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EDITORIAL
I would like to acknowledge and thank the Associate
Editors for their outstanding contribution during 2009:
Kishor Gulabivala, Matt German, Jeremy Hayes,
Michael Hulsmann, Yuan-Ling Ng, Ove Peters,
Min-Kai Wu, Matthias Zehnder.
I would also like to acknowledge and thank the
following referees for their critical appraisal of papers
received:
Paul Abbott, Guido Aesaert, Michael Ahlquist, Anas
Al-jadaa, Antonio Apicella, Saeed Asgary, Paul Ashley,
Phil Atkin, Graham Bailey, Rafael Yague Ballester,
Michael Baumann, Michael Behr, Sema Belli, Lars
Bergmans, Matthias Bickel, Lars Bjørndal, Gilles Blu-
teau, Emre Bodrumlu, Patrick Bogaerts, George Bogen,
Fiona Boissonade, Peter Bolhuis, Tatiana Botero, Serge
Bouillaguet, Martha Brackett, Peter Briggs, Paul Brun-
ton, Josette Camilleri, Jean Camps, Dermot Canavan,
Peter Carrotte, Bruno Cavalcanti, Nick Chandler, Gary
Cheung, Bun San Chong, David Cohen, Ben Cole, Georg
Conrads, Ian Corbett, Margaret Corson, Bill Costerton,
Elisabetta Cotti, Francesco D’Aiuto, Till Dammaschke,
Camillo D’Arcangelo, Peter Day, Mieke De Bruyne,
Roeland De Moor, Carlos de Souza Costa, Gustavo
De-Deus, Chris Deery, Anibal Diogenes, Nick Donos,
Nicholas Drage, Peter Duckmanton, Johannes Ebert,
Martin Ehrbar, Ashraf ElAyouti, Paul Eleazer, George
Eliades, Chris Emery, Unni Endal, Carlos Estrela, Marco
Ferrari, Jose Figueiredo, Ashraf Fouad, Richard Foxton,
Roland Frankenberger, Inge Fristad, Massimo Gagliani,
Gianluca Gambarini, Jennifer Gibbs, Alan Gluskin,
Michel Goldberg, Brenda Gomes, Harold Goodis,
Simone Grandini, Rene Gruythuysen, James Gutmann,
Markus Haapasalo, Gunnar Hasselgren, Sivakami
Haug, Jianing He, Brian Henderson, Michael Hofmann,
Christopher Hope, Keith Horner, Preben Horsted-
Bindslev, Tony Hoskinson, George Huang, Bart
Huybrechts, Richard Kahan, Asma Khan, Andrej
Kielbassa, Eun-Cheol Kim, Lise-Lotte Kirkevang, Anil
Kishen, Elisabeth Koulaouzidou, Thomas Kvist, Paul
Lambrechts, Rachel Leeson, Jim Lewsey, Ludwig
Limbach, Shaul Lin, Christina Lindh, Howard Lloyd,
Matthew Locke, Claus Lost, Robert Love, Hans Ulrich
Luder, Phil Lumley, Pierre Machtou, Iain Mackie,
Francesco Mannocci, Monika Marending, Phil Marsh,
Paul McCabe, John McCabe, Robert McConnell, Harold
Messer, Thimios Mitsiadis, Dirk Mohn, Anders Moland-
er, Francesca Monticelli, Nicky Mordan, Peter Murray,
Akhila Muthukrishnan, P.N.R. Nair, Mohammad
Nekoofar, Jacques Nor, Takashi Okiji, Dag Ørstavik,
Ahmet Ozok, Cornelis Pameijer, Frank Paque, Peter
Parashos, Shanon Patel, Jorge Perdigao, Hiran Perin-
panayagam, Christine Peters, Linda Peters, Kerstin
Petersson, David Pitt, Heather Pitt Ford, Gianluca
Plotino, Carlo Prati, Jonathan Pratten, Alison Qualt-
rough, Ivana Radovic, Derren Ready, John Regan,
Kathrin Reichenmiller, Claes Reit, John Rhodes, Adam
Roberts, Sarah Rolland, Martin Rosentritt, Vivian
Rushton, Kamran Safavi, Chankhrit Sathorn, Julian
Satterthwaite, Bill Saunders, Edgar Schafer, Jorg
Schirrmeister, Patrick Schmidlin, Helmut Schweikl,
Geoffrey Seccombe, Christine Sedgley, Bilge Sen, Ann
Shearer, Hagay Shemesh, Sharan Sidhu, Asgeir Sig-
urdsson, Nick Silikas, Ulf Sjogren, Alastair Sloan, Carlos
Soares, David Sonntag, Manoel Sousa-Neto, Erick
Souza, Valerie Sparkes, Dave Spratt, Vidya Srinivasan,
Hideaki Suda, Pia Titterud Sunde, Mario Tanomaru-
Filho, Franklin R Tay, Peter Taylor, Fabricio Teixeira,
Leo Tjaderhane, Mirek Tolar, Muhittin Toman, Phillip
Tomson, Mahmoud Torabinejad, Dimitrios Tziafas,
lucas van der Sluis, Peter Velvart, Frank Vertucci,
Morgana Vianna, Thomas von Arx, William Walker,
Angus Walls, Damien Walmsley, Tuomas Waltimo,
Rick Walton, John Wataha, Paula Waterhouse, Roland
Weiger, Richard Welbury, Paul Wesselink, John Whit-
worth, David Witherspoon, Karl Thomas Wrbas, Peter
Yaman.
Without their commitment, dedication and expertise,
the International Endodontic Journal could not maintain
its position as the leading publication in the field of
Endodontology.
Paul M. H. Dummer
Editor-in-Chief
doi:10.1111/j.1365-2591.2009.01656.x
1ª 2010 International Endodontic Journal International Endodontic Journal, 43, 1, 2010
REVIEW
The smear layer in endodontics – a review
D. R. Violich1 & N. P. Chandler2
1Private Endodontic Practice, Tauranga, New Zealand; and 2Sir John Walsh Research Institute, School of Dentistry, University of
Otago, Dunedin, New Zealand
Abstract
Violich DR, Chandler NP. The smear layer in endodontics –
a review. International Endodontic Journal, 43, 2–15, 2010.
Root canal instrumentation produces a layer of organic
and inorganic material called the smear layer that may
also contain bacteria and their by-products. It can
prevent the penetration of intracanal medicaments into
dentinal tubules and influence the adaptation of filling
materials to canal walls. This article provides an
overview of the smear layer, focusing on its relevance
to endodontics. The PubMed database was used
initially; the reference list for smear layer featured
1277 articles, and for both smear layer dentine and
smear layer root canal revealed 1455 publications.
Smear layer endodontics disclosed 408 papers. A
forward search was undertaken on selected articles
and using some author names. Potentially relevant
material was also sought in contemporary endodontic
texts, whilst older books revealed historic information
and primary research not found electronically, such
that this paper does not represent a ‘classical’ review.
Data obtained suggests that smear layer removal
should enhance canal disinfection. Current methods
of smear removal include chemical, ultrasonic and
laser techniques – none of which are totally effective
throughout the length of all canals or are universally
accepted. If smear is to be removed, the method of
choice seems to be the alternate use of ethylenedi-
aminetetraacetic acid and sodium hypochlorite solu-
tions. Conflict remains regarding the removal of the
smear layer before filling root canals, with investiga-
tions required to determine the role of the smear layer
in the outcomes of root canal treatment.
Keywords: dentine, ethylenediaminetetraacetic acid,
endodontic treatment, smear layer.
Received 20 June 2007; accepted 21 July 2009
Introduction
Whenever dentine is cut using hand or rotary
instruments, the mineralized tissues are not shredded
or cleaved but shattered to produce considerable
quantities of debris. Much of this, made up of very
small particles of mineralized collagen matrix, is
spread over the surface to form what is called the
smear layer. Identification of the smear layer was
made possible using the electron microprobe with
scanning electron microscope (SEM) attachment, and
first reported by Eick et al. (1970). These workers
showed that the smear layer was made of particles
ranging in size from less than 0.5–15 lm. Scanning
electron microscope studies of cavity preparations by
Brannstrom & Johnson (1974) demonstrated a thin
layer of grinding debris. They estimated it to be
2–5 lm thick, extending a few micrometres into the
dentinal tubules.
The smear layer in a cavity and in the root canal
may not be directly comparable. Not only are the tools
for dentine preparation different in coronal cavities, but
in the root canal the dentinal tubule numbers show
greater variation and there are likely to be more soft
tissue remnants present. The first researchers to
describe the smear layer on the surface of instrumented
root canals were McComb & Smith (1975). They
Correspondence: Nicholas Chandler, Associate Professor,
School of Dentistry, University of Otago, P.O. Box 647,
Dunedin 9054, New Zealand (Tel.: 0064 3 479 7124; fax:
0064 3 479 5079; e-mail [email protected]).
doi:10.1111/j.1365-2591.2009.01627.x
International Endodontic Journal, 43, 2–15, 2010 ª 2010 International Endodontic Journal2
http://endodontic.ws
suggested that the smear layer consisted not only of
dentine as in the coronal smear layer, but also the
remnants of odontoblastic processes, pulp tissue and
bacteria. Lester & Boyde (1977) described the smear
layer as ‘organic matter trapped within translocated
inorganic dentine’. As it was not removed by sodium
hypochlorite irrigation, they concluded that it was
primarily composed of inorganic dentine. Goldman
et al. (1981) estimated the smear thickness at 1 lm
and agreed with previous investigators that it was
largely inorganic in composition. They noted its pres-
ence along instrumented canal surfaces. Mader et al.
(1984) reported that the smear layer thickness was
generally 1–2 lm. Cameron (1983) and Mader et al.
(1984) discussed the smear material in two parts: first,
superficial smear layer (Fig. 1) and second, the material
packed into the dentinal tubules. Packing of smear
debris was present in the tubules to a depth of 40 lm.
Brannstrom & Johnson (1974) and Mader et al. (1984)
concluded that the tubular packing phenomenon was
due to the action of burs and instruments. Components
of the smear layer can be forced into the dentinal
tubules to varying distances (Moodnik et al. 1976,
Brannstrom et al. 1980, Cengiz et al. 1990) to form
smear plugs (Fig. 2). However, Cengiz et al. (1990)
proposed that the penetration of smear material into
dentinal tubules could also be caused by capillary
action as a result of adhesive forces between the
dentinal tubules and the material. This hypothesis of
capillary action may explain the packing phenomenon
observed by Aktener et al. (1989), who showed that the
penetration could increase up to 110 lm when using
surface-active reagents in the canal during endodontic
instrumentation. The thickness may also depend on the
type and sharpness of the cutting instruments and
whether the dentine is dry or wet when cut (Barnes
1974, Gilboe et al. 1980, Cameron 1988). In the early
stages of instrumentation, the smear layer on the walls
of canals can have a relatively high organic content
because of necrotic and/or viable pulp tissue in the root
canal (Cameron 1988). Increased centrifugal forces
resulting from the movement and the proximity of the
instrument to the dentine wall formed a thicker layer
which was more resistant to removal with chelating
agents (Jodaikin & Austin 1981). The amount pro-
duced during motorized preparation, as with Gates-
Glidden or post drills, has been reported as greater in
volume than that produced by hand filing (Czonstkow-
sky et al. 1990). However, McComb & Smith (1975)
observed under SEM that instrumentation with
K-reamers, K-files and Giromatic reciprocating files
created similar surfaces. Additional work has shown
that the smear layer contains organic and inorganic
substances that include fragments of odontoblastic
processes, microorganisms and necrotic materials
(Pashley 1992). The generation of a smear layer is
almost inevitable during root canal instrumentation.
Whilst a noninstrumentation technique has been
described for canal preparation without smear forma-
tion, efforts rather focus on methods for its removal,
such as chemical means and methods such as ultra-
sound and hydrodynamic disinfection for its disruption.
Root canal preparation without the creation of a smear
Figure 1 Scanning electron micrograph of smeared surface of
dentine. The crack shapes are processing artefacts overlying
dentinal tubules.
Figure 2 Scanning electron micrograph of dentine surface
showing smear plugs occluding tubules. The surface has been
treated for 60 s with Tubulicid Blue Label (Dental Therapeu-
tics AB, Nacka, Sweden).
3
Violich & Chandler Smear layer in endodontics
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 2–15, 2010
layer may be possible. A noninstrumental hydrody-
namic technique may have future potential (Lussi et al.
1993), and sonically driven polymer instruments with
tips of variable diameter are reported to disrupt the
smear layer in a technique called hydrodynamic
disinfection (Ruddle 2007).
When viewed under the SEM, the smear layer often
has an amorphous irregular and granular appearance
(Brannstrom et al. 1980, Yamada et al. 1983, Pashley
et al. 1988) (Fig. 3). The appearance is thought to be
formed by translocating and burnishing the superficial
components of the dentine walls during treatment
(Baumgartner & Mader 1987).
The significance of the smear layer
Root canal treatment usually involves the chemome-
chanical removal of bacteria and infected dentine from
within the root canals. The process is often followed by
an intracanal dressing and a root filling. Amongst
important factors affecting the prognosis of root canal
treatment is the seal created by the filling against the
walls of the canal. Considerable effort has been made to
understand the effect of the smear layer on the apical
and coronal seal (Madison & Krell 1984, Goldberg et al.
1985, 1995, Evans & Simon 1986, Kennedy et al.
1986, Cergneux et al. 1987, Saunders & Saunders
1992, 1994, Gencoglu et al. 1993a, Karagoz-Kucukay
& Bayirli 1994, Tidswell et al. 1994, Lloyd et al. 1995,
Behrend et al. 1996, Chailertvanitkul et al. 1996,
Vassiliadis et al. 1996, Taylor et al. 1997, Timpawat
& Sripanaratanakul 1998, Economides et al. 1999,
2004, von Fraunhofer et al. 2000, Froes et al. 2000,
Goya et al. 2000, Timpawat et al. 2001, Clark-Holke
et al. 2003, Cobankara et al. 2004, Park et al. 2004).
Workers have reached different conclusions, with
current knowledge of interactions between the smear
layer and factors such as filling technique and sealer
type being limited. In addition, the methodology of
studies, the type and site of leakage tests, and the
sample size should be taken into account and consid-
eration given to these variables before conclusions are
reached (Shahravan et al. 2007).
Some authors suggest that maintaining the smear
layer may block the dentinal tubules and limit bacterial
or toxin penetration by altering dentinal permeability
(Michelich et al. 1980, Pashley et al. 1981, Safavi et al.
1990). Others believe that the smear layer, being a
loosely adherent structure, should be completely
removed from the surface of the root canal wall
because it can harbour bacteria and provide an avenue
for leakage (Mader et al. 1984, Cameron 1987a,
Meryon & Brook 1990). It may also limit the effective
disinfection of dentinal tubules by preventing sodium
hypochlorite, calcium hydroxide and other intracanal
medicaments from penetrating the dentinal tubules.
Should the smear layer be removed?
The question of keeping or removing the smear layer
remains controversial (Drake et al. 1994, Shahravan
et al. 2007). Some investigations have focussed on its
removal (Garberoglio & Brannstrom 1976, Outhwaite
et al. 1976, Pashley 1985), whilst others have consid-
ered its effects on apical and coronal microleakage
(Madison & Krell 1984, Goldberg et al. 1995, Cha-
ilertvanitkul et al. 1996), bacterial penetration of the
tubules (Pashley 1984, Williams & Goldman 1985,
Meryon & Brook 1990) and the adaptation of root
canal materials (White et al. 1987, Gencoglu et al.
1993a, Gutmann 1993). In support of its removal are:
1. It has an unpredictable thickness and volume,
because a great portion of it consists of water (Cerg-
neux et al. 1987).
2. It contains bacteria, their by-products and necrotic
tissue (McComb & Smith 1975, Goldberg & Abramo-
vich 1977, Wayman et al. 1979, Cunningham &
Martin 1982, Yamada et al. 1983). Bacteria may
survive and multiply (Brannstrom & Nyborg 1973)
and can proliferate into the dentinal tubules (Olgart
et al. 1974, Akpata & Blechman 1982, Williams &
Figure 3 Scanning electron micrograph of dentine surface
with typical amorphous smear layer with granular appear-
ance and moderate debris present (courtesy of Dr Artika
Soma).
4
Smear layer in endodontics Violich & Chandler
International Endodontic Journal, 43, 2–15, 2010 ª 2010 International Endodontic Journal
http://endodontic.ws
Goldman 1985, Meryon et al. 1986, Meryon & Brook
1990), which may serve as a reservoir of microbial
irritants (Pashley 1984).
3. It may act as a substrate for bacteria, allowing their
deeper penetration in the dentinal tubules (George et al.
2005).
4. It may limit the optimum penetration of disinfecting
agents (McComb & Smith 1975, Outhwaite et al. 1976,
Goldberg & Abramovich 1977, Wayman et al. 1979,
Yamada et al. 1983). Bacteria may be found deep
within dentinal tubules (Bystrom & Sundqvist 1981,
1983, 1985) and smear layer may block the effects of
disinfectants in them (Goldberg & Abramovich 1977,
Wayman et al. 1979, Yamada et al. 1983, Baumgart-
ner & Mader 1987). Haapasalo & Ørstavik (1987)
found that in the absence of smear layer, liquid
camphorated monochlorophenol disinfected the den-
tinal tubules rapidly and completely, but calcium
hydroxide failed to eliminate Enterococcus faecalis even
after 7 days of incubation. A subsequent study con-
cluded that the smear layer delayed but did not abolish
the action of the disinfectant (Ørstavik & Haapasalo
1990). Brannstrom (1984) had previously stated that
following the removal of the smear layer, bacteria in
the dentinal tubules can easily be destroyed.
5. It can act as a barrier between filling materials and
the canal wall and therefore compromise the formation
of a satisfactory seal (Lester & Boyde 1977, White et al.
1984, Cergneux et al. 1987, Czonstkowsky et al. 1990,
Foster et al. 1993, Yang & Bae 2002). Lester & Boyde
(1977) found that zinc oxide – eugenol based root
canal sealers failed to enter dentinal tubules in the
presence of smear. In two consecutive studies, White
et al. observed that plastic filling materials and sealers
penetrated dentinal tubules after removal of smear
layer (White et al. 1984, 1987). Oksan et al. (1993)
also found that smear prevented the penetration of
sealers into dentinal tubules, whilst no penetration of
sealer was observed in control groups. Penetration in
their smear-free groups ranged from 40 to 60 lm. It
may be concluded that such tubular penetration
increases the interface between the filling and the
dentinal structures, which may improve the ability of a
filling material to prevent leakage (White et al. 1984).
If the aim is maximum penetration into the dentinal
tubules to prevent microleakage, root canal filling
materials should be applied to a surface free of smear
and either a low surface activity or, alternatively, an
adequate surface-active reagent must be added to them
(Aktener et al. 1989). However, there are no reports of
a correlation between microleakage and penetration of
filling materials into dentinal tubules, whilst the basis
of leakage studies remains questionable. Pashley et al.
(1989) observed an extensive network of microchan-
nels around restorations that had been placed in
cavities with smear layer. The thickness of these
channels was 1–10 lm. Smear layer may thus present
a passage for substances to leak around or through its
particles at the interface between the filling material
and the tooth structure. Pashley & Depew (1986)
reported that, when experimenting with class 1 cavi-
ties, microleakage decreased after the removal of smear
layer, but dentinal permeability increased. Saunders &
Saunders (1992) concluded that coronal leakage of
root canal fillings was less in smear-free groups than
those with a smear layer.
6. It is a loosely adherent structure and a potential
avenue for leakage and bacterial contaminant passage
between the root canal filling and the dentinal walls
(Mader et al. 1984, Cameron 1987b, Meryon & Brook
1990). Its removal would facilitate canal filling
(McComb & Smith 1975, Goldman et al. 1981, Cam-
eron 1983).
Conversely, some investigators believe in retaining
the smear layer during canal preparation, because it
can block the dentinal tubules, preventing the ex-
change of bacteria and other irritants by altering
permeability (Michelich et al. 1980, Pashley et al.
1981, Safavi et al. 1990, Drake et al. 1994, Galvan
et al. 1994). The smear layer serves as a barrier to
prevent bacterial migration into the dentinal tubules
(Drake et al. 1994, Galvan et al. 1994, Love et al.
1996, Perez et al. 1996). Pashley (1985) suggested
that if the canals were inadequately disinfected, or if
bacterial contamination occurred after canal prepara-
tion, the presence of a smear layer might stop bacterial
invasion of the dentinal tubules. Bacteria remaining
after canal preparation are sealed into the tubules by
the smear layer and subsequent filling materials. Some
studies provide evidence to support the hypothesis that
the smear layer inhibits bacterial penetration (Pashley
et al. 1981, Safavi et al. 1989). A major limitation is
that the experiments were undertaken with dentine
discs or root cross-sections, models with little relevance
in terms of simulating the clinical conditions of root
canal treatment. Drake et al. (1994) developed a more
clinically relevant model to determine the effect of the
presence or absence of the smear layer on bacterial
colonization of root canals.
Williams & Goldman (1985) reported that the smear
layer was not a complete barrier and could only delay
bacterial penetration. In their experiment, using the
5
Violich & Chandler Smear layer in endodontics
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 2–15, 2010
motile, swarming bacterium Proteus vulgaris, the smear
layer delayed the passage of the organisms through the
tubules. Madison & Krell (1984) using ethylenedi-
aminetetraacetic acid (EDTA) solution in a dye pene-
tration study found that the smear layer made no
difference to leakage. Goldberg et al. (1995) studied the
sealing ability of Ketac Endo and Tubliseal in an India
ink study with and without smear layer and found no
difference. Chailertvanitkul et al. (1996) found no
difference in leakage with or without smear layer,
however the time period was short. When the smear
layer is not removed, the durability of the apical seal
should be evaluated over a long period. Since the smear
layer is nonhomogenous and may potentially be
dislodged from the underlying tubules (Mader et al.
1984), it may slowly disintegrate, dissolving around a
leaking filling material to leave a void between the
canal wall and sealer. Meryon & Brook (1990) found
the presence of smear layer had no effect on the ability
of three oral bacteria to penetrate dentine discs. All
were able to digest the layer, possibly stimulated by the
nutrient-rich medium below the discs.
The adaptation of root canal materials to canal walls
has been studied. White et al. (1987) found that
pHEMA, silicone and Roth 801 and AH26 sealers
extended into tubules consistently when smear layer
was removed. Gencoglu et al. (1993b) found removing
the smear layer enhanced the adaptation of gutta-
percha in both cold laterally compacted and thermo-
plastic root fillings without sealer. Gutmann (1993)
also showed that after removing the smear layer,
themoplastic gutta-percha adapted with or without
sealer.
A systematic review and meta-analysis by Shahra-
van et al. (2007) set out to determine whether smear
layer removal reduced leakage of root filled teeth ex
vivo. Using 26 eligible papers with 65 comparisons,
54% of the comparisons reported no significant differ-
ence, 41% reported in favour of removing the smear
layer and 5% reported a difference in favour of keeping
it. They concluded that smear layer removal improved
the fluid-tight seal of the root canal system, whereas
other factors such as filling technique or the type of
sealer did not produce significant effects.
Urethane dimethacrylate (UDMA) based root canal
sealers have been introduced. Their aim is to provide a
better bond to allow less microleakage and increase the
fracture resistance of root filled teeth through the
creation of monoblocks, when a core material such as
Resilon replaces gutta-percha. Whilst some studies
indicate that smear layer removal leads to higher
tubule penetration, increased sealer to dentine bond
strength and enhanced fluid-tight seal, a recent report
concluded that smear layer removal did not necessarily
equate to improved resistance to bacterial penetration
along these and older types of sealers (Saleh et al.
2008).
Methods to remove the smear layer
Chemical removal
The quantity of smear layer removed by a material is
related to its pH and the time of exposure (Morgan &
Baumgartner 1997). A number of chemicals have
been investigated as irrigants to remove the smear
layer. According to Kaufman & Greenberg (1986), a
working solution is the one which is used to clean the
canal, and an irrigation solution the one which is
essential to remove the debris and smear layer created
by the instrumentation process. Chlorhexidine, whilst
popular as an irrigant and having a long lasting
antibacterial effect through adherence to dentine, does
not dissolve organic material or remove the smear
layer.
Sodium hypochlorite
The ability of NaOCl to dissolve organic tissues is well-
known (Rubin et al. 1979, Wayman et al. 1979,
Goldman et al. 1982) and increases with rising tem-
perature (Moorer & Wesselink 1982). However, its
capacity to remove smear layer from the instrumented
root canal walls has been found to be lacking. The
conclusion reached by many authors is that the use of
NaOCl during or after instrumentation produces super-
ficially clean canal walls with the smear layer present
(Baker et al. 1975, Goldman et al. 1981, Berg et al.
1986, Baumgartner & Mader 1987).
Chelating agents
Smear layer components include very small particles
with a large surface : mass ratio, which makes them
soluble in acids (Pashley 1992). The most common
chelating solutions are based on EDTA which reacts
with the calcium ions in dentine and forms soluble
calcium chelates (Fig. 4). It has been reported that
EDTA decalcified dentine to a depth of 20–30 lm in
5 min (von der Fehr & Nygaard-Ostby 1963); however,
Fraser (1974) stated that the chelating effect was
almost negligible in the apical third of root canals.
6
Smear layer in endodontics Violich & Chandler
International Endodontic Journal, 43, 2–15, 2010 ª 2010 International Endodontic Journal
Different formulations of EDTA have been used as
root canal irrigants. In a combination, urea peroxide is
added to encourage debris to float out of the root canal
(Stewart et al. 1969). This product (RC-Prep, Premier
Dental Products, Plymouth Meeting, PA, USA) also
includes a wax that left a residue on the root canal
walls despite further instrumentation and irrigation
and which may compromise the ability to obtain a
hermetic seal (Biesterfeld & Taintor 1980). Many
studies have shown that paste-type chelating agents,
whilst having a lubricating effect, do not remove the
smear layer effectively when compared to liquid EDTA.
A recent experiment examining the addition of two
surfactants to liquid EDTA did not result in better smear
layer removal (Lui et al. 2007).
A quaternary ammonium bromide (cetrimide) has
been added to EDTA solutions to reduce surface tension
and increase penetrability of the solution (von der Fehr
& Nygaard-Ostby 1963). McComb & Smith (1975)
reported that when this combination (REDTA) was
used during instrumentation, there was no smear layer
remaining except in the apical part of the canal. After
using REDTA in vivo, it was shown that the root canal
surfaces were uniformly occupied by patent dentinal
tubules with very little superficial debris (McComb et al.
1976). When used during and after instrumentation, it
was possible to still see remnants of odontoblastic
processes within the tubules even though there was no
smear layer present (Goldman et al. 1981). Goldberg &
Abramovich (1977) observed that the circumpulpal
surface had a smooth structure and that the dentinal
tubules had a regular circular appearance with the use
of EDTAC (EDTA and cetavlon). The optimal working
time of EDTAC was suggested to be 15 min in the root
canal and no further chelating action could be expected
after this (Goldberg & Spielberg 1982). This study also
showed that REDTA was the most efficient irrigating
solution for removing smear layer. In a study using a
combination of 0.2% EDTA and a surface-active
antibacterial solution, Brannstrom et al. (1980) ob-
served that this mixture removed most of the smear
layer without opening many dentinal tubules or
removing peritubular dentine. Bis-dequalinium-acetate
(BDA), a dequalinium compound and an oxine deriv-
ative has been shown to remove the smear layer
throughout the canal, even in the apical third (Kauf-
man et al. 1978, Kaufman 1981). BDA is well tolerated
by periodontal tissues and has a low surface tension
allowing good penetration. It is considered less toxic
that NaOCl and can be used as a root canal dressing. A
commercial form of BDA called Solvidont (De Trey,
A.G., Zurich, Switzerland) was available in the 1980s
and its use as an alternative to NaOCl was supported
experimentally (Kaufman 1983a,b, Chandler & Lilley
1987, Lilley et al. 1988, Mohd Sulong 1989). Salvizol
(Ravens Gmbh, Konstanz, Germany) is a commercial
brand of 0.5% BDA and possesses the combined actions
of chelation and organic debridement. Kaufman et al.
(1978) reported that Salvizol had better cleaning
properties than EDTAC. When comparing Salvizol with
5.25% NaOCl, both were found comparable in their
ability to remove organic debris, but only Salvizol
opened dentinal tubules (Kaufman & Greenberg 1986).
Berg et al. (1986) found that Salvizol was less effective
at opening dentinal tubules than REDTA.
Calt & Serper (2000) compared the effects of ethylene
glycol-bis (ß-aminoethyl ether)-N,N,N¢, N¢-tetraacetic
acid (EGTA) with EDTA. The smear layer was com-
pletely removed by EDTA, but it caused erosion of the
peritubular and intertubular dentine, whilst EGTA was
not as effective in the apical third of root canals. EGTA
is reported to bind calcium more specifically (Schmid &
Reilley 1957).
Tetracylines (including tetracycline hydrochloride,
minocycline and doxycycline) are antibiotics effective
against a wide range of microorganisms. Tetracyclines
have unique properties in addition to their antimicro-
bial aspect. They have low pH in concentrated solution,
and because of this can act as a calcium chelator and
cause enamel and root surface demineralization (Bjor-
vatn 1982). The surface demineralization of dentine is
comparable with that of citric acid (Wikesjo et al.
1986). Barkhordar et al. (1997) reported that doxycy-
Figure 4 Scanning electron micrograph of dentine following
60 s exposure to 18% ethylenediaminetetraacetic acid solu-
tion (Ultradent Products Inc., South Jordan, UT, USA).
7
Violich & Chandler Smear layer in endodontics
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 2–15, 2010
cline hydrochloride (100 mg mL-1) was effective in
removing the smear layer from the surface of instru-
mented canals and root-end cavity preparations. They
speculated that a reservoir of active antibacterial agents
might remain, because doxycycline readily attaches to
dentine and can be subsequently released (Baker et al.
1983, Wikesjo et al. 1986). Haznedaroglu & Ersev
(2001) showed that 1% tetracycline hydrochloride or
50% citric acid can be used to remove the smear layer
from surfaces of root canals. Although they reported no
difference between the two groups, it appeared that the
tetracycline demineralized less peritubular dentine than
the citric acid.
In an effort to produce an irrigant capable of both
removing the smear layer and disinfecting the root
canal system, Torabinejad et al. (2003) developed a
new irrigating solution containing a mixture of a
tetracycline isomer, an acid, and a detergent (MTAD).
Their work concluded MTAD to be an effective solution
for the removal of the smear layer. It does not
significantly change the structure of the dentinal
tubules when the canals are irrigated with sodium
hypochlorite and followed with a final rinse of MTAD.
This irrigant demineralizes dentine faster than 17%
EDTA (De-Deus et al. 2007) and bacterial penetration
into filled canals is similar with both solutions (Ghod-
dusi et al. 2007).
Organic acids
The effectiveness of citric acid as a root canal irrigant
has been demonstrated (Loel 1975, Tidmarsh 1978)
and confirmed to be more effective than NaOCl alone in
removing the smear layer (Baumgartner et al. 1984).
Citric acid removed smear layer better than polyacrylic
acid, lactic acid and phosphoric acid but not EDTA
(Meryon et al. 1987). Wayman et al. (1979) showed
that canal walls treated with 10%, 25% and 50% citric
acid solution were generally free of the smeared
appearance, but they had the best results in removing
smear layer with sequential use of 10% citric acid
solution and 2.5% NaOCl solution, then again followed
by a 10% solution of citric acid. However, Yamada
et al. (1983) observed that the 25% citric acid–NaOCl
group was not as effective as a 17% EDTA–NaOCl
combination. To its detriment, citric acid left precipi-
tated crystals in the root canal which might be
disadvantageous to the root canal filling. With 50%
lactic acid, the canal walls were generally clean, but
with openings of dentinal tubules that did not appear to
be completely patent (Wayman et al. 1979). Bitter
(1989) introduced 25% tannic acid solution as a root
canal irrigant and cleanser. Canal walls irrigated with
this solution appeared significantly cleaner and
smoother than walls treated with a combination of
hydrogen peroxide and NaOCl, and the smear layer was
removed. Sabbak & Hassanin (1998) refuted these
findings and explained that tannic acid increased the
cross-linking of exposed collagen with the smear layer
and within the matrix of the underlying dentine,
therefore increasing organic cohesion to the tubules.
McComb & Smith (1975) compared the efficacy of
20% polyacrylic acid with REDTA and found that it
was no better than REDTA in removing or preventing
the build up of smear layer, thought to be as a result of
its higher viscosity. McComb et al. (1976) also used 5%
and 10% polyacrylic acid as an irrigant and observed
that it could remove smear layer in accessible regions.
Polyacrylic acid (Durelon liquid and Fuji II liquid) at
40% has been reported to be very effective, and because
of its potency users should not exceed a 30 s applica-
tion (Berry et al. 1987).
Sodium hypochlorite and EDTA
When irrigating a root canal the purpose is twofold: to
remove the organic component, the debris originating
from pulp tissue and microorganisms, and the mostly
inorganic component, the smear layer. As there is no
single solution which has the ability to dissolve organic
tissues and to demineralize the smear layer, the
sequential use of organic and inorganic solvents has
been recommended (Koskinen et al. 1980, Yamada
et al. 1983, Baumgartner et al. 1984). Numerous
authors have agreed that the removal of smear layer
as well as soft tissue and debris can be achieved by the
alternate use of EDTA and NaOCl (Yamada et al. 1983,
White et al. 1984, Baumgartner & Mader 1987, Cengiz
et al. 1990). Goldman et al. (1982) examined the effect
of various combinations of EDTA and NaOCl, and the
most effective final rinse was 10 mL of 17% EDTA
followed by 10 mL of 5.25% NaOCl, a finding con-
firmed by Yamada et al. (1983). Used in combination
with EDTA, NaOCl is inactivated with the EDTA
remaining functional for several minutes.
Ultrasonic smear removal
Following the introduction of dental ultrasonic devices
in the 1950s, ultrasound was investigated in end-
odontics (Martin et al. 1980, Cunningham & Martin
1982, Cunningham et al. 1982). A continuous flow of
8
Smear layer in endodontics Violich & Chandler
International Endodontic Journal, 43, 2–15, 2010 ª 2010 International Endodontic Journal
NaOCl activated by an ultrasonic delivery system was
used for the preparation and irrigation of canals.
Smear-free canal surfaces were observed using this
method (Cameron 1983, 1987a,b, Griffiths & Stock
1986, Alacam 1987). Whilst concentrations of 2–4%
sodium hypochlorite in combination with ultrasonic
energy were able to remove smear layer, lower
concentrations of the solutions were unsatisfactory
(Cameron 1988). However, Ahmad et al. (1987a)
claimed that their technique of modified ultrasonic
instrumentation using 1% NaOCl removed the debris
and smear layer more effectively than the technique
recommended by Martin & Cunningham (1983). The
apical region of the canals showed less debris and
smear layer than the coronal aspects, depending on
acoustic streaming, which was more intense in
magnitude and velocity at the apical regions of the
file. Cameron (1983) also compared the effect of
different ultrasonic irrigation periods on removing
smear layer and found that a 3- and 5-min irrigation
produced smear-free canal walls, whilst an 1-min
irrigation was ineffective. In contrast to these results,
other investigators found ultrasonic preparation un-
able to remove smear layer (Cymerman et al. 1983,
Baker et al. 1988, Goldberg et al. 1988).
Researchers who found the cleaning effects of
ultrasonics beneficial used the technique only for the
final irrigation of root canal after completion of hand
instrumentation (Ahmad et al. 1987a, Alacam 1987,
Cameron 1988). This is given the term passive ultra-
sonic irrigation and has been the subject of a recent
review (van der Sluis et al. 2007). Ahmad et al.
(1987a,b) claimed that direct physical contact of the
file with the canal walls throughout instrumentation
reduced acoustic streaming. Acoustic streaming is
maximized when the tips of the smaller instruments
vibrate freely in a solution. Lumley et al. (1992)
recommended that only size 15 files be used to
maximize microstreaming for the removal of debris.
Prati et al. (1994) also achieved smear layer removal
with ultrasonics. Walker & del Rio (1989, 1991)
showed no significant difference between tap water and
sodium hypochlorite when used with ultrasonics, but
they reported that neither solution was effective at any
level in the canal to remove the smear layer ultrason-
ically. Baumgartner & Cuenin (1992) also observed
that ultrasonically energized NaOCl, even at full
strength, did not remove the smear layer from root
canal walls. Guerisoli et al. (2002) evaluated the use of
ultrasonics to remove the smear layer and found it
necessary to use 15% EDTAC with either distilled water
or 1% sodium hypochlorite to achieve the desired
result.
Laser removal
Lasers can be used to vaporize tissues in the main
canal, remove the smear layer and eliminate residual
tissue in the apical portion of root canals (Takeda et al.
1998a,b, 1999). The effectiveness of lasers depends on
many factors, including the power level, the duration of
exposure, the absorption of light in the tissues, the
geometry of the root canal and the tip-to-target
distance (Dederich et al. 1984, Onal et al. 1993, Tewfik
et al. 1993, Moshonov et al. 1995).
Dederich et al. (1984) and Tewfik et al. (1993) used
variants of the neodymium–yttrium-aluminium-gar-
net (Ne:YAG) laser and reported a range of findings
from no change or disruption of the smear layer to
actual melting and recrystallization of the dentine.
This pattern of dentine disruption was observed in
other studies with various lasers, including the carbon
dioxide laser (Onal et al. 1993), the argon fluoride
excimer laser (Stabholz et al. 1993), and the argon
laser (Moshonov et al. 1995, Harashima et al. 1998).
Takeda et al. (1998a,b, 1999) using the erbium-
yttrium-aluminium-garnet (Er:YAG) laser, demon-
strated optimal removal of the smear layer without
melting, charring or recrystallization associated with
other laser types. Kimura et al. (2002) also demon-
strated the removal of the smear layer with an Er:YAG
laser. Although they showed removal of the smear
layer, photomicrographs showed destruction of peri-
tubular dentine. The main difficulty with laser
removal of the smear layer is access to the small
canal spaces with the relatively large probes that are
available.
Conclusion
Contemporary methods of root canal instrumentation
produce a layer of organic and inorganic material called
the smear layer that may also contain bacteria and their
by-products. This layer covers the instrumented walls
and may prevent the penetration of intracanal medica-
ments into the dentinal tubules and interfere with the
close adaptation of root filling materials to canal walls.
The data presented indicate removal of the smear layer
for more thorough disinfection of the root canal system
and better adaptation of materials to the canal walls.
There are, however, no clinical trials to demonstrate
this. Current methods of smear layer removal include
9
Violich & Chandler Smear layer in endodontics
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 2–15, 2010
chemical, ultrasonic and laser techniques – none of
which are totally effective throughout the length of all
canals or are used universally. However, if the smear
layer is to be removed the method of choice seems to be
the alternate use of EDTA and sodium hypochlorite
solutions. Whilst much is known about individual
irrigants, their use in combination and their interac-
tions (and in some cases precipitates) is less well
understood. Conflicting reports exist regarding the
removal of the smear layer before filling root canals.
As several new sealer and core materials have recently
been introduced, further investigations are required to
determine the role of the smear layer in the outcome of
treatment.
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Violich & Chandler Smear layer in endodontics
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 2–15, 2010 15
Comparison of working length determination withradiographs and two electronic apex locators
J. P. Vieyra1, J. Acosta2 & J. M. Mondaca2
1School of Dentistry, Universidad Autonoma de Baja California, Tijuana, Baja California, Mexico; and 2Private Practice in
Endodontics, 71OE San Ysidro Blvd., 1513 San Ysidro, California 92173, USA
Abstract
Vieyra JP, Acosta J, Mondaca JM. Comparison of working
length determination with radiographs and two electronic apex
locators. International Endodontic Journal, 43, 16–20, 2010.
Aim To evaluate the accuracy of the Root ZX and
Elements-Diagnostic electronic apex locators when
compared with radiographs for locating the canal
terminus or minor foramen.
Methodology The canal terminus of 482 canals
in 160 maxillary and mandibular teeth was located
in vivo with both locators and radiographically.
After extraction, the actual location of the minor
foramen was determined visually and with magnifica-
tion. A paired samples t-test, chi-square test and a
repeated measure anova at the 0.05 level of signifi-
cance were used to determine differences between the
groups.
Results The Root ZX located the minor foramen
correctly 68% of the time in anterior and premolar
teeth, and 58% of the time in molar teeth. The
Elements-Diagnostic located the minor foramen
correctly 58% of the time in anterior and premolar
teeth and 49% of the time in molar teeth. Radio-
graphs located the minor foramen correctly 20% of
the time in anterior and premolar teeth and 11% of
the time in molar teeth. There was no statistically
significant difference between the two locators, but
there was a significant difference between them and
radiographs. For all teeth, the measurements made by
the apex locators were within ±0.5 mm of the minor
foramen 100% of the time, whereas for the radio-
graphs, the measurements were within this range only
15% of the time. This difference was significant
(P = 0.05).
Conclusion Measuring the location of the minor
foramen using the two apex locators was more
accurate than radiographs and would reduce the risk
of instrumenting and filling beyond the apical foramen.
Keywords: apical constriction, electronic apex loca-
tor, elements-diagnostic, Root ZX, working length
determination.
Received 20 November 2008; accepted 8 July 2009
Introduction
Root canal preparation and filling should not extend
beyond the tooth root nor leave uninstrumented areas
inside the root canal. Anatomically, the apical con-
striction (AC), also called the minor apical diameter or
minor diameter (Kuttler 1955), is a logical location for
working length (WL), as it often coincides with the
narrowest diameter of the root canal (AAE 2003).
However, locating the AC clinically is problematic.
Dummer et al. (1984) concluded that it is impossible to
locate the minor foramen clinically with certainty
because of its position and topography. The cemento-
dentinal junction (CDJ) has also been suggested as the
location for WL, because it represents the transition
between pulpal and periodontal tissue (Grove 1931).
The location of the CDJ is widely accepted as being
0.50–0.75 mm coronal to the apical foramen (Ricucci
& Langeland 1998) but, as with the AC, the exact
location of the CDJ is impossible to identify clinically. In
general, the CDJ is considered to be co-located with the
minor foramen (Stein et al. 1990); however, this is not
always the case (Dummer et al. 1984).
Correspondence: Dr Jorge Paredes Vieyra, PMB#1513, 710E,
San Ysidro Blvd., Suite ‘‘A’’, San Ysidro, CA 92173, USA (Tel.:
+1 619 946 0459; fax: +1 664 687 2207; e-mail:
doi:10.1111/j.1365-2591.2009.01620.x
International Endodontic Journal, 43, 16–20, 2010 ª 2010 International Endodontic Journal16
Working length is defined as ‘the distance from a
coronal reference point to the point at which canal
preparation and filling should terminate’ (American
Association of Endodontists (AAE) 2003). Radiographic
determination of WL has limitations such as distortion,
shortening and elongation, interpretation variability
and lack of three-dimensional representation. Even
when a paralleling technique is used, elongation of
images has been found to be approximately 5% (Van de
Voorde & Bjondahl 1969).
A WL 1 mm short of the radiographic apex may
result in over or under instrumentation because of the
variability in distance between the terminus of the root
canal (minor foramen) and the radiographic apex
(Gutierrez & Aguayo 1995). Thus, this often used ‘rule’
is not predictable or reliable.
Custer (1918) was the first to determine WL
electronically. Suzuki (1942) investigated the electrical
resistance properties of oral tissues and developed the
first electronic apex locator (EAL). The device was
resistance-based and measured the resistance between
two electrodes to determine the location of an instru-
ment in the canal. Later devices were impedance-based
(Nekoofar et al. 2006) and used multiple frequencies.
More recently, resistance- and capacitance-based
devices emerged that measure resistance and capa-
citance, directly and independently.
The Root ZX (J. Morita Corp., Tokyo, Japan) uses the
‘ratio method’ to locate the minor foramen (Kobayashi
& Suda 1994) by the simultaneous measurement of
impedance using two frequencies. The Root ZX claims
to work in the presence of electrolytes and nonelec-
trolytes and requires no calibration (Kobayashi 1995).
The Elements-Diagnostic (Sybron Endo, Sybron Den-
tal, Orange, CA, USA) uses multiple frequencies, in an
attempt to eliminate the influence of canal conditions.
In addition to improving WL accuracy (Nekoofar
et al. 2006), EALs address concerns about radiation,
as they have the potential to reduce the number of
radiographs taken during root canal treatment
(Pagavino et al. 1998).
The purpose of this study was to evaluate in vivo the
accuracy and predictability of two EALs for determining
WL as compared with radiographs.
Materials and methods
One hundred and sixty teeth (482 canals) with fully
formed apices and without apical resorption were used
(Table 1). All teeth gave positive responses to hot and
cold tests and were extracted for periodontal or
prosthodontic reasons. Ethical approval for the study
and an informed consent to participate was signed by
the patients.
After local anaesthesia, rubber dam isolation and
access cavity preparation were performed, the canals
were flared coronally with size 1 and 2 Orifice Shapers
(Dentsply Tulsa Dental, Tulsa, OK, USA) using 3%
sodium hypochlorite (NaOCl) for irrigation. The final
rinse was aspirated, but no attempt was made to dry
the canals.
The AC of each tooth was located with two EALs and
radiographically.
The minor foramen was located with the Root ZX by
advancing a size15 stainless steel K-file in the canal,
until the locator indicated that the minor foramen had
been reached, according to the manufacturer’s instruc-
tions (J. Morita Corp. 2004). The LCD showed a
flashing bar between APEX and 1 and a flashing tooth.
The silicone stop on the file was positioned at the
reference point. The file was removed from the canal
and the length was measured to the nearest 0.01 mm
with a digital caliper. This was the insertion length.
The AC was located with the Elements-Diagnostic
EAL by advancing the same size 15 K-file in the canal,
until the locator indicated that the minor foramen had
been reached, as per the manufacturer’s instructions
(Sybron Endo 2003). The stop was positioned at the
reference point and the insertion length measured. The
sequence of testing alternated between the two loca-
tors.
The minor foramen was located radiographically by
advancing the size15 K-file, until its tip was 1.0 mm
from the radiographic apex (determined from a pre-
treatment parallel technique radiograph). A radiograph
was exposed and if the file tip was seen not to be
1.0 mm from the radiographic apex, the file was
repositioned and another radiograph taken to ensure
that it was. The distance from the stop to the tip was
the insertion length. The file was then re-inserted to
the insertion length (1 mm from the radiographic
Table 1 Distribution of 160 teeth (482 canals)
Tooth (n)
Number of canals
Maxillary Mandibular
Central incisor (10) 7 3
Lateral incisor (8) 6 2
Canine (5) 3 2
Premolar (17) 11 6
Molar (120) 225 217
Total (160) 252 230
Vieyra et al. Working length determination
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 16–20, 2010 17
apex) and cemented in place with Fuji II LC dual-cure
glass ionomer cement (GC Corp, Tokyo, Japan). The
file handle was sectioned with a high-speed bur and
the tooth was extracted without disturbing the file,
placed in 6% NaOCl for 15 min to clean the root
surface and stored in a 0.2% thymol solution. All of the
clinical procedures were conducted by the principal
investigator.
After the tooth was removed from the solution and
with the file still in place, the apical 5 mm of the root
was ground parallel to the long axis of the canal with a
fine diamond bur and abrasive discs. When the file
became visible, additional dentine was removed under
20 · magnification (OPMI Pico microscope; Carl Zeiss,
Munich, Germany) until the file tip, the canal terminus,
and the foramen were in focus. A digital photograph
was taken and stored in Adobe Photoshop 5.5 (Adobe
Systems Inc., San Jose, CA, USA) and the distance of
the file tip to the minor foramen was measured. This
distance was recorded as being: )1.0 mm from the
minor foramen; )0.5 mm from the minor foramen; at
the minor foramen; +0.5 mm from the minor foramen
or +1.0 mm from the minor foramen. A minus symbol
()) indicated a file short of the minor foramen; a plus
symbol (+) indicated it was long.
Once the actual length to the minor foramen was
measured visually, the distance from the minor fora-
men determined by the two EALs was also completed
()1.0 mm from the minor foramen; )0.5 mm from the
minor foramen, etc.), by comparing their insertion
lengths to the actual length (distance to the AC)
(Tables 2–4).
The measurements obtained by the two EALs and
radiographs relative to the actual location of the minor
foramen were compared using a paired samples t-test,
chi-square test and a repeated measure. anova evalu-
ation was conducted at the 0.05 level of significance.
Results
For anterior teeth, the Root ZX, Elements and radio-
graphs located the minor foramen 74%, 65% and 22%
of the time, respectively. For premolar teeth, the Root
ZX, Elements and radiographs located the minor
foramen 53%, 41% and 35% of the time, respectively.
For molar teeth, the Root ZX, Elements and radiographs
located the minor foramen 58%, 49% and 11% of the
time, respectively. There was no statistically significant
difference between the two EALs, but there was a
difference when the EALs and radiographs were com-
pared (Tables 2–4).
Table 2 Distance of file tip from minor foramen determined by
Root ZX, Elements and radiograph (anteriors)
Distance from minor
foramen (mm)
Root ZX Elements Radiograph
n = 23 (%) n = 23 (%) n = 23 (%)
)1.0 – – –
)0.5 – – –
MF 17 (73.9) 15 (65.2) 5 (21.7)
+0.5 6 (26.08) 8 (34.7) 10 (43.47)
+1.0 8 (34.78)
MF, minor foramen.
(+) and ()) values indicate file tip beyond (+) or short ()) of the
AC.
Table 3 Distance of file tip from minor foramen determined by
Root ZX, Elements and radiograph (premolars)
Distance from minor
foramen (mm)
Root ZX Elements Radiograph
n = 17 (%) n = 17 (%) n = 17 (%)
)1.0 – – –
)0.5 – – –
MF 9 (52.94) 7 (41.17) 6 (35.29)
+0.5 8 (47.05) 10 (58.82) 5 (29.41)
+1.0 6 (35.29)
MF, minor foramen.
(+) and ()) values indicate file tip beyond (+) or short ()) of the
AC.
Table 4 Distance of file tip from minor foramen determined by Root ZX, Elements and radiograph (molars)
Distance from minor foramen (mm)
Root ZX (n = 444) Elements (n = 423) Radiograph (n = 414)
Canal Canal Canal
MB ML D DB DL Pa MB ML D DB DL Pa MB ML D DB DL Pa
)1.0 – – – – – – – – – – – – – – – – – –
)0.5 2 3 – – – – 6 5 18 – – 8 1 – 2 – – 1
MF 65 61 58 19 19 38 66 59 54 18 19 2 11 8 12 6 5 5
+0.5 53 45 27 16 16 22 48 41 15 22 21 21 61 41 47 17 17 28
+1.0 – – – – – – – – – – – – 43 34 26 11 12 26
MF, minor foramen.
(+) and ()) values indicate file tip beyond (+) or short ()) of the AC.
Working length determination Vieyra et al.
International Endodontic Journal, 43, 16–20, 2010 ª 2010 International Endodontic Journal18
For anterior, premolar and molar teeth, none of the
measurements were 1.0 mm short of the minor fora-
men. For anterior and premolar teeth, none of the
measurements were 0.5 mm short of the minor fora-
men, but for molar teeth 1%, 8% and 1% of the
measurements using the Root ZX, Elements and radio-
graphs, respectively, were short.
For anterior teeth, the Root ZX, Elements and
radiographs were 0.5 mm long of the minor foramen
a 26%, 35% and 39% roots, respectively. For premolar
teeth, the Root ZX, Elements and radiographs were
0.5 mm long of the minor foramen 47%, 59% and 29%
roots, respectively, and for molar teeth it was 41%,
42% and 48%, respectively.
No EAL measurements were 1.0 mm long of the
minor foramen for anterior, premolar and molar teeth,
but for radiographs it was 35% for anterior teeth, 35%
for premolar teeth and 37% for molar teeth. There
was no statistically significant difference between the
two EALs, but there was a significant difference
(P = 0.05) when the EALs and radiographs were
compared.
Discussion
The use of electronic devices to determine WL
has gained in popularity. When using them, an
important consideration is being aware of the possi-
ble sources of error such as metallic restorations,
salivary contamination, dehydration, etc. However, as
shown in this and other studies, the accuracy of EALs is
superior to radiographs (Van de Voorde & Bjondahl
1969, Pratten & McDonald 1996, Venturi & Breschi
2007).
One of the reasons why a radiographically deter-
mined WL lacks accuracy is that it is based on the
radiographic apex rather than the canal terminus – the
minor foramen. WL is obtained with a radiograph by
positioning the tip of a file a certain distance (usually
1.0 mm) from the radiographic apex. However, WL
should be based on the location of the minor foramen
rather than the apex, because the foramen frequently is
not at the apex (Wrbas et al. 2007). In this study,
radiographs correctly located the minor foramen 15%
of the time, whereas for the Root ZX and Elements it
was 63% and 53% of the time, respectively. Both EALs
were within ±0.5 mm from the minor foramen 100%
of the time, whereas radiographs were within ±0.5 mm
of 63% of cases. An in vivo study by Shabahang et al.
(1996) reported that the Root ZX was within 0.5 mm
from the minor foramen 96% of the time, a value
similar to the present findings. In general, this study
also agrees with others (Usun et al. 2007, 2008) that
EALs are more accurate than radiographs and greatly
reduce the risk of instrumenting and filling short or
beyond the canal terminus.
As the minor foramen varies in location and anat-
omy (sharply defined, parallel, or missing) (Nekoofar
et al. 2006), caution should be used to avoid over-
estimating WL. According to Gutierrez & Aguayo
(1995), over-instrumentation of the root canal must
be a common and unnoticed occurrence. An instru-
ment passing through a necrotic pulp and through the
foramen most likely carries bacteria and toxins into the
apical tissues (Siqueira et al. 2002, Siqueira & Barnett
2004). An indication by an EAL of reaching the minor
foramen or foramen is very helpful in avoiding
mishaps. Indeed this study showed that WL obtained
with radiographs was 1.0 mm long of the AC 37% of
the time, but 0% for the two EALs. This high incidence
of error is clinically important, because a WL 1.0 mm
long would result in canals being instrumented beyond
the foramen.
Conclusion
Under clinical conditions, the EALs identified the minor
foramen with high degree of accuracy. EALs were more
accurate compared with radiographs with the potential
to greatly reduce the risk of instrumenting and filling
beyond the apical foramen.
Acknowledgements
We thank Dr E. Steve Senia and Dr Michael Hulsmann
for their valuable assistance in reviewing this manu-
script.
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International Endodontic Journal, 43, 16–20, 2010 ª 2010 International Endodontic Journal20
Evaluation of the radiopacity of calcium silicatecements containing different radiopacifiers
J. Camilleri1,2 & M. G. Gandolfi3,4
1Department of Building and Civil Engineering, Faculty for the Built Environment, University of Malta, Msida; 2Department of
Dental Surgery, Faculty of Dental Surgery, University of Malta, Msida, Malta; 3Department of Earth Sciences, University of
Bologna, Bologna; and 4Department of Odontostomatological Sciences-Endodontic Section, University of Bologna, Bologna, Italy
Abstract
Camilleri J, Gandolfi MG. Evaluation of the radiopacity of
calcium silicate cements containing different radiopacifiers.
International Endodontic Journal, 43, 21–30, 2010.
Aim To identify the suitable ratio of alternative
radiopacifiers to impart the necessary radiopacity to
calcium silicate cements (CSC) and assess the purity of
the radiopacifying agents.
Methodology Alternative radiopacifying materials
for incorporation into CSC included barium sulphate,
titanium oxide, zinc oxide, gold powder and silver/tin
alloy. The chemical composition of the alternative
radipacifying materials and bismuth oxide, which is
used in mineral trioxide aggregate (MTA), was deter-
mined using energy dispersive X-ray analysis. In
addition, using an aluminium step-wedge and densi-
tometer, the radiopacity of each material was evaluated
as recommended by international standards. The opti-
cal density was compared with the relevant thickness of
aluminium (Al). A commercial MTA and CSC were
used as controls. Statistical analysis comparing the
radiodensity of the different cements to MTA was
performed using anova with P = 0.05 and post hoc
Tukey test.
Results All percentage replacements of bismuth oxide,
gold and silver–tin alloy powder, and the 25% and 30%
replacements with barium sulphate and zinc oxide had
radiopacities greater than 3 mm thickness of aluminium
(Al) recommended by ISO 6876 (2002). The 25%
replacement of cement with gold powder and 20%
replacement of cement with silver/tin alloy powder
exhibited radiopacity values of 8.04 mm Al and
7.52 mm Al, respectively, similar to MTA (P > 0.05).
The cement replaced with 20% bismuth oxide showed a
radiopacity of 6.83 mm Al, lower than MTA (P = 0.003).
Conclusions Silver/tin alloy and gold powder im-
parted the necessary radiopacity to a calcium silicate-
based cement. Barium sulphate was also a suitable
radiopacifier together with a lower concentration of
silver/tin alloy and gold powder that achieved the
radiodensity recommended by ISO 6876. Further
research is required to investigate the broader proper-
ties of the calcium silicate-based cement with the
different radiopacifiers.
Keywords: bismuth oxide, calcium silicate-based
cement, chemical composition, mineral trioxide aggre-
gate, radiopacity.
Received 20 April 2009; accepted 30 June 2009
Introduction
Calcium silicate-based cements [white Portland cement
and mineral trioxide aggregate (MTA)] are hydraulic
cements composed primarily of tricalcium silicate,
dicalcium silicate and tricalcium aluminate (Taylor
1997, Camilleri et al. 2005, Camilleri 2008b). In
dentistry, MTA is used amongst other things to seal
lateral root perforations (Lee et al. 1993, Pitt Ford et al.
1995) and as a root-end filling material (Torabinejad
et al. 1995a, 1997, Chong et al. 2003, Saunders
2008). Calcium silicate cements (CSC) without radiop-
acifying additives have intrinsic radiopacity values
ranging from 0.86 to 2.02 mm aluminium (Al) (Islam
Correspondence: Dr Josette Camilleri PhD, Department of
Building and Civil Engineering, Faculty for the Built Environ-
ment, University of Malta, Msida MSD 2080, Malta (Tel.: 356
2340 2870; fax: 356 21330190; e-mail: josette.camiller-
doi:10.1111/j.1365-2591.2009.01621.x
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 21–30, 2010 21
et al. 2006, Kim et al. 2008, Saliba et al. 2009), values
lower than the 3 mm aluminium recommended by the
International Standards for dental root canal sealing
materials (ISO 6876 Section 7.8 2002). Thus, a
radiopacifying material has to be added to calcium
silicate-based cements to allow the cement to be
detected radiographically and thus distinguished from
surrounding anatomical structures (Beyer-Olsen &
Ørstavik 1981).
Mineral trioxide aggregate is said to be composed of a
mixture of CSC and bismuth oxide in 4 : 1 ratio
(Torabinejad & White 1995). Bismuth oxide is added
to the MTA to increase the radiopacity of the material.
MTA is commercially available as white and grey
ProRoot MTA (Dentsply, Tulsa Dental Products, Tulsa,
OK, USA) and white and grey MTA-Angelus (Angelus
Solucoes Odontologicas, Londrina, Brazil). The addition
of bismuth oxide increased the radiopacity of the
material to higher levels than the equivalence of
3 mm Al suggested by ISO 6876 (2002). ProRoot
was reported to have a radiopacity ranging from
5.34 mm Al to 6.92 mm Al (Laghios et al. 2000, Chng
et al. 2005, Danesh et al. 2006, Islam et al. 2006, Kim
et al. 2008). White ProRoot MTA showed higher
radiopacity than the grey version (Chng et al. 2005,
Islam et al. 2006, Tanomaru-Filho et al. 2008). MTA-
Angelus demonstrated a radiopacity of 3–3.3 mm Al
(Tanomaru-Filho et al. 2008).
Most of the materials used in endodontics have
radiopacifying agents added to them such as barium or
bismuth compounds. There have been few investiga-
tions on the effect that radiopacifiers have on the
properties of materials. The bismuth oxide added to
white ProRoot MTA has been shown to affect its
hydration mechanism. The bismuth formed part of the
structure of calcium silicate hydrate, replacing the
silica in its structure. Approximately 5% by weight of
bismuth was attached to the calcium silicate hydrate
structure. Bismuth oxide reduced the precipitation of
calcium hydroxide in the hydrated paste (Camilleri
2007) and was also leached out from the material
together with calcium hydroxide (Camilleri 2008b). It
has been reported that bismuth is toxic (Bloodworth &
Render 1992) and induces cell death (Camilleri et al.
2004). Other researchers demonstrated that CSC con-
taining bismuth oxide induced cytotoxicity in dental
pulp cells (Min et al. 2007). Conversely, most research
performed on the biocompatibility of MTA has proved
that this material is biocompatible and induces cell
growth and activity. This may demonstrate that
addition of bismuth oxide to CSC does not seem to
affect the biocompatibility of the material (Kim et al.
2008, Koulaouzidou et al. 2008).
The use of bismuth oxide with CSC has been shown
to be deleterious to the physical properties of the
material, particularly the compressive strength in a
concentration-related manner (Coomaraswamy et al.
2007). This is in accordance with other reports where
Portland cement clinker was used (Camilleri 2008a)
but in opposition to studies reporting no significant
difference in the strength of Portland cement with
varying additions of bismuth oxide (Saliba et al. 2009).
The difference in the results of the studies performed
could be due to nonstandardization of testing when
performing compressive strength tests (Camilleri et al.
2006).
The bismuth oxide in MTA can be replaced by other
radiopacifying materials. Ideally, an alternative radi-
opacifier should only impart the necessary radiopacity
to the cement and should be inert, free from any
contaminants, colourless and nontoxic and be added in
minimal amounts. Addition of minimal amounts of any
material necessitates the use of elements that have a
high relative atomic mass. A number of materials with
high relative atomic masses are already used in dental
practice. Such materials include zinc oxide, which is
used in restorative dentistry, endodontics and peri-
odontology as a base material, root canal sealer and as
a dressing, respectively. Silver–tin alloy is the alloy used
in dental amalgam, gold is used in alloyed form in cast
restorations, and titanium is used for the construction
of endosseous implants. Barium sulphate is used
extensively in the medicine as a radiopacifier for
colonoscopies. The extensive use of these materials in
both medicine and dentistry indicates that the materi-
als have been well researched and thus their interac-
tion with the host tissues should be favourable.
However, not all have been evaluated for implantation
into deep sites.
The addition of a radiopacifier even in minimal
amounts can affect the physical properties of the
resultant material. The replacement of the cement with
a noncementitious material affects the water to cement
ratio (Neville 1981). In turn, variations to the water to
cement ratio affects the workability and the strength of
the resultant material. Other factors that affect the
water required to achieve a workable mixture include
particle size distribution and particle shape.
This study aimed at identifying the suitable ratio of
alternative radiopacifiers for CSC and assessing the
purity and physical properties of the radiopacifiying
agents.
Radiopacity of calcium silicate cements Camilleri & Gandolfi
International Endodontic Journal, 43, 21–30, 2010 ª 2009 International Endodontic Journal22
Materials and methods
The materials used in this study were white calcium
silicate-based cement (Aalborg White, Aalborg, Den-
mark manufactured to BS EN 197-1: British Standard
Institution 2000, type CEM I), and six radiopacifying
materials, which included titanium dioxide (rutile;
Sigma-Aldrich, Gillingham, UK), zinc oxide (Fischer
Scientific, Leicester, UK), barium sulphate (Sigma-
Aldrich), gold powder (Sigma-Aldrich), bismuth oxide
(Fischer Scientific), and silver/tin alloy powder (De-
gussa Dental GmbH, Hanau, Germany). The radiopa-
cifiers and the cement were placed in plastic containers
and were blended by placing the container on a rotary
shaker for 15 min (Luckham 4RT, Burgess Hill, UK).
White ProRoot MTA (Dentsply, Tulsa Dental Products)
and white MTA-Angelus (Angelus Solucoes Odontolog-
icas) were used as controls and received no additional
radiopacifier.
Scanning electron microscopy and elemental
analysis
Scanning electron microscopy of the radiopacifiers was
performed in order to determine the particle shape of the
materials. A thin layer of powder was dispersed onto an
aluminium stub (Agar Scientific, Stansted, UK) over
double-sided carbon tape and then carbon coated (Agar
Scientific) for electrical conductivity. The specimens
were then observed by scanning electron microscope
(SEM; Leo 1430, Philips, Cambridge, UK) and photomi-
crographs were recorded. Energy dispersive X-ray anal-
ysis (EDX) was performed to determine the constituent
elements. Semi-quantitative analysis of cements and
radiopacifiers was performed using a cobalt standard.
Two samples for each material were prepared and the
analysis was performed twice for each sample.
Particle size distribution of powders
The particle size distribution of the radiopacifying
materials was determined using a laser particle size
analyser (CILAS 1180, Orleans, France) having a range
of 0.04–2500 lm.
Evaluation of radiopacity
The radiopacifying materials were added to the calcium
silicate-based cement by replacing 10%, 15%, 20%,
25% and 30% of the cement by weight. Calcium
silicate-based cement without additive, ProRoot MTA
and MTA-Angelus were used as controls. The experi-
mental protocol was based on ISO 6876 Section 7.8
(2002) for dental root canal sealing materials. The
cement and the cement containing the radiopacifiers
were mixed with water, at a water to cement ratio of
0.30 measured by weight of materials. The MTAs were
mixed according to the manufacturer’s instructions.
The materials were compacted incrementally using
hand pluggers into stainless steel ring moulds 10 mm
in diameter and 1 mm high, and pressed against two
glass cover slips to make the specimens 1 mm thick.
Three specimens of each material were prepared. The
cements were allowed to cure for 24 h at 37 �C and
100% relative humidity covered by a plastic sheet to
avoid cement desiccation. After removal from the
moulds, they were stored in distilled water at 37 �C
for 7 days.
The cements were placed directly on a cassette
loaded with a cephalostat type film with an intensifying
screen (Kodak, Rochester, NY, USA) adjacent to a 10-
step aluminium step-wedge made of aluminium, where
each step measured 1 mm in height (Agfa Mamoray,
Agfa Gevaert, Mortsel, Belgium) and X-ray irradiated
using a standard X-ray machine (GEC Medical Equip-
ment Ltd., Middlesex, UK) at tube voltage of 50 kV, and
current 50 mA and exposure time of 0.05 s. The target
to film distance was set at 100 cm. Three specimens per
material under test were arranged on the cassette and
two radiographs were taken of the specimens. Eight
layers of lead foil covered a small area of each film to
obtain a small area of nonexposure. The radiographs
were processed in an automatic processing machine
(Clarimat 300, Gendex Dental Systems, Medivance
Instruments Ltd., London, UK). A photographic densi-
tometer (PTWdensix, Freiburg, Germany) was used to
measure the density of the radiographic images of the
specimens, of each aluminium step and the un-exposed
part of the film. Three density values of each material
were obtained for each radiograph of each specimen
and the mean density was calculated. The net radio-
graphic density was calculated by subtracting the base
and fog value from the gross radiographic density. The
base and fog value is the inherent optical transmission
density (lowest density) of a film base plus the
nonimage density contributed by the developed emul-
sion. Graphs were plotted for net radiographic density
of the aluminium steps (NRDAL) versus the logarithm of
the thickness of aluminium (log d) for each radiograph.
From the resultant plots, the gradient and the intercept
were calculated for each film. Linear regression of the
data was obtained using the following formula:
Camilleri & Gandolfi Radiopacity of calcium silicate cements
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 21–30, 2010 23
NRDAL ¼ m: log d þ I
where NRDAL was the net radiographic density of the
aluminium step wedge, m was the gradient, log d was
the logarithm of the step height, I was the intercept.
By rearranging the above equation into:
log d ¼ I � NRD
m
The logarithm of the relevant thickness of alumin-
ium for each material could be calculated from its net
radiographic density for each film taking into consid-
eration that specimen thickness was 1 mm. Logarithms
of step height were then converted to thicknesses of
aluminium (Watts & McCabe 1999).
Statistical analysis
The data was evaluated using Statistical Package for
the Social Sciences (SPSS) software (SPSS Inc., Chicago,
IL, USA). The distribution was first evaluated to
determine what kind of statistical test would be
performed. The Kolmogorov–Zmirnov test revealed
normal distribution and parametric statistics using
anova with post hoc Tukey test was performed.
Results
Scanning electron microscopy and elemental
analysis
Scanning electron micrographs of the radiopacifying
materials are shown in Fig. 1(a–f). Both zinc oxide and
barium sulphate (Fig. 1b,c respectively) were composed
of very fine particles that were difficult to discern by
SEM even at a magnification of ·2000. Thus, the
magnification was increased until the individual par-
ticles could easily be identified on the micrographs. The
bismuth oxide was composed of elongated needle-
shaped particles (Fig. 1e). The particle shape of gold
(Fig. 1d) and titanium (Fig. 1a) were spherical and the
silver/tin alloy was composed of lathe cut particles
(Fig. 1f). The results of semi-quantitative analysis
(a) (b)
(c) (d)
(e) (f)Figure 1 Scanning electron micro-
graphs of (a) titanium oxide (b) zinc
oxide (c) barium sulphate (d) gold
powder (e) bismuth oxide (f) silver/tin
alloy powder (2000· magnification).
The micrographs for barium sulphate
and zinc oxide were at higher magnifi-
cations because of the small size of the
powders.
Radiopacity of calcium silicate cements Camilleri & Gandolfi
International Endodontic Journal, 43, 21–30, 2010 ª 2009 International Endodontic Journal24
(elemental analysis percentage) of the cements and
radiopacifying materials are shown in Table 1, and the
EDX spectra are shown in Fig. 2. The radiopacifying
materials were mostly pure. The silver/tin alloy powder
had an inclusion of approximately 4% copper. The
calcium silicate-based cement and MTAs were com-
posed of calcium, silicon and aluminium with MTAs
including bismuth. The bismuth loading of MTA-
Angelus was lower than that of ProRoot MTA.
Particle size distribution
The particle size distribution of the radiopacifying
materials is shown in Fig. 3. The barium sulphate
and zinc oxide had very fine particles. Most of the
gold particles ranged between 2 and 4 lm. The
silver/tin alloy powder and bismuth oxide had a
wider range of particle sizes ranging from 0.1 to
53 lm for the silver/tin alloy and 5–100 lm for the
bismuth oxide with the bismuth oxide exhibiting the
largest particle sizes compared with the other radi-
opacifying agents.
Evaluation of radiopacity
The radiopacity values of the materials tested are
shown in Fig. 4. The calcium silicate-based cement
exhibited a low intrinsic radiopacity value of
Table 1 Semi-quantitative analysis of powders using cobalt standard
Material
Elemental analysis (%)
Ag Al Au Ba Bi Ca Cu O S Si Sn Ti Zn
Calcium silicate-based cement 0 0.7 0 0 0 19 0 40 0 9 0 0 0
Titanium dioxide 0 0 0 0 0 0 0 77 0 0 0 22 0
Zinc oxide 0 0 0 0 0 0 0 22 0 0 0 0 90
Silver/tin alloy powder 66 0 0 0 0 0 4 0 0 0 26 0 0
Barium sulphate 0 0 0 7 0 0 0 90 3 0 0 0 0
Gold powder 0 0 100 0 0 0 0 0 0 0 0 0 0
Bismuth oxide 0 0 0 0 62 0 0 12 0 0 0 0 0
White MTA (Dentsply) 0 0.6 0 0 8 29 0 45 0 6 0 0 0
White MTA (Angelus) 0 1.7 0 0 5 32 0 42 0 6 0 0 0
(a) (b)
(c) (d)
(e) (f)
Figure 2 Elemental analysis of (a) tita-
nium oxide (b) zinc oxide (c) barium
sulphate (d) gold powder (e) bismuth
oxide (f) silver/tin alloy powder.
Camilleri & Gandolfi Radiopacity of calcium silicate cements
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 21–30, 2010 25
1.62 ± 0.29 mm Al. The bismuth oxide, gold and
silver/tin alloy replaced cements at all the percentage
replacements and 25–30% cement replaced with bar-
ium sulphate and zinc oxide showed radiopacity values
greater than 3 mm thickness of Al. Thus, these
replaced cements complied with the recommendations
by ISO 6876 Section 7.8 (2002). The radiopacity of
calcium silicate-based cement, all additions of titanium
oxide, the 10% and 15% replacement with barium
sulphate and 10%, 15% and 20% replacement with
zinc oxide demonstrated a radiopacity lower than
3 mm thickness of aluminium.
MTA-Angelus had a lower radiopacity value than
ProRoot MTA (P < 0.001). The MTA-Angelus dis-
played a similar radiopacity to CSC with 10% gold
and silver/tin alloy, to 10% and 15% bismuth oxide
and 25% and similar to 30% barium sulphate and zinc
oxide (P > 0.05). The 25% replacement of cement with
gold powder and 20% replacement of cement with
silver/tin alloy powder displayed radiopacity values of
8.04 ± 0.67 mm Al and 7.52 ± 0.20 mm Al, respec-
tively, similar to ProRoot MTA (P > 0.05). The
cement replaced with 20% bismuth oxide revealed a
radiopacity of 6.83 ± 0.48 mm Al. The radiopacity of
this cement was lower than that of ProRoot MTA
(P = 0.003).
Discussion
In the present study, the radiopacity of calcium silicate-
based cement with varying additions of different
radiopacifying materials was investigated. The different
0
10
20
30
40
50
60
70
80
90
100
0.04 0.
10.
30.
50.
70.
91.
11.
31.
6 22.
4 3 56.
57.
58.
5 10 12 14 16 18 20 25 32 38 45 53 63 75 85 95 106
125
140
150
Diameter µm
Cu
mu
lati
ve v
alu
e %
Titanium oxide
Zinc Oxide
Barium sulphate
Gold
Bismuth oxide
Silver/Tin
Figure 3 Particle size analysis of
radiopacifying materials using laser
particle size distribution.
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
No addition Titaniumoxide
Zinc oxide Bariumsulphate
Goldpowder
Bismuthoxide
Silver/tinalloy
MTADentsply
MTA-Angelus
Addition of radiopacifier to calcium silicate-based cement %
Mea
n t
hic
knes
s o
f al
um
iniu
m m
m
10% 15% 20% 25% 30%
Figure 4 Radiopacity of cement with
varying additions of radiopacifying
materials expressed as mean thicknesses
of aluminium ± SD (n = 2). The dotted
line shows the minimum value for
radiopaque restorative material.
Radiopacity of calcium silicate cements Camilleri & Gandolfi
International Endodontic Journal, 43, 21–30, 2010 ª 2009 International Endodontic Journal26
radiopacifying materials were added by replacing the
amount by weight in percentages varying from 10–
30%.
The materials used to render the cement radiopaque
were powdered metals, metal oxides or salts. The
materials used in this study had no major contami-
nants; thus, the radiopacity increase was due to the
radiopacifier itself and not caused by contamination.
The lack of contaminants was checked on the material
data sheets provided with the chemicals and verified by
semi-quantitative analysis (EDX). The alternative rad-
iopacifying materials replaced the cement portion by
weight. This was carried out to standardize the amount
of radiopacifier added to the cement. The radiopacifier
materials used had different relative atomic masses
which affected the amount of material added to make
up the necessary weight of material used. The water to
cement ratio was standardized and other properties
affecting the physical properties of the resultant mate-
rial were investigated. These included the particle
shape and the particle size distribution. Addition of
small-sized particles increases the specific surface area
and would potentially make the mixture less workable
if the water to cement ratio is kept constant. The effect
that particle shape and particle size distribution of a
cement-replacing material have on the physical prop-
erties of the resultant material are still to be investi-
gated.
The radiopacifiers were chosen because of their easy
availability and the long-term use in dental clinical
practice. In dentistry, titanium is used in dental
composites and porcelain to add whiteness and opacity;
zinc oxide as a base materials under plastic restorative
materials, as temporary restorative materials, as root
canal sealers, as a dressing in periodontal surgery and
is the main constituent compound in gutta-percha
points; silver/tin alloy powder is the c phase of dental
amalgam (Van Noort 2002). The alloy used in the
present study was composed of lathe-cut particles. The
amount of copper was lower than that anticipated for
high copper silver/tin alloys; however, the tests carried
out were semi-quantitative, and thus the precise
amount of copper present could not be determined.
Barium sulphate is a compound characterized by an
extremely low solubility and is clinically used as a
radio-contrast agent for X-ray imaging and other
diagnostic procedures (Ott & Gelfand 1983) such as
imaging of the gastrointestinal tract. It is also used in
root canal filling materials. It has been reported that
the addition of barium sulphate to glass ionomer
cement at low concentrations reduced working and
initial setting times, but further addition delayed the
setting reaction of glass ionomer cements. However,
both compressive strength and surface hardness
decreased with increasing concentrations of the radi-
opacifier (Prentice et al. 2006). The effects of barium
sulphate on the physical–chemical properties of Port-
land cement are yet to be investigated.
In dentistry, bismuth oxide is used as a radiopacify-
ing agent for dental material such as dental acrylic
resin and MTAs. ProRoot MTA has a 20% loading of
bismuth oxide as reported by the manufacturer. The
amount present in MTA-Angelus is not specified by the
manufacturer. The 20% loading for the ProRoot was
verified by Rietveld X-ray diffraction analysis (Camilleri
2008b). Other researchers reported both higher (Song
et al. 2006) and lower bismuth oxide loading for
ProRoot MTA (Oliveira et al. 2007). The bismuth oxide
loading of MTA-Angelus varied from 38.8% to 9%
reported in different studies (Song et al. 2006, Oliveira
et al. 2007, respectively). In the current study, EDX
analysis was used to determine both the purity of the
radopacifiers and also the bismuth oxide loading of
both ProRoot and MTA-Angelus. EDX provides only
semi-quantitative analysis which would explain the
lower level of bismuth oxide detected in ProRoot MTA
when compared with other studies (Camilleri 2008b)
and the data provided by the manufacturer. Bismuth
oxide used in this study was composed of elongated
needle-shaped crystals similar to that previously
observed in ProRoot MTA (Camilleri et al. 2005,
Camilleri 2007).
In the present study, calcium silicate-based cement
revealed an intrinsic radiopacity of 1.62 mm Al, in
accordance with previous studies that reported radio-
pacity values equivalent to 0.95 mm Al (Islam et al.
2006), 2.02 mm Al (Saliba et al. 2009) and 0.86 mm
Al (Kim et al. 2008). This intrinsic value does not
satisfy the recommendation of the International Stan-
dards for dental root canal sealing materials (ISO 6876
Section 7.8 2002). Others have reported radiopacities
equivalent to 3.32 mm Al (Danesh et al. 2006), which
is higher than the recommended 3 mm Al. Thus,
unmodified calcium silicate-based cement is not suit-
able as a root-end filling material or as a sealer as its
presence will not be detected easily on a radiograph. In
the present study, the cement with 20% replaced
bismuth oxide revealed a radiographic density equiva-
lent to 6.83 mm thickness of Al in accordance with
previous studies that reported that the cement with
20% bismuth oxide showed a radiopacity of 6.81 mm
Al (Kim et al. 2008) and 6.62 mm Al (Saliba et al.
Camilleri & Gandolfi Radiopacity of calcium silicate cements
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 21–30, 2010 27
2009). In the present study, the values reported for CSC
replaced with 20% bismuth oxide were not similar to
those obtained for ProRoot MTA (8.26 mm Al). The
radiopacity of MTA-Angelus in the present study was
similar to that reported by others (Tanomaru-Filho
et al. 2008) who reported the radiopacity of MTA-
Angelus to be equivalent to 3 mm Al, which is lower
than that reported for ProRoot MTA by other groups
(Torabinejad et al. 1995b, Laghios et al. 2000, Chng
et al. 2005, Danesh et al. 2006, Islam et al. 2006, Kim
et al. 2008) and also in the present study.
The variation in the results obtained in different
studies is likely because of differences in the cements
tested. Calcium silicate-based cement can be obtained
from a wide range of manufacturers, and thus results
cannot be compared. The full details of the types of
materials used are not always reported nor are the
water/cement ratios specified and other details that
affect the material properties. Particle size and shape
affect the water absorption of the material. Addition of
radiopacifiers composed of very fine particles causes an
increase in water uptake of the material as the specific
surface area is increased, and thus using the same
water/powder ratio the consistency of the resultant mix
can vary. Radiopacifiers that do not absorb water cause
a decrease in the water/cement ratio (Neville 1981).
High water/cement ratios have been reported to cause
a reduction in the radiopacity of the material (Coom-
araswamy et al. 2008).
Specimen size can also affect the resultant radiopac-
ity of the material. ISO 6876 (2002) suggests the use of
specimens 10 mm in diameter and 1 mm thick. Other
researchers (Laghios et al. 2000) have used thicker
specimens thus making comparisons between different
studies difficult. Variations may also arise from differ-
ences in the techniques used to evaluate radiopacity. In
the present study, a technique adopted by Watts &
McCabe (1999) was used to convert the optical density
to thickness of aluminium. The ISO 6876 (2002) does
not give any details in this regard. Other researchers
used linear regression (Laghios et al. 2000) or con-
verted the radiographs to digital images (Kim et al.
2008) and measured the grey pixel value. In most
publications, no details are given whether the base and
fog values were reduced in optical density calculations,
in fact, no technical detail is given on parameters used
(Chng et al. 2005, Islam et al. 2006).
The radiopacity values of a material are related to the
relative atomic mass of constituent elements. The
presence of elements with low relative atomic mass
like titanium and zinc caused low radiopacity values
and increase in the percentage of the material added to
the cement did not increase proportionally the radio-
pacity values of the cement. Materials containing
elements with a high relative atomic mass like bismuth
and gold exhibited high radiopacity values, which were
proportional to the increase in the quantity of material
added to the cement. Barium sulphate, although
having a high atomic number, conferred low radio-
pacity values to the cement. This is due to low levels of
barium element present in the material BaSO4, as
confirmed by EDX analysis.
Gold and silver/tin alloy could potentially be alter-
native radiopacifying materials for use with CSC.
Cement replaced with 25% gold and 20% silver/tin
alloy displayed radiopacity values comparable to Pro-
Root MTA but higher than MTA-Angelus. Thus, gold
and silver/tin alloy powders can both be used to replace
bismuth oxide in MTAs as these alternative materials
impart the necessary radiopacity to the resultant
cement. The use of gold powder could be prohibitive
because of the high cost of the material. In addition,
gold and silver/tin alloy impart a dark colour to the
material and can thus cause tattooing of the adjacent
tissues produced by corrosion products of silver from
the silver/tin alloy. Barium sulphate and zinc oxide
used in 25–30% replacement and lower loadings of
gold, silver/tin alloy and bismuth oxide exhibited
similar radiopacity values to MTA-Angelus. Different
radiopacifier materials and lower loadings can be used
in conjunction with CSC to achieve radiopacity values
greater than 3 mm Al, which is the value recom-
mended by ISO 6876 Section 7.8 (2002). Further
research is required to establish the optimal loading
and the effects that the radiopacifiers have on the other
properties and compatibilities of the calcium silicate-
based cement.
Conclusions
Silver/tin alloy and gold powder impart the necessary
radiopacity to calcium silicate-based cement. In addi-
tion, barium sulphate and zinc oxide represent suitable
radiopacifiers able to confer the radiodensity recom-
mended by ISO 6876. Further research is required to
investigate the properties of the calcium silicate-based
cement with the different radiopacifiers.
Acknowledgements
The University of Malta Research Fund Committee for
funding; Mr J. Sand Damtoft of Aalborg Cement Denmark
Radiopacity of calcium silicate cements Camilleri & Gandolfi
International Endodontic Journal, 43, 21–30, 2010 ª 2009 International Endodontic Journal28
for providing the cement. Mr L. Spiteri of Heritage Malta
for his assistance with the electron microscopy; Mr R.
Mallett of the Biomaterials Department at King’s College
London Dental Institute at Guy’s, King’s and St Thomas’
Hospitals, London for his assistance with the particle size
distribution; Mr E. Grupetta for access to equipment and
Mr R. Spiteri and Ms G. Bonnici, radiographers at Mater
Dei and St Luke’s Hospitals Malta for their help with the
radiography of the samples.
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The effect of sodium hypochlorite andethylenediaminetetraacetic acid irrigation,individually and in alternation, on toothsurface strain
R. Rajasingham1, Y.-L. Ng1, J. C. Knowles2 & K. Gulabivala1
1Unit of Endodontology, and 2Unit of Biomaterials Science, Divisions of Restorative Dental Sciences and Biomaterials Science and
Tissue-Engineering, UCL Eastman Dental Institute, University College London, London, UK
Abstract
Rajasingham R, Ng Y.-L, Knowles JC, Gulabivala K. The
effect of sodium hypochlorite and ethylenediaminetetraacetic
acid irrigation, individually and in alternation, on tooth surface
strain. International Endodontic Journal, 43, 31–40, 2010.
Aim To evaluate the effect of irrigation regimens on
tooth surface strain using saline, sodium hypochlorite
(3% and 5% NaOCl) and ethylenediaminetetraacetic
acid (17% EDTA), individually and in alternating
combinations.
Methodology Single-rooted premolar teeth with
single canals prepared to standardized dimensions
were grouped by anatomical features and randomly
distributed amongst six experimental groups (n = 12
each). The six groups were: (1) saline; (2) 5% NaOCl;
(3) 3% NaOCl; (4) 17% EDTA; (5) 3% NaOCl and
17% EDTA; (6) 5% NaOCl and 17% EDTA. All
groups underwent four (group 1) or five (groups 2, 3,
4, 5, 6) sequential 30-min irrigation periods follow-
ing each of which the tooth was subjected to a
standard regime of cyclic, nondestructive, occlusal
loading. Tooth surface strain was measured during
each loading cycle using electrical strain gauges
mounted cervico-proximally. The data were analysed
by Hierarchical anova and post hoc multiple com-
parisons.
Results Irrigation with 5% NaOCl alone or alternat-
ing with 17% EDTA significantly (P < 0.001) increased
the peak strain values for each of the irrigation periods
compared with that of saline (group 1). The data for the
other groups revealed no significant differences com-
pared with those of saline. The strain increase after the
fourth irrigation cycle was significantly higher for group
6 than for group 2. The measured canal morphology
and dentine thickness parameters did not prove to have
a significant effect on tooth surface strain.
Conclusions Irrigation with 5% NaOCl acting alone
or alternated with 17% EDTA (used in 30 min cycles),
significantly increased tooth surface strain. The alter-
nated regimen showed significantly greater changes in
tooth surface strain than NaOCl alone. Irrigation with
3% NaOCl and 17% EDTA individually or in combina-
tion did not significantly alter the tooth surface strain.
Keywords: ethylenediaminetetraacetic acid, irriga-
tion, sodium hypochlorite, tooth surface strain.
Received 28 January 2009; accepted 15 July 2009
Introduction
It is widely believed that root filled teeth are more
susceptible to fracture than teeth with vital pulps
(Rosen 1961, Johnson et al. 1976, Gher et al. 1987)
but conclusive evidence is lacking. Nevertheless, there
is circumstantial evidence for putative causes of non-
vital and root filled tooth fracture (Burke 1992). The
main causes could be: loss of tooth tissue, altered
physical properties of dentine, and altered propriocep-
tive/nociceptive properties (Gutmann 1992, Gulabivala
1995, Kinney et al. 2003). These factors probably
interact cumulatively to influence tooth loading, stress
distribution and, ultimately result in catastrophic
failure.
Correspondence: K. Gulabivala, Professor and Head of Endod-
ontology, UCL Eastman Dental Institute, 256 Gray’s Inn Road,
London WC1X 8LD, UK (Tel.: 020-7915-1033; fax: 020-
7915-2371; e-mail: [email protected]).
doi:10.1111/j.1365-2591.2009.01625.x
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 31–40, 2010 31
Tooth tissue loss reduces the force required to strain
and ultimately fracture teeth in vitro. The pattern of
tooth tissue loss influences the magnitude of the
induced strain (Mondelli et al. 1980, Larson et al.
1981, Panitvisai & Messer 1995, Lang et al. 2006);
clinical studies confirm these observations (Cavel et al.
1985, Hansen et al. 1990). The relative importance of
intact marginal ridge and the width/depth character-
istics of cavities are under debate, but original tooth
anatomy may also play a part (Khera et al. 1990).
Endodontic access cavities potentially weaken teeth
further (Reeh et al. 1989, Howe & McKendry 1990,
Panitvisai & Messer 1995) as does wide preparation of
canals (Hansen & Asmussen 1993, Lang et al. 2006).
The properties of dentine have been investigated
intensively and may be influenced by many factors
(Kinney et al. 2003, Kishen 2006). Factors investigated
include: changes in moisture content (Helfer et al.
1972, Huang et al. 1992, Jameson et al. 1994, Papa
et al. 1994, Kishen 2006), nature of collagen (Rivera
et al. 1988) and standard laboratory physical proper-
ties (Lewinstein & Grajower 1981, Carter et al. 1983,
Huang et al. 1992, Sedgley & Messer 1992). Unfortu-
nately, the findings have been contradictory or equiv-
ocal and no definitive proof of mechanical weakening of
dentine exists, except for the influence of water content.
The fundamental problem is that all ex vivo tests are by
definition on teeth without vital pulps and it is
debatable whether teeth can become significantly
dehydrated in the mouth.
Two studies (Loewenstein & Rathkamp 1955, Ran-
dow & Glantz 1986) suggest that pulp necrosis or loss
compromises the tooth’s proprioceptive/nociceptive
properties, predisposing to greater loading in function
with consequent increased likelihood of fracture (Ran-
dow & Glantz 1986).
In addition to these factors, there is increasing
evidence that intracanal irrigants, medicaments and
materials also influence the physical and mechanical
properties of dentine. The implicated materials include
sodium hypochlorite (NaOCl) (Grigoratos et al. 2001,
Sim et al. 2001, O’Driscoll et al. 2002, Oyarzun et al.
2002, Slutzky-Goldberg et al. 2004), hydrogen perox-
ide (Chng et al. 2002), MTAD (Machnick et al. 2003),
chloroform, xylene and halothane (Rotstein et al.
1999), calcium hydroxide (Grigoratos et al. 2001,
Andreasen et al. 2002, Rosenberg et al. 2007) and
eugenol (Biven et al. 1972).
Sodium hypochlorite and ethylenediaminetetraacetic
acid (EDTA) are widely used during root canal treat-
ment for established and sound biological reasons
(Bystrom & Sundqvist 1985). However, their potential
influence on the biomechanical properties of teeth and
dentine has only recently gained significant attention
(Yamada et al. 1983, Dogan & Calt 2001, Grigoratos
et al. 2001, Sim et al. 2001, Calt & Serper 2002). A
laboratory study by Sim et al. (2001) found that
irrigation with a 5.25% solution of NaOCl significantly
increased the tooth surface strain of dentine using
cyclical nondestructive loading in a whole tooth model.
The possible mechanisms involved in dentine weaken-
ing were shown to be due to the disintegration of the
organic element, leaving the mineral component intact
(O’Driscoll et al. 2002). Sim et al. (2001) found that
sequential, repeated 30-min irrigation steps with
5.25% NaOCl did not result in a linear increase in
tooth surface strain but one that plateaued after the
first two steps. This may be because the mineral
component of dentine is not depleted and consequently
poses a barrier to further NaOCl penetration. It may be
further hypothesized that the use of EDTA, an agent
that chelates the calcium may deplete the inorganic
component of dentine and expose more of the organic
structure for further depletion. Therefore, alternate
irrigation with NaOCl and EDTA (Yamada et al.1983,
Marending et al. 2007) may eliminate the ‘plateauing’
tendency evident when irrigating solely with NaOCl
(Dogan & Calt 2001, Calt & Serper 2002, Yoshioka
et al. 2002).
The aims of this study were to evaluate the effect of
irrigation on tooth surface strain when using saline,
NaOCl (3%, 5%) and EDTA (17%) individually, and in
alternate combination as follows; irrigation with NaOCl
(either 3% or 5%) followed by EDTA (17%).
Materials and methods
Preparation of teeth and allocation to experimental
groups and anatomical sub-groups
Human extracted teeth were obtained with consent
from patients undergoing routine extractions for ortho-
dontic or restorative reasons. Seventy-two single-rooted
premolars with single root canals, all of which were
noncarious and crack-free (confirmed by transillumi-
nation under a microscope), were used after temporary
storage in 4% formal-saline (Lam & Gulabivala 1996)
immediately following extraction. Gross debris on the
external surfaces of the teeth was removed with a sharp
scalpel. The crowns of the teeth were removed 4 mm
coronal to the cemento-enamel junction with a dia-
mond bur in a high-speed hand-piece leaving a
Effect of irrigants on tooth strain Rajasingham et al.
International Endodontic Journal, 43, 31–40, 2010 ª 2010 International Endodontic Journal32
flattened surface that was perpendicular to the long
axis of the tooth. The remaining enamel was removed
with a high-speed hand-piece (Sim et al. 2001).
The access cavity size and shape were dictated by the
form of the pulp chamber and was not standardized.
Access to the canals was standardized with Profile�
orifice shapers (Maillefer Instruments, Ballaigues, Swit-
zerland), the pulps were extirpated with a Hedstrom�
file (Kerr UK, Peterborough, UK) and the canals were
prepared to a standard maximum apical size (30) and
taper (0.06), where preoperative canal size allowed
engagement of dentine; no attempt was made to gauge
canal diameter and enlarge further by a standard
number of instruments. Each canal was prepared to the
apical foramen, the position of which was determined
by the emergence of a size 10 file through it. A crown-
down sequence of Profile� nickel–titanium endodontic
instruments (Maillefer Instruments) was used with
saline as the irrigant. The teeth were maintained in a
hydrated state within saline-soaked tissue paper during
all procedures. Following canal preparation, the apices
were sealed with two coats of nail varnish (Boots No.17
Clear Nail Varnish, Nottingham, England).
Periapical radiographs in two planes (bucco-lingual
and mesio-distal) were taken for all teeth. The width of
the dentine at the cemento-enamel junction on the two
radiographic views was measured with digital callipers
and the average obtained. The teeth were grouped into
like types by anatomical features; the main criterion
was the apico-coronal position at which the root canal
started to narrow as follows: (i) immature apex or no
canal narrowing; (ii) coronal 1/3; (iii) middle 1/3; and
(iv) apical 1/3. The middle and coronal groups were
further partitioned by root length. This resulted in six
anatomically distinct groups with 12 teeth in each
group; teeth from each anatomical group were ran-
domly assigned amongst six experimental irrigation
groups to give a sample size of 12 per group.
Mounting of teeth and bonding of strain gauges
Clear acrylic resin (Specifix-20, Struers Epoxy resins;
Struers A/S, Copenhagen, Denmark), mixed according to
the manufacturer’s instructions was used to secure each
tooth centrally within circular plastic moulds (2.5 cm
high). The long axes of the teeth were strictly aligned
parallel to the walls of the plastic moulds and 2–3 mm of
the root was left exposed below the cemento-enamel
junction, simulating the level of the alveolar bone.
Constantan strain gauges (gauge factor = 2.05;
Measurements Group UK Ltd, Basingstoke, UK) with
short attached copper leads (resistance = 120 X; type
EA-06-062AP-120, option LE) were used. The gauge
polyimide backing was trimmed to an 1-mm border to
enable easier positioning on the tooth (Fig. 1). The
proximal bonding site on each tooth was prepared by
rinsing with water, drying with air (3-in-1 syringe) and
application of a thin layer of cyanoacrylate adhesive
(M-Bond 200 Adhesive, Measurements Group UK Ltd).
The gauge was positioned with the top edge of the
backing 1 mm below the occlusal surface and vertically
aligned along the long axis of the tooth, using an
engineering T-square. Gentle but firm pressure was
applied until the adhesive had set. The strain gauge and
exposed wire leads were protected with M-Coat D air-
drying acrylic varnish (Measurements Group UK Ltd).
The teeth were wrapped in damp gauze and placed in a
sealed polythene bag for storage until use. Every effort
was made to prevent dehydration of the teeth during
testing using damp gauze. Shortly before use, a length
Straingauge
Instron grip
Premolar with flattened coronal face
Point at whichload is applied
Figure 1 Experimental set-up of tooth,
acrylic holder and strain gauge.
Rajasingham et al. Effect of irrigants on tooth strain
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 31–40, 2010 33
of shielded twin cable (RS Components Ltd, Corby, UK)
was soldered to the copper leads and the resistance of
the gauge checked with an Ohm-meter to ensure
absence of component burnt out.
Preparation of strain gauge circuit
The ‘active’ strain gauge on the tooth was incorporated
as one arm of a ‘quarter bridge’ Wheatstone bridge
circuit; two arms consisted of a precision wirewound
1 kX resistor (RS Components Ltd) and the fourth arm
incorporated a ‘dummy’ strain gauge bonded to a tooth
for temperature compensation. A 100 kX precision
wirewound resistor (RS Components Ltd) with a switch
in parallel with the active gauge, served to calibrate the
strain gauge circuit. Shielded cable was used to
minimize electro-magnetic interference from proximal
equipment. The excitation voltage to the Wheatstone
bridge circuit was supplied by an RDP Transducer
Indicator E308 (RDP Electronics Ltd, Wolverhampton,
UK) and was set at 1.45V continuously for the duration
of the experimental period. This also amplified and
displayed the output voltage from the circuit and
allowed zeroing prior to loading. The strain-induced
voltage could then be measured relative to this base-
line. The output from the Wheatstone bridge circuit
was also logged via the transducer by a computer. The
software used (Waveview for Dos 1.24; Eagle Appli-
ances Pty Ltd, Brighton, UK) was set to sample the
output at intervals of 0.1 s.
Preparation of experimental solutions
The physiologic saline was commercially obtained
(Baxter Healthcare Ltd, Thetford, UK), whilst the 3%
and 5% solutions of NaOCl were diluted from 12%
NaOCl stock (BDH Laboratory Supplies, Poole, UK) and
the concentrations verified by iodometric titration. A
17% solution of EDTA (BDH Laboratory Supplies) was
obtained by adjusting the appropriate mass in water at
pH 7.8. Freshly made solutions were stored in opaque
bottles under controlled room temperature until use
but never longer than 2 weeks.
Irrigation regimen per experimental group
The teeth in groups 1–6 were exposed to four or five
sequential 30-min standardized irrigation cycles
(Table 1). Each 30-min irrigation cycle consisted of
delivering 10 mL of test solution as follows: (i) irriga-
tion with 3 mL over 1 min followed by agitation with
size 25 Flexo-file (Maillefer Instruments) for 10 s and
leaving undisturbed for 50 s; (ii) irrigation with 0.5 mL
over 20 s, followed by agitation for 10 s, and then
leaving undisturbed for 90 s; (iii) cycle 2 was repeated
13 more times. At the end of this period, the canals
were flushed with 9 mL saline over 3 min. In total
therefore, each irrigation cycle consisted of 33 min
(30 min test solution and 3 min saline).
Cyclic loading
Following each 30-min irrigation period, each tooth
was subjected to a standard regime of cyclic nonde-
structive occlusal loading (Goldsmith et al. 2002).
Tooth surface strain was measured during each loading
cycle. To perform the loading, the acrylic block
containing the test tooth was secured in a brass
receptacle with four restraining screws. The receptacle
was clamped via an attachment to the crosshead of a
Universal loading machine (Instron Ltd, High
Wycombe, UK). A ball bearing of 5.0 mm diameter
fixed to the end of the loading arm (with 1kN load cell)
delivered the load accurately to the centre of the tooth
access preparation along its long axis, by adjustment of
the receptacle position. Once positioned, the tooth was
not moved during the entire testing procedure; access
for irrigation procedures being achieved by lowering
the crosshead to leave 5 cm between the end of the
loading arm and the tooth.
Each loading cycle consisted of 3 stages: (1) Loading
from 0 N to 20 N (the pre-load); (2) Five cycles of
loading from 20 N up to 110 N and unloading down to
20 N at a crosshead speed of 0.7 mm/s (usually
completed over 2–3 mins); and (3) Unloading from
20 N to 0 N. The pre-load was set at the start of each
cycle through the Instron console, whilst the loading
regime was controlled by the Instron Series XII
software (Instron Ltd).
Strain measurement
At completion of the first irrigation cycle, the bridge
was balanced to zero and output logging was com-
menced. After 15–20 s, the calibration resistor was
activated for 20 s and the zero dial adjusted to record a
second baseline value before the loading procedure was
commenced; the baselines facilitated later calculations.
The data sampled from the output voltage were saved
electronically at the end of the loading period. The
irrigation and loading procedures were repeated four
(Group 1) or five (Groups 2, 3, 4, 5, 6) times for each
Effect of irrigants on tooth strain Rajasingham et al.
International Endodontic Journal, 43, 31–40, 2010 ª 2010 International Endodontic Journal34
tooth, generating four or five data files per tooth. The
entire experimental period was completed in a single
sitting for each tooth.
Five peak outputs were obtained from the recorded
data for each loading period and a mean value
calculated (peak strain value). The data were analysed
using the STATA software programme (stata version 9
2005; STATA Corporation, College Station, USA). The
change in the mean strain values of teeth following
each irrigation period from the baseline were calculated
for each experimental group and analysed using the
hierarchical anova analysis followed by the Bonferroni
analysis.
Results
The mean peak strain values of the teeth after each
consecutive irrigation period are summarized by each
experimental group in Table 1. In group 1 (negative-
control saline), there was little change in these values
following each consecutive irrigation period. In groups
2 (positive control 5% NaOCl) and 6 (5% NaOCl/17%
EDTA), there was marked increase in strain values
following the second and third irrigation periods, this
increase plateaued at the fourth irrigation period for
teeth without the alternate irrigation with 17% EDTA
(Group 2). In groups 3 (3% NaOCl) and 5 (3% NaOCl/
17% EDTA), there was a proportionately smaller
increase in the strain values following the second and
the third irrigation periods, but again this increase
plateaued for the teeth without the alternate irrigation
with 17% EDTA (Group 3). In group 4 (17% EDTA),
there was a continuous but small increase in the strain
values following each irrigation period. For test groups
2–4, there was no significant difference between the
mean peak strain values obtained after the fourth (test
solution) and fifth (saline) irrigation cycles. In contrast,
the difference was significant (P = 0.002) for the teeth
in group 6, although the magnitude was small (4.8 le;
95% CI 2.8 le, 6.7 le) (Table 1). Therefore the values
obtained following the fifth irrigation cycle were not
considered when comparing the changes in mean peak
strain.
The difference in the mean peak strain values for teeth
after each irrigation period and the baseline are plotted
by each experimental group in Fig. 2. The differences in
the changes in the mean peak strain values were found
to be normally distributed. Hierarchical anova analysis
showed that there was a significant interaction
between test groups and irrigation period (P < 0.001)
with significant differences between the test groups
(P < 0.001). This indicated that the rates of change of
Table 1 Mean peak strain values
[microstrains (le)] and standard devia-
tions (n = 12) for each group and irri-
gation cycle depicted by time and cycle
number. The irrigant used at each
30 min cycle is also shown
Time (min)
1 Baseline 2 3 4 5
30 60 90 120 150
Group 1
Irrigant Saline Saline Saline Saline
Mean 507.6 520 510.5 515.4
SD 343.4 359.9 337.8 344.8
Group 2
Irrigant Saline 5%NaOCl 5%NaOCl 5%NaOCl Saline
Mean 319.0 404.8 450.6 431.1 427.6
SD 93.1 125.6 144.9 162.4 162.5
Group 3
Irrigant Saline 3%NaOCl 3%NaOCl 3%NaOCl Saline
Mean 259.0 273.8 294.2 284.7 273.1
SD 136. 8 141.4 142.2 132.3 137.5
Group 4
Irrigant Saline 17%EDTA 17%EDTA 17%EDTA Saline
Mean 229.3 234.7 241.2 245.6 247.2
SD 140.3 138.6 137.0 135.8 136.4
Group 5
Irrigant Saline 3%NaOCl 17%EDTA 3%NaOCl Saline
Mean 370.0 386.3 396.3 409.3 409.0
SD 233. 9 234.9 235.5 235.9 238.8
Group 6
Irrigant Saline 5%NaOCl 17%EDTA 5%NaOCl Saline
Mean 231.9 317.3 355.7 434.5 439.3
SD 129.2 176.5 190.3 246.9 247.7
Rajasingham et al. Effect of irrigants on tooth strain
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 31–40, 2010 35
tooth surface strain between groups were significantly
different. In contrast, the irrigation cycle (P = 0.3),
average dentine thickness (P = 0.8) and canal mor-
phology (P = 0.5) had no significant influence on the
changes in the strain values. Multiple comparisons
between test groups for each period were subsequently
carried out using the Bonferroni test. Following the
second, third and fourth irrigation periods, the changes
in mean peak strain values of teeth in groups 2 (5%
NaOCl) and 6 (5% NaOCl/17% EDTA) were signifi-
cantly (P < 0.001) higher than those in group 1
(negative-control saline) and other experimental
groups. There were no significant differences
(P = 1.0) in the changes between teeth in group 1
(saline) and those in groups 3 (3% NaOCl), 4 (17%
EDTA) and 5 (3% NaOCl/17% EDTA). Following the
second and third irrigation periods, the differences in
the change of mean peak strain values between groups
2 and 6 (P = 1.0) and between groups 3 and 5
(P = 1.0) were not significant. However, the change
was significantly (P = 0.02) higher in group 6 com-
pared with group 2 following the fourth irrigation
period.
Discussion
Previous work (Goldsmith et al. 2002, Sim et al. 2001)
had suggested that root canal irrigation with suffi-
ciently concentrated NaOCl could alter tooth surface
strain, potentially predisposing teeth to fracture. This
effect was attributed to depletion of the organic content
of the root canal surface dentine (O’Driscoll et al.
2002). It has been suggested that alternation of
irrigation with 17% EDTA could facilitate greater
bacterial load reduction (Bystrom & Sundqvist 1985),
removal of the smear layer and bacterial biofilm from
noninstrumented surfaces (Gulabivala et al. 2005). The
potential disadvantage of this combination may be that
alternate depletion of organic and inorganic substrate
may allow the tooth to be weakened further as
demonstrated by an increase in tooth surface strain.
To test this hypothesis, the previous work was repeated
with a relevant study design and stringent attention to
detail in order to overcome the data variation seen in
the experiments of Goldsmith et al. (2002).
The 72 teeth used in this study were single-rooted
premolars with single root canals. The teeth were
grouped anatomically according to the location of root
canal narrowing and root length. Sim et al. (2001) had
standardized their sample by using mandibular second
premolars with single mature roots, whilst Goldsmith
et al. (2002) used a mixture of single and two-rooted
premolars with mature or immature apices. As would
be expected, the latter study showed greater variability
of the data. It is difficult to ‘quantify’ tooth anatomy but
the adopted method indirectly described the dentine
distribution within the tooth. The potential confound-
ing effect of tooth anatomy was reduced by stratified
randomized allocation of teeth and accounted for in the
hierarchical anova analysis by incorporating the
average thickness of dentine at the cemento-enamel
junction as well as canal morphology as co-variates.
The remaining enamel from the coronal 4 mm
of the prepared teeth was removed to show the effect
of the irrigant on dentine, since it has been shown that
the band of enamel around the cervical dentine has a
significant effect on tooth stiffness (Meredith 1992, Sim
et al. 2001). Equally, this measure should be taken into
Change in strain from first irrigation
–50
0
50
100
150
200
250
300
2 3 4 5 6
Irrigation period
Str
ain
(u
nit
s)Group 1Group 2Group 3Group 4Group 5Group 6
Figure 2 Graph depicting change in
mean peak strain values (microstrains
[le]) from baseline, with confidence
interval lines (colour coded); the obvi-
ously different groups are 2 and 6.
Effect of irrigants on tooth strain Rajasingham et al.
International Endodontic Journal, 43, 31–40, 2010 ª 2010 International Endodontic Journal36
account when considering the clinical implications of
the results. The root canals were prepared to a
standardized taper to allow the irrigating needle to
penetrate to a realistic depth towards the apices; the
precise method of preparation was not considered
important (Sim et al. – balanced force with hand files;
Goldsmith et al. – Quantec� 2000 instruments), as
long as stresses were not induced in the residual
dentine.
A clear acrylic resin (epoxy) was used for mounting
in this study because it showed minimal dimensional
change after setting compared to self-curing acrylic
resin used by Goldsmith et al. (2002).
The single-element strain gauge used by Goldsmith
et al. (2002) was again chosen for this study in
contrast to the rosette gauge used by Sim et al.
(2001) because the latter found that the main axial
loading stress was compressive and was mainly
recorded by the gauge element orientated in the
longitudinal axis. The location of the single-element
strain gauge was determined by the outcome of full
field stress pattern analysis (SPATE), which showed the
chosen site to be a zone of stress concentration during
loading of posterior teeth (Meredith 1992). Other
studies also concur regarding the distribution of strains
within loaded teeth (Asundi & Kishen 2000, Palamara
et al. 2002).
The choice of solutions and their concentrations were
informed by clinical usage and prior work (Grigoratos
et al. 2001, Sim et al. 2001, Goldsmith et al. 2002). A
9 mL saline final flush immediately prior to occlusal
loading, as per Sim et al. (2001) was repeated here
because Goldsmith’s work was suggestive of possible
tooth dehydration during NaOCl irrigation. Figure 2 did
not indicate significant alteration due to the final saline
irrigation phase but minor fluctuations during record-
ing confirmed the probability of some minor individual
tooth-related effect due to ‘dehydration’.
The maximum load applied (110 N) and the rate of
loading and unloading was the same as that used by
Goldsmith et al. (2002). The actual time taken to
complete a loading cycle differed between sample teeth
(range: 20–30 s) but remained constant for individual
teeth at each of the five loading periods. The range of
20 N to 110 N is within ‘physiological limits’ for the
human dentition (De Boever et al. 1978).
Values of peak strain reported in this study were
slightly higher than those found by Sim et al. (2001),
but were of the same order of magnitude as those
reported by Meredith (1992) and Goldsmith et al.
(2002). The wide range of baseline strain values seen
in all experimental groups can be accounted for at least
partly by the position of the loading arm on the
flattened surface of the resected crown. Once the tooth
position was fixed in the Universal loading machine, it
remained constant throughout the test, allowing com-
parison between irrigation cycles and for each tooth to
act as its own control. The magnitude of strain
recorded at the cervical target site was dependent on
loading position. Other factors expected to influence
strain might be tooth anatomy and dentine thickness.
Although the precise thickness of coronal dentine was
not measured after tooth preparation, one would expect
higher strain values to be found in teeth with the
thinnest walls (Goldsmith et al. 2002). In the present
study, neither of the tooth anatomy parameters (aver-
age dentine thickness at the cemento-enamel junction
and canal morphology) were found to have a signifi-
cant influence on the change in tooth surface strain.
This negative finding may be true or could possibly be
attributed to the crude and possibly inaccurate estimate
of dentine thickness obtained from radiographic
images. It may also be hypothesized that whilst there
may be straining of the dentine at the point of loading,
the transmission of this strain through the entire
thickness of dentine may be limited at certain surfaces
(given the complex nature of resolution of tensile and
compressive stresses and strains), resulting in absence
of detection at the point of measurement (Lertichira-
karn et al. 2003).
The potential issue of recovery time between cycles
was addressed by Sim et al. (2001) and data from this
study confirmed that on the whole, the possibility of
accumulative strain was not a problem. Occasional
unexpected changes in strain in individual samples
were attributed to micro-fractures propagating with
each loading cycle or errors in strain gauge positioning.
It was evident that the method was sufficiently sensitive
and transparent to detect such aberrant readings.
The effect of 5% NaOCl irrigation had yielded
contrasting results in the two previous reports (Sim
et al. 2001, Goldsmith et al. 2002), the latter of which
had considerable variation in their data. The present
study clearly confirmed that the findings of Sim et al.
(2001) were reliable and that consistent patterns may
only be revealed with precise attention to detail in the
experimental set-up. The key steps of influence were:
(i) alignment of the strain gauges to the long axis of the
tooth; (ii) flattening of the occlusal surface of the tooth
to allow true perpendicular loading; and (iii) mounting
of the tooth in a resin with minimal dimensional
changes. All 12 teeth showed an increase in peak strain
Rajasingham et al. Effect of irrigants on tooth strain
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 31–40, 2010 37
values after irrigation with 5% NaOCl followed in the
majority by a plateauing of strain increase.
Alternate irrigation with 5% NaOCl and 17% EDTA
resulted in increases in tooth surface strain that were
highly significantly different from the saline control; the
plateauing of strain increase (evident with irrigation
with 5% NaOCl alone) was eliminated as predicted by
the test hypothesis. The results therefore support the
hypothesis that alternate irrigation with NaOCl (5%)
and EDTA (17%) probably allows the alternate deple-
tion of organic and inorganic material, with a greater
accumulative depth of effect on dentine and therefore
tooth surface strain. Teeth undergoing root canal
treatment, already compromised by loss of tooth
structure, particularly with breaks in the continuity
of the band of circumferential enamel, could be further
weakened by 5% NaOCl irrigation acting alone but
particularly when alternated with 17% EDTA. The
increase in strain, although significant, does not yet
indicate whether it is sufficient to result in increased
risk of tooth fracture due to fatigue. It could be
hypothesized that since such irrigation patterns pro-
duce surface flaws in dentine (Calt & Serper 2002),
cyclic loading at the normal stresses of mastication may
allow fatigue crack growth to catastrophic proportions
(Kinney et al. 2003, Kishen 2006).
Irrigation with 3% NaOCl and 17% EDTA individu-
ally or in combination showed similar trends as for the
higher concentration sodium hypochlorite solution
(Fig. 2) but the difference was not significant and the
groups were comparable to the saline control. The
negligible changes in strain from baseline values for all
teeth irrigated with 17% EDTA alone implies the effect
on inorganic component of dentine is confined enough
to not affect tooth surface strain significantly. Alternate
irrigation with 3% NaOCl and 17% EDTA produced
small but noticeable increases in strain values between
the third (17% EDTA) and fourth (3% NaOCl) irrigation
cycles in some teeth. The duration, concentration and
irrigant combination appear to be critical as shown in
other in vitro work (Marending et al. 2007). The slight
reduction in peak strain values for some teeth, follow-
ing the final saline irrigation could be explained by
rehydration of the dentine, as anticipated from Gold-
smith et al. (2002).
The irrigation regime as used during the cyclic
nondestructive loading phase may not be directly
comparable to the clinical practice of all practitioners;
nevertheless it was well defined and provided key
insight into the potential clinical effects. In the clinical
scenario, the irrigant would have to contend with more
organic tissue in the root canal system and would
therefore become spent more rapidly. In this study,
pulpal tissue was removed during the canal preparation
stage, prior to irrigation with NaOCl and EDTA. The
intention was to test the worst case scenario to find any
differences, if they existed.
Irrigation with 3% NaOCl on its own, despite
showing some increase in strain values, was not
significantly different from irrigation with saline and
may be a ‘safer’ concentration to use. Its antimicro-
bial and tissue-dissolving properties should be ade-
quate (Bystrom & Sundqvist 1985, Baumgartner &
Cuenin 1992). It would be prudent to select a
suitable lower concentration of NaOCl that would
have minimal undesirable effects on the physical
properties of dentine.
Likewise, the use of EDTA on its own did not result in
any significant difference from irrigation with saline.
The experiment provided no evidence for depletion of
structural components that could induce alteration in
the mechanical properties of the teeth.
Conclusions
This study showed that within the confines of its
design, irrigation with 5% NaOCl alone but especially
when alternated with 17% EDTA for sufficient duration
may significantly increase tooth surface strain.
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Effect of restorations on pulpal blood flow in molarsmeasured by laser Doppler flowmetry
N. P. Chandler1, T. R. Pitt Ford2 & B. D. Monteith1
1Department of Oral Rehabilitation, School of Dentistry, University of Otago, Dunedin, New Zealand; and 2Department of
Conservative Dentistry, Dental Institute, King’s College London, London, UK
Abstract
Chandler NP, Pitt Ford TR, Monteith BD. Effect of resto-
rations on pulpal blood flow in molars measured by laser
Doppler flowmetry. International Endodontic Journal, 43, 41–46,
2010.
Aim To: (i) compare laser Doppler pulpal blood flow
(PBF) signals from restored and unrestored first molar
teeth, (ii) investigate PBF in teeth with large and small
restorations, and (iii) to relate PBF to pulp chamber
dimensions on radiographs.
Methodology Bitewing radiographs of young adults
with restored first molars were obtained and pulp
chamber dimensions measured. Subjects were divided
into 2 groups: group A with a restored tooth and an
unrestored contralateral (43 subjects) and group B,
those with a molar with a small (usually occlusal)
restoration whilst the contralateral tooth had an
extensive occlusal restoration (or restorations) or
restored proximal surface(s) and/or cuspal overlay
(31 subjects). The 148 teeth responded to electric pulp
testing, and their PBF was recorded using a laser
Doppler flowmeter. Data were analysed using Student’s
t-test.
Results In group A the PBF in the restored teeth was
significantly lower than in unrestored contralaterals
(P = 0.028) and the total pulp chamber area and that
in the clinical crown were smaller (P = 0.039 and
0.021 respectively). The group B molars with large
restorations had significantly lower PBF than contra-
laterals with small restorations (P = 0.001), and their
total pulp chamber area and pulp chamber width at
cervix were reduced significantly (P = 0.003 and
0.032 respectively).
Conclusions In molars the size of the pulp chamber
was influenced by the presence of restorations and the
PBF was reduced when restorations were present. Size
and extent of restorations had a significant effect on PBF.
Keywords: bitewing radiographs, endodontics, laser
Doppler flowmetry, pulp vitality.
Received 20 August 2008; accepted 5 August 2009
Introduction
Conventional pulp sensitivity tests rely on an intact
nerve supply and a patient response to a noxious
stimulus. Problems of electric pulp testing restored
posterior teeth include limited access to enamel and/or
dentine and the leakage of current via metallic resto-
rations or adjacent teeth (Pantera et al. 1992, Myers
1998). A test involving blood perfusion such as laser
Doppler flowmetry (LDF) eliminates the need for a
patient response. LDF has been used to assess the pulp
condition of anterior teeth, but few investigators have
focused on posterior teeth or teeth with restorations.
Whilst endodontic diagnosis involves integration of
clinical and radiographic findings, in a study of
treatment need only one-third of molars with disease
could be diagnosed from radiographs alone, compared
with half of the incisors (Petersson et al. 1986).
Improvements to pulp testing of posterior teeth are
therefore important, especially when there is a risk of
misdiagnosis and the economics of molar root canal
treatment are considered.
The aims of this study were to investigate pulpal
blood flow (PBF) in first molar teeth of subjects of
Correspondence: Associate Professor Nicholas Chandler,
Department of Oral Rehabilitation, School of Dentistry, Uni-
versity of Otago, P.O. Box 647, Dunedin 9054, New Zealand
(Tel.: 0064 3 479 7124; fax: 0064 3 479 5079; e-mail:
doi:10.1111/j.1365-2591.2009.01630.x
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 41–46, 2010 41
similar age, and to relate this to the restorations present
and to pulp chamber dimensions on radiographs.
Materials and methods
Ethical approval was granted by the Otago Ethics
Committee. An examination of the bitewing radio-
graphs of 275 dental students was carried out to screen
for appropriate combinations of healthy and restored
maxillary and mandibular first molar teeth. The
bitewings were available and none were taken for the
study. The images were all taken with the same X-ray
machine (Source 1, Belmont Co., Osaka, Japan:
70 kVp, 10 mA) using E speed film (Kodak Co.,
Rochester, NY, USA) held in a Rinn bitewing holder/
beam alignment device (Dentsply Rinn, Weybridge, UK)
and film processing was automatic (All-Pro 2000M,
Hicksville, NY, USA). Seventy-four individuals had
radiographs which indicated suitable dentitions and
they gave their written informed consent for investiga-
tion of PBF. The subjects were examined clinically.
Their first molars were caries and symptom-free and
there was no history of operative dental work, ortho-
dontics or trauma in the previous 6 months. Restora-
tions were recorded and their radiographic appearances
verified; none of the teeth had carious lesions. There
were two groups:
Group A. Unrestored teeth were compared with
contralateral restored teeth (Fig. 1). The 43 subjects
were 26 females and 17 males with a mean age of
22 years 0 months (range 19 years 0 month to
24 years 7 months). The teeth were 19 maxillary
and 24 mandibular first molars. Twenty-eight of the
restored teeth had single or multiple occlusal restora-
tions. Four teeth had both occlusal and buccal
restorations. Eleven teeth had mesio-occlusal (MO) or
disto-occlusal (DO) restorations, with two having a
buccal extension or separate buccal restoration.
Group B. Teeth with small and large restorations
were compared (Fig. 2). Restoration size was related to
the numbers of restored tooth surfaces, otherwise this
judgement was more subjective. Many small restora-
tions seen on radiographs during the screening
process proved to be extensive when the subjects
were examined clinically. Similarly, several very
extensive composite resin overlays were found that
were nearly invisible on the bitewings. The 31
subjects were 23 females and 8 males with a mean
age of 21 years 4 months (range 19 years 10 months
to 25 years 2 months). There were 16 maxillary and
15 mandibular first molars. Two teeth had buccal
restorations and two had occlusopalatal restorations.
One tooth had an occlusobuccal restoration, and there
were four teeth with small DO restorations. In the
group of heavily restored contralateral teeth were six
large or multiple occlusal restorations and 25 teeth
with either an MO, a DO or a mesio-occlusal-distal
restoration. One of these proximally restored teeth was
overlaid and three of these teeth also had restored
buccal surfaces.
The teeth were tested with an electric pulp tester
(Vitality Scanner Model 2001; Analytic Technology,
Redmond, WA, USA) with the probe tip on the
mesiobuccal cusp tip whenever possible (Lin et al.
2007). All the subjects gave unambiguous positive
responses for both teeth under investigation; as dental
students, they had a good understanding of electric
testing and responses to the stimuli so further pulp tests
were considered unnecessary. From the dental history,
clinical examination and radiological evidence avail-
able all the pulps were considered healthy. A laser
Doppler blood flow monitor (MBF3-D, Moor Instru-
ments, Axminster, UK) was used to display and store
(a)
(b)
Figure 1 Group A; example of unrestored (a) and restored (b)
contralateral mandibular first molar teeth.
Blood flow in restored molars Chandler et al.
International Endodontic Journal, 43, 41–46, 2010 ª 2009 International Endodontic Journal42
PBF signals from the teeth. The laser probe (Moor P5a,
Axminster, UK) was positioned 2 mm from the gingival
margin of the teeth (Roebuck et al. 2000) on the mid-
buccal surface using a splint made of a dark brown
silicone putty (President, Coltene AG, Altstatten, Swit-
zerland). This stabilized the probe and excluded light.
The same probe was used throughout the experiment
and regularly recalibrated. For the small number of
teeth featuring restorative material on the buccal
surface a site to the mesial was adopted for both teeth
in that individual. Two subjects had discrete opaque
hypoplastic regions of buccal enamel which were also
avoided. An accurate, clean hole was cut in the putty
to support the probe using a 1.5 mm dermal biopsy
punch (Miltex, Bethpage, NY, USA). The subjects lay
supine for 10 min in a quiet, draft-free room and then a
resting PBF trace was recorded at 20 Hz for 3 min for
each tooth. All the teeth provided clearly pulsatile
traces at heart beat frequency (Fig. 3). The mean flux
(PBF, machine units) was calculated for each trace by
the flowmeter’s processor.
The radiographs were code numbered and scanned
(DSR-1000 scanner; Electromedical Systems, Nyon,
Switzerland) and pulp measurements were made on a
desktop computer by a single operator using the Scion
Image Program (Scion Corp., Frederick, MD, USA). A
calibration radiograph of a measuring grid with 1 mm
squares (PHIL-X Grid; Medidenta International, Wood-
side, NY, USA) was also made and scanned. Prior to
measurement three pilot studies involving linear and
area assessments of bitewings were performed. These
revealed a high correlation of repeat measurements by
the operator (r = 0.90, 0.92 and 0.92 respectively)
with a regression slope not significantly different to 1.0.
For each tooth a line was drawn across the image
between the mesial and distal enamel-cementum mar-
gins, the area above this being termed the clinical
crown. Two areas were measured, the total pulp
chamber area (above a line across the most superior
part of the pulpal floor) and the pulp chamber area in
the clinical crown. The pulp chamber width at the
cervix and the heights of the mesial and distal pulp
horns (from the enamel-cementum line) were also
measured (Fig. 4).
Following the PBF recordings the radiograph codes
were broken and the data matched for each tooth.
Statistical significance was determined using Student’s
t-test (2-tailed in related samples).
Results
Means and standard deviations of the pulp chamber
measurements and PBF values are shown for group A
in Table 1 and for group B in Table 2.
In group A the presence of restorations was associ-
ated with a significant reduction of total pulp chamber
area, pulp chamber area in the clinical crown, mesial
pulp horn height and PBF (P-values all <0.05,
(a)
(b)
Figure 2 Group B; example of contralateral mandibular first
molar teeth with small (a) and large (b) restorations, in this
patient gold inlays.
Figure 3 Pulpal blood flow trace as seen on flowmeter screen.
Chandler et al. Blood flow in restored molars
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 41–46, 2010 43
Table 1). In group B the presence of large restorations
was associated with a significant reduction in total pulp
chamber area, pulp chamber width at the cervix and
PBF compared with teeth with smaller restorations
(P-values all <0.05, Table 2).
In group A the maxillary teeth revealed a significant
reduction in PBF (P = 0.008). In group B both the
maxillary and mandibular teeth demonstrated reduc-
tions in PBF, with this change more pronounced in the
maxillary teeth (P-values 0.003 and 0.047).
Discussion
Previous blood flow studies have made use of radio-
graphs when available (Odor et al. 1994a,b, Premdas &
Pitt Ford 1995). Other workers have taken radiographs
to determine that the pulp chamber of the tooth was
visible and that the periapical condition was normal
(Hartmann et al. 1996). The present study is unique in
including radiographic measurements alongside PBF
data. Radiographs had already been taken; ethical
approval would not have been granted to take radio-
graphs purely for the experiment. Digitization allowed
accurate measuring of magnified images of the pulp
spaces. The images and their measurements were not
available to the clinical researcher when the PBF
recordings were made. This was a deliberate aspect of
the experimental design in order to avoid bias. Had
radiographs been observed it might have been possible
to direct the LDF probe towards a maximal region of
pulp in an attempt to achieve stronger PBF signals.
Undergraduate students provided a group with a
narrow age range to reduce major variation due to
dentine deposition (Woods et al. 1990) and the
decrease in pulp chamber size (Ketterl 1983) and PBF
(Ikawa et al. 2003), which accompany increasing age.
A maximum of 6 months elapsed between taking
radiographs and recording PBF, with most readings
made within a few weeks.
There are few LDF studies of molars, and no
consensus on optimum probe positions. In studies of
local anaesthesia on mandibular first molars the probes
were positioned on the mid-buccal surfaces of the teeth
(Odor et al. 1994a,b).
Laser flowmetry studies of maxillary incisors reveals
an increase in PBF signal as probes are moved from
incisal to gingival (Ramsay et al. 1991, Ingolfsson et al.
1994, Hartmann et al. 1996). This could be due to a
larger volume of tissue being sampled as the probe is
Figure 4 Diagram of measurements made from radiographs.
(1) Total pulp area (area above a line drawn across the most
superior part of the pulpal floor). (2) Pulp area in the clinical
crown (area above a line drawn between mesial and distal
enamel-cementum junctions). (3) Pulp width at cervix
(between mesial and distal enamel-cementum junctions). (4)
Mesial horn height (above a line drawn between mesial and
distal enamel-cementum junctions). (5) Distal horn height
(above a line drawn between mesial and distal enamel-
cementum junctions).
Table 1 Group A. Mean pulp
dimensions and PBF for unrestored and
restored first molars (standard deviations
in parentheses)
Unrestored (n = 43) Restored (n = 43) t-test P-value
Total pulp area (mm2) 8.92 (2.59) 8.32 (2.55) 0.039*
Pulp area clinical crown (mm2) 3.41 (1.58) 2.89 (1.66) 0.021*
Pulp width at cervix (mm) 3.67 (0.71) 3.40 (1.15) 0.075
Mesial horn height (mm) 1.57 (0.57) 1.34 (0.58) 0.012*
Distal horn height (mm) 0.99 (0.47) 0.90 (0.46) 0.200
PBF (machine units) 98 (47) 83 (46) 0.028*
PBF, pulpal blood flow.
*Significant at the 0.05 level.
Blood flow in restored molars Chandler et al.
International Endodontic Journal, 43, 41–46, 2010 ª 2009 International Endodontic Journal44
moved apically. No data on this effect in molar teeth
have been published.
It has been shown that light from an LDF probe
placed 2 mm above the buccal enamel-cementum
junction in molars is transmitted apically towards the
radicular pulp (Odor et al. 1996). It should therefore be
possible to use LDF to investigate the health of molar
pulps which have diminished size or are situated
unusually deeply.
The pulp chamber width at the cervix of mandibular
first molar teeth is significantly larger than for maxil-
lary teeth (Chandler et al. 2003). A significant decrease
in pulp chamber width was found in group B, and this
may have a role in the success of LDF if an optimal
probe position cannot be achieved. A study of maxillary
central incisors found PBF measurements made at
various mesiodistal locations at the same level on the
tooth did not differ (Ramsay et al. 1991). Forty teeth
(38%) in the present study had proximal restorations.
In a previous study, 26% of the teeth had proximal
restorations (Chandler et al. 2003). In keeping with the
present findings, those restorations were also related to
a significant reduction in total pulp chamber area. The
pulp chamber area in the clinical crown was also
smaller amongst the restored teeth.
Most investigations of the dimensions of opposite
pairs of teeth have been done in man (Black 1980). The
differences are small and probably because of complex
genetic and environmental factors and known as
fluctuating asymmetry. Despite radiographic standard-
ization, minor changes in film position and beam
geometry across the jaws are likely in the present
study, together with anatomical variations such as
tooth rotation. Fluctuating asymmetry of the pulp
space has not been reported; the variations in PBF
signals were in any event much larger. Data may have
been recorded from the gingival crest (Vongsavan &
Matthews 1996) and it is assumed this was comparable
on both sides of the mouth. There appears to be no
published data on differences in blood perfusion on
different sides of the jaws, or LDF studies which
compare signal strengths between healthy maxillary
and mandibular first molars. In radiographic studies
pulp horn location is more reliable in mandibular
molars with bitewings, with the mesiolingual horn
responsible for clarity of the image and longer than that
of the mesiobuccal horn of maxillary teeth (Kandemir
1998, Chandler et al. 2003). The maxillary first molar
has the largest pulp chamber volume of human teeth,
followed by the mandibular first molar; in one study the
difference was 23% (Fanibunda 1986). This difference
in volume may account for the more noticeable
reductions in PBF in maxillary molars in both groups
in the present experiment.
Conclusion
In first molars, the pulp chamber size was influenced by
the presence of restorations. PBF was reduced when
restorations were present. The size and extent of the
restorations had a significant effect on the blood flow
recordings.
References
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19, 36–40.
Table 2 Group B. Mean pulp dimensions
and PBF for first molars with small
restorations and large restorations
(standard deviations in parentheses)
Small restoration
(n = 31)
Large restoration
(n = 31)
t-test
P-value
Total pulp area (mm2) 8.20 (2.47) 7.20 (2.73) 0.003*
Pulp area clinical crown (mm2) 2.43 (1.34) 2.09 (1.43) 0.134
Pulp width at cervix (mm) 3.54 (1.02) 3.19 (1.25) 0.032*
Mesial horn height (mm) 1.19 (0.50) 1.08 (0.60) 0.218
Distal horn height (mm) 0.74 (0.40) 0.63 (0.44) 0.162
PBF (machine units) 102 (55) 73 (44) 0.001*
PBF, pulpal blood flow.
*Significant at the 0.05 level.
Chandler et al. Blood flow in restored molars
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 41–46, 2010 45
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second molar teeth. Journal of Oral Science 40, 143–6.
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attachment apparatus. International Dental Journal 33, 262–
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with an electric pulp tester. Journal of Endodontics 24, 199–
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alveolar nerve block anaesthesia on the lower teeth.
Endodontics and Dental Traumatology 10, 144–8.
Odor TM, Pitt Ford TR, McDonald F (1994b) Adrenaline in
local anaesthesia: the effect of concentration on dental
pulpal circulation and anaesthesia. Endodontics and Dental
Traumatology 10, 167–73.
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effect of wavelength, bandwidth, and probe design and
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Analysis of resin tags formation in root canaldentine: a cross sectional study
Y. Malyk, C. Kaaden, R. Hickel & N. IlieDepartment of Restorative Dentistry and Periodontology, Ludwig-Maximilians University, Munich, Germany
Abstract
Malyk Y, Kaaden C, Hickel R, Ilie N. Analysis of resin tags
formation in root canal dentine: a cross sectional study.
International Endodontic Journal, 43, 47–56, 2010.
Aim To evaluate the length, density and quality of
resin tags formed by penetration of various types of
adhesive systems into dentinal tubules at various cross
section levels of the root canal in correlation to the
density of dentinal tubules.
Methodology Thirty mandibular premolars were
instrumented and fibre posts were inserted with three
different adhesive systems with and without activator:
etch & rinse XP Bond and XP Bond/Self Cure Activator;
self-etch (two-step) AdheSE and AdheSE/AdheSE DC
Activator and self-etch (one-step) Hybrid Bond and
Hybrid Bond/Hybrid Brushes. The resin tags were
evaluated from slices obtained from sections perpen-
dicular to the long axis of the teeth at 3, 6, and 9mm
from the root apex under a Confocal Laser Scanning
microscope.
Results In all groups, lack of continuity of resin tag
length, density and quality was observed not only
from the cervical to the apical region of each root
canal, but also in a mesio-distal direction to the long
axis of the root. Application of etch & rinse adhesive
in contrast to the self-etch adhesives provided the
formation of the shorter, but considerably denser,
more homogeneous and not interrupted resin
tags with similar length. Use of the activator for all
types of adhesives significantly increased the com-
pleteness (P=0.014) and continuity (P=0.024) of
resin tags.
Conclusions None of the investigated adhesives
were able to completely infiltrate the dentinal tubules
in the entire root canal. Use of the etch & rinse adhesive
system and the activators significantly increased the
density and the quality of resin tags.
Keywords: adhesive systems, confocal laser scanning
microscopy, resin tags, root canal dentine.
Received 3 February 2009; accepted 5 August 2009
Introduction
The bonding principle of dental adhesives is based on
the formation of a hybrid layer (Nakabayashi et al.
1991) as well as the penetration of adhesive into
dentine tubules and the formation of ‘resin tags’ (Titley
et al. 1995, Ferrari & Davidson 1996). Adaptation of
adhesive systems for fibre post bonding in root canal is
an attractive clinical concept, but its implementation is
controversial for several reasons: influence of the end-
odontic procedure, polymerization shrinkage (Feilzer
et al. 1993, Carvalho et al. 1996), unfavourable cavity
configuration factor (C-Factor) (Carvalho et al. 1996,
Tay et al. 2005), poor control of moisture (Bouillaguet
et al. 2003) or polymerization difficulties in the apical
regions (Roberts et al. 2004).
So far there are no conclusive and specific reports on
the importance of the resin tags in the quality of the
bond. While some authors measured a higher bond
strength in the coronal section of the root canal
because of the higher density of dentinal tubules and
the longer resin tags formed in this area (Patierno et al.
1996, Kurtz et al. 2003, Mallmann et al. 2005), other
authors found no correlation between bond strength
Correspondence: Yuriy Malyk, Department of Restorative
Dentistry and Periodontology, Ludwig-Maximilians University,
Goethe st. 70, 80336, Munich, Germany (Tel.:
+498951609337; fax: +498951509302; e-mail: ymalyk@
dent.med-uni.muenchen.de).
doi:10.1111/j.1365-2591.2009.01631.x
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 47–56, 2010 47
and resin penetration into dentinal tubules (Tay &
Pashley 2001, Kremeier et al. 2008). Duret et al.
(1990) and Pegoretti et al. (2002) noted that the
resultant homogeneous biomechanical unit allows a
more uniform stress distribution, which better pre-
serves the weakened tooth structure and reduces
microleakage at the dentine-cement interface as well
as reinfection of the peri-apical area (Bachicha et al.
1998, Reid et al. 2003).
Currently, various types of adhesives systems that
either follow an etch & rinse or self-etch approach, can
be used to bond fibre posts into root canals. Previous
studies showed that self-etching primers are more
advantageous for bonding of fibre posts, since they
contain a high concentration of acidic monomers that
demineralize the substrate, that acid does not need to
be removed with water, and the bond forms simulta-
neously to dentine (Yoshiyama et al. 1998, Tay et al.
2003). A recently published investigation showed that
bond strength was not influenced by the demineraliza-
tion of root canal dentine neither with phosphoric acid
nor with self-etching systems, but was affected by the
luting agent and the region of the root canal (Bitter
et al. 2006). As the number of tubules decreases from
the crown to the apex (Carrigan et al. 1984), the
response to acid etching and, consequently, dentine
bonding can vary among different areas of the same
root canal (Ferrari et al. 2000a). The application of
adhesive systems in the root canal usually shows a
non-uniform resin tag formation with consequent
decrease of retention towards the apex (Ferrari &
Mannocci 2000, Mannocci et al. 2004).
Although bonding to the root dentine wall has made
undeniable progress in recent years, the loss of adhe-
sion at the adhesive/root dentine interface is still the
main reason for leakage (Ferrari et al. 1994, Ferrari &
Davidson 1996), decrease in bond strength (Bouillag-
uet et al. 2003, Bolhuis et al. 2005) and hence, failure
of restorations (Ferrari et al. 2000b, Bouillaguet et al.
2003, Mannocci et al. 2003). To decrease these neg-
ative influences, some manufactures recommend the
use of an activator, which triggers the self-curing
reaction of the adhesives, to produce an additional set
that should improve the bonding to root canal walls.
On the basis of this consideration the aim of this study
was to analyze the resin tags formed by various types of
adhesive systems in relation to the density of dentinal
tubules in the cervical, middle and apical third of the
root canal using Confocal Laser Scanning Microscopy
(CLSM). Three types of adhesive systems were com-
pared in this study: an etch & rinse, a self-etch two-step
and a self-etch one-step system each with and without
addition of self-cure activators. Moreover, the density of
dentinal tubules and the quality of resin tag formation
were recorded. The null hypothesis tested was that both
the type of adhesive system and the morphology of the
dentinal tubules do not affect the formation of the resin
tags.
Material and methods
Thirty extracted human mandibular premolars were
used. The criteria for tooth selection were the presence
of a single root canal, verified radiographically, along
with a fully formed apex and no visible root caries or
fractures, verified by examination with a 3.2· magni-
fying glass.
Each root was separated from the crown with a low-
speed diamond saw (Isomet, Buehler, Lake Bluff, IL,
USA) to obtain a 12mm long specimen. The root canals
were shaped with K- and H-files (Dentsply Maillefer,
Ballaigues, Switzerland) to size 50, 1mm short of the
apex. After each instrument size, the canals were
irrigated with 1mL of 1% sodium hypochlorite (NaOCl).
The teeth were then randomly divided into six
groups (n=5). The roots were enlarged with low-speed
DT Drills sizes 0–3 designated for the respective post
system (VDW, Munich, Germany). The depth of the
post space preparation was 11mm. Irrigation was
performed after change of each drill size with 1mL of
1% NaOCl. Afterwards, the root specimens were
irrigated with 9% EDTA for 1min to remove the smear
layer, and then rinsed for 1min with 0.9% NaCl. The
fibre posts DT Light size 3 (VDW) were shortened to a
length of 15mm with water-cooled diamond rotary
cutting instrument and inserted into the root specimens
using six different adhesive systems. Inserted adhesive
systems: XP Bond (Dentsply DeTrey, Konstanz, Ger-
many), XP Bond/Self Cure Activator (SCA) (Dentsply
DeTrey), AdheSE (Ivoclar Vivadent, Schaan, Lichten-
stein), AdheSE/AdheSE DC Activator (Ivoclar Viva-
dent), Hybrid Bond (Sun Medical, Shiga, Japan) and
Hybrid Bond/Hybrid Brushes (Sun Medical). The fluo-
rescent dye 0.1% Rhodamine B isothiacyanate (RITC)
(Merck, Darmstadt, Germany) was mixed into the
components of the adhesive systems, to highlight the
resin tags under CLSM. The labelled adhesives were
applied into the canal space using microbrush tips for
the cervical and middle third of the canal and paper
points for the apical third. The adhesive systems and
application method in this study are summarized in
Table 1. The dual-cured cement Calibra Esthetic Resin
Analysis of resin tags Malyk et al.
International Endodontic Journal, 43, 47–56, 2010 ª 2010 International Endodontic Journal48
Tab
le1
Th
ea
dh
esiv
esy
stem
sa
nd
ap
pli
cati
on
met
ho
du
sed
inth
isin
ves
tig
ati
on
Gro
up
Ad
hesi
ve
Man
ufa
ctu
reLo
tN
o
Ad
hesi
ve
typ
eB
on
dP
rim
er
Act
ivato
rA
pp
lica
tio
n
1X
PB
on
dD
en
tsp
ly
DeT
rey;
Ko
nst
an
z,
Germ
an
y
0609001329
To
tal-
etc
hC
arb
oxyli
caci
dm
od
ified
dim
eth
acr
yla
te(T
CB
resi
n),
PE
NT
A,
UD
MA
,
TE
GD
MA
,H
EM
A
––
To
tal
etc
hw
ith
34%
ph
osp
ho
ric
aci
dfo
r15s
Wate
rsp
ray,
dry
wit
hair
an
d
pap
er
po
ints
Bo
nd
ap
ply
Exce
ssre
mo
ve
usi
ng
pap
er
po
ints
Lig
ht
cure
for
10s
2X
PB
on
d/
Self
Cu
re
Act
ivato
r
Den
tsp
ly
DeT
rey;
Ko
nst
an
z,
Germ
an
y
060516
To
tal-
etc
hC
arb
oxyli
caci
dm
od
ified
dim
eth
acr
yla
te(T
CB
resi
n),
PE
NT
A,
UD
MA
,
TE
GD
MA
,H
EM
A
–U
DM
A,
HE
MA
,
cata
lyst
,
ph
oto
init
iato
r,
ace
ton
e,
wate
r
To
tal
etc
hw
ith
34%
ph
osp
ho
ric
aci
dfo
r15s
Wate
rsp
ray,
dry
wit
hair
an
d
pap
er
po
ints
Bo
nd
mix
wit
hact
ivato
r
(1:1
)an
dap
ply
3A
dh
eS
E
Pri
mer/
Ad
heS
E
Bo
nd
Ivo
clar
Viv
ad
en
t;
Sch
aan
,
Lic
hte
nst
ein
Pri
mer:
JO
6075
Bo
nd
:
AK
03345
Self
-etc
hH
EM
A,
dim
eth
acr
yla
te,
sili
con
dio
xid
e,
init
iato
rs
Dim
eth
acr
yla
te,
ph
osp
ho
nic
aci
d
acr
yla
te,
wate
r
–P
RIM
ER
ap
ply
for
30s
Dry
wit
hair
an
dp
ap
er
po
ints
Bo
nd
ap
ply
Exce
ssre
mo
ve
usi
ng
pap
er
po
ints
Lig
ht
cure
for
10s
4A
dh
eS
E/
Ad
heS
ED
C
Act
ivato
r
Ivo
clar
Viv
ad
en
t;
Sch
aan
,
Lic
hte
nst
ein
K00997
Self
-etc
hH
EM
A,
dim
eth
acr
yla
te,
sili
con
dio
xid
e,
init
iato
rs
Dim
eth
acr
yla
te,
ph
osp
ho
nic
aci
d
acr
yla
te,
wate
r
Init
iato
rs,
solv
en
ts,
eth
an
ol
Pri
mer
ap
ply
for
30s
Dry
wit
hair
an
dp
ap
er
po
ints
Bo
nd
mix
wit
hact
ivato
r
(1:1
)an
dap
ply
5H
yb
rid
Bo
nd
Su
nM
ed
ical;
Sh
iga,
Jap
an
LF-2
Self
-etc
h
‘on
e-b
ott
le’
4-m
eth
acr
ylo
xyeth
ylt
rim
ell
itate
an
hyd
rid
e
––
Bo
nd
ap
ply
for
20s
Exce
ssre
mo
ve
usi
ng
pap
er
po
ints
Lig
ht
cure
for
10s
6H
yb
rid
Bo
nd
/Hyb
rid
Bru
shes
Su
nM
ed
ical;
Sh
iga,
Jap
an
LF-2
Self
-etc
h
‘on
e-b
ott
le’
4-m
eth
acr
ylo
xyeth
ylt
rim
ell
itate
an
hyd
rid
e
–H
yb
rid
Bru
shes
con
tain
a
bo
nd
ing
pro
mo
ter
Bo
nd
mix
wit
hb
rush
an
d
ap
ply
for
20s
Exce
ssre
mo
ve
usi
ng
pap
er
po
ints
Lig
ht
cure
for
10s
PE
NT
A,
Di-
Pen
taery
trit
ho
l-P
en
ta-A
cryla
te-M
on
op
ho
sp
hate
;U
DM
A,
ure
than
ed
imeth
acr
yla
te;
TE
GD
MA
,tr
ieth
yle
ne
gly
col
dim
eth
acr
yla
te;
HE
MA
,h
yd
roxyeth
yl-
meth
acr
yla
t.
Malyk et al. Analysis of resin tags
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 47–56, 2010 49
Cement (Dentsply DeTrey) was mixed for 20s and
spread onto the surface of the fibre post and into the
root canal with a Lentulo Spiral, as recommended by
manufacture. The posts were inserted into the root
canal and manually held in place throughout the self-
cure set time of 5min. After initial set, the light source
(Freelight 2; 1241mWcm)2; 3M-ESPE, Seefeld, Ger-
many) was placed on the post surface and the resin
luting cement was polymerized for 20s. All procedures
were performed by the same operator.
After storing for 24h at 37�C and 100% humidity
the samples were sectioned in 1mm thin slices at
9mm (cervical), 6mm (middle) and 3mm (apical) from
the root apex with a microtome saw (Leica SP 1600;
Leica, Nussloch, Germany). The slices were then
polished with a series of silicon carbide abrasive
papers (1200, 2400 and 4000 grit) on an automatic
polishing device (Exact 40 CS; Exact Apparatebau,
Norderstedt, Germany). The samples were kept moist
during the study.
CLSM examination
The density, length and quality of resin tags, as well as
the density of dentinal tubules and the amount of non-
infiltrated dentinal tubules were recorded in the cervi-
cal, middle and apical regions of the root canal using
LSM-510 Meta microscope (Carl Zeiss, Jena, Germany)
equipped with a water-immersion objective (Achro-
plan·63/0.95W). Microscopy was performed at four
standardized areas (buccal, lingual, mesial, and distal
to the long axis of the root) of each root slice (Fig. 1).
The visualized layer was selected 10lm below the slice
surface and was 15lm thick (15 images, distance
between images was 1lm). The image size was
150·150lm with resolution of 2656·2924 pixels.
The image analysis and 3D reconstruction were carried
out using LSM Image Browser 4.6 (Carl Zeiss).
The slices were scanned with ‘multitracking’, allow-
ing the simultaneous evaluation of labelled adhesive
and the density of the dentinal tubules. To observe the
RITC labelled adhesive, the 488nm laser line for
excitation (beamsplitter: HFT 405/488) was used, thus
allowing emitted fluorescent light to pass through and
hit the detector (filter: BP 530–560nm). To identify the
dentinal tubules, which were not infiltrated by adhesive
labelled with fluorescent dye a second channel was
added. The reflection mode (excitation 488nm) was
used with a special beam splitter (NT 80/20) and a
long-pass filter with a detection window for the
reflected light (long pass 420nm). In reflection, all
dentinal tubules give a strong and clear signal because
of a change in the optical medium between the dentine
and the medium (distilled water). Counting of dentinal
tubules was performed on images taken on an area
15·100lm. The results were indicated as tubules/
mm2.
Additionally, to determine the quality of resin
penetration into the dentinal tubules, the three factors
of completeness, continuity and evenness of resin tags
were evaluated using the classification system with
scores from 0 to 3 indicating best to worst quality.
Completeness (homogeneity of adhesive penetration
into dentinal tubules): 0=90–100% of the dentinal
tubules were homogenously filled with adhesive;
1=50–90%; 2=10–50%; 3=0–10%.
Continuity (uninterruptedly of the resin tags): 0=90–
100% of resin tags were not interrupted; 1=50–90%;
2=10–50%; 3=0–10%.
Evenness (equability of the resin tags length): 0=90–
100% of resin tags were of equal length; 1=50–90%;
2=10–50%; 3=0–10%.
The general linear model procedure of sas/stat 9.2
Software (SAS Institute, Cary, NC, USA) was used to
quantify the influence of the adhesive and root canal
region on the quality of the adhesive/root dentine
interface (a=0.05). One- and multiple-way anova and
Tukey post hoc tests for the morphology of dentinal
tubules were used (a=0.05).
Results
The results obtained regarding density of resin tags,
dentinal tubules and resin tags length are summarized
1 m
m
Figure 1 Preparation of cross sectional slice. Microscopy was
performed at four standardized areas (buccal, lingual, mesial,
and distal to the long axis of the root) of each root slice.
Analysis of resin tags Malyk et al.
International Endodontic Journal, 43, 47–56, 2010 ª 2010 International Endodontic Journal50
Tab
le2
Den
tin
al
tub
ule
sd
ensi
ty,
resi
nta
gs
len
gth
an
da
mo
un
to
fd
enti
na
ltu
bu
les
no
tp
enet
rate
dw
ith
ad
hes
ive
com
po
nen
ts(m
ean
+S
D)
Po
siti
on
Ad
hesi
ve
syst
em
s
Nu
mb
er
of
den
tin
al
tub
ule
s
(mm
2)
Len
gth
of
resi
nta
gs
(lm
)
Len
gth
of
resi
nta
gs
(bu
ccal,
lm
)
Len
gth
of
resi
nta
gs
(lin
gu
al,
lm
)
Len
gth
of
resi
nta
gs
(mesi
al,
lm
)
Len
gth
of
resi
nta
gs
(dis
tal,
lm
)
No
t
infi
ltra
ted
den
tin
al
tub
ule
sw
ith
ad
hesi
ve
(%)
No
tin
filt
rate
d
den
tin
al
tub
ule
sw
ith
ad
hesi
ve
(bu
ccal,
%)
No
tin
filt
rate
d
den
tin
al
tub
ule
s
wit
had
hesi
ve
(lin
gu
al,
%)
No
tin
filt
rate
d
den
tin
al
tub
ule
s
wit
had
hesi
ve
(mesi
al,
%)
No
tin
filt
rate
d
den
tin
al
tub
ule
sw
ith
ad
hesi
ve
(dis
tal,
%)
Cerv
ival
XP
Bo
nd
37985
(2608)
26.4
(5.3
)a27.0
(7.5
)27.3
(5.9
)22.3
(5.9
)21.5
(3.9
)6.6
3(2
.8)b
6.6
(2.7
)6.4
(2.2
)7.4
(3.5
)7.2
(2.5
)
XP
Bo
nd
/SC
A27.5
(6.8
)a28.1
(6.4
)27.4
(6.5
)22.9
(4.2
)23.8
(7.3
)0.4
(0.2
)a0
00
1.8
(0.4
)
Ad
heS
E93.7
(26.2
)c95.1
(20.0
)92.2
(30.0
)80.6
(38.8
)84.1
(36.0
)9.9
1(4
.8)c
5.2
(3.9
)8.4
(4.6
)9.2
(4.3
)11.3
(10.8
)
Ad
heS
E65.5
(11.2
)b66.1
(11.0
)67.3
(11.0
)65.3
(10.2
)64.6
(12.2
)1.6
(0.7
)a2.2
(1.1
)1.8
(0.7
)2.1
(1.6
)2.0
(0.6
)
HB
79.1
(19.6
)b,c
78.2
(20.8
)81.5
(18.0
)77.8
(16.6
)78.7
(18.2
)2.4
(0.7
)a0
00
6.8
(0.4
)
HB
/Hyb
rid
Bru
shes
152.3
(29.2
)d156.6
(24.8
)152.7
(21.5
)150.2
(27.1
)149.8
(26.1
)0.5
2(0
.2)a
00
1.8
(0.4
)0
Mid
dle
XP
Bo
nd
31028
(3671)
19.5
(4.5
)a20.0
(4.4
)19.4
(4.2
)18.4
(3.9
)18.8
(3.8
)5.6
6(2
.1)b
5.0
(1.6
)4.3
(3.0
)7.7
(2.0
)8.8
(6.2
)
XP
Bo
nd
/SC
A23.6
(5.7
)a24.0
(3.8
)24.0
(6.1
)18.2
(4.0
)20.7
(5.8
)2.8
8(1
.2)a
0.8
(0.4
)1.7
(0.8
)4.8
(2.7
)4.0
(2.9
)
Ad
heS
E76.6
(21.4
)b77.6
(19.0
)82.8
(22.9
)69.1
(17.9
)74.6
(26.8
)5.7
4(2
.7)c
3.8
(3.1
)4.2
(2.5
)6.2
(1.7
)15.0
(11.2
)
Ad
heS
E70.8
(15.2
)b79.6
(14.2
)64.5
(12.3
)61.8
(13.2
)60.8
(13.1
)5.3
6(2
.8)a
,b3.2
(1.6
)3.4
(2.4
)10.2
(6.8
)3.8
(1.6
)
HB
64.6
(12.8
)b65.7
(11.7
)69.1
(14.6
)61.4
(13.7
)62.2
(10.9
)3.6
6(1
.9)a
1.7
(0.8
)0
5.3
(2.4
)4.9
(2.2
)
HB
/Hyb
rid
Bru
shes
101.1
(34.8
)c96.5
(35.4
)95.4
(38.0
)84.0
(29.2
)95.3
(35.5
)1.0
2(0
.4)a
00
3.3
(0.6
)0.9
(0.4
)
Ap
ical
XP
Bo
nd
26042
(2792)
16.1
(3.3
)a15.9
(3.1
)17.0
(3.5
)14.4
(4.7
)13.8
(5.3
)4.4
3(2
.1)b
3.4
(0.8
)3.2
(2.0
)5.0
(1.2
)6.2
(5.2
)
XP
Bo
nd
/SC
A18.9
(6.4
)a19.5
(2.8
)19.6
(12.0
)11.8
(3.2
)12.2
(3.0
)4.1
7(3
.2)a
0(0
)0
(0)
10.2
(9.2
)5.4
(3.2
)
Ad
heS
E19.1
9(1
2.7
)a22.4
(14.2
)18.1
(10.5
)16.3
(12.9
)16.1
(12.8
)7.8
9(3
.2)c
5.8
(1.6
)5.4
(2.1
)9.6
(6.7
)14.4
(9.0
)
Ad
heS
E13.8
(4.7
)a13.4
(2.8
)14.4
(3.1
)11.3
(5.1
)12.2
(2.6
)6.5
5(3
.1)a
,b2.2
(1.7
)2.2
(1.8
)12.5
(11.4
)12.4
(10.2
)
HB
46.2
(10.2
)b47.1
(7.0
)45.4
(6.1
)44.7
(9.1
)42.7
(7.4
)5.4
7(3
.1)a
1.7
(1.1
)1.9
(0.8
)12.2
(8.8
)9.8
(2.7
)
HB
/Hyb
rid
Bru
shes
58.2
(15.6
)c59.6
(16.7
)59.1
(13.9
)54.4
(15.0
)55.7
(16.9
)4.8
8(2
.6)a
02.1
(1.1
)9.5
(3.8
)9.0
(6.6
)
Su
pers
crip
tle
tters
ind
icate
stati
stic
all
yh
om
og
en
eo
us
sub
gro
up
s(a
=0.0
5).
Malyk et al. Analysis of resin tags
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 47–56, 2010 51
in Table 2. The typical bonding morphology between
adhesive systems and root dentine is shown in Fig. 2.
The dentinal tubule density varied depending on the
region examined. In the cervical region the tubule
density was significantly higher (37985 per mm2) than
those observed in the middle (31028 per mm2) and
apical (about 26042 per mm2) thirds. Differences in
dentinal tubule densities between the four standardized
areas (buccal, lingual, mesial and distal) within one
part of a root slice were not significant.
Significant differences of the resin tag length were
found between groups (P<0.001). In all groups also a
discontinuity of resin tag length from cervical to
apical region was observed. The resin tags formed by
Hybrid Bond/Hybrid Brushes (Group 6) were found to
be longer than in the other five groups and consisted
of 152.3lm for the cervical, 101.1lm for the middle
and 58.2lm for the apical thirds. In contrast, the
lengths of resin tags for XP Bond (Group 1) samples
were the shortest and reached lengths of up to
26.4lm, 19.5lm and 16.1lm, accordingly. Bonfer-
roni adjustment indicated significant differences in the
depth of adhesive penetration within the apical and
middle regions of the root canal at four standardized
areas (buccal, lingual, mesial and distal) (P<0.001).
The adhesive penetration was deeper at buccal and
lingual areas to the long axis of the root than at
mesial and distal.
None of the adhesive systems tested was able to
infiltrate and flow inside all the dentinal tubules along
the entire root canal. An increase in non-infiltrated
dentinal tubules from cervical to apical region was
observed for all groups (P<0.001). The lowest numbers
of non-infiltrated dentinal tubules were observed for XP
Bond/SCA (Group 2), Hybrid Bond (Group 5) and
Hybrid Bond/Hybrid Brushes (Group 6). Non-infiltrated
dentinal tubules were significantly more frequently
observed at the mesial and distal areas than at the
buccal and lingual (P=0.04).
The quality of resin penetration into the dentinal
tubules was significantly different between the study
groups (Table 3). A significant reduction in complete-
ness, continuity and evenness of resin tags from the
cervical to the apical region of the root canal for all
adhesive systems tested was observed. The resin tags
formed by XP Bond/SCA (Group 2) were more complete
and even than those of other adhesives. In the cervical
region the dentinal tubules were 100% homogenously
filled with adhesive components, declining to 90% in
the middle and 80% in the apical. The least homoge-
nous adhesive penetration was observed for AdheSE
(Group 3) and consisted 55%, 25% and 0%, accord-
ingly. For all types of adhesive systems the use of an
activator influenced significantly the completeness
(P=0.014) and continuity (P=0.024) of resin tags,
but not the evenness of resin tags.
Discussion
Good quality dentine bonding is obtained when a
continuous hybrid layer forms with regular, dense resin
tags (Mjor & Nordahl 1996, Mannocci et al. 1998). The
current investigation compared resin tags length,
quality and density created by various types of adhesive
systems in relation to the density of dentinal tubules in
root canals under CLSM. Because of the lack of
information regarding the adhesive infiltration in the
apical part of the root canal (Tay et al. 2005) the fibre
post was inserted intentionally 1mm from the working
length to examine the resin tags formation along the
whole root canal wall. The null hypotheses tested in
this study – that the type of adhesive material and the
morphology of the dentinal tubules will not affect the
formation of the resin tags – were both rejected.
(a) (b) (c)
Figure 2 CLSM images of the adhesive/root dentine interface under 63· magnifications in reflection and fluorescence mode: RT –
resin tags, DT – dentinal tubules, RD – root dentine, RC – resin composite. (a) Penetration of the adhesive system AdheSE/AdheSE
DC Activator into the dentinal tubules in the cervical region of the root canal. The adhesive system labelled with RITC appears red
in fluorescent mode. (b) Dentinal tubules appear white in reflection mode. (c) Adhesive/root dentine interface in fluorescent and
reflection mode.
Analysis of resin tags Malyk et al.
International Endodontic Journal, 43, 47–56, 2010 ª 2010 International Endodontic Journal52
The CLS microscopy offers multidimensional access
to different structures of the same sample by staining
them with different markers. In this study, a combina-
tion of the reflection mode with fluorescence markers
allowed 3D-analysis of the adhesive resin penetration
revealing the morphological structure (Fig. 2). For the
visualization of detailed information of the penetration
and distribution of resin tags several advantages of the
confocal technique, compared with SEM imaging were
reported (Bitter et al. 2009). There is no additional
sample preparation necessary, which could cause
shrinking, swelling or similar artefacts by drying or
freezing the sample, as is essential for high resolution
electron microscopy. The RITC used as a fluorochrome
marker in this study is effective in very low concentra-
tions, soluble in water as well as in organic solutions
such as dentine primers (Pioch et al. 1997), moves
freely across the bonded interface, and is stable under
various pH-levels (Sidhu & Watson 1998).
In accordance with the findings of Ferrari & Mann-
occi (2000) and Mjor et al. (2001) who observed
significantly higher density of dentinal tubules in the
cervical third of the root canal than in the middle and
apical thirds, the results of this study revealed decreases
in the density of the dentinal tubules from 37985 per
mm2 in the cervical region to 31028 per mm2 in the
middle and 26042 per mm2 at the apex. Disparity of
dentinal tubule density in four standardized areas
(buccal, lingual, mesial and distal) within one slice of
the root canal was not significant.
The length of resin tags in this study decreased from
cervical to apical within the root canal. The type of
adhesive system significantly affected the resin tags
length (P<0.001). The self-etch adhesive Hybrid Bond/
Hybrid Brushes (one-step) created the deepest penetra-
tion into the dentinal tubules compared with the self-
etch (two-step) and to etch & rinse adhesives. The
deeper penetration of the self-cure adhesive might be
explained not only by dentine conditioning, but also
with material permeability and the conduct of the
adhesive component.
The morphological reasons that can impact on resin
penetration in an apical direction are the diameter of
the dentinal tubules, which are larger cervically than
apically (Marion et al. 1991) as well as sclerotic
processes, that hamper the access to the dentinal
tubules (Mjor 1985, Wang & Weiner 1998). It should
be highlighted that resin tag length was significantly
dependent not only on the root region observed, but
also on the area of observation within one slice. Longer
resin tag formation was observed at buccal and lingual
areas to the long axis than at mesial and distal in the
apical and middle regions of the root canal. It is because
of more prominent intratubular calcifications of the
dentinal tubules in the mesial and distal root directions
compared with buccal and lingual (Paque et al. 2006).
The significant difference in the density of the resin
tags was highly dependent on the type of adhesive
system used (P<0.001) and on the root region
(P<0.001). Numerous resin tags might provide a more
durable bond of the post to the root canal dentine
(Bitter et al. 2004) and prevent leakage (Mannocci
et al. 2001). Conditioning of the root canal dentine
with phosphoric acid revealed considerably more resin
tags than observed after the application of self-etching
adhesives. Lowest numbers of infiltrated dentinal
Table 3 Quality of adhesive penetration into the dentinal tubule (%). Completeness (I), continuity (II) and evenness (III) of resin
tags were evaluated using the classification system with scores from 0 to 3 indicating best to worst quality
Position Scale
XP Bond XP Bond/SCA AdheSE
AdheSE/Acti-
vator Hybrid Bond
Hybrid Bond/
hybrid
brushes
I II III I II III I II III I II III I II III I II III
Cervical 0 40 80 75 100 100 85 55 35 0 80 70 5 5 5 0 10 80 0
1 50 10 25 0 0 10 40 60 40 20 30 90 65 80 45 80 20 80
2 10 10 0 0 0 5 5 5 60 0 0 5 30 15 55 10 0 20
3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Middle 0 25 70 60 90 90 65 25 5 0 80 30 80 0 0 0 5 40 0
1 65 20 30 10 10 20 30 30 50 15 65 15 30 70 30 45 55 45
2 10 10 10 0 0 15 30 50 55 5 5 5 70 30 70 50 5 55
3 0 0 0 0 0 0 15 15 5 0 0 0 0 0 0 0 0 0
Apical 0 5 20 70 90 80 75 0 0 0 65 50 65 0 0 0 0 30 0
1 45 55 15 10 20 15 50 15 0 15 30 25 20 55 5 65 60 15
2 40 20 10 0 0 10 40 70 90 20 20 10 75 40 90 35 10 85
3 10 5 5 0 0 0 10 15 10 0 0 0 5 5 5 0 0 0
Malyk et al. Analysis of resin tags
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 47–56, 2010 53
tubules for the self-etch (two-step) adhesive AdheSE,
when compared with etch & rinse XP Bond adhesive
were observed. The reason for this might be that the
multiple-stage adhesive system was able to produce a
more uniform and thick resin-dentine interdiffusion
zone than the self-etching primer (Bitter et al. 2004). In
the apical region, the amount of dentinal tubules that
were not infiltrated with adhesive was more frequent
than in the cervical region. Just like resin tag length,
non-infiltrated dentinal tubules were more frequently
observed at mesial and distal areas than at buccal and
lingual.
The completeness of resin infiltration into dentinal
tubules is responsible for the long-term monomer/
dentine strength and stability (Zicari et al. 2008). In
this study, significant differences were found in the
qualitative evaluation of the resin tags by scores with
reference to the root region, area of observation and
adhesive type (Fig. 3). Despite the deepest penetrations
of Hybrid Bond, the interaction of this adhesive system
with the wall of dentinal tubule was irregular: the
dentinal tubules were incompletely infiltrated and often
interrupted. Only 5% of the dentinal tubules were
infiltrated completely when using Hybrid Bond in the
cervical region, declining to none in the apical region.
The worst completeness and continuity of the resin tags
with various lengths was recorded in the specimens in
which self-etch adhesive AdheSE was applied. The
self-etch (two-step) adhesive AdheSE Primer is charac-
terized by less acidity (pH=1.7), compared with the
self-etch (one-step) Hybrid Bond (pH=1.0). Therefore,
the acidic monomers of the self-etch AdheSE Primer
may not solubilize enough mineral to achieve homog-
enous resin penetration. In addition, the mineral
components from the smear layer may neutralize the
acidity of these self-etch systems (Tay & Pashley 2001).
Non and/or insufficiently resin infiltrated dentinal
tubules may cause the passage of fluids whereas
homogenous resin tags might be responsible for a tight
seal. Application of the conventional adhesive XP
Bond/SCA after dentine etching provided mainly for-
mation of homogeneous and complete tags of similar
length. This was probably caused by the etching effect
that dissolved the smear layer, thus allowing better
access and complete filling of dentinal tubule by the
monomers of the etch & rinse adhesive. Use of the
activator for all types of adhesives significantly
increased the completeness and continuity of resin tags
(P=0.014). A better quality of resin penetration was
observed at buccal and lingual areas to the long root
axis than at mesial and distal.
It has to be considered that bonding to root canal
dentine might be hampered by a lack of direct vision
and luting agent application techniques (D’Arcangelo
et al. 2008). In this study, poorer tag formation in the
apical third might be due to the fact that conditioning
with a microbrush would be better in the cervical
region whereas in the apical third the contact and fluid
exchange with paper cones might be reduced, resulting
in resin penetration less deeply into the tubules. These
findings agree with the results of Ferrari et al. (2002),
who reported that the microbrush promoted a higher
number of resin tags.
Conclusion
The application of the etch & rinse adhesive system
resulted in shorter, but more dense and more complete
resin tags compared with the two- or one-step self-etch
adhesives. There was a significant difference in resin
(a) (b) (c)
Figure 3 CLSM images of the resin tags formed by various types of adhesive systems in root canal under 63·magnification in
fluorescence mode: RT – resin tags, RD – root dentine, HL – hybrid layer, RC – resin composite. (a) Penetration of the adhesive
system Hybrid Bond into the dentinal tubules in the cervical region of the root canal. The resin tags are not homogenously, often
interrupted and not of equal length. (b) Penetration of the adhesive system AdheSE into the dentinal tubules in the middle region of
the root canal. The resin tags have an equal length, are continuous but not homogenous. (c) Penetration of the adhesive system
XP Bond into the dentinal tubules in the apical region of the root canal. The resin tags are not completeness but equal length.
Analysis of resin tags Malyk et al.
International Endodontic Journal, 43, 47–56, 2010 ª 2010 International Endodontic Journal54
tags formation not only among different regions of the
root canal (cervical, middle and apical), but also in the
direction of dentinal tubules (buccal, lingual, mesial
and distal to the long axis of the root). Use of the
activator for all types of adhesive systems significantly
increased density and quality of resin tags. The clinical
importance of the length of resin tags and/or their
quality in relation to bonding should be further
investigated.
Acknowledgements
The authors would like to thank Prof. Matthias
Folwazcny for permitting the use of the CLS micro-
scope, Dr. Jan-Erik Heil for CLSM technical support and
Dr. Alexander Crispin from IBE for statistical analysis.
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Haemostatic effect and tissue reactions ofmethods and agents used for haemorrhagecontrol in apical surgery
S. S. Jensen1,2, P. M. Yazdi3, E. Hjørting-Hansen1,4, D. D. Bosshardt1 & T. von Arx1
1Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland; 2Department of
Oral & Maxillofacial Surgery, Copenhagen University Hospital, Glostrup, Denmark; 3Department of Oral & Maxillofacial Surgery,
School of Dental Medicine, University of Arhus, Arhus, Denmark; and 4Department of Oral & Maxillofacial Surgery, School of
Dentistry, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
Summary
Jensen SS, Yazdi PM, Hjørting-Hansen E, Bosshardt DD,
von Arx T. Haemostatic effect and tissue reactions of methods
and agents used for haemorrhage control in apical surgery.
International Endodontic Journal, 43, 57–63, 2010.
Aim To compare the haemostatic effect and tissue
reactions of different agents and methods used for
haemorrhage control in apical surgery.
Methodology Six standardized bone defects were
prepared in the calvaria of six Burgundy rabbits. Five
haemostatic modalities were tested for their haemo-
static effect and tissue reactions, and were compared
with untreated control defects: ExpasylTM + Stasis�,
ExpasylTM + Stasis� + freshening of the bone defect
with a bur, Spongostan�, Spongostan� + epinephrine,
and electro cauterization. The haemostatic effect was
analysed visually and compared using Wilcoxon’s
signed rank test. Two groups of three animals were
evaluated histologically for hard and soft tissue reac-
tions related to the different haemostatic measures,
after 3 and 12 weeks of healing respectively.
Results ExpasylTM + Stasis� and electro cauteriza-
tion proved most effective in reducing bleeding
(P < 0.05), but were accompanied by unfavourable
tissue reactions, as indicated by the presence of necrotic
bone, inflammatory cells and the absence of bone
repair. These adverse tissue reactions did not recover
substantially over time. However, adverse reactions
were not observed when the superficial layer of bone
had been removed with a rotary instrument. In
contrast, Spongostan� + epinephrine showed only a
moderate haemostatic effect, but elicited also only mild
adverse tissue reactions.
Conclusions Haemostasis in experimental bone
defects is most effectively accomplished by using
ExpasylTM + Stasis� or electro cauterization. However,
the bone defects should be freshened with a rotary
instrument before suturing so as not to compromise
healing.
Keywords: animal study, apical surgery, haemor-
rhage control, haemostatic agent.
Received 15 July 2009; accepted 25 August 2009
Introduction
Haemorrhage control is important in apical surgery to
facilitate inspection of the root-end surface and to allow
placement and setting of the root-end filling. Usually,
one or more local agents are needed to achieve
sufficient haemostasis. These agents should be either
removed completely or should be fully biocompatible
and degrade without interfering with periapical healing.
The haemostatic effect and tissue reactions of bone
wax, ferric sulphate (Stasis�, Belport Co, Camarillo, CA,
USA), and an aluminium chloride-containing paste
(ExpasylTM, Pierre Rolland, Merignac, France) intended
for application into the sulcus prior to impression-taking
has been reported (von Arx et al. 2006). The combina-
tion of Stasis� and ExpasylTM or ExpasylTM alone proved
most efficient in controlling haemorrhage. However,
their use was accompanied by an inflammatory and a
Correspondence: Dr Simon Storgard Jensen, Department of
Oral & Maxillofacial Surgery, Copenhagen University Hospital
Glostrup, Ndr. Ringvej, DK-2600 Glostrup, Denmark (Tel.:
+45 43 23 32 08; fax: +45 43 23 39 63; e-mail:
doi:10.1111/j.1365-2591.2009.01637.x
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 57–63, 2010 57
foreign body tissue reaction at the histological level.
Based on these findings, the clinical use of ExpasylTM has
been modified to include freshening the bony surface of
the periapical crypt with a bur after placement and
initial setting of the root-end filling material.
Resorbable gelatin-based sponges, such as Spongo-
stan�, Spongostan�, Dental, Johnson & Johnson
medical Ltd., Ascot, UK, are frequently used for
haemostasis in several surgical specialties (Petersen
et al. 1984, Finn et al. 1992, Schonauer et al. 2004).
Spongostan� can be used alone, but is often combined
with a vasoconstrictor to enhance the haemostatic
effect (Rud et al. 2001). Tissue reactions to Spongo-
stan� are generally considered to be mild (Alpaslan
et al. 1997). However, when Spongostan� is left inside
osseous defects, delayed healing has been reported
(Liening et al. 1997, Schonauer et al. 2004). It is not
known how the tissue reacts if the gelatin sponge is
removed after haemorrhage control has been
achieved.
Electro cauterization is an effective method for
producing haemostasis by coagulation and vesicular
clumping. Most often, electro cauterization is used to
stop localized bleeding in the soft tissues, but it has also
been reported to be efficient when used on oozing bone
surfaces (Jensen et al. 2002). With this approach, no
foreign substance is introduced into the bony crypt.
However, concern has been raised about the influence
on healing due to the thermal damage to the bone
tissue (Eriksson et al. 1982).
The purpose of the present study was twofold:
• To compare the haemostatic effects of ExpasylTM +
Stasis�, Spongostan�, Spongostan� + epinephrine and
electro cauterization in standardized bone defects.
• To evaluate the tissue reactions after using Expa-
sylTM + Stasis� with and without freshening of the
bone defect with a bur, after electro cauterization, and
after using Spongostan� alone or in combination with
epinephrine.
Material and methods
Study design
Approval to perform the study was granted by the
authorities of the Canton of Bern, Department of
Agriculture, Section Veterinary Service, Experimental
Animal Studies (study number 100/06). The experi-
mental study was conducted in six adult Burgundy
rabbits, each at least 5 months old and weighing
between 3 and 4.5 kg.
The surgical procedures were performed under intra-
venous general anaesthesia using the medication and
surgical protocol presented by von Arx et al. (2006).
In each rabbit, six standardized monocortical bone
defects were created in the calvarium. The defects were
prepared using a trephine with an outer diameter of
4 mm. The depth of the defects depended on the
thickness of the outer cortical bone layer. Each defect
then received one of the following treatments in a
randomized sequence (Fig. 1), with a randomization
scheme generated using http://www.randomiza-
tion.com (seed: 2604):
• Control: no haemostatic agent was placed.
• ExpasylTM and Stasis�: ExpasylTM (Pierre Rolland,
Merignac, France) was placed into the bone defect with
a spatula, flush with the adjacent outer cortex; after
2 min the paste was removed with a dental curette.
(a) (c)(b)
Figure 1 a) Standardized monocortical bone defects in the rabbit calvarium before application of haemostatic agents. Example of
photograph used for visual assessment of initial bleeding score. b) Schematic illustrations used for visual assessment of bleeding. c)
Presentation after application of haemostatic agents. Example of photograph used for visual assessment of final bleeding score.
Haemostasis in apical surgery Jensen et al.
International Endodontic Journal, 43, 57–63, 2010 ª 2010 International Endodontic Journal58
Subsequently, a small sponge soaked with Stasis�
(Belport Co, Camarillo, CA, USA) was placed for 5 s
into the bone defect.
• ExpasylTM and Stasis� with freshening of the bone
defect: ExpasylTM and Stasis� were applied as described
above. Before primary closure, the bone defect was
freshened using a small round bur (Ø: 1.2 mm) under
copious saline irrigation to remove all macroscopically
visible remnants of ExpasylTM.
• Spongostan�: A Spongostan� sponge, 1 cm3
(Spongostan� Dental; Johnson & Johnson Medical Ltd.,
Ascot, UK) was compressed into the defect for 2 min
using a gauze tampon, and then removed.
• Spongostan� and epinephrine: A Spongostan�
sponge 1 cm3 was soaked in three drops of epinephrine
1%, compressed into the defect for 2 min using a gauze
tampon, and then removed.
• Electro cauterization: Any visible bleeding within the
defect was cauterized using a spatula-shaped cauteriza-
tion head (straight, 2.35 · 19 mm) (ERBOTOM ICC,
ERBE Swiss AG, Winterthur, Switzerland. Setting: Soft
coagulation 60 Watt). Before primary closure, the defect
was curetted using a surgical spoon.
Sacrifice
One group of three animals was allowed to heal for
3 weeks, and a second group of three animals for
12 weeks. Following each designated healing period,
sacrifice was performed as previously described (von
Arx et al. 2006). The retrieved calvarial specimens
were immediately immersed in a solution of 4%
formaldehyde and 1% calcium chloride.
Histological analysis
The non-decalcified specimens were embedded in
methyl-methacrylate and stained with combined basic
fuchsin and toluidine blue. Transversal sections with a
thickness of approximately 80 lm were obtained for
descriptive histology (Schenk et al. 1984). The histo-
logic examination for the description of qualitative
tissue reactions included absence or presence of (i)
remnants of anticoagulation agents; (ii) new bone; (iii)
necrotic bone; (iv) an inflammatory cell infiltrate; and
(v) multinucleated giant cells.
Visual analysis of haemostatic effect
Photos were taken before application and after removal
of the haemostatic agents (Fig. 1). The amount of blood
per site was assessed on a scale from 0 (completely dry
defect) to 7 (profuse bleeding from the defect) (von Arx
et al. 2006). Three evaluators independently examined
the photos and determined the bleeding score per site. A
mean bleeding score was calculated per treatment for the
different sites before application (=initial score) and after
removal (=final score) of the haemostatic agents. The
difference between the two means determined the mean
haemostatic effect per agent (reduction of bleeding).
Statistics
The results of the visual analysis of haemostatic effect
were compared using Wilcoxon’s signed rank test for
paired samples. Exact two-sided P-values were com-
puted to detect differences between the various treat-
ment options. As pair wise comparisons were
completed on the same data, the P-values would have
needed to be adjusted to compensate for the multiple
testing situation. However, because of the explorative
nature of the study and the small sample size, no
adjustment was carried out. Cohen’s weighted kappa
values were calculated to evaluate inter-observer vari-
ations (Fleiss & Cohen 1973).
Results
One animal in the 12-week group died immediately
postoperatively because of an anaesthetic complication.
An additional animal was therefore included, resulting
in seven animals being included in the visual evalua-
tion of the haemostatic effect. Another animal in the
12-week group died 7 weeks postoperatively. The
calvarium of this animal was evaluated histologically
and was found to demonstrate tissue reactions compa-
rable to the two remaining animals in the 12-week
group. This animal was therefore included in the
qualitative histologic evaluation.
Haemostatic effect
In the visual quantification of the bleeding, there was
strong agreement between the three observers
(weighted kappa values: 0.71 to 0.98) (Fleiss & Cohen
1973). The initial bleeding scores, final bleeding scores,
and reduction of bleeding for the individual test groups
are presented in Table 1. Pair wise comparisons of the
different test groups regarding final bleeding score and
bleeding reduction are given in Tables 2 and 3.
No significant differences were found between the
initial mean bleeding scores for the different treatment
Jensen et al. Haemostasis in apical surgery
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 57–63, 2010 59
modalities (P between 0.14 and 1.00). The mean final
bleeding score was significantly smaller final than
the ‘control’ for all groups except ‘Spongostan�’
(P = 0.798). ‘ExpasylTM + Stasis�’ and ‘ExpasylTM +
Stasis� + freshening’ both had significantly smaller
mean bleeding scores than ‘Spongostan�’ and ‘Spongo-
stan� + epinephrine’ (P < 0.05). ‘Electro cauterization’
exhibited borderline significantly smaller final mean
bleeding scores than ‘Spongostan�’ and ‘Spongostan� +
epinephrine’ (P = 0.059 and P = 0.051, respectively).
With regard to the mean bleeding reduction scores, all
but the two ‘Spongostan�’ groups (P = 0.866 and
P = 0.295, respectively) demonstrated significantly
higher bleeding reduction than the control defects
(P < 0.05). ‘ExpasylTM + Stasis�’ showed borderline
significantly higher bleeding reduction than ‘Spongo-
stan�’ (P = 0.050). ‘ExpasylTM + Stasis� + freshening’
reduced the bleeding significantly more than ‘Spongo-
stan�’ (P = 0.031) and borderline significantly more
than ‘Spongostan� + epinephrine’ (P = 0.051). Electro
cauterization resulted in significantly higher bleeding
reduction than ‘Spongostan�’ (P = 0.034).
Histology
No attempt was made to preserve the volume of the
original bone defects by covering them with a barrier
membrane. Therefore, herniation of soft tissues into the
defects was a frequent finding, irrespective of the
haemostatic agent applied (Fig. 2).
Control sites
3 Weeks: Vivid bone formation was observed extending
from the defect walls. Ongoing osteogenic activity was
observed throughout the defects with woven bone
trabeculae with osteoblastic seams.
12 Weeks: Maturation of the newly formed bone was
generally observed (Fig. 2). However, pressure from the
covering soft tissue caused surface resorption of some of
the newly formed bone.
Table 1 Mean bleeding scores ( ± SD)
before application and after removal of
haemostatic agents, and mean reduc-
tion in bleeding scores (n = 7)
Mean initial
score ( ± SD)
Mean final
score ( ± SD)
Mean
reduction ( ± SD)
Control 3.81 ( ± 1.68) 3.33 ( ± 1.60) 0.48 ( ± 1.87)
ExpasylTM + Stasis� 3.24 ( ± 0.83) 0.43 ( ± 0.29) 2.81 ( ± 0.71)
ExpasylTM + Stasis� +
freshening of defect
4.24 ( ± 1.74) 0.29 ( ± 0.21) 3.95 ( ± 1.84)
Electro cauterization 4.57 ( ± 2.12) 1.05 ( ± 0.90) 3.52 ( ± 1.74)
Spongostan� 3.62 ( ± 1.33) 3.10 ( ± 0.90) 0.52 ( ± 1.32)
Spongostan� + epinephrine 3.86 ( ± 1.59) 2.24 ( ± 0.92) 1.62 ( ± 0.93)
Table 2 P-values of pairwise comparisons of the final bleeding scores using Wilcoxon’s signed rank test
Control
ExpasylTM
+ Stasis�ExpasylTM + Stasis�
+ freshening of defect
Electro
cauterization Spongostan�
Expasyl + Stasis� 0.036 – – – –
Expasyl + Stasis� +
freshening of defect
0.022 0.586 – – –
Electro cauterization 0.034 0.100 0.181 – –
Spongostan� 0.798 0.022 0.016 0.059 –
Spongostan� + epinephrine 0.034 0.031 0.016 0.051 0.104
Table 3 P-values of pairwise comparisons of the scores of calculated bleeding reduction using Wilcoxon’s signed rank test
Control
ExpasylTM
+ Stasis�ExpasylTM + Stasis�
+ freshening of defect
Electro
cauterization Spongostan�
ExpasylTM + Stasis� 0.036 – – – –
ExpasylTM + Stasis�
+ freshening of defect
0.031 0.106 – – –
Electro cauterization 0.031 0.444 0.400 – –
Spongostan� 0.866 0.050 0.031 0.034 –
Spongostan� + epinephrine 0.295 0.141 0.051 0.150 0.204
Haemostasis in apical surgery Jensen et al.
International Endodontic Journal, 43, 57–63, 2010 ª 2010 International Endodontic Journal60
ExpasylTM and Stasis�
3 Weeks: The entire bone surface was necrotic, without
signs of repair activity. The osteocyte lacunae were
empty along the surfaces of the cavities, and numerous
macrophages and multinucleated giant cells were
observed close to the defect walls and to remnants of
ExpasylTM, which were particularly evident in concav-
ities of the defect wall.
12 Weeks: Necrotic areas could still be identified
within the defect walls with areas of undermining
resorption, nearly forming a sequester (Fig. 3). Rem-
nants of ExpasylTM were often observed, and were
always surrounded by an extensive foreign body
reaction (Fig. 3).
ExpasylTM and Stasis� with freshening of the bone defect
3 Weeks: Moderate amounts of woven bone formation
were observed close to the defect walls, particularly at
sites where the bone marrow spaces were opened
widely. Remnants of ExpasylTM were seen rarely.
However, if present, they were always accompanied
by multinucleated giant cells.
12 Weeks: The amount of osseous repair was
limited, but no signs of necrotic bone or foreign body
reaction were present.
Spongostan�
3 Weeks: Woven bone formation was observed along
the entire surface of the bone cavities. However, the
osteoblastic activity along the defect surfaces was
reduced compared with the control defects.
12 Weeks: The defects were dominated by matura-
tion of the newly formed bone, with layers of parallel-
fibered bone reinforcing the woven bone trabeculae.
Spongostan� and epinephrine
3 Weeks: Vivid new bone formation could be seen, with
woven bone throughout the former bone defect
(Fig. 4). Ongoing osteogenic activity, as indicated by
the presence of osteoid seams and osteoblasts, was a
dominating feature.
12 Weeks: Maturation of woven bone formed earlier
was seen, with only sparse signs of ongoing bone
formation. In general, the surfaces demonstrated
lamellar bone coverage.
Figure 2 Control defect after 12 weeks of healing. Most of the
original defect volume (marked with lines) is occupied by soft
tissue with the character of loose connective tissue dominated
by epidermal fat cells. Bone formed form the defects walls has
the character of mature lamellar bone.
Figure 3 Defect 12 weeks after application of ExpasylTM +
Stasis� without freshening the defect with a round bur.
Remnants of ExpasylTM (E) are surrounded by lots of multi-
nucelated giant cells (large arrows). Empty osteocyte lacunae
can be see in a bone trabecula undermined by resorption
cavities (Small arrows).
Figure 4 Defect three weeks after application of Spongostan�.
The former defect (marked with lines) is completely occupied
by newly formed woven bone. The ePTFE suture used to close
the periosteal layer can be recognized (asterisks).
Jensen et al. Haemostasis in apical surgery
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 57–63, 2010 61
Electro cauterization
3 Weeks: The surfaces of the entire cavities appeared
necrotic, without any signs of bone repair. The
osteocyte lacunae near to the surface were empty
(Fig. 5). The cell populations adjoining the surfaces
consisted almost exclusively of inflammatory cells,
mainly macrophages and some multinucleated giant
cells. In addition, many erythrocytes were often seen on
the cauterized bone surface. The opened bone marrow
often revealed signs of degeneration.
12 Weeks: The bone surface appeared vital, but
jagged after extensive osteoclastic activity. The size and
shape of the cavities were nearly identical to the
situation immediately postoperatively with very limited
signs of new bone formation.
Discussion
This study evaluated the haemostatic efficacy and
tissue reactions of different methods for local haemor-
rhage control used in apical surgery. Overall, Expa-
sylTM + Stasis� and electro cauterization proved most
efficient in reducing bleeding, while the use of Spongo-
stan� alone did not demonstrate any significant hae-
mostatic effect as compared with the control defects.
The addition of epinephrine to the Spongostan� had
some effect on the final bleeding score, without
reaching the efficacy of ExpasylTM + Stasis�.
The efficacy of ExpasylTM + Stasis� in reducing
bleeding was in accordance with a previous study
using the same model (von Arx et al. 2006). However,
a concern was the localized foreign body reaction
elicited by remnants of ExpasylTM in the bone defects.
Only limited documentation exists on tissue reactions
to aluminium chloride in paste form, but studies which
have evaluated topical application of aluminium chlo-
ride in liquid form have also reported inflammatory
reactions (Barr et al. 1993, Kopac et al. 2002). The
results of the present study suggest that these tissue
reactions can be significantly reduced by freshening the
defect with a bur. In the clinical case of using a root-
end filling material that does not set during the surgical
procedure [e.g. mineral trioxide aggregate (MTA)],
there is a risk of flushing out the material during the
freshening of the bony cavity. To avoid this, it has
proved important to use a relatively small round bur to
reduce the risk of touching the cut root surface and
MTA filling, and to prevent direct water spray on the
cut root surface.
Spongostan� is widely used in several surgical
specialties to control bleeding, but most often in
surgical sites where it can be left in situ, such as in
dental extraction sockets or in donor sites after bone
graft harvesting (Petersen et al. 1984, Finn et al. 1992,
Blinder et al. 1999). In the present study, the sponge
was removed after 2 min to conform with the typical
protocol in apical surgery (Rud et al. 2001). This
eliminated the compressive element, and the resulting
intrinsic haemostatic effect proved to be limited. Histo-
logic analysis revealed slightly delayed bone healing
that was qualitatively comparable to the control
defects. Similar findings have been reported in previous
experimental and clinical studies, where the gelatin
sponges were left in situ (Petersen et al. 1984, Finn
et al. 1992). Addition of epinephrine 1% to a gelatin
sponge or cotton pellet has been reported to provide
sufficient haemostasis to allow undisturbed placement
and setting of dentine-bonded composite resin root-end
fillings (Rud et al. 2001, Jensen et al. 2002). In the
present experimental setting, the addition of epineph-
rine to Spongostan� only marginally increased the
haemostatic effect, without reaching statistical signifi-
cance. No histologic difference in healing pattern was
observed with the addition of epinephrine. As epineph-
rine is a naturally occurring circulating hormone in the
organism, disturbance of healing was not to be
expected.
Electro cauterization provided a haemostatic effect
similar to that of ExpasylTM + Stasis�. However, bone
healing was delayed when compared to control defects
and to ExpasylTM + Stasis�-treated defects that were
Figure 5 Defect three weeks after using electro cauterization
for haemorrhage control. Multiple empty osteocyte lacunae
(small arrows) can be seen close to the defect walls (large
arrows). The soft tissue occupying the defect has the character
of immature granulation tissue. A coagulum containing many
erythrocytes is observed along the defect walls.
Haemostasis in apical surgery Jensen et al.
International Endodontic Journal, 43, 57–63, 2010 ª 2010 International Endodontic Journal62
freshened with a bur. Limited bone formation was
observed after 12 weeks of healing, following initial
signs of superficial necrosis. This can presumably be
ascribed to thermal injury, as has previously been
documented (Eriksson et al. 1982). In the early healing
phase, an adverse tissue reaction was seen in relation
to the necrotic zones. This inflammatory and foreign
body reaction was not observed after 12 weeks of
healing. Coagulated tissue remnants were removed
with a curette before suturing. It can be speculated that
the osseous healing conditions could have been
improved by removing the superficial bone layer with
a rotary instrument, as was observed with the fresh-
ened ExpasylTM + Stasis�-treated defects.
Conclusion
ExpasylTM + Stasis� and electro cauterization proved
most efficient in the reduction of bleeding from stan-
dardized bone defects. However, the same measures
were accompanied by the most pronounced adverse
tissue reactions. It is recommended to thoroughly
remove the superficial layer in the bone defect with a
rotary instrument after application of ExpasylTM + Sta-
sis� or electro cauterization in apical surgery to reduce
these unfavourable tissue reactions. Defects treated
with Spongostan� demonstrated no adverse tissue
reactions but delayed bone healing. Despite the reduced
haemostatic effect of Spongostan� and epinephrine
compared with ExpasylTM + Stasis� and electro cau-
terization, this combination will often clinically ensure
sufficient haemostasis for the undisturbed placement
and setting of a root-end filling.
Acknowledgements
The authors gratefully acknowledge the assistance of
Dr. med. vet. Daniel Mettler and the veterinarian
team of the Department of Experimental Surgery,
Bern University Hospital, Inselspital, Bern, Switzer-
land. We also thank Mrs. Britt Hoffmann and Mr.
David Reist, Department of Oral Surgery and Stoma-
tology, University of Bern, for the histologic prepara-
tion of the specimens. The statistical assistance of Mr.
D. Klingbiel, Institute of Mathematical Statistics and
Actuarial Science, University of Bern, was highly
appreciated.
Funding: The study was generously funded by a
grant from the Foundation for Dental Research and
Education (FDR), Basel, Switzerland (Grant 1–04/17).
The authors declare no conflicts of interest.
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Jensen et al. Haemostasis in apical surgery
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 57–63, 2010 63
Volumetric analysis of root fillings using spiralcomputed tomography: an in vitro study
R. Anbu, S. Nandini & N. VelmuruganDepartment of Conservative Dentistry & Endodontics, Meenakshi Ammal Dental College, Maduravoyal, Chennai, Tamilnadu, India
Abstract
Anbu R, Nandini S, Velmurugan N. Volumetric analysis of
root fillings using spiral computed tomography: an in vitro
study. International Endodontic Journal, 43, 64–68, 2010.
Aim To analyse volumetrically using spiral computed
tomography (SCT) the efficacy of various techniques to
fill root canals.
Methodology Root canals in 40 maxillary central
incisors were instrumented with K-files to size 60 and
the volume of the canal measured using SCT. The teeth
were divided into four groups of 10 each and root filled
by lateral compaction, Thermafil, Obtura II and System
B techniques, respectively. AH plus was used as sealer
with all techniques. The filled volume in each canal
was measured using SCT and the percentage of
obturated volume (POV) was calculated. The data were
statistically analysed using Kruskal–Wallis test and
Mann–Whitney U-test.
Results The four groups were comparable in canal
volume. The overall POV was 80.4%, 93.3%, 84.8%
and 93.7% for lateral compaction, Thermafil, Obtura II
and System B, respectively (P < 0.05).
Conclusion The greatest POV was obtained with
System B and Thermafil. Voids were seen in all root
fillings.
Keywords: Obtura II, obturation, percentage of
obturated volume, spiral CT, three dimensional, volu-
metric analysis.
Received 9 May 2009; accepted 25 August 2009
Introduction
A good root filling is essential to prevent bacteria and/
or their by-products from reaching the periapical
region. There are various methods available for filling
canals ranging from cold lateral compaction to
thermoplasticized techniques. Various experimental
methods have been used to assess the quality of root
fillings, such as radioisotope (Haıkel et al. 2000), dye
penetration (McRobert & Lumley 1997, Venturi 2006),
fluid filtration (Kontakiotis et al. 2007), bacterial
leakage (Jacobson et al. 2002), microscopic analysis
(De-Deus et al. 2006, 2008), clearing techniques
(Oliver & Abbott 2001) and Micro CT (Hammad et al.
2009). It has been reported that spiral computerized
tomography (SCT) has been a useful tool in various
in vivo and laboratory studies. It was concluded that
with SCT three-dimensional volume measurements are
possible without sectioning specimens thus avoiding
loss of material (Nandini et al. 2006, Hammad et al.
2009).
The aim of this study was to assess the efficacy of
different root filling techniques by calculating the
percentage of obturated volume (POV).
Materials and methods
Tooth specimens
Forty single rooted maxillary central incisors were
selected. Soft tissue remnants and calculus were
removed. Collection, storage, sterilization and handling
of extracted teeth followed the Occupational Safety and
Health Administration (OSHA) guidelines and regula-
tions (Reuben et al. 2008).
Correspondence: Dr Natanasabapathy Velmurugan, (Prof and
Head), Department of Conservative Dentistry & Endodontics,
Meenakshi Ammal Dental college, Allapakkam main road,
Maduravoyal, Chennai 95, Tamil nadu, India (Tel.:
09840164167; fax: 91 44 23781631; e-mail: Vel9911@
yahoo.com).
doi:10.1111/j.1365-2591.2009.01638.x
International Endodontic Journal, 43, 64–68, 2010 ª 2009 International Endodontic Journal64
All specimens were checked for number and curva-
ture of root canals radiographically. Teeth with single
straight canals were chosen whilst teeth with incom-
pletely formed apices, calcified canals, fractures or
resorption were excluded.
Tooth preparation
An access cavity was prepared in each tooth and a size
10 K-file introduced until the tip was just visible at the
foramen of the root. The working length was derived by
subtracting 0.5 mm from the measured length. Orifice
enlargement was achieved with sizes 2, 3 and 4 Gates
Glidden drills (Dentsply Maillefer, Ballaigues, Switzer-
land). Apical enlargement was completed to size 60
with K-files and a step-back procedure was used until
the preparation blended with the coronal flaring. Two
millilitres of 1% sodium hypochlorite and 2 mL of
saline were used as irrigants between each file size.
Ethylene-Diamine Tetraacetic acid (EDTA) paste (RC
Help; Prime Dental Products, Thane, India) was used as
a lubricant during instrumentation. Before filling, root
canals were dried using a size 60 paper point.
The teeth were numbered from 1 to 40. Specimens
were scanned using a Light Speed VCT Scanner (GE
Electricals, Milwaukee, WI, USA). They were then
viewed under high resolution, both cross-sectionally
and longitudinally with a constant thickness of
0.625 mm/slice and a constant spiral or table speed
of 0.5 and 140 kVp. The scanned data was then
transferred to Advantage windows work station
(GE system, Milwaukee, WI, USA) image analysis and
evaluated. The area of prepared root canal in each slice
was measured from cemento-enamel junction (CEJ) to
the apex of the root. The volume of root canal in each
slice was calculated by multiplying the root canal area
by the slice thickness (0.625 mm). Finally, the volume
of each canal was calculated.
The root length was divided into three equal parts;
coronal, middle and apical thirds and the volume of
each segment was calculated separately.
Forty teeth were randomly divided into four groups
of 10 each.
In all the teeth AH Plus sealer (Dentsply Maillefer)
was placed into the canal using a lentulo-spiral filler.
Group-I: lateral compaction (LC)
A size 60 gutta-percha (GP) (Dentsply Maillefer) was
coated with the sealer and placed in the canal to
working length with tug-back. Lateral compaction was
achieved using additional accessory GP cones and
standardized finger spreaders (Dentsply Maillefer) start-
ing 1 mm short of working length. When the points
prevented the spreader penetration beyond the coronal
third of the canal, the canal was considered to be
adequately filled and excess GP was removed at the CEJ
using a heated condenser. The GP at the CEJ was
compacted using a cold plugger.
Group-II: Thermafil
A 60 size Thermafil (Dentsply Maillefer) verifier was
used to check the size of the canal. A 60 size Thermafil
cone was heated (ThermaPrep Plus Oven, Tulsa Dental
Products, OK, USA) according to the manufacturer’s
instruction and introduced into each canal using firm
apical pressure within 0.5 mm short of working length.
An inverted cone bur was used to cut the plastic shaft
1–2 mm within the access cavity. Excess GP was
removed using pluggers (Gencoglu et al. 2008).
Group-III: Obtura II
A 20 gauge Obtura (Obtura Spartan, Fenton, MI, USA)
needle tip was selected. The tip was inserted into the
canal 3–5 mm short of the working length. The
temperature was set at 200 �C, the trigger was pressed
so that the molten GP flowed and the tip was
withdrawn slowly out of the canal. The apical segment
was compacted using appropriate Obtura pluggers.
Backfilling was achieved by the application of thermo-
plasticized GP in 4–5-increments, followed by uniform
compaction with pluggers.
Group-IV: System B
A medium-large nonstandardized GP cone was placed
to within 0.5 mm of the working length. A medium-
large System B (EIE/Analytic Technology, Redmond,
WA, USA) insert tip, which bound in the canal 3 mm
from the working length, was used for the down-pack.
The heat was preset to 200 �C during the first down-
pack. An accessory GP cone was then placed into the
canal and the heat was preset to 100 or 250 �C during
the second down-pack. This procedure was repeated
until the entire root canal was filled (Gencoglu et al.
2008).
A second SCT scan was performed to determine the
volume of GP and sealer. POV in each tooth was
calculated. POV in the coronal, middle and apical thirds
for each tooth was calculated separately (Fig. 1).
Anbu et al. Volumetric analysis of root fillings
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 64–68, 2010 65
Statistical analysis
Statistical analysis was performed with nonparametric
tests (Kruskal–Wallis and Mann–Whitney U-test). The
software used was SPSS (Statistical Package for Social
Sciences, Chicago, IL, USA) version 11.5. The level of
significance was set at P < 0.05.
Results
The volume (mean & standard deviation) of root canals
after cleaning and shaping for each group is given in
Table 1. The four groups were statistically comparable
in respect of canal volume (P > 0.05).
All POV values are summarized in Table 2. The
System B and Thermafil gave the highest POV values
and were significantly different in comparison with
Obtura II and lateral compaction (P < 0.05).
Discussion
Traditional methods of evaluating root fillings have
disadvantages. On sectioning the root, there could be
loss of material which might mimic voids. Radiographs
give only two-dimensional interpretations (Robinson
et al. 2002). The time taken for fluid filtration (Pommel
& Camps 2001) and clearing techniques (Oliver &
Abbott 2001) may be a concern. Dye penetration
studies do not correlate clinically (Oliver & Abbott
2001) whereas dye extraction studies evaluate only the
apical third of the tooth (Camps & Pashley 2003).
Bacterial leakage studies do not simulate exact clinical
conditions, need long periods of observation and do not
allow quantification of the number of penetrating
bacteria (Siqueira et al. 1999, 2000).
A literature search revealed that only sectioning
studies have been undertaken to assess thermoplasti-
cized root fillings at various levels (Jung et al. 2003,
ElAyouti et al. 2005, De-Deus et al. 2006). SCT, a
noninvasive technique gives a 3D interpretation (Nair
& Nair 2007) at various levels, avoids loss of material
(Hammad et al. 2009), yields reproducible results and
the specimens can be used for further research. The
specific location of voids can be determined accurately.
Recent studies have proved that SCT provides volu-
metric analysis of root fillings and remaining remnants
of root fillings (Bartletta et al. 2008, Hammad et al.
2008). Hence, SCT was chosen as the tool for inves-
tigating the efficacy of fillings in this study. The only
limitation of SCT is that it is difficult to differentiate GP
and sealer.
In this study, Thermafil and System B gave the
highest overall POV. The reason could be that the use
of heat softened GP had created a better homogenous
mass with less voids and better adaptation of the GP
to the canal wall. This is in accordance to the studies
reported by De-Deus et al. (2006) and Gencoglu et al.
(a) (b)
Figure 1 (a) SCT slice showing canal
obturated with Obtura II. (b) SCT slice
showing canal obturated by System B.
203 · 123 mm (300 · 300 DPI).
Table 1 The volume (in cm3) of root canals for each group
Groups Mean Standard deviation
LC 0.033 0.0055
Thermafil 0.035 0.0043
Obtura II 0.034 0.0051
System B 0.035 0.0047
LC, lateral compaction.
Volumetric analysis of root fillings Anbu et al.
International Endodontic Journal, 43, 64–68, 2010 ª 2009 International Endodontic Journal66
(2002), who showed that Thermafil produced a
significantly higher POV. In this study two specimens
in the System B group had voids between the coronal-
middle and middle-apical segments. These voids were
not through and through but were found only in a
few sections, which could have been missed in a
conventional radiograph. Obtura II, a thermoplastic
injectable technique had only 85% of overall POV.
Presence of voids in the apical region had reduced the
overall POV, which may be due to failure of the needle
tip to reach the apical third, poor compaction and
entrapment of air. The use of a 20-guage Obtura
needle which has an outer diameter of 0.81 mm could
have prevented the tip from reaching the appropriate
depth.
Lateral compaction had 83% of overall filling, the
lowest value of all the fillings. This was mainly because
this technique does not produce a homogenous mass
and may leave spaces between the GP and the dentinal
walls or accessory cones. According to Schilder (2006),
in lateral compaction the final filling had the appear-
ance of numerous GP cones that had been tightly
pressed together and joined by frictional grip and the
cementing substance. Spreader tracts can be devoid of
sealer or the sealer can resorb later leading to voids. In
this study, voids were seen between the accessory cones
throughout the length of the canal.
When comparing the POV of coronal, middle and
apical thirds of Thermafil, System B and lateral
compaction techniques, there was no difference in
the efficacy of fillings. It was seen that the POV of
coronal third of lateral compaction, Thermafil and
System B was slightly less than apical third. This
could be due to the use of coronal orifice enlargement
with Gates Glidden drills and lack of additional
vertical condensation with pluggers in the Thermafil
group. Even though pluggers were used in case of
System B for coronal compaction there was a decrease
in efficacy. This could be due to the mismatch in
taper of the instrument to that of the enlarged canal
orifice.
Conclusion
Within the limitations of this study, voids were seen in
all the root fillings. The greatest POV was obtained with
System B and Thermafil techniques; lateral compac-
tion, produced the least POV. SCT appears to be a
valuable tool to locate voids and to assess the efficacy of
obturation at various levels.
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LC 80.4 ± 1.6 (X) 80.7 ± 3.6 (a) 81.5 ± 3.1 (a) 83 ± 3.6 (a)
Thermafil 93.3 ± 2.4 (Y) 92.5 ± 3.4 (b) 95.5 ± 4.7 (b) 97.4 ± 5.4 (b)
Obtura II 84.8 ± 6 (X) 92.9 ± 8.5 (b) 95.6 ± 6.1 (b) 54.3 ± 19.3 (c)
System B 93.7 ± 3.6 (Y) 92.1 ± 5.7 (b) 94.7 ± 6 (b) 96.2 ± 6.2 (b)
Cells with the same letter denote no statistical significance between them (P > 0.05).
Capital letters were used for the overall data.
POV, percentage of obturated volume; LC, lateral compaction.
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International Endodontic Journal, 43, 64–68, 2010 ª 2009 International Endodontic Journal68
Influence of the shape of artificial canals on thefatigue resistance of NiTi rotary instruments
G. Plotino1, N. M. Grande1, M. Cordaro2, L. Testarelli1 & G Gambarini1
1University of Roma ‘La Sapienza’, Rome, Italy; and 2Catholic University of Sacred Heart, Rome, Italy
Abstract
Plotino G, Grande NM, Cordaro M, Testarelli L, Gam-
barini G. Influence of the shape of artificial canals on the
fatigue resistance of NiTi rotary instruments. International
Endodontic Journal, 43, 69–75, 2010.
Aim To investigate the influence of the trajectory of
NiTi rotary instruments on the outcome of cyclic
fatigue tests.
Methodology Ten ProFile and Mtwo instruments tip
size 20, taper 0.06 and tip size 25, taper 0.06 were
tested in two simulated root canals with an angle of
curvature of 60� and radius of curvature of 5 mm but
with different shape. Geometrical analysis of the angle
and radius of the curvature that each instrument
followed inside the two different artificial canals was
performed on digital images. The instruments were
then rotated until fracture at a constant speed of
300 rpm to calculate the number of cycles to failure
(NCF) and the length of the fractured fragment. Mean
values were calculated and analysed using two different
multivariate linear regression models and an indepen-
dent sample t-test.
Results The shape of the artificial root canal used in
cyclic fatigue studies influenced the trajectory of the
instrument. This difference is reflected by the NCF
measured for the same instrument in the different
artificial root canals and by the impact of the type of
canal on both the NCF (St.b = 0.514) and fragment
length (St.b = )0.920).
Conclusions Small variations in the geometrical
parameters of the curvature of an instrument subjected
to flexural fatigue could have a significant influence on
the results of fatigue tests.
Keywords: angle of curvature, artificial canal, cyclic
fatigue test, radius of curvature.
Received 27 June 2009; accepted 2 September 2009
Introduction
Fracture of instruments used in rotary motion occurs in
two different ways: fracture due to torsion and fracture
due to flexural fatigue (Serene et al. 1995, Sattapan
et al. 2000, Ullmann & Peters 2005). Torsional fracture
occurs when an instrument tip or another part of the
instrument is locked in a canal whilst the shank
continues to rotate. When the torque exerted by the
hand-piece exceeds the elastic limit of the metal,
fracture of the tip becomes inevitable (Peters 2004,
Parashos & Messer 2006). Instruments fractured
because of torsional loads often carry specific signs
such as plastic deformation (Sattapan et al. 2000).
Fracture due to fatigue through flexure occurs
because of metal fatigue. The instrument does not bind
in the canal but it rotates freely in a curvature,
generating tension/compression cycles at the point of
maximum flexure until the fracture occurs (Pruett et al.
1997, Haikel et al. 1999). As an instrument is held in a
static position and continues to rotate, one half of the
instrument shaft on the outside of the curve is in
tension, whilst the half of the shaft on the inside of the
curve is in compression. This repeated tension–
compression cycle, caused by rotation within curved
canals, increases cyclic fatigue of the instrument over
time and may be an important factor in instrument
fracture (Pruett et al. 1997).
Correspondance: Dr Gianluca Plotino, Via Eleonora Duse 22,
00197 Rome, Italy (Tel.: +393396910098; fax:
+3968072289; e-mail: [email protected]).
doi:10.1111/j.1365-2591.2009.01641.x
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 69–75, 2010 69
Resistance of rotary instruments to cyclic fatigue is
affected by the angle and radius of canal curvature and
the size and taper of the instrument. Increased severity
in the angle and radius of the curves around which the
instrument rotates decreases instrument lifespan
(Pruett et al. 1997, Haikel et al. 1999, Grande et al.
2006). Instruments have been tested in canals having
radii of 2 mm, 5 mm and 10 mm, with the conclusion
that the smaller the radius, the shorter the life of the
instrument when rotating (Pruett et al. 1997, Haikel
et al. 1999, Grande et al. 2006). Similarly, several
studies have shown that increased diameter at the
point of maximum curvature of the instrument, which
is determined by tip size and taper, reduces the time to
fracture (Pruett et al. 1997, Haikel et al. 1999, Plotino
et al. 2006, 2007). Only the study by Yared et al.
(2000) did not support these findings. Ruddle (2002)
has asserted that the position of the curvature of a
canal is a factor in instrument safety, a point that was
demonstrated in an earlier study (Malagnino et al.
1999). When the curvature is localized in a coronal
portion of the root canal, the instrument is subjected to
the maximum stress in the area in which its diameter is
largest.
In nearly all studies reported in the endodontic
literature, the rotating instrument was either confined
in a glass or metal tube, in a grooved block-and-rod
assembly or in a sloped metal block (Plotino et al.
2009); there has been no mention of the ‘fit’ of the
instrument in the tube or groove. As the instrument is
likely to be fitting loosely, the description of the radius
of curvature in those studies is likely to be overstated;
that is, the file was actually bent less severely than
reported. Previous studies using cylindrical metallic
tubes to test the cyclic fatigue life of NiTi rotary
instruments reported that the tubes do not sufficiently
constrain the shafts of the smaller instruments (Pruett
et al. 1997, Mize et al. 1998, Yared et al. 1999, 2000).
The aim of the present study was to investigate the
influence of the trajectory of NiTi rotary instruments on
the outcome of cyclic fatigue tests. The null hypothesis
tested was that there was no difference in the cyclic
fatigue resistance of the same instrument tested in two
artificial canals with the same radius and angle of
curvature but with different shapes.
Materials and methods
Ten ProFile NiTi rotary instruments (Dentsply Maillefer,
Ballaigues, Switzerland) tip size 20, 0.06 taper, ten
ProFile instruments tip size 25, 0.06 taper, ten Mtwo
NiTi rotary instruments (Sweden & Martina, Padova,
Italy) tip size 20, 0.06 taper and ten Mtwo instruments
tip size 25, 0.06 taper were selected.
Two simulated root canals with an angle of curva-
ture of 60� and radius of curvature of 5 mm were
constructed for each instrument size. The centre of the
curvature was approximately 5 mm from the tip of the
instrument, the curved segment of the canal was
approximately 5 mm in length and the linear segment
between the tip of the instrument and the end-point of
the curvature was approximately 2.5 mm. The artifi-
cial canals with two different shapes were milled in
stainless-steel blocks with a precision milling machine.
An artificial canal (A) was constructed with a
tapered shape corresponding to the dimensions of the
instruments tested (tip size and taper) (Fig. 1a), thus
providing the instrument with a suitable trajectory. To
ensure the accuracy of the size of each canal a copper
duplicate of each instrument was milled increasing the
original size of the instrument by 0.1 mm using a
computer numerical control machining bench (Bridge-
port VMC 760XP3; Hardinge Machine Tools Ltd.,
Leicester, UK). The copper duplicates were constructed
according to the curvature parameters that were
chosen for the study. With these negative moulds the
artificial canals were made using a die-sinking electri-
cal-discharge machining process (Agietron Hyperspark
3, AGIE Sa, Losone, Switzerland) in a stainless-steel
block. The depth of each artificial canal was machined
to the maximum diameter of the instrument +0.2 mm,
allowing the instrument to rotate freely inside the
artificial canal. The blocks were hardened through
annealing.
A second artificial canal (B) was constructed with a
tapered shape but with larger dimensions that did not
match the instrument size and taper; the artificial canal
was machined increasing the original size of the
instrument by 0.3 mm (Fig. 1b).
Each artificial canal was mounted on a stainless-steel
block that was connected to a frame to which a mobile
plastic support for the hand-piece was also connected.
The dental hand-piece was mounted upon a mobile
device that allowed for precise and simple placement of
each instrument inside the artificial canal, ensuring
three-dimensional alignment and positioning of the
instruments to the same depth. The artificial canal was
covered with tempered glass to prevent the instruments
from slipping out and to allow for observation of the
instrument.
Geometrical analysis of the trajectory that each
instrument followed inside the two different artificial
Influence of trajectory on fatigue resistance Plotino et al.
International Endodontic Journal, 43, 69–75, 2010 ª 2009 International Endodontic Journal70
canals was performed on digital images, determining
two parameters: angle and radius of the curvature
described by the instruments as measured by Pruett
et al. (1997). A straight line (PQ) was drawn along the
long axis of the coronal straight portion of the
instrument. A second line (TS) was drawn along the
long axis of the apical straight portion of the instru-
ment. There was a point on each of these lines at which
the instrument deviated to begin (Q) or end (S) the
curvature. The curved portion of the instrument was
represented by a segment of a circle (C) with tangents
at these points. The most precise circumference that
lied on the trajectory of the instrument was geometri-
cally determined using the osculating circumference
method (Gray 1997). The osculating circle of a curve at
a given point is the circle that best approximate the
curve at that point and it is unique. This method was
chosen because the curvature followed by an instru-
ment not constrained in a precise trajectory is not a
circumference, but a plain curve with a different
equation. In these cases, the above described is the
most precise method to define a curvature by the
parameters of radius and angle of a circumference. It is
possible to determine the osculating circle passing
through three points of a curve. The points that were
chosen on the trajectory of the instruments were the
beginning (Q) and the end (S) of the curve and a point B
that was chosen as the centre of mass of the triangle
resulting from the points Q, S and R that was the point
in which the straight coronal and apical portions of the
instrument met. The angle of curvature was defined as
the number of degrees on the arc of the circle between
the beginning and end-points of the curvature; the
radius of the circle was defined as the radius of the
canal curvature in millimetres (Fig. 2).
The calculation of the radius and angle of curvature
determined by the osculating circumference method
was repeated for each instrument analysed in the two
(a) (b)
Figure 1 The artificial canals used in the
present study. (a) canal A; (b) canal B.
Figure 2 The osculating circumference method to determine
the geometrical parameters of the trajectory of the instrument.
Plotino et al. Influence of trajectory on fatigue resistance
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 69–75, 2010 71
different artificial canals. Mean values were then
calculated for each instrument size.
ProFile and Mtwo instruments were then tested
within the two different artificial canals. The instru-
ments were rotated at a constant speed of 300 rpm
using a 6:1 reduction hand-piece (Sirona Dental
Systems GmbH, Bensheim, Germany) powered by a
torque-controlled motor (Silver, VDW GmbH, Munich,
Germany). To reduce the friction of the file as it
contacted the artificial canal walls, high-flow synthetic
oil designed for lubrication of mechanical parts (Super
Oil, Singer, Elizabethport, NJ, USA) was applied. All
instruments were rotated until fracture occurred.
Fracture was easily detectable because the instruments
were visible through the glass window. The time to
fracture for each file was recorded visually with a 1/
100 s chronometer, and the number of rotations was
calculated to the nearest whole number. The time to
fracture was multiplied by the number of rotations per
minute to obtain the number of cycles to failure (NCF)
for each instrument. Mean values were then calculated.
The length of the fractured tip was also recorded for
each instrument and the mean values were then
calculated for each instrument type in each group.
Analysed data consisted of NCF and the length of the
fractured tip for each instrument tested under the
specified artificial canal, and the radius and angle of
curvature curvature followed by the instruments in
both the artificial root canals tested. The data were
processed using spss software (SPSS, Oakbrook, IL,
USA). Means and standard deviations (SD) were
calculated. Two different multivariate linear regression
models were performed to investigate the effects of the
independent variables considered in the model (size of
the instrument, type of the instrument, type of the
artificial root canal) on the dependent variables anal-
ysed (NCF and fragment length). An independent
sample t-test was used to analyse significant differences
for the angle and radius of curvature measured
between the two artificial root canals for each instru-
ment tested. Significance was determined at the 95%
confidence level.
Results
Mean values and SD of the radius and angle of
curvature described by the instruments in the different
artificial canals are displayed in Table 1.
Mean values ± SD expressed as NCF and the mean
length of the fractured segment are displayed in
Table 2.
In the first model, considering the NCF as dependent
variable, the overall regression model was statistically
significant (F = 13.4; P = 0.000; R = 0.586). Further-
more, amongst the independent variables canal type
(A, B) and instrument size (20, 0.06; 25, 0.06) were
statistically significant (P < 0.05), whilst the instru-
ment type (Mtwo, ProFile) was not (P = 0.371). The
Table 1 Mean values ± SD of the radius and angle of curvature described by the instruments in the different artificial canals and
P-values (t-test between canal A and B)
ProFile size 20/0.06 taper Angle (�) Radius (mm) Mtwo size 20/0.06 taper Angle (�) Radius (mm)
Canal A 60 ± 0.1 4.9 ± 0.3 Canal A 60 ± 0.01 5 ± 0.1
Canal B 51 ± 0.1 5.7 ± 0.3 Canal B 55 ± 0.1 5.9 ± 0.2
ProFile size 25/0.06 taper Angle (�) Radius (mm) Mtwo size 25/0.06 taper Angle (�) Radius (mm)
Canal A 60 ± 0.1 5 ± 0.2 Canal A 60 ± 0.1 4.9 ± 0,3
Canal B 50 ± 0.1 6.6 ± 0.4 Canal B 54 ± 0.3 6 ± 0,4
Table 2 Mean ± SD expressed in number of cycles to failure (NCF) registered during the cyclic fatigue testing, mean length of the
fragments ± SD registered for each group (in mm) and increase of the lifespan between the two groups
ProFile size 20/0.06 taper NCF mm Mtwo size 20/0.06 taper NCF mm
Canal A 605 ± 52 4.9 ± 0.4 Canal A 617 ± 73 5 ± 0.2
Canal B 677 ± 55 3.3 ± 0.4 Canal B 703 ± 61 3.5 ± 0.3
Difference* 10% Difference* 12%
ProFile size 25/0.06 taper NCF mm Mtwo size 25/0.06 taper NCF mm
Canal A 564 ± 63 4,9 ± 0.3 Canal A 566 ± 84 5.1 ± 0.3
Canal B 645 ± 75 3.1 ± 0.3 Canal B 659 ± 82 3,6 ± 0.3
Difference* 12.5% Difference* 14%
*Indicates an increase of the lifespan for canal B compared to canal A.
Influence of trajectory on fatigue resistance Plotino et al.
International Endodontic Journal, 43, 69–75, 2010 ª 2009 International Endodontic Journal72
multivariate linear regression showed that canal type
was the independent variable with the greatest impact
in the model; canal B positively affected the NCF value
(St.b = 0.514, P < 0.000) when compared with canal
A, whilst an increasing in size negatively affected the
outcome variable (St.b = )0.260, P < 0.000).
In the second model, considering the fragment
length as dependent variable, the overall regression
model was statistically significant (F = 178.9;
P = 0.000; R = 0.935). Even considering the fragment
length the variable with the greater impact in the
model was the canal type, canal B negatively affected
the length of the fragment (St.b = )0.920, P < 0.000)
whilst size of the instrument was not statistically
significant (P = 0.844) and type of instrument has a
lower impact on the output variable (St.b = )0.179,
P < 0.000).
For all the instruments tested a statistically signifi-
cant difference was found between canal A and canal B
for both angle and radius of curvature (P < 0.000).
Discussion
Clinically, NiTi rotary instruments are subjected to both
torsional load and cyclic fatigue (Gambarini 2001,
Ullmann & Peters 2005), and ongoing research aims to
clarify the relative contributions of both factors to
instrument separation (Peters 2004).
Both cyclic fatigue tests (Pruett et al. 1997, Haikel
et al. 1999) and torsion tests (Camps & Pertot 1995,
Yared 2004, Ullmann & Peters 2005) have been
performed to investigate how these factors may influ-
ence the behaviour of NiTi rotary instruments in vitro.
In addition, torsional properties of used instruments
have been investigated (Yared et al. 2003, Yared 2004,
Ullmann & Peters 2005) to analyse how the combina-
tion of these two factors may influence instrument
failure.
The results of the present study showed that the
shape of the artificial root canal used in cyclic fatigue
studies influenced the trajectory of the instrument; for
all the instrument tested both angle and radius of the
curve statistically varied between canal A and B
(P < 0.000). This difference is reflected by the number
of cycles to failure measured for the same instrument in
the different artificial root canals and in the high
impact of the type of canal on both the NCF
(St.b = 0.514) and fragment length (St.b = )0.920).
The results of the present study showed a statistically
significant increase in the number of cycles to failure
when instruments were tested in an artificial canal that
does not sufficiently restrict the instrument shaft (canal
B). In this canal, the instrument would tend to regain
its original straight shape, aligning into a trajectory of
greater radius and reduced angle; that is, the file was
actually bent less severely than reported.
The results of the present study confirmed that the
size of the instrument at the point of maximum
curvature influenced resistance to fracture for cyclic
fatigue: bigger instruments are less resistant than
smaller instruments. That is, NCF decreased as the
diameter of the instrument increased (Pruett et al.
1997, Haikel et al. 1999, Grande et al. 2006, Plotino
et al. 2006, 2007). This is due to the fact that when a
curved root canal instrument rotates, any points within
it in the segment subjected to the maximum stress,
except those in the centre (neutral axis), are subjected
to repeated tensile or compressive strains. The farther
away from the central axis, the greater the imposed
strain at that point (Craig 1997). This explains why
instruments of a larger diameter are affected by fatigue
more than smaller ones.
Analysis of the data regarding the length of the
fractured segment revealed a statistically significant
difference in the mean size between canal A and canal
B for all of the instrument sizes. The centre of the
curvature was constructed approximately 5 mm from
the tip of the instrument for both canal A and canal B.
Instruments subjected to cyclic fatigue fractured at the
centre of the curvature or just below this point (Pruett
et al. 1997, Fife et al. 2004). The results of the present
study demonstrated that when the instruments were
tested in a precise artificial root canal they followed
precisely the trajectory established in the construction
of the canal. In fact, in the present study instruments
tested in canal A fractured at the established point of
maximum stress, as expected. This confirms previous
findings (Fife et al. 2004, Grande et al. 2006, Plotino
et al. 2006, 2007). On the contrary, data demonstrated
a significant decrease in the mean length of the
fragments for instruments tested in canal B. This was
due to the fact that instruments tested in canal B did
not followed the trajectory established by parameters
with which the artificial canal was constructed and
consequently the point of maximum stress were the
instrument fracture may vary.
Furthermore, considering the fragment length, there
was a minor but statistically significant impact of the
type of instrument on this variable (St.b = )0.179).
This was because different instruments followed an
unpredictable trajectory if the canal in which they were
tested did not guide them in a precise trajectory.
Plotino et al. Influence of trajectory on fatigue resistance
ª 2009 International Endodontic Journal International Endodontic Journal, 43, 69–75, 2010 73
As above mentioned, bending properties of different
files may determine a different trajectory if the file is not
constrained in a precise trajectory. If testing is com-
pleted for all different files at a given angle to ensure
consistency, the bending properties of the different files
determining different angles of curvature, thus bias the
results and the comparisons. To limit these problems,
Cheung & Darvell (2007a,b,c) constrained the instru-
ment into a curvature using three stainless-steel pins.
They used three smooth cylindrical pins of 2 mm
diameter from a high hardness stainless steel mounted
in acrylic shims, which were adjustable in the hori-
zontal direction; the position of the pins determines the
curvature of the instrument. A small V-shaped groove
prepared on the lowest pin maintained the position of
the tip of the instrument during rotation. The authors
reported in detail on the effect of surface strain ampli-
tude on fatigue failure using it as a different indicator of
the stress on instruments instead of radius and angle of
curvature. It has been reported in a three-point bending
test of NiTi wires that such constraints will produce a
curvature that is circular (Wick et al. 1995). The
authors affirmed that although this cannot actually be
true, the approximation should be reasonable. Unfortu-
nately, NiTi endodontic files are tapered and with
different cross-sectional design. The different bending
properties of the different files and the different bending
properties between the coronal and apical portion of the
same file may determine a different trajectory between
the pins, if the file is not constrained precisely.
The present study sought to overcome the limitations
of some laboratory studies in terms of the model used
for testing. The artificial canal was specifically designed
for each instrument in terms of size and taper, giving it
a precise trajectory. Cylindrical metallic tubes used in
previous studies (Pruett et al. 1997, Mize et al. 1998,
Yared et al. 1999, 2000, Melo et al. 2002) did not
sufficiently restrict the instrument shaft, which would
tend to regain its original straight shape, aligning into a
trajectory of greater radius and reduced angle (Yared
et al. 1999, 2000, Melo et al. 2002, Bahia & Buono
2005). The results of a previous study (Plotino et al.
2009b) reported that an artificial canal manufactured
as described in the present to riproduce instrument size
and taper seems to guarantee that different NiTi rotary
instruments may follow a precise and repeatable
trajectory in terms of radius and angle of curvature.
On the contrary, if the artificial canal is not identical (in
shape and size) to the instrument, its trajectory will not
respond to the established parameters, thus having a
reduced curvature during the test. The results of the
present study demonstrated that the variation in the
trajectory followed by the instruments in the artificial
canals used to test fatigue resistance could influence
the results of cyclic fatigue tests.
Conclusions
The null hypothesis tested in the present study has
been rejected. Results of the present study reported that
even small variations of the geometrical parameters of
the curvature of an instrument subjected to flexural
fatigue could determine a significant influence on the
results of fatigue tests. The standardization of the
parameters and devices used for cyclic fatigue testing of
NiTi rotary instruments is lacking. A more precise
regulation is required to obtain more consistent and
comparable results in different studies.
References
Bahia M, Buono V (2005) Decrease in the fatigue resistance of
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Camps JJ, Pertot WJ (1995) Torsional and stiffness properties
of nickel-titanium K files. International Endodontic Journal 28,
239–43.
Cheung GS, Darvell BW (2007a) Fatigue testing of a NiTi
rotary instrument. Part 1: strain-life relationship. Interna-
tional Endodontic Journal 40, 612–8.
Cheung GS, Darvell BW (2007b) Fatigue testing of a NiTi
rotary instrument. Part 2: fractographic analysis. Interna-
tional Endodontic Journal 40, 619–25.
Cheung GS, Darvell BW (2007c) Low-cycle fatigue of NiTi
rotary instruments of various cross-sectional shapes. Inter-
national Endodontic Journal 40, 626–32.
Craig RG (1997) Restorative Dental Materials, 10th edn. St.
Louis, MO, USA: Mosby.
Fife D, Gambarini G, Britto LR (2004) Cyclic fatigue testing of
ProTaper NiTi rotary instruments after clinical use. Oral
Surgery Oral Medicine Oral Pathology Oral Radiology and
Endodontology 97, 251–6.
Gambarini G (2001) Cyclic fatigue of ProFile rotary instru-
ments after prolonged clinical use. Internatiomal Endodontic
Journal 34, 386–9.
Grande NM, Plotino G, Pecci R, Bedini R, Somma F (2006)
Cyclic fatigue resistance and three-dimensional analysis of
instruments from two nickel-titanium rotary systems.
International Endodontic Journal 39, 755–63.
Gray A (1997) Osculating circles to plane curves. In: Gray A,
Abbena E, Salamon S, eds. Modern Differential Geometry of
Curves and Surfaces with Mathematic, 2nd edn. Boca Raton,
FL: CRC Press, pp. 111–5.
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Haikel Y, Serfaty R, Bateman G, Senger B, Allemann C (1999)
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(2009) A review on cyclic fatigue test of nickel-titanium
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(2006) A comparison of cyclic fatigue between used and
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(2007) Influence of a brushing working motion on the
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(2009b) Measurement of the trajectory of different NiTi
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ª 2009 International Endodontic Journal International Endodontic Journal, 43, 69–75, 2010 75
CASE REPORT
Apexogenesis after initial root canaltreatment of an immature maxillaryincisor – a case report
S. R. Kvinnsland1, A. Bardsen2 & I. Fristad2
1Clinic of Dentistry – Endodontics; and 2Department of Clinical Dentistry – Endodontics,
University of Bergen, Bergen, Norway
Abstract
Kvinnsland SR, Bardsen A, Fristad I. Apexogenesis after initial root canal treatment of an
immature maxillary incisor – a case report. International Endodontic Journal, 43, 76–83, 2010.
Aim To present a case where a traumatized, immature tooth still showed capacity for
continued root development and apexogenesis after root canal treatment was initiated
based on an inaccurate pulpal diagnosis.
Summary Traumatic dental injuries may result in endodontic complications. Treatment
strategies for traumatized, immature teeth should aim at preserving pulp vitality to
ensure further root development and tooth maturation. A 9-year-old boy, who had
suffered a concussion injury to the maxillary anterior teeth, was referred after
endodontic treatment was initiated in tooth 21 one week earlier. The tooth had
incomplete root length, thin dentinal walls and a wide open apex. The pulp chamber
had been accessed, and the pulp canal instrumented to size 100. According to the
referral, bleeding from the root made it difficult to fill the root canal with calcium
hydroxide. No radiographic signs of apical breakdown were recorded. Based on
radiographic and clinical findings, a conservative treatment approach was followed to
allow continued root development. Follow-up with radiographic examination every 3rd
month was performed for 15 months. Continued root formation with apical closure
was recorded. In the cervical area, a hard tissue barrier developed, which was sealed
with white mineral trioxide aggregate (MTA). Bonded composite was used to seal the
access cavity. At the final 2 years follow-up, the tooth showed further root
development and was free from symptoms.
Key learning points
• Endodontic treatment of immature teeth may result in a poor long-term prognosis.
• The pulp of immature teeth has a significant repair potential as long as infection is
prevented.
doi:10.1111/j.1365-2591.2009.01645.x
Correspondence: Inge Fristad, Department of Clinical Dentistry – Endodontics, University of
Bergen, Arstadveien 17, N-5009 Bergen, Norway (Tel.: + 47 55 58 66 04; e-mail: inge.fristad@
iko.uib.no).
International Endodontic Journal, 43, 76–83, 2010 ª 2010 International Endodontic Journal76
• Treatment strategies of traumatized, immature permanent teeth should aim at
preserving pulp vitality to secure further root development and tooth maturation.
• Radiographic interpretation of the periapical area of immature teeth may be confused
by the un-mineralized radiolucent zone surrounding the dental papilla.
Keywords: apexogenesis, diagnosis, endodontic treatment, immature tooth, pulp
necrosis, root development.
Received 5 June 2009; accepted 20 September 2009
Introduction
Traumatic dental injuries may jeopardize pulp survival in affected teeth. Luxation injuries
and avulsions are the most frequent traumatic causes for pulp necrosis resulting in the
need for endodontic treatment. In immature teeth, preservation of pulp vitality is crucial
for continued dentine formation and root development. Thus, treatment strategies for the
immature young dentition are important for the long-term prognosis of teeth and should
aim at preserving pulp vitality to secure tooth maturation and root development. In
immature teeth with pulp necrosis and bacterial infection, the long-term prognosis is
related to the stage of root development and the amount of root dentine present at time of
injury (Cvek 1992).
In teeth with an open apex, luxation may occur without disruption of the pulpal blood
and nerve supply. Moreover, pulp revascularization and repair will more readily occur in
teeth with a wide apical foramen (Andreasen et al. 1986). Consequently, a more
conservative treatment approach is recommended during follow-up of traumatized
immature teeth. Bacterial control is important and decisive to avoid infection resulting in
arrested root development.
The repair potential of immature teeth following luxation injuries is reflected in a more
favourable outcome after injury compared to mature teeth (Andreasen & Pedersen 1985).
Two factors have been found to be significantly related to the development of pulp
necrosis; the type of luxation injury and stage of root development (Andreasen 1970). The
frequency of pulp necrosis after luxation injuries in the permanent dentition has been
found to range from 5% to 59% (Andreasen & Andreasen 2007). Concussion and
subluxation injuries seldom results in pulp necrosis in immature teeth, whereas pulp
necrosis occurs in approximately 5% of teeth with complete root development
(Andreasen & Pedersen 1985). Following more serious luxation injuries, such as extrusive
and lateral luxation, approximately 10% of teeth with an open apex will develop pulp
necrosis (Andreasen et al. 1987, Andreasen 1989).
From previous studies, there appears to be a general agreement that lack of pulp
sensitivity or coronal discolouration alone is not sufficient diagnostic criteria to justify pulp
necrosis (Magnusson & Holm 1969, Bhaskar & Rappaport 1973, Zadik et al. 1979,
Jacobsen 1980). Periapical radiolucency has so far been considered to be the ‘safe’ sign of
pulp necrosis. However, investigations have questioned the validity of this assumption
(Andreasen 1989). In teeth with incomplete root formation, the radiographic interpretation
of the periapical area may be confused by the un-mineralized radiolucent zone surrounding
the dental papilla (Andreasen 1989). Even the concomitant presence of all three classical
signs of pulp necrosis; coronal discolouration, loss of pulp sensitivity and periapical
radiolucency, can in rare cases be followed by pulp repair (Andreasen 1989).
Pulp necrosis should be confirmed by sensitivity tests, keeping in mind that false
positive or negative result may be recorded. Pulp diagnosis is decisive for appropriate
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treatment and long-term prognosis. Infected teeth left untreated (false positive) might be
lost because of infectious related resorptions (Fuss et al. 2003). On the other hand, the
initiation of endodontic treatment of vital immature teeth (false negative) will impair
dentine formation and root development, thus substantially reducing the chances of long-
term survival (Cvek 1992).
The aim of this report is to present a case where a traumatized, immature tooth still
showed capacity for further root development and apexogenesis even after endodontic
instrumentation of the root canal. The treatment was based on an inaccurate pulp
diagnosis.
Case report
A 9-year-old boy was referred from the public dental health service to the clinic for post-
graduate endodontic training, University of Bergen, Bergen, Norway. The referral was
based on the following information: the maxillary central incisors were subjected to a
traumatic dental injury during ice-skating. Immediately after the accident, the patient was
examined at a public dental emergency clinic where concussion of the maxillary central
incisors was diagnosed. No emergency treatment was performed, and the patient was
referred to the public dental health service for follow-up. One month later, the patient
claimed weak and diffuse symptoms in the maxillary anterior region. An appointment at
the public dental health service was organized. Based on radiographic and clinical findings,
apical periodontitis was diagnosed (Fig. 1a). Vital pulp tissue with normal bleeding was
recorded when the pulp chamber was accessed. The root canal was then instrumented to
size 100 and irrigated with sodium hypochlorite 0.5% (Fig. 1b). According to the patient
record, there was profound bleeding with difficulties applying calcium hydroxide paste in
the instrumented root canal.
Following the referral, a clinical and radiographic examination was performed 1 week
after initial endodontic treatment. Tooth 21 was free from symptoms. Radiographs
revealed an immature tooth with incomplete root length, thin dentinal walls and a wide
open apex (Fig. 2a). No radiographic signs of apical breakdown were recorded. A radio-
(a) (b)
Figure 1 Radiographs taken 1 month after subluxation of the anterior teeth. The diagnosis apical
periodontitis form an infected root canal was set based on radiograph (a). The instrumentation length
was set according to radiograph (b), followed by instrumentation of the root canal to reamer ISO 100.
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International Endodontic Journal, 43, 76–83, 2010 ª 2010 International Endodontic Journal78
opaque material (calcium hydroxide) was visible only in the coronal part of the root canal
(Fig. 2a). Based on the radiographic and clinical findings, the diagnosis ‘previous initiated
root canal treatment’ (vital tooth) was recorded. Because of the insufficient introduction of
calcium hydroxide into the root canal, a conservative approach was decided upon, thereby
allowing observation of any further continued root development. Completion of the
endodontic treatment at this stage would result in a weak tooth with poor prognosis. The
patient and his parents were informed and agreed to the proposed treatment strategy.
At follow-up, 1 month later, (Fig. 2b) the tooth was still free of symptoms. The colour of
the tooth was normal, and signs of slight growth of the root could be noticed from the
radiographs.
Four months later, (Fig. 2c) the radiographs showed continued root formation and
thickening of the dentinal walls. The calcium hydroxide dressing was removed with
sodium hypochlorite 0.5%. A calcified bridge of hard tissue was verified in the cervical 1/3
of the root by visual inspection through a dental surgical microscope. The coronal part of
the tooth was dried and packed with calcium hydroxide paste, and IRM� was placed as a
temporary filling (Fig. 3a).
The tooth was then followed with radiographic examination every 3rd month for the
following 15 months (Figs 2d–f). Continued root formation and apical closure were
registered. No clinical symptoms were recorded. Finally, a 2–3 mm thick plug of white
mineral trioxide aggregate (MTA, Angulus) was placed in contact with the hard tissue
bridge (Fig. 2g, and the access cavity filled with bonded composite (Tetric flow/Tetric
Ceram, Ivoclar Vivadent AG, Liechtenstein). Follow-up was performed 7 months later
(a) (b) (c) (d)
(e) (f) (g) (h)
Figure 2 Radiographs showing continued root development during a 2 year follow-up period. (a)
Radiograph taken at the first appointment shows an immature tooth with incomplete root length, thin
dentinal walls and an open apex. Calcium hydroxide is visible in the coronal part of the root canal. (b)
One month later, slight growth of the root and mineralization in the cervical area is noted. (c–f)
Continued root formation and apical closure is observed during 15 months follow-up. (g) Radiograph
taken after application of mineral trioxide aggregate (MTA). (h) Final follow-up 2 years after the first
appointment. Bonded composite is used to seal the access cavity.
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ª 2010 International Endodontic Journal International Endodontic Journal, 43, 76–83, 2010 79
(Fig. 2h). The tooth was free from symptoms, and radiographs showed further root
development. Slight discolouration was noted in the cervical area (Fig. 3b).
Discussion
This case report illustrates the repair potential of a tooth with incomplete root formation.
The capacity for continued root development was preserved after traumatic injury and
treatment complications. Furthermore, it underlines the importance of an accurate pulp
diagnosis and a proper plan for treatment and follow-up of these teeth.
Development of pulp necrosis after dental trauma can be associated with symptoms
such as spontaneous pain or tenderness to percussion (Andreasen 1989). From previous
studies, it appears to be a general agreement that lack of pulp sensitivity (Magnusson &
Holm 1969, Bhaskar & Rappaport 1973, Zadik et al. 1979, Jacobsen 1980) or coronal
discolouration alone is not sufficient to justify pulp necrosis (Magnusson & Holm 1969,
Jacobsen 1980). Diagnosing traumatized, immature teeth may be a challenge to the
dentist, as demonstrated in the present case. The radiolucent zone surrounding the apical
dental papilla was interpreted as a periapical lesion from an infected necrotic pulp. The
initial endodontic treatment was based on misinterpretation of clinical and radiographic
findings. Although the root canal was instrumented to size 100, some odontoblasts and
pulp cells may have been left intact. The incomplete administration of calcium hydroxide
paste into the pulp canal was in this sense favourable. In addition, the copious solid
bleeding from the pulp tissue may have favoured reorganization of surviving pulpal tissue.
Different traumatic injuries may interfere with the pulpal neurovascular supply and
give rise to various defence and repair responses, ranging from localized or generalized
pulpal inflammation, tissue regeneration, reparative dentine formation or bone metapla-
sia and internal resorption, as well as pulp necrosis with or without bacterial
(a)
(b)
Figure 3 Clinical situation before placement of mineral trioxide aggregate (MTA) (a). Follow-up
7 months after application of white MTA showing light grey discolouration in the cervical area of tooth
number 21 (b).
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International Endodontic Journal, 43, 76–83, 2010 ª 2010 International Endodontic Journal80
contamination (Andreasen et al. 1988). A common pattern of the repair process is
reorganization of the damaged pulp tissue, formation of new vessels and recruitment of
pulp progenitor cells to the injured area, whereby a tissue loss is gradually replaced by
new tissue (Andreasen et al. 1988).
The character of the pulpal responses varies, not only according to the type and severity
of the traumatic injury, but also on the origin of the progenitor cells involved in the process.
Tissue repair may be initiated from progenitor cells of pulpal origin, from periodontal
tissues or from a combination of the two. If damaged pulp tissue is renewed by progenitor
cells of pulpal origin, differentiation of new odontoblasts, forming reparative dentine, may
occur. The new dentine formed may even be re-innervated by sensory nerves (Kvinnsland
et al. 1991). In contrast, when the damaged tissue is restored by cells from periodontal
tissues, periodontal stem cell progenitors may invade the root canal resulting in collagen
and hard tissue formation. In the present case, continued normal root formation was seen,
indicating repair based on cells of pulpal origin.
If a pulp exposure site is covered with a suitable capping material, limiting or
preventing bacterial contamination, a hard tissue barrier is normally established (Watts
& Paterson 1981, Cvek 2007). In the present case, radiographic examination indicated
the presence of calcium hydroxide paste only in the coronal part of the tooth. The
initial application of calcium hydroxide paste may have initiated the formation of a hard
tissue bridge in the canal entrance. The type and quality of this hard tissue bridge
cannot be evaluated by radiographic or clinical inspection. The cells responsible for the
formation of this hard tissue barrier include mesenchymal, paravascular cells that
differentiate into odontoblasts like cells (Ruch 1945, Sveen & Hawes 1968, Zach et al.
1969, Feit et al. 1970, Luostarinen 1971, Yamamura 1985). Hard tissue bridges formed
after calcium hydroxide application are often incomplete with multiple tunnel defects
that may lead to micro leakage (Cox et al. 1996). As a consequence, a bacteria tight
seal should be established over the bridge. In this case, white MTA followed by
bonded composite was used for this purpose. Discolouration of the tooth because of
the use of Grey MTA in the cervical region has been reported (Glickman & Koch 2000).
As an attempt to overcome this problem, white MTA has recently been introduced.
The major difference between grey and white MTA is the concentration of Al2O3, MgO
and, especially, FeO, with the observed values for each of these oxides being
considerably lower in the white MTA (Asgary et al. 2005). Differences in the observed
FeO concentration are thought to be primarily responsible for the variation in colour of
the white MTA when compared to gray MTA. The present case showed slight grey
discolouration even after filling with white MTA in the cervical part of the root canal,
indicating that the aesthetic properties of MTA are not completely solved. Although the
cervical discolouration of the crown was noted, it was accepted by the patient and his
parents.
Conclusion
Special care should be taken during the evaluation and follow-up of traumatized immature
teeth, and more then one sign indicating pulp necrosis should be recorded before
endodontic treatment is started. In this case, the apical un-mineralized apical area
surrounding the developing dental papilla was unintentionally interpreted as apical
pathosis from an infected necrotic pulp. An observation strategy is recommended and no
intervention should be carried out before pulp necrosis is properly verified. Initially, a
frequent follow-up regime should be used for periodontal injuries at high risk of
inflammatory resorption to allow early identification of this pathology. The long-term
prognosis of immature teeth is dependent on continued root formation.
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Disclaimer
Whilst this article has been subjected to Editorial review, the opinions expressed, unless
specifically indicated, are those of the author. The views expressed do not necessarily
represent best practice, or the views of the IEJ Editorial Board, or of its affiliated Specialist
Societies.
References
Andreasen JO (1970) Luxation of permanent teeth due to trauma. A clinical and radiographic follow-up
study of 189 injured teeth. Scandinavian Journal of Dental Research 78, 273–86.
Andreasen FM (1989) Pulpal healing after luxation injuries and root fracture in the permanent dentition.
Endodontics and Dental Traumatology 5, 111–31.
Andreasen FM, Andreasen JO (2007) Luxation injuries of permanent teeth: general findings. In:
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Copenhagen: Blackwell Munksgaard, pp. 372–97.
Andreasen FM, Pedersen BV (1985) Prognosis of luxated permanent teeth – the development of pulp
necrosis. Endodontics and Dental Traumatology 1, 207–20.
Andreasen FM, Zhijie Y, Thomsen BL (1986) Relationship between pulp dimensions and development
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Andreasen FM, Zhijie Y, Thomsen BL, Andersen PK (1987) Occurrence of pulp canal obliteration after
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Andreasen JO, Kristerson L, Andreasen FM (1988) Damage of the Hertwig’s epithelial root sheath:
effect upon root growth after autotransplantation of teeth in monkeys. Endodontics and Dental
Traumatology 4, 145–51.
Asgary S, Parirokh M, Eghbal MJ, Brink F (2005) Chemical differences between white and gray
mineral trioxide aggregate. Journal of Endodontics 31, 101–3.
Bhaskar SN, Rappaport HM (1973) Dental vitality tests and pulp status. Journal of American Dental
Association 86, 409–11.
Cox CF, Subay RK, Ostro E, Suzuki S, Suzuki SH (1996) Tunnel defects in dentin bridges: their
formation following direct pulp capping. Operative Denistryt 21, 4–11.
Cvek M (1992) Prognosis of luxated non-vital maxillary incisors treated with calcium hydroxide and
filled with gutta-percha. A retrospective clinical study. Endodontics and Dental Traumatology 8,
45–55.
Cvek M (2007) Endodontic Management and the use of Calcium Hydroxide in Traumatized Permanent
Teeth. In: Andreasen JO, Andreasen FM, Andersson L, eds. Traumatic Injuries to the Teeth, 4th
edn. Copenhagen: Blackwell Munksgaard, pp. 598–647.
Feit J, Metelova M, Sindelka Z (1970) Incorporation of 3H thymidine into damaged pulp of rat incisors.
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Fuss Z, Tsesis I, Lin S (2003) Root resorption – diagnosis, classification and treatment choices based
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Glickman GN, Koch KA (2000) 21st-century endodontics. Journal of American Dental Association
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Jacobsen I (1980) Criteria for diagnosis of pulp necrosis in traumatized permanent incisors.
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Kvinnsland I, Heyeraas KJ, Byers MR (1991) Regeneration of calcitonin gene-related peptide
immunoreactive nerves in replanted rat molars and their supporting tissues. Archives of Oral Biology
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Luostarinen V (1971) Dental pulp response to trauma. An experimental study in the rat. Suomi
Hammaslaak Toim 67(Suppl 2), 3–74.
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Ruch J (1945) Odontoblast differentiation and the formation of the odontoblast layer. Journal of Dental
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CASE REPORT
Non-resolving periapical inflammation:a malignant deception
D. Saund, S. Kotecha, J. Rout & T. DietrichBirmingham Dental Hospital, University of Birmingham, Birmingham, UK
Abstract
Saund D, Kotecha S, Rout J, Dietrich T. Non-resolving periapical inflammation: a malignant
deception. International Endodontic Journal, 43, 84–90, 2010.
Aim To report a case of oral non-Hodgkin’s lymphoma with a delayed diagnosis.
Summary Non-Hodgkin’s lymphoma of the oral cavity is an uncommon but important
condition. Early diagnosis is complicated when the presenting signs and symptoms are
similar to those of odontogenic infections. This report describes the case of a 38-year-old
female patient who presented to her dentist complaining of pain in her upper jaw.
Subsequent dental treatment, including extraction, root canal treatment and apicectomy
including biopsy were carried out by the patient’s dentist and local dental hospital. Nine
months elapsed before a more extensive surgical exploration established a diagnosis of
lymphoma.
Key learning points
• To appreciate the importance of recognizing discrepancies between the clinical
scenario and histopathological findings.
• To appreciate subtle radiographic changes that may accompany malignant disease of
the jaw bones.
• To appreciate the need for early referral when a patient’s symptoms do not
satisfactorily respond to conventional dental therapies.
• To appreciate lymphoma should be considered in the differential diagnosis of non-
healing periapical inflammation and non-healing socket.
Keywords: lymphoma, non-healing socket, periapical infection.
Received 16 December 2008; accepted 7 September 2009
Introduction
The incidence of non-Hodgkin’s lymphoma (NHL) has increased by over 50% in the
20-year period between 1986 and 2005 (Cancer Research UK 2008a). NHL now accounts
for 4% of all malignant neoplasms in the UK (Cancer Research UK 2008b). It is the third
most common malignancy to affect the head and neck region, after squamous cell
doi:10.1111/j.1365-2591.2009.01644.x
Correspondence: Daniel Saund, Birmingham Dental Hospital, St Chad’s Queensway, Birming-
ham, B4 6NN, UK (e-mail: [email protected]).
International Endodontic Journal, 43, 84–90, 2010 ª 2010 International Endodontic Journal84
carcinoma and salivary gland tumours (Barker 1984). NHL can be classified according to
the cell of origin into T-cell or B-cell lymphoma; the latter being more common in the oral
cavity (Neville et al. 2009). The incidence of NHL is rare in patients under the age of 40,
with approximately 70% of all cases being diagnosed in people over 60 years. It
predominately occurs in lymph nodes but 20–40% arise in extra-nodal sites (Neville et al.
2009). The gut is the commonest site for extra-nodal lymphoma, but bone and the mouth
are other frequently affected sites.
Non-Hodgkin’s lymphoma can present in a number of different forms within the oral
cavity, the more frequent being palatal (Tomich and Shafer 1975) and gingival swellings
(Spatafore et al. 1989, Payne and al-Damouk 1993). It is reported that 36–45% of oral NHL
can affect the jaw bones (Keyes et al. 1988). The initial diagnosis of oral lymphomas can
be challenging as they may resemble pyogenic granulomas, ulcers, sinusitis (Spatafore et
al. 1989), a non-healing socket (Thomas et al. 1991) or mimic an acute dental abscess
(Spatafore et al. 1989, Rog 1991, Payne & al-Damouk 1993). Patients may complain of
non-specific pain, which may be misdiagnosed as periapical inflammatory disease.
This report presents a case of malignant NHL which was originally diagnosed and
treated as an odontogenic infection.
Case report
A 38 year-old Afro-Caribbean female referred herself to the Birmingham Dental Hospital,
UK primary care unit in November 1998. She described a 6-month history of a
spontaneous intermittent dull ache in the upper left canine region. There was no
disturbance to her sleep pattern. She had visited her GDP on several occasions over the
preceding 6 months without resolution of her discomfort, despite extraction of tooth 22
and root canal treatment to teeth 23 and 24. Her medical history was unremarkable. She
was a non-smoker and drank 2 units of alcohol per week.
On clinical examination, there was no lymphadenopathy of the head and neck region.
An intra oral inspection revealed a non-healing socket where the 22 had been removed
4 months previously. The buccal sulcus was tender to palpation over the apex of the 23,
but no swelling or ulceration was apparent. The 23 and 24 were not mobile and were non-
tender to percussion. She had a good standard of oral hygiene and there was no evidence
of periodontal disease.
A periapical radiograph revealed a radiolucency and a dense radiopaque foreign body,
probably amalgam, at the base of the 22 socket (Fig. 1). The 23 and 24 (Fig. 2) had
satisfactory root canal fillings with no associated apical radiolucencies and good
periodontal support. She was prescribed a course of amoxicillin and reviewed a week
later. As her symptoms had not improved the 22 socket was surgically investigated.
During this procedure, granulation tissue was removed but not submitted for histopa-
thology.
Curettage of the 22 socket and a further two courses of amoxicillin failed to resolve her
symptoms so the 23 and 24 region was investigated and an apicectomy performed on
both teeth. Soft tissue was curetted from around the apices of 23 and 24 resulting in an
oro-antral communication due to loss of bone. The histology revealed chronically inflamed
granulation tissue.
Three months after her presentation to the dental hospital and 9 months following
onset of her symptoms, radiographic follow-up revealed destructive bony changes (Fig. 3).
The 23 and 24 apical radiolucency had increased in size, showed perforation of the cortical
bone and loss of the bony antral floor (Fig. 3).
As a consequence, a further biopsy was performed, which revealed extensive soft
tissue replacement of the left maxillary alveolar process extending from close to the
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palatal midline, posteriorly to the left maxillary buttress and superiorly towards the floor of
the nose. Extraction of the 23 led to the simultaneous removal of the 24 encased in a
loose segment of surrounding maxillary alveolus.
The histology of the soft tissue component again showed a granulomatous foreign
body reaction consistent with a periapical granuloma, whereas examination of the
tissue block containing bone and teeth revealed a dense infiltrate of cells that had the
appearance of malignant lymphoid cells. A preliminary diagnosis of lymphoma was
made and the patient referred for further assessment and management. A comput-
erized tomography (CT) scan showed destruction of the left maxillary alveolus (Fig. 4).
Further biopsy confirmed a diagnosis of non-Hodgkin’s lymphoma of the left maxilla.
Additional investigations showed that there were no other lesions elsewhere in the
body and thus the disease was classified stage 1AE (single extranodal site without
systemic signs of disease). She was treated with radiotherapy to the left maxilla and
chemotherapy. Seven years later the patient has no signs of recurrence and remains
under annual review.
Discussion
Inflammatory processes of the jaws may present in an indolent manner or show a more
aggressive behaviour. Typically odontogenic inflammation results in pain, widening of the
periodontal ligament space, and the development of a periapical radiolucency that is
usually well defined. Occasionally developmental anomalies, metabolic diseases and
malignancies can resemble dental inflammatory disease but do not respond to root canal
treatment or tooth extraction. In this situation the clinician should review the accuracy of
the diagnosis so that the appropriate treatment is not delayed.
Figure 1 Periapical radiograph taken at presentation of UL2 socket demonstrating foreign body.
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The presented case and several others in the literature have demonstrated that
extranodal lymphoma of the jaws may initially present, particularly in the early stages, with
unspecific signs and symptoms mimicking periapical disease (Slootweg et al. 1985,
Macintyre 1986). Lymphomas can become secondarily infected and present with swelling
mimicking a dental abscess (Rog 1991, Bavitz et al. 1992, Ardekian et al. 1996). The initial
clinical impression of inflammatory disease was supported when antibiotic therapy
appeared to reduce symptoms (Keyes et al. 1988). Whilst many malignant lesions are
easily recognized there are situations when they resemble other conditions. Although
Figure 2 Periapical radiograph taken at presentation showing root fillings UL34 and periradicular
bone.
Figure 3 Periapical radiograph taken 3 months after presentation showing destructive features with
cortical bony destruction above UL3.
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certain clinical features such as increased tooth mobility in the absence of advanced
periodontal disease and neurosensory disturbances may point towards non-odontogenic
disease, they may not be present initially (Gusenbauer et al. 1990). Similarly, radiographs
used to investigate dental disease may demonstrate findings such as poorly defined or
‘moth-eaten’ osteolytic lesions (Macintyre 1986), root resorption and erosion of crestal
bone, which are not typical for odontogenic lesions. However, destructive radiographic
changes may not be evident in slow growing lymphomatous lesions of the jaws (Keyes
et al. 1988, Rog 1991).
Malignant disease involving bone can resemble periapical inflammatory disease
particularly when the latter is infected changing its margin so it is less well defined.
Periapical inflammation is common whilst lymphoma in the jaws is not thus one tends not
to consider it in the diagnosis. It is important to review the clinical features and
radiological findings, and when these are unusual the diagnosis needs to be reconsidered
rather than persisting with inappropriate treatment. In addition, early referral to a
secondary setting for specialist opinion must always be considered. However, cases such
as the one presented here have to be cautiously interpreted with respect to missed
clinical and radiographic signs, as post-hoc interpretation may be misleading because
primary manifestation of lymphoma or other malignancies as periapical pathology is
uncommon. Therefore, a significant proportion of cases presenting with one or more of
the ‘atypical’ signs and symptoms discussed above may still represent odontogenic
pathologies.
Whilst the authors cannot comment on the indications for, and the sequence of
treatment undertaken by the general practitioner during the 6-month period prior to the
patient’s attendance in the hospital, it is quite clear that several therapeutic attempts
aimed at what was thought to be an odontogenic problem had failed. When initially seen
at our clinic, the non-healing extraction socket was attributed to the foreign body visible
on the radiograph and surgically revised without obtaining any material for histopath-
ological examination. Although an unlikely cause for the patient’s symptoms, it is not
unreasonable to remove a foreign body from a non-healing socket. However, the long
history and failure to respond to previous treatment should have raised the suspicion
that the condition was not infective and a tissue sample for histopathological
examination should have been retrieved (Rog 1991). In the present case it is however
unclear if this would have resulted in an earlier diagnosis, particularly when the
Figure 4 Axial CT image showing erosion of left maxillary alveolus following diagnosis of lymphoma.
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subsequent histology suggested an inflammatory process and the age of the patient was
younger than one expects for lymphoma.
Histologically, the distinction between lymphoma and periapical inflammation is often
challenging, and as in this and other cases, lymphoma has been interpreted as being
inflammatory in nature (Keyes et al. 1988, Richards et al. 2000). These difficulties have
been attributed to inadequate biopsy specimens and poor handling of the tissue by the
clinician leading to ‘crush artefact’ which obscures the fine cytological detail needed to
distinguish between benign and malignant lymphocytes. It is often difficult to obtain an
adequate tissue sample because of the close location to roots (Wannfors and Hammar-
strom 1990). To increase the chances of accurate diagnosis large specimens represen-
tative of the tumour are required (Rog 1991). One biopsy may be insufficient to make a
diagnosis and re-biopsy of non-healing lesions including bone within the sample may be
required. The diagnostic difficulty increases when lymphomas become inflamed,
obscuring the neoplastic nature of the infiltrate (Wright and Radman 1995). Indeed, the
soft tissue samples retrieved during the course of treatment were found to be consistent
with a chronic inflammatory lesion. The histopathological diagnosis of lymphoma was
made from the hard tissue block accidentally retrieved during the extraction of the
associated teeth. This illustrates that, in order to obtain a correct diagnosis earlier, a block
biopsy of the affected bone may have been required to yield the true nature of the disease
process.. However, this constitutes a rather invasive, if not destructive procedure, and
given that lymphoma is extremely rare, adoption of a practice of ‘early block biopsy’ would
result in unnecessary morbidity in many cases. However, in light of diagnostic difficulties
with histopathological examination and plain film radiography earlier referral for more
advanced imaging techniques such as computed tomography or magnetic resonance
imaging should have been considered.
Over the course of her treatment, the patient received three courses of antibiotics
without resolution of her symptoms. Antibiotics have no role in the treatment of persistent
non-healing sockets. Lymphomas and other non-odontogenic diseases may become
secondarily infected. In this situation a reduction of symptoms with antibiotic treatment
may delay proper diagnosis (Keyes et al. 1988).
Although extranodal lymphoma of the jaws is uncommon, perhaps with the increasing
incidence of HIV infection (UNAIDS 2008), a continued increase in the incidence of
lymphoma will be observed. As demonstrated, lymphoma may masquerade as common
dental inflammatory disease and clinicians should be alert to the possibility of sinister
pathology. In the study by Maxymiw et al. 2001 a high percentage of patients with NHL
had dental symptoms. These cases often demonstrate recurrent or protracted disease
patterns, as seen in this case with a delay of 9 months before making the correct
diagnosis. This is longer than the average 2.5 months between presentation and
treatment reported in other cases (Gusenbauer et al. 1990). NHL of the head and neck
has a good prognosis with a median survival rate of 10–15 years but the prognosis is
improved with early diagnosis (Payne & al-Damouk 1993).
Conclusion
Despite its rare occurance, dentists must consider lymphoma in the differential diagnosis
of pain, swelling, ulceration and non-healing periapical inflammation. In general, dentists
should have a high index of suspicion for lesions (including periapical lesions) that do not
respond to conventional therapy or appear unusual in other ways and as such have a role
in early diagnosis and prompt referral of patients for specialist secondary care. Finally, the
possibility of false negative biopsy results must be considered and referral to specialist
care may be warranted even in a case of a negative initial biopsy result.
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Disclaimer
Whilst this article has been subjected to Editorial review, the opinions expressed, unless
specifically indicated, are those of the author. The views expressed do not necessarily
represent best practice, or the views of the IEJ Editorial Board, or of its affiliated Specialist
Societies.
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