n
Shaping
Endodontic Canal Preparation:New Developments
Ove A. Peters, DMD MS PhDDiplomate, American Board of Endodontics
January 17, 2013Seattle WAWashington State Association of Endodontists
Shaping
§ Clinical goals! -!antimicrobial efficacy! -!avoid preparation errors
§ Mechanical goals! -!providing space for obturation! -!avoid instrument fracture
§ Where are we standing with this?! -! rotary instruments have brought very significant improvement over the last 2 decades
Shaping Goalsn What is new?
n NiTi properties
n Metallurgy
n Discussion
Shaping
”... the prepared canal should include the original canal; the apical
constriction should be maintained; the canal should end in an apical
narrowing; and the canal should be tapered from crown to apex.“
ESE Consensus Paper 2006
n
n
Shaping
H. Messer
n What is new?
n NiTi properties
n Metallurgy
n Discussion
Shaping
Paqué et al Int Endod J,44:148; 2011
§ Accessory anatomy blocked
Accumulated Debrisn What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Paqué et al Int Endod J,44:148; 2011
nsion Hard Tissue Debris§ Superimposition shows blocked areas in green§ Volume can be quantified
Shaping
Metzger et al, 2010
The Self-Adjusting Filen What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n
Peters et al, 2010
n
Shaping
n
n
Shaping
n
Peters & Paqué, 2011
Shaping
§ Wide canal space: most d roots, bicuspids! -! inadequate shape and insufficient cleaning
Greater Degree Of Difficultyn What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n
Paqué & Peters, 2011
n
Shaping
n
Siqueira et al, 2010
n
Shaping
n
n
Shaping
n The Wave One System
n
Shaping
Yared G (2008)
§ Aim! -! to describe a novel preparation technique using only two instruments
§ Summary-!the technique described begins with negotiation to working length with hand instrument to size .08
! -! the bulk of the shaping is done with a ProTaper F2 (tip size 25)- the ProTaper is oscillated in a ATR electric motor that is programmed to generate reciprocating movements- r.p.m. is set at 400, the angles of rotation are CW 144CCW 72- instrumentation proceeds with very light apical pressure
Canal preparation using only one Ni-Ti rotary instruments: preliminary
observations.
Int Endod J 41: 339-344
n
n
Shaping
§ Discussion! -! the technique presented appears to be effective and safe- the exact settings need to be confirmed and more research is needed
§ Results! -! several cases are presented where curved canals could be prepared with
just one hand and one rotary instruments
Yared G Int Endod J (2008)n
§ Engine-driven! - reciprocating in special motor! - 3 sizes, small (21.06), primary (25.08), large (40.08) - must be single use (plastic ring expands)
n
Shaping
n The Wave One System
n
Shaping
§ Material & Methods! -!20 maxillary molars had db and mb roots instrumented with ProTaper either in continuous rotation or reciprocation (CW140, CCW45 degrees) - micro CT data was acquired and processed for canal transportation assessment (curvature, volume, surface, SMI, in-plane shift - parametric statistics were performed
J Endod 2011, 37:1296-1300
n
Shaping
J Endod 2011, 37:1296-1300
Shaping
Preparation Quality
§ Clinical data! - currently no studies available but case reports and in vitro data is encouraging
§ Overall outcomes ! - no increased incidence or severity of errors
- prepared surface and debris similar
n Introduction
n Physiology
n Microbiology
n Regeneration
§ Conclusion! - Reciprocation is an “...attractive alternative method to prevent procedural errors during root canal shaping”
Baek, 2011
n
Shaping
n
n
Shaping
§ Material & Methods! -!90 curved canals in extracted teeth were carefully randomized - canals were prepared to final size #50 with NiTi hand files, MTwo or ProTaper following manufacturers’ recommendations - micro CT scans were acquired initially and after subsequent preparation steps - prepared perimeters and canal outlines were determined
J Endod 2011, 37:1580-1584
n
Shaping
J Endod 2011, 37:1580-1584
Sequential Enlargement
Shaping
Increased Apical Enlargement
§ Experimental data! - does not lead to more complete preparation but with
less flexible instruments may cause preparation errors
§ Intended to increase efficacy ! - circumferential dentin removal
- prepared canal surface
§ Clinical conclusion! - “...it may be recommended to keep the apical size of curved canals as minimal as possible provided that a sufficient irrigation is feasible.”
El Ayouti, 2011
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Crazy Root Canalsn
n
Shaping
n
Testarelli at al, 2011
n
Shaping
Martensitic Filesn
§ Bendable
100
Tem
pera
ture
[C]
residual deformation
n
Shaping
Heat Treatment after Machiningn
§ not treated § heat-treated (?)
prototypes, heat treated and controls, 2010
§ Surface topography
n
Shaping
J Endod 2011, 37:1293-1295
Shaping
Martensitic Alloys
§ Clinical data! - currently no studies available but case reports and in vitro data is interesting
§ Flexibility! - clearly greater than austentic initially
- under “normal” fatigue condition extended lifespan
Paqué, 2011
§ Conclusion! - need to reconsider fatigue testing norms - not clear how important fatigue is for single use
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Cyclic Fatigue [5mm radius, 90°]n
§ Effect of metal conformation on fatigue lifespan
prototypes, heat treated and controls, 2010
n
Shaping
n Blue™ File Technology§ New raw material! - the degree of shape memory is dependent on NiTi microstructure - this material promises to be much more fatigue resistant and more
Dentsply Tulsa Dental to be released
CuttingEfficienc
y of Conventiona
l and Martensiti
c
Nickel-Titanium
Instruments for C
oronal Flaring
RenataDorne
lles Morgental, DD
S, MS, PhD,*† Fabian
a VieiraVier-Pe
lisser, DDS, MS, PhD
,*
Patr!ıcia Maria Poli Ko
pper, DDS, MS, PhD
,‡ Jos!e Antonio
Poli deFiguei
redo, DDS, MS, PhD
,*
and Ove A.Peters,
DMD, MS, PhD†
Abstract
Introduction: T
his study aimed
at evaluating th
e influ-
ence of rotational sp
eed and numberof uses
on the
cuttingefficienc
y of 4 nickel-titanium
coronalflaring
instruments against
2 substrates, bov
ine dentin and
acrylic blocks.Methods:
BioRaCeBR0, Hy
Flex CM1,
ProFile OS#2, and
ProTaper Sx we
re usedin simulate
d
lateral action against
both substrates at 25
0 and 500
rpm up to 5 times, producing
5 notchesin each block.
Notch areas and
lengthswere me
asured under a s
tereo-
microscope, and
data were compared by using para-
metrictests (a = 0.05).
Results: Against
both
substrates, HyF
lex CM1 and ProFileOS#2 were the
most and the lea
st cutting efficie
nt instruments, r
espec-
tively (P< .05). Ag
ainst acrylic, are
a and length val
ues
at 500 rpm were significantl
y higherthan those at
250
rpm for all brands. A
gainst dentin, s
ignificant differ-
ences were dete
cted between 25
0 and 500 rpm for Hy-
Flex CM1 and Pro
Taper Sx(area) a
nd for BioRace B
R0,
HyFlexCM1, and ProTape
r Sx (length). Regardin
g
cuttingefficienc
y loss, area and length for notc
hes 1
and 2 (first notches) a
nd 4 and 5 (last notches) w
ere
similaragainst
acrylic.Against
dentin,length values
for notches 1 an
d 2 weresignifica
ntly higher than t
hose
for notches 4 an
d 5 in ProFile O
S#2 andProTape
r Sx. A
strong correlation was detected
betweenthe overall
resultsobtained
on acrylic and dentin for area and
length (P < .0001),although
furtheranalysis
showed
that data against
acrylic were a poor pre
dictor of data
againstdentin a
fter repeated use
. Conclusions: H
yFlex
CM1 was the most c
utting efficient in
strument in later
al
action.An increase
in rotational speed
improved the
cuttingefficienc
y. Resultsagainst
acrylicshowed
a high correlation to data against
dentin,but acry
lic
may not bea proper s
ubstratewhen the intention
is
to assess cutting
efficiency loss w
ith repeated use.
(J En-
dod 2013;-:e1–e5)
Key Words
Coronalflaring,
cutting efficiency, marte
nsitic nickel-tita
nium
The introduction o
f nickel-titanium
(NiTi) toendodon
tics (1)significa
ntly changed
the wayroot can
al preparation is
performed. NiTi
rotary instrumen
ts have enabled
clinicians to obta
in tapered prepar
ations with little
or no procedura
l errorseven in
curved canals (2
).
New instrument de
signs, surface, an
d alloy treatments
have been develop
ed over the
years. Thus, sever
al brands are ava
ilable onthe mark
et, and directions
of use for most of
them recommend a cro
wn-downapproac
h. A so-called cor
onal flaring proce
dure is typi-
cally performed b
y more tapered in
struments and is
claimedto be adv
antageous during
the cleaning and s
haping phase of th
e root canal treatm
ent (3).It is com
monly accepted
that suchinstrume
nts should act lat
erally, avoiding th
e dangerzone des
cribed by Abou-
Rass et al (4). Als
o, the crown-down
techniquemay de
crease fracture ri
sks by preventing
a large portion of
an instrument fro
m engagingroot den
tin (5).
NiTi rotary instru
ments should hav
e some desirable
mechanical prop
erties, such
as shaping ability,
flexibility, resistan
ce to breakage, an
d cuttingefficienc
y (6). Different
methodologies ha
ve beenused to e
valuate the cuttin
g efficiency of end
odonticinstru-
ments, such as weight l
oss analysis(7–9),
profilometry (10, 11
), andmicro–
computed tomogra
phy (6). Moreo
ver, several subs
trates have been
used for such
purpose: human
dentin (9), bovi
ne bone(6, 10–1
2), andacrylic o
r plasticblocks
(7, 8, 13–18).
It appears that t
here isno consens
us regarding the
most adequate
criteria to assess
cutting efficiency
of endodontic ins
truments. Howeve
r, in principle,
the quantification of mater
ial removed in a specific
time seems arational
way to
determine cutting
efficiency.
Despite the exten
sive literature, th
ere is a lack of in
formation about
the behavior
of NiTicoronal
flaring instrume
nts related to lateral c
utting action. Sev
eral design
factors may affect
cutting efficiency
of rotaryinstrume
nts (6),but the
influence of
rotational speed
and numberof uses
on this property ha
s yet tobe investiga
ted
further.Thus, th
e aims of this stu
dy wereas follow
s:
1. To compare th
e cuttingbehavior
of 4 NiTi rotary i
nstruments in lat
eral action
2. To compare 2
differentsubstrate
s
3. To analyzethe influ
ence ofrotationa
l speedand number
of usesin the cutti
ng
efficiency
From the *Departmen
t of Endodontics
, Schoolof Denti
stry, Pontifical Ca
tholic University
of Rio Grande d
o Sul, Porto Alegre,
Brazil;†Arthur A
. Dugoni School
of
Dentistry, Unive
rsity of the Pacifi
c, San Francisco,
California; and
‡Department of En
dodontics, Schoo
l of Dentistry, Fed
eral University of
Rio Grande do Su
l, Porto Alegre,
Brazil.Renata D
ornellesMorgenta
l was supported
by MEC/CAPES (Brazil
ian Federal Agen
cy for Support an
d Evaluation of G
raduateEducatio
n) as anexchang
e scholarship
at the University
of the Pacific, A
rthur A.Dugoni
School of Dentis
try.
Addressrequests
for reprints to Dr
Renata Dornelles
Morgental, Pontifi
cal Catholic Univ
ersity ofRio Gran
de do Sul – PUCR
S, Av. Ipiranga 6
681, Pr!edio 6, 9
0619-900
Porto Alegre, RS
, Brazil.E-mail a
ddress:remorge
0099-2399/$ - s
ee frontmatter
Copyright ª 2013 Am
erican Associatio
n of Endodontist
s.
http://dx.doi.org/
10.1016/j.joen.2
013.08.016
Basic Research—Technolo
gy
JOE — Volume-, Numbe
r -, - 2013
Cutting Efficacy fo
r Coronal Flaring
1
n
Shaping
§ Cutting efficacy! -!was highest in martensitic instruments used in lateral action (orifice modification)
n
Shaping
The Vortex Systemn
Shaping
ProFile Vortex Rotariesn What is new?
n NiTi properties
n Metallurgy
n Discussion§ Sizing! -!similar to ProFile, .04 & .06 tapers, #15 to #50 tips! -!offers sizes for many cases and shapes
§ Benefits and limitations! -!supposedly more cutting efficient! -!M-wire may result in better fatigue resistance
§ Research! -!Vortex may be the successor to GT/ProFile - there is limited published research on this file
Rhodes et al 2011Gao et al 2010
n
Shaping
ProTaper Next
§ Clinical “feel”! -!brushing motion preferred! -! fairly safe instrument re.: breakage
§ Research data! - shaping potential good - not a minimal invasive instrument - fatigue-resistant, low torque when cutting apically
§ Clinical outcomes! -!no data at this point
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Shaping Assessmentn What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Enlargement to #25, Paqué & Peters, unpublished
Example of CT Data
n
Shaping
Summary of CT Data
§ Minimal dentin thickness! -!0.60±0.18mm (X2), 0.55±0.17mm (X3)! -! initial dentin thickness ~ 1.0mm
§ Uninstrumented area! - 16.4±7.4%, range 8-29%, apical 23.2±10.7% (to X3) - very good values in small curved canals
Paqué & Peters, 2013 AAE Meeting
§ Canal transportation! -!70 to 120µm in apical and middle third
Paqué & Peters, unpublished
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Torque Testsn What is new?
n NiTi properties
n Metallurgy
n Discussion
In Vitro Assessment of T
orque and Force
Generated by
Novel ProTaper
Next Instrument
s duringSimulate
d Canal
Preparation
ErikaS.J. Per
eira, DDS, MS,*
† Rupinderpal
Singh,DDS,*
Ana Arias,DDS, P
hD,*
and Ove A.Peters,
DMD, MS, PhD*
Abstract
Introduction: T
he purpose of t
his study was to
assess
torque and force for simulated canal pr
eparation with
a new root canalinstrume
nt, ProTaper Next.
Methods:Six sets of ProTape
r Next Instruments
(X1–X5)were us
ed to prepare 36
artificialcanals. F
iles
were dividedinto 6 groups.
Different setting
s of rota-
tions per minute
(250, 300, and 3
50 rpm)and num
bers
of in-and-out m
ovements to rea
ch working leng
th (3 or
4 insertions [ins
]) were applied in
each group (250
rpm/
3 ins, 250 rpm/4
ins, 300rpm/3 in
s, 300 rpm/4 ins,
350
rpm/3 ins, and350 rpm/4 ins) by u
sing an automated
torque bench. Peak torques
(Ncm) as well a
s positive
and negativeforces (N) wer
e registered. Analy
sis of
varianceand Tuk
ey posthoc test
s were applied. P
relim-
inary data for angle and stationa
ry torqueat failur
e
were also obtainedand compare
d with peak torque
for eachinstrume
nt. Results: Si
gnificant differe
nces
in peak torque (P < .0001),positive
force (P < .002),
and negative for
ce (P < .0001) were foun
d for ProTaper
Next instrument
s overall. X2 sho
wed thehighest
torque
with allsettings
. X5 showed the
highestpositive
force
in all groups. X1 and X2 showed
the highest nega
tive
forces for all gro
ups except for
350 rpm/4 ins. Signifi-
cantly lower torque(P < .0001)
and positiveforce
(P < .007) were mea
sured in the group 350 rpm/4 ins
for all instruments except
for X4. In contrast, X1
showeda significa
ntly lower negative
force for 350
rpm/4 ins. Torque at failure
according to America
n
Dental Associatio
n no. 28/ISO 36030-1
was lower for
X1, X2,and X3 than torque
during simulated canal
preparation (P < .0001).
Conclusions: Under
the
conditions of this
study, using ProTape
r Next at 350
rpm and with 4 in-and-out moveme
nts resultedin
lowestlevels of peak
torque as well aspositive
and
negativeforces. (
J Endod2013;-
:1–5)
Key Words
Nickel-titanium,
ProTaper Next, t
orque, simulated
preparation
Nickel-titanium (NiTi) ro
tary instruments a
re increasingly us
ed in root canal p
rep-
aration.Developm
ent continues to
design rotaries t
hat render shapi
ng not only
easier and faster
but arealso mo
re likelyto lead t
o improved outc
omes, compared
with stainless ste
el handinstrume
nts (1).However
, despiteincrease
d flexibility and
torsional strengt
h compared with
stainlesssteel ins
truments(2), NiT
i rotaryinstru-
ments still seem
to have arisk of fr
acture inthe clini
cal situation (3,
4).
Failure modes of N
iTi instruments ha
ve beenstudied e
xtensively (3–9).
Flexural
fatigue iscaused b
y repetitive comp
ressive and tensil
e stresses acting o
n outer fibers of
a file rotating in a
curved canal; tor
sional failure occ
urs whenthe tip o
f the instrument
binds, but the sh
ank of the file con
tinues torotate (3
). Shearfracture
of the material
then occurs when
the maximum strength
of the material is
exceeded(7).
The torque gener
ated by arotating
instrument durin
g root canal instr
umentation
dependson the c
ontact area betwe
en the file and th
e canal walls, the
appliedapical
force, instrumen
t diameter, and
preoperative canal vo
lume (10–12). In turn,
mechanical prop
erties ofendodon
tic instruments ar
e affected by a v
ariety offactors
such as size, taper, desi
gn, alloy chemica
l composition, a
nd thermomechanica
l
processes applied
during manufactu
ring (13–15).
It is believed that
there is astrong p
ositive correlation
betweenthe maxi
mum tor-
que an instrumen
t can withstand a
nd its diameter (1
2, 16). It has also
been suggested
that the cross-sec
tional shape of in
struments affects
the stress distribu
tion pattern and
thus their torsion
al resistance (17,
18). Moreover, fl
exural fatigue dev
eloped during
curvedroot can
al shaping may decrease
the torsional resista
nce of endodontic
instruments (12,
19–21).
ProTaper Next is
a novel set of rota
ry instruments th
at are designed w
ith variable
tapers and an off-
centeredrectangu
lar crosssection.
The set includes
5 shaping instru-
ments with overa
ll variable tapers
; at the tip, X1 is
#17/.04,X2 is #2
5/.06, X3is #30/
.075, X4is #40/.0
6, and X5 is #50
/.06. Allthe instr
uments are expec
ted passively to
follow the canal until th
e working length
(WL) isachieved
(22).
Such a singlelength techniqu
e possibly requir
es greater torsio
nal strength of
a given instrume
nt because of gre
ater contact with
the dentin walls
resultingin high
stresseson its en
tire length (11).
However, the syst
em featuresan off-ce
ntered rectan-
gular cross sectio
n, whichis intend
ed to reduce torsi
onal stress on the
instrument (22).
From the *Departmen
t of Endodontics,
University of the
Pacific, Arthur A.
Dugoni School of
Dentistry, San Fr
ancisco,Californ
ia; and†Restorat
ive Dentistry, Fac
ulty of
Dentistry, Unive
rsidadeFederal
de Minas Gerais, Belo
Horizonte, Minas Ger
ais, Brazil.
Supported by th
e Fundac~ao de A
mparo!a Pesqu
isa do Estado de
Minas Gerais (FAP
EMIG), BeloHorizont
e, MG, Brazil, and Pr
"o-Reitoria de Pe
squisa da Univer
sidade
Federalde Minas Ger
ais, BeloHorizont
e, MG, Brazil.
Addressrequests
for reprints to D
r Erika S. J. Pere
ira, Restorative D
entistry,Faculty
of Dentistry, Un
iversidade Fede
ral de Minas Ger
ais (UFMG), Av. P
res. Antonio
Carlos, 6627 – Campus
Pampulha, 31.27
0-901 Belo Hori
zonte, MG, Brazi
l. E-mailaddress:
m
0099-2399/$ - s
ee frontmatter
Copyright ª 2013 Am
erican Associatio
n of Endodontist
s.
http://dx.doi.org/
10.1016/j.joen.2
013.07.014
Basic Research—Technolo
gy
JOE — Volume-, Numbe
r -, - 2013
Torqueand Forc
e with ProTaper
Next1
n
Shaping
§ First published research! -! torque during shaping is low: 1.5 - 3Ncm - higher RPM (300) is better than lower - torque at failure (ISO 3630) is lower than working torque
n
Shaping
0
0.5
1
1.5
2
2.5
3
X1 X2
Peak
Tor
que
[Ncm
]
X1
X2
0.35
0.82
Torque at failure[Ncm]
350 rpm
In-and-out movements
Simulated Canal Preparation
n
Shaping
0
1.5
3
4.5
6
X1 X2
Forc
e [N
]
Simulated Canal Preparation350 rpm
In-and-out movements
n
Shaping
Torque Data in Plastic Blocks
§ Torque during simulated canal preparation! -! range from 1.6 to 2.8Ncm for X1 to X5 - higher compared to fracture torque
§ Torque at failure (ISO3630-1)! - range from 0.35 to 2.87Ncm for X1 to X5 - similar or slightly less to ProTaper Universal
§ Handling parameters! -!comparing rpm, higher speed is better - comparing in-and-out movement, gentle is better
Pereira et al, 2013 AAE Meeting
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Fatigue Datan What is new?
n NiTi properties
n Metallurgy
n Discussion
Weibull plots, Nguyen J Endod accepeted
n
Shaping
Fatigue Data
Weibull plots, Nguyen J Endod accepeted
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n
Shaping
Assessment??
§ WS, #7, 06 § AZ, #14, 06
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Torque Explained§ Torque is lever length times force! -! rotational axis, point of force K
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Fatigue Explained§ Cyclic nature! -! repetitive action below elastic limit (high cycle)! -!sometimes beyond elastic limit (low cycle, <105)
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Fatigue Explained§ Southwest Airlines accident! -! “...jetliner had gone through about 39,000 cycles of pressurizing, generally a count of takeoffs and landings. Cracks can develop from the constant cycle of pressurizing for flight, then releasing the pressure.”
§ 2009 § 2011
n What is new?
n NiTi properties
n Metallurgy
n Discussion
Shaping
www.nitinol.com/nitinol-university/university-resources/
n
Shaping
Cyclic Fatigue in vivon
n
Shaping
Hooke’s Lawn
n
Shaping
Cyclic Fatigue in vitron
§ Effect of pseudoelasticity on fatigue lifespan?
FlexMaster, 5mm radius, 90°, Hübscher et al 2003
n
Shaping
Deformation Mechanisms
Elasticbehavior
Pseudoelasticbehavior
Force
Steel
NiTi
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n
n
Shaping
Nickel-Titanium Components§ austenite (B2)! -! hard, exists at room temperature for most endodontic instruments (with some exceptions)
§ martensite (B19’)! -! ductile, very flexible; trace amounts present in many endodontic instruments at room temperature
§ R-phase (R)! -! ductile, stress- or temperature induced, a pre- martensitic phase that provides shape memory
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Components§ austenite (also found in iron)! -!Austenite, also known as gamma phase iron, is a
metallic non-magnetic allotrope of iron. From about 900
to 1,400°C alpha iron undergoes a phase transition from
body-centered cubic (BCC) to the face-centered cubic
(FCC) configuration of gamma iron, also called
austenite.
wikipedia.org
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Components§ martensite (also found in iron, steel)
! -!Martensite, named after the German metallurgist
Adolf Martens (1850–1914), most commonly refers to a
very hard form of steel crystalline structure, but it can
also refer to any crystal structure that is formed by
diffusionless transformation.
wikipedia.org
- for NiTi martensite is in a monoclinic configuration
and more flexible than austenite
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Nickel-Titanium Components§ R-phase! -!The R-phase transformation is best thought of as a
second (or pre-) martensitic transformation that provides
a small, nearly hysteresis-free shape memory and
superelastic effect that exhibits virtually no degradation
during cycling.
- the name derives from the concept that the crystal
lattice is rhombohedral (may in fact be trigonal)
from Duerig et al 2010
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
The R-Phase
From Otsuka & Ren 2005
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
§ It is a bit obscure, even for a physicist! -!shows up through changes in electrical conductance, heat flow (total energy) or in stress-strain diagrams
from Duerig et al 2007
n What is new?
n NiTi properties
n Metallurgy
n Discussion
The R-Phase
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Shaping
R-Phase Crystal Latticen
from Duerig et al 2010
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Shaping
Nickel-Titanium Properties
Aust
enite
[%]
Temperature
§ Temperature and strain-dependent
§ Transition of crystal phases
n What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
Nickel-Titanium Properties§ Clinical application! -!martensitic phase (at low temperature) is flexible! -!higher flexibility ~ less cutting (=efficiency?)
Aust
enite
[%]
Temperature
n What is new?
n NiTi properties
n Metallurgy
n Discussion
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Shaping
n NiTi Phase Transformation
exothermic
endothermic
From Miyai et al 2006
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Shaping
Transition Temperatures [C°]n
Ms Mf As Af
EndoWave 29 -3.2 -21 37Hero 642 6 -41 -38 9K3 9 -44 -41 5ProFile .06 23 -16 -21 30ProTaper 19 -10 -17 32
coolingcooling heatingheating
From Miyai et al 2006
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Shaping
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Shaping
n NiTi Phase Transformation
auste
nite el
astic martensitic transformation
martensite elastic
martensite plastic
2%4% 2%
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Shaping
Appraisal I§ Thermal processing! -!drawn NiTi wire is work-hardened! -!heat treatment increases flexibility, fatigue resistance! -!downside: cutting ability is lower, high rpm required
§ Martensitic files (e.g., with shape memory)! -!current market share is small! -!martensitic files cannot utilize the pseudoelastic SIM transformation; rely on 2% recoverable strain
§ Hybrid files (e.g., segmental martensitic)! -!small market share! -!maybe a compromise but better?
n What is new?
n NiTi properties
n Metallurgy
n Discussion
Shaping
n What is new?
n NiTi properties
n Metallurgy
n Discussion
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Shaping
What is here already...§ The alloy! -! thermal treatment: M-wire! -!surface treatment: electropolishing, PVD! -!cold treatment, nitrogen ion implantation! -!production process, twisting/stamping vs grinding
§ Intelligent motors! -! torque control is a standard feature! -!may detect individual instruments
§ Modified usage! -!glide path, single-patient use! -!change of sequence, hybrid techniques, etc.
n What is new?
n NiTi properties
n Metallurgy
n Discussion
Shaping
Summary of Current Data§ GTX! - fatigue resistance ↑(p<0.001) compared to stock NiTi
- similar torsional resistanceJohnson et al 2008
§ TF (Twisted File)! - flexibility ↑ compared to same size ProFiles (p<0.05)
- fatigue resistance: TF > K3 = GTX (different sizes)Gambarini et al 2008
§ Comparisons! - fatigue: EndoSequence>ProFile>TF> GTX; .06>.04
- difference not significant for TF vs. ProFile- Fatigue, angle at fracture: GT=GTX; .06>.04
- Multiple usage: GT, GT ↓ angle, torque at fractureKramkowski et al 2009
Kell et al 2009
Larsen et al 2009
n What is new?
n NiTi properties
n Metallurgy
n Discussion
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Shaping
§ Material & Methods! - 100 central maxillary incisors were prepared with either Reciproc, WaveOne, ProTaper or MTwo - teeth were embedded in Technovit, sectioned and observed under a stereomicroscope at 25x magnification - complete cracks were defined as “ a line extending from the root canal wall to the outer surface of the root” - the numbers of complete and incomplete cracks was compared by parametric statistics
Bürklein et al J Endod in press
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Shaping
Bürklein et al J Endod, 39:501;2013
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Shaping
Comparison of 2
Canal Preparati
on Techniques
in the Induction
of Microcracks: A Pilot Stu
dy
with Cadaver M
andibles
Ana Arias,DDS, P
hD, Yoon H. Lee
, BS, Christin
e I. Peters, DM
D, Alan H. Glu
skin, DDS,
and Ove A.Peters,
DMD, MS, PhD
Abstract
Introduction: The purpose
of this pilot study in a
cadavermodel w
as to compare 2 d
ifferentshaping
tech-
niques regarding
the induction of
dentinalmicrocra
cks.
Methods:Three lower in
cisors from each of 6 adult
humancadaver
skulls were randomly distribut
ed into
3 groups: the con
trol group (CG, n
o instrumentation
), the
GT group (GT Profile hand files; Dentsply Tulsa Dental,
Tulsa, OK), and t
he WO group (WaveOne;
DentsplyTulsa
Dental).In the GT group, m
anual shaping in a crown-
down sequence w
ith GT Profile han
d files was perfo
rmed.
In the WO group, P
rimary WaveOne
files were used to
the
workinglength. T
eeth were separa
ted fromthe man
dibles
by careful remova
l of softtissue an
d bone under ma
gnifi-
cation. Roots were sectione
d horizontally at 3, 6,
and
9 mm from the apexusing a l
ow-speed saw. C
olor photo-
graphs at 2 magn
ifications(25! and 40!) were ob
tained.
Three blinded ex
aminersregistere
d the presence of
micro-
cracks (yes/no), e
xtension(incomp
lete/complete), d
irection
(buccolingual/me
siodistal), and location.
Data were
analyzedwith chi-
square tests at P
< .05. Results: Micro-
cracks were foun
d in 50%(CG and GT)
and 66%(WO) of
teeth at 3 mm, 16.6% (CG) and
33.3% (GT andWO) at
6 mm, and 16.6% in all 3 groups at 9 mm from the
apex. There were no significa
nt differences in the inci-
dence ofmicrocra
cks between all g
roups at3 (P = .8), 6
(P= .8), or 9mm (P= 1). All m
icrocracks were in
complete,
started at the pulpal wa
ll, and had a buccolingual dire
c-
tion. Conclusion
s: Within the limitations of this
pilot
study, arelations
hip betweenthe shaping
techniques
(GT handand WaveOne)
and theincidenc
e of microcracks
could not be sho
wn compared w
ith uninstrumente
d con-
trols. (J Endod 20
14;-:1–4)
Key Words
Cadavermandibl
e, GT hand, micr
ocracks,WaveOne
A frequentreason f
or toothloss afte
r root canal treat
ment isvertical r
oot fracture
(VRF) (1, 2). VR
Fs havebeen des
cribed innonendo
dontically treated
as well as
in teethafter roo
t canal preparatio
n (3, 4). Howeve
r, thereseems to
be disagreement
about the causes
of root fracture.
Historically, pulp
less teethwere co
nsideredto be
more brittle (5),
whereasmore re
cent studies repo
rted nosignifican
t differences in
moisturecontent (
6), strength and
stiffnessof dentin
(7, 8), nanomech
anical changes
to radicular intert
ubular dentin (9)
, or brittleness of
endodontically tre
ated teeth (10).
There isan incre
asing awareness
among clinicians
and patients abo
ut VRF that
calls forthe iden
tificationof the fa
ctors responsible
for fractures of
endodontically
treated teeth in or
der tomaximize t
ooth survival time
(11). Some studi
es have suggested
that factors direct
ly relatedto cleani
ng (12),shaping
(13), and filling (
14) procedures,
per se, could deb
ilitate root canal–
treated teeth.
The instrumenta
tion of root cana
ls alonesignifica
ntly reduced the
resistance of
teeth to fracturein in vitro studies
(13, 15). More
over, different p
reparation
techniques and file desi
gns havebeen identified
as beingresponsi
ble for different
degreesof dentin
al damage and th
e induction of m
icrocracks (16–
20). More recen
t
data suggested a
relationship betw
een thepresence
of dentinal defect
s and different
shapingmotions.
Althoughhand instrume
ntation techniques produ
ced significantly
less dentinal def
ects (20, 21), re
ciprocating files
that operate und
er the concept of
single-file prepar
ation were shown to create si
gnificantly more
incomplete dent
inal
cracks than full-s
equencerotary sy
stems (22).
It couldbe specu
lated that the use
of a single instru
ment, rather than
a seriesof
files, to perform the entir
e canal preparatio
n will generate m
ore stress (22). H
owever,
these experimen
ts usedextracted
teeth (15, 17–20, 22,
23) thatlacked bone an
d
periodontal ligam
ent (PDL) support
aroundthe teeth, th
us possiblyaltering
the
generated forces
(24).
In somestudies,
extractedteeth wer
e mounted in res
in blocks with sim
ulated PDL
in orderto mimic
bony sockets that
in turn may influe
nce theforces ap
plied during
endodontic proce
dures (18, 19, 2
1, 25).However
, no artificial ma
terial was found
to completely rep
roduce viscoelast
ic properties of t
he PDL,whereas
the PDLacts to
absorb much of th
e forcesintroduc
ed into teeth clin
ically (24).
A majorshortcom
ing of studies in
extractedteeth is t
hat specimens ca
n be sub-
jected toundue fo
rces during the e
xtractionprocedu
re and may displa
y microfractures
before being used
as samples in cra
ck studies. In add
ition, time since e
xtractionand the
lack of knowledge of
the previous circ
umstances of the
patient’sdentition
such as
occlusaldysfunct
ions or trauma c
ould alsoinfluenc
e the results (23)
. Therefore, the
aim of this study was
to compare the a
bility of 2different
shapingtechniqu
es in thein-
ductionof dentin
al microcracks in
an in situ cadave
r model.
Materialand Methods
Six adulthuman c
adaver skulls wit
h at least 3 lowe
r incisors were o
btained;the
final sample num
ber in each of the
3 groupswas n =
6. The time of de
mise was less
than 9 months pr
evious tothe comp
letion ofthe study
. The mean age o
f the tissue do-
nors was82.8 ("14.6) ye
ars. Twodigital ra
diographs with di
fferent angulation
s were
From the Department
of Endodontics, U
niversityof the P
a-
cific, Arthur A. Dugo
ni School of Dentistr
y, SanFrancisc
o,
California.
Addressrequests
for reprints to D
r Ana Arias, Univ
ersity of
the Pacific, Arth
ur A. Dugoni Sch
ool of Dentistry,
2155 Webster
St, San Francisco
, CA 94115. E-ma
il address: aa@ana-aria
s.com
0099-2399/$ - s
ee frontmatter
Copyright ª 2014 Am
erican Associatio
n of Endodontist
s.
http://dx.doi.org/
10.1016/j.joen.2
013.12.003
Basic Research—Technolo
gy
JOE — Volume-, Numbe
r -, - 2014
Microcracks in C
adaver Teeth
1
§ Microcracks are...! -!difficult to detect - associated with various events over the life of a tooth
Unshaped Control
Arias et al J Endod in press
Shaping
§ “More of the same” - refined instruments that are more efficient and safer - easier market penetration but limited innovation
§ Minimal invasive - limited enlargement and retained structural integrity - specific set of challenges
§ Not at all - specific non-instrumental techniques - alternatively, vital pulp therapy or regeneration
Preparation Possibilitiesn What is new?
n NiTi properties
n Metallurgy
n Discussion
n
Shaping
n What is new?
n NiTi properties
n Metallurgy
n Discussion
Questions so far?