International Endodontk journal (1993) 26,173-178

An assessment of the plastic Thermafil obturation techniquePartiRadiographic evaluation of adaptation and placementJ. L. GUTMANN, W. P. SAUNDERS*, E. M. SAUNDERSt& L. NGUYENDepartment of Restorative Sciences. Baylor College of Dentistry, Dallas, Texas, USA; 'Department of Adult Dental Care,

Glasgow Dental Hospital and School Glasgow and f Department of Conservative Dentistry, The Dental School Dundee, UK

Summary

Adaptation and placement of alpha-[diase gutta-perchadelivered with a plastic core-carrier, Thermafil, wascompared to the lateral condensation of gutta-percha ina spraific tooth model. Fifty-one mandibular molar rootswith separate canals, patent canal orifices and curva-tures greater than 15 degrees were cleaned and shapedwith K-files and 2.5% sodium hypochlorite to a size 30at the apex, and flared with Hedstrom flies to create acontinuously tapering iunnel preparation. Canals wererandomly obturated with Seaiapex root canal sealer andeither alpha-phase gutta-percha on a plastic Thermafllcarrier, or standard beta-phase gutta-percha withlateral condensation. Roots were radiographed fromthe proximal and evaluated by three examiners, basedon established criteria for overall material adaptation,apical adaptation, and fltling material extrusion.Thermafit provided a statistically significant better over-alt canal obturation (P< 0.001), while, in the apicalthird, both techniques were not significantly difierent(P > 0.05). When the apical orifice was patent there wasa significant propensity for the extrusion of fillingmaterials beyond the apex (P< 0.001) with theThermafl] technique.

Keywords: extrusion, heated gutta-percha, radiographicevaluation, obturation, Thermafil.

Introduction

Techniques which claim to provide three-dimeasiona)obturation of the root canal system are dependent ofproper cleaning and shaping prior to filling. Likewise,because all canal systems present with a multitude ofirregularities, obturation techniques and materials must

Correspondence; Dr James L. Gutmann. Baylor College of Dentistry.3302 Gaston Avenue, DaUas, Texas 75246, USA,

be capable of being adapted to the root canal walls,thereby providing complete obturation of the preparedspace. Clinically, the determination of that obturationand adaptation is manifest exclusively by radio^aphicassessment, with parameters of evaluation including the•length of the filling material in the canal and its density,shape, and uniformity of appearance in relation tothe walls of the canal (Quality Assurance Guidelines.American Association of Endodontists, 1987).

Because gutta-percha obturation techniques generallyrequire some type of condensation (lateral, vertical),their final radiographic appearance may or may not befraught with undesirable variations in appearEmce suchas sealer voids, spreader tracks, condenser voids andmaterial welds {in the case of heated techniques)(Gutmann & Hovland 1992). While various studies haveattempted to relate these aberrancies with case unaccept-abiiity and faiiure. little correlation exists at present,except for the standard that a dense, well-adapted rootfilling is clinically and radiographicaily acceptable.

In the last 15 years, efforts have been made to producefillings and techniques which can achieve the maximumcanal adaptation with the minimum amount of leakage.In the late 1970s and early 1980s, the developmentof the injectable thermopiasticized gutta-percha tech-niques has made material adaptation not only mucheasier, but also equal in quality if not superior, topreviously advocated techniques (Yee et al. 1977,Torabinejad et al, 1978, Michanowicz & Czonstkowsky1984, Michanowicz et aJ, 1986), Even with new develop-ments, however, the presence of short root fillings andthose with voids is common, primarily due to lack ofoperator expertise and skill in the application of thesenew advances (Gutmann & Rakusin 1987).

In 1978 Johnson presented a simple method forthe delivery of thermopiasticized gutta-percha to theproperly prepared canal, which appeared to minimize oreUminate problems in the radiographic appearance of

173

174 J. L. Gutmann et al.

the root canal obturation. Fillings could be placed to theprepared apex with reasonable apical control and fllliogdensity was uniform, as the softened material adaptedeasily to the prepared canal walls and flowed into theirregularities often found in the root canal system. Theinitial development of this system relied on metalliccarriers for delivery and placement of the softenedgutta-percha. Present technology has resulted in aplastic carrier (Thermafil Endodontic Obturators-plastic:Tulsa Dental Products. Tulsa. Oklahoma. USA) whichcan delix'er the softened material with ease and consider-able accuracy. While still in its infanc}'. the application ofthis technique shows great promise. Clinically relevantevaluations of this technique are necessary', however toensure that minimal standards of acceptability are metand that the clinician can assess properly the attainmentof these standards. The purpose of this initial study in aseries of evaluations of the Thermafll technique, was toassess the radiographic appearance of canal obturationwith the plastic Thermafil obturator, and compare it toaccepted standards using a clinically relevant model.

Materials and methods

Fifty-one extracted human permanent mandibularmolars were used in this study. The teeth w ere sectionedbuccolingually through the furcation with a diamondsaw. The mesial and distal roots were accessed and radio-graphed with working length files (No. 10 K-ile) in eachcanal to examine the anatomy and ensure the patency ofthe canal system (Fig. 1). Roots were selected for thestudy based on the following criteria: cun'ature of theroot of 15" or greater: two separate root canals: andseparate apical orifices.

A size 10 K-Flex file (Kerr Manufacturing Co..Romulus. Michigari. USA) was passed down each canalof the mesial root until the tip was seen to perforate justthrough the apical part of the root. The instrument waswithdrawn 1.0 mm and this recorded as the workinglength. Further working radiographs were taken ifnecessary from both a mesiodistal and buccolingualorientation.

Preparation of the root canals ivas performed withK-Flex files and Hedstrom files (Kerr Manufacturing Co..Romuius. Michigan, USA), alternately, until the apicalportion of each root canal was flied to a size 30. Thiswas accompanied hy irrigation, after the use of each sizeof instrument, with 2 ml of 2.5% sodium hypochioritesolution, delix'ered from an Endodontic ssringe (SherwoodMedical, St Louis, Missouri. USA) with a 23 gauge

Fig. 1. Proximal radiograph demonstratiag canal working length,separate canals an<l patent apical foramen.

needle. The remainder of the root canal was preparedwith a step-back technique (MuUaney 1979) usingHedstrom files along with recapitulation with a size 30K-file to the working length to remove dentinal debris.Adequate flaring of the canal was considered to havebeen attained when a D-llT endodontic spreader(HuFriedy. Chicago. Illinois. USA) and a No. 30 plasticThermafll core without gutta-percha, could be fittedloosely in the root canal to the working length. Followingpreparation the master apical file was placed in eachcanal and radiographs taken to verify the workinglength. Patency of the apical foramen was ensured withthetipofasizelOK-flle.

The prepared mesiobuccal and mesiolingual rootcanals of each tooth were irrigated with 3.0 ml of2.5% sodium hypochiorite. dried with paper points, andobtuated randomly with either lateral condensation ofcold gutta-percha or Thermafii with plastic cores. Thecanal to be filled by lateral condensation was fitted with amaster gutta-percha cone (Union Broach, Long IslandCity, New York) that gave a snug fit at the workinglength. This cone was lightly coated with root canalsealer, Sealapex (Kerr Manufacturing Co.) and used to

Plastic Thermafil obturation technique. Part 1 175

Table 1, Criteria for radiographic evaluation of filling material Overall canal obturation

Ratings Criteria for each rating

0 Consistently dense, radiopaque fill in all three segments(apical, middle and cortmai): gutta-percha is well adaptedto the canal outUne

1 Mitiimal variation in density throughout: some evidenceof small voids (< 0.5 mm) or instrument marks <10%oftotal Sll

2 Moth-eaten appearance or voids (< 0,5 mm) in the apica!third, and/or evident throughout the filling

3 Voids (> 0.5 mm but < 1.0 mm) in the apical third, and/or evident throughout the filling

4 Voids (> 1.0 mm) in the apical third, and/or evidentthroughout the filling

Table 2, Criteria for extrusion of material through apicai foramen

Ratings Criteria for rating extrusion of materials

0 No sealer or gutta-percha heyond the working length

1 Sealer and/or gutta-percha beyond the working lengthbut not at radiographic apex

2 Sealer and/or gutta-percha at the radiographic apex

3 Sealer and/or gutta-percha beyond the radiographic apex

2 3 4RaUngs

LC = Lateral condensation TH = Thienmafil

Fig. 2. Bar graph showing ratings for overall obturation.

45403530

45Canal obturation - apical third

i0

e^Hi

1

2

2Ratings

5I:•_3

31 1

• LCOTH

21

4

LC = Lateral condensation TH = Ttiermafil

Fig. 3. Bar graph showing ratings for obturation in the ajHcal third.

wipe the walls of the canal. Following a second lightcoating with sealer, the master cone was inserted tothe working length of the canal and held there for5 s before condensation commenced. Lateral condensa-tion was completed using a D-llT spreader (HuFriedy)and accessory cones (Union Broach) tintil the spreadercould not penetrate more than 1 to 2 mm into the canalorifice.

The remaining root canal was filled with a No, 30Thermafil obturator containing the plastic core. Theobturating core was heated in the ThermaPrep oven for aminimum of 4 min, as recommended by the manufac-turer. A small amount of Sealapex was applied twice tothe walls of the root canal with a No. 30 mastergutta-percha cone and the heated Thermafll obturatorwas positioned to the proper depth in the canal.

Proximal radiographs were exposed of all roots andsubjected to evaluation at x 6 magnification using aRealistic-Vantage 5 Magnifier (ANACOMP, Maltiprodux

4 0

35

30

c 25

§201 '5

10

5

0

Extrusion of filling materials

r -

• LCD T H

_ 19

~ ^ ^ l 14

- J - L J H ^

39

Ratings

LC = Lateral condensation TH - Thermafil

Fig. 4. Bar graph showing ratings for extrusion of filling materials.

Division, Hartford, Wisconsin, USA). Teeth were evalu-ated as to the overall obturation, apical third obturationand material extrusion. Three examinees, who had beentrained in the criteria for evaluation of obturation andmaterial extrusion (Tables 1 and 2), reviewed and ratedeach radiograph. All cases in which there was a dis-crepancy, were re-reviewed and a score was agreed uponby all examiners.

176 J. L. Gutmann et al.

I - - ,I ^.

:

• /••

Fig. S. Radiograph showing good overall obturation in both canals.Right canai is the Thermafil

Statistical analj'sis was performed using the Mann-Whitney U-test to compare both the overall quality of thetwo obturation techniques and the quality in the apicalthird of the root canal. In addition, comparisons weremade on the amount of extrusion of obturating materialthrough the apical foramina.

Results

The results of the radiographic evaluation are shown inFigs 2 ^ . Statistical analysis showed that Thermafilobturation gave a significantly better overall obturationusing the criteria stated. P < 0.001. No significant differ-ences were noted between the two methods of obturationin theapical third, P> 0.05 (Fig. 5). Thermafilobturation.however, resulted in significantly more material extrusionbeyond the apical preparation, P < 0.001 (Fig. 6).

Discussion

The importance of radiographic criteria and theirconsistent application cannot be overemphasized in the

Fig. 6. Radiograph showing good o\ erai! obturation in the Therniafilobturated canal fnghtL with material extrusion: poor overall obtu-ration of lateral condensation (left I. Note however, the qualit_v of theapical conden.sation of the gutta-percha in both canals is excellent.

evaluation of root canal treatment. This is essential tosupport standards of care which must be attained if areasonable degree of success is to be achieved in patienttreatment. Clinical guidelines published in the QualityAssurance Guidelines by the American Association ofEndodontists (1987), indicate that radiographically,there should be the appearance of a dense, three-dimensional filling which extends as close as possible tothe cemento-dentinal junction. Gross overextensions ofthe filling material into the periradicular tissues andunderfilling or undercondensation in the presence ofpatent canal space are considered undesirable. In thisrespect, there was a predisposition for extrusion of fillingmaterials with the Thermafil obturation technique whenthe apical foramen was patent. These findings have beennoted in other studies using Thermafll (Lares & ElDeeb1990, Haddix et al 1991, Clark 199], Christiansen1991,Mattison«tfl/. 1991, Scott &Vire 1992), Preven-tion of this occurrence with the use of an apical dentine

Plastic Thermafil obturation technique. Part 1 177

plug has been demonstrated by Scott & Vire (1992). Evenwith this predisposition, however, evidence of leakagehas been shown to be non-existent (Clark 1991) andEwriradicular tissue response to material extrusion withThermafll has been shown to be similar to that observedwith the lateral condensation (Mattison et al. 1991),

In this study, both filling techniques radiographicallysatisfied the established criteria for root canal fillingsin the apical third of the canal. Canals were three-dimensionally and densely filled, with filling materialextending at least to the apical constriction, whichis crucial to prevent or tninimize leakage from thesurrovmding tissues. Equally important though, is thedense, three-dimensional obturation of the entire canal,to assist in the control of coronal leakage. In this regard,and with respect to the overall adaptation of the fillingmaterial to the canal irregularities, the Thermafil tech-nique provided a significantly better result. The fact thata root canal appears densely obturated, on radiographicexamination, does not indicate, however, that the seal ofthe canal system is adequate, Kersten (1987) has shownthat the use of the proximal radiograph gives a betterprediction of the quality of gutta-percha adaptation andcompaction. In the cases evaluated, filling materialswere seen adapted to the highly irregular nature ofthe canal systems, which is often only seen from theproximal view.

The application and comparison of the two fillingtechniques in the model described tended to minimizevariables often encountered in individual samples foreach technique. Likewise it provided the evaluatorswith a direct comparison as both techniques could beviewed simultaneously within the same anatomicalsurroundings.

The three examiners who radiographically evaluatedthe specimens, had been standardized to the criterialisted in Tables 1 and 2, This was essential becauseobserver bias is a major factor in dental radiographicinterpretation (Zakariasen et al. 1984, Lambrianidis1985), Likewise the formal structuring of all radio-graphic evaluative studies Is essential (Reit & HoUender1983, Halse & Molven 1986, Reit & Grondahl 1987),especially the use of large sample sizes, multiplestandardized observers, and standardized agreed-uponcriteria (Koran 1975, Reit 1987),

Conclusions

Within the parameters of this study and based uponstandardized radiographic criteria the following conclusionscan be drawn.

(1) Obturation of curved root canals with alpha-phase gutta-percha on a plastic core-carrier,Thermafil, resulted in a more dense and welladapted root canal fill throughout the entire canalsystem, than lateral condensation with standardgutta-percha,

(2) Both lateral condensation and Thermafil plasticcore-carrier obturations demonstrated acceptableroot canal fillings in the apical one-third of thecanal.

(3) There was a significant predisposition for materialextrusion beyond a patent apex with Thermafilobttiration using plastic core-carriers.

Acknowledgements

Dr W. P, Saunders wishes to acknowledge the WelcomeResearch Tnist for the award of a grant for travel to theUnited States where this research was tindertaken.

References

CHRISTIANSEN KR (1991) An in vitro comparison and quantitative analysisof warm lateral condensation and the Tkermi^ obturator. IndianaUniversity School of Dentistry, USA: Master Thesis.

CLARK DC (1991) The apical sealing ability of metal versus plastic carrierThermafil obturators. University of Minnesota. USA: Masters Thesis.

GUTMANN JL, HOVLAND E] (1992) Problems in root canal obturation. In:Gutmann JL. Ehimsha TC. Lovdahl PE, Hovland EC. eds. ProblemSolving in Endodontics St Louis: Moshy Year-Book inc.. pp. 92-116.

GUTMANN JL, RAKOSIN H (19871 Perspectives on root canal obturationwith thermoplasticised injectable gutta-percha. Internationa!Endodontic Journal 20. 261-70.

HADDIX JE, JARRELL M, MATTISON GD, PINK FE (1991) An in vitro

investigation of the apical seal produced by a new thermoplastidzedgutta-percha obturation technique. Quintessence /nternatiana/ 22,159-63.

HALSE A. MOLVEN 0 (1986) A strategy for the diagnosis of periapicalpathosis.;oHrnfllo/Endodontiesl2, 534-38.

JOHNSON W B (1978) A new gutta-percha technique. Journal ofEndodonlfcs 4 ,184-88.

KERSTEN HW, WESSEUNK PR, THOIEN VAN VELSEN SK (1987) The diag-

nostic reliability of the buccal radiograph after root canal filling.International Endodontic Journal 20, 20-24.

KORAN LM (1975) The reliability of clinical methods, data andjudgments. NewEnjJflnd/ournflJo/Merficine 293,642-46. 695-701.

LAMBRIANIDIS T (1985) Observer variation in radiographic evaluation.Endodontics and Dental Traumatoiogy 1 ,235-41.

LARES C. ELDEEB ME (1990) The sealing ability of the Thermafllobturation technique. Journal of Endodontics 16, 474-79.

MATTISON G, HADDK J, PINK F, BAUGHMAN R, COLLINS R (1991) Periapical

issue response to root canals flUed with Thermafil. Journal of DentalResearch 70, 362 (Abstract no. 771).

MiCHANOWia A, CzoNSTJCOWSKY M (1984) Sealing properties of aninjection-thermoplasticied low-temperature (70°) gutta-percha: apreUminary study. Journal o/Bndodontics 10, 563-66.

178 /. L. Gutmann et al.

TP (1979) Instrumentation of finely curved canals. DentalCtttucs of North Ammca2i, 575-92.

QuALTTY ASSURANCE GunMiNES (198 7) Chicago; American AssociaUon ofEndodontists, pp. 1-27.

REIT C (1987) The influence of observer calibcatlon on radiographicperiapical diagnosis, intermtioml Eadodmtk fourml 2 0 , 7 5 - 8 1 .

REIT C. GRONDAHL H-C (1987) Endodontic decision-making underuncertainty: a decision analytic ap[»x>ach to management of peri-apical lesions in endodontically treated teeth. Endodontics and DentalTrtumatology 3 ,15-20.

RETT C. HOLLENDER L (1983) Radiographic evaluati<m of endodontictherapy and the inituence of observer variation. Scmidttnavian Journalof Dental Research 91 ,205-12 .

Scon AC. VntEDE (1992) An evaluation of the ability of a draatin plugto control extrusion of thermofdasticized gutta-percha. loumal ofEndoiontics IS, 52-57.

TORAONQAD M, SKOBE Z, TROMBLY F L et al. (1978) Scaonii^ electionmicroscopic study of root canal obturation using thermoplastidzedgavta-paccba. Journal of Endodontics 4,245-50.

YEE FS, MARUN ], KRAKOW AA, GRON P (1977) Three-dimensional

obturation of the root canal u^ng injection-molded, themuiplastictzeddental gutta-p«tha.7oumalo/Endodontics 3 ,168-74.

ZAKAWACT) KL. Scan DA, JENSEN JR (1984) Endodontic recall radio-graphs: how reliable is our interpretation of endodontic successor failure and what factors affect or reliability. Oral Surgery OralMedicine and Oral Pathology 57 ,343-47.