Interaction Between Sealers andGutta-percha Cones

Michael Tagger, DMD, MS, Beatrice Greenberg, DMD, and Galit Sela, BS, DMD, MSD

Clinical observations seem to indicate that somegutta-percha cones are softened by contact withsealers. The purpose of the study was to verifywhether an interaction existed between some seal-ers and different brands of gutta-percha cones.Because previous studies have indicated that thedifferences between brands of gutta-percha aremagnified by heat, thermatic compaction was usedin conjunction with a model of a root-canal prep-aration with lateral canals. Three brands of cones(Kerr, UDM, Beldent) were tested with three typesof endodontic sealers (AH 26, Apexit, Roth’s). Agroup without sealer served as a control. Thelength of flow into the lateral canals was measuredfor each combination and analyzed by two-wayANOVA. A highly significant difference was found,confirming the hypothesis that an interaction be-tween sealer and cones is present in some combi-nations. It was not possible to ascribe a trend ofgreater effect to a certain sealer, but Roth’s 811had the least effect on flow.

Gutta-percha has been used for more than 100 yr for the obturationof root canals, yet its properties are still being explored (1).Currently, great efforts are made to develop compounds that pro-vide better lateral seal and improved handling properties (2, 3). Thecardinal ingredient of the cones, which gives the material its name,is gutta-percha but it constitutes only up to 20% of the bulk of thecompound. The main component, 70% to 80%, is a filler: zincoxide, which is widely used in dentistry. In addition, radio-opaci-fiers, waxes, coloring, and plasticizing agents are present in verysmall quantities. Yet, these minor ingredients and changes in theproportions of the major ones affect significantly the clinicalbehavior of the cones: radio-opacity (4), solubility (5), adaptabilityto the walls (6), flow (7, 8), rejuvenation of one make only (9), orcomparison of seven brands (10), etc. Therefore, discussing phys-ical properties of gutta-percha is clinically meaningless unless thebrand and the mode of presentation of the material (cones, rods,carpules, syringes, spread on a carrier, etc.) is cited. The date ofproduction also may be useful because the manufacturers do not

divulge the exact composition of the material and they may changeparameters without notice (7).

Clinical observation has led practitioners and teachers to theconclusion that sealers soften some gutta-percha cones. Therefore,students are cautioned not to coat with sealer too many auxiliarycones in advance because their tip becomes soft (Fridlander C,personal communication, 2001). This observation was made at theuniversity’s clinic in which the sealer is usually AH 26 (DeTreyDentsply, Zurich, Switzerland), which is not known to contain asolvent of gutta-percha, unlike CRCS (Hygenic Corp, Akron, OH)for instance, in which approximately one-third of the liquid iseucalyptol. Because softening of the points is not always presentand the assumption was based on clinical impression, systematicinvestigation of the interaction, if any, between gutta-percha conesand a variety of sealers was deemed worthwhile.

MATERIALS AND METHODS

The elongation of a gutta-percha cone under cold compaction inan artificial model of the root canal (8) is too small for quantitativemeasurement but under thermomechanical compaction in vitrowithout sealer, the flow of gutta-percha is enhanced so that thedifferences between various brands are magnified (7). Sealer wasnot used in that study because of the fear that the resultant mixtureof warm gutta-percha and cement would be too messy and strati-fied in the mold to be suitable for precise assessment. This concernhas recently been disproved by a pilot study in which the majorityof the samples yielded a clear cast of the model thus showing thatthis in vitro study is feasible (11).

The model for testing the hypothesis of interaction was bor-rowed from a previous study (7). It consists, in essence, in abipartite mold of hard metal (chrome-cobalt). The two halves arehinged on one side and aligned, keyed by a series of cones and pitson their inner surface. On one side of the assembled book-likemold is an orifice leading into a straight endodontic cavity corre-sponding to size ISO 70 (Fig. 1). There is no apical opening butlateral canals 0.5 mm in diameter (also without exit). The gutta-percha cone, size 70, is coated with sealer and inserted into thecanal. A thermatic compactor (Engine Plugger size 60 ISO, Vere-inigte Dental Werke, Munich, Germany) is used as described byTagger et al. (12). After establishing tight contact with the gutta-percha, the engine is started at a speed of 15,000 rpm and keptwithout any vertical movement exactly for 1 s. The audible timesignal is provided by an electronic metronome (Type 7935,

JOURNAL OF ENDODONTICS Printed in U.S.A.Copyright © 2003 by The American Association of Endodontists VOL. 29, NO. 12, DECEMBER 2003

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Reichert, Austria) set at 1 s. The engine plugger is then advancedin a continuous movement up to the stop that indicates penetrationto 2 mm from the end of the canal. Then, without stopping therotation, it is slowly withdrawn in a continuous movement.

The mold is opened when it is cold enough (usually within 1–2min) and the specimen is carefully removed and placed into a smallcontainer marked in code for each group. The code is not revealeduntil full examination, measurement, and tabulation of the resultshave been completed.

Three brands of gutta-percha (Table 1) and three sealers ofdifferent types (Table 2) were tested in combination. An additionalgroup, gutta-percha cones without sealer served as a control, yield-ing altogether 12 groups. Each combination was replicated 10times and the extent of filling of the lateral canals was measuredunder magnification, as previously described (7). The mean andstandard deviation of each group and the data were subjected tostatistical analysis: two-way ANOVA for examining the interac-tion between gutta-percha and sealer (Table 3); and a one-wayanalysis of variance was used for each group of gutta-percha (bysealer) and each type of sealer (by gutta-percha brand), for a totalof 12 one-way ANOVA tests.

RESULTS

The flow of gutta-percha into the lateral canals ranged from 1.90mm (SD 0.53) for the combination of Korean-made Beldent gutta-percha cones with Roth’s 811 zinc–oxide-eugenol sealer to a highof 5.68 mm (SD 0.58) for UDM’s cones (distributed in Europe byZipperer, VDW, Munich, Germany) with Apexit (Table 3). Thecontrol groups showed the lowest penetration except for Kerr’sgutta-percha, in which the combination with Roth’s sealer waslower numerically but not statistically different from it (p � 0.5).In the case of UDM, there was no significant statistical differencebetween the control and Roth’s group, but the other two sealersunquestionably had more effect on the flow. Beldent was the leastaffected gutta-percha cone brand; only AH 26 was effective insoftening it sufficiently for the flow to be different from the control(Fig. 2). The overall interaction between gutta-percha and sealerswas highly significant (p � 0.001).

DISCUSSION

The results confirmed the hypothesis that there is an interactionbetween some brands of gutta-percha cones and certain sealers.Because the composition of the gutta-percha cones is not divulged,any attempt to link one of their ingredients with the flow of thematerial would be speculative. Direct comparison of the controls

FIG 1. Oblique view of the semiclosed book-like mold. Orifice of thecanal (arrow). Although the mold was cast with two canals, only onewas used (arrow). The second was destined to be used if the firstshowed imperfections in the casting.

TABLE 1. Brands of gutta-percha

Beldent—imported from R.O. Korea by Klingbeil Co, HaifaKerr—Sybron/Kerr, Romulus, MIUDM—United Dental Manufacturers, FL

TABLE 2. Sealers used

Brand name Type Manufacturer

AH 26 silver-free Epoxy resin DeTrey/Dentsply,Konstanz,Germany

Apexit Salicylate Vivadent,Schaan,Liechtenstein

Elite, Grade 811 Zinc oxide-eugenol-Grossman’s Roth,Chicago, IL

No sealer Control group

TABLE 3. Results—extension of filling within lateral canals (in mm)

Gutta-percha

Sealer

AH 26 Roth Apexit Control

Beldent 2.52 (0.66)* 1.90 (0.53) 1.92 (0.93) 1.18 (0.83)Kerr 3.96 (1.11) 2.36 (0.82) 2.54 (1.32) 2.47 (1.17)UDM 4.32 (1.04) 2.45 (0.63) 5.68 (0.58) 1.80 (1.44)

* Standard deviation.

FIG 2. Three-dimensional representation of the results of all 12groups. The extension of the gutta-percha into the lateral canals isexpressed in mm.

836 Tagger et al. Journal of Endodontics

(no sealer) with the results of a previous investigation in which nosealer was used (7) is not possible because of differences in thematerials and design. In the 8 yr that elapsed between the twoprojects, some brands of gutta-percha cones disappeared, otherswere apparently renamed but no one would confirm it. Because theextent of the flow is smaller in this study, it is possible to concludethat the sealer exerts a cooling effect caused by its mass and alsobecause it reduces friction with the gutta-percha.

The sealer that had a notable softening effect on most gutta-percha brands, resulting in increased flow, was AH 26 silver-free.Because the two ingredients present in the powder: bismuth oxideand hexamethylene-tetra-amine are not likely to affect the cones, itmust be assumed that the liquid (bisphenol epoxy resin) acts as apartial solvent of gutta-percha (or one of the secret additives). Thefindings of Lee et al. (13) confirm our results but these authorssuggest that chemical-bond formation is responsible for the highvalues, not mentioning a possible solvent effect of the resin.

Although it affects numerous plastic materials by softening orblemishing their surface, eugenol has no solvent effect on gutta-percha. This lack of interaction has been proven again in a studyof the bonding of sealers to gutta-percha (14) and reconfirmed (13).It should be noted that unlike relatively simple zinc-oxide–eugenolsealers, more complex formulations do affect gutta-percha.

The combination of Apexit with UDM cones gave the greatestpenetration in lateral canals. Because its effect on the flow of otherbrands of gutta-percha was slight and did not differ significantlyfrom the control, the cause for the exceptional interaction must besought for in the gutta-percha compound. The secrecy of thecomposition of the material leaves us no lead for tracing the natureof the ingredient.

The results of this investigation indicate again that gutta-perchacones cannot be referred to as one entity. Various brands maydiffer considerably in their physical properties to the point ofaffecting their clinical behavior. The results may be helpful to themanufacturers by providing them with a clue as to how to try toimprove and test their product and better their brand of gutta-percha cones. This type of investigation should be extended to thegutta-percha formulations that are currently being developed andintroduced, packaged for use with particular delivery devices (e.g.refill rods, carpules, preloaded syringes).

Understanding the interaction between gutta-percha and sealersmay serve as a guide for using the most suitable combination forspecific clinical cases. Thus, for instance, a tooth with a wide

apical foramen should be filled with a combination that provideslittle flow and, conversely, a root-canal preparation with a very fineapical foramen and internal irregularities that could not be abol-ished by the shaping procedure needs a more fluid combination.Finally, premature contact of gutta-percha cones with sealer shouldbe avoided.

The authors thank Ms. I. Gelertner (Computation Center Tel Aviv Univer-sity) for help with statistical analysis.

Dr. Tagger is retired associate professor, Dr. Sela is a senior graduatestudent, Department of Endodontology, The Maurice and Gabriela Gold-schleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel, andDr. Greenberg is in private practice, Pediatric Dentistry, Netanya, Israel.

Address requests for reprints to Professor Michael Tagger, School ofDental Medicine, Tel Aviv University, Ramat Aviv 69978, Israel; E-mail:taggendo@post.tav.ac.il.

References

1. Weine FS. A preview of the canal filling materials of the 21st century.Compendium 1992;13(Suppl):852–6.

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3. Tagger M, Katz A, Tamse A. Apical seal using the GPII method instraight canals compared with lateral condensation, with or without sealer.Oral Surg 1994;78:225–31.

4. Kaffe I, Littner MM, Tagger M, Tamse A. Is the radio-opacity standardfor gutta-percha sufficient for clinical use? J Endodon 1983;9:58–9.

5. Tamse A, Unger U, Metzger Z. Gutta-percha solvents: comparativestudy. J Endodon 1986;12:337–9.

6. Wong M, Peters DD, Lorton L. Comparison of gutta-percha filling tech-niques, compaction (mechanical), vertical (warm), lateral condensation tech-niques, part 1. J Endodon 1981;7:551–8.

7. Tagger M, Gold A. Flow of various brands of gutta-percha cones underin vitro thermomechanical compaction. J Endodon 1988;14:115–20.

8. Bou Dagher FE, Yared GM. Master cone apical movement duringcompaction: evaluation of two in vitro models. J Endodon 1993;19:22–5.

9. Sorin SM, Oliet S, Pearlstein F. Rejuvenation of aged (brittle) endodonticgutta-percha cones. J Endodon 1979;5:233–8.

10. Katz A, Tagger M, Tamse A. Is rejuvenation of gutta-percha a universaltechnique? J Endodon 1987;13:65–8.

11. Greenberg, B. Influence of the type of sealer on the flow of gutta-percha under thermomechanical compaction [master’s thesis]. Tel Aviv: TelAviv University, School of Dental Medicine, 1996.

12. Tagger M, Tamse A, Katz A. Efficacy of apical seal of engine pluggercondensed root canal fillings: leakage to dyes. Oral Surg 1983;56:641–6.

13. Lee KW, Williams MC, Camps JJ, Pashley DH. Adhesion of endodon-tic sealers to dentin and gutta-percha. J Endodon 2002;28:684–8.

14. Tagger M, Tagger E, Tjan AHL, Bakland LK. J Endodon 2003;29:191–3.

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