A comparative study of the sealing ability of two root canal obturation techniques

A comparative study of the sealing ability of two root canal obturation techniques

0099-2399/95/2109-0449503.00/0 JOURNALOF ENDODONTICS Copyright © 1995 by The American Association of Endodontists Printed in U.S.A. VOL. 21, NO. 9, S...

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0099-2399/95/2109-0449503.00/0 JOURNALOF ENDODONTICS Copyright © 1995 by The American Association of Endodontists

Printed in U.S.A. VOL. 21, NO. 9, SEPTEMBER1995

A Comparative Study of the Sealing Ability of Two Root Canal Obturation Techniques Antonio Pallares, DMD and Vicente Faus, DMD

A comparison was made of the ability of two root canal obturating techniques to prevent dye microleakage: gutta-percha lateral condensation and mechanically plasticized gutta-percha (JS Quickfill). Twenty central incisors were prepared and obturated by each technique. After rendering the teeth transparent, linear dye penetration was found to be 0.48 and 0.52 mm, respectively. The difference between the two techniques was not significant. As for the distribution of the sealing cement (AH26) in the teeth obturated with JS Quickfill, the cement was located in the most peripheral zone of the obturation alongside the dentinal walls, whereas the gutta-percha was found in the central part of the canal obturating material.

lected 50 specimens with straight canals to minimize possible instrumentation problems. The teeth were immersed in water until instrumentation and divided into three groups.

Group 1 Twenty upper central incisors were instrumented with identical new K-files for each tooth (Maillefer SA, Ballaigues, Switzerland). Before canal preparation, the apexes were perforated with #10 K-files to confirm their permeability. The canals were instrumented by a step-back technique and a #45 apical termination file being used up to 1 mm short of the apex. Sodium hypochlorite (0.5%) was used as the irrigating solution. The coronal portions of the canals were prepared with Hedstrom files up to #70. The canals were then dried with paper points, and the apexes were again perforated using a size 10 K-file to guarantee canal patency. The cement (AH26) was introduced into the canals with #35 K-files. Canal obturation was then performed by the lateral guttapercha condensation technique.

According to a number of studies, up to 60% of failures in endodontics are due to incomplete filling of the root canal system (1). This is possibly a consequence of the complexity of root canal anatomy, with irregularities, anastomoses between canals, and the existence of accessory and lateral canals. As a result, tridimensional sealing of the root canal becomes difficult. Lateral gutta-percha condensation is currently the most accepted canal obturating method. However, a number of different plasticized gutta-percha techniques have been introduced with the aim of securing better sealing of the canal irregularities. JS Quickfill (JS Dental Manufacturing, Inc., Ridgefield, CT) affords a canal obturating method in which a carrier similar to a lentulo and covered with gutta-percha is warmed by wall friction on rotating it within the root canal (Fig. 1). In this way, the plasticized gutta-percha is impulsed apically, whereas the titanium carrier is simultaneously removed from the canal. It may also be left in place, however. The aim of the present study was to compare the apical sealing capacity of JS Quickfill and lateral gutta-percha condensation.

Group 2 Upper incisors were instrumented in the same way as in group 1, and after introducing the cement (AH26) within the canal using a #35 file, obturation was performed with JS Quickfill according to the instructions of the manufacturer. A JS Quickfill two sizes smaller than the last file used to prepare the apical third of the canal was selected and positioned within the canal until a slight resistance was noted. Rotation was started until gutta-percha plasticity was noted, and slight pressure was applied apically until reaching working length. The titanium core of the JS Quickfill was then removed from the canal while continuing clockwise rotation.

Group 3 The remaining 10 upper central incisors were used as controls. Five were instrumented but not obturated (positive controls), whereas the other five were instrumented, obturated, and coated with nail polish (negative controls). After obturating the teeth in all three groups, buccolingual projection X-rays were taken to verify correct obturation. The teeth were then immersed in physiological saline, and 24 h later they

M A T E R I A L S AND M E T H O D S A large series of upper incisors recently removed for prosthetic or periodontal reasons were examined. The calculus and soft tissue fragments were eliminated mechanically. We radiographically se-

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Journal of Endodontics

Pallar~s and Faus

DISCUSSION

FIG 1. JS Quickfill before

(top) and after (bottom) use.

were numbered and two layers of nail polish were uniformly applied, except for the most apical 3 mm. All teeth were immersed in India ink for 72 h, after which the specimens were washed and varnish removed with a scalpel blade. The roots were decalcified in 10% nitric acid for 72 h, followed by washing and dehydration in an alcohol series (60, 80, and 100%). Specimens were finally rendered transparent with methyl salicylate (2). Each canal was examined under a stereoscopic light microscope (Nikon SMZ-2T), and a calibrated grid was used to determine leakage. After measuring linear microfiltration of dye in specimens obturated with JS Quickfill, we cut the decalcified teeth with a #15 scalpel blade to remove and examine the filling material.

The results obtained with the positive and negative controls indicate that the leakage model chosen was appropriate for the purpose of the present study. Linear penetration of dye was similar between the teeth obturated by lateral gutta-percha condensation and by JS Quickfill. Aktener et al. (3) concluded that to obtain optimum penetration into dentinal tubules, root canal filling materials should have low surface tension or an adequate surface-active reagent must be added to them. Oksan et al. (4) observed that cement penetration into the dentinal tubules following removal of the smear layer is conditioned by factors such as the chemical composition of the cement and its physical properties. It would also be of interest to study the influence of rotational movement upon the penetration of the sealing agent within the dentinal tubules. On examining the specimens obturated with JS Quickfill, we noted the presence of a number of lateral and accessory canals that were only filled with sealing cement. Under higher magnification, it would be of interest 1o see if mechanically softened gutta-percha is able to penetrate the dentinal tubules along with the sealing cement, as occurs with thermally softened gutta-percha (5, 6) once the smear layer is eliminated. The results of this in vitro study showed that JS Quickfill gives a well-filled root canal, provided that overfillings can be avoided (7, 8). Dr. Pallares is associate professor and Dr. Faus is titular professor, Operative Dentistry, Faculty of Medicine and Odontology, University of Valencia, Valencia, Spain. Address requests for reprints to Dr. Antonio Pallar~s, Pasaje J. Segura Esc 0-2 a, 46680, Algemesi, Valencia, Spain.

References

RESULTS The positive control showed dye leakage throughout the length of the canals, whereas the negative controls had no dye penetration. Leakage for teeth obturated by lateral condensation was 0.48 _+ 0.82 mm (mean _+ SD) versus 0.52 _+ 0.94 mm in the case of teeth obturated with JS Quickfill. Student t test revealed a t value of 0.132 (nonsignificant). Detailed observation of the filling in teeth obturated with JS Quickfill revealed the following distribution of the sealing cement. From the coronal to the apical thirds, the AH26 was situated closest to the dentinal walls whereas the gutta-percha was positioned in the center without direct contact with the dentin. The sealing cement layer was very thin at the apical third, its thickness increasing progressively toward the coronal third.

1. Ingle JI. Endodontics, 3rd ed. Philadelphia: Lea & Febiger, 1985:27. 2. Robertson D, Leeb IJ, McKee M, Brewer E. A clearing technique for the study of root canal systems. J Endodon 1980;6:421-4. 3. Aktener BO, Cengiz T, Piskin B. The penetration of smear material into dentinal tubules during instrumentation with surface-active reagents: a scanning electron microscopic study. J Endodon 1989;16:588-90. 4. Oksan T, Aktener BO, Sen BH, Tezel H. The penetration of root canal sealers into dentinal tubules. A scanning electron microscopy study. Int Endod J 1993;26:301-5. 5. Guttman JL. Adaptation of injected thermoplasticized gutta-percha in the absence of the dentinal smear layer. Int Endod J 1993;26:87-92. 6. Genqoglu N, Samani S, G~nday M. Dentinal wall adaptation of thermop~asticized gutta-percha in the absence or presence of smear ]ayer: a scanning electron microscopic study. J Endodon 1993;19:558-62. 7. Scott AC, Vire DE. An evaluation of the ability of a dentin plug to control extrusion of thermoplasticized gutta-percha. J Endodon 1992;18:52-7. 8. George JW, Michanowicz AE, Michanowicz JC. A method of canal preparation to control apical extrusion of low-temperature thermoplasticized gutta-percha. J Endodon 1987; 13:18-23.

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