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Endodontics ISSN 1516-4055 versão impressa

Endod. Clin. Pract. Educ. Res. v. 1 n. 2 São Paulo Maio 1999

A SIMPLIFIED TRANSVERSAL CUT SYSTEM TO STUDY ROOT CANAL MORPHOLOGY AND PREPARED TECHNIQUES

Skelton Macedo, M. C. Cardoso, R. J. A. Bombana, A. C. Universidade de São Paulo São Paulo – Brazil

ABSTRACT A simplified system of teeth inclusion to transversal cut is hereby presented. The method is easy to be reproduced at a low cost, and with no loss in precision of comparatives measures made after and before the cuts. UNITERMS: Root canal instrumentation

INTRODUCTION The necessity of studying the various techniques of preparing the root canal with greater accuracy always ended in a major problem: the difficulty in evaluating the previous conditions of the canal systems. Impression and even diafanization studies are very useful, but do not allow comparisons between the morphologic conditions of the root canal system prior and

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later to preparation. A model which permits this evaluation should have, as control, the original condition of the root canal . Bramante et al. (1987) developed a methodology which allowed the study of the root canal system comparing their conditions prior and later to preparation. For this, they used transversal cuts that could be remounted, due to the fact that the specimens were set in acrilic resin in individual plaster muffles. Of the various modifications in the methodology, we can describe the ones performed by McCann et al. (1990). These authors substituted the plaster muffle for the same model in cast iron, suggesting greater resistance to impacts and to the action of auxiliary chemical substances used during the root canal preparation. They also stated that the same muffle can be used for several specimens, reducing time spent making them. Other important changes were done by Tamse & Pilo (1998), where the muffle was substituted by a system of four pins joined to a metallic base where each specimen was included. This was done so as to reduce time spent on making the model, adding precision, versatility and the ability to reproduce the original methodology. Adding to the stated advantages, the purpose of this study is to modify the methodology of evaluation of the morphology and the techniques of root canal preparation, so as to make it easier to reproduce, using already available materials, less general cost, with no loss in final quality of precision, versatility and ability to reproduce.

MATERIAL E METHODS The modification of the tranversal cutting system for the morphologic study of the root canals consisted in a block of polyester resin containing a specimen to be studied and two cylindrical metal guides (steel nails) placed next to the proximal faces of two opposite positions. These metallic guides were coated in wax to compensate for the contraction suffered by the resin on cure. The especimens received a hand of black China ink on the root surfaces to facilitate visualization when using the stereoscopic magnifying lens. The block of resin containing the specimen was obtained from pouring the polyester resin into a 30mm tall, ¾ inch PVC receptacle. This receptacle was positioned with one of its openings towards a glass plaque and sealed with pink wax to avoid leakage of resin (fig. 1A). On its other opening, a small amount of pink wax, where the specimen and the metal guides coated in wax were fixed, was placed so as to keep them in a central position (Fig. 1B).

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A


B

Figura 1 - (a) ¾ inch PVC receptacle with wax on a glass plaque; (b) wax with the tooth and the metallic guides in position.

The open space between the small amount of pink wax and the walls of the receptacle was used to pour the polyester resin (2 parts of resin base to one of estirene monomer and to another of metil etil cetone peroxide as catalyst). Twenty four hours after pouring, the block containing the specimen and the metallic guides was easily removed from the glass plaque as well as from the receptacle. The guides were detached with the help of fine pliers and the block was taken to the cutter (hard tissue cutter Extec 1010 by Mitutoyo). The segments to be studied were produced with a 0.3 diamond disc, in this way reducing loss of material associated to this fase of the method (fig. 2).

A

B

Figura 2 - (a) resin block with cuts; (b) segments separated: I – coronary block; II – cervical segment; III – radicular block.

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Once the segments were obtained, where exists interest by the study, the morphologic evaluations of the root canal system can be done, as well as the measurements, photographs, etc. Next, the block was mounted once again with the aid of the guides, when any type of manipulation of the root canal and the pulp chamber can be performed, with no need for further adjusting to the receptacle or making it. In this way, the block can be detached once again, with pre and post operative evaluations of the root canal system.

DISCUSSION The methods of morphologic studies of the root canal system involving the impression and diafanization do not allow the study of previous and posterior conditions to chemical and surgical preparation. These methods are only efficient in the morphology study of one specific anatomic or surgical moment of the root canal system. Studies performed with the aid of radiografic exams allow bidimensional analysis only, and also provide other limitations when comparing images, since several important variables are involved. The proposal of Bramante et al. (1987) allows for the comparison of the morphologic condition of the root canal system prior and later to preparation, being that the initial condition is used as the control of the instituted therapy. This proposal involves the inclusion of the specimen in acrilic resin with remounting guides. The block of resin containing the specimen is included in a plaster muffle which, reproducing the guides, can be easily remounted. The problems associated to this methodology are the use of acrylic resin and the use of a plaster muffle. The acrylic resin suffers great contraction on cure, which may lead to the loosening of the specimen, in this way increasing the difficulty in precisely remounting so as to perform the chemical and surgical preparations. The plaster muffle can easily fracture, and also deteriorate with the use of auxiliary chemical substances during the preparation of root canal. Considerations by McCann et al. (1990) about this method allow for the substitution of the plaster muffle for cast iron, so as to eliminate these limitations. To proceed in remounting in this case, the use of a morse is necessary, and the use of the same muffle is recommended for all the specimens. Although there is a gain in time, there is the difficulty in making the cast iron muffle so as to reproduce the experimental model. Tamse & Pilo (1998) suggested a modification for the remounting guides of the resin block, where it would be possible to eliminate the use of the muffle of the original model, be it of plaster or of cast iron. The authors suggest the use of a metallic apparatus which would act as a support for the 4 metallic pins which are set around the specimen to be studied. The tooth is fixed to the base with the use of wax, centralized amongst the pins described previously. The whole set is then put into a Teflon receptacle and the resin is poured so as to cover the pins and the tooth which will be studied. Upon cure, the whole set is loosened from the Teflon receptacle and the guides, and is cut at pre-established sections so as to continue on to the morphologic study of the root canals. Once these studies are concluded, the segments of the resin block containing the tooth are remounted with the help of the metallic guides and the base, and the root canal preparation is done. This modification can be simplified to a greater extent in this study, and still be perfectly useful, by using a PVC receptacle and steel nails as metallic guides, in this way reducing costs and making it a more accessible methodology. Since simple materials are used and it is a very

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practical method, is also easy to reproduce. The perfect adjustment of the guides allows a safe remounting for the root canal preparation to be conducted, with no kind of deterioration of the materials used. The evaluations can be done with the optical microscope or even with the stereoscopic magnifying lens. A coat of China ink allows a usefull contrast during the morphologic evaluations. Linear or area analysis can be performed on the faces of the segments containing parts of the teeth studied.

CONCLUSIONS The modification of this methodoly is much more practical since it involves ready available materials, and of a low cost. It is easy to reproduce, with no loss in precision or versatility; Taking into consideration the amount of techniques for root canal preparation and the new products for this, and with polemic discussions about the results, this methodology promises to evaluate all of these with precision, comparing the original anatomical condition of the root canal (also serving as control of the work to be performed) with the post-preparatory surgical condition, with quick results; and, This method allows better studying and teaching conditions of internal dental anatomy, providing durable specimens and didatic material.

REFERENCES 1. Bramante, C. M.; Berbert, A.; Borges, R. P. A methodology for evaluation of root canal instrumentation. J Endod, 1987, 13(5): 243-245 2. McCann, J. T.; Keller, D. L.; LaBounty, G. L. A modification of the muffle model system to study root canal morphology. J Endod, 1990, 16(3): 114-115 3. Tamse, A.; Pilo, R. A new muffle model system to study root canal morphology and instrumentation techniques. J Endod, 24(8): 540-542

© 2014 Endodontics - Clinical Practice, Education and Research Av. Prof. Lineu Prestes, 2227 - Cidade Universitária - Butantã - CEP 05508-900 - São Paulo - SP

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