Avaliação in vitro da adesão de facetas laminadas cerâmicas em dentes não-vitais clareados externamente

Abstract

Nowadays, aesthetic problems are not limited to those induced by caries, but also the darkened teeth, for innumerable reasons. The color of the tooth depends on the composition of dental tissue. Any transformation or alteration in the tissues will lead to an alteration in the dental color. There are some solutions to the darkening problem, some less conservative, as the procedure of restorations. Others, as bleaching, are described as conservative of the structure of the tooth; however, bleaching may not totally solve the aesthetic problem. Veneers can improve or modify the color of the teeth, however, these alterations have limits, depending on innumerable factors. The association of bleaching and veneers represents what could be the best to an acceptable aesthetic result. If we consider that bleaching acts by diffusion, the conclusion is that less enamel structure presented to spread out the bleaching agent, will lead to better and faster bleaching. Thus, when doing veneers, a previous external bleaching can be done, before the impression, just after the preparation, where there will be a faster contact of the oxygen spring with the pigmented structure. However, the adhesive procedure of veneers is sensible to the oxygen. It must be waited at least two weeks after the bleaching for the accomplishment of the cementation, what it seems to be sufficient to prevent damages to the adhesion in the case of the external, traditional bleaching, but in the external over the preparation bleaching this becomes a doubt. The objective of this study was to evaluate, in vitro, through shear bond tests, the adhesion of laminate ceramic veneers to teeth that had been bleached previous to the execution of the preparations and the preparations that had been directly bleached on, comparing them to the adhesion on the preparations that had not suffered bleaching previous to the cementation. 60 human anterior teeth were used, sectioned and mounted in an epoxi resin structure. They were divided into three groups: group I, that received bleaching treatment e later veneer preparation, group II, that received the preparation and then the bleaching treatment, and group III, control group, without bleaching treatment. After an assembly time of 15 days, the cementation of ceramic tablets was carried through on the preparations, the specimens were termocycled, and were taken to the shear bond tests. After the statistical analysis (ANOVA and Tukey) of the results (group I – mean 56,02 MPa; group II – mean 46,42 MPa e group III – mean 54,42 MPa; p≤ 0,05 between groups I and II), the conclusions are that the adhesion of veneers on teeth that were bleached over the preparations was inferior to the adhesion on teeth that were not bleached, or when it was done after the preparations; on teeth that were not bleached, the results seem to be more homogeneous, and the adhesion of veneers to over-the-preparation bleached teeth may be performed, as its mean, although inferior to the ones of the other groups, are acceptable, from the mechanical point of view.