[The preparation of enamel margin beveling in proximal cavities].

Minicavities for posterior composite resin restorations were prepared in 24 caries-free teeth. The aim of this in vitro study was to evaluate the micromorphology of the proximal cavosurface bevel. The cavosurface bevel has been employed for many years as an accepted modification for composite restorations in permanent anterior teeth. The bevel provides more exposed enamel rod ends available for bonding. Using the acid-etch technique the resin-enamel bond is stronger with etched transverse sections of enamel prisms than with longitudinal sections. Enamel in the proximal and gingival wall of class II cavity preparations for restoration with composite should be beveled because prism direction is at right angles to the surface. The aim of this study was therefore to compare two methods for beveling the box margins of small proximal cavity preparations. One method for the preparation of the proximal bevel was the use of a modified EVA-System with the total amplitude reduced to 0.4 mm, the fixation of the file position and a new developed file (Bevelshape, grain 40 microns). The form of this file was modified in order to produce a short cavosurface bevel of the gingival and proximal wall without danger of damaging the adjacent tooth. The other method was the use of an axial margin trimmer. The micromorphology of the two methods was investigated by means of scanning electron microscopy and a score system as described earlier (Lussi et al. 1987). Statistical analysis revealed significant differences between the two groups. As compared to the axial margin trimmer the new device allowed a significant better finishing of the proximal bevel (p < or = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)