Effect of bevelling on the occurrence of fractures in the enamel surrounding composite resin fillings.

Three different types of cavities: (1) with a 90 degree cavo-surface angle, (2) with a bevel at the cavity margin 0-25-0-50 mm wide, and (3) with a bevel at the cavity margin 0-5-1-0 mm wide, were prepared in extracted human teeth. Fifteen cavities of all three types were filled with Adaptic. Fifteen cavities of Type 2 and of Type 3 were filled with cosmic and the same number and types of cavities with prestige. The fillings were polished 10 min after starting the mix of the composite resins. Fractures in the enamel at the cavity margins were visualized by discoloration with methylene blue. Fractures were observed around all types of cavities, but, for all types of materials, an increased bevel at the margin gave an increased number of fillings without fractures in the enamel. However, great variations in the frequency of fractures were also observed; i.e. Adaptic showing a small frequency, Cosmic a medium and Prestige a great frequency of fillings connected with fractures at the enamel margin.