Surface topography of the enamel margins of butt and beveled Class V preparations

Abstract

A major shortcoming of the composite restorative resins is that they do not adhere to enamel and dentin.’ The alteration of tooth surfaces by acid conditioning with phosphoric acid increased the bonding of acrylic restorative resins to enamel,:: and the effects of phosphoric acid etching on enamel surfaces have been studied extensively with the scanning electron microscope @EM). ‘-? The classic cavity preparation for silicate cement, acrylic resin, and composite resin restorations is box-shaped with internal retention and a cavosurface angle of 90 degrees resulting in a butt joint. The concept of beveling the enamel margins of conventional butt preparations to produce a cavosurface angle of 135 degrees was proposed for the following reasons: 1. A beveled margin results in improved esthetics because it provides for the gradual transition from tooth structure to composite resin.” 2. A beveled marqin provides more enamel for c acid etchinK for retentive purposes.: 3. Acid etching of a beveled enamel margin provides improved marginal seal.‘ The poor leakage results obtained in butt restorations when compared to beveled restorations were explained on the basis that bonding of composite resins to surfaces of longitudinally cut enamel prisms was not as strong as to cross-cut enamel prisms.” Microleakage studies have been used extensively to evaluate the effect of restorative techniques on the integrity of the seal at the restoration/tooth inter-