A Laboratory Investigation to Compare Enamel Preparation by Sandblasting Or Acid Etching Prior to Bracket Bonding

Abstract

A laboratory investigation to compare the mean shear debonding force and mode of bond failure of metallic brackets bonded to sandblasted and acid-etched enamel is described. The buccal surfaces of 30 extracted human premolars were sandblasted for 5 seconds with 50 µ alumina and the buccal surfaces of a further 30 human premolars were etched with 37 per cent phosphoric acid for 15 seconds. Following storage for 24 hours at 37°C in distilled water, shear debonding forcewas measured using an Instron Universal Testing Machine with a cross-head speed of 10 mm/minute. Mean shear debonding force was significantly lower for brackets bonded to sandblasted enamel compared to acid etched enamel (P<0.001). Weibull analysis showed that at a given stress the probability of failure was significantly greater for brackets bonded to sandblasted enamel. Brackets bonded to etched enamel showed a mixed mode of bond failure whereas following sandblasting, failure was adhesive at the enamel/composite interface (P<0.01).