Effect of Removal of Enamel on Rebonding Strength of Resin Composite to Enamel

Objective. To examine the effect of removing the surface layer of enamel on the rebonding strength of resin composite. Methods. Teeth in four groups (n = 10) were etched, a small amount of resin composite was bonded and debonded, then specimens in three groups were ground for different lengths of time (10 s, 20 s, 30 s) to remove an increasing amount of enamel, one group was left untouched. The teeth were bonded again and the bond strengths of 1st and 2nd bonding were compared and analysed against the amount of enamel loss in different groups (7 mu m (+/- 2); 12 mu m (+/- 1); 16 mu m (+/- 3)). Specimens were examined with SEM and by noncontacting optical profilometer. Results. Although results indicated higher rebonding strength with increasing enamel removal ANOVA showed low statistical differences between the groups (p > 0.05). However, values between first bonding and rebonding strengths differed significantly (p < 0.05) in the group that was not ground. SEM revealed that enamel-surfaces that were ground after debonding etchedwell, compared to the surfaces that still contained adhesive remnants. Conclusions. Removal of small amount of enamel refreshed the surface for rebonding. Rebonding strengths without grinding the surface before bonding were lower than bond strength to intact enamel.