Effect of Various Exposure Methods on Shear Bond Strength of Composite Veneers to Enamel and Dentin (in-vitro)

Composite veneers are used as a conservative and cosmetic treatment for discolored and deformed teeth or defective restorations. Due to the effect of various exposure methods on polymerization shrinkage stress, this study aimed to investigate the effect of various treatment techniques on shear bond strength of composite veneers restoration.
In this in-vitro study, 72 premolar teeth were divided equally into enamel and dentin groups. The buccal surfaces in each groups were abraded to reach flat enamel or dentin surfaces. The specimens were mounted in acrylic cubs and bonding procedures were performed using Single Bond 2[M1] . The specimens were divided into three subgroups according to the methods of exposure including conventional, soft-start, and pulse-delay techniques. In each subgroup, a composite cylinder was formed on buccal surfaces using Z250 composite [M2] and different curing modes. The shear strengths were measured and the data were analyzed using one-way analysis of variance followed by Tukey multiple comparisons test (α=0.05).
There was no significant difference in shear strength of composite to enamel between enamel subgroups (P=0.185). However, the difference in shear strength of composite to dentin between dentin subgroups was significant (P=0.042). Adhesive failures were the most among all subgroups.
Curing with soft-start and pulse-delay methods can increase shear strength in both enamel and dentin surfaces. Nevertheless, it is more effective in dentin surfaces