Effect of thermal stress on dentin adhesives used individually and in combination

Polymerization shrinkage remains an inherent problem in composite restorations. Dentin adhesives generally improve bonding to dentin but do not consistently provide leak-free restorations. This study evaluated a dentin adhesive that bonds to dentinal calcium and another that bonds to dentinal collagen when used separately and in combination. The measurement of contraction gaps at the restoration-dentin interface was used as the means of testing the effectiveness of dentin adhesion. The effect of thermal stress on the dentin-polymer bond was also investigated. Results showed that the bisphenyl A glycidyl methacrylate (BISGMA)-based dentin adhesive was more effective when compared with the hydroxyethyl methacrylate (HEMA)-based adhesive. When used in combination, the mean contraction gaps of cavities were not found to be significantly better than those treated with only the BISGMA-based adhesive. Thermal stress reduced the effectiveness of dentin adhesives whether applied individually or in combination.