Experimental studies of composite shrinkage of dental restorations

Abstract

Dental composites are light-curable resin-based materials with an inherent defect of polymerization shrinkage which may cause tooth deflection and debonding of restorations. The shrinkage behaviors of dental composites under four different light curing regimens were investigated by using digital image correlation (DIC) method. Experimental results showed that the shrinkage in unbonded restorations has the greatest shrinkage strain on the top surface. The bonded restorations did not show a typical centripetal shrinkage patterns as their unbonded restorations, and had greater downward displacements. Vertical curing at regular intensity caused the greatest shrinkage strain. Low-intensity curing reduced overall shrinkage at cervical margin, but did not prevent debonding after storage. Oblique curing caused asymmetric shrinkage with less deformation at tooth-shielded side and reduced shrinkage due to the attenuated polymerization rate rather than guided shrinkage direction. This studies may provide useful information for clinical usage, and further stress analysis by numerical methods.