Characterization of time-dependent mechanical behaviors of dental composites by DIC

Dental resin composites are widely applied in dental restoration. These resin composites have some problems due to shrinkage occurred. Since shrinkage stress could be presented by resin matrix polymerization as tensile stress and causes structure failure. In this study, four types of dental composites (Z350 flow, universal composite Z250, packable composite P60, and low-shrinkage composite LS) were chosen to investigate their tensile creep and recovery behavior. The specimens were divided into two groups: (1) after curing about 5 min, and (2) stored in artificial saliva for 30 days. With force control, the specimen image under uni-axial tension was recorded and analyzed by using digital image correlation (DIC) method. Four-parameter fluid model is found applicable to fit the experimental obtained strain. The results showed that the longitudinal strain of 5-min case has higher creep and residual strain than that of 30 days. The creep of LS was the smallest in four resin composites. The Poisson’s ratio of 5-min case was increased about 0.5 with time except for LS. However, the Poisson’s ratio of 30-day cases varied up and down insignificantly with time.