Abstract
It is very important to investigate the mechanism for shrinkage in composite resin during hardening, because the developing force caused by the shrinking of composite resin in the cavity applies stress to human tooth tissue.In this study, the apparatus was prepared to measure the developing force in composite resin during hardening.The shrinking stress in a different curing type of composite resin, light cured and chemically cured type, was observed, and then the mechanism of shrinkage in composite resin was discussed.Initially, the shriking stress of composite resin increased dramatically.Later, the shrinking stress suddenly decreased, which indicates the detachment at the interface between the composite resin and the cavity wall.The shrinking stress obtained with the open type cavity was smaller than that obtained with the closed type cavity, and the shrinking stress of the chemically cured resin appeared faster than that of the light cured resin, but the maximum value of the shrinking stress was the same.
