Opacity and color changes of tooth-colored restorative materials

Abstract

Internal opacity and color changes of several esthetic direct restorative materials were determined using an accelerated test proposed by Asmussen (1981). Five chemically cured composites, seven light-cured composites, and three resin-modified glass-ionomer cements were placed in acrylic rings. After curing, they were left at 37°C for 1 week before baseline measurement, and then stored in 60°C distilled water up to 4 weeks. Color change was determined by a color analyzer, and contrast ratio representing opacity was calculated. All chemically cured composites tested discolored to dark yellow or dark brown after 4 weeks. Opacity decreased for two macrofilled composites. Light-cured composites discolored slightly, but their opacity change was negligible. All resin-modified glass-ionomer cements tested showed an abrupt decrease of opacity at the initial stage, accompanying darkening of the materials. Opacity decrease was found to be a factor of discoloration for some tooth-colored restorative materials, might be caused by a refractive index change of the matrix phase of the materials. ©Operative Dentistry, 1996.