Opacity and color changes of tooth-colored restorative materials.
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 degrees C for 1 week before baseline measurement, and then stored in 60 degrees 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, with accompanying darkening of the materials. Opacity decrease was found to be a factor of discoloration for some tooth-colored restorative materials, and might be caused by a refractive index change of the matrix phase of the materials.
Inokoshi
S
S
Tokyo Medical and Dental University, Faculty of Dentistry, Department of Operative Dentistry, Japan.
Burrow
M F
MF
Kataumi
M
M
Yamada
T
T
Takatsu
T
T
D000704:Analysis of Variance; D003116:Color; D003188:Composite Resins / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008027:Light; D055095:Optics and Photonics; D011108:Polymers / Q000737:chemistry; D017797:Prosthesis Coloring; D019279:Resin Cements / Q000737:chemistry
D003188:Composite Resins; D005899:Glass Ionomer Cements; D011108:Polymers; D019279:Resin Cements