title: 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 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.
authors.affiliation: Tokyo Medical and Dental University, Faculty of Dentistry, Department of Operative Dentistry, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Inokoshi
authors.forename: M F
authors.initials: MF
authors.lastname: Burrow
authors.forename: M
authors.initials: M
authors.lastname: Kataumi
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: T
authors.initials: T
authors.lastname: Takatsu
mesh_terms: 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
chemical_list: D003188:Composite Resins; D005899:Glass Ionomer Cements; D011108:Polymers; D019279:Resin Cements