Five-year color changes of light-cured resin composites: influence of light-curing times.
OBJECTIVE
The purpose of this study was to investigate the influence of light-curing times on the color changes of light-cured resin composites, over specified periods of time.


METHODS
Silux Plus (3M Dental Products) light-cured resin composite disks (shades: U, Y, DY, L, G, UO, YO), 10 mm in diameter and 1 mm in thickness were prepared with 20, 40, and 120 s of light exposure through a 1 mm thick glass plate. The specimens were stored in artificial saliva at 37 degrees C. Colorimetric values of the specimens immediately after curing and after every 6 months for 5 years were measured backed by a light trap, and a white colored plate using a fast spectrophotometer. The CIE 1976 L*a*b* color system was used for the determination of the color difference.


RESULTS
For specimens backed by a white colored plate, the delta E*ab of all shades increased for 3 years and 6 months to 5 years, to the time elapsed during all curing times. However, the a*b* values to the time elapsed differed among the shades and light curing times. In the 20 and 120 s curing time groups, the opacity% of all shades increased for 4 or 5 years to the time elapsed.


CONCLUSIONS
The modes of color changes of Silux Plus resins differed among the shades and light curing times.
Hosoya
Y
Y
Department of Pediatric Dentistry, Nagasaki University School of Dentistry, Japan. hosoya@net.nagasaki-u.ac.jp
D000704:Analysis of Variance; D003116:Color; D003124:Colorimetry; D003188:Composite Resins / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D017797:Prosthesis Coloring; D018709:Statistics, Nonparametric; D013997:Time Factors
D003188:Composite Resins; C074741:Silux Plus