Abstract
The purpose of this study was to investigate the color changes of light-cured composite resins over specified periods of time.
Composite resin disks which were 10 mm in diameter and 1 mm in thickness, and made by the 3M Co. light-cured composite resin Silux Plus (shades: U, Y, DY, L, G, UO, YO) were made with 2 minutes of light exposure through a 1 mm thick glass plate. The spccimens were stored in 37°Cartical saliva.
Chromatical values of the specimens immediately after curing,1 day,1 month,3 months,6 months and 1 year after curing were measured without background color, backed by a white plate.
Color measuring was performed with the Murakami Color Research Laboratory Fast Spectrophotometer CMS-500 and the Flexible Sensor FS-3.
1) In the cases without background color, the ΔE*ab values of all shades increased for 1 year proportionately to the time elapsed. In the cases backed by a white plate, the ΔE*ab values of all shades increased for 6 months after curing, however, compared to the 6 month ΔE*ab values, the 1 year ΔE*ab values increased in some shades and decreased in other shades.
2) Both in the cases of with and without background color, compared to the ΔE*ab values of immediately after curing, the 3 month ΔE*ab valucs of all shades were over 1.2, and the 1 year ΔE*ab values of many shades were near or over 2.5and detectable to the naked eye.
3) Both in the cases of with and without background ccicr, the L* values of all shades decreased for 6 months after curing. However, compared to the 6 month L* values, the 1 year L* values decreased in some shades and increased in other shades.
4) In the cases without background color, the a* values of all shades increased for 1 year after curing. In the cases backed by a white plate, the a* values of all shades increased for 6 months, however, compared to the 6 month a* values, the 1 year a* values of all shades decreased.
5) Both in the cases of with and without background color, compared to the b*values immediately after curing, the 1 day b* values of all shades increased, then the b* values of all shades decreased between 1 day and 1 month after curing, and the b* values of many shades increased between 1 month and 6month, however, compared to the 6 month b* values, the 1 year b* values increased in some shades and decreased in other shades.
