The purpose of this study was to evaluate the color changes of the composite resin resulting from xenon lamp exposure in different environments. Composite resin (Z 250 ; shade A1, A2, A3, A3.5, and A4) were applied in a cylindrical metal mold. Seventy five specimens according to environments of exposure were made as follows;
Group I: aluminum foiling of the specimens in the air at 37℃ for 1 day and 7 days.
Group II: exposure of xenon lamp to the specimens in the air at 37℃ for 1 day and 7 days.
Group III: exposure of xenon lamp to the specimens in distilled water at 37℃ for 1 day and 7 days.
The color characteristics (L*,a*,b*) of the specimens before and after exposure of xenon lamp were measured by spectrophotometer and the total color differences (ΔE*) were computed.
The results obtained were as follows:
In all groups except A1 shade of group III, the ΔE* values presented below 2.0, and group III showed the highest ΔE* values followed by group II and group I in a decreasing order(p<0.05).
In all shades and groups, the more the exposure time of xenon lamp and the lighter the shade were, the higher the tendency for discoloration (p<0.05).
The composite resins which was exposed to xenon lamp in the distilled water was more discolored than those in the air (p<0.05).
The major changes of composite resins which were exposed to xenon lamp in the air were an increase in yellowness through a positive shift of the b* value, and those in the distilled water were an increase in darkness and yellowness through a negative shift of the L* value and a positive shift of the b* value.
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