Discoloration of Coating Resins Exposed to Staining Solution

―The Influence of Different Surface Conditions―

抄録

This study evaluates in vitro the effects of discoloration induced by coating resins under various polymerization conditions. Two coating resins (WTC and BTC) were used. Disk specimens (diameter: 15.0 mm;thickness: 0.7 mm) were used uncoated, coated with a polyethylene film, or coated with an application of TopCoat for WTC or GlossRefine for BTC. Five specimens were immersed for 72 h in a staining solution of either coffee or water. The CIELAB coordinates (L*, a*, b*) of each specimen were measured against a black background using a colorimeter (Shade Eye, NCC) and the color difference [ΔE] was estimated and analyzed by one-way ANOVA and Tukey comparison. The specimen surfaces were observed by FE-SEM. The results reveal that for both materials, the uncoated group had the highest ΔE values (p<0.05). For the other groups, the ΔE values for WTC were higher than those for BTC (p<0.05). The surfaces of both materials contained fillers of various sizes and shapes. For all groups, WTC had much smaller fillers than BTC. Both White Coat and BTC exhibited a color change after 72 h under all conditions (ΔE>3.6). Coffee discolored the coating resins. Oxygen inhibition significantly affected the discoloration of the coating resins. We propose applying a coating agent for WTC and a glazing agent for BTC to suppress discoloration of coating resins.