Changes in the translucency of porcelain and repairing resin composite by the illumination

The objectives were to evaluate the difference in the translucency parameter (TP) by the illuminants, to determine the correlation between the contrast ratio (CR) and three TP values relative to the illuminants, and to measure the correlation between the differences in TP (DeltaTP) and color (DeltaE(ab)*) by the illuminants based on dental porcelain and porcelain repairing resin composites.

Color and spectral reflectance of three shades of one dental porcelain and three porcelain repairing resin composites were measured before and after thermocycling for 3000 cycles relative to the CIE standard illuminants D65, A and F2 over a white and a black backgrounds. Specimen was 1.8mm in thickness after polishing. CR was calculated, and the differences in TP and color caused by the change of illuminants were compared. Three-way analysis of variance by the material (porcelain or resin composite), shade and illuminant was used to compare differences (alpha=0.05).

The TP value was influenced by the illuminant (p<0.05), and the TP values relative to the illuminants A and F2 were higher than those relative to D65. The correlation coefficients between the CR and three TP relative to the three illuminants were around -0.95. Color difference was positively correlated with the difference in translucency in resin composites (r=0.65 between A and D65 and 0.47 between F2 and D65), but was negatively correlated in porcelain (r=-0.37 between A and D65 and -0.69 between F2 and D65).

Difference in translucency by illumination should be considered when matching shade of porcelain and repairing resin composite.