Influence of refractive index on optical parameters of experimental resin composites.

Color characteristics of the experimental resin composites were determined to know the influence of different refractive index (RI) on optical parameters. Four experimental light-cured resin composites of the same shade but with different RI were used. The colorimetric values of the specimens were measured against black and white backgrounds using spectrophotometry. The results were converted to CIE L*a*b* color-space values. The chroma (C*ab), color difference (ΔE), translucency parameter (TP) and opacity (OP, opposite property of TP) values were calculated. Surface gloss (GS) of the specimen was also measured. The L* coordinate, a* coordinate and ΔE*ab values increased as the difference in RI increased. The OP and GS values increased and the TP values decreased as the refractive-index difference increased. The L* and C*ab values increased as the value of the RI increased. The TP, OP and GS values were highly correlated with the RI value. The TP value decreased and the OP and GS values increased, as the RI value increased. Refractive index of resin composites is important when thinking about improving the color appearance of esthetic restorations.