Influence of refractive index on optical parameters of experimental resin composites

Abstract

Objective. Color characteristics of the experimental resin composites were determined to know the influence of different refractive index (RI) on optical parameters. Materials and methods. 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. Results. 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. Conclusions. Refractive index of resin composites is important when thinking about improving the color appearance of esthetic restorations.

Key Words::

• color
• resin composites
• refractive index
• CIE L*a*b*

Acknowledgement

This work was supported, in part, by Grant-in-Aid for Scientific Research (C) number 20592237 from the Japan Society for the Promotion of Science (JSPS), by the Sato Fund, and by a Grant from the Dental Research Center, Nihon University School of Dentistry, Japan.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.