Optical properties of enamel and translucent composites by diffuse reflectance measurements

Objectives: The aim of this study was to evaluate the optical properties of natural enamel and translucent composites by diffuse reflectance measurements and Kubelka-Munk's theory. Methods: Twenty natural enamel slabs and 80 composite replicas using four brands of translucent composites (Gradia Direct, Venus (TM), Brilliant New line and Beautiful II; n = 20) were evaluated at thicknesses of 1.0 mm. The spectral distributions of enamel and composites were measured by means of a reflectance spectrophotometer. Optical constants including scattering coefficient (S), absorption coefficient (K), light reflectivity (RI) and infinite optical thickness (X-infinity) were calculated from the spectral reflectance data using Kubelka's equations. Paired t-tests were performed to evaluate the differences of optical constants (S, K, RI and X-infinity) between natural enamel and composites. Results: The optical constants S and K decreased with increasing wavelength, while RI and X-infinity increased with increasing wavelength within the visible spectrum. The values of enamel were in the range of the optical constants of these composites within the visible spectrum. However, there were significant differences of optical constants (S, K, RI and X-infinity) between enamel and translucent composites (p < 0.05). Conclusions: The optical constants of translucent composites were not completely consistent with that of natural enamel. In addition, the optical properties of these translucent composites varied with the brands of the composites. (C) 2012 Elsevier Ltd. All rights reserved.