Light transmission characteristics of dentine and resin composites with different thickness

Objective: The purpose of this study was to evaluate the light transmission characteristics of dentine and resin composites with different thickness. Methods: Disks of bovine dentine and three resin composites (Estelite Sigma, Beautifil II and Clearfil Majesty) of OA2 shade were prepared with various thicknesses (0.5, 1.0 and 2.0 mm). Using a goniophotometer, the distribution graphs of the light transmission intensity of each specimen were obtained, and diffusion factor (DF) as an indicator for a diffuse transmission property and peak-gain (G0) for a straight-line transmission property were calculated. Their colors were measured on black and white backings using a reflection spectrophotometer to calculate translucency parameter (TP). The data of each value (G0, DF and TP) were analyzed by two-way ANOVA and Dunnett's T3 for post hoc test (p = 0.05). Regression analyses were used to determine the correlation between G0, DF, TP values and the thickness. Results: Regardless of the thickness, dentine had lower TP values than the resin composites. 0.5 mm-thick specimens of dentine and resin composite produced various G0 and DF values, with dentine exhibiting significantly lower G0 and higher DF than the resin composites (p < 0.05), whereas with the 1.0 and 2.0 mm-thick specimens, they were closely aligned. For dentine, G0 and DF increased in inverse proportion to the thickness (G0: R-2 = 0.962, p < 0.001; DF: R-2 = 0.891, p < 0.001). Conclusions: Dentine had different light transmission characteristics from resin composite, depending on the thickness. Clinical significance: Dentine has different light transmission characteristics (straight-line and diffusion) from resin composite, depending on thickness. Resin composite restoration might be different to accurately reproduce light transmission characteristics of dentine substrate. (C) 2012 Elsevier Ltd. All rights reserved.