Methods:Three photo cured disc specimens of different material thicknesses (x=0.55 to x=1.46mm) were made from four dental resin-composites of different matrix type, particulate filler type and loading. The reflectance measurements (n=3) were made using an Ocean Optic USB4000 Fibre Optic Spectrometer operated by Spectra Suite software and a light source. The spectra was analysed by mean values of reflectance, at intervals of 100nm light wavelengths in the range 500-800nm.Contrast ratio and contrast gloss values were calculated from f reflectance measurements. Data were analysed using One-way analysis of variance (ANOVA) combined with a Tukey multiple test.
Results: Significant differences (p< 0.05) were found in the reflectance (specular and diffuse) values as well as contrast gloss and contrast ratio with increasing material thickness and light wavelength. Linear regression analysis of specular reflectance (white background) with light wavelength at a material thickness ca 1.00mm gave R2 values ranging from 0.81 to 0.99 for all the materials. Also for diffuse reflectance with light wavelength at a material thickness ca 1.00mm gave R2 values ranging from 0.81 to 0.99 for all the materials.
Conclusions: Material thickness, light wavelength and material composition affected the specular and diffuse reflectance, contrast gloss and contrast ratio. The differences in the reflectance and contrast ratio and contrast gloss will significantly affect the clinical appearance of the materials.