Effect of Refractive Index Mismatch to Translucency of Dental Composite.

Objectives: When dental filling composites absorbs light from the surrounding tooth structures, it creates a color-match, which is known as “a chameleon effect”. In this study, series of co-monomer mixtures were prepared with an increasing refraction index (RI) and mixed with glass fillers. The aim of this study was to optimize mismatch of refraction index of resin/fillers to form the chameleon effect.
Methods: BisGMA/TEGDMA resins were prepared with seven different mix fractions from 20 % to 80 %. In addition, 0.7%wt camphorquinone and DMAEMA as activator were added. Two different series with 0.7 micron silanized fillers (70% wt%) (Schott-RI=1.53, Esschem RI=1.54) were mixed with resins (30wt%). Disc-shaped specimens (1 mm thickness, Ø10mm) for each composite combination (n=3) were prepared after light cured for 20 seconds. Control groups were commercial dental composite (OmniChroma, Tokuyama Dental Corp., Japan). The translucency parameter (TP) was measured using a spectrophotometer (CM-700d, Konica Minolta Sensing, INC). Data was statistically analyzed using ANOVA (SPSS).
Results: Composition of resin and type of fillers had statistically significant effect on TP-values (p<0.05). In both series the highest TP values were achieved of 50 %-50 % fractions of BisGMA and TEGDMA. With high or low BisGMA content of composite revealed more translucent composite. TP values are shown on Table 1.
Conclusions: Refraction index of fillers and monomer system influenced light scattering and translucency of resin composite. By optimizing these parameters resin composite can be tailored for providing “chameleon effect”.