Optical transmission analysis by visible light into resin composite inlays: effect on curing of underlying resin cement

ABSTRACT

The penetration of visible light into dental materials is an essential factor in photoinitiation of setting reaction and in optical aspects of dental aesthetics. Recently, the indirect composite restoration is a versatile technique for aesthetic restoration of posterior teeth. This technique offers improvement in overcoming some of the problems associated with direct placement composites. However, the indirect procedure remains technique sensitive principally related to the luting agent used to bond the resin composite inlay to the tooth structure. The purpose of the present investigation was to analyse the optical transmission through different indirect resin composite restorations. The effect of the material, shade, thickness and surface finish on light energy transmission was investigated. The effect of transmitted light on resin cement polymerization was also in vestigated. Two commercially available visible light-cured resin composite materials, with two different shades each, were used in this study. A total of 160 resin composite specimens 10 mm in diameter with different thickness ranging from 1 to 4 mm were prepared and visible light-cured according to the manufacturer's instructions. Half of the specimens were prepared against Mylar strip, while the rest of the specimens were finished with silicon carbide paper. Specimens were dry stored at 37°C for 24 hours before testing. The amount of light energy transmitted through various thickness and shades of each light-cured resin composite was measured using spectrophotometer and its influence on degree of conversion of the resin composite luting cement was studied. Data were collected and statistically analysed. It was concluded that the improved light transmission through the indirect resin composite restorations and consequent adequate polymerization of the underlying resin cement couldn't be generalized for all condensable resin composites. The predominant influencing factor was the compositional pattern of the resin composite. Both thickness and shade of the resin composite inlays were the overwhelming factors affecting the light transmission and curing of the underlying luting resin cement. Lighter shades and lower thickness resin composite inlays would guarantee better light transmission and resin cement polymerization. Surface finish of the inlay was not an efficient factor in light transmission and curing of resin cement. If photoactivated resin cement has to be used for a resin-based restoration, the attenuation of the curing light through the restoration must be taken into consideration