Spatially Distributed Light Exposure: Impact on Light Transmission through CAD/CAM Resin-Based Composites of Different Thicknesses

Abstract

This article reports the variation in incident and transmitted light through four different computer-aided-designed/computer-assisted-manufactured (CAD/CAM) resin-based composites (RBC) of thicknesses up to 4 mm after simulating clinically relevant but non-ideal curing conditions. A violet-blue light curing unit (LCU) was used to simulate 39 different curing conditions for each material and thickness, setting an exposure distance of up to 7 mm in the vertical direction and an additional 13 horizontally varying positions that included a central position and up to 3 mm off-center positions in mesial, distal, buccal, and lingual directions. The data clearly indicate that exposure distance has a stronger influence on the measured light characteristics than the directional and offset deviations from the center position. Increasing exposure distance leveled the differences and should be limited to 3 mm. In all materials, the parameters of the transmitted light follow the pattern of variation of the incident light. The attenuation of light while passing RBCs is high and increases exponentially with thickness to 95–96% of the incident light for 4-millimeter-thick samples. Significant differences in light transmission were observed between the materials, which are well related to chemical composition and refractive index differences between filler and organic matrix. Violet light is still measurable after passing through 4-millimeter-thick RBC layers, but its proportion relative to blue light is drastically reduced.