Curing characteristics of a composite. Part 2: The effect of curing configuration on depth and distribution of cure

ObjectiveThe objective of this study was to examine the effect different configurations of curing would have on the depth and distribution of the cure within each configuration, for a specific resin-based composite (RBC).MethodsRBC was cured in a variety of configurations, consisting of 6 mm molds of three different colors; large molds that simulated the condition of no mold at all; and 3–6 mm diameter molds to check the effect of size. All specimens were cured for 20 s with a quartz-halogen lamp and were allowed to cure for 24 h in the dark. Transmission measurements were made for these same configurations. Knoop hardness measurements were made across the central plane of some configurations to determine the distribution of curing.ResultsDepths of cure and distribution of curing were significantly affected by changes in configuration. Under the configuration of no mold, the cure extended well beyond the periphery of the light guide due to scattering of the light. When a mold was used, a pronounced effect by the walls resulted in decreased hardness as the mold wall was approached, and the severity of this effect was dependent on the color of the mold. It is believed that this is due to absorption/reflection characteristics of light by the walls, with the white molds showing the least effect. Reducing the diameter of the molds resulted in significant decreases in depth of cure, which are attributed to light absorption by the walls that limits the penetration of light during the curing procedure.SignificanceConfiguration of curing has a significant effect on the depth of cure, but also significantly reduces the cure near the mold wall. This can have clinical ramifications for the cure along a stainless steel matrix band for Class II restorations, and for test procedures in general, where there is no standardization regarding configuration or where measurements are made on specimens.