Factors affecting cure at depths within light-activated resin composites

Abstract

When confronted with all the variables that are influential in maximizing the cure in light-activated resin composites, a practitioner may require information that ranks the relative importance of these parameters, so that clinical time can be best utilized. The purpose of this study was to determine simultaneously the relative impact of filler type (hybrid or microfill), composite shade (universal or gray), exposure duration (20, 40, 60 and 80 seconds) and source intensity (800, 578, 400 and 233 mW/cm2) on the extent of cure in light-activated composite at selected depths (top surface, 1, 2, and 3 mm) of a simulated restoration. Thin wafers of composite (P-50 and Silux Plus) were made between a cured composite underlay and varying thicknesses of cured overlay to obtain a wafer that reproduced the curing environment within a cylinder of composite. The monomer conversion of each specimen was obtained by infrared spectroscopic techniques. Analysis of variance was used to determine the significance of factors contributing to the cure of composite at each thickness of overlay used. At the surface, filler type, exposure duration and resin shade predominated as the most influential factors respectively. At 1 mm depth, the order of influential factors were exposure duration, filler type and source intensity. At depths of 2 mm and more, the overwhelming influences on cure were related solely to source intensity and exposure duration. Resin shade and filler type exerted minimal influence at these depths.