Effects of Backing Reflectance and Mold Size on Polymerization of Photo-activated Composite Resin

The in vitro depth of cure of a visible-light-activated microfilled composite, as influenced by backing reflectance and mold size, was investigated using microhardness measurements. More extensive polymerization was obtained with higher values of backing reflec-tance. Mold size larger than the cross-sectional area of the photo-activating beam also increased the degree of polymerization. Back-ing reflectance and mold size are influential factors and need to be defined in depth-of-cure evaluations if in vitro measurements are to be valid predictors of clinical performance