Abstract
The heterogeneities of polymerization of visible light-cured composite resins were investigated by measurments of Knoop hardness and residual monomer in these cured resins. In longitudinal section of specimen, conversion of resin was slightly lower immediately beneath the surface irradiated with light, and became maximum near 0.5mm beneath the surface, and then gradually decreased with depth. In horizontal section of specimen, conversion of resin was highest at center portion and gradually decreased toward cavity wall side. This heterogenities of polymerization were improved by increasing irradiation time and aproaching the light on the surface of material as near as possible. On the basis of hardness (conversion of resin) of chemically-cured composite resin, the clinically effective depth of cure of visible light-cured composite resin seemed to be in the range of 30 to 40% of the apparent depth of cure which generally called “depth of cure”. The visible light-cured resins had more residual monomer than the chemicallycured resin, and which was attributable to the heterogenities of polymerization of the visible light-cured resins. In visible light-cured resins, the material which contained more inorganic fillers with good light permeability, had less residual monomer than ones which contained less.
