The effects of gamma radiation on the properties of composite restorative resins

The effects of gamma radiation at therapeutic dosage levels on the physical properties of three anterior (two light-cured and one autocure) composites and a light-cured posterior composite were studied. Gamma radiation had no effect on the autocured composite but had varied effects on the light-cured systems. The diametral tensile strength and dimensional stability were unaffected, water sorption and solubility were reduced but surface and bulk hardnesses were increased with the hardness increases linearly related to the radiation dosage. These effects may arise from continued polymerization of the air-inhibited surface layer and possibility of low molecular weight entities within the matrix. Overall, therapeutic levels of gamma radiation had no detrimental effects on the physical properties of the composite resins.