THE INFLUENCE OF ULTRAVIOLET-RADIATION INTENSITY ON CURING DEPTH OF PHOTO-ACTIVATED COMPOSITE VENEERING MATERIALS

Light intensity and wavelength distribution affect post-cure propertie s of photoactivated composite materials. This study examined curing de pth of composite veneering materials polymerized with a laboratory pho to-curing unit for the purpose of evaluating the influence of ultravio let radiation (UV) intensity on depth of cure. Three microfilled compo site materials designed for prosthetic veneer were assessed. Two mater ials (Axis and Thermoresin LC II) were activated by both UV and visibl e radiation, whereas the other material (Dentacolor) was activated sub stantially by visible light. The light source of the photo-curing unit was a metal-halide lamp that radiates both UV and visible light. The unit was equipped with a removable UV-elimination filter capable of re ducing the UV intensity from 1014.0 mW/cm(2) to 574.0 mW/cm(2). Each o f the three materials was cured with the photo-curing unit for duratio ns of 20, 30, 60 and 90 s both with and without the filter. The depth of cure of the materials was determined using a scraping technique des cribed by the International Organization for Standardization (ISO 4049 ). Three-factor analysis of variance revealed that the depth of cure w as influenced by the type of composite material, by the exposure perio d and also by the use of the filter (P < 0.01). Curing depth of one ma terial (Thermoresin LC II) was significantly greater when the material was exposed without the filter than when the material was exposed thr ough the filter. Among the three materials, the Axis composite demonst rated the greatest depth of cure regardless of exposure time period or filter use.