The rate of post-exposure polymerization and the effects of initial polymerization on the final polymerization of visible lightactivated composite resin were studied. The extent of polymerization, as indicated by hardness values, was influenced by the exposure time to the photo-activating radiation and by the postexposure time. The timing of testing is critical when studying the properties of visible light-activated composite resins.

Water sorption values for direct filling resins and an unfilled resin were much more similar at 30 days when expressed as mg/g organic matrix than as mg/cm2 or weight percent. This interpretation is indicative of the water sorption characteristics of resin matrices. The values are even more indicative when solubility or leaching is taken into consideration. With the specimen sizes used in this study, the effect of the kinetics of water sorption could be minimized by using values obtained after immersion in water for 30 days.

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