CURE BEHAVIOR OF VISIBLE-LIGHT ACTIVATED DENTAL COMPOSITES .2. NONISOTHERMAL KINETICS

In this paper, the non-isothermal cure behaviour of a dental composite , activated by visible light, is described using a heat transfer model that, coupled with a reaction kinetic expression, is able to predict the temperature and the degree of reaction in the composite. The tempe rature and the degree of reaction profiles inside the composite are ca lculated, as a function of the cure time, taking into account the syst em geometry, the thermal diffusivity of the composite, and the resin r eaction rate. Material properties, boundary and initial conditions and the kinetic behaviour are the input data of the heat transfer model. Once the degree of reaction is known, the glass transition temperature profiles across the thickness of the composite are calculated. Experi mentally measured glass transition temperatures are used for the evalu ation of an extinction coefficient capable of accounting for the effec ts of the light absorption through the thickness on the polymerization kinetics. Finally, the effects of the non-isothermal cure conditions on the application of these materials in dental restorations are discu ssed.