Temperature rise in ion-leachable cements during setting reaction.

Resin-modified ion-leachable cements have been developed for use as aesthetic restorative materials. Their apparent improved physical and handling properties can make them more attractive for use than conventional glass-ionomers. However, they contain monomers which are known to contract on polymerization and produce a polymerization exotherm. This study evaluated the temperature rise during setting and the rate of dimensional change of several ion-leachable materials. The resin-modified ion-leachable cements demonstrated greater temperature rises and higher rates of contraction than conventional materials. Generally, the behaviour of these resin-modified materials was similar to that of composite resins. However, some resin-modified cements produced a temperature rise of up to 20 degrees C during polymerization which was greater than that of the composite resin. This temperature rise must be taken into account when using the materials in direct contact with dentine in deep cavities without pulp protection. Longer irradiation time than the recommended 20 s did not significantly increase the maximum temperature rise but slightly extended the time before the temperature started to decline. The temperature of the environment had a significant effect on the rate of dimensional change in some materials. The rate of polymerization contraction of light-activated cements was directly related to the observed temperature rise.