Temperature rises beneath composite restorations during curing

Objectives: Temperature rise in the pulp chamber can occur during composite resin light polymerization. The increased temperature can cause irreversible damage to the pulp tissue. The purpose of this study was to compare the thermal emission of five light cure units while curing two different composite materials. Methods: The thermal emission of the different lights units was measured and compared: Three LED (Elipar Freelight 2; Bluephase; Radii), one halogen (Demetron 501), and one plasma arc (ESC Medical Systems Ltd, Israel). LED and halogen units were used for 40s and plasma arc for 6s according to manufacturer's instructions. Thermal emission was assessed using a K-type thermocouple and a digital thermometer with various curing distances (0mm, 3mm and 6mm), various materials thickness (1mm, 2mm and 4mm), and two restorative materials (Gradia Anterior and Filtek Supreme). Statistical processing was done using a 4 course variance analysis on ln transformation of the maximal temperature and a Tukey test for multiple comparisons. Results: Thermal emission of LED lights was significantly higher than the halogen light. Plasma light showed the most diminished thermal emission. Temperature rise was significantly higher when using Gradia Anterior than with Filtek Supreme. There was an inverse ratio between the thickness of the material and the thermal emission that was measured and between the distances of the light tip from the restorative material. Conclusions: When polymerizing composite resin for 40s LED units emitted more heat than halogen units and different composite resins conduct heat differently.