Intrapulpal Temperature Changes Induced by Various Light - curing Units

Objectives: The aim of the present study was to compare the temperature increase in pulp chamber by various light-curing units during composite resin polymerization and to determine the effect of remaining dentin thickness on temperature rise. Methods: A Class II occlusodistal cavity with a remaining dentin thickness of 2 mm was prepared in an extracted human mandibular molar tooth. A 2mm layer of fine hybrid composite resin was placed on the floor of the proximal box. A K-type thermocouple was inserted into the pulp chambers and temperature rise during polymerization of composite was measured. The light-cuing units tested included two halogen lights; Spectrum 800, Elipar Trilight (Standard and Exponential mode), a light emitting diode (LED; Elipar Freelight) and a plasma arc (Virtuoso, Xenon Power Arc). Five measurements were carried out for every light-curing unit. The same experimental design was conducted after the cavity preparation was modified and leaving a dentin layer 1mm thick. Kruskal-Wallis and multiple comparison test were used to evaluate the differences among the tested curing units. Mann Whitney-U test were used to compare the mean temperature rise in each curing units for different remaining dentin thickness. Results: The highest temperature rise was observed when using EliparTrilight Standard mode and the lowest with LED for both remaining dentin thickness. The only significant differences in temperature rise were observed between Elipar Trilight Standard mode and LED. Statistically significant higher temperature rise was observed within each curing unit at depth of 1mm compared to 2mm.. Conclusion: Although the tested light-curing units caused a temperature rise in the pulp chamber, none of them exceed the critical value of 5.5. The thickness of the residual dentin is a critical factor in reducing thermal transfer to the pulp and this transfer varies with the curing unit used