Pulpal-temperature rise and polymerization efficiency of LED curing lights

Prior research has shown that light curing systems influence polymerization efficiency and pulp chamber temperature. Established knowledge includes the role of irradiation time and light wavelength in material hardness. However, this gap motivated a study on how specific LED systems affect dual-photoinitiator composites. No prior work had resolved the interplay between light characteristics and material shade. The need to balance polymerization and pulp safety remains unresolved in dental practice. This paper's contribution lies in comparing multiple LEDs and a halogen light. The study addresses variability in material formulations and curing protocols. It builds on prior findings about dual-photoinitiator composites.

The aim of this research was to evaluate how different LED curing lights affect polymerization efficiency and pulp temperature. The specific problem addressed is the variability in curing outcomes based on light characteristics and material shade. Motivation stems from the need to optimize both hardness and thermal safety in dental restorations. The study tests whether certain LEDs can replace halogen lights without compromising quality. It also examines the impact of irradiation time on polymerization. The goal is to identify LEDs that match or exceed halogen standards. The research focuses on dual-photoinitiator composites used clinically. It seeks to clarify the relationship between light parameters and material performance.

The study tested four LEDs and one halogen light on two composite shades. Each LED was applied for 10, 20, or 40 seconds. Vickers microhardness was measured on upper and lower surfaces of 2-mm samples. A K-type thermocouple monitored pulp chamber temperature during irradiation. The setup included a prepared molar with a 2-mm dentin layer. Data were collected for both filled and empty molds. Two-way ANOVA analyzed the results with p < 0.05 significance. The method compared LEDs against a halogen light as a control. It assessed both material hardness and temperature rise.

For shade A2, all but one LED condition (F2-10 seconds, lower surface) achieved hardness equal to or better than the halogen control. For Bleach shade, G and BG2 at 20 and 40 seconds matched halogen standards. At 10 seconds, G and BG2 failed to meet the reference hardness. Other LEDs showed lower hardness on at least one surface. Temperature increases were higher with LEDs than with the halogen light. B16i, BG2, and G at longer times caused the highest deltaT. Uncovered teeth showed higher temperatures than those with composite layers. The results highlight shade-dependent differences in polymerization and thermal response.

The authors state that matching light and material spectra is crucial for optimal polymerization and pulp safety. Some reduction in curing time is possible but limited. No LED fully replaced the halogen standard in all conditions. The study emphasizes the need to consider both hardness and temperature when selecting curing lights. The findings suggest that longer irradiation times are safer for pulp chamber heating. Material shade significantly affects both polymerization and thermal outcomes. The authors propose that LED selection should align with material photoinitiator profiles. They conclude that current LEDs require careful use to avoid undercuring or overheating.