The effect of different preheating methods on the intrapulpal temperature of bulk-fill composite resins

This study aimed to evaluate the effect of various preheating methods applied to bulk-fill composite resins on temperature changes within the pulp chamber. Ten sound human molars were used. Each tooth was sectioned 2 mm apical to the cementoenamel junction, and the occlusal surface was flattened to leave a 2 mm dentin thickness. Four bulk-fill composite resins were applied at five temperatures (24 °C, 37 °C, 54 °C, 65 °C, and 68 °C) and polymerized using an LED curing unit. Intrapulpal temperature changes were measured with a K-type thermocouple connected to a data logger in a setup simulating pulpal microcirculation. In total, twenty measurements were taken per tooth under each condition. Data were analyzed using one-way ANOVA and post-hoc LSD tests (p < 0.05). The highest intrapulpal temperature increase was observed at 65 °C in all groups using the VisCalor dispenser. The critical temperature threshold was not exceeded in any sample. Significant differences were found between certain temperatures within individual resin groups (p < 0.05), particularly at 65 °C compared to lower temperatures. However, no statistically significant differences were found between different resin types at the same temperatures (p > 0.05). Preheating of bulk-fill composite resins led to an increase in intrapulpal temperature; however, this rise remained below the threshold that could cause irreversible pulpal damage. Preheating bulk-fill composites enhances handling and adaptation but may increase intrapulpal temperature. In this study, the temperature rise remained below the critical threshold, suggesting that the procedure is clinically safe.