In vitro changes in pulpal temperature during light exposure at different pulpal fluid flows

This in vitro study evaluated the effect of three different fluid flow rates on the pulp temperature (PT) of an empty Class II cavity using three high-powered light-curing units (LCUs): Bluephase PowerCure (Ivoclar Vivadent), PinkWave (Vista Apex), and Valo X (Ultradent), using both 10 s (normal) and their highest irradiance, shortest exposure modes. The spectral radiant power, irradiance, and radiant exposure delivered from each LCU were measured using an integrating sphere. A T-type thermocouple was placed inside the pulp chamber of a human molar with a Class II cavity. Three different pulpal flow rates were evaluated: 0.026 mL/min, 0.2 mL/min and 1 mL/min. After reaching a baseline of 32 °C, PT measurements were recorded every 0.5 s before, during and after light exposure (n = 5). The temperature increases (ΔT) for the different light conditions at the different fluid flow rates were analyzed using ANOVA followed by the Tukey post hoc tests (⍺ = 0.05). No significant changes in PT were found between pulpal fluid flow rates of 0.026 mL/min and 0.2 mL/min, but there was a lower PT when the pulp fluid flow was increased to 1 mL/min. The LCUs produced different ΔT. The PT rise was directly associated with the radiant exposure (J/cm²) and spectral radiant power delivered by each exposure mode. The PinkWave-10 s produced the greatest ΔT across all the simulated pulp fluid flow rates (2.7 °C ± 0.3 at 1 mL/min; 3.8 °C ± 0.4 at 0.026 mL/min). The PowerCure-3 s and PinkWave-3 s produced the smallest ΔT (p ≤ 0.05).