Correlation of Power Density with Simulated in-Vitro Intrapulapal Temperature Rise

OBJECTIVE: To determine the correlation of applied curing light power density and resultant intrapulpal temperature rise in-vitro.   METHODS: Twenty three commercial dental light curing units (21 LED, 1 PAC, 1 QTH) were measured for irradiance at the tip end using a laboratory grade spectral radiometer (DAS-2100, Labsphere).N=5 The same lights were shown on the facial surface of an extracted human bifurcated bicuspid having a Class V preparation with 1 mm remaining dentin thickness (approved MCG HAC protocol #02-10-104).  The tooth was immersed in temperature-controlled water up to the CEJ water bath.  Using tubing, water entered one root end and exited the other at a similar temperature as the water bath and at a physiological intrapulpal blood flow rate (0.0123 mL/min) using an infusion pump.  Temperature was monitored on the pulp chamber wall directly behind the axial wall of the preparation using a K-type thermocouple.  Thermocouple output was directed to a cold-junction compensating/A-D converter (DAQPad-6020e, National Instruments) and was recorded in units of temperature (Deg C) and read in real time on a PC. Temperature rise from physiologic intrapulpal baseline level (34°C) at 10-seconds exposure was recorded. (N=5) For each light used, mean irradiance and mean temperature rise values were plotted, and the intrapulpal temperature was predicted from irradiance values using linear regression analysis.   RESULTS: Data passed both the normality (p=0.827) and constant variance tests (p=0.058). Temperature rise was highly correlated to applied irradiance (p < 0.001).  The predicted correlation determined was: Temperature Rise (Deg C) = 0.191+(0.00254*Irradiance (mW/cm²), with an R-squared value of 0.758.   CONCLUSION: Using this in-vitro temperature-compensated, fluid-flowing tooth model, intrapulpal temperature rise was found to be correlated with increased curing light irradiance in a direct, linear manner.