Effect of Multiple and Single Emission Peak Light Emitting Diode Light Curing Units on the Degree of Conversion and Microhardness of Resin-Based Pit and Fissure Sealant

Objective: To assess a multiple emission peak light-emitting-diode (LED) light-curing unit (LCU) by measuring the polymerization efficiency through the degree of conversion (DC) and Knoop microhardness (KH) of a resin-based pit and fissure sealant at various light curing times and two distances compared to a single emission peak LED LCU. Method: Sixty disks of a resin-based pit and fissure sealant (Delton, DENTSPLY, York, PA) samples (6 x 1 mm) were fabricated. Prepared specimens were polymerized using 10, 20 and 40 second curing times at 2 or 4 mm curing distances (n = 5/LCU/group). A Managing Accurate Resin Curing System-Resin Calibrator was used to ensure that irradiance delivered from the LED LCUs remained consistent throughout the study. Samples were stored at 37°C for one hour. Then, the DC (n = 3/surface) and KH (n = 5/surface) measurements were obtained on the top and bottom surfaces using an Attenuated Total Reflection-Fourier transform infrared spectroscopy (Pike analytics and Jasco) and a Knoop microhardness tester (Instron) utilizing 25 gm at 10 second dwell time, respectively. Multiple-way ANOVA was performed followed by Fisher’s test (α = 0.05). Results: The multiple emission peak LED LCU displayed significantly higher DC (27.7 81.4 %) and KH (10.0 23.0 kg/mm2) compared to the single emission peak LED LCU; DC (20.4 74.8%) and KH (4.8 19.6 kg/mm2) when curing specimens at 2 and 4 mm curing distances assessed using 10, 20 and 40-second curing times. The 10 second cure at 4 mm showed significantly lower DC and KH values compared to the other times and distances tested. Conclusion: The multiple emission peak LED LCU demonstrated significantly higher DC and KH compared to the single emission peak LED LCU when using a resin-based pit and fissure sealant assessed regardless of the curing distance or curing time.