Irradiance Quantification from Three LED LCUs at Various Distances

Introduction: Performance of the restoration depends on light irradiance of the light-curing unit(LCU). Maximum light radiation can be observed at the surface of a photoinitiated restoration when the tip of the LCU reaches its closest proximity. Objectives: The objective of this study was to quantify the irradiance of three light-emitting diode(LED) LCUs at different distances. Methods: Three LED LCUs, LCU1(Elipar S-10; 3MESPE, Seefeld, Germany), LCU2(Valo; Ultradent, South Jordan, UT, USA) and LCU5(Bluephase G2; Ivoclar Vivadent, Schaan, Liechtenstein) were mounted on a Marc™ Resin Calibrator (BlueLight Analytics Inc., Halifax, NS, Canada) and tested at 0.0mm up to 12.0mm  with 1.0mm increments. At standard modes all LCUs were set for 10seconds of exposure following manufacture’s recommendation. For Valo at high-power(LCU3) 4seconds was used and for x-high-power(LCU4) 3seconds was used. For low-power(LCU5) and high-power(LCU6) mode of BluephaseG2 also 10 seconds was used as the exposure time. Irradiance was measured at all distances for all LCUs and all power modes. Measurements were repeated three times for each LCU and power mode. Means and standard deviations were calculated. Results were analyzed with ANOVA followed by Tukey HSD test (α=0.05). Results: Means and standard deviations of iradiance (mW/cm²) at 0.0mm were: LCU1(1971.88±4.73); LCU2(1556.13±11.80); LCU3(2142.42±31.20); LCU4(3503.98±64.51); LCU5(660.19±2.83) and LCU6(1116.07±4.04). There was a statistical significant difference of irradiance between all LCUs. Irradiance decreased as distance increased except for Valo for all power modes up to 3 mm. The same effect was observed with Bluephase up to 5 mm. Conclusions: Within the limitations of this study, results determined that the energy delivered by different LCUs may reach levels that are not suitable for curing of resin-based composites. Manufacture’s instructions should be observed specially with high power LCUs where irradiance generate heat and burn of pulpal and soft tissues.