Effectiveness of Class Two Polymerization With QTH and LED Lights

Objective: The aim of this in vitro study was to compare cure effectiveness of class two (RBC) restorations polymerized with light emitting diodes (LED) and quartz tungsten halogen (QTH) light curing systems. Methods: 30 class two (vertical slot type) cavities with 5 mm depth were prepared on the mesial and distal surfaces of 15 extracted caries free upper and lower molars. The cavities were divided randomly into 3 groups (10 cavities each) and restored incrementally with P60/ Single Bond 2 (3MESPE, USA), and polymerized in continuous standard mode with: 1- (QTH) light curing system (Optiluxe 501 LCU Kerr, USA), 2- (LED) light curing system (MiniLED LCU Acteon, France, and Elipar Freelight2 LCU 3MESPE, USA). After polymerization the teeth were sectioned mesio-distally and polished at the sectioned surfaces before submitting to microhardness tests. Vickers Microhardness Tests (load= 100 g; dwell time= 30 seconds) were performed at 1,2,3,4,5 mm depths on the sectioned surfaces of the mesial and distal restorations starting from the occlusal surface toward the gingival surface. Results: Two-way ANOVA detected significant differences between light curing units in hardness values. Despite the depth of the cavity Freelight2 showed superior hardness values, (p<0.05), indicating better degree of conversion for the composite restorations. Vickers Hardness Number (VHN) decreased when the depth of the cavity was increased regardless of the light curing units. Hardness ratio (HR) between (VHN) at 5 mm depth and (VHN) at 1 mm depth for MiniLED (82.91%), and Freelight2 (76.84%) were higher than Optiluxe 501 (66.13%), (p<0.05), indicating good focusing effect of LED light curing system. Conclusions:1-Freelight2 gave the highest hardness value with different cavities depths. 2- The hardness values decreased when the cavity depth was increased . 3- LED light curing system was more effective than QTH light curing system in polymerizing class two (RBC) restorations.