The Effect of Different Light Curing Modes on Microleakage of Composite Restorations

Abstract

Statement of problem: One of the major problems in composite restorations is polymerization shrinkage leading to microleakage, hypersensitivity, recurrent carries, pulpal inflammation, and later pulp necrosis. To overcome these problems, different photo-activation methods have been employed to prolong the plastic phase during polymerization.Purpose: To investigate the mircoleakage in 3 groups of Pulse, Ramp and conventional LED photo-polymerization methods in class V composite restorations.Materials and Method: Twenty one freshly extracted human premolars were categorized in 3 groups of 7 each. Slot shaped class V cavities (4 ´ 2 ´ 2 mm) were prepared on both buccal and lingual surfaces of the teeth, with occlusal margins on the enamel and gingival margins 1mm below the CEJ. The cavities were restored with single bond and Z100 composite (3M ESPE,USA) and cured in group A with Ramp, group B with Pulse mode, and group C with Conventional mode using Apoza LED Turbo light Curing unit. After one day storage in 37°C water and thermo cycling for 1000 cycles, the teeth were sealed with nail varnish 1 mm short of margins, immersed in AgNo3 50% W and then developed in solution. The specimens were cut and evaluated by Stereo microscope at 40 x magnification. The results were statistically analyzed by kruskal- Wallis test.Results: None of the specimens revealed microleakage at the occlusal margins but 69.2% of the specimens in Ramp group, 76.9% in the Pulse group and 61.5% in the conventional group showed score 1 gingival microleakage. Also, 30.8% in the Ramp and Conventional and 23.1% in the Pulse group showed score 2 gingival microleakage. Analysis of the data among the 3 groups revealed no statistically significant differences. ( p = 0.640)Conclusion: Based on the limitations of this study:1- All of LED photoactivation modes using Apoza LED turbo unit prevent microleakage in the enamel margins.2- None of the photoactivation modes can prevent microleakage in the gingival margins completely.3- For Z100 (microhybrid composite), all of the 3 employed methods were equally effective in microleakage reductionKey words: Microleakage, Photo activation mode, Class V cavities, Composite