Mohammed Q Alqahtani.
The effect of visible light polymerization techniques on microleakage of Hybrid and Microfilled resin composites.
J Pak Dent Assoc Nov ;14(3):158-62.

OBJECTIVE: To evaluate the effect of 2-step technique of visible light polymerization on the microleakage of hybrid and microfilled resin composite materials, and to compare the results with those of the same materials polymerized with the standard method of visible light polymerization. MATERIALS AND METHODS: 48 teeth were used and divided to 4 groups of 12 specimens, one control group and one test group for each resin. Class V cavities were prepared on the facial surfaces of all teeth. After applying the bonding agent, the resin composite was applied in two increments. In the control groups, the resin samples were polymerized for 60 seconds using the standard technique at light intensity of 700 mW/cm2. In the experimental groups, the resin samples were polymerized using the 2-step technique at light intensity of 150 mW/cm^2 for the first 10 seconds and 700 mW/cm2 for the remaining 50 seconds. After thermocycling, each tooth was sectioned and "Ca tracer was used to test microleakage with autoradiographs. RESULTS AND CONCLUSION: Based on the findings of this study, no significant differences were seen at the enamel margin for both resin composite materials. For the microfilled resin, the 2-step technique reduced significantly the microleakage at the dentin margin. For the hybrid resin, the 2-step technique had no significant effect on reducing of the microleakage at the dentin margin.

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