Effectiveness of polymerization in composite restoratives claiming bulk placement: impact of cavity depth and exposure time.

The impact of variation of cavity depth and light-source exposure time upon the effectiveness of polymerization of two "bulk placement" composite restoratives was assessed indirectly using hardness testing. The current investigation used a digital microhardness tester to evaluate hardness gradient between top and bottom surfaces of composite specimens of various depths after different light-exposure times. The results showed that the effectiveness of polymerization decreased significantly with increased cavity depth regardless of exposure time. Increased exposure time increased the extent of polymerization at cavity depths of 3 to 4 mm. Increments of the composites evaluated should be no greater than 2 mm to provide uniform and maximum polymerization.