COMPOSITE DEPTH OF CURE USING FOUR POLYMERIZATION TECHNIQUES

The light-curing technique is relevant to reduce the degree of polymerization shrinkage, improving clinical and esthetic success of composite resin restorations. Objective: To evaluate in vitro the effect of four light-curing techniques on depth of cure of a composite resin. Material and Methods: Ten specimens of a composite resin were made in cylindrical cavities prepared in PVC plates (3.0 x 7.0 mm) for each light-curing technique. Four photoactivation methods were investigated: stepped, ramped, pulse-delay and traditional. Specimens were longitudinally sectioned and polished for microhardness measurements (kg/mm(2)), which were made at 0.1, 1.0, 2.0 and 4.0 mm from the irradiated surface. Data were subjected to ANOVA and Tukey's test. Results: The effect of factors studied (curing method and distance from the surface) and the interaction of these factors was statistically significant (p<0.05). The traditional method of cure provided higher microhardness values (69.6 +/- 2.5) than the stepped (63.5 +/- 3.1) and pulsed (63.9 +/- 3.2) methods at all depths evaluated, but it did not differ from the ramped method (66.7 +/- 4.4) at 0.1 and 1.0 mm of depth. Conclusion: All techniques employed provided satisfactory cure of the composite resin up to the depth of 2.0 mm from the irradiated surface.