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vol.9 issue3Surface characterization of alumina reinforced with niobium carbide obtained by polymer precursorComparison of the corrosion resistance of DIN W. Nr. 1.4970 (15%Cr-15%Ni-1.2%Mo-Ti) and ASTM F-138 (17%Cr-13%Ni-2.5%Mo) austenitic stainless steels for biomedical applications author indexsubject indexarticles search
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Materials Research

Print version ISSN 1516-1439On-line version ISSN 1980-5373


CORRER, Américo Bortolazzo et al. Effect of exposure time vs. irradiance on knoop hardness of dental composites. Mat. Res. [online]. 2006, vol.9, n.3, pp.275-280. ISSN 1516-1439.

A comparison was made of the hardness of Z250 and Esthet-X composites light cured with different light sources. Cavities (3 mm diameter x 6 mm deep) were prepared in 240 bovine incisors. The composite was bulk inserted and light-cured using halogen light, LED or xenon plasma arc (PAC) with different irradiances and exposure times, maintaining the same energy density. The specimens were stored in an incubator at 37 °C for 24 hours prior to sectioning for hardness measurements. Three measurements were taken at each depth: surface, 1, 2, 3, 4 and 5 mm. The data were analyzed by ANOVA and Tukey's test (p < 0.05). No statistically significant differences were found for LED up to 2 mm, for PAC up to 3 mm, and for halogen light up to 5 mm. Photoactivation with intermediate power density and exposure time resulted in the highest Knoop hardness values.

Keywords : composite resin; energy density; Knoop hardness; light curing.

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