Evaluation of Knoop Microhardness of Nanoparticle Resins According to the Light Curing Apparatus.

Resumo

Since the introduction of composite resins, depth of polymerization has been a concern among researchers since it can adversely affect the materials´ physical and mechanical properties if insufficient. This study assessed the degree of Knoop microhardness of three nanoparticle resins polymerized with four types of sources of activation. Sixty test specimens were prepared using standard curing time of 20 seconds as per manufacturers´ recommendations. Those specimens were divided into four groups and further divided into subgroups according to type and type of cured resin, respectively. After microhardness test and analysis of variance (ANOVA with a significance level of 5.0%), results showed that the highest hardness values were observed on the top for all groups. For Groups 2, 3 and 4 in the top area and 1, 2 and 4 in the base resins, there were significant hardness differences whereas in Group 1 (base) and 2 (top) the Z350 resin showed significantly higher hardness values than the others. It was also shown that LED appliances are as effective as those using halogen light.