Consequences of the Additional Polymerization on Knoop Microhardness of Direct Composite Resin

Abstract

ABSTRACT:The following hypothesis was tested: direct composites additional polymerization improve the surface microhardness of direct composite resin Filtek Z250 (3M ESPE). We prepared 25 specimens (2x4 mm) with a stainless steel mold. Resin specimens were randomly assigned into 5 groups (n=5/per group): G1 -resin Filtek Z250 photoactivated 60 s; G2 -resin Filtek Z250 photoactivated 60 s + autoclave cycle to 134°C for 7 min at a pressure of 2.5 kg/cm3; G3 -resin Filtek Z250 photoactivated 60 s + oven at 125ºC for 7 min; G4 -resin Filtek Z250 photoactivated 60 s + microwave for 3 min to the power of 450W; G5 -indirect resin Resilab photoactivated 60 s + supplementary furnace LUX GDS 4 min. The specimens were fabricated by a metal matrix, filled with resin in two increments and each increment polymerized according to their group. For polymerization of the last layer, we used a glass plate on a polyester strip. Then the specimens were evaluated for surface microhardness Knoop. Additional polymerization media resulted in significant differences among the groups (p<0.05) (One-way ANOVA and Dunnett test, p=0.05). The mean surface hardness Knoop (KHM) were as follows: G1: 51.71±1.73b; G2: 62.37±1.71a; G3: 50.61±1.30b; G4: 52.65±1.125b; G5: 60.15±2.02a; Conclude that the additional polymerization in autoclave increased the surface microhardness Knoop of composite resin evaluated. Hypothesis was partially confirmed.

Comparative Analysis of the Influence of 10 and 5% Hydrofluoric Acid Etching on the Average Roughness of Lithium Disilicate Used in Dental Prostheses

“…These are composed of two crystalline phases, one consisting of elongated crystals of lithium disilicate and the other by lithium orthophosphate, and a vitreous phase, which forms a matrix involving the crystalline phases. It is a brittle material with high elasticity modulus and flexural strength around 400MPa [1].…”