Abstract
The purpose of this study was to assess the effects of post-polymerization heat on the flexural strength of direct composites. Direct composite specimens (n=10), measuring 25×2×2 mm (Z-250 and P-60), were polymerized by 3 methods: (1) light-polymerized for 40 seconds, (2) (1) + post-polymerization in an oven at 120ºC for 20 minutes, and (3) (1) post-polymerization in an autoclave at 120ºC for 20 minutes. Specimens (n=10) of the indirect composite Artglass (control group) were polymerized in a UniXS oven. Specimens were stored in distilled water for 24 hours at 37ºC and then submitted to a flexural 3-point bending test with a universal testing machine. Flexural strength (MPa) data were analyzed by one-way ANOVA and Tukey´s multiple comparison test (α=.05). Results showed that (1) additional heat polymerization in an oven provided significantly (p<.05) higher flexural strengths (Z250: 158.85 MPa and P60: 147.10 MPa) than that of the Artglass resin (121.52 MPa); (2) with additional heat polymerization in an autoclave, these direct resins presented mean flexural strengths (Z250: 134.54 MPa and P60: 130.18 MPa) similar to that of Artglass (P>.05); (3) groups that were only light-polymerized (Z250: 124.75 MPa and P60: 128.96 MPa) were similar to Artglass (P>.05). When composites were only light-polymerized, they showed a flexural strength behavior similar to that of the indirect composite Artglass. The post-polymerization heat do not enhanced the resistance of the Filtek P60, but increased the strength of the Filtek Z250 when additional heat polymerization in a oven
Highlights
During the last decade, the development of new esthetic restorative materials and more efficient dentin/ enamel bonding systems have provided replacements for metal restorations
Filtek Z250 and Filtek P60 resins, when post-polymerized in an oven, demonstrated similar mean flexural strengths; these strengths were significantly (p
For Filtek Z250, post-polymerization in an autoclave resulted in resistance significance lower than that of the group post-polymerized in an oven
Summary
The development of new esthetic restorative materials and more efficient dentin/ enamel bonding systems have provided replacements for metal restorations Another factor resulting from the increased use of posterior composite restorations is the esthetic advantages of nonmetal restorations[5]. Commercially called “ceromers”, were developed in 1995 to overcome some of the undesirable properties of porcelain, such as the difficulty of intraoral repair and occlusal adjustment, and the possibility of wear to opposing teeth[6]. These materials, require the use of special equipment for processing, increasing the cost of the restoration. Indirect composites present a chemical composition similar to those of the light-polymerized direct composites; yet, the polymerization processes utilized are often more efficient[6]
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