Post-cure Heat Treatments Influence the Mechanical and Optical Properties of Acrylic and Bis-acryl Composite Resins
To evaluate the influence of post-cure heat treatments (PCHT) on Knoop microhardness (KHN) and color change of bis-acryl composite resin (Protemp 4 - 3M ESPE, USA and PrimmaArt - FGM, Brazil) and chemically activated acrylic resins (Dencôr – Clássico, Brazil, and Duralay – Cotia, Brazil). Specimens (12×1 mm) were prepared for each material (n=10/group). Thirty minutes after curing, the specimens were subjected to PCHT for 10 minutes at 70°, 100°, or 130°C. The control group was kept at room temperature (24°C) for the same amount of time. KHN was analyzed 24 hours after PCHT (n=10). Following Commission Internationale de l’Éclairage (CIE) Delta E 2000 (CIEDE2000 [ΔE00]), color measurements were obtained at three time points: 1. after polymerization; 2. after PCHT; and 3. after 30 days of storage in water, coffee, or red wine. Data for each material were analyzed by one-way analysis of variance (ANOVA) (p<0.05). The PCHT at 130°C produced the highest KHN values. Except for the 70°C groups from Dencôr and Protemp, all PCHTs increased the initial color values (p>0.05). In general, chemically activated acrylic resins showed an increase in color stability when subjected to PCHT (p>0.05). For bis-acryl composite resin, PCHT did not influence color stability (p<0.05). Overall, the results showed that PCHT increased the tested materials’ color changes and Knoop microhardness. However, except for PCHT at 130°C in Duralay, the color changes remained within acceptable values. The PCHT treatment resulted in better color stability for most of the composite resins studied.SUMMARY
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Flowchart of the experimental design.
Mean and standard deviation in Knoop microhardness of the resin composites after post-cure heat treatment. p-values are presented when a significant difference is observed between groups by one-way ANOVA followed by Tukey tests. (α=0.05, n=10/group.)
Mean and standard deviation of color changes ΔE00 of the resin composites after post-cure heat treatment. p-values are presented when a significant difference is observed between groups by one-way ANOVA followed by Tukey tests. (α=0.05, n=10/group).
Mean and standard deviation of color changes (ΔE00) of the thermally treated resin composites after immersion in water, coffee, and wine. p-values are presented when a significant difference is observed between groups by one-way ANOVA followed by Tukey tests. (α=0.05, n=10/group).
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