Abstract
The aim of this study was to investigate the influence of accelerated artificial aging (AAA) on the microstructure and mechanical properties of the Filtek Z250, Filtek Supreme, 4 Seasons, Herculite, P60, Tetric Ceram, Charisma and Filtek Z100. composite resins. The composites were characterized by Fourier-transform Infrared spectroscopy (FTIR) and thermal analyses (Differential Scanning Calorimetry - DSC and Thermogravimetry - TG). The microstructure of the materials was examined by scanning electron microscopy. Surface hardness and compressive strength data of the resins were recorded and the mean values were analyzed statistically by ANOVA and Tukey's test (α=0.05). The results showed significant differences among the commercial brands for surface hardness (F=86.74, p<0.0001) and compressive strength (F=40.31, p<0.0001), but AAA did not affect the properties (surface hardness: F=0.39, p=0.53; compressive strength: F=2.82, p=0.09) of any of the composite resins. FTIR, DSC and TG analyses showed that resin polymerization was complete, and there were no differences between the spectra and thermal curve profiles of the materials obtained before and after AAA. TG confirmed the absence of volatile compounds and evidenced good thermal stability up to 200 °C, and similar amounts of residues were found in all resins evaluated before and after AAA. The AAA treatment did not significantly affect resin surface. Therefore, regardless of the resin brand, AAA did not influence the microstructure or the mechanical properties.
Highlights
In order to minimize the problems related to polymer degradation, it is essential to know the surface and structural behavior of polymeric materials
Numerous studies reported that artificial aging leads to a significant decrease in the mechanical properties of dental materials [15,16], but in this study the aging process did not cause significant changes in the properties of the aged resins and the study hypothesis was rejected
The mechanical analyses were selected because compressive strengths are transmitted to the supporting tissues of the oral cavity and to dental restorative materials
Summary
In order to minimize the problems related to polymer degradation, it is essential to know the surface and structural behavior of polymeric materials. Mechanical properties are relevant to the durability of composite resins [3,4] and are related to the filling ratio, which includes such factors as the shape, type, number and distribution of charged particles [5]. These properties depend on the degree of polymerization [6]. Morphological analysis conducted by scanning electron microscopy (SEM) provides insight into particle size and shape as well as surface and bulk morphology [5]
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