Effect of oral environment on new fiber-reinforced composites system

Abstract

PURPOSE: Fiber-reinforced composite (FRC) consists of matrix that is reinforced with thin fibers, which have high tensile strength and flexural modulus (Zhang and Matinlinna, Silicon 4 (2012) 73). The bis-GMA-MMA combination is widely used as resin matrix, whereas bis-GMA is reported to be the most cytotoxic monomer among dental resin composite monomers (Moharamzadeh et al., Material 2 (2009) 514). Resin matrix 1,6-hexanediol dimethacrylate (HDMA) has similar reactive groups than bis-GMA, and is not listed among carcinogens (Vallittu and Sevelius, J Prosthet Dent 84 (2000) 13). The purpose of this study was to investigate the water sorption of a new resin matrix system of FRC based on HDMA. METHODS AND MATERIALS: Materials used were: E-glass fiber bundles (Stick Tech, Finland), HDMA (Esstech, USA), bis-GMA (Sigma–Aldrich, USA), MMA (ProSciTech, Australia), CQ (Esstech, USA) and CEMA (Esstech, USA). Fifteen specimens (2mm×2mm×25mm) were prepared and divided into 3 groups. Composition of group 1: 78.4%HDMA +19.6%MMA+ 1.0%CQ + 1.0%CEMA; group 2: 49.0%HDMA +49.0%MMA+ 1.0%CQ + 1.0%CEMA; and group 3: 78.4%bis-GMA +19.6%MMA+ 1.0%CQ + 1.0%CEMA. Specimens with two fiber rovings of 25mm long were placed in a mould and monomers were added and light-cured with halogen light-curing unit on both sides for 3×40 s. Specimens were immersed in 15 ml distilled water of 37 ◦C for 21 days. The difference in weights, before and after immersion were recorded. Data obtained were analyzed by one-way ANOVA and LSD. RESULTS: As for the difference in weights (before and after immersion), group 1 showed the lowest average (0.004%), followed by group 3 (0.003%) and group 2 (0.01%). Statistical analysis (ANOVA) proved a significant difference among the three groups (p < 0.05). Result of LSD showed there was a significant difference between group 1 and group 2 (p < 0.05), but no significant difference between group 1 and group 3 (p > 0.05). CONCLUSION: It can be concluded that FRC based on HDMA matrix system (group-1) is comparable to bis-GMA (group-3) on its water sorption.