| Objective: The aim of this study was to examine the effects of accelerated aging on shear strength, micro-tensile strength and microstucture of different fiber-reinforced resin posts. Methods: Five brands of fiber posts were selected for this study (Macro-lock? Post/ML, Luxa Post/LP, Para Post Taper Lux/PA, FRC Postec Plus/VI, Nordin Glassix + plus /NO). 20 specimens of each brands of posts were divided randomly into 2 groups. One for aging test, the other one not (in each group 10 specimens were used for shear strength test, 10 for tensile strength test). The group of aging was accelerated aged for 200 h, and the other one was stored in opaque box. Then the specimens of these groups were used for tests in shear strength and tensile strength, and processed for ESEM analysis to assess their microstructural characteristics, namely fiber diameter, fiber density, fiber/matrix radio. FTIR was used to assess the inner chemical bonds. The statistical analysis of shear strength and tensile strength befor and after aging was carried out with two-way ANOVA for the 5 different brands of posts. The correlation between mechanical properties and microstuctural variances of the posts was measured by calculating Peason's correlation coefficients (α=0.05). Results: The posts of different brands showed statistically significant differences in shear strength and tensile strength (P<0.05). The shear strength showed a significant correlation to fiber diameter (r=0.740, P=0.000), and to fiber density (r=-0.822, P=0.000); the tensile strengths showed a significant correlation to fiber diameter (r=-0.776, P=0.000), and to fiber density (r=-0.860,P=0.000). The shear strength and tensile strength of the samples befor and after aging were significantly different (P<0.05). The shear strength declined after aging, of which the reduction of NO was the lowest (4.73±12.02%) and VI the highest (30.53±6.96%). The tensile strength of ML/PA inclined, LP/VI declined after aging, of which the reduction of VI was the highest (50.29±2.53%). ESEM observations showed that most of the matrix separated from the surface of fiber, and FTIR observations showed that the absorbance of ester increased after aging. Conclusion: The shear strength and tensile strength of different brands were significantly different. Both the shear strength and tensile strength were influenced by fiber diameter and density. Physical aging and oxidation took place in matrix, which influence the interfacial bond and mechanical properties after aging. The shear strength declined after aging, and the aging resistance of NO was the strongest, VI the weakest. The tensile strength changed variously and the aging resistance of VI was the weakest. |
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