The study of fractural behavior of repaired composite

Abstract

Objectives: This study evaluated microtensile bond strength (μ TBS) and short-rod fracture toughness to explain fractural behavior of repaired composite restorations according to different surface treatments. Materials and Methods: Thirty composite blocks for μ TBS test and sixty short-rod specimens for fracture toughness test were fabricated and were allocated to 3 groups according to the combination of surface treatment (none-treated, sand blasting, bur roughening). Each group was repaired immediately and 2 weeks later. Twenty-four hours later from repair, μ TBS and fracture toughness test were conducted. Mean values analyzed with two-way ANOVA / Tukey' s B test (α= 0.05) and correlation analysis was done between μ TBS and fracture toughness. FE-SEM was employed on fractured surface to examine the crack propagation. Results: The fresh composite resin showed higher μ TBS than the aged composite resin (p < 0.001). Mechanically treated groups showed higher bond strength than non-mechanically treated groups except none-treated fresh group in μ TBS (p < 0.05). The fracture toughness value of mechanically treated surface was higher than that of non-mechanically treated surface (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. Specimens having high KIC showed toughening mechanism including crack deviation, microcracks and crack bridging in FE-SEM. Conclusions: Surface treatment by mechanical interlock is more important for effective composite repair, and the fracture toughness test could be used as an appropriate tool to examine the fractural behavior of the repaired composite with microtensile bond strength.