FRACTURE TOUGHNESS OF DENTAL CAD/CAM RESIN-MATRIX CERAMICS EXPOSED TO AN ACIDIC ENVIRONMENT

This study aimed to assess the effects of an acidic environment on the fracture toughness of dental CAD/CAM resin-matrix ceramics. One hundred rectangular specimens (18 x 4 x 3 mm(3)) were obtained from four CAD/CAM resin-matrix ceramic blocks - Crystal Ultra (CU), Vita Enamic (VE), Lava Ultimate (LU), Cerasmart (CS) - and a Vitablocs Mark II (VMII) glass-matrix ceramic. Specimens from each material group were aged either in artificial saliva or cola for one week (n = 10). The fracture toughness (KIc) was evaluated using the single-edge v-notch beam (SEVNB) method in a three-point bending set-up. The fractured specimen surfaces were analysed using a scanning electron microscope (SEM). The data were analysed using a two-way ANOVA with the post hoc Bonferroni and paired t-test (p < 0.05). The two-way ANOVA suggested that the materials significantly affected the KIc (p < 0.001), while the ageing environment had no significant effect on the KIc (p = 0.285). The highest KIc was observed in the CU group aged in cola (1.53 +/- 0.12 MPa center dot m(1/2)), while the lowest mean KIc was observed in the CS group aged in saliva (1.17 +/- 0.08 MPa center dot m(1/2)). All the tested CAD/ CAM resin-matrix ceramics showed improved fracture toughness in an acidic environment compared to the artificial saliva. However, the fracture toughness of the CS and CU groups significantly improved in an acidic environment compared to the artificial saliva, demonstrating the ability of these materials to resist an erosive acidic environment.