Investigation of some mechanical properties of zirconia samples produced in 3-dimensional printers in a digital environment and the strength of connection with veneer ceramics

In this study, some mechanical properties of ceramic samples fabricated by additive manufacturing (three-dimensional lithography) and subtractive manufacturing (CAD-CAM) were evaluated in-vitro. Three-dimensional lithographic production techniques and CAD-CAM systems were used to create the zirconia samples used in the study. In evaluating mechanical properties; the bending strength test, indentation fracture toughness test, and hardness test were used. Moreover, the shear test was applied to test the connection with the superstructure ceramics. In addition, EDS and particle analysis tests were applied to the samples. EDS and particle analysis were performed on the FE-SEM device before the tests were performed. The analysis of the fracture surfaces of the broken parts in the flexural strength test was evaluated both in the FE-SEM device and in the optical microscope. After the shear test, the surfaces of the samples were examined under an optical microscope to determine the failure types. In line with the results obtained, the highest flexural strength was obtained as 1173±160.9 MPa in zirconia samples produced by the lithography technique. The lowest bending strength is 818.5±265.8 MPa in the zirconia group produced by subtractive methods. A statistically significant difference was observed between the bending strengths of both groups (P<0001). When the zirconia samples prepared by subtractive and additive methods were compared in terms of surface hardness and fracture toughness, no statistically significant difference was found (P>0.05). As a result of the shear bond test, no statistically significant difference was observed between zirconia groups in both production methods (P=0.9862). Considering the strength of the zirconia produced by the additive manufacturing method (lithography) in line with the findings obtained, it is sufficient for dental use. When the bond strength values with the superstructure ceramic are evaluated, the values obtained in the samples prepared by the additive manufacturing method are as good as the subtractive manufacturing (CAD-CAM).