Lithography-based Ceramic Manufacturing (LCM) versus Milled Zirconia Blocks under uniaxial compressive loading: An in vitro comparative study

Aim: This in vitro study aimed to compare the mechanical performance of 3D printed versus milled zirconia blocks, when subjected to uniaxial compression load, and to investigate the microstructural characteristics of the 3D printed samples, before and after the application of the load. Methods: Twenty zirconia blocks (5 x 5 x 5mm(3)) were prepared: 10 (tests) were 3D printed with a Lithography based Ceramic Manufacturing (LCM) printer (Cerafab S65 (R), Lithoz, Vienna, Austria), and 10 (controls) were milled with a 5-axis milling machine (DWX-52D (R), DGShape, a Roland Company, Hamamatsu, Japan). Compression tests were carried out on all samples, using a load cell of 30 kN and crosshead speed of 0.5 mm/min, in according to the ASTM C1424-15. The elastic modulus of the material was calculated from stress/strain curve by taking compressive stress values between 50 MPa and 100 MPa. Compression data obtained were plotted as stress-strain curves. Finally, the 3D printed test samples were also observed by VEGA3 Tescan scanning electron microscope (SEM) to detect the presence of eventual defects on surface before and after compression. A statistical analysis was performed to compare the elastic modulus and the deformation in compression at maximum load of the test samples that did not break and the control samples. Results: Under mechanical compression, four of the test samples reached failure, whereas all the control samples did not reach failure at the limit of the load cell. However, the 3D printed samples that did not break revealed interesting properties, such as a better modulus of elasticity (p = 0.15) and a lower tendency to deformation under compression (p<0.001), when compared to the milled ones. Conclusions: Within the limits of this study (experimental setting, in vitro design, only one type of force applied) milled zirconia blocks were found more resistant to compression forces than 3D printed ones.