IN VITRO ASSESSMENT OF MARGINAL AND INTERNAL GAP OF MONOLITHIC ZIRCONIA CROWNS FABRICATED BY MILLING AND 3D PRINTING TECHNIQUES.

Aim of the study: this invitro investigation aimed to assess how accurate monolithic zirconia restoration constructed by milling (subtractive) and printing (additive) techniques. Materials and methods: twenty zirconium single unit restorations were constructed by subtractive (group 1) and additive technologies (group 2). The accuracy at the margin was evaluated at twelve measurement spots utilizing the vertical marginal gap method (VMGT). With regards the internal discrepancy, the replica approach was conducted, and it was measured in four areas: marginal, axial, axial-occlusal, and mid-occlusal areas. It was reported that the data followed a normal distribution, and an independent t-test was used to analyze the results. Results: Using VMGT, group 1’s mean marginal gap values were (56.9 ± 7.77 μm), which was significantly lower than group 2’s (84 ± 13.5) μm (p < 0.001). Additionally, group 1’s marginal gap (61.75 ± 13.45 μm) showed substantially lower values with the SRT than group 2’s (82.65 ±12.53 μm). With the exception of the axial gap, the adaptation of the internal surface revealed a substantial disparity between both techniques. Conclusions: Despite zirconia milled crowns performed better, clinically acceptable outcomes with regards accuracy of fit, can be achieved by the additive techniques.