Comparison and Evaluation of Marginal and Internal Gaps in Zirconia Crowns Fabricated Using Additive Manufacturing with Top-Down Approach

Zirconia crowns prepared by the milling method are successfully used for single anterior and posterior restorations. Incorrect marginal fit of zirconia prostheses can lead to cavities between the prosthesis and natural teeth, resulting in periodontal disease. In this study, the marginal fit of zirconia crowns manufactured by milling machine and top-down additive manufacturing was compared and analyzed. Existing milling methods show excellent precision, but the fit result might vary or the precision would be lowered depending on the degree of use of the burr. In addition, different results could be shown depending on the limitations of the milling axis of CAD/CAM equipment or the compensation value of the milling bur. The additive manufacturing method could solve all of these limitations because there is no consumption of cutting tools and complex shapes are processed with a constant layer thickness. Furthermore, we confirmed that the top-down approach in 3D printing could enhance precision in ceramic 3D printing.