From milling to printing: evaluating the applicability of zirconia in restorative dentistry

PURPOSE. This study compared the mechanical and optical properties of 3D-printed and milled zirconia, and evaluate the marginal and internal adaptation of crowns fabricated with 3Y-TZP and veneers fabricated with 5Y-TZP. MATERIALS AND METHODS. Ninety-two disc specimens and thirty-six monolithic restorations (crowns and laminate veneers) were fabricated using standardized CAD-CAM workflows. Biaxial flexural strength was measured, and optical properties were evaluated using the translucency parameter (TP), total transmittance (TT), and haze. Marginal and internal adaptations were assessed using a silicone replica technique. RESULTS. Printed 3Y-TZP showed flexural strength comparable to milled zirconia (1211.4 ± 114.3 MPa vs. 1120.3 ± 93.3 MPa; P = .067), and no significant differences were observed between fabrication methods for 5Y-TZP (P = .442). TP values were significantly higher in milled zirconia for both 3Y-TZP and 5Y-TZP (all P < .001). For 5Y-TZP specimens only, TT was higher in the milled group (P < .001), whereas haze values did not differ between fabrication methods. All restorations demonstrated marginal gaps within clinically acceptable limits (< 120 ㎛). Printed crowns exhibited significantly smaller occlusal internal gaps (P = .029), and printed laminate veneers showed favorable marginal adaptation at multiple sites. CONCLUSION. 3D-printed zirconia showed flexural strength comparable to milled zirconia and demonstrated favorable adaptation in selected regions, although optical properties were lower.