Fit and fracture resistance of 3D-printed single crowns made from highly translucent zirconia

To compare the fit and fracture resistance of 3D-printed and milled single crowns made from highly translucent zirconia (5Y-PSZ) and to evaluate the influence of two debinding/presintering protocols.

Single crowns were fabricated either by 3D printing or milling. For fit evaluation (n = 10/group), crowns with a wall thickness of 0.7 mm were cemented, sectioned, and analyzed microscopically at predefined locations. For fracture resistance testing (n = 10/group), crowns with wall thicknesses of 0.7 mm and 1.5 mm were cemented to fiber-reinforced composite abutments. Conservative (cons DB) and a fast (fast DB) debinding and presintering protocols were applied to the 3D-printed groups.

3D-printed crowns showed significantly larger circular (cons DB: 124.8 µm; fast DB: 125.0 µm vs. 77.4 µm) cement gaps than milled crowns (p < 0.001), whereas their occlusal gaps were significantly smaller (cons DB: 96.8 µm; fast DB: 95.6 µm vs. 157.0 µm; p = 0.030). Mean marginal cement gaps in vertical and tangential directions were below 80 µm for all groups. The debinding protocol did not significantly affect fit. Fracture resistance was significantly influenced by manufacturing technique: at 0.7 mm wall thickness, 3D-printed crowns showed the highest values (cons DB: 1022N; fast DB: 1286N vs. 664N; p < 0.050), whereas milled crowns showed superior fracture resistance at 1.5 mm wall thickness (cons DB: 2384N; fast DB: 1904N vs. 3318N; p < 0.050). The debinding protocol had no significant effect on fracture resistance, although lower values and greater variability were observed following the fast DB protocol, particularly for 1.5 mm crowns.

3D-printed 5Y-PSZ single crowns demonstrated clinically promising fit and fracture resistance overall, with performance broadly comparable to milled crowns. However, rapid debinding may compromise the mechanical reliability of thicker printed restorations.