Abstract
This in vitro comparative study evaluated the dimensional stability and mechanical performance of monolithic zirconia crowns fabricated using slurry-based additive manufacturing (AM) versus conventional computer-aided design and computer-aided manufacturing (CAD/CAM) subtractive milling (SM). A standardized resin master die of a prepared upper first molar was digitized to design forty monolithic 3Y-TZP zirconia crowns (n = 20 per group). Group AM crowns were fabricated via digital light processing stereolithography, while Group SM crowns were subtractive-milled from presintered zirconia blocks. Marginal and internal adaptation were quantified using high-resolution micro-computed tomography (micro-CT) and the silicone replica technique. Following thermal aging (10,000 cycles between 5°C and 55°C), all specimens were subjected to axial compressive loading until fracture using a universal testing machine. Mean marginal discrepancies were 44.2 ± 5.1 µm for AM and 38.4 ± 4.2 µm for SM, both well within the clinical threshold of 120 µm. AM exhibited significantly lower axial gap variability, indicating uniform internal relief. Fracture resistance testing demonstrated mean failure loads of 2145 ± 182 N for AM and 2280 ± 195 N for SM, showing no statistically significant difference (p = 0.082). Scanning electron microscopy revealed similar catastrophic fracture patterns without evidence of interlayer delamination in AM crowns. Slurry-based additive manufacturing produces monolithic zirconia restorations with clinically acceptable dimensional accuracy and robust mechanical performance comparable to subtractive milling.
