Weibull-Based Reliability of Full-Arch Zirconia Prostheses in a Mandibular All-on-4 Model: Monolithic Versus Titanium-Bar–Supported Designs

Background/Objectives: Full-arch zirconia prostheses for mandibular All-on-4 rehabilitations are provided as screw-retained monolithic zirconia or as a zirconia suprastructure luted to a CAD/CAM titanium bar. Because zirconia is a brittle, flaw-sensitive ceramic, design assessment should incorporate stress-field–weighted fracture risk. This in-silico study compared zirconia tensile stress and Weibull-based reliability between monolithic (Zr-Mono) and titanium-bar–supported zirconia (Zr-TiBar) designs. Methods: A standardized 3D edentulous mandibular All-on-4 model (four 4.3×11.5-mm implants; posterior implants tilted 30°) with multi-unit abutments and Ti-bases was analyzed using linear static finite element analysis. Posterior unilateral loads were applied to the first molar (300 N axial; 300 N at 45° oblique). Outcomes were maximum principal tensile stress in zirconia (S1max), total prosthesis deformation, and Weibull-predicted probability of zirconia fracture (m = 7.41; σ0 = 576.5 MPa) derived from the tensile S1 field. Results: Under axial loading, S1max was similar (Zr-Mono 277.09 MPa; Zr-TiBar 277.13 MPa). Under oblique loading, S1max was lower for Zr-TiBar (226.94 MPa) than for Zr-Mono (233.82 MPa). Deformation was <0.07 mm and lower for Zr-TiBar (0.0607 mm axial; 0.0589 mm oblique) than for Zr-Mono (0.0635 mm axial; 0.0660 mm oblique). The Weibull-predicted probability of fracture was very low: axial 1.309×10⁻⁶ (Zr-Mono) vs 1.473×10⁻⁶ (Zr-TiBar); oblique 1.589×10⁻⁷ vs 1.790×10⁻⁷. Conclusions: Both designs showed comparably low Weibull-predicted fracture probability under single 300 N posterior loads. Titanium-bar support reduced deformation and modestly reduced peak tensile stress under oblique loading, but did not reduce the predicted fracture probability relative to monolithic zirconia.