Mechanical stability of posterior implant‐supported monolithic zirconia cantilever on titanium‐base abutments. An in vitro study

Purpose Investigate survival and technical complications of two‐unit posterior implant‐supported cantilever made of monolithic zirconia on titanium‐base abutments (Zr‐TiB) vs. porcelain‐fused‐to‐metal on castable gold abutments (PFM‐GA) using two different implant connections, internal butt‐joint (IBJ) and internal conical (IC). Materials and Methods Forty‐eight implants (4.3 mm diameter) were divided into four groups ( n = 12) to support 2‐unit mandibular premolar cantilevers with two different materials (Zr‐TiB vs. PFM‐GA) and two connection types (IBJ vs. IC). Tested groups were as follows: (1) IBJ/Zr‐TiB; (2) IBJ/PFM‐GA; (3) IC/Zr‐TiB; and (4) IC/PFM‐GA. Specimens were thermomechanical aged (1,200,000 cycles, 98 N, 5–55°C) with occlusal axial load on the pontic. Catastrophic and non‐catastrophic events were registered, and removal torque values measured before and after aging. Specimens surviving aging were subjected to loading until failure. Survival, total complication rates, torque loss (%), and bending moments were calculated. Results From 48 specimens, 38 survived aging. Survival rates significantly varied from 16.7% (IC/PFM‐GA) to 100% (IBJ/Zr‐TiB; IBJ/PFM‐GA; IC/Zr‐TiB) ( p < .01). Internal conical connection revealed significantly higher torque loss (IC/ZrTiB – 67%) compared to internal butt‐joint (IBJ/Zr‐TiB – 44%; IBJ/PFM‐GA – 46%) ( p < .01). Bending moments were higher in internal butt‐joint connections than in internal conical ( p < .05). Conclusion and Clinical Implications Two‐unit posterior implant‐supported cantilever FDPs replacing mandibular premolars composed of monolithic zirconia on titanium‐base abutments demonstrated higher mechanical stability compared to porcelain‐fused‐to‐metal on castable gold abutments in this in vitro study. The internal conical connection combined with porcelain‐fused‐to‐metal on gold abutments revealed a high number of failures; therefore, their clinical use may be considered cautiously for this indication.