Fracture Resistance of Yttria-Stabilized Zirconia Dental Implant Abutments

Purpose: An in vitro study was performed to assess the effect of different degrees of clinical reduction of zirconia abutments on the failure load of clinical assemblies.
Materials and Methods: Zirconia abutments (Y-TZP Ceramic Abutment, Astra Tech) were prepared with 0, 0.5, or 1 mm of external axial reduction starting 1 mm above the height-of-contour. Abutments (n = 10) were attached to implant analogs (25 Ncm torque) embedded in a stainless steel cylinder using Field's metal. Fracture loads (N) were determined when assemblies were loaded at 60° off-axis until failure (Instron, CHS = 0.1 mm/min). Groups were statistically compared using ANOVA ( p < 0.05).
Results: Fracture loads for all assemblies displayed large variations within groups. There were no statistically significant differences ( p > 0.05) among different abutment groups with a mean fracture load of 429 N (±140) for the control group, 576 N (±120) for 0.5-mm margins, and 547 (±139) for 1.0-mm margins. All fractures occurred at the interface where the abutment was connected to the analog.
Conclusion: In this in vitro study of simulated ultimate assembly strength, the preparation of zirconia abutments did not significantly impair the fracture resistance of simulated implant assemblies. All implant abutments fractured at rates higher than the maximum incisal forces (90–370 N) estimated to occur in the anterior region of the mouth.