In Vitro Fatigue and Fracture Strength Testing of One-Piece Zirconia Implant Abutments and Zirconia Implant Abutments Connected to Titanium Cores

Purpose: The purpose of this study was to determine the fatigue and fracture strength of zirconia implant abutments connected to titanium cores (ZrTi) and one-piece zirconia implant abutments (Zr). Materials and Methods: Thirty-two implants were secured into epoxy resin blocks and connected with abutments. Eight specimens of each group (Zr with a diameter of 3.75 mm [Zr3.75] or 5.5 mm [Zr5.5] and ZrTi with a diameter of 3.75 mm [ZrTi3.75] or 5.5 mm [ZrTi5.5]) were thermally cycled from 5°C to 55°C and loaded with 100,000 cycles at 120 N at 30 degrees off-axis. All specimens were then tested for fracture resistance using a compressive load at 30 degrees off-axis. Results: Abutment fracture or screw loosening was not observed during thermal cycling and cyclic loading. The median fracture resistance values and standard deviations were 526 N (± 32 N) for group Zr3.75, 1,241 N (± 269 N) for group ZrTi3.75, 1,894 N (± 137 N) for group Zr5.5, and 2,225 N (± 63 N) for group ZrTi5.5. Statistically significant differences in fracture strength were found between Zr and ZrTi for each implant diameter. Conclusions: Zirconia implant abutments connected to titanium cores showed higher fracture strength compared to one-piece zirconia abutments. Hence, they might be preferable for clinical use.