Fatigue resistance of a two‐piece zirconia oral implant. An investigation in the chewing simulator.

Kohal R, Fross A, Adolfsson E, Bagegni A, Doerken S, Spies BC

Fatigue resistance of a two‐piece zirconia oral implant. An investigation in the chewing simulator.

Kohal R, Fross A, Adolfsson E, Bagegni A, Doerken S, Spies BC: Fatigue resistance of a two‐piece zirconia oral implant. An investigation in the chewing simulator. Clin Oral Implan Res, 2018; 29 Suppl. 17: 54. : https://doi.org/10.1111/clr.11_13356

Originalarbeiten in wissenschaftlichen Fachzeitschriften

Background Early ceramic implants made from mono‐ or polycrystalline alumina had a reduced fracture resistance. With the use of yttria‐stabilized zirconia as implant material, stability of ceramic implants increased due to the allotropic character of this ceramic material allowing for a phase transformation toughening mechanism. A further development are zirconia composite materials like alumina‐toughened zirconia (ATZ) which is characterized by increased stability and decreased degradation kinetics. Aim/Hypothesis The purpose of the present study was to evaluate the thermomechanical stability of a two‐piece ceramic implant made from ATZ ceramic in a chewing simulator and the fracture strength in a static loading test. These results were compared with those of two‐piece titanium implants of a similar design. Material and Methods Three different 2‐piece implant systems (ATZ Z‐ test group, titanium T and titanium‐zirconium TZ‐ control groups, n = 16 samples per group) were used. Of the 16 samples per group, 8 were subjected to a simultaneous aging loading procedure (L) in a chewing simulator and the remaining 8 served as reference without any load aging (N). This resulted in six subgroups (ZL, ZN, TL, TN, TZL, TZN). The loaded subgroups were subjected to 10 million loading cycles (F = 98 N) in a +85 °C hot aqueous environment in the chewing simulator. One sample per subgroup (n = 6) was evaluated for gap size of the implant‐abutment‐connection. 42 implants were finally loaded to fracture in a static loading test and statistically analyzed. Estimates of the P‐values and the 95% confidence intervals were derived from a multivariate linear regression model. To make a correction for multiple testing, P‐values were adjusted according to the Student‐Newman‐Keuls (SNK) method and several pairwise comparisons were made. Results The dynamically applied load of F=98 N resulted in an exerted bending moment of M=53.9 Ncm during the loading aging procedure. All implants survived the 10 million loading cycles with simultaneous hydrothermal aging in the chewing simulator. For the static load test, the following average bending moments were obtained (Table)‐ ZL‐ 614 Ncm, Zn‐ 614 Ncm, TZL‐ 735 Ncm, TZN‐ 756 Ncm, TL‐ 673 Ncm, TN‐ 683 Ncm. In no group, loading aging affected the fracture load bending moments (P = 0.727). Independent of loading aging, TZ implants showed higher fracture loads than Z implants (P = 0.002). No significant difference between T and TZ (P = 0.072) as well as Z and T (P = 0.086) could be observed. Multiple pairwise comparisons between all subgroups (ZL, ZN, TL, TN, TZL, TZN) revealed significant differences between ZN and TZN (P = 0.007) as well as ZL and TZL (P = 0.007). All other differences were statistically insignificant. Conclusions and Clinical Implications Within the limits of the present investigation it can be concluded, that thermomechanical loading in an artificial mouth had no negative impact on the fracture strength value of the tested ceramic implants. From a mechanical point of view and based on the limitations of the present setup, the evaluated ATZ implant system will resist physiological chewing forces long‐term. The investigation was in part (the loading hemispheres were provided) supported by the Straumann AG and Dentalpoint AG.

https://doi.org/10.1111/clr.11_13356