Load Limit of Mini-Implants with Reduced Abutment Height Based on Fatigue Fracture Resistance: Experimental and Finite Element Study

Purpose: The primary objective of this study was to investigate the fracture resistance of experimental mini-implants with a reduced abutment height. The secondary objective was to assess the effects of implant diameter and bone level on the load limit, using finite element simulations. Materials and Methods: Two Ti-6A1-4V 1.8-mm-diameter implants were subjected to monotonic bending testing and fatigue tests incorporating 5 × 106 cycles (ISO 14801): a commercially available implant (c18), and an experimental implant with a reduced abutment height (e18). The load limit was estimated using the finite element models based on the maximum stress at failure in the experiments. For simulations, implants with increased diameters of 2.1 and 2.4 mm were also modeled, and the load limit was estimated for all models in a bone model. Results: In the bending test, e18 revealed a higher mean load at yield stress than c18, and this was attributed to the reduced height of the former. An endurance limit of 140 N was detected for both c18 and e18 in the fatigue test, while the load limit of e18 was higher than that of c18. The estimated load limit increased as the implant diameter or the bone level increased, with the highest value of 510 N observed at a diameter of 2.4 mm. Conclusion: A higher load limit was evident in the experimental mini-implant with a reduced abutment height. The simulations indicated that the load limit increased with increased implant diameter and higher bone levels. Keywords: fatigue, finite element analysis, implant, prosthodontics, stress, titanium