Effect of dental implant diameter on fatigue performance. Part I: Mechanical behavior

Aim: The purpose of this study was to evaluate the effect of the implants' diameter on the mechanical function and load-fatigue performance of dental implants. Materials and Methods: Three groups of implants with different diameters (3.3mm, 3.75mm and 5mm), were tested under static and cyclic compressive loading. A total number of 15 implants for the static test and 112 implants for the cyclic-fatigue test. In the cyclic test, the machine ceased operating when the structure collapsed or when it reached 5×10⁶ cycles without apparent failure. The load versus the number of cycles was plotted as curves for biomechanical analysis (S-N curve) for each implant diameter. Results: The S-N curve plotted for the 5mm implants showed classic fatigue behavior with a finite life region starting from 620N. The same was observed for the 3.75mm diameter implants, with a finite life region starting below 620N. By contrast, the 3.3mm diameter implants failed to show predictable fatigue behavior and a fatigue limit could not be defined. Conclusions: The results of this study emphasize the importance of implant diameter on fatigue behavior. Narrow implants failed to show typical fatigue behavior which might be attributed to the implant design.