Effect of Dental Implant Diameter on Fatigue Performance

Objectives: Prospective studies showed a decrease in success rate of narrow implants after a few years in function caused by implant body breakdown. The purpose of this study was to evaluate the effect of implant diameter on mechanical function and load-fatigue performance in maximal oral bite force. Materials and methods: Test implants, D= 3.3 mm (n=5), D=3.75 mm (n=5) and D= 5 mm (n=5) in diameter, were loaded with cyclic compressive force using a servo hydraulic machine. Testing was carried out in room air at ambient temperature. Force magnitude was identical to the typical maximum bite force and reached 620N. The force was applied on the implant abutment in a 30̊ angle to the implant longitudinal axis thus creating a bending moment. The machine stopped working when the structure collapsed or when it reached 5X106 cycles without apparent failure. The number of cycles to failure and the failure mode were recorded. Results: All narrow diameter implants (3.3mm) failed before reaching 5X106 cycles. The average number of cycles to failure was 30,186 cycles. The mode of failure was a crack in the implant body. One standard 3.75 mm implant failed after 2.3X106 cycles. The mode of failure was a crack in the implant body. The other four 3.75mm implants reached the 5x106 cycles limit without failure. None of the wide diameter implants (5mm) failed. Conclusions: In this preliminary test, narrow diameter implants showed an early failure in the implant body when loaded at maximal oral bite force.