Effect of Loading Frequency on Fatigue Strength of Titanium Implants

Objective: The objective of this study was to determine whether the loading frequency, either 2 Hz or 15 Hz, had an effect on the fatigue strength of titanium dental implants. Methods: Using the set-up as described in ISO 14801, 3.75 mm X 15 mm titanium dental implants (Nobel Biocare AB) were cyclic load tested to success or failure in three different environments; air, distilled water and saline. Success was considered 5 X 10⁶ cycles. The fatigue strength was the maximum load under which 3 consecutive implants were successful. Results: The fatigue strengths at 2 Hz were as follows: air- 225 N, water- 200 N and saline- 275 N. The mean at 2 Hz was 233.33 N. At 15 Hz the results were: air- 250 N, water- 275 N and saline 250 N. The mean at 15 Hz was 258.33 N. A 2-way ANOVA demonstrated the interaction of environment and loading frequency was highly significant (p< 0.001) as were the main effects environment (p< 0.001)and loading frequency (p < 0.001) Conclusion: The loading frequency had a statistically significant effect on measured fatigue strength in titanium dental implants. The measured strength at the faster loading rate, 15 Hz, was higher than with a 2 Hz loading force when all environments were grouped. However, the interaction of the environment with the loading frequency did have a statistically significant effect on the fatigue strength as well, so it was not possible to make a universal statement regarding the effect of loading frequency on measured fatigue strength in titanium dental implants without also taking into account environment effects.