Dynamic Fatigue Testing of Narrow-Diameter Dental Implants

Objectives: The test procedures outlined in ISO 14801 were used to evaluate the structural properties and determine the fatigue endurance limit of two “mini-implant” products from 3M™ ESPE™:

–        Ø1.8 mm O-Ball Implant 

–        Ø2.4 mm O-Ball Implant 

Methods: Testing methodology followed the ISO standard for providing an offset bending moment using 30º ± 2º angle to the loading.  Servo-controlled test frames provided the offset bending loading and monitored the resulting displacements.

Static testing was performed to determine the design’s structural properties.  A loading rate of 1 mm/min. was used with n=5 samples per design.

Dynamic testing was performed to determine the design’s fatigue properties using sinusoidal compressive-compressive loading profile, (R-value 10) at 10Hz.  Six load levels based on percentage of the static ultimate strengths were used with n=3 implants per load level.  Testing continued on each specimen until structural failure or 5 million cycles without failure was reached as run out.

Results: From static testing, load vs. displacement curves were produced for determining the structural properties including elastic stiffness, yield strength and ultimate strength.  The mean values and standard deviation of strengths for each design were calculated.

For dynamic testing, semi-log peak load (moment) vs. number of cycle charts were generated to present the fatigue profile for each design.  Statistical analysis was performed per ASTM E739 with 95% confidence bands on the charts with the failed specimens.  The fatigue endurance limit attained for each design was the maximum load magnitude at which all implants completed run out.

Conclusions: The experimental results agreed with scientific theory in showing that the static and dynamic load capacities increase with implant diameter.  The results also illustrated that the clamping mechanism can have a significant impact on the variability of the fatigue measurements.