Effect of Implant Thread Geometry on Secondary Stability, Bone Density, and Bone-to-Implant Contact: A Biomechanical and Histological Analysis.

PURPOSE

This study evaluated the effect of 2 different thread designs on secondary stability (micromotion) and osseointegration rate in dense and cancellous bones.

MATERIALS AND METHODS

Forty large threaded and 40 small threaded implants (Cortex) were placed in low- (iliac crest) and high-density (mandible) bone of sheep. Two months later, micromobility tests and histological analysis were performed to measure secondary stability, osseointegration (bone-to-implant contact percentage [%BIC]), and bone density (bone volume percentage [%BV]). The value of actual micromotion of implant is introduced as a new parameter to evaluate secondary stability.

RESULTS

Large threaded implants showed significantly higher %BIC and %BV than small threaded implants in low-density bone and statistically higher secondary stability in cancellous and cortical bones.

CONCLUSIONS

Implants in dense bone reach higher secondary stability than those in cancellous bone, despite the lower %BIC. Implant geometry and bone density play a key role in secondary stability. Large thread design improves bone anchorage mechanically and histologically as compared with small threaded implants.