Relationship Between Primary Stability and Crestal Bone Loss of Implants Placed with High Insertion Torque: A 3-Year Prospective Study

Purpose: Concerns have been expressed about the possibility of high insertion torque (IT) causing necrosis, impaired osseointegration, and crestal bone loss over time. The present study investigated the relationship between primary stability and implant success, including early and late maintenance of crestal bone levels. Materials and Methods: Implants were placed in patients at three study centers. Every effort was made to achieve the highest possible primary stability, which was measured with IT and implant stability quotient (ISQ). The IT and ISQ at insertion and reopening (3 to 4 months), as well as bone levels at several points in time, were recorded. The correlations between IT, ISQ, and immediate and 3-year crestal bone loss were investigated through linear regression analyses. Results: Average IT was 76.1 +/- 20.8 Ncm, while the average ISQ score was 80.4 +/- 8.4. The implant success rate at 36 months was 98.6%. The crestal bone loss around most implants (41.0%) ranged from 0.05 to 0.5 mm. None of the osseointegrated implants had crestal bone loss greater than 2.5 mm. The linear regression analysis showed no correlation among early or 3-year crestal bone loss and IT, ISQ at surgery, and ISQ at reopening. Conclusion: The implants studied avoided any negative effects deriving from the high IT values (>50 Ncm) applied during 3 years of follow-up.