Bone healing at non-submerged implants installed with different insertion torques: a split-mouth histomorphometric randomized controlled trial

Objectives: To evaluate histomorphometrically the healing at implants installed with standard or very low insertion torque values Material and methods: Twelve volunteer patients were recruited, and two screw-shaped titanium devices were installed in the distal segments of the mandible using insertion torque values of either < 10 Ncm or similar to 30 Ncm. The implants were left to heal in a non-submerged fashion. After 8 weeks, biopsies were retrieved, and ground sections were prepared for histological evaluation. Results: Histological slides from 11 patients were available for (n = 11). The new bone in contact with the implant surface was 39.3 +/- 18.5% and 49.4 +/- 9.4% at the < 10 and similar to 30 Ncm sites, respectively. Considering the pre-existing old bone, the total mineralized bone was 46.8 +/- 22.1% at the < 10 Ncm sites and 57.0 +/- 14.1% at the similar to 30 Ncm. No statistically significant differences were found. New bone density and total mineralized bone density were 36.6 +/- 8.1% and 53.0 +/- 13.5% at the < 10 Ncm sites and 35.9 +/- 10.0% and 52.2 +/- 16.0% at the similar to 30 Ncm sites, respectively. No statistically significant differences were disclosed. Conclusion: From the data of the present study, it can be concluded that a trend of higher osseointegration was observed at the similar to 30 Ncm compared to the < 10 Ncm torque group. Nevertheless, it can be concluded that an implant installed with a very low torque may achieve a good integration.