Healing at implants installed from ~ 70- to < 10-Ncm insertion torques: an experimental study in dogs

To evaluate histologically the early healing at implants installed with different insertion torques MATERIAL AND METHODS: Three months after the extraction of the mandibular premolars and of the first molars, two implants were installed monolaterally in the premolar and two in the molar regions of the edentulous alveolar ridge of twelve dogs. The recipient sites were prepared using drills of different diameter to obtain insertion torque of different values, i.e., 30 Ncm (control) or ~ 70 Ncm (test) in the premolar region, and < 10 Ncm (test) or ~ 50 Ncm (control) in the molar region. Six animals were euthanized after 4 weeks and six after 8 weeks of healing. Histological analyses were performed, and the Wilcoxon test was applied for statistical analyses.

After 4 weeks of healing, in the premolar region, the new bone in contact with the implant surface was 65.0 ± 4.6% and 53.9 ± 13.5% at the ~ 30-Ncm and ~ 70-Ncm sites, respectively (p = 0.075). In the premolar region, new bone proportions were 51.4 ± 17.0% and 67.3 ± 7.0% at the < 10-Ncm and ~ 50-Ncm sites, respectively (p = 0.046). After 8 weeks of healing, in the premolar region, new bone reached fractions of 77.7 ± 16.2% at the ~ 30-Ncm sites, and 68.3 ± 12.1% at the ~ 70-Ncm sites (p = 0.028). In the molar region, new bone presented proportions of 70.2 ± 6.4% at the < 10-Ncm sites and 76.2 ± 9.4% at the ~ 50-Ncm sites (p = 0.173).

The insertion torque influenced the osseointegration of implants. Higher values of bone-to-implant contact percentages were registered for insertion torques of ~ 30 Ncm and ~ 50 Ncm. Implants inserted with torque < 10 Ncm became integrated with an optimal osseointegration.