A histomorphometric analysis of heavily loaded and non-loaded implants

Purpose: To investigate the bone tissue response at the interface of loaded and non-loaded implants used in an orthopedic anchorage system after a continuous, non-axial force application of 5 N over 2 months. Materials and Methods: Twenty-nine Branemark System implants were placed in the Zygomatic arches of 5 dogs. After a healing period of 8 weeks, 20 implants (4 in each dog) were loaded during 8 weeks with a large non-axial orthopedic force application of 5 N. This force was directed between the implants and a maxillary splint to move the maxilla forward. Nine implants were not loaded during this period. At the termination of the experiment, all 29 implants were retrieved for radiographic as well as for histologic analysis. Computer-based histomorphometric quantifications were performed via light microscopy and computer software. Bone-metal contact (BMC), bone surface area (BSA) inside the threads, and the bone mirror area (BMA) of the implants were measured. Statistical comparisons between the loaded and non-loaded implants were carried out. In the group of loaded implants a 2-factor analysis of variance was used. Results: There were no statistically significant differences found in BMC, BSA, and BMA between the loaded and non-loaded implants, both for all the threads and for only the cervical region of the implants. Nor were there statistically significant differences between the non-pressure and pressure sides or for different lengths of the loaded implants. Discussion: The loaded implants maintained the osseointegration achieved during the 8-week healing period. Conclusions: The results of this study indicate that titanium implants can be used as anchorage for orthopedic force application systems