Bone reactions around dental implants subjected to progressive static load: an experimental study in dogs

ObjectiveTo evaluate histologically and histomorphometrically, the peri-implant bone reaction around implants subjected to controlled progressive orthodontic loading. Materials and methodsIn three beagle dogs, bilateral edentulous flat alveolar ridges were created in the maxillary area posterior to the canines. After 8weeks of healing, 24 implants (Biomet 3i) were inserted in the edentulous sites. Two experimental groups were created. Progressive loading group: Twelve implants were left to heal for 8weeks uncovered, and abutments were adapted and connected by pairs with Ni-Ti orthodontic springs. A gradual static force of 100, 200 and 300g was applied for a 3-week period each. Thus, a total progressive loading period of 9weeks was exercised. Unloaded control group: Twelve implants were left to heal undisturbed. At the end of the experimental period, all implants of both groups were removed with the surrounding bone. Histologic and histomorphometric analyses were performed, and the following parameters were measured: bone-to-implant contact, bone density 1 and 2mm distant to the implant threads and crestal bone resorption. Median regression models are used for statistical analysis. ResultsImplants of the progressive loading group exhibited significantly higher percentage of bone-to-implant contact compared to the unloaded control implants (P=0.018). Bone density 1 and 2mm distant to the threads was found to be the same between the two groups (P=0.734 and P=0.961, respectively). Crestal bone resorption did not differ between loaded and unloaded implants (P=0.813). ConclusionThe application of progressive loading by controlled orthodontic force on osseointegrated implants provoked significant increase in the percentage of bone-to-implant contact of the low-density bone of the dog maxilla.