Histomorphometric evaluation of the effect of systemic osteoprotegerin administiration on bone remodeling during retention after experimental tooth movement in rats

The aim of this study was to histomorphometrically evaluate the effect of osteoprotegerin administered following experimental tooth movement, on bone remodeling during retention in rats.Twenty Sprague-Dawley rats were used for this purpose. Orthodontic elastics, 0,5 mm thick, were inserted between the maxillary right first and second molars to achieve orthodontic tooth movement. At the end of the third day the rats were divided into two groups including 10 animals each. One of the groups received 5 mg/kg subcutaneous osteoprotegerin (OPG) twice a week, while the other received volume-matched saline solution. Animals were sacrificed two weeks after the onset of injections. At the end of the experiment, the maxillae of the animals were excised and required sections were prepared for the histomorphometric evaluation.In the histomorphometric evaluation, the volume of alveolar bone between the roots of the teeth that underwent orthodontic force were found to be 0,347±0,035 mm3 in the control group and 0,737±0,039 mm3 in the OPG group. In the OPG group, the volume of alveolar bone between the roots was significantly higher than the control group (p<0,001). The volume fractions of alveolar bone in the interradicular area, were found to be 43±1,8 % in the control group and 55±3,3 % in the OPG group. In the OPG group the volume fraction of alveolar bone in the interradicular area was significantly higher than the control group (p<0,05).In this study, it was concluded that administration of osteoprotegerin, which inhibits osteoclastic activity, following orthodontic tooth movement may have a positive effect on bone formation during bone remodeling and thus reduce relapse potential.Key Words: Orthodontic tooth movement, relapse, remodeling, osteoprotegerin, retention