Cortical bone response adjacent to applied light orthodontic forces in ovariectomized rats

Cortical bone response to experimental orthodontic forces has not been adequately described in the available literature. The aim of this study was to investigate the application of light orthodontic forces on the cortical bone adjacent to the point of their application, in normal and ovariectomized rats. At the age of eight months, twenty-four female rats were divided equally into two groups: normal (group A) and ovariectomized (group B). A 20 gr* orthodontic force was applied to the maxillary right first molars in all animals for 14 days. Histological examination of the maxillary cortical bone, at the level of the first molar of the upper jaw, was performed on both sides of all animals. It was found that light orthodontic forces applied to the upper right first molars of normal rats result in thinner cortical bone with increased osteoblastic activity, normal lamellar orientation and normal distribution of osteocytes compared to the non-affected contralateral side. In ovariectomized rats it was found that light orthodontic forces applied to the upper right first molars result in thickening of the cortex, in comparison to the respective area of the opposite side where no orthodontic forces were applied. It seems that experimental light orthodontic forces, in rats, affect cortical bone remodeling differently, according to their hormonal status, in areas adjacent to the applied forces.