Histologic and histometric study of bone resorption after tooth movement in rats.

The effects of orthodontic movement on rat molars produced by a specially designed device have been studied by means of histological and histometric methods. Areas of resorption start to increase after 12 hours and reach a maximum after 48 hours. The number of osteoclasts starts to increase 20 hours after initiation of the orthodontic force attaining its maximum at the 60 hours period. This finding suggests that the initiation of bone resorption is not associated with an increase in the number of osteoclasts.