Osteoclast distribution within the rat interdental septum coincident to experimental tooth movement using light forces.

There is little quantitative information concerning the number and distribution of bone-matrix resorbing osteoclasts (BMRO) within the adjacent alveolar bone coincident to tooth movement. We moved the right first maxillary molar tooth anteriorly in 40 female rats (E), the left side was untreated, serving as an internal control (IC). Forty female age and weight matched rats were untreated, serving as external controls (EC). BMRO were identified on periosteal and endosteal surfaces of the interdental septum from 1-5 days after initial force application using the MTB-322 antibody. The number of BMRO at periosteal surfaces of E was greater in IC and EC from 2-5 days (P < 0.001). Similarly, the number of BMRO at endosteal surfaces was greater from 1-5 days (P < 0.001). The number of BMRO at periosteal and endosteal surfaces was greater within E than within EC from 1-5 days (P < 0.001). Outcome data from IC were often significantly different from EC. Our data suggest that relatively low forces increase the number of BMRO, which are not uniformly distributed onto both periosteal and endosteal surfaces. Thus, the interdental septum resorbs at the alveolar wall and within spaces between the trabeculae, which, taken together, results in net removal of bone from areas of compression. These data also suggest that experimental tooth movement produces significant differences in the number and distribution of BMRO within IC and EC. Thus, EC groups should be included in studies of tooth movement.