Methods: An active closed coil spring was bonded with composite from the maxillary first molar to the incisor to facilitate tooth movement. Specimens were collected at 24 hours, 3 days, and 7 days after the initiation of movement. TRAP staining was utilized to compare the number and location of osteoclasts in the PDL’s of orthodontically moving teeth in periostin null and wild type mice.
Results: In the periostin null mice, the osteoclast recruitment appeared to be delayed. The number of TRAP positive cells remained up-regulated on the compression side of the roots by the seventh day whereas the wild-type mice showed a large increase in osteoclast recruitment at the beginning (24 hours and 3 days) but gradually decreased over time (in 7 days). Furthermore, wild-type samples displayed an increase in osteoclast activity on the tension side and generally increased alveolar bone remodeling rate by the seventh day while the periostin null mice had little or no osteoclasts on the tension side.
Conclusion: These data support the idea that the decrease in orthodontic movement in the periostin null mice is due, at least in part, to the delayed osteoclastic recruitment and function in response to mechanical stress in these mice when compared to the wild-type control.