Objective To study the role of mammalian target of rapamycin（mTOR） and p70 S6 kinase（p70 S6K） in periodontal tissues remodeling during orthodontic tooth movement. Methods Twenty -four rabbits were chosen to establish rabbit models for the study. The right maxillary teeth of each animal treated by orthodontics were the test sides, and the untreated left teeth were the control sides. The animals were sacrificed at 3, 5, 7, 14 d, espectively. The prepared tissue specimens were processed for the study of the change in the histologic morphology ith HE staining and the expression of p70 S6K in periodontal tissues by reverse transcription-polymerase chain eaction（RT-PCR） and Western blot techniques. Results In the test side, the tranecula of bone became porous nd cells arrayed disorderly, resorption of alveolar bone was observed in histological study. There were many holes n the alveolar bone, osteoblasts were occasionally observed. RT-PCR showed that the expression of p70 S6K mRNA ramatically changed at 3 d. The expression of p70 S6K mRNA in treating periodontal tissues was higher than the ontrol side, especially at 7 d, and then decreased. Compared with the control side, there was significant difference n statistical analysis（P ＜0.01）. The expression of Western blot was same as the RT -PCR. Conclusion Higher xpression of mTOR and p70 S6K during orthodontic tooth movement especially plays an important role in the process f periodontium remodeling.
