[Forced tooth movement in rats and its histologic changes].

The first upper molars in 140 young adult wistar rats were moved buccally by fixed appliance. The phenomena of tooth movement and its periodontal tissue changes has been investigated systematically. The results indicate that the tooth movement can be divided into three periods: rapid movement reversal movement and slow persistent movement. The compression of the periodontium was the main cause of the rapid movement; The rising of the tissue pressure caused by tissue edema probably resulted in the reversal movement and the remoulding of the alveoli at the pressure side caused the slow, persistent movement. This experiment also indicates that the total distance of tooth movement at the end of each experiment is not related to the magnitude of the force applied. In general, the heavy force makes the extent of the necrosis larger and the time necessary for tissue recovery longer. The above phenomena suggest that in clinical practice, it is important to acquire rapid, effective tooth movement while avoiding undue tissue injury.