The effect of orthodontic force on early root resorption repair in rats

Objective:To investigate the effect of the mode of orthodontic force on the early repair of root resorption of rats.Method:Having been applied orthodontic forces to induce root resorption,65 SD rats were randomly divided into 3 groups for experimental tooth movement,which were the force suspended group、the intermittent force group、the continuous force group and another 5 rats served as non-treatmental control group.The maxilla of the rats were prepared and processed for histological analysis.The selected tissue sections were treated with hematoxylin-eosin (HE)and tartrateresistant acid phosphatase (TRAP)histochemistry in the aim of observing the histological morphologic alterations of the root.Result:The amount of odontoclasts decreased with the lengthening of the time of suspension of orthodontic force while the newly produced cementum increased.No statistical difference of root resorption and root repair were found between intermittent force group and the force suspended group (P 0.05).whereas on day 17,the amount of TRAP (+) cells and the root resorption in intermittent force group were significantly lower than those in the continuous force group(P 0.05).Conclusion:Alteration of the mode of orthodontic force may affect the early repair of root resorption.The severity of root resorption can be reduced by permanent or temporary suspension of active orthodontic treatment.