OBJECTIVEThe purpose of this article was to investigate the changes of the estrogen and insulin-like growth factors (IGF) level induced by orthodontic tooth movements in order to elucidate the bio-mechanism of orthodontic treatments during the estrous cycle.

METHODSA Wistar rat experimental model was established to apply orthodontic activation during different stages of estrous. The serum and periodontal tissue estradiol level were determined by radioimmunoassay and immunohistochemistry. In situ hybridization was also used to detect the variation of the IGF mRNA expression in the periodontal tissues. The data of each group was analyzed with SPSS 11.0 software package.

RESULTSBoth serum and periodontal estradiol level were increased by orthodontic activation during various stages of the estrous. IGF mRNA expression were also enhanced with the same trend. The estradiol and IGF- I level showed in a similar pattern during the estrous cycle and the rhythm was not changed by the orthodontic activation. There was no rhythm of IGF-II expression found in the estrous cycle.

CONCLUSIONIt was concluded that estrogen and IGF were involved in the remodeling activities induced by the orthodontic activation. The speed of the orthodontic tooth movements was closely related to the estrous cycle.