[An experimental study on the relationship between the orthodontic tooth movements and menstrual cycle]

The purpose of this study was to explore the relationship between the menstrual cycle and orthodontic tooth movement.

A Wistar rat model was established to apply orthodontic activation during different stages of the estrous cycle. The distances of the tooth movements were measured and the serum estradiol level was detected by radioimmunoassay. The data of each group was analyzed with SPSS11.0 software package for Student-Newman-Keuls(S-N-K)test and one way ANOVA test. And cosinor-rhythmometry method was used for chronobiologic analysis to show the rhythmic change of the serum estradiol level.

There was a 5-day rhythm of the rat serum estradiol during the estrous cycle. The distances of orthodontic tooth movement were different at various stages. Teeth moved fastest in the estrus while the serum estradiol was lowest (P<0.05), the distance of tooth moved was (2.10+/-0.14)mm. And teeth moved slowest in the proestrus while the serum estradiol was highest (P+/-0.05), the distance of tooth moved was (1.79+/-0.03)mm. Totally, orthodontic activation increased the serum estradiol level without disturbing its fluctuating rhythm.

It was inferred that female patients may have an optimal opportunity of orthodontic activation for rapid tooth movement, which should be applied on a few days before the menorrhea in order to move the teeth rapidly.