The effects of tooth movement on estrous-cycle-dependent expression of the estrogen receptor α

The aim of this study was to explore the effects of applying force during the different stages of the estrous cycle on the dynamic expression of alpha estrogen receptors (ER alpha) and the rate of tooth movement, to provide insight into the timing of effective treatment. A repeated, intermittent force was loaded on the first upper molar of female rats five times during specific stages of the estrous cycle. The distance of tooth movement was measured. ER alpha protein and mRNA levels in the periodontal tissue were measured, and the data were analyzed by ANOVA, Student-Newman-Keuls (SNK) and cosinor analysis. The results showed that ER alpha expression varied among the subgroups that received force during different stages of the estrous cycle and exhibited an infradian rhythm in both groups. There were significant variations in the amount of tooth movement among the four subgroups (P < 0.01). We conclude that the highest ER alpha expression and the fastest periodontal remodeling were in the rats that received force during estrus.