title: The Effect of Ovariectomy and Orchiectomy on Orthodontic Tooth Movement and Root Resorption in Wistar Rats.
abstract: BACKGROUND
  Root resorption (RR) after orthodontic tooth movement (OTM) is known as a multifactorial complication of orthodontic treatments. Hormonal deficiencies and their effect on bone turnover are reported to have influences on the rate of tooth movement and root resorption.
  
  
  OBJECTIVE
  This study was designed to evaluate the effect of female and male steroid sex hormones on tooth movement and root resorption.
  
  
  METHODS
  Orthodontic appliances were placed on the right maxillary first molars of 10 ovariectomized female and 10 orchiectomized male Wistar rats as experimental groups and 10 female and 10 male healthy Wistar rats as control groups. NiTi closed-coil springs (9mm, Medium, 011"×.030", Ortho Technology(®); Tampa, Florida) were placed between the right incisors and the first right maxillary molars to induce tipping movement in the first molars with the application of a 60g force. After 21 days, the rats were sacrificed and tooth movement was measured by using a digital caliper (Guanglu, China). Orthodontic induced root resorption (OIRR) was assessed by histomorphometric analysis after hematoxylin and eosin staining of sections of the mesial root.
  
  
  RESULTS
  The rate of tooth movement was significantly higher in all female rats, with the root resorption being lower in the experimental group. The rate of tooth movement in experimental male rats was significantly higher than the control group (p= 0.001) and the rate of root resorption was significantly lower in the experimental group (p= 0.001).
  
  
  CONCLUSIONS
  It seems that alterations in plasma levels of estrogen, progesterone, and testosterone hormones can influence the rate of OTM and RR. The acceleration in tooth movement increased OTM and decreased RR.
authors.affiliation: Dept. of Orthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Massoud
authors.initials: M
authors.lastname: Seifi
authors.affiliation: Dept. of Prosthodontics, School of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Baharak
authors.initials: B
authors.lastname: Ezzati
authors.affiliation: Researcher, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Saedi
authors.affiliation: Research Institute for Endocrine Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Hedayati
keywords: Estrogen; Orthodontic Tooth Movement; Progesterone; Root Resorption; Testosterone