title: Inactivated periods of constant orthodontic forces related to desirable tooth movement in rats.
abstract: OBJECTIVE
  To examine the effects of inactive periods of force on the amount of tooth displacement and root resorption during experimental tooth movement in rats.
  
  
  METHODS
  Sixty 11-week-old male Sprague-Dawley rats.
  
  
  METHODS
  The maxillary first molar (M1) was moved mesially using a removable titanium-nickel alloy closed coil spring for 14 days. The rats were divided into four groups with, 0, 1, 4, and 9 hours of inactivation per day.
  
  
  RESULTS
  Tooth displacement in the 0- and 1-hour groups was significantly greater than that in the 9-hour group. The area of root resorption in the 4- and 9-hour groups was significantly less than that in the 0- and 1-hour groups. There was no significant difference in root resorption between 0- and 1-hour groups, and also between 4- and 9-hour groups.
  
  
  CONCLUSIONS
  The distance of tooth displacement gradually decreased as the inactive period increased, whereas root resorption suddenly decreased between 1 and 4 hours of inactive orthodontic force.
authors.affiliation: Science Department of Orofacial Development and Function, Tokyo Medical and Dental University, Japan. kame.orts@tmd.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kameyama
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: H
authors.initials: H
authors.lastname: Warita
authors.forename: K
authors.initials: K
authors.lastname: Soma
mesh_terms: D000818:Animals; D003799:Dental Stress Analysis / Q000379:methods; D008297:Male; D008437:Maxilla / Q000033:anatomy & histology; D008963:Molar / Q000033:anatomy & histology; D016382:Orthodontic Appliance Design; D009970:Orthodontics / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012391:Root Resorption / Q000209:etiology*; D013314:Stress, Mechanical; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000009:adverse effects* / Q000379:methods*