Inactivated periods of constant orthodontic forces related to desirable tooth movement in rats.
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.
Kameyama
T
T
Science Department of Orofacial Development and Function, Tokyo Medical and Dental University, Japan. kame.orts@tmd.ac.jp
Matsumoto
Y
Y
Warita
H
H
Soma
K
K
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*