Experimental tooth movement under light orthodontic forces: rates of tooth movement and changes of the periodontium.
OBJECTIVE
To investigate light forces for experimental tooth movement.


METHODS
Light orthodontic forces of 1.2, 3.6, 6.5, and 10 g force (gf) were applied for 14 days to move rat molars, and the effects of the forces on the rate of tooth movement and changes of the periodontium were examined.


RESULTS
In the early period, despite the different levels of force used in each group, there were no significant differences in tooth displacement. From hour 56 to day 14, the tooth displacement in the 1.2 gf group was significantly smaller than that in the other groups and the rate was nearly constant. The rates of tooth displacement in the 3.6, 6.5, and 10 gf groups fluctuated repeatedly, while the orthodontic forces gradually decreased.


CONCLUSIONS
Experimental tooth movement in rats, tipping without friction under light forces, were either constant or fluctuated in cycles of several days' duration. This is in contradiction to the three-phases-theory of tooth movement described in previous investigations using heavy forces.
Kohno
T
T
Orthodontic Science, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. kohno.orts@tmd.ac.jp
Matsumoto
Y
Y
Kanno
Z
Z
Warita
H
H
Soma
K
K
D000539:Alveolar Process / Q000473:pathology; D000704:Analysis of Variance; D000818:Animals; D001862:Bone Resorption / Q000473:pathology; D003722:Dental Alloys; D008297:Male; D008963:Molar; D009532:Nickel; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D010010:Osteoclasts / Q000473:pathology; D010513:Periodontal Ligament / Q000473:pathology; D010519:Periodontium / Q000473:pathology* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012391:Root Resorption / Q000473:pathology; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium; D014070:Tooth / Q000473:pathology* / Q000503:physiopathology; D014087:Tooth Movement Techniques
D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium