Intermittent force in orthodontic tooth movement.
A single orthodontic activation lasting one hour can initiate tooth movement. The purpose of this study is to examine tooth movement, osteoclasts, and root resorption in rats following several one-hour activations. Rats (n = 144) were randomly assigned to intermittent (multiple activations of 1 hr/day), continuous, and sham appliances. Twelve rats were killed at 3, 5, 7, and 14 days. Tooth movement, osteoclasts, osteoclast %, and root resorption % were quantified. Continuous force moved molars mesially at days 3 and 14 (p < 0.05), but intermittent and sham did not. Intermittent and continuous force increased osteoclast numbers at days 3, 5, and 7 (p < 0.05). Continuous force increased osteoclast surface on days 3 and 14 (p < 0.05). Continuous force increased root resorption at days 5, 7, and 14 (p < 0.05). These results demonstrate that orthodontic force for one hour in 24 stimulates osteoclasts at compression sites but does not stimulate tooth movement or root resorption.
Konoo
T
T
Department of Orthodontics, Kyushu Dental College, Japan. tetsuro@kyu-dent.ac.jp
Kim
Y J
YJ
Gu
G M
GM
King
G J
GJ
D000539:Alveolar Process / Q000473:pathology; D000818:Animals; D016723:Bone Remodeling; D002508:Cephalometry; D003799:Dental Stress Analysis; D008297:Male; D008437:Maxilla; D008963:Molar; D010010:Osteoclasts / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012391:Root Resorption / Q000209:etiology* / Q000473:pathology / Q000517:prevention & control; D018709:Statistics, Nonparametric; D014087:Tooth Movement Techniques / Q000009:adverse effects