Effect of cyclical forces on the periodontal ligament and alveolar bone remodeling during orthodontic tooth movement.
OBJECTIVE
To investigate the effect of externally applied cyclical (vibratory) forces on the rate of tooth movement, the structural integrity of the periodontal ligament, and alveolar bone remodeling.


METHODS
Twenty-six female Sprague-Dawley rats (7 weeks old) were divided into four groups: CTRL (unloaded), VBO (molars receiving a vibratory stimulus only), TMO (molars receiving an orthodontic spring only), and TMO+VB (molars receiving an orthodontic spring and the additional vibratory stimulus). In TMO and TMO+VB groups, the rat first molars were moved mesially for 2 weeks using Nickel-Titanium coil spring delivering 25 g of force. In VBO and TMO+VB groups, cyclical forces at 0.4 N and 30 Hz were applied occlusally twice a week for 10 minutes. Microfocus X-ray computed tomography analysis and tooth movement measurements were performed on the dissected rat maxillae. Tartrate-resistant acid phosphatase staining and collagen fiber assessment were performed on histological sections.


RESULTS
Cyclical forces significantly inhibited the amount of tooth movement. Histological analysis showed marked disorganization of the collagen fibril structure of the periodontal ligament during tooth movement. Tooth movement caused a significant increase in osteoclast parameters on the compression side of alveolar bone and a significant decrease in bone volume fraction in the molar region compared to controls.


CONCLUSIONS
Tooth movement was significantly inhibited by application of cyclical forces.
a  Postdoctoral Fellow, Department of Craniofacial Sciences, University of Connecticut Health Center, Farmington, Conn.
Zana
Z
Kalajzic
Elizabeth Blake
EB
Peluso
Achint
A
Utreja
Nathaniel
N
Dyment
Jun
J
Nihara
Manshan
M
Xu
Jing
J
Chen
Flavio
F
Uribe
Sunil
S
Wadhwa
D000135:Acid Phosphatase / Q000032:analysis; D000539:Alveolar Process / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling / Q000502:physiology*; D003094:Collagen / Q000032:analysis; D003722:Dental Alloys / Q000737:chemistry; D005260:Female; D007527:Isoenzymes / Q000032:analysis; D008437:Maxilla / Q000502:physiology; D008963:Molar / Q000502:physiology; D009532:Nickel / Q000737:chemistry; D009929:Organ Size; D009969:Orthodontic Wires; D010010:Osteoclasts / Q000166:cytology; D010513:Periodontal Ligament / Q000502:physiology*; D010865:Pilot Projects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D000071681:Tartrate-Resistant Acid Phosphatase; D014025:Titanium / Q000737:chemistry; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods*; D014732:Vibration; D055114:X-Ray Microtomography / Q000379:methods
D003722:Dental Alloys; D007527:Isoenzymes; C040654:titanium nickelide; D009532:Nickel; D003094:Collagen; D014025:Titanium; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase