Occlusal hypofunction causes periodontal atrophy and VEGF/VEGFR inhibition in tooth movement.
OBJECTIVE
To examine changes in microvasculature and the expression of vascular endothelial growth factor A (VEGF-A) and VEGF receptor 2 (VEGFR-2) in rat hypofunctional periodontal ligament (PDL) during experimental tooth movement.


METHODS
Twelve-week-old male Sprague-Dawley rats were divided into normal occlusion and occlusal hypofunction groups. After a 2-week bite-raising period, rat first molar was moved mesially using a 10-gf titanium-nickel alloy closed coil spring in both groups. On days 0, 1, 2, 3, and 7 after tooth movement, histologic changes were examined by micro-computed tomography and immunohistochemistry using CD31, VEGF-A, VEGFR-2, and the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) method.


RESULTS
Hypofunctional molars inclined more than normal molars and did not move notably after day 1 of tooth movement. Blood vessels increased on the tension side of the PDL in normal teeth. Immunoreactivities for VEGF-A and VEGFR-2 in normal teeth were greater than those in hypofunctional teeth during tooth movement. Compressive force rapidly caused apoptosis of the PDL and vascular endothelial cells in hypofunctional teeth, but not in normal teeth.


CONCLUSIONS
Occlusal hypofunction induces vascular constriction through a decrease in the expression of VEGF-A and VEGFR-2, and apoptosis of the PDL and vascular cells occurs during tooth movement.
Orthodontic Science, Department of Orofacial Development and Function, Division of Oral Health Science, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Risa
R
Usumi-Fujita
Jun
J
Hosomichi
Noriaki
N
Ono
Naoki
N
Shibutani
Sawa
S
Kaneko
Yasuhiro
Y
Shimizu
Takashi
T
Ono
D000818:Animals; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008297:Male; D008310:Malocclusion / Q000150:complications* / Q000473:pathology; D008963:Molar / Q000002:abnormalities* / Q000098:blood supply; D055093:Periodontal Atrophy / Q000209:etiology*; D010513:Periodontal Ligament / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000009:adverse effects* / Q000379:methods; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*; D055114:X-Ray Microtomography
D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2