The effects of systemic stress on orthodontic tooth movement.
OBJECTIVE
To determine if systemic stress affects the biological reactions occurring during orthodontic tooth movement.


METHODS
Four groups of male 10 week-old Wistar rats were used. Group A animals (N=10) were restrained for one hour per day for 40 days; Group B animals (N=10) were restrained for one hour per day for three days; Group C (N=10) and Group D (N=8) animals were unrestrained. The upper left first molars in the rats in Groups A (long-term stress), B (short-term stress) and C (control) were moved mesially during the last 14 days of the experiment. The animals in Group D (N=8) were used for body weight and hormonal dosage comparisons only. They were not subjected to any stress and did not have appliances fitted. All animals were killed at 18 weeks of age and blood collected for measurement of plasma corticosterone. Tooth movement was measured with an electronic caliper. The right and left hemi-maxillae of five rats from each group were removed and the number of tartrate-resistant acid phosphatase (TRAP) positive cells, defined as osteoclasts, adjacent to the mesial roots of the upper first molars counted. The contralateral side in each animal served as the control (split-mouth design).


RESULTS
Corticosterone levels were significantly higher in the stressed groups (Groups A and B) than in the control group (Group C). Tooth movement was significantly greater in Group A (long-term stress) compared with Group B (short-term stress) and Group C (control), which did not differ from each other. There were significantly more osteoclasts in the long-term stress group than in the short-term stress and control groups.


CONCLUSIONS
Persistent systemic stress increases bone resorption during orthodontic tooth movement. Systemic stress may affect the rate of tooth movement during orthodontic treatment.
Gameiro
Gustavo Hauber
GH
Division of Orthodontics, Piracicaba Dental School, State University of Campinas, UNICAMP, Piracicaba, São Paulo, Brazil. gustavo@gameiro.pro.br
Nouer
Darcy Flávio
DF
Pereira-Neto
Joáo Sarmento
JS
Urtado
Marília Bertoldo
MB
Novaes
Pedro Duarte
PD
de Castro
Margaret
M
Veiga
Maria Cecília Ferraz Arruda
MC
D016301:Alveolar Bone Loss / Q000503:physiopathology*; D000539:Alveolar Process / Q000502:physiology; D000818:Animals; D016723:Bone Remodeling / Q000502:physiology; D002452:Cell Count; D003345:Corticosterone / Q000097:blood; D003799:Dental Stress Analysis; D008297:Male; D008439:Maxillary Diseases / Q000503:physiopathology; D010010:Osteoclasts; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000502:physiology*; D013997:Time Factors; D014087:Tooth Movement Techniques
D003345:Corticosterone