Behavior responses to different orthodontic forces in rats

Objective To investigate the effects of different orthodontic forces on behavior responses during the experimental tooth movement in rats.Methods Seventy-eight 8-week-old male Sprague Dawley rats (266.67ent in g) were randomly assigned into control group and experimental group,with 6 and 72 rats respectively.Rats in experimental group received an orthodontic force moving the upper left molars misally,which counted 50 g or 100 g in two subgroups with 36 rats each.The rats' behavior was evaluated by means of open-field test,mouth wiping test and resistance-tocapture test on Day 1,2,3,5,7 and14.The following parameters were analyzed:number of lines crossed in first 30 seconds and 5 minutes,number of lines crossed to the center of the open field,rearing time in 5 minutes,number of mouth wiping and the score of resistance-to-capture.The Kruskal-Wallis H (K) test was used.Results The tests showed that behavior responses of the experimental group were significantly stronger than that of the control group after treatment.On Day 1,behavior responses decreased in open-field test (P1＜0.05) and then increased back to the blank level till Day 14; the number of mouth wiping behavior and the score of resistance-to-capture increased sharply till Day 2,and then dropped to the blank level gradually.The behavior responses were much stronger in 100 g group than 50 g group (P2＜0.05).Conclusions Orthodontic tooth movement seriously affected the behaviors of the rats,which was related to the force magnitude. Key words: Orthodontic force;  Rat;  Behavior response