Age effect on orthodontic tooth movement in rats.

Orthodontic procedures seem to be more time-consuming in adults than in juveniles. This might be related to delay in the initial tissue response or to a slower turnover of the bone and periodontal ligament in adults. To study this problem, we studied orthodontic tooth movement in two groups of 30 rats, aged 6 wks and 9-12 mos, respectively. At one side of the maxilla, 3 molars together were moved mesially with a standardized orthodontic appliance delivering a force of 10 cN. The other side served as a control. The results showed a faster initial tooth movement in juvenile than in adult animals. However, once tooth movement had reached the linear phase, the rate of tooth movement was the same in both groups. The results indicate that, besides a delay in the onset of tooth movement in adult animals, tooth movement could be equally efficient in adults once it had started.