Mode of tooth movement according to the timing of orthodontic force application after extraction

Han, Sung Ho; Hwang, Hyeon Shik

Abstract

This study was performed to compare and analyzed the mode of tooth movement according to the timing of orthodontic force application after extraction. The upper right and left third incisors were carefully extracted at three-week interval in four adult dogs. Both canines were used as an anchorage for the bodily movement of the upper second incisors. Orthodontic force of 100gm was simultaneously applied at one week after extraction on one side four weeks after extraction on the other side using NiTi closed coil spring. While orthodontic force was applied for twelve weeks, the amount of tooth movement was measured at every second week with calipers. The animals were sacrificed at twelve weeks and histologic examination was executed to reveal any difference between both sides. The results were obtained as follows: 1. The tooth movement was likely to be faster in four-week side for the first two seeks while faster in one-week side during next two weeks 2. The rate of tooth movement was fastest during four to six weeks period, then decreased gradually. 3. The total amount of tooth movement was likely to be larger in one-week side compared to four-week side. 4 Any damage to tooth and periodontal tissue could not be seen in the histologic section of one-week side. These results suggest that earlier application of orthodontic force is better than later after extraction in terms of the rate of tooth movement.