3. 치근단이 뽀족할수록, 치조골이 손실될수록 그리고 치근이 흡수될수록 치아는 경사되려는 경향이 강해진다.
4. 원하는 부위에 회전중심을 위치시키기 위한 M/F ratio를 구할 수 있다.
5. 이상적인 교정력은 치주인대 내에 발생하는 최대웅력에 의해 결정되며 그 크기는 회전중심에 따라 다르다.
[영문]
In order to achieve a predictable and physiologic tooth movement, knowing the center of rotation and maximum stress level is of great importance.
The purpose of this study is to locate the center of rotation and estimate the magnitude of ideal orthodontic force according to various root shapes under alveolar crest with analytical method.
Extracted upper canine was scanned to the computer and location of center of rotation, relationship between location of applied force and center of rotation, and ideal magnitude of orthodontic force was derived mathematically by an analysis of stress distribution under various conditions.
The results of the study wave revealed as follows:
1. Location of center of resistance for upper canine used in this study was 42% of root length measured from alveolar crest to apex. The center of rotation moves apically for the blunt root while it moves coronally for tapered root.
2. As the amount of alveolar bone increases, location of center of resistance moves apically linearly, while the amount of root resorption increases, location of center of resistance moves coronally nonlinearly.
3. With more tapering of the root, more alveolar bone loss and more root resorption, the tooth tends to tip easily. Therefore more precise M/F ratio is required for specific center of rotation.
4. M/F ratio needed in order to locate the center of rotation can be calculated by the formula derived.
5. Ideal magnitude of orthodontic force is determined according to maximum stress within the periodontal ligament space and should varied with center of rotation.