Abstract
About 35 upper central incisors having different periodontal conditions, the returning phase of the tooth from labial to the original position after sudden removal of labial forces (50g, 100g, 200g) was observed by using the tooth-mobility measuring apparatus applied a electromicrometer which was reported previously.
The results are as follows:
1. Two different aspects was observed in returning phase of the tooth and designated as rapid return phase and slow return phase.
2. The author classified various types of returning phases of the teeth into four types.
1) Gradual perfect return type: the tooth return perfectly to the original position in about 180 seconds.
2) Quick perfect return type: the tooth return quickly and perfectly to the original position in about 60 seconds.
3) Imperfect return type: the tooth can not return perfectly to the original position even after the lapse of 180 seconds and leaves the displacement of several microns.
4) Lingual displacing type: the tooth displaces lingually beyond the original position.
