Abstract
This cephalometrical study was undertaken to look into morphological changes in the mandibular symphysis in patients with class I crowded malocclusion after treatment by means of edgewise appliances without premolar extraction. In addition, the effectiveness of this orthodontic treatment procedure was evaluated clinically.
The following is a summary of our findings.
1) The basal bone in the mandibular symphysis tilted lingually to a significantly large extent when cephalometrically observed after treatment.
2) The inclination of the basal bone had a negative correlation with the facial angle and a positive correlation with the occlusal plane angle.
3) The alveolar bone in the mandibular symphysis showed a significant labial inclination.
4) The inclination of the alveolar bone correlated positively to the labial inclination of the mandibular incisors.
5) The angle formed between the basal bone and the alveolar bone increased significantly.
6) The symphyseal thickness at point B decreased significantly.
7) The symphyseal height at points B, Id and Ll e also showed a significant increase.
8) The symphyseal height at points B and L I e correlated negatively to the increase in the occlusal plane angle respectively.
9) The increase in the symphyseal height at point Id correlated negatively to the labial inclination of the mandibular incisors.
The above-mentioned results suggested that morphological changes occur flexibly in the mandibular symphysis in the wake of mechanotherapy for Angle's class I crowding case by using the edgewise appliance without premolar extraction. Moreover, the area near point B in the mandibular symphysis appeared to play a pivotal role in bone remodeling. It was also suggested that this orthodontic treatment procedure we had used without removing premolars at the permanent dentition period should be taken into consideration in making plans for treating the crowding of teeth at the stage of
