[Stabilized position of incisors after orthodontic treatment on reversed occlusion cases with skeletal imbalance. Application of quadrilateral analysis].

Abstract

This study was made to evaluate the position of the incisors after orthodontic treatment on reversed occlusion cases with skeletal imbalance and to establish norms of the upper and lower central incisors on the quadrilateral (quadrilateral analysis) as the orthodontic treatment objectives through lateral cephalograms. The materials used for this study consisted of twenty-eight posttreatment lateral cephalograms which were taken at more than 2 years after active treatment, and twenty lateral cephalograms which were taken from young-adult females with normal occlusion. The treated samples were of twenty-eight females which were over 14 years old and had reversed occlusion with less than 2 degrees of ANB angle at first examination. These samples were divided into two groups: one consisted of 17 cases females with more than 0 degree of ANB angle and the other of 11 cases with less than 0 degree of ANB. And 11 cases which were treated with multi-bracket appliance alone were selected from the treated samples in order to examine the morphological changes during orthodontic treatment. The results were as follows: 1. In the treated sample the mean profile showed protrusion of the soft pogonion and had slightly forward position of the upper lip and the lower lip, but the outline from the subnasale to the soft pogonion coincided with that of the normal occlusion sample. 2. The ANB angle of the treated sample was smaller than that of the normal occlusion sample so that the mandible of the treated sample was prognathic. 3. The overjet of the treated sample revealed normally in spite of this skeletal disharmony because of compensation by labial inclination of the upper incisors and lingual inclination of the lower incisors. The stronger this skeletal imbalance was, the more the upper incisors inclined labially. But the Ll-Mp showed no difference between the groups which had more than 0 degree of ANB angle and that which less than 0 degree of ANB. 4. The edges of the maxillary and mandibular central incisors always were at a certain place from A'B' line not undergoing an effect of the jaw relationship, and the edge of the mandibular central incisor placed at 8 mm in front of A'B' line. 5. In the treated sample the mandibular central incisor positioned at 1 mm above the occlusal plane. 6. Occlusal plane-A'B' angles in the treated and the normal occlusion samples were revealed about 90 degrees.(ABSTRACT TRUNCATED AT 400 WORDS)