In treatment of skeletal cl. 2 malocclusion with vertical changes, it is said to be critical if an orthodontist could control not only antero-posterior but vertical dimension in the maxillo-mandibular relationship.
The purpose of this study is to investigate what is concerned most with vertical changes in the maxillo-mandibular relationship in orthodontic treatment, and the possibility to find any signs before treatment.
Taking note of changes in vertical dimension, the subjects were divided into two groups according to the increase (PP-MP (+)) and the decrease (PP-MP (-)) in the angle formed by palatal plane and mandibular plane through orthodontic treatment. The two groups were compared with before-and after-treatment, and these differences.
The results were as follows.1.Before treatment, PP-MP (+) was identified with clockwise rotation of the mandible with a wide ramus inclination, and also excessive heights in the maxillary incisor and molar, as well as the mandibular incisor. It seemed to share these features with an open bit ecase, except for the rest of a wide gonial angle, short ramus, and steep mandibular plane.2. In the difference between before and after treatment, PP-MP (-) indicated clockwise rotation of the palatal plane, narrowness of the mandibular plane and gonial angle, while PP-MP (+) presented itself counter-clockwise rotation of the palatal plane, acute mandibular plane and gonial angle, all of which had a corresponding effect on an increase in the vertical dimension on the maxillo-mandibular relationship.
In changes in the denture pattern, PP-MP (-) showed counter-clockwise rotation of the occlusal plane. However, PP-MP (+) indicated lingual inclination of the upper incisors and clockwise rotation of the occlusal plane, whose changes seemed to act in compensation for antero-posterior and vertical relationship of the jaw.
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