60 黃昭慈 / Chao-Tzu Huang
Main Instructor Heng-Ming Chang
Department / Institution Orthodontic Department, Chang Bing Show Chwan Memorial Hospital
Classification case report
The aim of this case report is to introduce the mandible backward rotation technique (MBRT) and to present its effects in a class III bimaxillary hypodivergent case.
A 25-year-old female presented class III malocclusion with hypodivergent facial pattern and protrusive lips.
The treatment goal was to improve the overall esthetics, especially the protrusive lips and the relatively prominent chin. Non-extraction orthodontic approach was decided with the aids of the temporary anchorage devices (TADs) for lower arch distalization.
Reverse curve of Spee was applied to compensate the side effects (i.e. retroclination and extrusion of the lower incisors) while retracting the lower arch from the TADs. Then, instead of class III elastics, we applied class II elastics to enhance clockwise rotation of the occlusal plane by extruding lower molars and upper incisors. By applying MBRT mechanics and the total arch distalization, the protrusive lips and chin were corrected. More pleasant facial profile was achieved and the overall outcome of treatment was satisfactory.
MBRT has demonstrated to be an effective mechanics on the treatment of mild class III malocclusion with hypodivergent pattern. Rotating occlusal plane as well as mandibular plane backward is beneficial to the enhancement of upper incisor show and the reduction of chin prominence. Class II, rather than class III, elastic plays an important role in MBRT mechanics. With the proper use of this mechanics, overall facial esthetics of this type of malocclusion can be improved.
Application of Mandible Backward Rotation Technique (MBRT) in a Class III Bimaxillary Hypodivergent Case