Mechanics in the Production of Mandibular Fractures: A Study with the "Stresscoat" Technique. I. Symphyseal Impacts

¹ Department of Anatomy, University of Michigan Medical School Ann Arbor, Michigan

Forces and impacts to the symphysis of the mandible cause deformations which are specific in their location. Most frequently these impacts cause a deformation of the neck of the mandible, the type of deformation depending on the method of condylar fixation. This deformation may be a medial or lateral bending of the condyle or a vibration of the subcondylar region itself. In addition, the lingual aspect of the chin tends to flatten because of the application of the force to the opposite side of the bone. Tensile stresses and strains tend to concentrate about the mental foramen, buccal alveolar walls, lingula and lingual tuberosity, oblique line, buccal shelf, and inferior margin of the mandible. However, following chin impacts, these areas are not so frequently involved either clinically or experimentally. Additionally, the coronoid process tends to vibrate because of chin impacts when the condyles are firmly fixed. Clinical data have shown that any area of the mandible may be fractured by impacts to the chin region, with the subcondylar region being most frequently involved. The experimental results of the present study also indicate that all areas of the mandible may develop high tensile stresses and strains due to impacts to the chin and that the subcondylar region is most frequently involved.