Anatomic study of mandibular fracture mechanism

Objective:To provide anatomical basis for researching the mechanism of mandibular fracture. Methods: 10 cases of fresh adult cadaveric skulls were dissected to observe masticatory muscles and occlusion. Mandibles were transected in order to measure the thickness of cross section of mandible. Results: The data of the mandibular anatomic areas showed that the median symphysis's thickness was (12.4±0.7)mm, mental foramina's was (10.6±1.1)mm, molar's was (14.1±0.9)mm, the angle of mandible's was (6.8±0.5)mm, the anterior foramen's was (10.1±1.0)mm and the posterior foramen's was (6.2±0.5)mm. The mandible got fragile when mandibular third molar was impacted. The bone absorbing and the alveolar ridge descending was followed by the missing tooth. Masticatory muscles adhered to the different sites of mandible like images in mirror. Maxillary teeth contacted with mandibular teeth and there was no fissure between temporomandibular joint and temporal bone joint on intercuspal position and retruded contact position. While at mandibular postural position,there were fissures between maxillary teeth and mandibular teeth or between temporomandibular joint and temporal bone joint. Conclusions: The fragile areas of mandible are median symphysis, mental foramina, angle of mandible and neck of condylar process. There is no the correlation between mandibular fracture and the thickness of mandible. Under such conditions as impacted tooth, lacked tooth, mental foramina and fossa of mandibular canine, mandibular bone is debilitated. Tooth force orbit is beneficial to stress conduction through mandible. The site of mandibular fracture is changed by the contract of masticatory muscles and the difference of occlusions. Mandibular fracture is related with the fragile area of mandible, masticatory muscles and occlusions .