Abstract
Clinical observation was conducted on 208 fracture lines in 138 patients with fractures of the mandibula alone (except the fracture of the alveolar process) in which the situation at the time of infliction of the trauma and fracture lines was clearly established, to evaluate the mode of occurrence in fracture of the mandibula.
The cause of trauma consisted most frequently from accidents on motor cycles, followed by a fall and beating, therefore the intensity of the external force has been thought to be of medium degree in most of the cases.
In the cases, that had 2 or 3 fracture lines, the following tendences were evident. Infliction of external force on the midline portion was apt to cause a direct fracture of the midline portion and indirect fracture of the mandibular process. Infliction of external force on the mandibular angle frequently caused a direct fracture of a mandibular angle and indirect fracture of the anterior portion of the mandibula.
As to the relationship between the site of the infliction of external power and site of the fracture in the cause of mandibular process fracture, the shift of the site of impact from the lateral mental region, mandibular body and mandibular angle resulted in an increase in the number of the fracture lines in the contralateral side.
The mode of fracture in patients with an unstable condition of the mandible at the time of infliction of the trauma was in keeping with the results of experimental studies conducted on the fixation of the mandibular process that has already been reported. Therefore the weak portion of the mandibula appears to be reflected more simply in the case of the unstable mandible.
