A clinical analysis of 131 mandibular fracture cases

Objectives: Through the analysis of the single fracture in 131 mandibles, this study was aimed to discuss the displacement model of the mandible fracture and it biomechanical principles. Methods: In this study, 131 cases of single mandibular fracture (male:86, female: 56) were reviewed. The anterior and posterior fragmentary parts and 6 directions of the fragmentary displacement were defined. We regarded the anterior fragmentary part and superior board of the mandible as frame of the reference to evaluate the displacement of the fractured fragment. Results: The position of the fractures were located at angle, posterior body, anterior body, mental foramen, and symphysis with 35, 17, 15, 23, 41 cases ,respectively. The lingual-buccal displacements were observed in 96 cases, caudal-cranial in 75 cases, and compression-tension in 42 cases. Conclusions: The fracture of the mandible results from three kinds of forces, blend movement, torsion movement and shear force. The directions of these forces varied and caused various displacements. These three forces resulted in compression-tension, lingual-buccal and caudal-cranial displacement. The effect of the shear force was obvious at angle and posterior body fractures, while the effect of torsion movement was the most obvious at symphysis and mental foramen fractures.