Development of plate of osteosynthes for mandibular angle fracture with boné loss

Abstract

Despite the developments concerning the treatment of mandibular angle fractures, knowledge becomes limited when it comes to multiple fractures lines or loss of bone due to the lack of specific investigation in this field. Thus, the aim of this work is developing and evaluating a new design of internal fixation plate for the treatment of the complex mandibular fractures by the finite element method and mechanical testing. A three dimensional model of the fractured mandible was generated in Rhinocerus 4.0 software, and also was performed the modeling of the 2.0 mm system plates. The models have been exported to ANSYS ®, in which it was performed a static application of a force to generate displacement of 3 mm in the first molar region ipsilateral to the fracture. Three groups were evaluated according to the method of internal fixation: two plates of the 2.0 mm non-locking system, two plates of 2.0 mm locking system, and a plate with new design 2.0mm locking system. The computational model was transferred to an in vitro experiment with polyurethane mandibles with the same fixation groups and fracture pattern. Each group with five mandibles was subjected to linear loading test in a universal testing machine Instron Model 4411 to the displacement of 5 mm. A more balanced distribution of stress in the new plate design was observed. In addition, the new plate modified the mechanical behavior of the fractured region with a tendency to keep the approximate segments. However, the superiority of the reaction force of the group with two 2.0mm locking plates was observed (651.67 N). In the mechanical test the group with two locking plates showed greater resistance to the 3 mm displacement with statistically significant difference than the new plate group ( one-way ANOVA , F = 4.92 , p = 013) . A new plate for the treatment of mandibular angle fracture was developed, which, in the finite element analysis, showed a more balanced distribution of the stresses, however the group with two locking plates showed higher mechanical resistence. The new plate can replace two conventional plates without loss of mechanical resistence and with advantages of having the tendency to keep the fractured viii segments close when subjected to displacement and this use less material of internal fixation.