Evaluation of inter-maxillary fixation techniques for multi-piece Le Fort I osteotomies using finite element analysis

A strong postoperative occlusal relationship is essential for the long-term stability of the jaw relations post orthognathic surgery. In multi-piece Le Fort I osteotomy, obtaining a satisfactory inter-maxillary fixation (IMF) of the mobilized segments in the correct position and according to the preoperative plan is difficult. Herein, we aimed to evaluate three different IMF techniques (tooth-supported, bone-supported, or hybrid IMF) using finite element analysis (FEA) of the occlusal surfaces of four models: three multi-piece (lateral incisor-canine, central incisor-central incisor, and canine-first premolar) and a single one-piece Le Fort I osteotomy scenario.

Three different IMF techniques were applied separately to three different multi-piece models and a single one-piece Le Fort I model designed using related software. Simulation brought the lower and upper jaw models to the planned occlusion. Each model's occlusal force was applied to determine their distributions under 100 N, 300 N, and 800 N loads. Forces on the maxilla and mandible during fixation, the effect of these forces on the force distribution in the occlusion, and the accumulated stresses in these regions were determined with Algor Fempro and Rhinoceros software to determine the ideal fixation method. Data obtained were interpreted and evaluated according to the advantages and disadvantages of the actual surgical scenario.

In all four models studied, the hybrid IMF technique was found to be the ideal IMF technique, followed by the teeth- and bone-supported IMF techniques.

FEA allows the manipulation of single parameters, which clinical methods cannot obtain, thereby allowing each to be examined separately. Further clinical trials are required to validate these findings.