Maxillary stability in patients with skeletal class III malocclusion treated by bimaxillary orthognathic surgery: comparison of mandible-first and maxilla-first approaches in a randomised controlled study

Abstract

The maxilla-first approach has been the standard orthognathic sequence for many years, however, with the evolution of rigid internal fixation and to eliminate any errors that could be encountered during preoperative bite registration, the mandible-first approach has become an effective treatment modality for bimaxillary orthognathic surgery. Would the maxilla-first or mandible-first orthognathic sequence in bimaxillary orthognathic surgery result in more maxillary stability in patients with skeletal class III malocclusion? Twenty-four patients with skeletal class III malocclusion were selected from the outpatient clinic of the Oral and Maxillofacial Surgery Department, Faculty of Dentistry, Cairo University. Patients were randomly divided into two equal-sized groups: the maxilla-first approach (group I), and the mandible-first approach (group II). All patients underwent cone-beam computed tomography before, immediately after (P1), and 6months after surgery (P2). Virtual planning included designing the virtual cuts and the intermediate and final splints. Both splints were three-dimensionally printed. In both approaches, hard and soft tissue landmarks were used as reference points to evaluate maxillary stability, which was calculated by subtracting P2 values from P1 values. All measures were statistically evaluated as numerical values of means and standard deviations. The differences between the radiographic measurements of the two groups were not statistically significant except for the soft tissue inclination at the nasal tip. The mandible-first approach in bimaxillary orthognathic surgery is a reliable method for achieving high maxillary stability.