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The increase in the pharyngeal airway space after mandibular advancement has not been well explained, and in this study we aimed to show whether there is a correlation in the increase of pharyngeal airway space as a consequence of the mandibular advancement or of the relative change between the mandibular position and the natural head position (NHP). Fifteen patients who had bilateral sagittal split osteotomy for mandibular advancement with or without genioplasty were studied retrospectively. The primary variables of mandibular position, NHP, and pharyngeal airway space were measured in three dimensions using preoperative and postoperative cone-beam computed tomographic datasets and were compared using the paired t test. The secondary variable of pharyngeal airway space was defined as the square root of the mean cross-sectional area (CSA 1/2 ) of the pharyngeal airway space. Pearson's correlation coefficient was used to find out whether there was a correlation between the change in CSA 1/2 and the change in mandibular position, or the relative change between the mandibular position and the NHP. Volumes and minimal cross-sectional areas were increased in the pharyngeal airway space, and lengths of airways decreased. Correlation existed only between the increase in CSA 1/2 and the relative change between the mandibular position and NHP. The increase in pharyngeal airway space after mandibular advancement correlated with the relative changes between the mandibular position and the NHP., (Copyright © 2019 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Our aim was to assess the accuracy of computer-aided orthognathic surgery for maxillary repositioning in 15 patients with mandibular hyperplasia and normal temporomandibular joints (TMJ). We aligned preoperative and postoperative virtual skulls at the cranium using surface superimposition then recorded and calibrated three 3-dimensional coordinates (maxillary dental landmarks U0, 6R, and 6L) on the skulls. Errors between these preoperative and postoperative landmarks were calculated and the largest error of every patient was chosen for assessment. Landmark errors ranged from 1.00 - 2.49mm, and recording errors from -0.06 - 0.07mm. The superimposition error was mean (SD) 0.036 (0.002)mm. The accuracy of the method is acceptable in patients with a normal TMJ., (Copyright © 2017. Published by Elsevier Ltd.)

We investigated the change in the natural head position and its relation to the change in the mandibular position in patients with mandibular hypoplasia. Forty-one patients treated by orthognathic surgery were divided into three groups: bilateral sagittal split osteotomy (BSSO) advancement (n=8); BSSO advancement with genioplasty (n=12), and Le Fort I osteotomy with BSSO advancement (n=21). Cone-beam computed tomographic (CT) datasets were collected preoperatively and six weeks postoperatively. The natural head position was measured using the craniocervical angle and the distance from the second vertebra to the frontal plane, and the mandibular position was measured using the craniomandibular angle and the distance from the mandible to the frontal plane. Repeated measures two way ANOVA was used to assess the significance of differences between the angular and linear measurements, and Pearson's correlation coefficient to assess those between the change in the mandibular position and the natural head position. The craniomandibular angle increased and the mandible to frontal plane distance decreased, as planned; the craniocervical angle increased, and the distance from the second vertebra to the frontal plane decreased in all three groups. ANOVA showed a significant difference in the time factor (preoperative compared with postoperative) but no significant differences between the groups or interaction (time multiplied by group) factors. There was a significant correlation between the change in mandibular position and the change in the natural head position. Changes in the natural head position after correction of mandibular hypoplasia are correlated with the change in the mandibular position, regardless of whether a genioplasty or Le Fort I osteotomy was done., (Copyright © 2017 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Our aim was to investigate the potential effect of advancement by bilateral sagittal split osteotomy (BSSO) on the natural position of the head by using 3-dimensional cephalomentric analysis. Seven consecutive patients who had had only BSSO advancement, and had had preoperative and 6-week postoperative cone beam computed tomography (CT) scans, were recruited to this retrospective study. Two variables, SNB and SNC2, were used to indicate the craniomandibular alignment and craniocervical inclination, respectively, in the midsagittal plane. Using 3-dimensional cephalometric analysis software, the SNB and the SNC2 were recorded in volume and measured in the midsagittal plane at 3 independent time-points. The reliability was measured and a paired t test used to assess the significance of differences between the means of SNB and SNC2 before and after operation. The 3-dimensional cephalometric measurement showed good reliability. The SNB was increased as planned in all the mandibles that were advanced, the cervical vertebrae were brought forward after BSSO, and the SNC2 was significantly increased in 6 of the 7 patients. Three-dimensional cephalometric analysis may provide an alternative way of assessing cephalometrics. After BSSO advancement, the natural position of the head changed by increasing the craniocervical inclination in an anteroposterior direction., (Copyright © 2012 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

We investigated the feasibility of using an internal bidirectional mandibular distractor to elongate the mandibular bodies and rami of 4 mature male goats. An osteotomy was made at the right mandibular angle and the distractor placed within the osteotomy and allowed to heal in place for 5 days. The mandibles were simultaneously distracted vertically and horizontally at a rate of 0.5mm/day for 30 days. After a 12-week consolidation period, all the goats were killed for gross, radiographic, and histological evaluation. Smooth new bone had been restored in the distracted area after 12 weeks' consolidation, and the gross, radiographic, and histological evaluations showed that the new bone was similar to the native bone. These results suggest that the internal bidirectional distractor could permit bidirectional distraction osteogenesis in a goat model., (Copyright © 2011 The British Association of Oral and Maxillofacial Surgeons. All rights reserved.)

We have investigated the feasibility of using a new curvilinear distractor to repair mandibular defects in 6 mature male dogs. A mandibular defect was created by an oblique osteotomy between the distal planes of the bilateral second premolars, and a transport disc 10mm wide was made. After a 7-day latency period, distraction was activated at 0.5mm/12h and consolidation lasted for 6 or 12 weeks. Three dogs were killed after 6 and 12 weeks' consolidation for gross, radiographic, and histological observations to be made. Curvilinear distraction osteogenesis was successful in 5/6 animals. At both time points smooth curved bone had been restored in the distracted areas, and radiographic and histological examination showed that the generated bone was similar to normal bone after 12 weeks' consolidation. These results suggest that the curvilinear distractor could complete curvilinear distraction osteogenesis in dogs' mandibles., (Copyright © 2011 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)