A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients.

PURPOSE: This study was an analysis of the soft and hard tissue changes of the facial profile after bilateral sagittal splitting osteotomy for mandibular setback of Taiwanese patients. PATIENTS AND METHODS: We collected pre- and postsurgical lateral cephalographs of 64 patients (28 males, 36 females) with skeletal Class III malocclusion who received combined orthodontic-surgical treatment with bilateral sagittal splitting osteotomy mandibular setback at Taipei Veterans General Hospital between 1994 and 2000. Nineteen cephalometric parameters of (14 linear, 4 angular, and the BS index) soft and hard tissues were measured at 1 week before treatment, and 2 months and 1 year after surgery, and analyzed by paired t test. RESULTS: Mean patient age was 20.0 +/- 1.6 years. The patients underwent an average of 7 mm mandibular setback at the osseous pogonion (Pog). Average setbacks at Pog and soft tissue pogonion (pog) were 5.54 mm and 4.85 mm, respectively, at 1 year after surgery. The setback ratio of Pog/pog was 1:0.88. The hard tissue relapse at Pog was 21% at 1 year after surgery. Improvement in prognathic profile was demonstrated by significant changes in the positions of Pog and pog, ANB angle, the distance from lower lip to esthetic line (E-L lip), and the BS index after surgery. However, compared with parameters obtained from a normal Taiwanese population, the cephalometric data of Pog, pog, and BS index still indicated mild prognathism. CONCLUSION: Although mandibular prognathism could be grossly improved by bilateral sagittal splitting osteotomy mandibular setback, a significant amount of relapse occurred within 1 year after surgery. The extent of the postoperatively preserved features showing mandibular prognathism should be a concern for both patients and physicians.     

Soft tissue assessment before and after mandibular advancement or setback surgery using three-dimensional images: systematic review and meta-analysis

The aim of this systematic review was to evaluate the effects of mandibular advancement or setback surgery on the facial soft tissue assessed using three-dimensional images. An electronic search was performed in the MEDLINE, Cochrane Library, Scopus, Virtual Health Library (VHL), Web of Science, and OpenGrey databases. Inclusion criteria comprised studies that evaluated the soft tissues of adult patients before and after mandibular advancement or setback surgery using computed tomography or magnetic resonance imaging. The risk of bias was analyzed. A total of 3501 studies were retrieved. The titles and abstracts of 2071 studies were read and 2040 of them were excluded. Thirty-one articles were read in full and six fulfilled the eligibility criteria and were included. A meta-analysis was performed using three of these articles. The correlation was significant and strong in the chin area (r = 0.876 and r = 0.868) and moderate for the lower lip/lower incisor (r = 0.690). The ratio for lower lip/infradentale was 78% and for Pog′/Pog was 98%. Due to the limited number of articles included, there is weak evidence to infer that changes in the facial soft tissue due to mandibular advancement or setback are significant, but changes in the lower lip tend to be smaller than changes in the chin area.     

Evaluation of post-surgical relapse after mandibular setback surgery with minimal orthodontic preparation

BackgroundThe aim of this study was to evaluate of the patterns of post-surgical relapse after mandibular setback surgery with minimal orthodontic preparation (MS-MO).Materials and methodsThe subjects consisted of 15 patients with minimal pre-surgical orthodontic preparation (1.37 ± 1.69 months). Lateral cephalograms were taken in pre-surgical (T0), post-surgical 1 month (T1) and immediately after debonding (T2) stages. To evaluate the surgical changes (T1–T0) and the relapse (T2–T1), the linear and angular measurements were analyzed using paired t-test. Pearson's correlation coefficients of the horizontal and vertical relapses of Pog and Me to other measurements were calculated. Pog or Me in T1 were displaced rotationally on Ar-Pog or Ar-Me lines in T2 to evaluate the remaining surgical relapse except the rotational relapse from total relapse.ResultsThe mandible relapsed anteriorly 3.53 mm (Pog) and 4.00 mm (Me) and superiorly 2.72 mm (Pog) and 2.44 mm (Me). FH to Ar-Pog and FH to Ar-Me decreased by about 2°. Pure surgical relapses at Pog and Me, except rotational relapses, were about 0.5 mm anteriorly and inferiorly 0.8 mm.ConclusionThe vertical relapse might induce mandibular rotation with the horizontal relapse. For an accurate prediction after MS-MO, the rotational relapse might be considered.     

Consideration of effect of the amount of mandibular setback on the submental region in the planning of orthodontic–orthognathic treatment

Aesthetic outcome has gained in importance in the treatment of patients with orthognathic problems. Historically, Class III malocclusions have historically been treated by isolated mandibular setback and maxillary advancement, whereas bimaxillary procedures have recently become the more common option. Functional outcome and stability have been discussed previously. The aim of this observational study was to evaluate the effect of mandibular setback (BSSO) on the cervical region. We studied 38 Class III patients (20 women and 18 men, mean (SD) age 25 (0.8) years) who we identified from our clinical records and who were treated between 1 January 2002 and 30 December2012 with mandibular setback procedures and followed up for 6 months. To study the effect of the amount of mandibular setback on the aesthetic outcome we have distinguished between patients with less than 5 mm setback and those with 5 mm or more. In patients whose mandibular setback was less than 5 mm there was no significant change in cervical length. However, it decreased significantly in patients in whom the movement was 5 mm or more. Postoperatively the lip–chin–throat angle (p = 0.02), the length of the lower lip (p = 0.002), and the length of the upper lip (p = 0.003) from the aesthetic line also differed significantly between the 2 groups. Our observations strongly suggest that all these relations should be considered when treatment is being planned to avoid an unpleasant aesthetic impact on the chin region.     

Relapse after SSRO for mandibular setback movement in relation to the amount of mandibular setback and intraoperative clockwise rotation of the proximal segment

The aim of this study was to evaluate the effect of the amount of setback movement and intraoperative clockwise rotation of the proximal segments on postoperative stability after orthognathic surgery to correct mandibular prognathism.Thirty-six patients with mandibular prognathism who underwent orthognathic surgery with bilateral sagittal split ramus osteotomy were evaluated. The amount of postoperative relapse was analyzed using a cephalometric analysis.Six months after surgery, the mean backward movement of the mandible at point B was 11.2 mm, the mean intraoperative clockwise rotation of the proximal segment was 4.3° and the amount of postoperative relapse at point B was 2.3 mm (20.3%) on average. The tendency of relapse did not significantly increase with the amount of setback but did increase significantly with the intraoperative clockwise rotation of the proximal segment.This study suggested that postoperative relapse after mandibular setback surgery might be more related to the degree of the intraoperative clockwise movement of the proximal segment, rather than the amount of setback movement. When the amount of mandibular setback is considerable, postoperative relapse might be minimized with adequate control of the intraoperative positioning of the proximal segments.     

Evaluation of soft tissue profile following intraoral ramus osteotomy in Chinese adults with mandibular prognathism

Twenty-five Chinese adults with mandibular prognathism were treated with either the intraoral vertical subcondylar osteotomy or the bilateral sagittal split ramus osteotomy. The patients were kept in maxillomandibular fixation for 6 to 8 weeks while osteosynthesis was achieved with the use of intraosseous wiring. Serial lateral cephalograms were taken presurgery and between 12 and 26 months postsurgery, and specific soft and hard tissue points were digitized on a computer. The mean mandibular setback postsurgically was 8.4 +/- 3.2 mm, with a 5.2-degree reduction in point A-nasion-point B angle. Posterior movement of pogonion, point B and the mandibular incisal edge was accompanied by posterior movement of 95% at soft tissue pogonion (r = .96), 89% at soft tissue point B (r = .83), and 67% at labrale inferius (r = .81), respectively. The correlation between changes in the labrale superius and mandibular setback appeared to be dependent on both the amount of mandibular setback and the degree of mandibular rotation during the setback surgery. The presently reported ratios of the soft tissue response to hard tissue movement vary from those reported in white patients by other researchers, which confirms the need for different ratios for different racial types.     

Gender differences in morphological and functional outcomes after mandibular setback surgery

Purpose

The aim of this study was to examine and compare morphological and functional outcomes after either isolated mandibular setback or bimaxillary surgery in males and females.

Soft-tissue changes associated with different surgical procedures for treating class III patients

Objective

The aim of this study was to evaluate the effects of different surgical procedures on soft tissue and skeletal changes.

Patients and methods

Pre- and postoperative lateral cephalograms of 191 class III patients aged 16–58 years were retrospectively analyzed and divided into three groups according to the surgical therapy they had undergone. Group I had undergone maxillary advancement (n=51), group II a bimaxillary (n=102) procedure, and group III mandibular setback (n=38). Cephalometric assessments were made at the beginning of orthodontic treatment (T1) and at least 8 weeks after surgical correction of the class III malocclusion (T2). Nasolabial angle and the distance between the lower lip and the esthetic line were evaluated as soft-tissue parameters, while the skeletal parameters included the SNA and SNB angles, Wits value, gonial angle, and relative position of the maxilla to mandible. Mean values and standard deviations were calculated and any significant difference between soft and hard tissue in association with surgery methods was determined applying the Wilcoxon test using SAS statistical software.

Results

Compared to mandible setback, the number of bimaxillary procedures and maxilla advancements has increased significantly in recent years (0.04). SNA values measured at T2 were an average of 84° in group I, 83° in group II, and 82° in group III, thus, revealing a tendency to return to the normal range. SNB values measured at T2 averaged 81° in group I, 80° in group II, and 81° in group III. We observed significant changes in the nasolabial angle according to the surgical approach taken (p=0.018). Changes in the distance between the lower lip and the esthetic line were only slightly significant (p=0.050). No significant differences were noted among the surgical approaches in terms of SNA and SNB angles.

Conclusion

The two groups that underwent advancement of the maxilla (groups I and II) revealed marked improvements in soft-tissue esthetics.     

双侧升支矢状劈开截骨后退下颌术后骨的稳定性的研究

目的：探讨双侧升支矢状劈开截骨术（BSSRO）后退下颌骨以钢丝结扎固定两骨段加颌间固定术后骨的稳定性，了解导致复发的有关因素。方法：双侧下颌升支矢状劈开截骨手术后退下颌的患者14例，于手术前1周，手术后1周，术后6个月分别拍摄定位头颅侧位片及许勒位X线片，用于测量下颌移动的距离及确定下颌骨髁状突的位置。结果：双侧下颌升支矢状劈开截骨后退术后，6个月的复发率为27.2%，多元逐步回归分析示下颌后退的距离与复发相关。结论：BSSRO后退下颌骨的距离越大，术后下颌骨向前移位的可能越大。     

The effect of mandibular setback or two-jaws surgery on pharyngeal airway among different genders

Cephalometric studies show significant gender differences in the size of the pharyngeal airway space. This study aimed to investigate and compare morphologic changes after mandibular setback or two-jaws surgery on the pharyngeal airway in men and women using computed tomography (CT). The sample included 34 women and 13 men diagnosed with Class III skeletal deformities, who had been treated by mandibular setback or bimaxillary surgery (maxillary advancement and mandibular setback). Anteroposterior, lateral and cross-sectional area dimensions of the airway, at the level of soft palate and base of tongue, were measured pre- and postoperatively on CT images. In the mandibular setback group, the anteroposterior and cross-sectional area of the pharyngeal airway at the level of the soft palate and base of tongue were significantly reduced for men or women (P < .05). In the two-jaws surgery group, only midsagittal anteroposterior dimensions at the same levels were significantly decreased for men or women (P < .05). The difference between any values measured between men and women who received bilateral sagittal split ramus osteotomy setback surgery or two-jaws surgery for the treatment of class III anteroposterior discrepancy were not statistically significant (P > .05). This study suggests that oropharyngeal airway measurements, important for airway patency, do not demonstrate sex dimorphism.     

Changes in overnight arterial oxygen saturation after mandibular setback

Mandibular setback reduces space in the pharyngeal airway, and it has been suggested that it might induce sleep-disordered breathing. We report on its effects on space in the pharyngeal airway and respiratory function during sleep. We studied 78 patients (29 men and 49 women) in whom skeletal class III malocclusions had been corrected. The mean (range) age at operation was 24 (16–38) years and body mass index (BMI) 21.4 (16.1–30 .9) kg/m². Morphological changes were evaluated on lateral cephalograms taken three times: preoperatively, a few days postoperatively, and more than 6 months postoperatively. Overnight arterial oxygen saturation (SpO₂) was measured by pulse oximetry 6 times: preoperatively, and on days 1, 3, 5, and 7, and 6 months postoperatively; oximetric indices were calculated. Those immediately after mandibular setback were significantly worse than those preoperatively, although they gradually improved. There were positive correlations between BMI and oximetric indices, and little association between changes in mandibular position and oximetric indices. There was no evidence of sleep-disordered breathing 6 months after mandibular setback because most patients adapt to the new environment for respiratory function during sleep. However, some (particularly obese) patients may develop sleep-disordered breathing just after mandibular setback. In such patients attention should be paid to respiratory function during sleep in the immediate postoperative period, and careful postoperative follow-up is needed.     

Effect of setback Le Fort I osteotomy on midfacial soft-tissue changes as evaluated by cone-beam computed tomography superimposition for cases of skeletal Class III malocclusion

This study employed the cone-beam computed tomography (CBCT) superimposition method to evaluate postoperative midfacial soft-tissue changes in cases of skeletal Class III malocclusion after double-jaw surgery with setback and vertical reduction Le Fort I osteotomy. A retrospective study was carried out on 15 patients who had undergone maxillary setback Le Fort I osteotomy and mandibular setback sagittal split ramus osteotomy with alar cinch suturing and V-Y soft-tissue closure. Three dimensional CBCT volume scans were recorded preoperatively (T0) and 6 months postoperatively (T1) to measure soft-tissue changes of the upper lip and midface. Post-surgery, soft-tissue landmarks in the cheek and paranasal areas had moved forward; the soft-tissue thickness at the A-point had markedly increased (P < 0.05); there was no significant change in the subnasale, and the midline of the soft-tissue of the upper-lip area had moved backward. The extent of the mean soft-tissue change at the labrale superius was greater than that at the other soft-tissue landmarks of the upper lip. The results suggest that maxillary setback movement of the maxilla by alar cinch suturing has a beneficial effect on paranasal soft-tissue and lip contours for patients with protrusive lip and acute nasolabial angle.     

Stability of hard tissue profile after mandibular setback in sagittal split osteotomies: a longitudinal and long-term follow-up study

The aim of the study was to conduct a long-term follow-up on the stability of the hard tissues after bilateral sagittal split osteotomy (BSSO) with rigid internal fixation (RIF)to set back the mandible and to compare it with that of mandibular advancement performed by the same team of surgeons and with the same examination protocol. Seventeen consecutive patients (6 females and 11 males) could be re-examined 12.7 years (T5) after surgery. The previous examinations were before surgery (T1), 5 days (T2), and 6.6 (T3) and 14.4 (T4) months after surgery. Lateral cephalograms were traced by hand, digitized, and evaluated with the Dentofacial Planner software program. The x-axis for the system of co-ordinates ran through sella (point zero) and the line nasion-sella-line minus 7 degrees. The program determined the x- and y-values of each variable and the usual angles and distances. The effects of treatment were determined with Wilcoxon matched pairs, signed ranks test, with Bonferroni adjustment, and the relationship between variables with Spearman rank correlation coefficient. Relapse at point B was 0.94 mm or 15 per cent and at pogonion 1.46 mm or 21 per cent of the initial setback at T5. Relapse was mainly short-term (T4-T2), 13 per cent for point B and 17 per cent for pogonion. Gender correlated significantly with relapse (T5-T2) at point B (P = 0.002) and pogonion (P = 0.021), i.e. females in contrast to males showed further distalization of the mandible instead of relapse. No correlations were seen for age or the amount of surgical setback. The long-term results in mandibular setback patients were more stable when compared with the mandibular advancement patients examined previously. The initial soft tissue profile, the initial growth direction, and the remodelling processes of the hard tissues must be considered as reasons for long-term relapse. Growth direction positively influenced the long-term results in females: further distalization of the mandible occurred.     

Facial changes in patients with skeletal class III deformity after bimaxillary surgery: an evaluation based on three-dimensional photographs registered with computed tomography

The objective of this study was to evaluate facial soft and hard tissue changes, individually and relative to each other, in patients with skeletal class III deformity after bimaxillary surgery using three-dimensional (3D) photos obtained by white light scanning. Thirty patients with skeletal class III deformity who underwent bimaxillary surgery were selected. Each patient underwent white light scanning and spiral computed tomography (CT) within two weeks before (T0) and six months after surgery (T1). The 3D photos were registered with CT soft tissue models for T0 and T1, and the skeletal area unaffected by treatment (cranial base) was used to register T0 and T1. Then, the 3D colour-coded map was analysed to assess both skeletal and soft tissue changes between T0 and T1. Changes in the 3D coordinates of each anatomical landmark were analysed using the Student’s t-test. Maxillary advancement by 2–3 mm and mandibular recession by 5–6 mm were observed; the mandible was shortened in the vertical direction. Compared with the preoperative values, the nasal columella was 0.51 mm shorter, the upper lip was 0.71 mm longer, the base of the alar cartilage was 1.38 mm wider, and the nasolabial angle became larger. The ratio of change in the position of soft tissue point Sn to hard tissue point A was 0.73:1, and that of soft tissue point Pg to hard tissue point Pog was 0.86:1. Images obtained by structured white light scanning registered with CT can be used as an alternative to study facial changes after orthognathic surgery.     

Soft tissue profile changes following mandibular advancement and setback surgery an average of 12 years postoperatively.

PURPOSE: The aim of this study was to assess long-term changes in position of soft tissue landmarks following mandibular advancement and setback surgery. MATERIALS AND METHODS: Twenty-seven patients (14 women, 13 men; mean age, 36 years) who had undergone either mandibular advancement (15 patients) or setback surgery (12 patients), were available for a long-term follow-up an average of 12 years postoperatively. In all of these cases, lateral cephalometric radiographs taken immediately before operation, at 1 week, 14 months, and 12 years postoperatively, were studied. RESULTS: During the 14 months postoperatively, soft tissue chin and mentolabial fold followed its underlying hard tissue in all patients. A continuous skeletal relapse was observable 12 years after mandibular advancement, but soft tissue chin moved more in an anterior direction. After mandibular setback, soft and hard tissue landmarks remained almost unchanged. Over the entire observation period, a thickening of soft tissue at pogonion was generally seen, and particularly a thickening of the whole chin in the setback group. All patients showed a significant lengthening and thinning of the upper lip. In all except 2 males, the patient's body weight increased markedly. CONCLUSION: In contrast to the immediate postoperative stage, soft tissue changes observed an average of 12 years after the primary operation do not directly follow the movements of the underlying skeletal structure. The soft tissue profile changes observed over such a long term seem to be influenced not only by the underlying skeletal structure but also by other factors such as weight gain and aging process.     

Soft tissue profile changes after vertical ramus osteotomy

Patients with mandibular prognathism have, for a number of years, been treated by orthognathic surgery and post-surgical changes in the facial profile have been widely reported. However, little is known about the influence of gender and age on the soft tissues. The aim of this study was to investigate changes in the soft tissue profile following orthognathic surgery and to evaluate gender and age differences in the ratios of soft-to-hard tissue change. Forty-two Caucasian adults (18 males and 24 females) aged from 17 to 46 years with mandibular prognathism who underwent vertical ramus osteotomy were included. Lateral cephalograms were taken 2-8 months pre- (T1) and 12-19 months post- (T2) surgically. Five skeletal, two dental, and seven soft tissue parameters were hand traced. Paired and unpaired Student's t-tests, Pearson's correlation coefficients, and multiple regression analyses were used to evaluate the data. Due to the setback of the mandible, soft and hard tissues changed in a 1:1 ratio at the mentolabial fold and chin in females and 1:1,1 in males. Significant differences of soft-to-hard tissue ratios were found at points Pg (P < 0.05) and Gn (P < 0.01). Age effects on the ratios were not significant. Other effects of the mandibular setback on the soft tissue profile were a significant increase in facial convexity, a deepening of the mentolabial fold, an increase in lower lip thickness, and a decrease in upper lip thickness, which increased the nasolabial angle. These findings indicate that use of gender-specific ratios in treatment planning might improve the accuracy of predicting treatment results.     

双侧升支矢状劈开截骨后退下颌术中去骨的评估研究

目的:评估双侧升支矢状劈开截骨后退下颌术中去除的颊侧骨皮质形状与垂直截骨线的方向和前牙覆变化间的关系,指导临床去骨操作。方法:在头影测量侧位描记图的下颌体部设计3种不同方向的垂直截骨线,用头影测量裁剪预测方法先旋转再后退下颌到术前设计位置,分析最终垂直截骨线与初始垂直截骨线间的角度关系,运用几何学原理计算此角度的大小。评价后退下颌时所需要去除骨皮质大致形状同初始垂直截骨线方向及前牙覆变化间的关系。结果:近心骨段不发生矢状向移位情况下,最终垂直截骨线与初始垂直截骨线间的角度大小与上下颌平面交角保持一致,与初始截骨线的方向和下颌后退的距离大小无关。去除的骨皮质形状与前牙覆变化相关。结论:近心骨段去骨形状与前牙覆变化密切相关,与截骨线方向和下颌后退的距离大小无明显相关。     

Effect of fixation method on intergonial width stability after mandibular setback via bilateral sagittal split osteotomy

Q4: Horizontal changes occur following bilateral sagittal split osteotomy (BSSO) in skeletal class III patients. The aim of this study was to assess the ostoperative changes in intergonial (IG) width and compare them between the positional screw and miniplate fixation methods in BSSO. This study evaluated patients who had mandibular prognathism and underwent BSSO for mandibular setback. Internal fixation was performed bilaterally, either with positional screws in the lateral ramus or with a miniplate. Postero-anterior cephalograms were obtained preoperatively (T1), at 1 month postoperative (T2), and at 6 months postoperative (T3). The IG widths and the alterations in IG width postoperative (T2 − T1, T3 − T2) were measured. No correlations were observed between the amount of setback and changes at T2  − T1 or T3 − T2. The IG width values decreased after mandibular setback and internal fixation with both methods. Statistical analyses showed a significant difference between T3 and T1 in the miniplate group (P = 0.045). No significant difference in the postoperative change in IG width (T2 − T1 and T3 − T2) was found between the two fixation groups. The magnitude of this change was smaller for positional screws when compared to miniplates for fixation. The amount of mandibular setback showed no correlation with postoperative changes in IG width..     

Midfacial soft-tissue changes after mandibular setback surgery with or without paranasal augmentation: Cone-beam computed tomography (CBCT) volume superimposition

The aim of this article is to compare the soft-tissue changes in the midfacial areas of patients who had undergone mandibular setback sagittal split ramus osteotomy (SSRO) with that of mandibular setback SSRO with paranasal augmentation. The subjects included 15 patients (group I), SSRO with paranasal augmentation and 20 patients (group II), SSRO alone. To evaluate the difference of the midfacial soft-tissue changes between groups, cone-beam computed tomography superimposition was utilized and the soft-tissue changes were measured both preoperatively and postoperatively by a 10 × 27 grid. In group I, the soft tissues were changed at the areas bounded superiorly by the infraorbital foramen, zygomatic eminence, posteriorly by the masseteric muscle and medially by the lateral aspect of the nose and following the nasolabial fold. In group II, the midfacial soft-tissue measurements were unchanged. This study may help clinicians to predict improvement in the midfacial region from mandibular setback SSRO with or without a paranasal augmentation procedure in class III deformities.     

Computational fluid dynamics for the assessment of upper airway changes in skeletal Class III patients treated with mandibular setback surgery

Objective:To analyze and compare pharyngeal airflow characteristics pre- and post–mandibular setback surgery in patients with Class III skeletal dysplasia using cone beam computed tomography (CBCT) and computational fluid dynamics (CFD).Materials and Methods:Records of 29 patients who had received orthodontic treatment along with mandibular setback surgery were obtained. CBCT scans were obtained at three time points: T1 (before surgery), T2 (average of 6 months after surgery), and T3 (average of 1 year after surgery). Digitized pharyngeal airway models were generated from these scans. CFD was used to simulate and characterize pharyngeal airflow.Results:Mean airway volume was significantly reduced from 35,490.324 mm³ at T1 to 24,387.369 mm³ at T2 and 25,069.459 mm³ at T3. Significant increase in mean negative pressure was noted from 3.110 Pa at T1 to 6.116 Pa at T2 and 6.295 Pa at T3. There was a statistically significant negative correlation between the change in airway volume and the change in pressure drop at both the T2 and T3 time points. There was a statistically significant negative correlation between the amount of mandibular setback and change in pressure drop at the T2 time point.Conclusions:Following mandibular setback surgery, pharyngeal airway volume was decreased and relative mean negative pressure was increased, implying an increased effort required from a patient for maintaining constant pharyngeal airflow. Thus, high-risk patients undergoing a large amount of mandibular setback surgery should be evaluated for obstructive sleep apnea and the proposed treatment plan be revised based on the risk for potential airway compromise.