Postoperative nausea and vomiting after oral and maxillofacial surgery: a prospective study

Postoperative nausea and vomiting (PONV) is one of the most unpleasant experiences after surgery. It reduces patient satisfaction and also increases hospital costs due to longer hospitalizations. The aim of this prospective study was to determine whether orthognathic surgery is associated with more PONV than less invasive maxillofacial surgery. Three hundred and eight patients aged 8–87 years who underwent maxillofacial surgery were included. The PONV score, based on the Apfel score, was calculated preoperatively. PONV occurred in 142 (46.1%) patients during the first three postoperative days; these patients were further categorized as having postoperative nausea (PON) and/or postoperative vomiting (POV). PON was most frequent after orthognathic surgery to the mandible (75%), and POV was most frequent after maxillary surgery, including bimaxillary surgery, Le Fort I osteotomy, and surgically assisted rapid palatal expansion (SARPE) (43.1%). There was a small significant relationship between the preoperative PONV score and the incidence of PONV: patients experienced more PONV when the PONV score calculated preoperatively was higher. The incidence of PONV after orthognathic surgery was very high compared with the incidence after dental extractions and other minor surgeries. Further investigation is required to establish a strategy to reduce PONV after orthognathic surgery.     

Nitrous oxide does not aggravate postoperative emesis after orthognathic surgery in female and nonsmoking patients.

PURPOSE: The purpose of this study was to evaluate the effect of supplemental nitrous oxide on postoperative nausea and vomiting (PONV) after propofol anesthesia for orthognathic surgery in female and nonsmoking patients. PATIENTS AND METHODS: We compared PONV in 28 ASA-I female nonsmoking patients undergoing orthognathic surgery. Anesthesia was induced with propofol combined with fentanyl, and tracheal intubation was facilitated with vecuronium. Anesthesia was maintained with propofol with or without nitrous oxide. No patient received neostigmine. PONV was assessed as score 0 (no PONV), score 1 (nausea), and score 2 (vomiting) during the 24-hour recovery period. RESULTS: There were no differences in the patients' characteristics, operation, anesthesia and emergence time, fluid transfusion, blood loss, urine output, and total propofol and fentanyl doses between the 2 groups. There was also no difference in PONV score in 2 groups. Only 1 patient in each group vomited. CONCLUSIONS: It is suggested that supplemental nitrous oxide does not aggravate PONV after propofol anesthesia for orthognathic surgery in female nonsmoking patients.     

Effect of chlorhexidine/benzydamine soaked pharyngeal packing on throat pain and postoperative nausea & vomiting in orthognathic surgery

Pharyngeal packing is believed to reduce postoperative nausea and vomiting (PONV) frequency, but has the disadvantage of causing throat pain. The present study aimed to investigate whether applying pharyngeal packs soaked with a combination of chlorhexidine gluconate 0.2% and benzydamine hydrochloride 0.15% (CGBH) were effective in preventing postoperative throat pain and PONV in patients undergoing orthognathic surgery. A total of 101 patients scheduled for orthognathic surgery were enrolled in this prospective, double-blind, randomized study. Patients were randomly allocated into two groups: those with CGBH-soaked packing, and those with saline-soaked pharyngeal packing. PONV was recorded using a 5-point Likert scale (0: no PONV to 4: severe PONV) immediately after the surgery at 5, 10, and 30 min, and at 2, 4, 6, 12, and 24 h postoperatively. The severity of throat pain was assessed via two methods: visual analogue scale (VAS, 0: no pain, 10: severe pain) and 6-point Likert scale (0: no pain, 5: strongly severe pain) score at 2, 4, 6, 12, and 24 h postoperatively. Mean VAS scores of throat pain were significantly lower in patients receiving CGBH-soaked pharyngeal packs compared to patients receiving saline-soaked pharyngeal packs, at all measured time points. There was a tendency towards less PONV in patients receiving a CGBH-soaked pharyngeal pack compared to those receiving a saline-soaked pharyngeal pack; however, this difference did not reach statistical significance. The results of this study suggest that the usage of CGBH-soaked pharyngeal packs reduce postoperative throat pain in patients undergoing orthognathic surgery. Our results support the implementation of CGBH-soaked pharyngeal packing in orthognathic surgery practice, as a measure to improve patient comfort.     

Predicting postoperative nausea and vomiting in patients undergoing oral and maxillofacial surgery

A common predictive measure of postoperative nausea and vomiting (PONV) is the Apfel score. Although tested in many different operations, it has not been tested extensively in oral and maxillofacial surgery (OMFS). This study was designed to determine whether it applied to OMFS and whether there were other factors in this population that would improve its accuracy. A retrospective chart review was carried out on a randomly selected group of patients who had OMFS during a 10-month period. In addition to the Apfel score risk factors, PONV data were collected in relation to type of anesthetic induction and maintenance, type of surgery, use of maxillomandibular fixation (MMF), use of opioids, and anesthesia and surgery times. One-hundred and sixty-seven patients were included in the analysis; 24% had nausea and 11% had nausea and vomiting. Patients who had orthognathic or temporomandibular joint surgery had the highest rate of PONV. Young age, anesthesia and operation time, and use of MMF were also associated with increased PONV. Adding age, MMF or limited postoperative mouth opening, and surgery type to the Apfel score should make it more predictive in OMFS.     

Prevalence of nasolacrimal canal obstruction and epiphora following maxillary orthognathic surgery

Acquired injuries of the nasolacrimal apparatus may be the result of craniomaxillofacial surgical procedures, facial trauma, or inflammation. Injury to the nasolacrimal duct system following maxillary orthognathic surgery is rarely reported. This study evaluated the importance of early diagnosis and treatment of epiphora developing after Le Fort I surgery. The records of 83 patients who underwent maxillary orthognathic surgery over a 2-year period were reviewed. The prevalence of postoperative epiphora was 3.6% and it persisted for a mean of 32.7 days. No patient required further surgical treatment of the nasolacrimal duct obstruction. Clinicians should evaluate the lacrimal canal position and schedule close postoperative follow-up of injuries to the nasolacrimal apparatus. These may become permanent, necessitating additional surgery.     

Effect of orthognathic surgery on the temporomandibular joint in patients with anterior open bite

This study examined the prevalence of temporomandibular joint (TMJ) signs and symptoms in patients with anterior open bite. The influence of orthognathic surgery on the TMJ in these patients and the interaction of occlusal and psychologic variables on the presence and/or persistence of pain was studied. A retrospective survey of 83 patients with an anterior open bite who underwent orthognathic surgery was carried out. Records were examined for the prevalence of abnormal TMJ signs and symptoms, including pain. A survey was mailed to these patients that consisted of: (1) the TMJ Scale, (2) the Symptom Checklist 90 (SCL90), (3) the Spielberger State-Trait Anxiety Inventory (STAI), and (4) a visual analog scale on which patients indicated their degree of satisfaction with the procedure. Thirty-seven (42%) patients responded to the survey, and 13 (15%) also attended a clinical and radiographic examination. Multiple regression analysis was used for statistical analysis of the factors contributing to the presence and/or persistence of pain. In the preoperative group, the prevalence of pain was 32%, dysfunction 40%, and limitation of opening 7%. Age and gender were significantly associated with the presence of pain. The overall prevalence of abnormal TMJ signs and symptoms was not significantly different after orthognathic surgery. An abnormal psychologic profile was the most significant factor associated with the presence and/or persistence of pain. It is concluded that that the prevalence of temporomandibular disorders in anterior open bite patients increases with age, is significantly higher in females, and is not influenced by other occlusal variables. Furthermore, orthognathic surgery does not significantly influence temporomandibular disorders in patients with anterior open bite. Female patients, particularly those with an abnormal psychologic profile, are at a higher risk of persistent postoperative TMJ pain.     

The assessment of blood loss in orthognathic surgery for prognathia.

PURPOSE: It is difficult to predict the need for blood transfusion during orthognathic surgery. The purpose of this study was to evaluate differences between patients who underwent different orthognathic procedures, and to assess the need for transfusion in orthognathic surgery. SUBJECTS AND METHODS: We examined 62 prognathic patients who underwent orthognathic surgery in our hospital. The subjects were divided into 4 groups according to procedure. Pre- and postoperative values of blood parameters were evaluated statistically. RESULTS: A greater amount of blood was lost in the double-jaw surgeries than in the single-jaw surgeries. There was a significant difference between sagittal split ramus osteotomy (SSRO) combined with Le Fort I osteotomy and intraoral vertical ramus osteotomy (IVRO) ( P < .05). However, none of the patients required transfusion intraoperatively. In all groups except the IVRO group, there were significant differences in red blood cell count, hemoglobin, and hematocrit between preoperative values and 1 week postoperative values ( P < .05). Although the values of red blood cell, hemoglobin, and hematocrit tended to decrease until 2 weeks postoperative, no complications occurred. Simple regression analysis showed significant positive correlation between duration of operation and blood loss ( P < .05). CONCLUSION: The present results indicate that there is little risk of marked bleeding in routine procedures, and that IVRO causes minimal bleeding. Transfusion was not necessary in IVRO or SSRO with or without Le Fort I osteotomy.     

The predictability of inferior medial canthus as a stable external vertical reference point in maxillary repositioning surgery

The purpose of this study was to investigate the predictability of using the inferior medial canthus as a stable external reference point for establishment of the vertical dimension in maxillary orthognathic surgery. Ten consecutive patients with skeletal Class II malocclusion and open bite who underwent orthognathic reconstructive surgery were included in the study. Prediction tracings were completed preoperatively and superimposed on an immediate postoperative lateral cephalometric radiograph. In 7 patients, the vertical positioning of the maxillary incisal edge on the immediate postoperative lateral cephalometric radiograph showed no difference from the superimposed preoperative prediction tracing. One patient showed 1 mm difference and 2 patients showed 2 mm difference from the preoperative prediction tracings. All cases resulted in acceptable maxillary incisal exposure relative to upper lip stomion. It is concluded that the inferior medial canthus can be used as a reproducible external vertical reference for orthognathic surgery when the technique described herein is used.     

The Early Psychological Adjustment of Cleft Patients After Maxillary Distraction Osteogenesis and Conventional Orthognathic Surgery: A Preliminary Study

PURPOSE: To compare the early psychological changes of cleft lip and palate (CLP) and noncleft patients after maxillofacial corrective surgery, including maxillary distraction osteogenesis and conventional orthognathic surgery. MATERIALS AND METHODS: Nine CLP patients were compared with a group of 9 non-CLP patients having similar dentofacial deformities in a prospective longitudinal cohort study. Five of the CLP patients underwent maxillary distraction osteogenesis and 4 underwent conventional orthognathic surgery. A control group of 9 noncleft patients received conventional orthognathic surgery. All patients completed a set of questionnaires to enable their psychological profile to be assessed. The data were collected immediately before surgery (T1), and at 3 weeks (T2) and 12 weeks (T3) after surgery. RESULTS: The CLP patients treated with distraction osteogenesis were happier, but had a higher level of social anxiety and distress than the CLP patients receiving conventional orthognathic surgery. On the other hand, the CLP patients overall were happier, with lower social anxiety and distress, than the noncleft control group. The CLP patients showed a higher level of parental self-esteem than the noncleft patients. CONCLUSION: This preliminary study shows that CLP patients were generally happier, and had a higher level of parental support, than normal patients suffering from dentofacial deformities. Maxillary distraction osteogenesis seemed to induce a higher level of anxiety and distress in CLP patients than conventional orthognathic surgery in both cleft and noncleft patients.     

Combining single- and double-tooth osteotomies with traditional orthognathic surgery

Combining large-segment orthognathic surgery and unitooth or small-segment surgery is an effective approach to deal with a wide range of dentofacial deformities that have minor to severe occlusal problems. The indications for combining single- or double-tooth osteotomies with traditional orthognathic surgery were patients with dentofacial deformities and malocclusion requiring stable correction within a short overall treatment period. From 1991 to 1998, a total of 36 patients underwent combination single- or double-tooth-segment osteotomy with traditional orthognathic procedures performed at Chang Gung Memorial Hospital. The indications for surgery were maxillary protrusion (N = 5), bimaxillary protrusion (N = 19), mandibular prognathism with maxillary protrusion (N = 11), and noncleft maxillary retrusion (N = 1). The types of osteotomies performed were the Le Fort I, the anterior segmental osteotomies of the maxilla or the mandible, the palatal split, and the posterior segment in combination with single-tooth or double-tooth segments. Follow-up ranged from 12 months to 6 years and showed stability in the movements with no complications. There was no loss of any "osteotomized" segment. The average overall treatment time was approximately 18 months--5 months preoperative and 13 months postoperative orthodontic treatment. This was at least 6 months shorter in duration compared with traditional orthognathic surgery. Combining traditional orthognathic surgery with single- or double-tooth segments allows us to treat complex dentofacial deformities in the vertical, transverse, and sagittal dimensions with differential repositioning of all segments, either major or minor, simultaneously. The authors' experience with 36 consecutive patients evidence good results and demonstrate the procedure to be safe with minimal complications.     

Do oropharyngeal throat packs prevent fluid ingestion during orthognathic surgery?

The oropharyngeal throat pack is commonly used in oral and maxillofacial surgery despite debated evidence regarding its barrier function. The study objectives were to investigate whether the oropharyngeal pack reduces blood ingestion and to evaluate its relationship with postoperative nausea and vomiting (PONV) and throat pain. This was a single-center, parallel group, single-blind randomized controlled trial. Participants undergoing orthognathic surgery, age ≥16 years, were included in the study. After intubation and prior to surgery start, the treatment group received oropharyngeal packing; the control group received no packing. Outcome variables were the quality of gastric contents aspirated by nasogastric tube (bloody or not bloody), PONV, and throat pain (visual analog scale). Thirty patients (treatment n = 15; control n = 15) were randomized and analyzed. There was no difference between the groups in quality of gastric contents (P = 1.00) or incidence of PONV at 2 hours and 24 hours (P = 1.00). Throat pain incidence and severity at 2 hours were both higher in the treatment group, but this was not statistically significant (P = 0.128, P = 0.223). The results indicate that the oropharyngeal pack is not an effective barrier against blood ingestion. Oropharyngeal packs do not improve or worsen PONV, but may increase throat pain.     

Prevalence of postoperative complications after orthognathic surgery: a 15-year review.

PURPOSE: This study was conducted to determine the prevalence of postoperative complications after orthognathic surgery and evaluate the use of antibiotic prophylaxis in relation to the infection rate. PATIENTS AND METHODS: All patients undergoing orthognathic procedures between 1990 and 2004 were studied retrospectively by retrieving their individual medical records. Demographic data, intraoperative data (specific orthognathic procedures and duration of operation), and postoperative data (type and duration of antibiotic prophylaxis and presence of postoperative complications) were recorded. Patients noted to have suffered any postoperative complications were studied in detail, and various factors, including gender, age, duration of operation, and use of prophylactic antibiotics, were analyzed using statistical tests in relation to postoperative infection. RESULTS: A total of 2,910 orthognathic procedures were performed on 1,294 consecutive patients in the 15-year period, with 1,070 patients undergoing bimaxillary procedures and 224 patients undergoing single-jaw surgery. The orthognathic surgery-related complication rate was 9.7%, of which 7.4% was related to postoperative infection. Of the cases of infection, 58.3% were acute infection and 41.7% were chronic infection. Patients who received a single preoperative dose of antibiotics had a significantly higher infection rate (17.3%) than those who received postoperative antibiotics for various durations. CONCLUSIONS: The prevalence of infection after orthognathic surgery was relatively low given the complexity of the procedures. No particular orthognathic procedure was more susceptible to infection. A preoperative dose of prophylactic antibiotics together with at least 2 days of postoperative doses was useful in reducing the infection rate compared with only a single dose of prophylactic antibiotics.     

Three-dimensional alterations in pharyngeal airspace,soft palate,and hyoid bone of class II and class III patients submitted to bimaxillary orthognathic surgery: A retrospective study

IntroductionThe aim of this retrospective study was to evaluate changes in pharyngeal airway space (PAS), soft palate, and hyoid bone position after bimaxillary orthognathic surgery in skeletal Class II and Class III patients.MethodsPatients were divided into Group 1: Class III patients who underwent maxillary osteotomies and mandibular setback surgery (N = 43); and Group 2: Class II patients who underwent maxillomandibular advancement surgery (N = 36). Cone beam computed tomography (CBCT) images were acquired one month before and six to eight months after orthognathic surgery. PAS area, volume and minimum axial area (MAA), soft-palate morphology, and hyoid bone position measurements obtained before and after orthognathic surgery were compared using the Gamma family test (p ≤ 0.10).ResultsIn Class II group the maxillomandibular advancement surgery significantly increased the PAS area, volume, and MAA and significantly affected hyoid bone position and soft-palate morphology. In Class III group, maxillary osteotomies and mandibular setback also showed increase in PAS area, however without statistically significant values for most of the evaluated measurements.ConclusionThe results of the present study indicate that PAS and related structures are expected to be improved in Class II patients submitted to bimaxillary surgery, and they are not negatively affected by bimaxillary surgery in Class III patients.     

Comparison of the effect of 2 hypotensive anesthetic techniques on early recovery complications after orthognathic surgery

The aim of this study was to evaluate the recovery complications following the use of 2 anesthetic protocols in orthognathic surgery, namely, propofol with remifentanil and isoflurane with remifentanil. Sixty-two patients with American Society of Anesthesiologists physical status I were selected. All underwent bimaxillary orthognathic surgery. Propofol with remifentanil was used as an anesthesia in group 1 (n = 32), and isoflurane with remifentanil was used in the patients in group 2 (n = 30). Early recovery complications consisting of pain, postoperative nausea and vomiting (PONV), shivering, and agitation were evaluated and documented. The length of the operation and duration of recovery were documented for all patients. Analysis of the data demonstrated no relationship between age and recovery time (P > 0.05). Analysis of data with χ(2) and independent t-tests did not show any difference between the 2 groups with regard to pain, agitation, PONV, and shivering (P > 0.05). Logistic regression was used to evaluate the effect of the operation time on recovery complications. The analysis showed that pain and PONV were significantly higher in those who experienced a longer operation time. With increasing operation time longer than 165 minutes, 64% of patients experienced pain, and 89% of them had PONV. General anesthesia can be provided via intravenously administered medications and/or inhaled volatile anesthetics. No significant difference in early recovery time was found in patients when either isoflurane or propofol was used to maintain the anesthesia. However, the length of the operation played a major role in increasing early recovery complications.     

Complications and failures in orthognathic surgery

This paper reviews the literature about the most relevant complications in daily orthognathic surgery. Although orthognathic surgery has proven to be relatively safe, patients who undergo such maxillofacial orthopaedic surgery must be aware of the side effects of this combined treatment. Immediate life-threatening complications are very rare. They can in most cases be avoided by good anaesthetic and surgical techniques and adequate postoperative care. The most frequently encountered perioperative problem in maxillary surgery is excessive blood loss, whilst subjective neurosensory disturbance is the most frequent complication in mandibular surgery. Good co-operation between orthodontist and surgeon is essential to prevent most immediate and late postoperative problems and nearly all unsatisfactory results.     

The validity of a computer-assisted simulation system for orthognathic surgery (CASSOS) for planning the surgical correction of class III skeletal deformities: single-jaw versus bimaxillary surgery

The aim of this study was to assess the accuracy of the two-dimensional profile prediction produced by the computer-assisted simulation system for orthognathic surgery (CASSOS), for the correction of class III facial deformities. Correction was by maxillary advancement (n=17) or bimaxillary surgery (n=16). The mean age was 24 years (range 18-42). The surgical and dental movements obtained from the postoperative cephalogram were used to produce a CASSOS profile prediction, which was compared with the soft-tissue profile. The prediction was superimposed onto the postoperative radiograph, and a coordinate system was used to measure linear differences. For the maxillary advancement group there were statistical differences for three horizontal landmarks: superior labial sulcus (p=0.017), labrale superious (p=0.038) and labiomental fold (p=0.014). In the bimaxillary group only the landmark vertical labrale superious (p=0.002) showed a statistical difference. Generally, CASSOS produced useful profile predictions for maxillary advancement surgery or bimaxillary surgery for Class III patients, although there was considerable individual variation. The main areas of inaccuracy were the lips. The major difference between the two types of surgery was that most of the errors in the maxillary surgery group were in the horizontal direction, whilst for the bimaxillary surgery the errors were mainly in the vertical direction.     

上颌前突患者头影测量的配对统计学测量研究

目的：应用配对统计学测量方法通过对比单纯正颌治疗和正畸-正颌联合治疗上颌前突畸形的疗效,明确正颌治疗和正畸治疗的疗效及相互关系。方法：36例恒牙期骨性上颌前突病例,根据上颌前突程度两两配对,分配于A,B两组;A组上颌前突患者只接受正颌治疗,B组患者接受正畸-正颌联合治疗。结果：两组患者的上颌前突畸形均较术前有很大的改善（P〈0．05）,B组术后能获得较好的疗效及较好的稳定性（P〈0．05）。结论：应用正颌和正畸一正颌联合治疗上颌前突均能取得良好的面型改善,正颌术前术后正畸治疗可以对疗效及术后稳定性有良性的促进作用。     

Effect of methylprednisolone on swelling after orthognathic surgery

The effectiveness of methylprednisolone for the reduction of postoperative facial edema was evaluated by the computed tomographic examination of 39 patients who underwent either a Lefort I osteotomy or a transoral vertical osteotomy. Results of the CT scans, which were performed preoperatively and at 24 and 72 hours postoperatively, showed that in the LeFort I osteotomy patients methylprednisolone reduced the degree of facial edema by 61% at 24 hours postoperatively and by 10% at 72 hours. In the transoral vertical osteotomy patients methylprednisolone reduced the degree of facial edema by 38% at 24 hours postoperatively and by 45% at 72 hours. It was concluded that methylprednisolone is effective for the control and management of postoperative facial edema following orthognathic surgery.     

Risk factors for nausea and vomiting after day care general anesthesia in mentally challenged patients undergoing dental treatment

Clinically, the incidence of postoperative nausea and vomiting (PONV) may be higher in mentally challenged patients than in normal healthy patients. The aim of this study was to investigate the risk factors for PONV after day care general anesthesia in mentally challenged patients undergoing dental treatment. We analyzed data on 231 day care general anesthesia cases involving mentally challenged patients undergoing dental treatment. Anesthetic records for the past 5 years were investigated retrospectively. Ten items (age, body weight, sex, duration of general anesthesia, use of propofol, use of sevoflurane, use of nitrous oxide, use of neostigmine, treatment accompanied with bleeding, and transfusion volume) were selected as risk factors for PONV. Postoperative nausea and vomiting was evaluated using the postoperative check sheet and linear discriminant analysis was performed to distinguish PONV incidence using the 10 items as independent variables. The reliability of the linear discriminant function was evaluated using a misjudgment rate and information criteria (AIC). Postoperative nausea and vomiting was observed in 13 cases out of 231 cases. The discriminant function with the smallest AIC (-25.0718) consisted of two independent variables: y=-0.077x(1)-0.001x(2)+0.0716(x(1)=use of propofol, x(2)=age). The misjudgment rate was 31.6%. This result suggests that PONV decreases when propofol is used and that the incidence of PONV decreases with age. To investigate other risk factors, an additional analysis was performed using 83 out of the 231 cases in which sevoflurane was used as an anesthetic agent. The results of the subgroup analysis suggest that the incidence of PONV decreases in male patients and higher weight patients, although the patient's body weight may be related to age, as the study cohort included many children. It is suggested that the major risks for PONV in mentally challenged patients after day care general anesthesia are no use of propofol, lower age, female sex and lower weight.     

Operative time,length of stay and reoperation rates for orthognathic surgery

Orthognathic surgery improves quality of life in terms of oral function and facial aesthetics. Our aim was to establish and compare operative time and length of inpatient stay for orthognathic procedures, and to assess the reoperation rate. Departmental electronic data base was used to identify all patients undergoing orthognathic surgery in a single unit between the 01/01/2016 and the 01/08/2018. 251 patients were identified who underwent 409 orthognathic surgery procedures. The mean operating time for a bimaxillary osteotomy (n=107) was 139.3 min. For single jaw procedures, the mean operating time for a Le Fort I osteotomy (n= 42) was 82.2 min and for a bilateral sagittal split osteotomy (BSSO) (n= 102) was 80.3min. Bimaxillary osteotomy combined with genioplasty (n=17) this increased the operating time on average by 31 min. and of a BSSO combined with a genioplasty (n=14) by 27 mins. The mean postoperative hospital stay was 1.2 ± 0.2 days. 96.4% patients spent only one postoperative night in hospital. 6/251 (2.4%) patients required re-operation. In regression analysis, age was the only significant factor in increasing length of stay (p<0.008), 95% CI 0.03-0.2). Our review shows short operating times and postoperative inpatient stays in a large cohort of patients undergoing orthognathic surgery. This is combined with a low reoperation rate. This may point to a patient benefit from high volume orthognathic centres.