Changes in masticatory function after orthognathic treatment in patients with mandibular prognathism.

Changes in masticatory function were measured in 27 patients in whom mandibular prognathism was corrected surgically. The mean value of masticatory efficiency before treatment was 46% of that of control subjects with normal occlusion. It improved, but remained at 60% of the control value postoperatively. Similar changes were seen in the number and area of occlusal contacts and the integrated muscle activities of the masseter and temporalis on the chewing side, but the postoperative improvement in masticatory efficiency was mainly the result of improvement in masseter activity. The mean values of masticatory cycle variables in the patient group did not differ significantly from those of the controls. Their preoperative mean coefficients of variation, which were significantly higher than those of the controls, decreased significantly postoperatively. These results suggest that the stability of masticatory rhythm was improved by orthognathic surgery.     

Changes in oropharyngeal airway and respiratory function during sleep after orthognathic surgery in patients with mandibular prognathism

The aim of this study was to examine the effects of mandibular setback surgery on pharyngeal airway space and respiratory function during sleep. The subjects were 22 patients in whom mandibular prognathism was corrected by bilateral sagittal split ramus osteotomy; either one jaw or two jaw surgery. Polysomnography was performed before surgery and 6 months after surgery, and the apnea hypopnea index (AHI) and arterial oxygen saturation during sleep were measured to assess respiratory function during sleep. Morphological changes were studied using cephalograms taken immediately before, a few days after and 6 months after surgery. As a control, 10 subjects without sleep-disordered breathing underwent the same examinations. AHI was not changed significantly after surgery, although two patients were diagnosed with mild obstructive sleep apnea (OSA) syndrome after surgery. They were not obese, but the amounts of mandibular setback at surgery were large. In conclusion, a large amount of mandibular setback might inhibit biological adaption and cause sleep-disordered breathing, and it might be better to consider maxillary advance or another technique that does not reduce the airway for patients with skeletal class III malocclusions who have large anteroposterior discrepancy and/or maxillary hypoplasia.     

Effects of orthognathic surgery on pharyngeal airway and respiratory function during sleep in patients with mandibular prognathism

The aim of this study was to determine changes in overnight respiratory function and craniofacial and pharyngeal airway morphology following orthognathic surgery. The subjects were 40 patients in whom mandibular prognathism was corrected by orthognathic surgery: a one-jaw operation in 22 patients and a two-jaw operation in 18 patients. Morphological changes were studied using cone beam computed tomography immediately before surgery and at more than 6 months after surgery, and the apnoea–hypopnoea index (AHI) was measured with a portable polysomnography system. Pharyngeal airway volume was decreased significantly after surgery, especially in the one-jaw operation group. AHI was not changed significantly after surgery in either group, although AHI in one patient in the one-jaw operation group was increased to 19 events/h. There was no significant change in pharyngeal airway morphology in that patient, but he was obesity class 1 and was 54 years old. In conclusion, some patients who are obese, have a large amount of mandibular setback, and/or are of relatively advanced age may develop sleep-disordered breathing after mandibular setback; a two-jaw operation should therefore be considered in skeletal class III patients who have such risks because it decreases the amount of pharyngeal airway space reduction caused by mandibular setback surgery.     

正颌外科和正畸联合治疗下颌前突畸形

目的：总结分析下颌升支部和下颌体部截骨矫正下颌前突畸形的手术和正畸治疗特点。方法：根据手术设计需要，将125例下颌前突畸形患者分下颌升支部截骨和下颌骨体部截骨两组，并分别进行内容不同的术前术后的正畸治疗。结果：两种术式均获得满意的治疗效果。下颌升支部截骨和下颌骨体部截骨满意率分别为88.3%和83.3%。2例下颌体部截骨术后2年复发，行二次手术予以矫正。结论；必需根据不同的术工，设计不同的术前术后正畸方案。一方面保证下颌前突畸形患者获得满意的美学改善，同时在新建的颌位上应具有良好的he关系。     

Evaluation of masticatory function following orthognathic surgical correction of mandibular prognathism.

Masticatory function was examined in 17 patients with mandibular prognathism before and after bilateral sagittal splitting osteotomy of the mandibular rami. Masticatory efficiency was measured by means of a spectrophotometer, using adenosine triphosphate (ATP) granules, the biting force and occlusal contact area. Masticatory functions showed a tendency to gradual improvement postoperatively. Concerning masticatory efficiency, mean values of absorbance of ATP granules in patients with mandibular prognathism were inferior to those of subjects who possess a normal occlusion, even 12 months after operation.     

Changes in bite force and occlusal contact area after orthognathic surgery for correction of mandibular prognathism

OBJECTIVE: This study examined the long-term changes of bite force and occlusal contact area in patients with prognathous after orthognathic surgery with a newly developed pressure-sensitive sheet (Dental-Prescale; Fuji Photo Film Co). STUDY DESIGN: Fifty-seven patients with prognathous were examined. Bite force and occlusal contact area were measured just before operation and at 2 weeks, 1 month, 3 months, 6 months, 1 year, 2 years, and 3 years after operation. Forty control subjects with normal occlusion were also measured. RESULTS: The bite force and occlusal contact area of the patients were significantly greater than the preoperative level at 1 year, 2 years, and 3 years after operation. However, they were still significantly lower than the control subject level even at 3 years after operation. CONCLUSIONS: This study suggests that orthognathic surgery improves the bite force and occlusal contact area of patients with prognathous. However, at 3 years from the time of operation, patients had not reached control subject levels.     

Mandibular function and dysfunction in patients with mandibular prognathism

There are indications that in patients with mandibular prognathism there is a great risk of mandibular dysfunction symptoms. The present study was undertaken to verify this and to investigate whether surgical correction of the sagittal discrepancy would improve the functional abilities. The material comprised a group of 28 untreated patients with mandibular protrusion and another group of 44 patients who were operated on 10 years ago. The functional status and subjective symptoms were recorded according to the principles introduced by Helkimo. The results indicate a great reduction of the subjective symptoms in the treated group, and even the objective evaluation shows a reduction of the dysfunctional symptoms in the treated persons, particularly in relation to the movement capacity of the mandible. The number of occluding teeth was significantly greater in the treated persons, and the number of occlusal interferences was smaller. Thus, it seems that a repositioning of the mandible to a correct sagittal position will improve function. A normal anatomic foundation may therefore be an important factor in securing normal mandibular function.     

Changes in mandibular mobility after different procedures of orthognathic surgery.

A prospective study including 63 adult Class II and Class III patients was carried out in order to examine short- and long-term effects of four different treatment methods on mandibular mobility. The patients were treated either (Group A, control-group) orthodontically alone or (Group B) by a LeFort I-osteotomy, a (Group C) mandibular advancement or (Group D) a two-jaw surgery/mandibular set-back. In the surgery-groups (B, C, and D) maximum opening, protrusion and lateral excursions were measured 2 days pre-operatively (T0), and 3, 8, 14.5, and 25.5 months post-operatively (T1-T4). In the control-group (A) at T0 and T4 was measured, only. Significantly differing effects of the four treatment methods on mandibular mobility were detected. (A) Orthodontic treatment alone, (B) maxillary advancement by LeFort I osteotomy, and (D) two-jaw surgery/mandibular set-back osteotomy did not influence mandibular mobility permanently. Temporary decreases in groups B and D (P less than or equal to 0.05) were observed, however. In contrast, permanent reductions after (C) mandibular advancement took place (P less than or equal to 0.001). Longitudinal survey showed that in all surgery groups recoveries were limited to a short period of 3-14.5 months, depending on the movement. Surprisingly, a closer similarity between the LeFort-I group (B) and the two-jaw surgery group (D), rather than between the sagittal-split groups (C and D), was seen indicating that the problem of reduced mobility after orthognathic surgery can be limited to Class II therapy. It was concluded that in Class III therapy, the application of rigid fixation in combination with a method of maintaining condyle-position, thereby dispensing with maxillomandibular fixation, prevents permanent reductions in mobility and guarantees a rapid recovery to pre-operative mobility levels.     

Postoperative mandibular stability after orthognathic surgery in patients with mandibular protrusion and mandibular deviation

Skeletal stability and temporomandibular joint (TMJ) signs and symptoms were analyzed in 23 patients in whom mandibular protrusion and mandibular deviation had been corrected using bilateral sagittal split ramus osteotomy (BSSRO group, n = 10) and unilateral SSRO and intraoral vertical ramus osteotomy (USSRO+IVRO group, n = 13). Miniplate fixation was used in SSRO but no fixation was used in IVRO. The ratio of condylar bony change was 30.4% (7/23) and all condylar bony changes were seen on the deviated side. All preoperative signs and symptoms of TMJ disorders (4/13 patients in the USSRO+IVRO group and 2/10 patients in the BSSRO group) disappeared after surgery. Comparing the USSRO+IVRO group and the BSSRO group, in patients without condylar bony change, the mandible in both groups was stable anteriorly and horizontally after surgery, even though there was a larger horizontal mandibular movement in the USSRO+IVRO group during surgery. Comparing patients with condylar bony change versus no condylar bony change in the USSRO+IVRO group, postoperative horizontal mandibular displacement was significantly larger in the condylar bony change group than in the no condylar bony change group. These results support the idea that USSRO+IVRO can be useful in correcting mandibular deviation as well as improving signs and symptoms of TMJ disorders. However, it also seems important to be aware of the possibility of horizontal mandibular relapse in patients with condylar bony change.     

Changes in occlusal state of patients with mandibular prognathismafter orthognathic surgery: a pilot study

This study examined the occlusal state of patients with mandibular prognathism and compared it with that of adults with normal occlusion (controls). It also examined changes in occlusal state after orthognathic operations in these patients. The values of occlusal contact area and bite force in patients before operation were significantly lower than in controls, and occlusal pressure in patients was higher than in controls. The occlusal contact area and bite force of the patients 1 month after the operation had decreased to below preoperative values. These values 12 months after the operation had increased by 2.0 and 1.8 times in women and 1.4 and 1.4 times in men, respectively, compared with preoperative values. However, absolute values remained extremely low compared with those of controls. In contrast to the above, occlusal pressure reached its maximum value 1 month after the operation and at 12 months it was close to the value for controls.     

Changes in the facial soft-tissue profile after mandibular orthognathic surgery

Objectives

To investigate the correlation between soft- and hard-tissue changes after mandibular orthognathic surgery, to generate precise prognostic values for the esthetic treatment outcome of the facial profile.

Material and Methods

In this retrospective study, sagittal changes in the facial soft tissue profile in relation to surgical changes in hard structures after mandibular osteotomy were examined. The sample population included 144 reported adult patients aged 17–50 years who had received combined mandibular orthognathic surgery and orthodontic treatment at the Department of Orthodontics, Ludwig-Maximilians University of Munich, Germany. Both mandibular advancement and mandibular setback cases in monognathic and bignathic osteotomy procedures were included. All subjects had undergone rigid fixation. A cephalometric analysis of presurgical and postsurgical cephalograms was performed, and the correlations between hard-tissue and soft-tissue change ratios were evaluated using a bivariate linear regression analysis.

Results

The lower lip, represented by the landmark Labrale inferius (Li), followed the lower incisor (Ii) by 77%. The soft-tissue B-point (B’) followed the B-point (B) by 97% and the soft-tissue Pogonion (Pg’) followed the Pogonion (Pg) by 97% in a linear correlation.

Conclusion

The scatterplots show a distinct linear correlation and no significant difference in the direction of the movement. A wider spread for the lower lip (Li/Ii) indicates a lower predictability of the expected lip position, whereas a narrow spread of the chin values (B’/B and the Pg’/Pg) reveals a very good predictability of the postoperative chin position.

Clinical relevance

This study contributes valid data for the soft-tissue profile prediction in orthognathic surgery.

     

Increase in mandibular and chin projection with orthognathic surgery

Three groups of twelve patients, each of whom had a Class II, Division 1 malocclusion with a markedly convex facial profile and steep mandibular plane, were treated by orthodontic means and orthognathic surgery. One group had mandibular advancement, another had maxillary elevation, and the third had both surgical procedures combined, with genioplasties performed in some cases from each group. Changes were studied with the aid of lateral cephalometric headfilms taken just after surgery and from 5 to 105 months later. Horizontal changes in point B and pogonion after the follow-up period were 7.0 mm and 8.5 mm with mandibular surgery, 5.4 mm and 9.3 mm with maxillary surgery, and 10.7 mm and 16.4 mm with combined surgery. The amount of change is much larger than found with orthodontic or orthopedic treatment alone and makes possible the successful treatment of very difficult problems.