Early and long-term changes in the muscles of the mandible following orthognathic surgery

Objectives

The aim of the present study is to evaluate the early and long-term postoperative dimensional changes of the muscles of the mandible in patients with orthognathic surgery for class II and class III malocclusions by using ultrasonography (US).

Material and methods

Twenty-six patients who underwent bimaxillary orthognathic surgery for class II or class III malocclusions (14 and 12 patients, respectively) were ultrasonographically examined. The length, width, and cross-sectional area of the masseter and suprahyoid muscles were measured at three different time points: T₀ (preoperatively), T₁ (early postoperatively at 1 month after the surgery), and T₂ (late postoperatively at 9 months). A repeated measures ANOVA was used to calculate statistically significant dimensional changes of the mandibular muscles.

Results

Statistically significant dimensional changes were found postoperatively in class II malocclusion patients only. The digastric muscle showed higher values for the length and lower values for the width (p < .05) at T₁. The geniohyoid muscles were higher in length at T₁ and lower in cross-sectional area (CSA) (p < .05) at T₂. A decreased measured length and an increased measured width were found in case of the mylohyoid muscle (p < .05) at T₂. The early and long-term postoperative dimensional changes of the masseter muscle were not statistically significant.

Conclusions

The mandibular muscles showed a variable adaptive response to the orthognathic surgery. US should be considered for the long-term follow-up of muscular dimensional changes in class II malocclusion patients.

Clinical relevance

From a clinical perspective, US is a reliable, non-invasive, and widely available method, which allows monitoring the postoperative muscular changes occurring in class II malocclusion patients.

     

Characterization of different paresthesias following orthognathic surgery of the mandible.

PURPOSE: Paresthesia is a well known consequence of peripheral nerve injury. However, the neural mechanisms of the 2 recognized types, spontaneous and elicited, are currently unknown. This study aimed to investigate these 2 paresthesias and the possible mechanisms accompanying orthognathic surgery. PATIENTS AND METHODS: Mechanical-touch thresholds and current perception threshold were measured before and 7 days after surgery in 60 chin sites (mental nerve area) of 30 patients who underwent orthognathic surgery. Similar testing was conducted on healthy volunteers (controls). All sites were classified by the presence or absence of each paresthesia: spontaneous paresthesia or no spontaneous paresthesia, and elicited paresthesia or no elicited paresthesia. Presence or absence analyses were followed-up for 6 weeks after surgery. RESULTS: Gender differences and maxillary surgery did not change the incidence of paresthesia during postoperative week 1 (chi-square test, P > .05). A significantly higher mechanical-touch threshold was observed with spontaneous paresthesia compared with no spontaneous paresthesia (Mann-Whitney U-test; P < .05), but not between no elicited paresthesia and elicited paresthesia (Mann-Whitney U-test; P > .05). A significant increase in postsurgery current perception thresholds values compared with presurgery values was observed at 2,000 Hz in spontaneous paresthesia, and at 2,000 and 5 Hz in elicited paresthesia (paired t test, P < .05). The incidence of spontaneous paresthesia decreased more rapidly than elicited, while the latter tended to increase again during the 6-week postsurgical test period. CONCLUSION: The results suggested that both spontaneous and elicited paresthesias are associated with damage and dysfunction in myelinated primary afferent fibers, but additional neural mechanisms are implicated during elicited paresthesia.     

正颌外科治疗后颞下颌关节改变的X线研究

目的 了解正颌外科手术后颞下颌关节（ｔｅｍｐｏｒｏｍａｎｄｉｂｕｌａｒ ｊｏｉｎｔ,ＴＭＪ）形态的改变,探讨手术方式不同对ＴＭＪ的影响。方法 正颌手术患者５７例,术前、术后１周、１年分别拍摄定位许勒位片用于观察髁突位置及关节形态的变化。结果 ①正颌手术可导致髁突移位,但大多数关节适应后并不发生病变,术后１年髁突位置已调整到术前相似的位置。②手术方式不同髁突位置的变化也不尽相同。③８６．４％的患者关节无明显变化或发生了适应性改建;１３．６％患者关节发生了退行性改变。结论 正颌手术可对ＴＭＪ产生影响,但大部分处于关节的正常适应范围内。     

Changes in border movement of the mandible in skeletal Class III before and after orthognathic surgery

The purpose of this study was to examine the changes in border movement of the mandible before and after mandibular ramus osteotomy in patients with prognathism. The subjects were 73 patients with mandibular prognathism who underwent sagittal split ramus osteotomy (SSRO) with and without Le Fort I osteotomy. Border movement of the mandible was recorded with a mandibular movement measure system (K7) preoperatively and at 6 months postoperatively. Of the 73 patients, 21 had measurements taken at 1.5 years postoperative. Data were compared between the pre- and postoperative states, and the differences analyzed statistically. There was no significant difference between SSRO alone and SSRO with Le Fort I osteotomy in the time-course change. The values at 6 months postoperative were significantly lower than the preoperative values for maximum vertical opening (P = 0.0066), maximum antero-posterior movement from the centric occlusion (P = 0.0425), and centric occlusion to maximum opening (P = 0.0300). However, there were no significant differences between the preoperative and 1.5 years postoperative measurements. This study suggests that a postoperative temporary reduction in the border movement of the mandible could recover by 1.5 years postoperative, and the additional procedure of a Le Fort I osteotomy does not affect the recovery of mandibular motion after SSRO.     

Neurosensory changes following orthognathic surgery

Much variability exists among studies of neurosensory disturbance following facial surgery. This diversity of findings may be a function of the different surgical procedures and measurement methods used. The present study compared 3 methods of assessing neurosensory loss following surgical orthodontics. Two objective tests and 1 subjective test were administered to 24 patients preoperatively and 4 weeks postoperatively. These included measures of 2-point discrimination, pressure-pain thresholds, and perceived sensation changes in specific facial regions. Postoperatively, all patients needed greater separation on the 2-point discrimination test in the lower facial regions, but not in the upper regions. Bilateral sagittal split osteotomy patients, especially males, required greater separation on these lower sites. Pressure-pain thresholds were not significantly impaired in most patients. Those who underwent combined maxillary and mandibular procedures experienced lower thresholds on the lower lip, while bilateral sagittal split osteotomy patients reported lower thresholds on the upper lip. The 2-point discrimination test was consistent with patients' self-ratings of neurosensory problems using facial maps, but the pressure-pain test was not. The majority of patients reported changed sensation in the lower facial regions postoperatively, regardless of surgery type. Examiners were less likely to rate these same facial regions as different in sensory acuity. Male patients were more likely to report sensory loss or pain postoperatively. These findings suggest that self-reports of neurosensory change following orthognathic surgery are consistent with tests of 2-point discrimination and somewhat higher than examiner ratings, but the objective test of pressure-pain thresholds in this study was least sensitive to neurosensory changes.     

Postoperative pneumomediastinum and pneumothorax following orthognathic surgery

Pneumomediastinum and pneumothorax are rare complications in the postoperative oral and maxillofacial surgery patient. Review of the sequence of events relating to these two life-threatening conditions emphasizes the importance of awareness of the clinical presentation and pathophysiology of these conditions as well as the need for judicious pulmonary physiotherapy in the intubated patient.     

Treatment-induced errors in occlusion following orthognathic surgery

Posttreatment occlusion following orthognathic surgery is often different from that predicted in the treatment plan. Differences between intended and actual occlusion may be treatment-induced occlusal errors caused by mismatches between the centers of rotation of the mandible and of the articulated models. Discrepancies in the position of the articulator center of rotation (relative to the position of the center of rotation of the patient's mandible) influence the magnitude of occlusal errors. A computer model was developed to quantify these errors. As the center of rotation of the articulated models becomes more divergent from the patient's center of rotation, the magnitude of the occlusal errors increases. This magnitude increases most rapidly along the line that is perpendicular to the line joining the patient's center of rotation and a preselected mandibular landmark (incisor tip or molar cusp, for instance). For small changes in vertical dimension, clinically insignificant errors result, independent of the degree of mismatch between the centers of rotation. Clinical implications of these findings are discussed.     

Change in cranio-cervical angulation following orthognathic surgery

Changes in natural head posture (NHP) were investigated in 33 patients (10 males, 23 females) with an age range of 16-40 years (median 21 years) following orthognathic surgery to change vertical face height. The reproducibility of the radiographer's technique of taking radiographs in NHP was investigated using a photographic method and found to be acceptable. The patients were divided into two groups: group 1, patients who had more than 3 mm of vertical change in anterior total face height (ATFH) and group 2, those who had less than 3 mm vertical change.For group 1 there was a significant relationship between ATFH change and cranio-cervical angulation (NSL/OPT) change (r = 0.532, P = 0.023), compared with group 2 (r = -0.247, P = 0.376). A similar relationship was revealed between lower anterior face height (LAFH)/ATFH ratio and NSL/OPT, where the correlation was also higher in group 1 (r = -0.635, P = 0.005) compared with group 2 (r = -0.182, P = 0.515). The correlation between cranio-vertical angulation (NSL/VER) and ATFH was not significant for group 1 (r = 0.406) or group 2 (r = 0.239) patients. Additionally, NSL/VER and LAFH/ATFH correlation for the two groups was not significant (r = -0.392 and -0.338, respectively).There appears to be a relationship between the reduction in vertical face height following orthognathic surgery and neck posture (as indicated by NSL/OPT). As no significant relationship was found between the reduction in face height and head posture (as indicated by NSL/VER) this suggests that neck posture, rather than head posture, had changed.     

Patient expectations and satisfaction following orthognathic surgery

Orthognathic surgery aims to correct dentoskeletal and facial discrepancies. Treatment usually requires a minimum of 18 months, necessitating that patients are adequately satisfied with the treatment provided. This study aimed to assess the determinants of patient satisfaction following treatment. One hundred and eighteen patients who had undergone orthognathic surgery were included prospectively. All participants completed a questionnaire regarding their reasons for undergoing treatment, treatment logistics, treatment outcomes, and satisfaction throughout their journey. Most patients were ‘very satisfied’ (71.2%) or ‘satisfied’ (19.5%) with the overall treatment. The majority wished to improve their smile (78.0%); post-treatment, 89.0% of patients reported an improved smile. Almost half of the patients (46.6%) stayed in hospital for only one night, and 41.5% took over 4 weeks off work or school post-surgery. People with postoperative breathing difficulties spent more days in hospital (P = 0.021), but importantly, the duration of hospital stay did not differ between maxillary advancement, bilateral sagittal split osteotomy, and bimaxillary surgery (P = 0.78). In conclusion, patient satisfaction was high following orthognathic treatment. The results highlight areas for improvement, such as information delivery to the patient throughout the treatment journey, and show that the presence of ongoing problems is an important predictor of patient satisfaction.     

Masseter muscle changes following orthognathic surgery

Abstract Objective: To evaluate the long-term changes of masseter muscle morphology in skeletal Class III patients with facial asymmetry following two-jaw orthognathic surgery (Le Fort I osteotomy + intraoral vertical ramus osteotomy). Materials and Methods: Using computed tomography (CT), a longitudinal study was conducted on 17 skeletal Class III patients with facial asymmetry. Measurements from the reconstructed three-dimensional (3D) CT images were compared from T1 (before surgery), T2 (1?year after surgery), and T3 (4?years after surgery). The maximum cross-sectional area (CSA), orientation, thickness, and width of the masseter muscle were measured on both the deviated and nondeviated sides. The control group included 17 volunteers with skeletal and dental Class I relationships without dentofacial deformities. Results: At T1, there were no significant differences in CSA, thickness, or width of masseter muscle between the deviated and nondeviated sides. Masseter muscle orientation was significantly more vertical on the nondeviated side than on the deviated side at T1 (P < .01); no significant bilateral differences were noted at T2 and T3. At T1, masseter muscle measurements were significantly lower than controls (P < .01). During T1-T3, a significant increase was noted in CSA, thickness, and width (P < .01) of masseter muscle. At T3, no significant difference was noted between the study and control groups. Conclusion: After surgery, the masseter muscle measurements of skeletal Class III asymmetry patients showed no significant differences compared with the control group within the 4-year follow-up period, indicating adaptation to the new skeletal environments and increased functional demand.     

Major vascular complications of orthognathic surgery: false aneurysms and arteriovenous fistulas following orthognathic surgery

False aneurysms and arteriovenous fistulas are rare complications of orthognathic surgery. The vessel most commonly involved with false aneurysms following mandibular surgery is the internal maxillary artery, and this vessel, especially the sphenopalatine branch, may also be involved following maxillary surgery. An unusual factor in the presentation of false aneurysms following Le Fort I osteotomies is an initial episode of epistaxis occurring greater than 2 weeks postoperatively. Arteriovenous fistulas following orthognathic surgery are more apt to involve large vessels, especially the internal carotid artery. Embolization procedures are the treatment of choice for false aneurysms and arteriovenous fistulas in the maxillofacial region following orthognathic surgery.     

Recovery of neurosensory function following orthognathic surgery

The purpose of this study was to prospectively define the recovery of touch discrimination following four commonly performed surgical procedures in 22 consecutive patients with no previous maxillofacial surgery. The surgical groups studied were Le Fort I osteotomy (LEFORT; n = 13), sagittal split ramus osteotomy (SSRO; n = 6), intraoral vertical ramus osteotomy (IVRO; n = 9), and isolated genioplasty (GENIO; n = 5). Neurosensory function was assessed by three different testing modalities which included static light touch (SLT), moving touch discrimination (MTD), and two-point discrimination (TPD). Cutaneous sensation of the lower lip and chin were examined for the mandibular procedures, whereas the infraorbital and upper lip regions were evaluated following maxillary surgery. Immediately following surgery, each group varied in both the incidence and magnitude of neurosensory deficits (NSD). The SSRO group had the highest percentage of sites with immediate postsurgical NSD to both SLT (72%) and MTD (67%), followed by the LEFORT (SLT = 50%, MDT = 58%), GENIO (SLT = 27%, MTD = 6%), and IVRO groups (SLT = 11%, MTD = 18%), respectively. Each group also varied in the severity of the initial postoperative deficit as measured by SLT, with the SSRO group showing the greatest deficit followed by the LEFORT, GENIO, and IVRO groups. During the 6-month recovery period each group approached preoperative levels of sensation at a different rate. The LEFORT group recovered most rapidly, with few anatomic sites showing NSD (SLT = 20%, MTD = 5%) at the 1-month postoperative examination, and the majority of the group (96%) returned to preoperative sensation by 3 months following surgery. The SSRO group recovered more slowly, with approximately half of the group demonstrating a deficit (SLT = 50%, MTD = 59%) at 1 month, which diminished to about one fourth of the sites (SLT = 25%, MTD = 5%) by 3 months. Most of the SSRO group (90%) exhibited no residual deficit 6 months following surgery. The IVRO group had few sites with immediate NSD (SLT = 11%, MTD = 15%). In none of the surgical groups was a statistically significant correlation found between the severity of the initial NSD and length of time to complete recovery.     

Recovery of mandibular mobility following orthognathic surgery

The aim of this prospective study was to define the patterns of recovery of mandibular mobility following three commonly performed orthognathic surgical procedures. Twenty-two consecutive patients undergoing either isolated Le Fort I osteotomy (LE FORT; n = 7), sagittal split ramus osteotomies (SSRO; n = 7), or intraoral vertical ramus osteotomies (IVRO; n = 9) were studied. LE FORT and SSRO patients had no mandibular immobilization, whereas IVRO patients were immobilized by dental fixation for 3 weeks. Mandibular mobility was assessed by measurement of maximal mandibular opening (MMO) and lateral and protrusive excursions. No significant difference in MMO was observed between groups prior to surgery (LE FORT, 47.0 mm; SSRO, 50.7 mm; IVRO, 54.5 mm). A significant reduction in MMO occurred immediately after surgery in the LE FORT and SSRO groups and at release of fixation in the IVRO group. Each group returned to presurgical levels of mandibular mobility at a different rate following surgery. LE FORT patients recovered quickly, regaining 83% (mean, 38.7 mm) of MMO by 1 month and exceeded preoperative levels (mean, 49.6 mm) by 6 months. SSRO patients showed hypomobility (mean, 23.5 mm) after 1 month, with significant improvement in MMO (mean, 38.0 mm) at 2 months, and nearly complete recovery (96.2%; mean, 48.8 mm) at 6 months. IVRO patients recovered rapidly after release of dental fixation, achieving 78% (mean, 39.8 mm) of preoperative MMO at 2 months. This study shows that significant differences in recovery patterns of mandibular mobility exist between surgical procedures. The clinician should be aware of these differences in recovery patterns in defining goals for individual patient rehabilitation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adaptations in lip posture and pressure following orthognathic surgery

Lip pressures before and after orthognathic surgery were studied to evaluate the relationship between posttreatment soft-tissue adaptation and incisor stability. After all surgical procedures, physiologic adaptation resulted in the maintenance of pressures during speech and swallowing. When the maxilla was advanced by LeFort I osteotomy, a significant decrease in resting pressure of the upper lip was observed instead of the expected increase and incisor stability did not seem related to soft-tissue influences. When the mandible was advanced by sagittal split osteotomy, resting pressure did not increase as expected, but there was a tendency for incisors to become more upright after fixation release, perhaps as a rebound from labial tipping in fixation. When soft tissues were relaxed as the mandible rotated forward following superior repositioning of the maxilla, resting pressures decreased and lower incisors tended to be positioned forward as predicted by equilibrium theory.     

Changes in posterior airway space, pulmonary function and sleep quality, following bimaxillary orthognathic surgery

Bimaxillary orthognathic surgery (BOS) is commonly used in the correction of severe Class III deformities (mandibular prognathism with maxillary retrognathism). The postural response of the pharyngeal airway after mandibular setback and maxillary advancement procedures is clinically crucial for maintaining optimum respiration. Patients might suffer from obstructive sleep apnoea, postoperatively. The aim of this study was to determine the effects of BOS on pharyngeal airway space, respiratory function during sleep and pulmonary functions. 21 male patients were analysed using cephalometry, spirometry for pulmonary function tests, and a 1 night sleep study for full polysomnography before and 17±5 months after BOS. The data show that the hyoid bone repositioned to the inferior, the tongue and soft palate displaced to the posterior, narrowed at the oropharynx and hypopharynx and widened at the nasopharynx and velopharynx levels significantly (p<0.05). The alterations indicated decreased airway resistance and better airflow. As a consequence of polysomnography evaluation, the sleep quality and efficiency of the patients improved significantly after BOS. Patients who undergo BOS should be monitored with pulmonary function tests and polysomnography pre- and postoperatively to detect any airway obstruction.     

Short-term periodontal and microbiological changes following orthognathic surgery

ObjectiveAim of the present study was to evaluate the influence of orthognathic surgery on the development of periodontal and microbiological changes.Materials and methodsFifteen consecutively treated patients with a mean age of 24.9 ± 7.7 years receiving orthognathic surgery were included in the present study. Plaque index (PI) and concentrations of 11 periodonto-pathogenic bacteria were recorded one day prior to surgery (t₀) and one week (t₁) and six weeks (t₂) post-surgery. In addition, a complete periodontal examination including pocket probing depth (PPD), gingival recession (GR), clinical attachment level (CAL), bleeding on probing (BOP) and width of keratinized gingiva (WKG) was conducted at t₀ and t₂. For statistical analysis, general linear model and paired t-test were applied.ResultsA significant increase of PI (t₀–t₁, p = 0.037) was followed by a significant decrease (t₁–t₂, p = 0.017). Apart from Eikenella corrodens (p = 0.036), no significant microbiological changes were recorded. PPD significantly increased on oral sites (p = 0.045) and GR especially on buccal sites (p = 0.001). In the incision area the development of GR was significantly higher on the test (buccal) than on the control sites (oral). Both gingival biotypes were affected by GR.ConclusionsOrthognathic surgery causes statistically significant changes of periodontal parameters, but these changes do not necessarily impair the aesthetic appearance of the gingival margin.