Influence of surgical orthodontic treatment on masticatory function in skeletal Class III patients

Skeletal Class III patients exhibit malocclusion characterised by Angle Class III and anterior crossbite, and their occlusion shows total or partially lateral crossbite of the posterior teeth. Most patients exhibit lower bite force and muscle activity than non‐affected subjects. While orthognathic surgery may help improve masticatory function in these patients, its effects have not been fully elucidated. The aims of the study were to evaluate jaw movement and the electromyographic (EMG) activity of masticatory muscles before and after orthognathic treatment in skeletal Class III patients in comparison with control subjects with normal occlusion. Jaw movement variables and EMG data were recorded in 14 female patients with skeletal Class III malocclusion and 15 female controls with good occlusion. Significant changes in jaw movement, from a chopping to a grinding pattern, were observed after orthognathic treatment (closing angle P < 0·01; cycle width P < 0·01), rendering jaw movement in the patient group similar to that of the control group. However, the grinding pattern in the patient group was not as broad as that of controls. The activity indexes, indicating the relative contributions of the masseter and temporalis muscles (where a negative value corresponds to relatively more temporalis activity and vice versa) changed from negative to positive after treatment (P < 0·05), becoming similar to those of control subjects. Our findings suggest that orthognathic treatment in skeletal Class III patients improves the masticatory chewing pattern and muscle activity. However, the chewing pattern remains incomplete compared with controls.     

骨性III类错牙合畸形患者正颌手术前后咀嚼肌功能变化的初步研究

目的:应用肌电图仪评价骨性III类错牙合畸形患者正颌手术前后咀嚼肌功能的变化。方法:收集16例骨性III类错牙合畸形需正颌手术病例和20例正常牙合对照组,应用MedelecSynergy肌电图仪分别在静息放松、正中紧咬、前伸、开口、侧方和咀嚼运动时,测定双侧颞肌前束、咬肌和二腹肌前腹的表面募集电位,并计算其肌不对称指数运动。病例组在术后3个月和6个月时重复测定,采用t检验进行统计学分析,并与对照组进行比较。结果:手术前病例组咀嚼肌电位小于对照组,尤以紧咬和咀嚼时差异显著(P<0.05),肌不对称指数与对照组无差异。术后3个月时,部分肌功能恢复,但紧咬和咀嚼时募集电位下降显著(P<0.001),肌不对称指数也增大,提示此时肌功能尚未完全恢复。术后6个月各种功能运动时的募集电位均大于术前水平,肌不对称指数则基本小于术前水平,说明肌功能有所改善。结论:骨性III类错牙合畸形患者手术前咀嚼肌功能弱于对照组,正颌手术矫正了颌骨位置和咬合关系,改善了患者的咀嚼肌功能。     

正颌手术后咀嚼肌改变的研究进展

正颌手术通过打破原有的颌骨系统,重建咬合平衡来达到改善面型和咀嚼功能的目的。随着现代医学的发展和人们观念的进步,正颌外科被越来越多的患者所接受,其疗效和安全性也得到了学术界的肯定,但是也有少部分术后恢复不佳甚至治疗失败的病例存在。颌面部解剖结构复杂,影响预后的因素较多,尤其正颌术后颌面部软组织的变化难以动态观察,至今其变化过程及机制尚不明确。本文就近年来正颌术后咀嚼肌改变的研究进展作一综述。     

Electromyographic evaluation of masseter and anterior temporalis muscles in patients with temporomandibular disorders following interocclusal appliance treatment

The purpose of this study is to evaluate the interocclusal appliance efficiency in patients with temporomandibular disorder (TMD), by using computerized electromyographic (EMG) evaluation in the rest position of the mandible. Twenty-two patients (male and female) with TMD symptoms, between 18 and 53 years of age, were examined. EMG evaluations were performed before the treatment and during the 90th, 120th and 150th day of using the interocclusal appliance therapy. In the 90th and 120th day, inserting canine guidance and group function disclusion, respectively, changed interocclusal appliance. The results showed that group function disclusion caused shorter EMG activity in the mandible rest position for the anterior temporalis muscle.     

The effect of experimental balancing interferences on masticatory performance

Immediate adaptation to experimental‐balancing interferences is known to affect jaw kinematics and electromyographic activity (EMG). However, little is known about the influence on masticatory performance parameters. This study hypothesises that balancing‐side interferences significantly reduce the performance of the masticatory system. Twenty‐one healthy subjects (eleven female, mean age: 24·1 ± 1·2 years) chewed standardised silicone cubes performing 15 masticatory cycles on the right side under three experimental conditions: (i) natural dentition (ND), (ii) splints with structured occlusal profiles (SS) (iii) splints with balancing interferences in the left molar region (OI). The particle size distribution was determined by a validated scanning procedure and curve fitted with the Rosin–Rammler function to determine X₅₀‐values. The EMG of both temporalis and masseter muscles was recorded simultaneously, and the total muscle work (TMW) was calculated. A jaw‐tracking device recorded the incisal movement path (IMP). The functional parameters under the experimental conditions were compared by repeated‐measures analysis of variance. The findings confirm our hypothesis. The X₅₀‐values differed significantly (P < 0·01) between ND and OI (4·34 vs. 4·60 mm), and between SS and OI (4·34 vs. 4·60 mm), respectively. In contrast, no significant differences (P > 0·05) were observed between SS and ND. There was no significant difference in both TMW (1269·0 vs. 1284·9 vs. 1193·9 μV*s) and IMP (720·2 vs. 735·3 vs. 723·1 mm) amongst the three conditions (P > 0·05). These findings confirm the assumption that the disturbance of the habitual chewing cycles by balancing‐side interferences significantly reduces the masticatory performance in the short term. Occlusal balancing‐side interferences are common technical failures of dental restorations. Simulation of this condition caused deterioration of masticatory performance in healthy young adults. Further studies should be carried out, on whether the observed effect is long‐term and whether masticatory performance decreases even more in patients with reduced adaptive capacity.     

Occlusal comparison of hand-articulation versus digital articulation in orthognathic surgery

The aim of the present study was to develop measurement methods to evaluate occlusal differences in digitally-articulated and hand-articulated models in final occlusal planning for orthognathic surgery. A total of 10 (five class II and five class III) previously treated orthognathic cases were analysed by three oral and maxillofacial surgeon investigators, creating a total of thirty cases. Investigators used physical models to create a preferred hand-held final occlusion, which were then scanned and saved utilising a Trios 3® scanner (3Shape). Models were digitally disarticulated and sent back to investigators after a period of at least a month for digital articulation. Novel measurements of dental roll, pitch, and translational differences were performed by an independent engineer using Materialise 3-Matic® software. Statistical analysis was used to evaluate translational differences, the effect of deformity, and inter-investigator variation. A mean (SD) translational difference of 1.58 mm (1.14) mm was seen between the thirty digital and hard-articulated cases analysed. Minimal difference was seen in roll and pitch between hand articulation and digital articulation. A significant translational difference was seen in class III cases compared with class II (p = 0.0006) but not in roll or pitch. There was no significant difference seen between investigators related to translation (p = 0.18), roll (p = 0.09), or pitch (p = 0.17). Digital articulation yielded similar results to hand held in this pilot study. Using measurement techniques described in larger cohorts, its accuracy can be validated using currently available technology.     

骨性III类错畸形患者正颌手术前后下颌运动轨迹变化的初步研究

目的:应用下颌运动轨迹仪评价骨性III类错牙合畸形患者正颌手术前后下颌运动的变化。方法:对15例骨性III类错牙合畸形需正颌手术病例和20例正常牙合对照组,采用ARCUSDigma下颌运动轨迹仪测定受试者最大开口运动,前伸及左右侧边缘运动距离,记录由计算机通过切牙运动模拟的双侧髁突的运动轨迹间的最大差数(MRC)。通过自身比较以及与对照组比较,评价患者在术前、术后3个月及6个月时下颌运动的变化以及髁突运动的对称性。采用团体t检验和配对t检验进行统计学处理。结果:术前患者除开口度外,其他运动距离均小于对照组,前伸运动差异显著(P<0.05);开口时MRC值大于对照组(P<0.05)。术后3个月时,开口度及左侧运动距离下降,前伸和右侧运动略有增加;MRC呈上升趋势。术后6个月时,下颌运动距离均有所增加,除开口度外其余均超过术前水平,与对照组无统计学差异;MRC小于术前水平且与对照组差异无显著性。结论:骨性III类错牙合畸形患者下颌运动水平与正常牙合存在差异,髁突运动对称性较差。正颌手术能够有效地改善患者的下颌运动功能。     

骨性III类错畸形患者正颌手术前后力变化的初步研究

目的:应用计算机咬合分析系统,评价正颌手术前后骨性III类错牙合患者牙合力的变化。方法:收集15例骨性III类错牙合需正颌手术病例,利用T-ScanII牙合诊断分析系统在术前1周内、术后3个月和术后6个月时对患者的牙合力进行测定,分析患者的总牙合力(TOF)、MIP/MAX指数、牙合力不对称指数(AOF)、牙合力中心点位置(COF)及咀嚼时最大位移距离(MCOF),应用配对t检验进行比较研究。结果:术后3个月时TOF有所上升,6个月时与术前水平相比已有显著差异(P<0.05),说明患者牙合力水平已有提高。MIP/MAX指数略有下降,但6个月时增大并超过术前水平。AOF术后呈下降趋势,在3个月和6个月时均比术前显著减小(P<0.01,P<0.001)。术后COF逐渐接近正常,MCOF减小,术后6个月时均较术前明显改善,说明患者牙合力水平已有提高。结论:正颌正畸联合治疗能够改善骨性III类错牙合患者的牙合力水平及力平衡性。     

下颌前突患者胸锁乳突肌和咀嚼肌的肌电研究

目的 探讨下颌前突患者在下颌运动和姿势位时,双侧颞肌前束(TA)、咬肌(MM)、二腹肌前腹(DA)和胸锁乳突肌(SCM)的肌电活动情况,为临床进行正颌手术提供参考数据.方法 选取于中国医科大学口腔医院颌面外科就诊的下颌前突患者32名为研究对象,运用美国BioEMG Ⅱ八道表面肌电仪和BioFLEX带状双极表面电极记录患...     

Orthodontic intervention combined with myofunctional therapy increases electromyographic activity of masticatory muscles in patients with skeletal unilateral posterior crossbite

Objective. The aim of this study was to evaluate the electromyographic activity of both the temporalis and masseter muscles and the mastication type of patients with skeletal unilateral posterior crossbite before and after orthodontic treatment and speech therapy. Methods. A total of 14 patients with skeletal unilateral posterior crossbite (eight females and six males), between 6–13 years of age, underwent electromyographic evaluation of their masseter and temporalis muscles in mandibular rest, habitual mastication and isometry. The subjects were assessed with regard to mastication type before and after orthodontic treatment and speech therapy. The data obtained during mandibular rest and habitual mastication were normalized in terms of the mean values of isometry. The Student's t-test was used for paired samples to compare the mean values of electromyographic activity (p < 0.05). Results. The masseters during habitual mastication presented higher electromyographic activity after both treatments (p = 0.0458). There was no significant difference between the contralateral masseters in terms of mandibular rest or habitual mastication before or after either treatment (p > 0.05). During habitual mastication, after the treatments, the temporalis muscle on the malocclusion side showed higher electromyographic activity than the contralateral side (p = 0.0263). Prior to therapy, all of the patients exhibited chronic unilateral mastication (n = 14) and 13 patients exhibited bilateral mastication after treatment. Conclusions. Orthodontic intervention combined with myofunctional therapy in patients with skeletal unilateral posterior crossbite provided an increase in the electromyographic activity of the masseter and temporalis muscles during mandibular rest and habitual mastication, with predominantly bilateral mastication.     

头颈部放射治疗对咀嚼肌神经电生理的影响

目的:探讨放疗后开口受限的发病机制,为临床放射治疗后开口受限的预防和治疗提供一定的实验依据.方法:以接受头颈部放射治疗后的7例患者为研究对象.分别对患者健、患侧咬肌、翼内肌与翼外肌进行同心圆针肌电图(EMG)检查,同时测量患者开口度.对受照射侧与未受照射侧咀嚼肌静息状态下出现失神经电位情况进行统计分析.结果:放射区域涉及咬肌有4例患者:肌肉静息状态下2例患者患侧咬肌出现失神经电位;肌肉大力收缩状态下2例患者患侧咬肌无募集电位;该4例患者开口度分别为16mm、31mm、15mm和9mm.放射区域涉及咬肌、翼内肌与翼外肌的有3例患者:肌肉静息状态下1例患者患侧翼外肌、咬肌出现失神经电位,1例患者患侧咬肌、翼内肌与翼外肌均出现失神经电位;肌肉大力收缩状态下,1例患者患侧咬肌、翼内肌与翼外肌均无募集电位.该3例患者开口度为39mm、17mm、5mm.受照射侧与未受照射侧出现失神经电位咀嚼肌数差异有统计学意义(p＜0.01).结论:头颈部放射治疗可引起放射区域咀嚼肌神经电生理异常改变,造成放射性周围神经病理性损伤;咀嚼肌神经肌肉系统的放射损伤是放射治疗后开口受限的发生因素之一.     

头位左倾和右倾变化对咀嚼肌肌电的影响

目的：研究不同的头位变化对咀嚼肌肌电活动的影响。方法：以30例健康正常[牙合]受试者为研究对象，通过肌电图仪（EMG）测试下颌姿势位和牙尖交错位最大紧咬时，5种头位姿势的颞肌前束（TA）、颞肌后束（TP）、咬肌（MM）、二腹肌前腹（DA）的肌电幅值，并对结果进行统计学分析。结果：下颌姿势位和紧咬位时，与正中头位相比，头左倾和右倾状态时咀嚼肌的肌电值变化无显著性差异（P〉0．05）。结论：咀嚼肌在头位左倾和右倾变化过程中所受影响不大。     

Electromyographic activity of masticatory, neck and trunk muscles of subjects with different skeletal facial morphology--a cross-sectional evaluation

The electromyographic pattern activity of masticatory, neck and trunk muscles was assessed using surface electromyography (sEMG) in 60 Caucasian adult females (20 subjects in skeletal class I, 20 subjects in skeletal class II and 20 subjects in skeletal class III), classified on the base of their skeletal class (ANB angle), corrected on the base of maxillary and mandibular rotations. The sEMG activity was recorded at mandibular rest position and during maximal voluntary clenching. At mandibular rest position, the sEMG activities of masseter and anterior temporal muscles were significantly higher in class III subjects than in class I and class II subjects, that showed no significant difference between them. Then, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups. During maximal voluntary clenching, no significant difference was observed in the sEMG activity of masticatory muscles among the three considered groups. However, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups, which showed no significant difference between them. In conclusion, the skeletal class seems to affect the sEMG pattern activity of masticatory, neck and trunk muscles.     

Preoperative incisor inclination in patients with Class III dentofacial deformities treated with orthognathic surgery

Our aim was to evaluate cephalometrically the preoperative inclination of the incisors in a group of 50 patients with Class III dentofacial deformities whose immediate preoperative lateral cephalometric radiographs were analysed after they had been treated by maxillary advancement. The radiographs were hand-traced by the same operator who made the cephalometric analysis. Mean values for each measurement were compared with the normal values using Student's t-test (p<0.05). Results showed significantly increased inclination of the upper incisors, with a mean U1-NA angle of 27.58° and a mean U1-PP angle of 116°. The lower incisors were also inclined lingually, with a mean L1-NB angle of 22.53° and a mean IMPA of 83.13°. Thirty-five of the patients had labial inclination of the upper, and 28 lingual inclination of the lower, incisors. Mean inclinations of upper and lower incisors differed from the normal values, and the inclination of the lower incisors was more likely to be decompensated than that of the upper incisors.     

Ageing and surface EMG activity patterns of masticatory muscles

Summary The purpose of this study was to evaluate the influence of age on the electromyographic activity of masticatory muscles. All volunteers were Brazilian, fully dentate (except for Group I – mixed dentition), Caucasian, aged 7–80, and divided into five groups: I (7–12 years), II (13–20 years), III (21–40 years), IV (41–60 years) and V (61–80 years). Except for Group V, which comprised nine women and eight men, all groups were equally divided with respect to gender (20 M/20 F). Surface electromyographic records of masticatory muscles were obtained at rest and during maximal voluntary contraction, right and left laterality, maximal jaw protrusion and maximal clenching in the intercuspal position. Statistically significant differences (P < 0·05) were found in all clinical conditions among the different age groups. Considerably different patterns of muscle activation were found across ages, with greater electromyographic activity in children and youth, and decreasing from adults to aged people.     

Pharyngeal airway space,hyoid bone position and head posture after orthognathic surgery in Class III patients

Objective:To determine the effect of orthognathic surgery on pharyngeal airway in Class III patients and to (1) compare the results of different surgical techniques, (2) determine the change at the position of the hyoid bone, and (3) evaluate the craniocervical posture changes related to pharyngeal airway change.Materials and Methods:Forty-eight Class III adult patients were included in the study to assess airway space after orthognathic surgery. Nine patients were treated with maxillary advancement, seven patients were treated with mandibular set back, and 32 patients were treated with bimaxillary surgery. Cephalometric records were taken before treatment, after surgery, and about 1 year after surgery (at the end of the treatment).Results:No differences were determined at the position of hyoid bone and craniocervical posture. Nasopharyngeal area was significantly increased in all groups (P < .05). Oropharyngeal area and SPSS and IPS parameters were significantly decreased after mandibular set back operation (P < .05). In bimaxillary and maxillary advancement groups, PPS parameter was significantly increased (P < .01), and IPS parameter was significantly decreased (P < .05). No differences were detected at oropharyngeal and hypopharyngeal areas in bimaxillary and maxillary advancement groups.Conclusion:Different surgical procedures have different effects on pharyngeal airway space.     

髁状突纵形骨折及he夹板治疗时对翼外肌影响的光镜和电镜观察

目的：观察翼外肌下头和嚼肌在髁状突纵形骨折后及舱夹板治疗时的改变。方法：幼年小型猪18头，平均分3组，纵形骨折木治疗组，纵形骨折he夹板治疗组和正常对照组。建立髁状突纵形骨折和he夹板治疗模型。分别在实验后3周、6周和12周取材，进行光镜、电镜观察。结果：骨折后3周，骨折侧的翼外肌下头肌纤维间水肿较重，个别部位出现肌核增多和内移。he夹板治疗组翼外肌肌纤维间的水肿较轻。对侧翼外肌下头以及骨折后6周，12周以及双侧嚼肌肌纤维末见异常。电镜下纵形骨折后3周，可见骨折侧翼外肌下头肌纤维间隙增大，线粒体变圆、增大，数量增多，对侧翼外肌下头以及骨折后6周，12周双侧翼外肌下头以及双侧嚼肌肌纤维未见异常。纵形骨折he夹板治疗组3周可见翼外肌下头肌纤维线粒体轻度变圆、数量稍有增多。结论：幼年小型猪髁状突纵形骨折后，骨折侧的翼外肌下头肌纤维在形态有变化，但翼外肌具有较强的适应能力，he夹板治疗能减轻咀嚼肌的改变。     

Variation in masticatory muscle activity during subsequent,submaximal clenching efforts

In previous studies to the relative contribution of the jaw closing muscles to the maintenance of submaximal clenching levels, a considerable variation in the electromyography (EMG) activities of these muscles during subsequent efforts was found. In this study, it was examined to what extent this variation could be explained by coincidental variations in mandibular positioning. From seven healthy individuals, a total of 90 EMG sweeps was recorded: three conditions (intercuspal position and two types of stabilization appliances) x three clenching levels (10, 30 and 50% of maximum voluntary contraction level) x 10 repetitions. Mandibular position was monitored with a six degrees of freedom opto-electronic jaw movement recording system. Variations in mandibular positioning during subsequent, submaximal clenching efforts explained up to 25% of the variance in the indices that quantify the relative contribution of the jaw closing muscles to the total clenching effort (P=0.000; ANOVA). Only a weak dependency of positioning upon clenching condition was found whereas during higher clenching levels, the positioning effect tended to be smaller than during lower levels. In conclusion small, coincidental variations in mandibular positioning during subsequent clenching efforts partly explain the variance in EMG activity of jaw closing muscles, especially at lower clenching levels.     

Influence of masticatory muscle pain on electromyographic activities of cervical muscles in patients with myogenous temporomandibular disorders

The present study tested the hypothesis that the resting electromyographic (EMG) activities of sternocleidomastoid and trapezius muscles of myogenous temporomandibular disorder (TMD) patients would be significantly greater than healthy individuals. Eight masticatory muscle pain patients without disc interference disorders (DID) and 30 patients with DID along with 41 matched control subjects were included in the study. The resting EMG activities of sternocleidomastoid and trapezius muscles were recorded with a portable EMG machine. Pain intensities described over the muscles were recorded with a 100 mm visual analogue scale. The two groups of patients had significantly higher resting activities compared with control subjects. Patients (in both groups) who had pain in sternocleidomastoid and trapezius muscles reported significantly higher resting activities in the respective muscles than patients who were free of pain and the controls. The presence of pain over the examined muscles showed significant association with the myogenous TMDs without DID. The observed association of the cervical muscles with myogenous TMDs is expected to be a result of functional link between masticatory and cervical muscles. The present findings suggest that the myogenous TMDs without DID could be a distinct sub-group that can be a part of broader regional or generalized diseased entity.