The immediate effect of hard and soft splints on the EMG activity of the masseter and temporalis muscles.

The aim of this study was to compare the effects of hard and soft splints on the activity of the anterior temporalis and masseter muscles. Surface EMG recordings were made from these muscles during clenching at 10% of maximum, 50% of maximum and at maximum clench, both before and after insertion of a hard splint. This sequence was then repeated with a soft splint. The relative level of activity in the anterior temporalis and masseter muscles at all three activity levels was quantified by means of an Activity Index, which provides a measure of the balance of activity in the masseter relative to the activity in the anterior temporalis muscle. It was found that hard splints led to a decrease in EMG activity in relation to activity with no splint in both muscles at maximum clench and particularly the anterior temporalis. Soft splints produced a slight increase in activity of both muscles, but particularly the masseter muscle. The Activity Index indicated a shift in the balance of activity away from the anterior temporalis muscles with both splints, particularly at 10% of the maximum clenching level. It is possible that the decrease in activity of the temporalis muscles relative to the masseter muscles may be a factor in the therapeutic effect of both a hard and a soft splint, although the decrease is clearly greater with the hard splint.     

Effect of occlusal splints on the electromyographic activities of masseter and temporal muscles during maximum clenching.

OBJECTIVES: Despite the broad use of occlusal splints in the treatment of temporomandibular disorders, the efficacy of splints is a source of controversy. In this study, the effectiveness of occlusal splints on the electromyographic activity of the masseter and temporal muscles in healthy individuals was investigated. METHOD AND MATERIALS: An occlusal splint was made for 25 healthy individuals. Surface electromyographic recordings were done during maximum clenching without the splint and immediately after application of the splint. The relative level of activity in the masseter and temporal muscles was quantified by means of activity index. Paired t test and Wilcoxon signed-rank tests were used for data analysis. RESULTS: The mean electromyographic activities of masseter and temporal muscles (in mV/s) were 0.7712 and 1.0488 without the splint and 0.8396 and 0.9276 immediately after application of the splint. There was no significant difference between the electromyographic activities of both muscles before and after insertion of the splints. The activity index increased after application of the occlusal splints. This increase was also insignificant. CONCLUSION: Immediate application of occlusal splints has no significant effect on the activity of masseter and temporal muscles. It could decrease the relative activity of the temporal to the masseter muscle (increasing the activity index).     

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??Objective??To observe and analyze the clinical effect of the stabilization splint and the occlusal reconstruction treatment on patients with masticatory muscle pain. Methods??Totally 20 patients with masticatory muscle pain who visited General Department and Prosthodontics Department of Affiliated Stomatology Hospital of China Medical University from September 2016 to May 2018 were given the stabilization splint therapy and the occlusal reconstruction treatment. Analyze the visual analogue scale??VAS????electromyographic pattern and Friction temporomandibular joint dysfunction index before treatment??T0????three months after the stabilization splint therapy??T1????when occlusal reconstruction was finished??T2??and three months later??T3??. Results??Statistical analysis showed that VAS??the electromyographic signal of anterior temporalis and masseters in mandibular postural position??asymmetry index of masseter muscles and temporalis muscles and Friction temporomandibular joint dysfunction index in T1??T2 and T3 were significantly lower than those in T0??P < 0.05??. The electromyographic signal were dramatically increased in intercuspal position ??P < 0.05??. No significant difference was shown in VAS??the electromyographic signal of anterior temporalis and masseters??asymmetry index of masseter muscles and temporalis muscles??or Friction temporomandibular joint dysfunction index in T1??T2 and T3??P > 0.05??. Conclusion??The stabilization splint therapy is effective on patients with masticatory muscle pain??and the occlusal reconstruction treatment is able to maintain these effects.     

稳定型咬合板配合咬合重建治疗咀嚼肌疼痛疗效评价

目的　评价稳定型咬合板配合咬合重建治疗咀嚼肌疼痛的疗效。方法　选取2016年9月至2018年5月于中国医科大学附属口腔医院综合科及修复一科行稳定型咬合板及咬合重建序列治疗的咀嚼肌疼痛患者20例。分析治疗前（T0期）、佩戴咬合板3个月后（T1期）、咬合重建完成即刻（T2期）及咬合重建完成3个月后（T3期）的疼痛视觉模拟评分（visual analogue scale,VAS）、肌电图及Friction颞下颌关节紊乱指数的变化。结果　T1、T2、T3期患者VAS评分、下颌姿势位时颞肌咬肌的肌电活性、颞肌咬肌不对称指数及Friction颞下颌关节紊乱指数均较T0期显著降低,差异有统计学意义（均P < 0.05）;最大紧咬牙时颞肌咬肌的肌电活性较T0期明显增高,差异有统计学意义（均P < 0.05）。T1、T2、T3期患者之间的VAS评分、颞肌咬肌的肌电活性、颞肌咬肌不对称指数及Friction颞下颌关节紊乱指数差异无统计学意义（均P > 0.05）。结论　稳定型咬合板可有效治疗咀嚼肌疼痛,咬合重建序列治疗能很好维持其疗效。     

咬合板高度对TMD患者咀嚼肌肌电的影响

目的:研究不同高度的咬合板对颞下颌关节紊乱病(TMD)患者颞肌前束、咬肌肌电的影响。方法:73例TMD患者随机分为3组,戴用不同高度咬合板使咬合距离分别增加3mm、5mm、7mm,比较分析戴板前和戴板后即刻测量的双侧颞肌前束(TA)和咬肌(MM)肌电电位。结果:在静息及紧咬状态下,戴用不同高度咬合板即刻测量的TA及MM肌电电位均明显低于戴板前的测量值(P<0.05);紧咬状态下5mm和7mm咬合板对MM肌电电位的降低程度显著高于3mm组。结论:咬合板是治疗肌功能紊乱的有效方法。高度为5mm和7mm的咬合板降低咀嚼肌肌电的能力较3mm咬合板更强。     

Effects of interocclusal appliances on EMG activity during parafunctional tooth contact

To test the hypothesis that a flat plane interocclusal appliance affects the electromyographic (EMG) activity of the temporalis and masseter muscles in pain-free individuals, maxillary splints were fabricated for 20 individuals who reported no history, signs or symptoms of myofascial pain or arthralgia as determined by two trained, independent examiners. Subjects were instructed to establish light tooth contact, maximum clenching, and moderate clenching with/without the splint in place (as determined by random assignment) while EMG data from the left and right temporalis and masseter muscles were recorded. A 5-min biofeedback training session to relax the masticatory muscles was followed by a repetition of the tooth contact/clenching tasks with/without the splint in place. With the splint in place, the activity of the temporalis muscles decreased for all tasks, significantly for the left and right temporalis under maximal clenching and for the right temporalis under moderate clenching. In contrast, the activity of the masseter muscles increased under light and moderate clenching (significantly for the left masseter under moderate clenching) and decreased slightly under maximal clenching. The effectiveness of interocclusal appliances may be due to mechanisms other than redistribution of adverse loading.     

Immediate electromyographic response in masseter and temporal muscles to bite plates and stabilization splints

Abstract— The immediate influence on masticatory muscle activity of bite plates and stabilization splints was investigated in control subjects and patients with craniomandibular disorders. Electromyographic surface recordings were performed from the masseter and temporal muscles bilaterally with and without the appliances in situ. In the rest position, no significant change in average activity was registered in any muscle with either appliance. Activity during maximal biting on stabilization splints was not different from that without the appliance while bite plates caused a decrease in activity in both muscles in both groups. The reduced maximal activity was probably due to the smaller number and exclusively anterior positioned occlusal contacts on the bite plate.     

Immediate electromyographic response in masseter and temporal muscles to bite plates and stabilization splints

The immediate influence on masticatory muscle activity of bite plates and stabilization splints was investigated in control subjects and patients with craniomandibular disorders. Electromyographic surface recordings were performed from the masseter and temporal muscles bilaterally with and without the appliances in situ. In the rest position, no significant change in average activity was registered in any muscle with either appliance. Activity during maximal biting on stabilization splints was not different from that without the appliance while bite plates caused a decrease in activity in both muscles in both groups. The reduced maximal activity was probably due to the smaller number and exclusively anterior positioned occlusal contacts on the bite plate.     

Effects of occlusal splints on the asymmetry of masticatory muscle activity during maximal clenching

summary The effects of stabilization splints on the electromyographic activity patterns of the masseter and anterior temporal muscles during maximal clenching in healthy subjects and subjects with different types of stomatognathic dysfunction syndrome were investigated. No marked effect of splints on the asymmetry of muscle activity during bilateral clenching was revealed immediately after splint insertion. During unilateral clenching in the intercuspal position (ICP), the relative asymmetry index (rAI) of the masseter muscles, detecting the imbalance of left and right muscular activity, was significantry increased. The use of splints suppressed the asymmetry of masseter muscle activity during unilateral clenching. This result suggests that the use of a splint is a method of suppressing clench-caused aggravation of stomatognathic dysfunction in the presence of an imbalance between left and right muscle activities.     

Bite plates and stabilization splints in mandibular dysfunction. A clinical and electromyographic comparison

Twenty patients with mandibular dysfunction, all women, aged 17-41 years, were randomized for treatment with either a bite plate with a frontal plateau or a full-coverage stabilization splint. The occlusal appliances were used at night for 6 weeks to compare clinical and electromyographic effects (EMGs). Integrated EMGs were recorded bilaterally from the anterior and posterior parts of the temporal muscle and the masseter muscle in the rest position and during gentle and maximal biting before and after treatment without the appliances in situ. Initially recorded EMG activity in the temporal muscle was correlated to signs of dysfunction in the rest position. Compared with previously investigated healthy subjects, the patients had lower EMG activity in the anterior part of the temporal muscle and in the masseter muscle during maximal biting. Use of occlusal appliances at night for 6 weeks did not change the EMG activity in the rest position or during maximal biting. The clinical signs improved, significantly in the splint group. The subjective symptoms improved in both groups, significantly more in the splint group.     

Masticatory muscle activity in different jaw relations during submaximal clenching efforts.

The EMG activities of the masseter muscles and the anterior and posterior parts of the temporalis muscles were investigated in different vertical and sagittal jaw relations. Surface EMG recordings were made. Relative muscle activities were quantified by means of the Activity Index and the Asymmetry Index. Ten subjects with a healthy masticatory system were asked to clench at 10% and 50% of their maximum voluntary clenching level. Registrations were made during clenching in the intercuspal position, on a thin stabilization splint (SSP, 1-2 mm increase of vertical dimension at first molar), on a thick stabilization splint (3 mm thicker at the incisal edge relative to SSP), and on a protrusive re-positioning splint (3 mm protrusive to SSP). The masseter EMG amplitudes were the same for all the jaw positions investigated. However, at the 10% clenching level, the temporalis muscle activity decreased after the vertical dimension was raised and decreased further after the mandible was protrusively positioned (p less than 0.01). An independent function for the posterior and the anterior parts of the temporalis muscle was not found in any of the intermaxillary jaw relations investigated. At the 50% clenching level, a decrease in anterior temporalis muscle activity was observed only with the protrusive position in relation to the other three positions. Also at this level, the index relating the activity of the anterior to that of the posterior part of the temporalis muscle was not different between jaw positions. Raising the vertical dimension and protrusive positioning of the mandible decrease the activity of the temporalis muscles. This may be a factor related to the therapeutic effect of the stabilization splint in the treatment of craniomandibular disorder patients.     

A Comparison of Electromyographic Activity Between Anterior Repositioning Splint Therapy and a Centric Relation Splint

The purpose of this study was to compare the electromyographic activity of masticatory muscles (temporal and masseter) with the use of an anterior repositioning splint and a centric relation superior repositioning splint. Twenty-six consecutive patients, who referred with the chief complaint of temporomandibular pain and/or headache were selected from one of the author's practices. All these subjects were diagnosed as having internal derangement of the temporomandibular joint. Ten normal subjects were used as controls. Surface electromyographic recordings were taken of each subject prior to the beginning of clinical therapy for the patients. The results show significantly less masseter and temporal muscle activity with anterior repositioning splint therapy compared to the centric relation superior repositioning splint therapy.     

稳定性咬合板治疗颞下颌关节紊乱病的咀嚼肌肌电图研究

目的：通过对颞下颌关节紊乱病（Temporomandibular disorders,TMD）患者进行稳定性咬合板的可逆性咬合治疗,然后利用肌电图仪测量治疗前后患者的咀嚼肌（TA和MM）的肌电情况,分析探讨用稳定性咬合板对颞下颌关节紊乱病患者咀嚼肌肌电图的影响。方法：选取来我院就诊的10例咀嚼肌功能紊乱患者,在稳定性咬合板治疗前和治疗后3个月时,分别用肌电图仪对其咀嚼肌（TA和MM）进行肌电检查,并通过比较治疗前后的咀嚼肌活动不对称指数情况。结果：戴入稳定性咬合板3个月后,颞肌前束与咬肌的MPP和ICP高电位降低（P〈0.05）;最大紧咬时双侧咀嚼肌总体不对称性指数（Astot）、双侧颞肌不对称性指数（ASTA）和双侧咬肌不对称性指数（ASMM）均降低（P〈0.05）。结论：颞下颌关节紊乱病患者通过稳定性咬合板进行咬合治疗后,使患者双侧咀嚼肌的MPP和ICP高电位较治疗前有明显的降低,最大紧咬时双侧咀嚼肌活动不对称性得到明显的改善。     

Electromyography of masticatory muscles in three jaw registration positions

The purpose of this study was to investigate whether anteroposterior changes in mandibular position affect masticatory muscle activity. The electromyographic (EMG) activity of masticatory muscles during full and partial (10%) clenching in three mandibular bite registration positions--retruded contact position (RCP), intercuspal position (IP), and muscular position (MP)--was studied. Three groups of subjects with different ranges of anteroposterior positioning of the condyles were evaluated (normal occlusion, Class II, Division 2 malocclusion, and dual bite malocclusion). A posterior stabilizing splint for each registration position was made. EMG data were obtained from three bilateral muscles (masseter, anterior temporal, and posterior temporal). Clenching in the RCP elicited the lowest masseter muscle activity during full clenching, and the highest anterior temporal and posterior temporal muscle activity during partial clenching. If the relationships of the masticatory muscles are analyzed through a ratio that represents the interaction between biting and positioning muscles (masseter/posterior temporal muscle ratio), the RCP as compared with other positions had the lowest ratio. The RCP required more positioning muscle activity and permitted less biting muscle activity. There was no significant difference in the muscle activity between the IP and MP registrations. Small changes in jaw position (anterior to RCP) are not critical for the masticatory apparatus provided there is good intercuspation. The results of this investigation suggest that intercuspation in RCP is not the optimal position.     

Comparative electromyographic study of bite plates and stabilization splints

The object was to study any influence on the integrated electromyographic activity in the masseter and temporal muscles of two types of occlusal appliances. Seventeen healthy subjects wore a bite plate with a frontal plateau and a full coverage stabilization splint at night, each for 1 wk. The EMG activity was recorded without appliances in situ, in the rest position, and during gentle and maximum biting before and after the use of the different appliances. After use of the bite plate, the EMG activity was not significantly different at any tested level. After use of the splint, the activity in the rest position was significantly lower in the anterior and posterior parts of the temporal muscles. The EMG activity was significantly lower in the rest position in both parts of the temporal muscle after use of the splint than after use of the bite plate. In a control group of eight subjects in whom no appliances were used, the EMG activity did not change significantly between the initial and 1- or 5-wk recordings. Thus, the occlusal design of the appliances seems to be of importance for the influence on the EMG activity in the masticatory muscles, at least in healthy subjects.     

Relation between cervical posture on lateral skull radiographs and electromyographic activity of masticatory muscles in caucasian adult women: a cross-sectional study

The aim of this study was to evaluate the association between cervical posture on lateral skull radiographs and surface electromyographic recordings (sEMG) of head and neck muscles. The sample comprised 40 Caucasian adult females, average age 26.8 (20-48); lateral skull radiographs were obtained in natural head position (mirror position). sEMG activity was bilaterally investigated for the following muscles: masseter, anterior temporalis, digastric, posterior cervical, sternocleidomastoid and upper and lower trapezius. All muscles were monitored at rest and during maximal voluntary clenching (MVC). A Pearson's correlation coefficient revealed significant correlations (P < 0.01) between cranio-cervical angulations and sEMG activity of masseter, digastric, lower trapezius, during MVC and anterior temporalis at rest. Significant correlations (P < 0.01) were also found between cervical lordosis angle and sEMG activity of masseter (during MVC) and lower trapezius (at rest). In view of transversal method, no conclusion was possible about the mechanism concerning these results. Future longitudinal studies should be directed to understand the extent of environmental and genotype influences by masticatory muscle activity on cervical posture.     

Reliability of electromyographic activity vs. bite-force from human masticatory muscles

The reproducibility of electromyographic (EMG) activity in relation to static bite-force from masticatory muscles for a given biting situation is largely unknown. Our aim was to evaluate the reliability of EMG activity in relation to static bite-force in humans. Eighty-four subjects produced five unilateral static bites of different forces at different biting positions on molars and incisors, at two separate sessions, and the surface EMG activities were recorded from temporalis, masseter, and suprahyoid muscles bilaterally. Intraclass correlation coefficients (ICCs) were determined, and an ICC of ≥ 0.60 indicated good reliability of these slopes. The ICCs for jaw-closing muscles during molar biting were: temporalis muscles, ipsilateral 0.58-0.93 and contralateral 0.88-0.91; and masseter muscles, ipsilateral 0.75-0.86 and contralateral 0.69-0.88. The ICCs for jaw-closing muscles during incisor biting were: temporalis muscles, ipsilateral 0.56-0.81 and contralateral 0.34-0.86; and masseter muscles, ipsilateral 0.65-0.78 and contralateral 0.59-0.80. For the suprahyoid muscles the 95% CIs were mostly wide and most included zero. The slopes of the EMG activity vs. bite-force for a given biting situation were reliable for temporalis and masseter muscles. These results support the use of these outcome measurements for the estimation and validation of mechanical models of the masticatory system.     

Short-term effect of a stabilization splint on the asymmetry of submaximal masticatory muscle activity

Ten healthy subjects continuously wore equilibrated maxillary full-arch stabilization splints in the retruded position for 7 days. The muscular activity balance of the masseter muscles during submaximal isometric clenching at 10% and 50% of the maximum voluntary contraction (MVC) did not change immediately on insertion of the splint, but was improved at the 50% level after 7 days (P less than 0.05). While the muscular balance of the anterior temporal muscles was not affected, either immediately on splint insertion, or after wearing it for 7 days, temporal muscle activity at 10% of the MVC was greater on the side to which the mandible moved from the retruded contact position (RCP) to the inter-cuspal position (ICP), both before (P less than 0.025) and after (P less than 0.01) wearing the splint. Splint removal after 7 days resulted in increased awareness of interferences in the ICP and increases in masseter muscle asymmetry (10%, P less than 0.025; 50%, P less than 0.05) when the electromyograms in the ICP after splint removal were compared with those on the stabilization splint before removal. After wearing the splint, the masseter muscle activity at the 10% level was greater on the side where premature contacts were present in the RCP (P less than 0.01). The use of masticatory muscle asymmetry indices in the evaluation of splint treatment for craniomandibular dysfunction is indicated since submaximal masticatory muscle activity is related to occlusal stability, premature contacts in the RCP and the direction of lateral slides from the RCP to the ICP.     

Modulation of masticatory muscle activity by tongue position

The purpose of this study was to test whether the tongue position affects the electromyographic (EMG) activities of masticatory muscles. We recorded the EMG activities of the masseter and anterior temporalis muscles in 10 skeletal Class I adults. Tongue position was monitored by two pressure transducers embedded in the midpalatal region and the lingual flange of a custom-made acrylic monoblock. We instructed subjects to assume three different tongue positions: rest, superior, and anterior. Friedman's test and Sheffe's F-test were used to statistically examine differences in muscle activities induced by changes in tongue position. Significant differences were found in masseter muscle activity between the rest and anterior positions and in anterior temporalis muscle activity between the rest and both the anterior and the superior tongue positions. We concluded that masticatory muscle activity is affected by tongue position.     

牙齿病理性磨损充填治疗的临床效果研究

目的观察尚未出现牙髓症状的牙齿病理性磨损充填治疗的临床效果。方法选择牙列完整、后牙骀面有病理性磨损且具有充填空间的患者10例，患牙48颗，均无牙髓症状。使用后牙树脂充填后，比较治疗前、治疗后3个月和1年时，患者主观感觉和咀嚼功能（咬合力、咀嚼效率和咬肌肌电活动）的变化，观察树脂充填的临床效果（美国公共健康部评价系统）。结果患牙经充填治疗后患者临床症状消失，咬合力增加（P〈0．05），咀嚼效率明显提高（P〈0．01），治疗前后下颌息止位、大力咬合时、咀嚼运动时，颞肌前束和咬肌的活动强度、活动对称性及用力方式差异均无统计学意义（P〉0．05）；治疗后3个月和1年时复查，48颗后牙树脂充填体各项指标A级率为100％。结论对后牙骀面尚未出现牙髓症状的病理性磨损用树脂进行充填是一种有效的治疗方法，可以解除患者的临床症状，减缓磨损的发展，增加咀嚼效率及患牙咬合力。