Electromyographic activity of frontalis and sternocleidomastoid muscles in patients with temporomandibular disorders

Little is known of the effects of an interocclusal appliance on the activity of craniocervical muscles in patients with temporomandibular disorder. The bilateral electromyographic activity of the frontalis muscle and sternocleidomastoid muscle were assessed in 10 patients with temporomandibular disorders and eight gender, age and dentally matched asymptomatic control subjects during rest and different clenching tasks with or without an interocclusal appliance. Clenching significantly increased both frontalis and sternocleidomastoid activity from rest. Clenching with an interocclusal appliance, as compared with clenching alone, also significantly reduced frontalis activity in both groups, but not for sternocleidomastoid. Increased electromyographic activity of these muscles may represent co-activation of the craniocervical musculature during clenching.     

A critical evaluation of orthopedic interocclusal appliance therapy: design, theory, and overall effectiveness

Orthopedic interocclusal appliances have been evaluated in a number of research papers and clinical reports over the years. Various theories have been proposed about the method of action of the different appliances, but at present no conclusive controlled testing of these theories has occurred. Certainly, when the potential influence of the nonspecific treatment factors is considered, as well as those cognitive awareness factors common to all appliances, the use of "symptom improvement" as the definitive proof of the need for mandibular realignment or repositioning must be questioned. Specific, well-controlled research using more quantifiable measures of the treatment effect is necessary to make valid comparisons between the different therapeutic approaches. The full-arch occlusal stabilizing appliance is the design that has the most valid evidence about its effectiveness. Partial coverage interocclusal appliances have significant irreversible complications with tooth intrusion or eruption when used on an extended basis. There is little or no experimental support at present about repositioning, realignment, and pivot appliances and their effectiveness. Therefore, these appliances must be considered experimental treatments. When used to treat TM dysfunction in a program along with other methods, such as occlusal adjustments, and prosthetic care, the effectiveness of this treatment method is between 70% and 90%. As a general approach to managing TM pain and dysfunction, interocclusal appliances appear to be a highly effective, commonly used method.     

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).     

Interocclusal appliances--indications and clinical routines in general dental practice in Sweden

The aim of this study was to analyse what kind of interocclusal appliances that are used in general dental practice in Sweden, the indications for such treatment, to what extent a clinical status is recorded before treatment, as well as the routines for evaluation of treatment results. The study was a retrospective analysis of patient records from 320 adult patients who had been treated by general dental practitioners in the Public Dental Service in Sweden. For comparison a group of 88 consecutive patients who had received interocclusal appliance therapy at a specialist clinic was used. The most common indication for treatment with hard acrylic stabilisation appliances, as well as with soft appliances, was occlusal wear due to tooth grinding.The second most common indication for treatment with hard acrylic stabilisation appliances was pain from masticatory muscles, while the second most common indication for soft appliances was tension-type headache. Treatment with soft appliances was more often combined with other treatment modalities compared to treatment with hard acrylic stabilisation appliances. Large variations were found between the 3 general dental clinics and the specialist clinic in respect of treatment indications, combinations with other treatment modalities, recording of clinical findings, follow-ups and evaluation of treatment results. General conclusion should, however, be made with caution due to the risk of selection bias. From the results of this study it is obvious that treatment with soft appliances is common in general dental practice in Sweden, despite the lack of scientific support for their efficacy, as well as effectiveness, compared to hard acrylic stabilisation appliances. There is an obvious need for investigations of the decision-making processes among dentists when performing treatment with interocclusal appliances, as well as for randomised controlled studies concerning efficacy and effectiveness of soft appliances.     

COMPARATIVE EVALUATION OF THE EFFICACY OF OCCLUSAL SPLINTS FABRICATED IN CENTRIC RELATION OR MAXIMUM INTERCUSPATION IN TEMPOROMANDIBULAR DISORDERS PATIENTS

Fabrication of occlusal splints in centric relation for temporomandibular disorders (TMD) patients is arguable, since this position has been defined for asymptomatic stomatognathic system. Thus, maximum intercuspation might be employed in patients with occlusal stability, eliminating the need for interocclusal records. This study compared occlusal splints fabricated in centric relation and maximum intercuspation in muscle pain reduction of TMD patients. Twenty patients with TMD of myogenous origin and bruxism were divided into 2 groups treated with splints in maximum intercuspation (I) or centric relation (II). Clinical, electrognathographic and electromyographic examinations were performed before and 3 months after therapy. Data were analyzed by the Student''s t test. Differences at 5% level of probability were considered statistically significant. There was a remarkable reduction in pain symptomatology, without statistically significant differences (p>0.05) between the groups. There was mandibular repositioning during therapy, as demonstrated by the change in occlusal contacts on the splints. Electrognathographic examination demonstrated a significant increase in maximum left lateral movement for group I and right lateral movement for group II (p<0.05). There were no significant differences (p>0.05) in the electromyographic activities at rest after utilization of both splints. In conclusion, both occlusal splints were effective for pain control and presented similar action. The results suggest that maximum intercuspation may be used for fabrication of occlusal splints in patients with occlusal stability without large discrepancies between centric relation and maximum intercuspation. Moreover, this technique is simpler and less expensive.     

The relationship between signs and symptoms of temporomandibular disorders and bilateral occlusal contact patterns during lateral excursions

The relationship between signs and symptoms of temporomandibular disorders (TMD) and bilateral occlusal contact patterns was investigated in 143 TMD patients (mean age: 34·0 ± 15·9 years; 38 male and 105 female). In addition to an interview regarding chief complaints and accompanying symptoms various muscles and the temporomandibular joints were palpated bilaterally and occlusal analyses were made. Only 5 out of 108 paired variables were found to be significantly associated by using the chi‐squared test. Medial pterygoid muscle pain on palpation showed significant associations with the occlusal contact pattern ( P < 0·005), especially working side contacts (interocclusal tooth contacts on the working side) ( P < 0·005), during contralateral excursions; sternocleidomastoid muscle pain on palpation showed a significant association with balancing side contacts (interocclusal tooth contacts on the balancing side) during ipsilateral excursions P < 0·05); shoulder stiffness and pain in the eye showed significant associations with balancing side contacts during contralateral excursions ( P < 0·05). The results show only a weak relationship between some TMD symptomatology and bilateral occlusal contact patterns during lateral excursions. The findings suggesting the specific laterality of a few TMD signs and symptoms associated with particular occlusal contacts may deserve closer case–control study.     

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.     

A critical evaluation of orthopedic interocclusal appliance therapy: effectiveness for specific symptoms

This paper reviews the effectiveness of occlusal splints on specific symptoms that are often associated with TM disorders. The research has shown the clicking TMJ is sometimes helped but not cured by the traditional stabilization interocclusal appliance and that TMJ clicking is the least responsive to treatment. Questions have been raised about the need to specifically treat the clicking joint; more research on this issue is necessary. Painful TMJs have been shown to respond to occlusal appliance therapy, but questions still exist about the effectiveness of interocclusal appliances for this symptom. There is little scientific proof available about the ability of splints to effectively slow down or reverse degenerative TMJ changes that are evident on radiographs. Masticatory muscle pain is by far the symptom that has the best experimental evidence to support occlusal splints as a highly effective method of treatment. These changes are probably mediated via an alteration in the patient's muscle activity patterns. Those patients with more severe symptoms are less likely to be helped with splints as a sole treatment modality. The effect of occlusal appliances in muscle trismus has been discussed but not effectively evaluated in the literature. Occlusal splints have been shown to have a distinct influence on improving mandibular muscle coordination. Inter-occlusal splints are a commonly used method of controlling attrition and adverse tooth loading, and few questions have been raised in the literature about this therapeutic application.     

Efficacy of treatment with hard and soft occlusal appliance in TMD

Temporomandibular disorders (TMD) include clinical disorders involving the masticatory muscles, the temporomandibular joints (TMJ) and the adjacent structures. TMD was recognized as a main source for pains in the orofacial area, which are not caused from dental origin, and is defined by the American Academy of Orofascial Pain (AAOP) as a sub-group within the frame of musculoskeletal disorders. The main etiology for TMD has not been found yet. The customary treatments for this disorder include treatment with occlusal splints, physiotherapy, medicaments, behavioral-cognitive treatment, hypnosis, acupuncture and surgery that should be considered only if all conservative treatments were unsuccessful. Occlusal splint is the most common and efficient treatment for TMD patients proved by many studies with a successful rate of 70-90%. The following article reviews the different opinions in the treatment of TMD with special attention to hard and soft occlusal appliances. Based upon much research, and despite the many disagreements regarding its efficacy, the hard splint is a customary application which has the most successful outcome in patients who suffer from functional disorders of the masticatory system. The stabilization splint has an important benefit for being a non-penetrating and reversible appliance. However, despite this, the dentist should evaluate the joint or muscular problem, and seriously consider the various available treatments before deciding to use the appliance as a means of treatment.     

Occlusal stabilization appliances. Evidence of their efficacy.

BACKGROUND: There is substantial controversy regarding the value of occlusal appliances for managing temporomandibular joint disorders. This article specifically assesses whether the evidence is sufficient to judge occlusal appliances as being efficacious for the management of localized masticatory myalgia, arthralgia or both. A major confounder is that few studies have measured or evaluated whether subjects had strong, ongoing parafunctional activity (such as clenching or grinding) and whether appliances influenced this behavior. LITERATURE REVIEWED: The authors evaluated four placebo-controlled studies, several randomized wait-list controlled studies and several random-assignment treatment-comparison studies. Data from the wait-list condition studies vs. those from the occlusal appliance condition studies consistently suggested that the latter treatment's effect on patient symptom level is far more than that of no treatment on a wait-list group's condition. In contrast, the studies on placebo-controlled vs. occlusal appliance studies yielded a mix of data: two showed a positive benefit of occlusal vs. nonoccluding appliances, and two showed a null effect or no difference. CONCLUSIONS: Considering all of the available data (pro and con), the authors conclude that the use of occlusal appliances in managing localized masticatory myalgia, arthralgia or both is sufficiently supported by evidence in the literature. CLINICAL IMPLICATIONS: The mechanism of action by which occlusal appliances affect localized myalgia and arthralgia probably is behavioral modification of jaw clenching. However, if the behavior continues unabated, even the best splint will not work.     

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。     

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.     

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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.     

Counselling and self‐management therapies for temporomandibular disorders: a systematic review

The aim of this review was to investigate the effectiveness of counselling and other self‐management‐based therapies on muscle and temporomandibular joint (TMJ) pain relief and increasing the functional abilities of patients with temporomandibular disorders (TMD). A systematic literature review was conducted by three independent reviewers and included articles published up to 2012. PubMed and Cochrane Library electronic databases were used in addition to hand‐searching to assess clinical outcomes for counselling and self‐management approaches for TMD treatment. The review yielded 581 records that were narrowed down to 7. All included studies were classified as blind‐randomized controlled clinical trials. The selected articles analysed revealed that counselling was able to improve tenderness upon masticatory muscle palpation and maximum mouth opening with and without pain in patients with TMD, with similar results to those of interocclusal appliances approaches. Thus, counselling‐ and self‐management‐based therapies could be considered a conservative low‐cost and beneficial treatment alternative for treating TMD to potentially improve psychological domains and remove harmful behaviours for the control of the signs and symptoms of TMD.     

An electromyographic study of masseter and anterior temporalis muscles in extra-articular myogenous TMJ pain patients compared to an asymptomatic and normal population

The purpose of this study was to evaluate the effectiveness of the therapy with a centric relation stabilization appliance (CRSA) in patients with temporomandibular disorders of myogenous origin by electromyography and compare the results with two asymptomatic control groups. Three groups of 20 patients each were selected for the study. Electromyography (EMG) of masseter and anterior temporalis muscles was performed during mandibular rest position. In the treated group, the occlusal appliance reduced the electrical activity of the analyzed muscles at right and left sides (p<0.0001), and equilibrated muscular activity between right and left sides (p<0.0001), reaching values close to the control groups. Although there was not a statistically significant difference, the normal control group presented lower EMG values than control group II and presented the lowest asymmetry index of all subjects. More than 85% of all subjects, including the controls, demonstrated a statistically significant temporal anterior activity prevalence (p<0.0001). Treatment with the CRSA reduced the activity index, although the prevalence of the temporal muscle over the masseter was maintained. The significant laterodeviating (torque) effect found in the temporomandibular disorder patients was reduced after treatment. No side prevalence was found in the control groups.     

Habitual mastication in dysfunction: a computer-based analysis

To study the different parameters of habitual mastication in stomatognathic dysfunction, mandibular movements and electromyographic activity of the elevator muscles were recorded during three chewing sequences in 86 dysfunctional subjects. The Dysfunction Index system was used to treat two subgroups, patients with severe temporomandibular joint impairment and patients with severe muscle dysfunction. Data on the different parameters of mastication from the single patients, the whole group, and the two subgroups were statistically assessed and compared with those from 12 normal individuals. The following conclusions were drawn. (1) In dysfunctional patients the normal symmetrical and balanced distribution of the chewing cycles is lost and movements are more restricted. (2) The electromyographic data show marked alterations with a tendency to reduce or suppress the isometric phase of contraction during closing in the temporomandibular joint patients. This can be viewed as a defensive mechanism of the impaired system. (3) The data at hand are helpful in explaining some of the mechanisms that lead to muscle pain in dysfunctional patients.     

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.     

Vertical dimension: A research and clinical analysis

Vertical dimension has been defined in relation to the clinical rest position of the mandible, the vertical dimension of occlusion, and the interocclusal space between the two. The physiologic rest position has been attributed to three possible mechanisms: postural tonicity of the muscles, myotatic (stretch) reflexes, and gravity-elasticity, and/or a combination of all three. There is general agreement that it varies due to head position and many other extrinsic and intrinsic stimuli.The myotatic (stretch) reflex is produced by stimulation of the stretch receptors in the elevator muscles producing a simple two-neuron reflex arc which causes reflex muscle contraction. Its function is to give proprioceptive information to the central nervous system concerning position and movement. The proprioception of mandibular position is determined for the most part by the joint receptors, muscle spindles, pressoreceptors (in the periodontal membrane), and exteroceptors in the oral mucosa.Minimal EMG activity has been demonstrated at the clinical rest position and slightly beyond, at an increased vertical dimension which eliminates the interocclusal space. However, experimental evidence has been shown with adult monkeys that long-term increases in the vertical dimension of occlusion result in intrusion of the posterior teeth with the return almost to the original vertical dimension of occlusion. Several clinical examples of intrusion of the posterior teeth were shown when long-standing occlusal splints were used. Since both occlusal adjustment and vertical dimension increases can cause a reduction in EMG activity, it is recommended that the treatment of TMJ dysfunction is best accomplished by occlusal correction.A treatment prosthesis is recommended for trismus and/or joint injury but it should be accomplished within the interocclusal space. Most treatment prostheses, except those for condylar repositioning, are utilized for the control of symptoms and do not treat the cause of TMJ dysfunction pain.     

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.     

Influence of Different Centric Functions on Electromyographic Activity of Elevator Muscles

This study compares eight different occlusal centric functions with splint contact on different teeth in order to determine their influence on mandibular elevator electromyographic (EMG) activity.

Maxillary occlusal splints were built for eight subjects without craniomandibular dysfunction. Investigators divided each splint into three parts, in order to record different occlusal schemes in the same subject without varying the vertical dimension. EMG activity in the left masseter and anterior temporal muscles was registered during maximum voluntary clenching.

Results showed higher masseter activity with the splint than without, and anterior temporal activity was similar. There was a significant decrease of EMG activity with the anterior section of the splint. There were no significant differences between the remaining centric functions and clenching with the complete splint, except for the centric function with contralateral posterior contact, in which elevator activity was significantly reduced.

Results suggest that bilateral posterior occlusal stabilization is critical for maximum interocclusal force.