Postural and dynamic masseter and anterior temporalis muscle EMG repeatability in serial assessments.

Electromyographic (EMG) assessment has been used as a non-invasive tool to objectively assess muscle function, although with controversial research and clinical potential. The aim of this study was to assess within-, inter-subject and between-day repeatability of serial EMG recordings. The study sample included 10 asymptomatic subjects with no history of temporomandibular disorders or muscle parafunctions. Bilateral masseter and anterior temporalis muscle EMG parameters were assessed in two standardized serial recordings (day 1 to day 2) using a portable EMG equipment (ME 6000 recorder, Mega Electronics, Kuopio, Finland). The functional tasks included postural/resting activities as pre- and post-recording series of 30 s each and jaw opening/closing, intercuspal and maximal voluntary clenching activities of 5 s, repeated three times. The assessed EMG parameters included the mean amplitude, s.d. and error. In addition, the power spectrum EMG parameter assessment included the median power frequencies and the averaged EMG spectrum data values. The results of the intraclass correlation coefficient analysis indicated reliability for nearly all of the intercuspal and all clenching EMG amplitude and power spectrum parameters. This was complemented by the repeated measures anova and post hoc analyses that indicated non-significant differences between day 1 and 2 in task- and muscle-related analyses. Most variability was noted in postural and some in opening/closing tasks. In conclusion this study assessed the reliability, repeatability and limitations of postural and various dynamic masseter and temporalis EMG recordings for serial assessment.

Temporomandibular disorders: a critical review of the nature of pain and its assessment.

Temporomandibular disorders is a common form of chronic pain affecting the head, face, and jaw. The distinguishing symptoms of this disorder include pain and impairment of the masticatory function, and frequent display of symptoms, ranging from aches in the head, neck, ears, and eyes, to atypical toothaches, throat symptoms, and occlusal changes. It is recognized that pain is a complex, multifactorial experience including not only sensory dimensions, but also affective and cognitive factors. Recent recommendations regard temporomandibular disorders as a dual-axis disorder with physical and psychologic dimensions, but little research has incorporated measures of multidimensional pain characteristics in the assessment of temporomandibular disorders. This article is a review of the literature on the psychophysiologic factors contributing to temporomandibular disorders and its limitations. Recommendations for future research are also given.

Temporomandibular disorders. Part I: A comparison of symptom profiles in Australian and Finnish patients.

Variability in the assessment methods of patients seeking treatment for musculoskeletal disorders of the masticatory system confounds comparative assessment of different studies. In this study, presenting symptom profiles were assessed in 40 Australian and 42 Finnish patients with temporomandibular disorders. The symptom parameters of these patients were compared with those of 40 Australians reporting acute dental pain and were assessed with reference to response to conservative management. A self-administered anamnestic questionnaire was used in a standard, systematic, and comparative way to assess demographic data, general health status, and symptom parameters according to type, frequency, severity, duration, location, impact on the patients' lives, urgency for need of treatment, and possible initiating factors. It was found that the two nationalities studied had similar presentations of cardinal symptom profiles. Statistically significant differences in major presenting symptoms were found between patients with temporomandibular disorders and those with acute dental pain, but not between patients who responded rapidly as opposed to slowly to conservative therapy. It was concluded that the presenting symptom profiles were similar for the two nationalities and were not related to treatment outcome.

Temporomandibular disorders: Part II. A comparison of psychologic profiles in Australian and Finnish patients.

Recent recommendations regard musculoskeletal disorders of the masticatory system as dual-axis disorders, but little comparative data of psychologic factors across different pain populations are available. In this study, presenting psychologic profiles were assessed in 40 Australian and 42 Finnish patients diagnosed with temporomandibular disorders. Findings were compared with those of a group of Australian patients reporting acute dental pain and with reference to response to conservative management. The psychologic testing instrument incorporated cognitive, motivational/affective, and illness behavior variables, and it was based on validated general pain questionnaires (Coping Strategies Questionnaire and Illness Behavior Questionnaire). This instrument was found internally reliable in the majority of its subscales in the group studies and provided comparable data to other pain populations. Significant differences in the presenting psychologic profiles were found according to nationality, type of pain suffered, and treatment outcome. Affective disturbance, hypochondriasis, lack of cognitive control, and feeling ill with symptoms were identified in discriminant function analysis as potential predictors of treatment outcome, and they correctly classified 79% of the Australian and 87% of the Finnish patients with temporomandibular disorders. It was concluded that psychologic profiles differed in the two nationalities and were related to treatment outcome. The concept of multiaxial assessment was supported.

The effect of interocclusal appliances on temporomandibular joints as assessed by 3D reconstruction of MRI scans.

Magnetic resonance imaging (MRI) enables simultaneous visualization of hard and soft tissues. The aims of the present study were to computer generate three-dimensional (3D) images, reconstructed from MRI scans of normal temporomandibular joints (TMJ), to assess the relative positions of the disc, condyle and articular surface of the temporal bone and to study the effect of two mandibular group function interocclusal appliances (IOAs). Bilateral MRI scans of 2 mm slice thickness were generated for the TMJs of 12 asymptomatic subjects with the image acquisition coils orientated in a corrected oblique sagittal plane. MRI scans were generated for all subjects with 3 mm interincisal distance IOAs, while a subgroup (n = 4) was also scanned with a 5 mm interincisal IOA in situ. An average of 10 slices through each TMJ were generated for the closed mouth and IOA positions. Three-dimensional reconstruction was performed on a 486 IBM compatible computer using a suite of nine programs not commercially available. Three-dimensional images allowed visualization of composite images of joint relationships. Subjective assessment indicated that joint relations in 3D were more informative than multiple separate 2D MRI scans. With the 3 mm IOA in situ, the disc was positioned posteriorly and superiorly to the condyle in three of 12 cases. In four of 12 cases the condyle, and in two of 12 cases both the disc and condyle, were positioned anteriorly and inferiorly. With the 5 mm IOA changes in condyle/disc and condyle/fossa relationships were more variable. It was concluded that 3D images of TMJs enabled the assessment of the positional changes of the condyle/disc and condyle/fossa relationships as altered by IOAs. However, the role of IOAs on the internal arrangements within the TMJ remains variable and is deserving of further study.

Review of clinical EMG studies related to muscle and occlusal factors in healthy and TMD subjects.

Several electronic instruments have been developed as adjuncts to objectively record the dysfunctional features of temporomandibular disorders and to study the effectiveness of various treatment interventions. The aim of this review was to assess the value and contribution of clinical electromyographic research in the understanding of asymptomatic and dysfunctional muscle function and the therapeutic effects of interocclusal appliances. For this purpose MedLine and PubMed searches were conducted with the following main keywords alone and in various combinations: electromyography, muscles of mastication, masseter, temporalis, temporomandibular, TMD, utility, validity, repeatability, rest, postural, vertical dimension, occlusal, splint, treatment. The review includes critical evaluation, discussion and conclusions regarding electromyographic studies in asymptomatic and dysfunctional muscles, rest position, occlusal parameters and interocclusal appliances, as well as a critical summary and proposals for further research. Much of earlier critique of many electromyographic studies still applies regarding comparative sample selections, research designs, analyses and conclusions. The areas not well-understood include normal biological variation, capacity for adaptation, fluctuations regarding the clinical course and multidimensional features of temporomandibular disorders and long-term follow-up data, especially in studies that evaluate the effectiveness of therapeutic measures. Considering the required improvements in technical and research designs features and critical appraisal electromyographic research could have value as an adjunct research tool to study features of craniofacial muscle-related dysfunction. Until electromyographic measures are correlated with other multidimensional, especially subjective and pain-related methods, the clinical use of this method for diagnostic purposes of temporomandibular disorders remains in doubt, and is not at present recommended.

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.

Outcome of therapy in the conservative management of temporomandibular pain dysfunction disorder.

The present study considered predictors of the outcome of treatment for temporomandibular pain dysfunction disorder (TMPD). Thirty-seven patients were assessed with objective and self-report measures of physiological and psychosocial aspects of this disorder at initial assessment and at 6-month follow-up subsequent to conservative physical therapy. Patients were subdivided into slow and rapid responders to conservative physical therapy based on self-reported level of improvement. Measures employed included the Temporomandibular Pain Dysfunction Disorder Questionnaire and the Temporomandibular Pain Dysfunction Disorder Clinical Form. Eighty-one per cent of patients showed a 50% or greater improvement in pain severity at follow-up, with minimal differential changes across the two groups found in the physiological symptoms, while the rapid responding group showed greater improvement in terms of psychosocial factors. These findings indicated that psychosocial factors, particularly coping strategies and illness behaviour, cannot be ignored in the management of TMPD.

Clinical simulation in teaching preclinical dentistry.

Current and projected approaches to dental education have created a wide interest in clinical simulation, and recently there has been a considerable expansion in the availability of experiential learning tools which imitate "real life" clinical conditions in dentistry. These include patient simulation devices such as heads, jaws, teeth and clinical environments, standardized patients, interactive video-discs and computer-based instruction. This paper reviews some of the equipment currently available for simulation of clinical procedures, and assesses the initial experiences and responses of 2nd, 3rd and 4th year undergraduate dental students at The University of Melbourne to case-based simulations in a patient simulator in comparison with preclinical exercises in a traditional bench and manikin laboratory. Student response to teaching and learning in the simulator over a 3-year evaluation period, collected via a student questionnaire was uniformly positive. Students were very enthusiastic about the learning environment and educational approach, preferring it to traditional preclinical laboratory instruction.

A comparison of the effects of group function and canine guidance interocclusal device on masseter muscle electromyographic activity in normal subjects.

This study investigated the role of occlusal balance and canine guidance or group function guidance in masseter muscle function of normal subjects. Two types of interocclusal devices were constructed for each of the 10 subjects. Two ME 1020 EMG analyzers and bipolar Ag/AgCI electrodes were used to record the electromyographic activity of masseter muscles during clenching in centric occlusion, during left and right laterotrusive movements, and during clenching at the extremities of the jaw both with the natural dentition only and with adjusted and intentionally unadjusted interocclusal devices in place. This study demonstrated that there was no difference in masseter muscle electromyographic activity between the use of interocclusal devices designed for canine guidance or for group function guidance in normal subjects. It showed also that altering the occlusal balance significantly reduced muscle activity.

The effect of an interocclusal appliance on bite force and masseter electromyography in asymptomatic subjects and patients with temporomandibular pain and dysfunction.

The aims of this study were to assess the effect of clenching with or without the presence of an interocclusal appliance (IOA) on bite force (BF) and masseter electromyography (EMG) in patients with temporomandibular pain dysfunction disorders (TMPD) and to compare these results with an asymptomatic age- and gender-matched control group. Ten patients with TMPD (mean age 26.9 years) were compared with eight healthy controls (mean age 25.3 years). Bilateral masseter EMG activity was recorded at rest, while clenching on the BF meter, while clenching on an IOA and while clenching on an IOA together with the BF meter. Significant left to right EMG activity asymmetry was found in the patient group at rest and during multiple clenching tasks in the control group. The patient group had significantly greater EMG activity at rest than controls. For all other tasks, the control group EMG activity was greater than the patient group. Use of an IOA significantly decreased EMG activity in both patient and control groups. BF was significantly greater in the control group on the right side for the different clenching tasks. Insertion of the IOA significantly increased BF in the control group. The results of this study indicate differences in EMG activity and BF during different clenching tasks and between patients with TMPD and asymptomatic subjects.

Vertical jaw separation and masseter muscle electromyographic activity: a comparative study between asymptomatic controls & patients with temporomandibular pain & dysfunction.

The aims of the present study were to assess the relationship pattern between bilateral masseter muscle electromyographic (MEMG) activity recordings and vertical jaw separation (VJS). Asymptomatic subjects (n = 15) were compared with age and gender-matched patients (n = 18) with temporomandibular pain and dysfunction (TMPD); before and after undergoing interocclusal appliance (IOA) therapy for 4 months. In asymptomatic subjects a bilateral minimum MEMG activity was found in a 'resting zone' at approximately a quarter of maximum mandibular opening (mean, 15.4 mm of VJS; range, 5.5-22.5 mm including overbite). No overall relationship between MEMG and VJS was shown for patients with TMPD. After successful IOA therapy, the majority of TMPD patients (14 of 18) showed normalization of the relationship between MEMG and VJS, but electromyographic assessment was not found to be of value as a single objective assessment parameter in evaluating the resolution of TMPD or the effectiveness of IOA therapy.