Small vertical changes in jaw relation affect motor unit recruitment in the masseter.

Strategies for recruitment of masseter muscle motor units (MUs), provoked by constant bite force, for different vertical jaw relations have not previously been investigated. The objective of this study was to analyse the effect of small changes in vertical jaw relation on MU recruitment behaviour in different regions of the masseter during feedback-controlled submaximum biting tasks. Twenty healthy subjects (mean age: 24·6 ± 2·4 years) were involved in the investigation. Intra-muscular electromyographic (EMG) activity of the right masseter was recorded in different regions of the muscle. MUs were identified by the use of decomposition software, and root-mean-square (RMS) values were calculated for each experimental condition. Six hundred and eleven decomposed MUs with significantly (P < 0·001) different jaw relation-specific recruitment behaviour were organised into localised MU task groups. MUs with different task specificity in seven examined tasks were observed. The RMS EMG values obtained from the different recording sites were also significantly (P < 0·01) different between tasks. Overall MU recruitment was significantly (P < 0·05) greater in the deep masseter than in the superficial muscle. The number of recruited MUs and the RMS EMG values decreased significantly (P < 0·01) with increasing jaw separation. This investigation revealed differential MU recruitment behaviour in discrete subvolumes of the masseter in response to small changes in vertical jaw relations. These fine-motor skills might be responsible for its excellent functional adaptability and might also explain the successful management of temporomandibular disorder patients by somatic intervention, in particular by the use of oral splints.

[Clinical management of masticatory muscle pain: an update of the recommendations]. / Therapie bei Schmerzen der Kaumuskulatur: Aktualisierung der Empfehlungen.

Besides the different forms of odontalgia, myalgias of the masticatory muscles are the most frequent noninfectious complaints in the orofacial region. After summarizing the recommendations set forth by the Interdisciplinary Working Group of Orofacial Pain within the German Chapter of the IASP (German Pain Society), we present the current state of knowledge regarding the etiology, diagnosis, and therapeutic options, based on an extensive literature search. A systematic literature search was carried out in PubMed, the Cochrane Library, and the database of the Deutsche Zahnärztliche Zeitschrift. The results corroborate our previous recommendations that for the majority of patients pain reduction or pain relief can be achieved with noninvasive, reversible methods. Short- and long-term trials have added more evidence to the fact that different therapeutic measures have similar efficacy. In patients with chronic myalgias of the jaw muscles, involvement of a psychotherapist is crucial. Patient education, oral appliances, physiotherapeutic exercises, and acupuncture are recommended therapeutic measures, while physical therapy, pharmacotherapy, and psychological therapy received a limited recommendation.

The dental occlusion as a suspected cause for TMDs: epidemiological and etiological considerations.

The relationship between the dental occlusion and temporomandibular disorders (TMDs) has been one of the most controversial topics in the dental community. In a large epidemiological cross-sectional survey - the Study of Health in Pomerania (Germany) - associations between 15 occlusion-related variables and TMD signs or symptoms were found. In other investigations, additional occlusal variables were identified. However, statistical associations do not prove causality. By using Hill's nine criteria of causation, it becomes apparent that the evidence of a causal relationship is weak. Only bruxism, loss of posterior support and unilateral posterior crossbite show some consistency across studies. On the other hand, several reported occlusal features appear to be the consequence of TMDs, not their cause. Above all, however, biological plausibility for an occlusal aetiology is often difficult to establish, because TMDs are much more common among women than men. Symptom improvement after insertion of an oral splint or after occlusal adjustment does not prove an occlusal aetiology either, because the amelioration may be due to the change of the appliance-induced intermaxillary relationship. In addition, symptoms often abate even in the absence of therapy. Although patients with a TMD history might have a specific risk for developing TMD signs, it appears more rewarding to focus on non-occlusal features that are known to have a potential for the predisposition, initiation or perpetuation of TMDs.

Influence of neck rotation and neck lateroflexion on mandibular equilibrium.

Neuromuscular interaction between neck and jaw muscles has been reported in several studies. However, the influence of experimentally modified posture of the neck on jaw muscle activity during isometric biting was not investigated so far. The aim of the present study was to test by the aid of simultaneous electromyographic and intraoral bite force measurements whether neck rotation and lateroflexion, in contrast to a straightforward neck position, change the isometric cocontraction patterns of masticatory muscles under identical submaximum bite forces of 50-200 N. Electric muscle activity of all masticatory muscles and changes of the reduction point (RP) of the resultant bite force vectors were examined. An anteroposterior displacement of the RPs could be observed for the rotated and lateroflexed neck position in comparison with the straightforward position. On the other hand, the results revealed no significant differences between bilateral muscle activation under the different test conditions. These findings suggest a force transmission between the neck and the masticatory system, but no essential activity changes in the masticatory muscles under short time posture modification of the neck.

Temporomandibular pain and depression in adolescents--a case-control study.

This study compared the depression status of adolescents with temporomandibular (TM) pain to those without, considering the influence of age, sex, and other pain conditions. From a general population sample of 455 adolescents, 29 cases (mean age, 15.3 years) with current TM pain were compared with 44 age-matched controls without such pain. Study participants were examined for general health status, additional pain sites (back, abdomen, and head) in the previous month, and depression, using a 15-item German-language depression questionnaire. Cases had a statistically significant higher average depression score than controls (14.2 +/- 7.1 vs. 9.7 +/- 6.3; t test, p < 0.01), and they reported more often additional pain. The more pain sites were mentioned, the higher was the depression score [no pain, 4.0 +/- 2.8; four pains, 17.3 +/- 8.0; analysis of variance (ANOVA), p < 0.001]. We conclude that TM pain assessment among adolescents should include a whole-body pain drawing as well as a screening questionnaire to identify pain-related depressive symptoms.

Small unilateral jaw gap variations: equilibrium changes, co-contractions and joint forces.

After complex prosthetic reconstructions, small differences in vertical distances between the left and right side of the jaw may occur during jaw closing, nevertheless providing bilateral tooth contacts in intercuspation by small deformations of the mandible. Their effects on the co-contraction of the masticatory muscles, the temporomandibular joint reaction forces, and the point of application of the resultant bite force vector in the maxillary occlusion plane - the so-called reduction point - have not been investigated, thus far simultaneously in one sample. The main goal of this study was to investigate variations of these measures in an experimental intercuspation simulated by one anterior and two posterior force transmission points.

[Suggestion for a classification of odontalgias]. / Vorschlag einer Klassifikation der Odontalgien.

BACKGROUND: Toothache prevalence in the overall population is considerable. However, for clinical purposes, the classification schemes available do not appear to be sufficiently sophisticated. Moreover, not all known forms of dental pain are considered. A refined classification that meets current standards is therefore introduced. To facilitate diagnosis, the characteristic features of the various types of odontalgia are summarized. RESULTS: The new classification differentiates among seven different origins of pain: 1. dentinal pain (originating from the pulpal tissues), 2. pulpal pain (originating from the pulpal tissues), 3. periodontal pain, 4. alveolar-osseous pain, 5. atypical odontalgia, 6. heterotopic dental pain, 7. odontalgia associated with primary psychosocial factors. CONCLUSIONS: In our opinion, the proposed classification differentiates among the different forms of odontalgia more precisely than all previous ones. However, its viability and advantages over other available classification schemes still need to be verified in daily practice.

[Myalgia of the masticatory muscles]. / Myalgie der Kiefermuskulatur.

Masticatory muscle pain can be regarded as a regional manifestation of musculoskeletal disorders similar to those observed in other body regions. Along with temporomandibular joint pain and some painless disturbances related to mandibular mobility they are subsumed under the term temporomandibular disorders (TMD). Masticatory muscle pain is assumed to be associated with a variety of biophysiological risk factors. Valid diagnostic instruments make it possible to differentiate between the various TMD subgroups. In most cases, masticatory muscle pain can be treated/managed successfully. In a considerable number of patients, however, the pain persists over a long period of time despite therapeutic interventions. Understanding of the underlying neurobiological background of acute and chronic pain may help in therapeutic decision-making and evaluation of the therapeutic effects.

Dental occlusion: a critical reflection on past, present and future concepts.

For nearly a century, the diversity of concepts about 'normal' and 'ideal' dental occlusal relationships has led to confusion in trying to describe the occlusion of any individual patient. In addition, a similar controversy arises when trying to formulate treatment plans for patients who need extensive dental restorations or orthodontic treatment. And finally, the application of occlusal concepts to patients with temporomandibular pain and dysfunction has created a third area of debate. Over the past few decades, however, an appreciable part of the tenacious dogmatic heritage of this topic has been challenged. As a result, the acceptance of morphological and functional variability of the stomatognathic system has gained increasing support, and this change has important consequences for modern dental practice. In this article, the past, present and future of the subject of occlusion will be considered.

Jaw clenching: muscle and joint forces, optimization strategies.

Realistic masticatory muscle and temporomandibular joint forces generated during bilateral jaw clenching are largely unknown. To determine which clenching directions load masticatory muscles and temporomandibular joints most heavily, we investigated muscle and joint forces based on feedback-controlled electromyograms of all jaw muscles, lines of action, geometrical data from the skull, and physiological cross-sectional areas acquired from the same individuals. To identify possible motor control strategies, we applied objective functions. The medial pterygoid turned out to be the most heavily loaded muscle for all bite directions. Biting with accentuated horizontal force components provoked the highest loading within the medial and lateral pterygoids. The largest joint forces were also found for these bite directions. Conversely, the lowest joint forces were detected during vertical biting. Additionally, joint forces with a clear posterior orientation were found. Optimization strategies with the elastic energy as objective function revealed the best fit with the calculated results.

[Therapy of temporomandibular joint pain: recommendations for clinical management]. / Therapie bei Arthralgie der Kiefergelenke: Empfehlungen zum klinischen Management.

Arthralgias of the temporomandibular joint occur rarely in their isolated form, in contrast to myalgias of the jaw muscles. Most often, arthralgias are combined with myofascial pain. Here we define relevant terms (arthralgia, arthropathy, arthritis, osteoarthritis/osteoarthrosis), describe special diagnostic aspects and provide diagnosis-related specifications. We then present current information on the clinical management of temporomandibular joint pain. A systematic literature search revealed that pain reduction or pain relief can be achieved with non-invasive reversible methods for the majority of patients. Results from short and long-term longitudinal studies show that different therapeutic methods are similarly effective. For the management of chronic forms with extensive psychosocial impairment a multidisciplinary approach is essential.

[Therapy of masticatory muscle pain: recommendations for clinical management]. / Therapie bei Schmerzen der Kaumuskulatur: Empfehlungen zum klinischen Management.

Myalgias of the masticatory muscles are the most frequent noninfectious complaints in the orofacial region. After summarizing the current knowledge on the physiology, etiology, pathophysiology, diagnosis, and differential diagnosis of masticatory muscle pain, we specifically focus on management recommendations. Results of an extensive literature search show that for the majority of patients pain reduction or pain relief can be achieved with noninvasive reversible methods. Longitudinal short- and long-term studies have revealed that different therapeutic measures are similarly effective. In patients with chronic masticatory myalgias associated with psychosocial impairment, however, additional involvement of a psychotherapist is crucial.

[Pain drawings of patients with orofacial pain. Comparison of acceptance and gain of information]. / Schemata zur Schmerzeinzeichnung bei Patienten mit orofazialen Schmerzen. Vergleich von Akzeptanz und Informationsgehalt.

AIM OF THE STUDY: The aim of this prospective multicentric study was to compare two different types of pain drawings in terms of acceptance and gain of information in patients with orofacial pain. PATIENTS AND METHODS: A total of 204 patients from 9 centers, who visited their dentist or physician for orofacial pain, received two different diagrams for pain drawings in random order. One was the original pain diagram of the Deutsche Schmerzfragebogen (German Pain Questionnaire, diagram A), and the other diagram had been developed to achieve a symmetrical representation of the body and to allow computer-assisted analysis (diagram B). This diagram was larger and contained a drawing of the head. The patients' answers were analyzed for the preference between diagrams, the number and distribution of pain areas, and the concordance between the diagrams. The results were correlated with the patients' data. RESULTS: Data from 183 patients could be analyzed: 100 of 183 patients preferred diagram B and 57 of 183 preferred diagram A, independent of gender, age, or duration of disease. Most patients reported pain in more than one area; in only 43 of 183 patients was the pain limited to the face and head. The number and distribution of pain areas were not different between the two pain diagrams. CONCLUSIONS: Detailed head and body diagrams can be used in the diagnostic evaluation of patients with orofacial pain without fear of placing excessive demands on the patients and are useful for detecting comorbidities.

Asymmetry of the articular eminence in dentate and partially edentulous populations.

The purpose of this study was to assess the degree of right-left asymmetry of the glenoid fossa. The specific aims were (1) to determine whether there were relationships between age, number of teeth, slope of the articular eminence, fossa depth, and the degree of right-left asymmetry, and (2) to compare the right-left asymmetry of two populations, one characterized by an acceptable occlusion (A-Occ), the other by an unacceptable occlusion (partially edentulous; Un-Occ). A-Occ was defined as possessing a minimum of 28 teeth that would allow for hand articulation of the mandibular teeth to the maxillary teeth. Un-Occ had fewer than 17 teeth, which would make it impossible to articulate the mandible with the maxilla. The sample included 20th century dry skulls: 70 African-American (44 male, 26 female) and 64 European-American (49 male, 15 female), ranging in age from 21-105 (mean 47.1 +/- 19.9). The medial (M), central (C), and lateral (Lat) aspects of the right (R) and left (L) slopes of the articular eminence were measured in a sagittal plane. The R and L fossa depth also were measured. The raw absolute differences IR-LI and relative differences [IR-LI/IR+Llx100] of the articular slope angles (M, C, and Lat) and fossa depths were computed. Statistical analysis included paired t-tests, independent t-tests, and Pearson's correlation coefficients, significance at p < or = 0.05. Ninety percent (90%) of the population exhibited right-left asymmetry of the glenoid fossa. The right articular slopes (M, C, and Lat) were significantly steeper than the left articular slopes; the right fossa depths were significantly deeper than the left. There generally were no differences in the articular slope steepness or fossa depths between the partially dentate and the dentate, nor were there statistical differences between the two groups in the raw absolute differences or relative differences of the M, C, and Lat slopes or fossa depths. No significant relationships were found between right-left asymmetry, age, or number of teeth. With only 10% of the subjects exhibiting symmetry of the glenoid fossa depths or articular slope angles, clinicians should consider bilateral asymmetry the norm and not an anomaly.

[Recommendations for the standardized evaluation and classification of painful temporomandibular disorders: an update]. / Aktualisierung der Empfehlungen zur standardisierten Diagnostik und Klassifikation von Kaumuskel- und Kiefergelenkschmerzen.

BACKGROUND: In 2000, the interdisciplinary Working Group of Orofacial Pain within the German Chapter of the IASP (German Association for the Study of Pain) published recommendations for the standardized evaluation and diagnostic classification of patients with painful masticatory muscles and/or temporomandibular joints. The purpose of the present study was to critically review and update these recommendations. RESULTS: Appraisal of the relevant literature published after the release of the recommendations (up to December 2005) shows that the two-axis approach for the assessment of the somatic and psychosocial parameters of the orofacial pain experience has found wide support. Single aspects of the recommendations have been substantiated by additional scientific evidence. CONCLUSIONS: The recommendations reflect the current state of pain medicine. Therefore, they should be considered among practitioners who diagnose and manage patients suffering from temporomandibular disorders.

Evidence-based dentistry in German-language dental journals 1997-2003.

The purpose of this systematic literature search was to evaluate how the evidence-based approach appears in German-language dental journals. All volumes of 28 dental journals published between 1997 and 2003 were searched by hand; for 15 of these journals, an additional electronic search was made. The focus of the search was all articles, editorials or letters to the Editor dealing with topics related to evidence-based dentistry (EBD)/medicine or using its terminology. Of the 1776 journal issues that were scrutinised, 368 relevant publications were found. After a low, albeit slightly increasing, number of pertinent contributions published between 1997 and 1999, there was a sharp rise in 2000 and 2001, culminating in 2003. Our findings indicate a rising awareness of the concept of EBD in the German-language dental literature. Nonetheless, its reception within the German-speaking dental community is still modest.