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.

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.

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.

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.

[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.

[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.

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.

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.

Greater disability with increased pain involvement, pain intensity and depressive preoccupation.

Persistent pain is often accompanied by functional disability. This study investigated the effect of pain extent and the involvement of specific pain sites on pain-related disability, as determined by the Pain Disability Index (PDI). Complete data were available from 278 persistent facial pain (PFP) patients. Patients were divided into one of two groups based on drawings of their pain distribution. When the patient's pain drawing was limited to the region supplied by the trigeminal nerves (Nn. V(1) V(2), and/or V(3)), with or without the inclusion of any combination of the cervical dermatomes C2, C3 and C4, the patient was assigned to the local/regional pain group. If the pain extended beyond this area, the patient was allocated to the group exhibiting widespread pain. In addition to the PDI, patients filled out the Beck Depression Inventory (BDI) and the State-Trait Anxiety Inventory (STAI). The local/regional pain group had significantly lower scores on the PDI, the BDI and STAI state than cases with widespread pain. Patients with widespread pain who indicated pain locations in any one or more of the extremities plus the lower back scored significantly higher on the PDI and the BDI than patients with no such combined involvement. Multiple regression analysis revealed that depressive preoccupation, pain extent and pain intensity were significant predictors of pain-related disability, whereas the STAI was not. If controlled for pain extent and pain intensity, the presence of high as opposed to low depressive scores added almost 11 points to the PDI score. These results showed that pain distribution, pain intensity and depressive mood are significant predictors of pain-related disability.

Pain maps from facial pain patients indicate a broad pain geography.

Two hundred consecutive female patients, who were referred to a university-based facial pain clinic, were asked to mark all painful sites on sketches showing the contours of a human body in the frontal and rear views. The drawings were analyzed with transparent templates containing 1875 (frontal view) and 1929 (rear view) square cells of equal size. The average patient scored 71.8 cells in the frontal and 99.7 cells in the rear view (corresponding to 3.8% and 5.2% of the maximum possible scores). In individual patient drawings, however, up to 42.7% and 44.9% of all cells were marked. Only 37 cases (18.5%) exhibited pain that was limited to the trigeminal system. An analysis of the pain distribution according to the arrangements of dermatomes revealed three distinct clusters of patients: (1) pain restricted to the region innervated by the trigeminal nerves (n = 37); (2) pain in the trigeminal dermatomes and any combination involving the spinal dermatomes C2, C3, and C4, but no other dermatomes (n = 32); and (3) pain sites involving dermatomes in addition to the ones listed above (n = 131). Mean ages in the three clusters were 38.7, 35.5, and 37.5 years, respectively (p = 0.62, n.s.). Widespread pain existed for longer durations (median, 48 months) than conditions involving local and regional pain (median, 24 months) (p = 0.02, s.). Our findings showed that among a great percentage of persistent facial pain patients the pain distribution is more widespread than commonly assumed, and that the persistence of pain in the regional and widespread pain presentations is significantly greater than in cases with pain limited to the trigeminal system.

Generic pain intensity scores are affected by painful comorbidity.

AIMS: To determine the degree to which the generic pain intensity rating (i.e., overall and without reference to a particular body site) of facial pain patients being seen in a specialty setting for facial pain is influenced by painful comorbidity in body parts other than the face. METHODS: In this prospective study, 40 consecutive female temporomandibular pain patients rated their generic pain on a 100-mm visual analog scale. After marking all painful body sites on pain drawings, patients were asked to rate the pain intensity for each of the indicated pain sites; the patients did not have access to the generic pain intensity score. Pearson's correlation coefficient was used to correlate the generic pain intensity score with site-specific pain intensity ratings, their mean and maximum, and the number of pain sites. RESULTS: The medians of the generic, maximum, and facial pain intensity scores were 49.5, 53, and 45.5, respectively. The generic pain intensity rating correlated more highly with the intensity scores reported for the most painful body site (r2 = 0.82; P < 0.001) than with the average rating across all painful sites (r2 = 0.62; P < 0.001), or the pain intensity score in the face (r2 = 0.61; P < 0.001). The number of pain sites did not correlate to any statistically significant degree with the generic pain intensity rating (r2 = 0.006; P = 0.65). CONCLUSION: The results of this study suggest that the maximum visual analog scale pain intensity score, observed in any body location, is a better reflection of the generic pain intensity rating than the corresponding score of the face. To avoid over-rating or underrating of facial pain intensity, patients should be instructed to provide site-specific pain intensity scores if painful comorbidity is present.

Pain descriptors characteristic of persistent facial pain.

The McGill Pain Questionnaire is an instrument that is widely used to assess the multidimensional experience of pain. Although it was introduced more than 20 years ago, limited information is available about its use in patients suffering from persistent facial pain. The aim of this study was to investigate the response patterns of persistent facial pain patients to the McGill Pain Questionnaire, to correlate these patterns with patients' beliefs about the seriousness of the condition, and to compare the findings with data reported from other painful conditions. The study sample consisted of 200 consecutive female patients referred to a tertiary care facial pain clinic. The Pain Rating Index scores of the McGill Pain Questionnaire subscales and the total number of words chosen by these patients closely matched the summary scores reported by Wilkie et al, who pooled data from seven pain conditions (cancer, chronic back, mixed chronic, acute/postoperative, labor/gynecological, dental, and experimentally induced) in their meta-analysis. On the other hand, when the data collected in this study were compared with those from specific clinical subsets, such as cancer patients, chronic back pain patients, or dental patients, differences in McGill Pain Questionnaire scores could be identified. Differences were also found in the choice of specific pain descriptors. More than 20% of the facial pain patients selected "radiating" and "pressing"; this was not the case for those suffering from other pain conditions. Facial pain patients who felt that their condition was more serious or different from what the treatment providers had told them had a greater likelihood of choosing specific word categories of the McGill Pain Questionnaire.

Treatment-seeking patterns of facial pain patients: many possibilities, limited satisfaction.

Knowledge about the different kinds of treatment provided to patients with nonmalignant musculoskeletal facial pain is limited. The present study was based on 206 consecutive patients who were referred to a university-based tertiary care clinic for the diagnosis and management of persistent facial pain. Its purpose was to get information about the number and specialty of providers consulted by patients prior to their referral, and to follow the underlying treatment-seeking patterns. The results showed that on average 4.88 providers from 44 different categories were consulted. A general dentist or a dental specialist was seen by about 70% of patients. For patients whose first provider was a dentist, the most likely subsequent provider was another dentist. Conversely, if the first provider was a physician, chances were greater that the subsequent provider was a physician rather than a dentist. Among the nondental therapies patients received, physical therapy was chosen most frequently (42.2%). More than 60% of patients had at least one nondental treatment; however, the majority of these patients experienced two or more different types of such therapy (e.g., chiropractic, osteopathic, relaxation training). Patients' satisfaction with care and treatment was moderate, since only 18.5% of the patients were very satisfied, while 27.7% were dissatisfied or very dissatisfied. The present findings, which corroborate a recent study from the Kansas City, Missouri, region, indicate that patients with persistent facial pain see a large number of different providers, and that nonmedical/nondental treatment approaches are common. The moderate satisfaction experienced with any of the therapies points out that much needs to be done before this patient population is served satisfactorily.

Computerized axiographic evaluation of condylar movements in cases with fractures of the condylar process: a follow up over 19 years.

The treatment of fractures of the mandibular condylar process(es) can be conservative or surgical. However, in many cases, a definitive judgment on the functional long-term outcome of the chosen therapy can only be given many years after the intervention. As a result, it is clearly useful to be able to review the effects of treatment undertaken at least 15 years previously. Even so, only two such studies have been identified. Therefore, the aim of the present study is to evaluate the current functional capacity of the mandibular condyles of 20 subjects who had had an uni- or bilateral fracture of the condylar process, on average 19 years ago. The individuals, who all had been treated conservatively, were compared with a control group of healthy volunteers matched for gender and age. Besides measuring maximum mouth opening (MMO), computerized axiographies in the sagittal plane were made for each condyle during MMO, maximum protrusion and maximum mediotrusion. In spite of the high degree of inter-individual variability in both groups, the data showed that the amount of condylar movement was in most cases greater in the control group. In general, it appears that the risk of developing functional problems after conservative treatment is highest in the case of a fracture of the condylar process accompanied by condylar luxation, rather than by a condylar dislocation or without it.

Palpation of the lateral pterygoid region in TMD--where is the evidence?

OBJECTIVE: Palpation of the lower head of the lateral pterygoid muscle is included in many study protocols and examination schemes of the masticatory system. The aim of this investigation was to search the medical/dental literature to find evidence for the validity and reliability of this diagnostic procedure. METHODS: A systematic search was carried out using different electronic databases (Medline Ovid, PubMed, Cochrane Library, Embase, Current Contents Connect, Science Citation Index, Web of Science, Japana Centra Revuo Medicina), supplemented by handsearch in selected journals and by examination of the bibliographies of the identified articles. VALIDITY: As far as the palpability of the inferior head of the lateral pterygoid muscle is concerned, five publications representing four studies could be identified. According to these investigations, the lateral pterygoid muscle is practically inaccessible for intraoral palpation due to topographical and anatomical reasons. Other anatomical structures, such as the superficial head of the medial pterygoid muscle, may be palpated instead in this region. Reliability: Determination of the palpability of the lateral pterygoid muscle is characterized by poor interexaminer agreement. Studies investigating the presence of pain in response to palpation of the lateral pterygoid area revealed a moderate intra- and interindividual reliability. Because of the tenderness of the lateral pterygoid region even among healthy subjects, positive findings may lead to wrong conclusions with regard to the need of treatment. CONCLUSIONS: Considering the lack of validity and reliability associated with the palpation of the lateral pterygoid area, this diagnostic procedure should be discarded.

Trigeminal neuralgia versus atypical facial pain. A review of the literature and case report.

Trigeminal neuralgia and atypical facial pain are common conditions of facial pain. Although these two pain conditions are classically well separated in textbooks, a straightforward diagnosis may not always be possible because of the overlapping clinical signs and symptoms. In this article, a comparison and differentiation between the clinical and diagnostic features of these two pain conditions are presented. The general characteristics, etiologic characteristics, pathophysiology, differential diagnostic criteria, and therapeutic options of trigeminal neuralgia and atypical facial pain are described. A case report demonstrates the difficulties that can arise in the diagnosis and differentiation between the two disease entities. The article underscores the responsibility clinicians have in correctly diagnosing and managing patients with facial pain conditions.