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.

Efficacy of stabilization splints for the management of patients with masticatory muscle pain: a qualitative systematic review

This study aimed at providing an answer to two clinical questions related to patients with masticatory muscle pain: 1) Does the use of a full-coverage hard acrylic occlusal appliance (stabilization splint) lead to a significant decrease of symptoms? and 2) Is the treatment success achieved with a stabilization splint more pronounced than the success attained with other forms of treatment (including placebo treatment) or no treatment? A systematic search was carried out in different electronic databases, supplemented by handsearch in four selected dental journals and by examination of the bibliographies of the retrieved articles. Thirteen publications, representing nine controlled clinical studies, could be identified. Reporting quality of most studies as assessed with the Jadad score ranged from 1 to 5. Based on the currently best available evidence it appears that most patients with masticatory muscle pain are helped by the incorporation of a stabilization splint. Nevertheless, evidence is equivocal if improvement of pain symptoms after incorporation of the intraoral appliance is caused by a specific effect of the appliance. A stabilization splint does not appear to yield a better clinical outcome than a soft splint, a non-occluding palatal splint, physical therapy, or body acupuncture. The scarcity of current external evidence emphasizes the need for more and better clinical research.

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.

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.

The cracked tooth syndrome: an elusive diagnosis

The authors review the literature and present a case of cracked tooth syndrome. Special emphasis is placed on diagnostic problems associated with this syndrome. The case report demonstrates classic and atypical features of cracked tooth syndrome.

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.

RESULTS

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.

Prevalence of temporomandibular disorders in patients seeking orthodontic treatment: A systematic review

The objective of this systematic review was (a) to establish the prevalence of temporomandibular disorders (TMDs) in patients seeking orthodontic treatment and (b) to determine the association between the presence of TMD and sex, age and malocclusion. A systematic literature search was performed according to PRISMA guidelines from 1969 to 2019 using the PubMed and LIVIVO databases. Eight study articles met the inclusion and exclusion criteria. An additional three contributions were identified through manual searching of the reference lists of retrieved articles. The methodological quality of the 11 articles was assessed with the Joanna Briggs Institute Critical Appraisal Checklist for prevalence studies. TMD prevalence ranged from 21.1% to 73.3%. The frequency of painful TMD signs/symptoms varied from 3.4% to 65.7%, while non-painful signs/symptoms ranged from 3.1% to 40.8%. The percentage of males and females presenting with TMD varied from 10.6% to 68.1% and 21.2 to 72.4%, respectively. In all studies, TMD prevalence was higher among females. The majority of articles reported more TMD signs/symptoms in individuals older than 18 years as compared to younger ones (≤18 years). While in four studies no association between TMD and malocclusion was found, another three investigations indicated that TMD may be related to certain occlusal traits. The TMD prevalence in patients seeking orthodontic treatment was high, with many individuals presenting painful TMD signs/symptoms. Female and older patients appear to have a greater occurrence of TMD. Although no strong association between TMD and malocclusion was established, several occlusal traits were implicated.

Determining mandibular condyle and ramus height with the help of an Orthopantomogram--a valid method?

The asymmetry of condylar and rami heights was determined from orthopantomograms of 25 macerated skulls and compared with the results of the 'true' values obtained by direct measurements of the skulls. The correlation between the two measuring methods was low.

Temporomandibular disorders--pain outside the head and face is rarely acknowledged in the chief complaint

STATEMENT OF PROBLEM

With diagnostic and therapeutic procedures being heavily influenced by the patient's chief complaint, the question arises whether this information alone represents a solid basis for clinical action.

PURPOSE

The aim of this investigation was to assess the agreement between pain complaints and patient generated paper-and-pencil drawings of the distribution of pain in patients suffering from temporomandibular disorders.

METHODS

The study included 140 adult female patients with temporomandibular disorders. Pain drawings served as a standard, against which the oral reports were compared. In 40 (29%) of the patients, pain was limited to the head and face; in the remaining subjects, it exceeded the boundaries of these regions. Nine potential pain sites were distinguished (head, face, neck, shoulders, arms, chest, abdomen, back, and legs). Whenever one of these regions was part of the drawing or the pain complaint, it was counted. Sensitivity, specificity, and kappa indices were computed for each site.

RESULTS

Patients with pain limited to the head and face showed a close correspondence between pain report and drawing. On the other hand, patients with temporomandibular disorders with concomitant pain sites outside the head and face frequently did not mention these additional pain locations. This was reflected in low sensitivities (minimum: 0.00; maximum: 0.48) and low kappa values (minimum: -0.02; maximum: 0.19).

CONCLUSIONS

This study showed that the chief complaint frequently underestimates the real extent of pain involvement.

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.

Differential activity patterns in the masseter muscle under simulated clenching and grinding forces

The aim of this study was to investigate (i) whether the masseter muscle shows differential activation under experimental conditions which simulate force generation during clenching and grinding activities; and (ii) whether there are (a) preferentially active muscle regions or (b) force directions which show enhanced muscle activation. To answer these questions, the electromyographic (EMG) activity of the right masseter muscle was recorded with five intramuscular electrodes placed in two deep muscle areas and in three surface regions. Intraoral force transfer and force measurement were achieved by a central bearing pin device equipped with three strain gauges (SG). The activity distribution in the muscle was recorded in four different mandibular positions (central, left, right, anterior). In each position, maximum voluntary contraction (MVC) was exerted in vertical, posterior, anterior, medial and lateral directions. The investigated muscle regions showed different amount of EMG activity. The relative intensity of the activation, with respect to other regions, changed depending on the task. In other words, the muscle regions demonstrated heterogeneous changes of the EMG pattern for the various motor tasks. The resultant force vectors demonstrated similar amounts in all horizontal bite directions. Protrusive force directions revealed the highest relative activation of the masseter muscle. The posterior deep muscle region seemed to be the most active compartment during the different motor tasks. The results indicate a heterogeneous activation of the masseter muscle under test conditions simulating force generation during clenching and grinding. Protrusively directed bite forces were accompanied by the highest activation in the muscle, with the posterior deep region as the most active area.

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.

[Functional somatic pain syndromes: summary of hypotheses of their overlap and etiology]

Currently it is unclear whether functional somatic syndromes can be explained by one common underlying functional syndrome. In any case it does not seem justified to view functional somatic syndromes as purely psychological disorders (somatized anxiety or depression). Psychiatric comorbidity and life time stress including traumatisations are mainly, but not exclusively responsible for triggering health care utilisation. The lowered pain threshold that can be demonstrated clinically and experimentally in fibromyalgia, irritable bowel syndrome, tension headache and temporomandibular disorders is currently seen primarily as result of an altered central nervous processing of nociceptive input. In addition some results also hint at a disturbance in the hypothalamus-pituitary-adrenal axis. The predominance of female patients can be due to gender specific illness behaviour as well as to estrogen-induced changes in pain sensitivity. In sum, functional somatic syndromes currently are best explained by a biopsychosocial model of predisposing, triggering and maintaining factors. More research is needed particularly to clarify the role of genetic and of cultural factors.

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.

The effect of musculoskeletal facial pain on registration of maxillomandibular relationships and treatment planning: a synthesis of the literature

STATEMENT OF PROBLEM

A significant number of patients exist who are in need of prosthodontic rehabilitation and who at the same time report musculoskeletal pain in the facial area.

PURPOSE

This article, which is based on an assessment of both the past and the most recent basic science and clinical literature, evaluates the effect of musculoskeletal facial pain on two static (physiologic rest position and centric relation) and two dynamic (protrusive border and lateral border movements) maxillomandibular relationships.

MATERIAL AND METHODS

To find the relevant studies addressing the association between musculoskeletal facial pain and maxillomandibular relationships, a MEDLINE search was conducted, which was complemented by a hand search in selected journals.

RESULTS AND CONCLUSIONS

Musculoskeletal facial pain seems to variably affect the aforementioned positions and movements. Hence, the validity of maxillomandibular registrations in patients with existing facial pain is questioned. In those patients with facial pain who simultaneously are in need of a prosthodontic rehabilitation, clinicians should be cautious with regard to the timing of the restorative procedures.

Prosthetic rehabilitation in patients with temporomandibular disorders

Decision-making in prosthetic dentistry and in the management of patients suffering from temporomandibular disorders is strongly influenced by the clinical and educational background of the dentist. The prosthetic rehabilitation of patients affected by one of the various subsets of temporomandibular disorders is a particularly challenging task, and the literature about this topic is limited. This article reviews the current situation and gives suggestions on how the dentist should proceed in the prosthetic treatment of these patients.

Reliability and Validity of the Diagnostic Criteria for Temporomandibular Disorders Axis I in Clinical and Research Settings: A Critical Appraisal

The recently published Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I, which is recommended for use in clinical and research settings, has provided an update of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The authors of the DC/TMD based their publication on the results of a Validation Project (2001-2008) and consecutive workgroup sessions held between 2008 and 2013. The DC/TMD represents a major change in both content and procedures; nonetheless, earlier concerns and new insights have only partly been followed up when drafting the new recommendations. Moreover, the emphasis on immediate implementation in clinical and research settings is not in line with the provided external evidence on which the DC/TMD is based. This Focus Article describes these concerns with regard to several aspects of the DC/TMD: the additional classification categories; the high dependency on pressure-pain results from use of the recommended palpation technique; the TMD pain screening instrument; the test population characteristics; the utility of additional subgroups; the use of a reference standard; the dichotomy between pain and dysfunction; and the DC/TMD algorithms. Thus, although the DC/TMD represents an improvement over the RDC/TMD, its immediate implementation in research and clinical care does not yet appear to be adequately substantiated.

Associations between the masticatory system and muscle activity of other body districts. A meta-analysis of surface electromyography studies

The aim of this meta-analysis regarding the use of surface electromyography (sEMG) is to assess the scientific evidence for detectable correlations between the masticatory system and muscle activity of the other body districts, particularly those mainly responsible for body posture. A literature survey was performed using the PubMed database, covering the period from January 1966 to April 2011, and choosing medical subject headings. After selection, five articles qualified for the final analysis. One study article was judged to be of medium quality, the remaining four of low quality. No study included a control group or follow-up; in only one study, subjects with impairment of the masticatory system were enrolled. In all studies, detectable correlations between the masticatory systems and muscle activity of the other body districts, or vice versa, were found; however, after a reappraisal of the data provided in these studies, only weak correlations were found, which reached biological, but not clinical relevance. With the limitations that arise from the poor methodological quality of the published study reports discussed here, the conclusion is that a correlation between the masticatory system and muscle activity of the other body districts might be detected through sEMG under experimental conditions; however, this correlation has little clinical relevance. While more investigations with improved levels of scientific evidence are needed, the current evidence does not support clinically relevant correlations between the masticatory system and the muscle activity of other body districts, including those responsible for body posture.

Occlusal dysesthesia-A clinical guideline

Background

The diagnosis and management of patients suffering from occlusal dysesthesia (OD) remain a major challenge for dental practitioners and affected patients.

Objectives

To present the results of a literature‐based expert consensus intended to promote better understanding of OD and to facilitate the identification and management of affected patients.

Methods

In 2018, electronic literature searches were carried out in PubMed, Cochrane Library and Google Scholar as well as in the archives of relevant journals not listed in these databases. This approach was complemented by a careful assessment of the reference lists of the identified relevant papers. The articles were weighted by evidence level, followed by an evaluation of their contents and a discussion. The result represents an expert consensus.

Results

Based on the contents of the 77 articles identified in the search, the current knowledge about clinical characteristics, epidemiology, aetiology, diagnostic process, differential diagnosis and management of OD is summarised.

Conclusions

Occlusal dysesthesia exists independently of the occlusion. Instead, it is the result of maladaptive signal processing. The focus should be on patient education, counselling, defocusing, cognitive behavioural therapy, supportive drug therapy and certain non‐specific measures. Irreversible, specifically an exclusively dental treatment approach must be avoided.

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.

Centric relation critically revisited-What are the clinical implications?

PURPOSE OF THE ARTICLE

Centric relation is a dental term that has undergone many alterations over the years, which in turn have led to significant clinical controversies. These continuing changes in the meaning of the term CR have not only led to confusion, but they also have resulted in a variety of unnecessary diagnostic and therapeutic procedures. Analysis of the dental literature reveals ongoing misunderstanding and disagreement regarding that term among both clinicians and academic dentists.

MATERIALS AND METHODS

A search of the PubMed database was performed with the following search terms: "centric relation", "masticatory muscles", "maxillomandibular relationship" and "condylar position." Relevant literature from the past 70 years until the present day was meticulously scrutinised.

RESULTS

As expected, the literature review on the topic of CR revealed a problematic pattern of changing definitions and clinical disagreements, all of which have had a significant impact on the practice of dentistry.

CONCLUSION

There are semantic, conceptual and practical reasons for concluding that the term 'centric relation' is flawed. Those flaws have a significant impact on dental practice. Based on our analysis, argumentation is provided to conclude that the term 'centric relation' should be abandoned. Instead, it appears that every individual has a unique temporomandibular joint relationship which cannot be described by any singular term. In healthy dentate patients, this relationship is determined by the maximum intercuspation of the teeth and should therefore be considered as biologically acceptable.

[Atypical odontalgia - a little known phantom pain]

BACKGROUND

Atypical odontalgia (AO) was described in the dental literature more than 200 years ago, and it is included in most taxonomies and textbooks of pain. Nonetheless, it remains one of the most frequently misdiagnosed intraoral pain conditions.

TERMINOLOGY

Due to similarities with phantom pain, AO is also referred to as "phantom tooth pain".

CLINICAL FEATURES

AO is characterized by persistent throbbing pain in or around a former or present permanent tooth (preferably molars and premolars). Clinical and radiographic examination, however, does not reveal any organic cause of the pain. The complaints associated with AO usually begin after deafferentiation of primary afferent trigeminal nerve fibers, e. g., after pulp extirpation, apicectomy, or extraction of a tooth.

DIAGNOSIS

AO is a diagnosis by exclusion.

MANAGEMENT

Patients and dentists must be aware of the fact that the therapeutic options are limited. AO is primarily managed with topically or systemically administered pharmacological agents. Unnecessary and harmful procedures around teeth and jaws must be avoided by all means.

OUTLOOK

A concept was recently proposed which aims to unify a group of four types of orofacial pain under the term "idiopathic orofacial pain" (Woda & Pionchon 1999, 2000). These pain conditions - AO, atypical facial pain, burning mouth syndrome ("stomatodynia"), and subgroups of temporomandibular disorders ("idiopathic facial arthromyalgia") - are characterized by unknown etiology, but common clinical characteristics. It is to be hoped that the suggested classification will stimulate reflection on these enigmatic orofacial pain disorders.

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.

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.