Development and preliminary evaluation of a new screening instrument for atypical odontalgia and persistent dentoalveolar pain disorder.

AIM: To develop and preliminarily evaluate a new screening instrument for atypical odontalgia (AO) or persistent dentoalveolar pain disorder (PDAP). To evaluate the instrument's performance in detecting AO/PDAP amongst a heterogeneous group of orofacial pain conditions and pain-free controls and empirically compare its performance with an established neuropathic screening instrument (S-LANSS), which is the best available standard. METHODS: The study design was cross-sectional; subjects recruited included a convenience sample of pain-free controls (n = 21) and four groups of orofacial pain conditions: AO/PDAP (n = 22); trigeminal neuralgia (n = 21); temporomandibular disorder (n = 41); and acute dental pain (n = 41). The instrument's internal reliability and factor structure were examined alongside its sensitivity and specificity and ROC-determined threshold score. RESULTS: The 9 AO/PDAP-specific items were found to moderately correlate with the S-LANSS (r = 0.58; P < 0.01). The 14-items of the full instrument were examined using exploratory factor analysis and reduced to ten items in a two-factor structure that explained 96% of the variance. This 10-item final instrument had a ROC area of 0.77 (95% CI: 0.67; 0.88), sensitivity of 77% (95% CI: 55; 92%), and specificity of 69% (95% CI: 60; 77%) with an intentionally higher false-positive rate than false-negative rate. In contrast, the S-LANSS exhibited sensitivity of 32% (95% CI: 14;55%) and specificity of 78% (95% CI: 70;85%) with less optimal false-positive versus false-negative rates. CONCLUSION: This preliminary study confirms the new screening instrument for AO/PDAP merits progression to field testing.

Influence of culture on pain comorbidity in women with and without temporomandibular disorder-pain.

Evidence on cultural differences in prevalence and impact of common chronic pain conditions, comparing individuals with temporomandibular disorders (TMD) versus individuals without TMD, is limited. The aim was to assess cross-cultural comorbid pain conditions in women with chronic TMD pain. Consecutive women patients (n = 122) with the index condition of chronic TMD pain diagnosed per the research diagnostic criteria for TMD and TMD-free controls (n = 121) matched for age were recruited in Saudi Arabia, Italy and Sweden. Self-report questionnaires assessed back, chest, stomach and head pain for prevalence, pain intensity and interference with daily activities. Logistic regression was used for binary variables, and ancova was used for parametric data analysis, adjusting for age and education. Back pain was the only comorbid condition with a different prevalence across cultures; Swedes reported a lower prevalence compared to Saudis (P < 0·01). Saudis reported higher prevalence of work reduced >50% due to back pain compared to Italians or Swedes (P < 0·01). Headache was the most common comorbid condition in all three cultures. The total number of comorbid conditions did not differ cross-culturally but were reported more by TMD-pain cases than TMD-free controls (P < 0·01). For both back and head pain, higher average pain intensities (P < 0·01) and interference with daily activities (P < 0·01) were reported by TMD-pain cases, compared to TMD-free controls. Among TMD-pain cases, Italians reported the highest pain-related disability (P < 0·01). Culture influences the associated comorbidity of common pain conditions. The cultural influence on pain expression is reflected in different patterns of physical representation.

The effect of culture on pain sensitivity.

Cross-cultural differences in pain sensitivity have been identified in pain-free subjects as well as in chronic pain patients. The aim was to assess the impact of culture on psychophysical measures using mechanical and electrical stimuli in patients with temporomandibular disorder (TMD) pain and pain-free matched controls in three cultures. This case-control study compared 122 female cases of chronic TMD pain (39 Saudis, 41 Swedes and 42 Italians) with equal numbers of age- and gender-matched TMD-free controls. Pressure pain threshold (PPT) and tolerance (PPTo) were measured over one hand and two masticatory muscles. Electrical perception threshold and electrical pain threshold (EPT) and tolerance (EPTo) were recorded between the thumb and index fingers. Italian females reported significantly lower PPT in the masseter muscle than other cultures (P < 0.001) and in the temporalis muscle than Saudis (P = 0.003). Swedes reported significantly higher PPT in the thenar muscle than other cultures (P = 0.017). Italians reported significantly lower PPTo in all muscles than Swedes (P ≤ 0.006) and in the masseter muscle than Saudis (P < 0.001). Italians reported significantly lower EPTo than other cultures (P = 0.01). Temporomandibular disorder cases, compared to TMD-free controls, reported lower PPT and PPTo in all the three muscles (P < 0.001). This study found cultural differences between groups in the PPT, PPTo and EPTo. Overall, Italian females reported the highest sensitivity to both mechanical and electrical stimulation, while Swedes reported the lowest sensitivity. Mechanical pain thresholds differed more across cultures than did electrical pain thresholds. Cultural factors may influence response to type of pain test.

Self-management programmes in temporomandibular disorders: results from an international Delphi process.

Self-management (SM) programmes are commonly used for initial treatment of patients with temporomandibular disorders (TMD). The programmes described in the literature, however, vary widely with no consistency in terminology used, components of care or their definitions. The aims of this study were therefore to construct an operationalised definition of self-management appropriate for the treatment of patients with TMD, identify the components of that self-management currently being used and create sufficiently clear and non-overlapping standardised definitions for each of those components. A four-round Delphi process with eleven international experts in the field of TMD was conducted to achieve these aims. In the first round, the participants agreed upon six principal concepts of self-management. In the remaining three rounds, consensus was achieved upon the definition and the six components of self-management. The main components identified and agreed upon by the participants to constitute the core of a SM programme for TMD were as follows: education; jaw exercises; massage; thermal therapy; dietary advice and nutrition; and parafunctional behaviour identification, monitoring and avoidance. This Delphi process has established the principal concepts of self-management, and a standardised definition has been agreed with the following components for use in clinical practice: education; self-exercise; self-massage; thermal therapy; dietary advice and nutrition; and parafunctional behaviour identification, monitoring and avoidance. The consensus-derived concepts, definitions and components of SM offer a starting point for further research to advance the evidence base for, and clinical utility of, TMD SM.

Perspectives on next steps in classification of oro-facial pain - part 2: role of psychosocial factors.

This study was initiated by a symposium, in which the present authors contributed, organised by the International RDC/TMD Consortium Network in March 2013. The purpose of the study was to review the status of biobehavioural research - both quantitative and qualitative - related to oro-facial pain (OFP) with respect to the aetiology, pathophysiology, diagnosis and management of OFP conditions, and how this information can optimally be used for developing a structured OFP classification system for research. In particular, we address representation of psychosocial entities in classification systems, use of qualitative research to identify and understand the full scope of psychosocial entities and their interaction, and the usage of classification system for guiding treatment. We then provide recommendations for addressing these problems, including how ontological principles can inform this process.

Perspectives on next steps in classification of oro-facial pain - part 1: role of ontology.

The purpose of this study was to review existing principles of oro-facial pain classifications and to specify design recommendations for a new system that would reflect recent insights in biomedical classification systems, terminologies and ontologies. The study was initiated by a symposium organised by the International RDC/TMD Consortium Network in March 2013, to which the present authors contributed. The following areas are addressed: problems with current classification approaches, status of the ontological basis of pain disorders, insufficient diagnostic aids and biomarkers for pain disorders, exploratory nature of current pain terminology and classification systems, and problems with prevailing classification methods from an ontological perspective. Four recommendations for addressing these problems are as follows: (i) develop a hypothesis-driven classification structure built on principles that ensure to our best understanding an accurate description of the relations among all entities involved in oro-facial pain disorders; (ii) take into account the physiology and phenomenology of oro-facial pain disorders to adequately represent both domains including psychosocial entities in a classification system; (iii) plan at the beginning for field-testing at strategic development stages; and (iv) consider how the classification system will be implemented. Implications in relation to the specific domains of psychosocial factors and biomarkers for inclusion into an oro-facial pain classification system are described in two separate papers.

Perspectives on next steps in classification of oro-facial pain - Part 3: biomarkers of chronic oro-facial pain - from research to clinic.

The purpose of this study was to review the current status of biomarkers used in oro-facial pain conditions. Specifically, we critically appraise their relative strengths and weaknesses for assessing mechanisms associated with the oro-facial pain conditions and interpret that information in the light of their current value for use in diagnosis. In the third section, we explore biomarkers through the perspective of ontological realism. We discuss ontological problems of biomarkers as currently widely conceptualised and implemented. This leads to recommendations for research practice aimed to a better understanding of the potential contribution that biomarkers might make to oro-facial pain diagnosis and thereby fulfil our goal for an expanded multidimensional framework for oro-facial pain conditions that would include a third axis.

Achieved competences in temporomandibular disorders/orofacial pain: a comparison between two dental schools in Europe.

AIMS: The aim was to study achieved competences in temporomandibular disorders (TMD)/orofacial pain (OP) at two universities by comparing student's knowledge and understanding, satisfaction with their education and confidence in their clinical competences of TMD/OP. METHODS: The study was conducted in collaboration between Malmö University, Sweden­which uses problem-based learning­and the University of Naples Federico II, Italy­which uses traditional educational methods. Final-semester dental students responded to a self-report questionnaire regarding their knowledge and understanding, interpretation of cases histories, clinical experience, satisfaction and confidence in clinical examination, management and treatment evaluation. RESULTS: No significant difference was found between the students regarding knowledge and understanding. Eighty-seven per cent of the Malmö students and 96% of the Naples students met the criterion on achieved competence. Malmö students had a higher per cent of correct diagnoses than Naples students in the interpretation of case histories. Overall, Malmö students reported most clinical experience and higher confidence than Naple students. CONCLUSIONS: The main findings were that students from Malmö and Naples were, similar in knowledge and understanding of TMD/OP and in satisfaction with their clinical competences. However, Malmö students perceived more confidence in clinical management of patients with TMD/OP. This may reflect that, besides the theoretical part of the programme, a sufficient level of clinical exposure to patients with TMD/OP is essential to gain competences in TMD/OP.

Expanding the taxonomy of the diagnostic criteria for temporomandibular disorders.

There is a need to expand the current temporomandibular disorders' (TMDs) classification to include less common but clinically important disorders. The immediate aim was to develop a consensus-based classification system and associated diagnostic criteria that have clinical and research utility for less common TMDs. The long-term aim was to establish a foundation, vis-à-vis this classification system, that will stimulate data collection, validity testing and further criteria refinement. A working group [members of the International RDC/TMD Consortium Network of the International Association for Dental Research (IADR), members of the Orofacial Pain Special Interest Group (SIG) of the International Association for the Study of Pain (IASP), and members from other professional societies] reviewed disorders for inclusion based on clinical significance, the availability of plausible diagnostic criteria and the ability to operationalise and study the criteria. The disorders were derived from the literature when possible and based on expert opinion as necessary. The expanded TMDs taxonomy was presented for feedback at international meetings. Of 56 disorders considered, 37 were included in the expanded taxonomy and were placed into the following four categories: temporomandibular joint disorders, masticatory muscle disorders, headache disorders and disorders affecting associated structures. Those excluded were extremely uncommon, lacking operationalised diagnostic criteria, not clearly related to TMDs, or not sufficiently distinct from disorders already included within the taxonomy. The expanded TMDs taxonomy offers an integrated approach to clinical diagnosis and provides a framework for further research to operationalise and test the proposed taxonomy and diagnostic criteria.

Reliability of electromyographic activity vs. bite-force from human masticatory muscles.

The reproducibility of electromyographic (EMG) activity in relation to static bite-force from masticatory muscles for a given biting situation is largely unknown. Our aim was to evaluate the reliability of EMG activity in relation to static bite-force in humans. Eighty-four subjects produced five unilateral static bites of different forces at different biting positions on molars and incisors, at two separate sessions, and the surface EMG activities were recorded from temporalis, masseter, and suprahyoid muscles bilaterally. Intraclass correlation coefficients (ICCs) were determined, and an ICC of ≥ 0.60 indicated good reliability of these slopes. The ICCs for jaw-closing muscles during molar biting were: temporalis muscles, ipsilateral 0.58-0.93 and contralateral 0.88-0.91; and masseter muscles, ipsilateral 0.75-0.86 and contralateral 0.69-0.88. The ICCs for jaw-closing muscles during incisor biting were: temporalis muscles, ipsilateral 0.56-0.81 and contralateral 0.34-0.86; and masseter muscles, ipsilateral 0.65-0.78 and contralateral 0.59-0.80. For the suprahyoid muscles the 95% CIs were mostly wide and most included zero. The slopes of the EMG activity vs. bite-force for a given biting situation were reliable for temporalis and masseter muscles. These results support the use of these outcome measurements for the estimation and validation of mechanical models of the masticatory system.

COMT Genotype and Efficacy of Propranolol for TMD Pain: A Randomized Trial.

Propranolol is a nonselective ß-adrenergic receptor antagonist that is efficacious in reducing facial pain. There is evidence that its analgesic efficacy might be modified by variants of the catechol-O-methyltransferase (COMT) gene. We tested the hypothesis in a subset of 143 non-Hispanic Whites from a randomized controlled trial of patients with painful temporomandibular disorder (TMD). Patients were genotyped for rs4680, a single nucleotide polymorphism of COMT, and randomly allocated to either propranolol 60 mg twice daily or placebo. During the 9-wk follow-up period, patients recorded daily ratings of facial pain intensity and duration; the product was computed as an index of facial pain. Postbaseline change in the index at week 9 (the primary endpoint) was analyzed as a continuous variable and dichotomized at thresholds of ≥30% and ≥50% reduction. Mixed models for repeated measures tested for the genotype × treatment group interaction and estimated means, odds ratios (ORs), and 95% confidence limits (95% CLs) of efficacy within COMT genotypes assuming an additive genetic model. In secondary analysis, the cumulative response curves were plotted for dichotomized reductions ranging from ≥20% to ≥70%, and genotype differences in area under the curve percentages (%AUC) were calculated to signify efficacy. Mean index reduction did not differ significantly (P = 0.277) according to genotype, whereas the dichotomized ≥30% reduction revealed greater efficacy among G:G homozygotes (OR = 10.9, 95%CL = 2.4, 50.7) than among A:A homozygotes (OR = 0.8, 95%CL = 0.2, 3.2) with statistically significant interaction (P = 0.035). Cumulative response curves confirmed greater (P = 0.003) efficacy for G:G homozygotes (%AUC difference = 43.7, 95%CL = 15.4, 72.1) than for A:A homozygotes (%AUC difference = 6.5, 95%CL = -30.2, 43.2). The observed antagonistic effect of the A allele on propranolol's efficacy was opposite the synergistic effect hypothesized a priori. This unexpected result highlights the need for better knowledge of COMT's role in pain pathogenesis if the gene is to be used for precision-medicine treatment of TMD (ClinicalTrials.gov NCT02437383).

Assessment and further development of RDC/TMD Axis II biobehavioural instruments: a research programme progress report.

A symposium was held in Toronto, 2008, in which research progress regarding the biobehavioural dimension of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was presented. An extended workshop was held in April 2009 in which further recommendations were made from an expert panel, using the 2008 symposium material as a base. This paper is a summary of the 2008 symposium proceedings with elaborations based on further developments. Seven studies were conducted between 2001 and 2008, in which the following were investigated: (i) basic properties of Axis II instruments, (ii) reliability and criterion validity of Axis II instruments, (iii) expansion of predictors, (iv) metric equivalence of the depression and non-specific physical symptoms subscales in the RDC/TMD, (v) laboratory investigation of oral behaviours, (vi) field data collection of oral behaviours, and (vii) functional limitation of the jaw. Methods and results for each of these studies are described. Based on the results of these studies that have been published, as well as the direction of interim results from the few studies that await completion and publication, the biobehavioural domain of the RDC/TMD, as published in 1992, is reliable and valid. These results also provide strong evidence supporting the future growth of the biobehavioural domain as the RDC/TMD matures into subsequent protocols for both clinical and research applications.

Disability assessment in temporomandibular disorders and masticatory system rehabilitation.

The consequences of a disease or condition such as temporomandibular disorders (TMD) include functional limitation and psychosocial disability. These two concepts refer to the individual's experience of limitations in function associated with the affected part of the body and to disarray in one's life, respectively. Models of disability emphasize the individual's self-report in describing these states and the centrality of these concepts as part of the disease and illness process. However, assessment approaches typically used in medicine and especially in dentistry do not yet routinely include these domains. TMD, as a musculoskeletal pain condition, can clearly lead to both limitation and disability, and the available evidence suggests that dentofacial disorders can also lead to both consequences. The relatively low contribution of disease impairment (measured changes in function through objective tests), however, to the reported limitation or disability in either TMD or dentofacial disorders remains complex and poorly understood. This article reviews the overall model of disablement, the necessary properties of measures to assess disablement, the present state of knowledge about these concepts, and what measures should be considered as part of routine assessment.

Oral rehabilitation, disability and dentistry.

This invited commentary explores the concept of oral rehabilitation and the relevance of the biopsychosocial model to it. Specifically, it discusses the implications of changing the definition of oral rehabilitation and incorporating the biopsychosocial model more fully in dental medicine. The biopsychosocial model's relevance to dentistry is exemplified through demonstrating its existing, and potential, applications to the assessment and rehabilitation of Temporomandibular Disorders.

Recommendations from the International Consensus Workshop: convergence on an orofacial pain taxonomy.

This 2·5-day workshop was organized by the International RDC/TMD Consortium Network of the International Association for Dental Research and the Orofacial Pain Special Interest Group of the International Association for the Study of Pain. Workshop participation was by invitation based on representation within the field, which included the Consortium Network, the Orofacial Pain Special Interest Group, the National Institute for Dental and Craniofacial Research, American Academy of Orofacial Pain, the European Academy of Craniomandibular Disorders, and the International Headache Society; other disciplines included radiology, psychology, ontology, and patient advocacy. The workshop members were divided into workgroups that reviewed core literature describing the properties of the RDC/TMD, provided recommendations for revision, and suggested relevant research directions. The goals of this workshop were to (i) finalize the revision of the RDC/TMD into a Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), which would be more appropriate for routine clinical implementation, (ii) provide a broad foundation for the further development of suitable diagnostic systems for not only TMD but also oro-facial pain as well, and (iii) provide research recommendations oriented towards improving our understanding of TMD and oro-facial pain. This report provides the full description of the workshop and Executive Summary, and it acknowledges the participants and sponsors.

Pain Sensitivity Modifies Risk of Injury-Related Temporomandibular Disorder.

This study evaluates contributions of jaw injury and experimental pain sensitivity to risk of developing painful temporomandibular disorder (TMD). Data were from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) nested case-control study of incident painful TMD. Injury and subsequent onset of painful TMD were monitored prospectively for ≤5 y in a community-based sample of 409 US adults who did not have TMD when enrolled. At baseline, thermal-pressure and pinprick pain sensitivity, as potential effect modifiers, were measured using quantitative sensory testing. During follow-up, jaw injury from any of 9 types of potentially traumatic events was determined using quarterly (3-monthly) health update questionnaires. Study examiners classified incident painful TMD, yielding 233 incident cases and 176 matched controls. Logistic regression models, estimated incidence odds ratios (IORs), and 95% confidence limits (CLs) were used for the association between injury and subsequent onset of painful TMD. During follow-up, 38.2% of incident cases and 13.1% of controls reported 1 or more injuries that were 4 times as likely to be intrinsic (i.e., sustained mouth opening or yawning) as extrinsic (e.g., dental visits, whiplash). Injuries due to extrinsic events (IOR = 7.6; 95% CL, 1.6-36.2), sustained opening (IOR = 5.4; 95% CL, 2.4-12.2), and yawning (IOR = 3.4; 95% CL, 1.6-7.3) were associated with increased TMD incidence. Both a single injury (IOR = 6.0; 95% CL, 2.9-12.4) and multiple injuries (IOR = 9.4; 95% CL, 3.4,25.6) predicted greater incidence of painful TMD than events perceived as noninjurious (IOR = 1.9; 95% CL, 1.1-3.4). Injury-associated risk of painful TMD was elevated in people with high sensitivity to heat pain (IOR = 7.4; 95% CL, 3.1-18.0) compared to people with low sensitivity to heat pain (IOR = 3.9; 95% CL, 1.7-8.4). Jaw injury was strongly associated with elevated painful TMD risk, and the risk was amplified in subjects who had enhanced sensitivity to heat pain at enrollment. Commonly occurring but seemingly innocuous events, such as yawning injury, should not be overlooked when judging prognostic importance of jaw injury.

Static and dynamic mechanics of the temporomandibular joint: plowing forces, joint load and tissue stress.

OBJECTIVES - To determine the combined effects 1) of stress-field aspect ratio and velocity and compressive strain and 2) joint load, on temporomandibular joint (TMJ) disc mechanics. SETTING AND SAMPLE POPULATION - Fifty-two subjects (30 female; 22 male) participated in the TMJ load experiments. MATERIAL AND METHODS - In the absence of human tissue, pig TMJ discs were used to determine the effects of variables 1) on surface plowing forces, and to build a biphasic finite element model (bFEM) to test the effect of human joint loads and 2) on tissue stresses. In the laboratory, discs received a 7.6 N static load via an acrylic indenter before cyclic movement. Data were recorded and analysed using anova. To determine human joint loads, Research Diagnostic Criteria calibrated investigators classified subjects based on signs of disc displacement (DD) and pain (+DD/+pain, n = 18; +DD/-pain, n = 17; -DD/-pain, n = 17). Three-dimensional geometries were produced for each subject and used in a computer model to calculate joint loads. RESULTS - The combined effects of compressive strain, and aspect ratio and velocity of stress-field translation correlated with plowing forces (R(2) = 0.85). +DD/-pain subjects produced 60% higher joint loads (ANOVA, p < 0.05), which increased bFEM-calculated compressive strain and peak total normal stress. CONCLUSIONS - Static and dynamic variables of the stress-field and subject-dependent joint load significantly affect disc mechanics.