Journal of Oral & Facial Pain and Headache, 01/2009

The lack of standardized diagnostic criteria for defining clinical subtypes of temporomandibular disorders (TMD) was the main motive to create the Research Diagnostic Criteria for TMD (RDC/TMD), which were provided to allow standardization and replication of research into the most common forms of muscle- and joint-related TMD. The RDC/TMD offered improvement compared to the older literature: the use of one system classifying TMD subgroups and the introduction of a dual-axis classification. The aim of this Focus Article is to appraise the RDC/TMD Axis I (physical findings). Since the original publication in 1992, no modification of the RDC/TMD has taken place, although research has yielded important new findings. The article outlines several concerns, including diagnostic issues in Axis I, classification criteria, feasibility of palpation sites, the myofascial diagnostic algorithm, the lack of joint tests (compression, traction), and missing subgroups. Using a gold standard examiner may improve calibration and offer better reliability; it does not improve any of the diagnostic validity issues. It is also noted that in the 2004 mission statement of the International Consortium For RDC/TMD-Based Research, the RDC/TMD are also advocated for clinical settings. Clinicians may eagerly embrace the RDC/TMD, believing that the clinical use of the RDC/TMD as a diagnostic procedure is already supported by evidence, but its application is not indicated in clinical settings. The article concludes that given the research developments, there is a need to update the RDC/TMD Axis I in the clinical research setting.

The authors of the Focus Article1 present a critical appraisal of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I and its classification system. They recognize the impact that the cornerstone paper published by Dworkin and LeResche in 1992 has had on clinical research.2 Research has since yielded important changes and the authors raise a number of important issues, some being very well supported while others are more debatable. The authors conclude that the time has come to update and broaden the scope of the RDC/TMD, which should be more clinically oriented and better oriented to treatment decision making. My commentary addresses the major points from each of the four sections of the Focus Article.

The temporomandibular disorder (TMD) research community has been using the Research Diagnostic Criteria for TMD (RDC/TMD) since 1992, and its original developers have much to be proud of because of their widespread acceptance.1 They have accomplished their initial goal of getting researchers to use some common language in classifying TMD patients, and by forming the International Consortium for RDC/TMD-Based Research they have enabled clinical researchers around the world to apply this system in their native languages. However, even from the very beginning there have been some doubts and concerns about the validity as well as the utility of this taxonomic system. During the past 16 years, other classification systems for TMD such as the one proposed by the American Academy of Orofacial Pain (AAOP),2 as well as the broader headache classification system of the International Headache Society (IHS),3 have coexisted with the RDC/TMD, but a direct confrontation was avoided by describing the former two as clinical classifications while the latter was intended for research purposes.

The commentary by Drs Steenks and de Wijer1 is an important appraisal of the potential shortcomings of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD).2 Nothing is perfect and everything can be improved. Clinicians and researchers need to be aware of the pros and cons for any type of diagnostic or classification scheme of orofacial pain conditions and therefore a critical dissection of the merits of the RDC/TMD is much welcomed. The authors raise a number of questions and concerns and discuss them in a timely and fair manner. Nevertheless, I would like specifically to comment on two points.

The authors would like to thank Drs Goulet, Greene, and Svensson for their valuable comments on our Focus Article4 "Validity of the research diagnostic criteria for temporomandibular disorders Axis I in clinical and research settings." Because the Critical Commentaries in general are very supportive of the thoughts and suggestions brought forward in the Focus Article, we would like to add some comments on their use in children and adolescents in addition to our response to the Commentaries.

Aims: To evaluate the relationships between gender, diagnosis, and severity of temporomandibular disorders (TMD) with self-reports of the impact of TMD on the quality of life. Methods: Eighty-three individuals seeking TMD treatment at the Dental School of Pontifical Catholic University Minas from May to August 2005 were evaluated by a single examiner who was trained and calibrated for diagnosis according to criteria of Axis I of the Research Diagnostic Criteria for TMD (RDC/TMD). The severity of TMD was established by the Temporomandibular Index and the impact on quality of life by the Oral Health Impact Profile (OHIP 14). Complete data were available for 78 of the 83 initial patients and evaluated by the Mann-Whitney test and Spearman correlation analysis. Results: Except for one patient, all individuals showed some impact related to physical pain. Of the seven aspects evaluated on the OHIP 14, women presented a greater impact than men only for functional limitations (Mann-Whitney, P .05). Patients presenting with diagnoses of muscular disorders (group I) or osteoarthritis (group III) reported a greater impact than those without (P .05). The Spearman test demonstrated a significant correlation between impact on quality of life and severity of TMD (P .05). Conclusion: Orofacial pain had a great impact on the quality of life of individuals with TMD, without group difference between genders. The presence of muscular disorders (group I) and osteoarthritis (group III) was related to greater impact on quality of life, which was not observed for diagnoses of disc displacement (group II). A correlation between severity of TMD and impact on quality of life was clearly observed.

Aims: To examine the associations between the ethnic backgrounds of temporomandibular disorder (TMD) patients in the Netherlands and the level of TMD pain complaints and psychological/behavioral factors and whether these associations are influenced by socioeconomic factors. Methods: A sample of 504 consecutive patients from a TMD clinic completed the Research Diagnostic Criteria for TMD (RDC/TMD) Axis II questionnaire (pain intensity, pain-related disability, somatization, depression, ethnic background, and socioeconomic status), an oral parafunctions questionnaire, and questions related to stress. Ethnic background was classified, following the method of Statistics Netherlands (CBS), using the country of birth from subject and both parents. This resulted in a classification into three subgroups: Native Dutch (ND; 69.6%), Non-Native Western (NNW; 14.8%), and Non-Native Non-Western (NNNW; 15.6%). Statistics used were chi-square, one- and two-way ANOVA, and Kruskall-Wallis tests; for post-hoc interpretation, standardized residual values, Bonferroni, and Mann-Whitney U tests were used. Results: No differences in age or gender were found between the three ethnic groups, nor were there any differences in characteristic pain intensity or oral parafunctions. However, TMD patients from the NNNW subgroup had significantly higher scores on psychological factors, namely pain-related disability, disability days, somatization, depression, and stress. These patients had a lower incidence of employment, a lower level of education, and a lower income level than patients from the ND and NNW ethnic backgrounds. Analysis of variance showed no interaction effects between ethnic background and socioeconomic factors in relation to the psychological variables mentioned. Conclusion: Ethnic background of TMD patients in the Netherlands is associated with psychological factors, regardless of socioeconomic status, but not with TMD pain complaints or oral parafunctions. Keywords: ethnic background, pain, pain-related disability, socioeconomic status, temporomandibular disorders

Aims: To define treatment success from the facial pain and fibromyalgia pain patient perspective across four domains (pain, fatigue, emotional distress, interference with daily activities) through the use of the Patient-Centered Outcomes (PCO) Questionnaire. Methods: Participants included 53 facial pain (46 women, seven men) and 52 fibromyalgia (49 women, three men) patients who completed the PCO Questionnaire. The PCO assesses four relevant domains of chronic pain: pain, fatigue, distress, and interference in daily activities. Participants rated their usual levels, expected levels, levels they considered successful improvements, and how important improvements were in each of the four domains following treatment. Repeated-measures analyses of variance were performed to determine whether differences existed across domains and across pain groups. Results: Both groups of participants defined treatment success as a substantial decrease in their pain, fatigue, distress, and interference ratings (all approximately 60%). Fibromyalgia participants reported high levels of pain (mean = 7.08, SD = 2.04), fatigue (mean = 7.82, SD = 1.71), distress (mean = 6.35, SD = 2.46), and interference (mean = 7.35, SD = 2.21). Facial pain participants' ratings of these domains were significantly lower for pain (mean = 5.62, SD = 2.38), fatigue (mean = 5.28, SD = 2.64), distress (mean = 4.34, SD = 2.78), and interference (mean = 4.10, SD = 3.06). Conclusion: These results demonstrate the high expectations of individuals with facial pain and fibromyalgia regarding treatment of their symptoms. Health care providers should incorporate these expectations into their treatment plans and discuss realistic treatment goals with their pain patients. Keywords: facial pain, fibromyalgia, patient-centered care, treatment outcome, pain/psychology

Aims: To compare patients with temporomandibular disorders (TMD) to control subjects on two measures of central processing, ie, temporal summation of heat pain and decay of subsequent aftersensations, following thermal stimulation in both a trigeminal and extratrigeminal area. Methods: A "wind-up" protocol was used in which 19 female TMD patients and 17 female controls were exposed to 15 heat stimuli at a rate of 0.3 Hz. Numeric pain ratings were elicited after the 1st, 5th, 10th, and 15th stimulus presentation and every 15 seconds after final presentation (aftersensations) for up to 2 minutes. In separate trials, the thermode was placed on the thenar eminence of the hand and the skin overlying the masseter muscle. Results: Groups did not differ with respect to the slope of wind-up when stimulated at either anatomic site, although asymptotic levels occurred sooner for TMD patients than for controls. In analysis of aftersensations, a significant group x site x time interaction was detected, in which TMD patients experienced more prolonged painful aftersensations than controls when stimulated on the skin overlying the masseter muscles. Conclusion: These results are consistent with the presence of enhanced central sensitivity in TMD and suggest that this sensitivity may be largely confined to the region of clinical pain. This contrasts with conditions such as fibromyalgia, where central sensitivity appears to be widespread. Keywords: aftersensations, chronic pain, temporal summation, temporomandibular disorders, wind-up

Aims: Recent evidence suggests that the purinoceptor P2X7 may be involved in the development of dysesthesia following nerve injury, therefore, the aim of the present study was to investigate whether a correlation exists between the level of P2X7 receptor expression in damaged human lingual nerves and the severity of the patients' symptoms. Methods: Neuroma-in-continuity specimens were obtained from patients undergoing surgical repair of the damaged lingual nerve. Specimens were categorized preoperatively according to the presence or absence of dysesthesia, and visual analog scales scores were used to record the degree of pain, tingling, and discomfort. Indirect immunofluorescence using antibodies raised against S-100 (a Schwann cell marker) and P2X7 was employed to quantify the percentage area of S-100 positive cells that also expressed P2X7. Results: P2X7 was found to be expressed in Schwann cells of lingual nerve neuromas. No significant difference was found between the level of P2X7 expression in patients with or without symptoms of dysesthesia, and no relationship was observed between P2X7 expression and VAS scores for pain, tingling, or discomfort. No correlation was found between P2X7 expression and the time between initial injury and nerve repair. Conclusion: These data show that P2X7 is expressed in human lingual nerve neuromas from patients with and without dysesthesia. It therefore appears that the level of P2X7 expression at the injury site may not be linked to the maintenance of neuropathic pain after lingual nerve injury. Keywords: dysesthesia, immunohistochemistry, lingual nerve, nerve injury, P2X7