Painful and non-painful comorbidities associated with short- and long-term painful temporomandibular disorders: A cross-sectional study among adolescents from Brazil, Canada and France.

BACKGROUND: Temporomandibular disorder (TMD) pain is common among adolescents. The association between painful TMD and other comorbidities has been demonstrated. However, the difference between short-term (<6 months) and long-term (≥ 6 months) painful TMD is not yet clear. OBJECTIVE: The aim of this study was to assess the association between comorbidities and short- and long-term painful TMD among adolescents. METHODS: In this cross-sectional study, adolescents were recruited from Montreal (Canada), Nice (France) and Arceburgo (Brazil). Self-reported painful TMD, comorbidities, school absence and analgesic intake were assessed using reliable instruments. Multivariable logistic regression analyses were conducted to assess the study aims. RESULTS: The prevalence of short- and long-term painful TMD was estimated at 22.29% and 9.93% respectively. The number of comorbidities was associated with short- (OR = 1.71, 95%CI = 1.53-1.90) and long-term painful TMD (OR = 1.79, 95%CI = 1.55-2.08) compared to controls. Frequent headaches (ORshort-term  = 4.39, 95%CI = 3.23-5.98, ORlong-term  = 3.69, 95%CI = 2.45-5.57) and back pain (ORshort-term  = 1.46, 95%CI = 1.06-2.03, ORlong-term  = 1.69, 95%CI = 1.11-2.59) were associated with both painful TMD groups. Frequent neck pain (OR = 2.23, 95%CI = 1.53-3.26) and allergies were only associated with short-term painful TMD (OR = 1.54, 95%CI = 1.13-2.10). Frequent stomach pain was related to long-term (OR = 2.01, 95%CI = 1.35-3.26), and it was the only comorbidity significantly more frequent among the long than short-term TMD (OR = 1.82, 95%CI: 1.14-2.90). These analyses were adjusted by sex, age and city. CONCLUSION: In this multi-centre study, both short- and long-term painful TMD are associated with frequent headaches and back pain, whereas frequent neck pain and allergies are related to only short-term and frequent stomach pain with long-term painful TMD.

Psychophysical evaluation of somatosensory function in oro-facial pain: achievements and challenges.

AIM: This critical review describes key methodological aspects for a successful oro-facial psychophysical evaluation of the somatosensory system and highlights the diagnostic value of somatosensory assessment and management perspectives based on somatosensory profiling. METHODS: This topical review was based on a non-systematic search for studies about somatosensory evaluation in oro-facial pain in PubMed and Embase. RESULTS: The recent progress regarding the psychophysical evaluation of somatosensory function was largely possible due to the development and application of valid, reliable and standardised psychophysical methods. Qualitative sensory testing may be useful as a screening tool to rule out relevant somatosensory abnormalities. Nevertheless, the patient should preferably be referred to a more comprehensive assessment with the quantitative sensory testing battery if confirmation of somatosensory abnormalities is necessary. Moreover, the identification of relevant somatosensory alterations in chronic pain disorders that do not fulfil the current criteria to be regarded as neuropathic has also increased the usefulness of somatosensory evaluation as a feasible method to better characterise the patients and perhaps elucidate some underpinnings of the so-called 'nociplastic' pain disorders. Finally, an additional benefit of oro-facial pain treatment based on somatosensory profiling still needs to be demonstrated and convincing evidence of somatosensory findings as predictors of treatment efficacy in chronic oro-facial pain awaits further studies. CONCLUSION: Psychophysical evaluation of somatosensory function in oro-facial pain is still in its infancy but with a clear potential to continue to improve the assessment, diagnosis and management of oro-facial pain patients.

Comorbid conditions associated with painful temporomandibular disorders in adolescents from Brazil, Canada and France: A cross-sectional study.

BACKGROUND: Painful temporomandibular disorder (TMD) is common among adolescents. Presence of painful comorbidities may worsen painful TMD and impact treatment effectiveness. OBJECTIVE: The aim of this study was to assess the association between painful TMD and comorbidities. METHODOLOGY: In this cross-sectional study, adolescents were recruited in Montreal (Canada), Nice (France) and Arceburgo (Brazil). Reliable instruments were used to assess painful TMD and comorbidities. Multivariable logistic and linear regression analyses were conducted to assess the study aims. RESULTS: The prevalence of self-reported painful TMD was estimated at 31.6%; Arceburgo (31.6%), Montreal (23.4%) and Nice (31.8%). Painful TMD was more common among girls than boys (OR = 1.96). Painful TMD was associated with a higher number of comorbidities (OR = 1.77); Arceburgo (OR = 1.81), Montreal (OR = 1.80) and Nice (OR = 1.72). A stronger association was found between painful TMD and headaches (OR = 4.09) and a weaker one with stomach pain (OR = 1.40). Allergies were also related to painful TMD (OR = 1.43). CONCLUSION: Painful TMD was associated with comorbidities. Headaches were consistently associated with painful TMD. Other associations were modified by sex and/or covariates related to the cities where participants were recruited.

Construction and validation of an questionnaire for evaluating self-medication practised by patients with temporomandibular disorders.

AIMS: Despite the fact that self-medication associated with temporomandibular disorders is clinically quite common and is considerably harmful, there is no instrument in the literature to assess this practice. The aim of this study was to construct and validate a questionnaire to study this important issue specifically. METHODS: After completing the literature review, semi-structured interviews, focus group and pretest, the first version of the instrument resulted in 62 questions. After face validity testing, pretest and the necessary corrections and changes, the instrument had 41 questions and was administered for validation to a sample of 110 patients diagnosed with TMD according to the RDC/TMD (1992) criteria. RESULTS: According to factor analysis, seven questions with loadings below 0.30 were removed, with the final version consisting of 34 questions. The analysis of internal consistency and temporal stability showed values of 0.844 for Cronbach's alpha coefficient and a Kappa coefficient of 0.810, respectively, indicating that the instrument presents sufficient reliability and reproducibility for its proposed objective. After validation, with the ultimate goal of classifying patients according to the degree/intensity of self-medication, a classification was proposed that allowed the discrimination of results into three distinct groups regarding self-medication exposure: mild, moderate or severe, based on the self-medication raw point score. CONCLUSION: The results of the instrument validation process showed that it has suitable properties for evaluating the practice of self-medication in patients with TMD.

Gender differences in temporomandibular disorders in adult populational studies: A systematic review and meta-analysis.

The objective of this study was to systematically evaluate gender differences in the prevalence of TMD. A systematic review was performed in PubMed, EMBASE, Web of Science and LILACS in duplicate by two independent reviewers. The inclusion criteria were cross-sectional studies that reported the prevalence of TMD for men and women and that used the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I group diagnostic criteria:(group I = muscle disorders; group II = disc displacements; group III = arthralgias/arthritis/arthrosis).To be eligible for inclusion, studies must include adult individuals (>18 years) from a non-clinical population (ie without pre-diagnosis of TMD); in other words, from population-based studies. There were no restrictions on the year and language of publication. The quality of the articles was assessed by an adapted version of the Newcastle-Ottawa Scale(NOS), and the publication bias was assessed by a funnel plot graph. Data were quantitatively analysed by meta-analysis using odds ratio (OR) as the measure effect. The electronic search retrieved a total of 6104 articles, of which 112 articles were selected for full-text reading according to the eligibility criteria. By means of manual search, one study was retrieved. Five articles were selected for meta-analysis with a combined sample of 2518 subjects. Women had higher prevalence of TMD in all RDC/TMD diagnostic groups. The meta-analysis yielded the following results: (a) OR = 2.24 for global TMD (groups I, II and III combined), (b) OR = 2.09 for group I, (c) OR = 1.6 for group II and (d) OR = 2.08 for group III. The importance of gender in the development of TMD has been demonstrated, with a two times greater risk of women to develop it as compared to men.

Transcranial direct current stimulation and exercises for treatment of chronic temporomandibular disorders: a blind randomised-controlled trial.

To evaluate the effect of adding transcranial direct current stimulation (tDCS) to exercises for chronic pain, dysfunction and quality of life in subjects with temporomandibular disorders (TMD). Participants were selected based on the RDC/TMD criteria and assessed for pain intensity, pressure pain threshold over temporomandibular joint and cervical muscles and quality of life. After initial assessment, all individuals underwent a 4-week protocol of exercises and manual therapy, together with active or sham primary motor cortex tDCS. Stimulation was delivered through sponge electrodes, with 2 mA amplitude, for 20 min daily, over the first 5 days of the trial. A total of 32 subjects (mean age 24.7 ± 6.8 years) participated in the evaluations and treatment protocol. Mean pain intensity pre-treatment was 5.5 ± 1.4 for active tDCS group, and 6.3 ± 1.2 for sham tDCS. Both groups showed a decrease in pain intensity scores during the trial period (time factor--F(4.5,137.5) = 28.7, P < 0.001; group factor--F(1.0,30.0 = 7.7), P < 0.05). However, there were no differences between the groups regarding change in pain intensity (time*group interaction--F(4.5,137.5) = 1.5, P = 0.137). This result remained the same after 5 months (t-test t = 0.29, P > 0.05). Pressure pain thresholds decrease and improvement in quality of life were also noticeable in both groups, but again without significant differences between them. Absolute benefit increase was 37.5% (CI 95%: -15.9% to 90.9%), and number needed to treat was 2.66. This study suggests that there is no additional benefit in adding tDCS to exercises for the treatment of chronic TMD in young adults.

Reflejo C evocado en el músculo digástrico: un nuevo método para evaluar actividad wind-up trigeminal aplicable a principios activos de plantas medicinales / C-reflex evoked in the digastric muscle: a new method for evaluating trigeminal wind-up activity applicable to active principles of medicinal plants

Wind-up is a measure of nociceptive neurons synaptic potentiation and constitutes an important mechanism in the generation of central sensitization in chronic pain. At the spinal level, the C-evoked reflex in the bicep femoris muscle, by low frequency repetitive stimulation of the sural nerve, has enabled us to evaluate the wind-up of nociceptive neurons of the dorsal horn, and also the effect of antinociceptive drugs with a possible potential therapeutic value in chronic pain. In the present work, we electrophysiologically evaluated the trigeminal wind-up activity, utilizing as an experimental paradigm the evoked C-reflex in the Sprague-Dawley rat digastric muscle. The results obtained indicate that: (a) It is possible to evoke an electromyographic reflex in the digastric muscle by stimulation of C-fibers belonging to the third trigeminal branch; (b) It is possible to potentiate the trigeminal C-reflex with low frequency stimuli (wind-up) and (c) it is possible to depress the trigeminal wind-up with the μ-opioid agonist morphine and with the NMDA receptor antagonist, ketamine. We can conclude that the simple measurement of the trigeminal wind-up will facilitate future studies on the analgesic efficacy of new drugs in oro-facial chronic pain syndromes like migraine and with special emphasis on medicinal plant active principles.

El wind-up refleja la potenciación sináptica en neuronas nociceptivas y constituye un importante mecanismo en la generación de sensibilización central en dolor crónico. A nivel espinal, el reflejo C evocado en el músculo bicep femoris por estimulación repetitiva de baja frecuencia del nervio sural ha permitido evaluar la actividad wind-up en neuronas nociceptivas del cuerno dorsal, así como el efecto de drogas antinociceptivas con un posible potencial terapéutico en dolor crónico. En el presente trabajo evaluamos electrofisiológicamente la actividad wind-up trigeminal, utilizando como paradigma experimental el reflejo C evocado en el músculo digástrico de ratas Sprague-Dawley. Los resultados obtenidos indican que: (a) es posible evocar un reflejo electromiográfico en el músculo digástrico de la rata por estimulación de fibras C de la tercera rama del trigémino; (b) es posible potenciar el reflejo C trigeminal con estímulos de baja frecuencia (wind-up) y (c) es posible deprimir el wind-up trigeminal con el agonista μ-opioide morfina y con el antagonista NMDA, ketamina. Podemos concluir que la medición simple del wind-up trigeminal mediante el reflejo C evocado en el músculo digástrico facilitará futuros estudios sobre eficacia analgésica de nuevos fármacos en cuadros de dolor orofacial crónicos, como la migraña, con especial énfasis en los principios activos de plantas medicinales.