Temporomandibular Disorders Subgroups Research Articles

Investigation of the masseter and temporalis muscles thicknesses in individuals with and without temporomandibular disorders by ultrasonography: A randomized controlled study

Aim: The aim was to evaluate the impact of different temporomandibular disorder (TMD) diagnoses on the thickness of the masseter and temporalis muscles. Materials and Methods: Individuals were divided into four groups: (1) myofascial pain; (2) disc displacements; (3) mixed group; and (4) asymptomatic control group. 53 individuals with TMD and 20 individuals without TMD were recruited. Results: No significant differences were found among groups in masseter and temporalis muscles thickness at rest and maximum contraction (p>0.05). However, the masseter muscle thickness at rest and maximum contraction were greater in asymptomatic individuals than in individuals with TMD (p<0.05). Conclusion: Masseter and temporalis muscles thickness are similar in the TMD subgroups and the asymptomatic control group at rest and maximum contraction.

Updating The General Practitioner on The Association Between Teeth Loss and Temporomandibular Disorders: A Systematic Review.

The belief about a possible association between the absence of one or more teeth and the presence of temporomandibular disorders (TMD), although old, is still present among the dental class. Although evidence points to a lack of association between loss of posterior support and the presence of TMD, we do not have critical studies on the extent, quantity, or location of these losses. In this sense, this systematic review aims to investigate the association between tooth loss and the presence of TMD signs or diagnostic subgroups. Search strategies using a combination of keywords tooth loss and TMDs were performed in six databases (PubMed, Embase, Web of Science, Livivo, Lilacs, and Scopus) and gray literature from August to September 2020. Observational studies that investigated the association between tooth loss in TMD were considered. The risk of bias was assessed using the Joanna Briggs Institute (JBI) Critical Assessment Checklist for cross-sectional analytical studies, case-control, and cohort studies. Finally, the level of certainty measured by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was assessed. Six articles were included in the review according to the eligibility criteria. Of these, five had a high risk of bias and one had a moderate risk. Only one study showed an association between the loss of posterior teeth and the presence of joint sounds and joint pain, the others found no significant association with sign or TMD subgroups diagnostic.There is no scientific evidence to support the association between one or more tooth loss and the presence of TMD signs and symptoms or diagnostic subgroups.

Psychosocial profiles and their correlation with physical diagnosis in temporomandibular disorders, a preliminary report

ABSTRACT Objective To assess representative psychosocial features in a group of temporomandibular disorder (TMD) patients from Jordan using Axis II of the Diagnostic Criteria for TMD (DC/TMD) protocol. Methods Ninety-eight TMD patients were examined according to Axis I DC/TMD protocol in addition to assessment of their pain-related disability, psychological distress, and stress reactivity. Results Just under half of the patients (49%) had high intensity of characteristic pain (self-reported TMJ-related pain) and one-third (32%) had high levels of pain-related disability. Furthermore, significant proportions of patients expressed moderate-severe degrees of distress and stress reactivity (41% and 39%, respectively). Significant correlations were identified between the Graded Chronic Pain Scale (GCPS) and each of the pain-related TMD subgroups. Conclusion TMD patients are susceptible to high levels of pain-related psychosocial impairment, and clinicians should be aware of the possible correlations between the physical TMD diagnosis and specific psychosocial features during treatment planning.

Association between waking-state oral behaviours, according to the oral behaviors checklist, and TMD subgroups.

ObjectivesTo assess the association between waking‐state oral behaviours and temporomandibular disorder (TMD) subgroups and to develop new scoring methods for the Oral Behavior Checklist (OBC).MethodsPatients with any TMD diagnosis, according to the diagnostic criteria for TMD (DC/TMD), were divided into subgroups: ‘Dysfunctional‐TMD’ (n = 70), only mechanical dysfunction; ‘Painful‐TMD’ (n = 204), only myalgia, arthralgia or both; and ‘Painful‐Dysfunctional TMD’ (n = 95), combined pain and dysfunction. A group of individuals without TMD, ‘Non‐TMD’ (n = 374), was used for testing associations. Participants completed the OBC. An exploratory factor analysis, followed by a confirmatory factor analysis of the OBC responses, identified 2 major factors, named non‐functional activities (NFA) and functional activities (FA). Component total scores were computed. Differences among subgroups for OBC‐MS (mean score) and NFA and FA factor scores were estimated using one‐way ANOVA and Tukey post hoc tests. Significance was set at p < .05.ResultsThe OBC‐MS in Non‐TMD, Painful‐TMD and Painful‐Dysfunctional TMD subgroups was higher than in the Dysfunctional‐TMD subgroup (p ≤ .001). NFA in Painful‐TMD and Painful‐Dysfunctional TMD subgroups were higher than in the Non‐TMD group (p < .05); NFA in the Dysfunctional‐TMD subgroup were lower than in the Painful‐TMD subgroup (p = .034). In contrast, FA in Painful‐TMD, Dysfunctional‐TMD and Painful‐Dysfunctional TMD subgroups were lower than in the Non‐TMD group (p < .0001).ConclusionsA new scoring method for the OBC results in item reduction and creation of meaningful subscales for functional and non‐functional behaviours, which are differentially associated with painful and dysfunctional TMDs. This may help clinicians to better tailor treatment for the management of subtypes of TMD patients.

Is jaw muscle activity impaired in adults with persistent temporomandibular disorders? A systematic review and meta-analysis.

Understanding jaw muscle activity changes in temporomandibular disorders (TMD) is crucial to guide clinical management. The nature of these changes is currently unclear. Explore changes in jaw muscle activity in TMD. Electronic databases (PubMed, EMBASE, CINAHL, Scopus, Web of Science, Cochrane) and bibliographies were searched from inception to 9 July 2020 for eligible studies, including grey literature. Case-control and interventional studies reporting time-domain and frequency-domain electromyographic measures of jaw muscle activity in TMD and control groups were included. SIGN checklist for case-control studies was used to evaluate risk of bias. Results were pooled for meta-analysis using random-effects model. Confidence in cumulative evidence was established using American Academy of Neurology guidelines. Forty-five studies were included. Most were rated moderate risk of bias. Activity of four muscles (masseter, temporalis, lateral pterygoid, suprahyoids) was assessed across six domains (resting, clenching, chewing, swallowing, concentrating, resisted mandibular movements), with partial meta-analysis scope. Masseter and temporalis activity were significantly higher at rest (P=.05, P<.0001), but lower during brief maximal clenching (P=.005, P=.04) in TMD vs controls. Insufficient data precluded meta-analysis of remaining outcomes and subgroup analysis. Confidence in cumulative evidence ranged from moderate to very low. Changes in jaw muscle activity exist in TMD, which are both task-specific and muscle-specific. It remains unclear whether jaw muscle activity changes vary between TMD subgroups. Muscle function should be considered in clinical management of TMD. Insufficient subgroup data highlight future direction for research.

Clinical Reasoning for the Examination and Physical Therapy Treatment of Temporomandibular Disorders (TMD): A Narrative Literature Review.

The current narrative literature review aims to discuss clinical reasoning based on nociceptive pain mechanisms for determining the most appropriate assessment and therapeutic strategy and to identify/map the most updated scientific evidence in relation to physical therapy interventions for patients with temporomandibular disorders (TMDs). We will also propose an algorithm for clinical examination and treatment decisions and a pain model integrating current knowledge of pain neuroscience. The clinical examination of patients with TMDs should be based on nociceptive mechanisms and include the potential identification of the dominant, central, or peripheral sensitization driver. Additionally, the musculoskeletal drivers of these sensitization processes should be assessed with the aim of reproducing symptoms. Therapeutic strategies applied for managing TMDs can be grouped into tissue-based impairment treatments (bottom-up interventions) and strategies targeting the central nervous system (top-down interventions). Bottom-up strategies include joint-, soft tissue-, and nerve-targeting interventions, as well as needling therapies, whereas top-down strategies include exercises, grade motor imagery, and also pain neuroscience education. Evidence shows that the effectiveness of these interventions depends on the clinical reasoning applied, since not all strategies are equally effective for the different TMD subgroups. In fact, the presence or absence of a central sensitization driver could lead to different treatment outcomes. It seems that multimodal approaches are more effective and should be applied in patients with TMDs. The current paper also proposes a clinical decision algorithm integrating clinical diagnosis with nociceptive mechanisms for the application of the most appropriate treatment approach.

Are jaw range of motion, muscle function and proprioception impaired in adults with persistent temporomandibular disorders? A systematic review and meta-analysis.

The nature of certain musculoskeletal impairments associated with temporomandibular disorders (TMD) is unclear. Understanding impairments within TMD subgroups is important to guide management. Characterise local musculoskeletal impairments in adults with persistent TMD. PubMed, EMBASE, CINAHL, Scopus, Web of Science and Cochrane databases were searched from inception to 12 January 2020. Bibliographies were searched for additional articles, including grey literature. Case-control and interventional studies reporting temporomandibular range of motion (ROM), muscle function (MF) or proprioception in TMD and control groups were included. Risk of bias was assessed using SIGN checklist for case-control studies. Results were pooled using random-effects model. Confidence in cumulative evidence was determined using American Academy of Neurology guidelines. Sixty-six studies were included, most rated moderate risk of bias. Twelve primary outcomes were assessed, with partial scope for meta-analysis. Significant reductions were found for active maximal mouth opening (P<.00001, MD=-4.65mm), protrusion (P<.0001, MD=-0.76mm) and maximum bite force (P<.00001) in TMD versus controls. Subgroup analysis scope was limited. Reduced AMMO was found in myogenic TMD subgroups versus controls (P=.001, MD= -3.28mm). Few studies measured proprioception, with high methodological variability. Confidence in cumulative evidence ranged from high to very low. ROM and bite force impairments accompany TMD. Insufficient data were available to investigate impairments within TMD subgroups. Several musculoskeletal impairments have been identified, which may guide clinical management of TMD. Lack of subgroup data, and data for proprioception and MF, highlights future direction for research. CRD42020150734.

Polymorphisms in COL2A1 gene in Adolescents with Temporomandibular Disorders.

Temporomandibular disorder (TMD) is considered a functional disorder with multifactorial aspects. The goal of this study was to investigate if genetic polymorphisms in the COL2A1 gene could be associated with TMD in adolescents. The case group (TMD-affected) included individuals diagnosed with any of the following TMD subgroups according to the RDC/TMD criteria: myofascial pain, disc displacements and arthralgia. Genomic DNA for molecular analysis was extracted from buccal cells and genetic polymorphisms in COL2A1 were genotyped by real time polymerase chain reactions using the TaqMan assay. Data were analyzed using the Epi Info 3.5.7 and Stata software. 249 subjects were included in this study (148 subjects "affected" by TMD). There were no significant differences between the affected and unaffected individual (p>0.05), for TMD, arthralgia and myofascial pain however, rs2276454 was borderline in the genotype distribution (p=0.07) and was associated with disc displacement (p=0.03) in the allelic distribution. Recessive model showed significant differences between groups for with disc displacement (p=0.02). Genetic polymorphisms in COL2A1 are not associated with myofascial pain, arthralgia or TMD in adolescents but this study provides evidence that rs2276454 is involved in the disc displacement of the temporomandibular joint.

Eye Pain in Patients with Arthrogenous Versus Myogenous Temporomandibular Disorder Presenting to An Otolaryngology Clinic.

Abstract Objective: The issue of eye pain in patients with temporomandibular disorders (TMD) had not been previously addressed; specifically, in relation to the two major subgroups of TMD; arthrogenous and myogenous. The present study aimed to compare the incidence and pattern of eye pain in arthrogenous versus myogenous TMD. Methods: The study involved 314 consecutive patients with TMD, prospectively examined over a period of 6 months. These were stratified into 193 patients with arthrogenous TMD and 121 patients with myogenous TMD. The pattern of any eye pain in each patient was studied. Results: Eye pain was present in 78 per cent of TMD patients. It was more commonly encountered in myogenous versus arthrogenous TMD patients. Approximately one-quarter of patients in either group had TMD-related eye pain. Conclusion: Eye pain is significantly associated with TMD. The presence of eye pain augments the morbidity of TMD in patients afflicted with both disorders.

Association between convergence insufficiency and temporomandibular disorder cross-sectional study.

Evaluate whether there is an association between convergence insufficiency and temporomandibular disorder (TMD) and whether there is an association between pain and range of motion in different degrees of TMD. We evaluated 138 individuals with TMD and 46 without TMD using the Research Diagnostic Criteria for temporomandibular disorders, the Fonseca Anamnestic Index (FAI), Numeric Pain Rating Scale, and the measurement of mandibular range of motion (ROM). Convergence insufficiency was diagnosed using the convergence test and Convergence Insufficiency Symptom Survey. Analysis of variance was used to compare age and mandibular ROM. The Kruskal-Wallis was used to compare mandibular ROM and pain between groups. The chi-square test was used to evaluate associations between TMD subgroups and the FAI, sex, and ocular convergence. The majority of individuals without TMD did not exhibit convergence insufficiency. The frequency convergence insufficiency was significantly higher among individuals with severe TMD (p < 0.003). Mean pain severity differed between individuals with and without TMD. Mandibular ROM diminished with the increase in TMD severity. Convergence insufficiency, age, the increase in pain, and the reduction in mandibular range of motion were associated with the degrees of TMD severity. Despite the significant associations between convergence insufficiency and both pain and TMD severity, these variables cannot be indicated as predictive factors due to the low variability in the linear regression analysis. The present findings can assist in decision making regarding the treatment of severe TMD and the evaluation of ocular convergence.

Cervical Muscle Tenderness in Temporomandibular Disorders and Its Associations with Diagnosis, Disease-Related Outcomes, and Comorbid Pain Conditions.

To analyze cervical tenderness scores (CTS) in patients with various temporomandibular disorders (TMD) and in controls and to examine associations of CTS with demographic and clinical parameters. This case-control study included 192 TMD patients and 99 controls diagnosed based on a questionnaire and a clinical examination following the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) guidelines. CTS, adapted from the widely used total tenderness score, was the mean sum of the palpation scores from the suboccipital, sternocleidomastoid, and trapezius muscles. Depending on the variables, data were analyzed using Pearson chi-square, analysis of variance, t test, Bonferroni post hoc adjustment, and/or multivariate linear regression analyses. CTS was higher in TMD compared to controls (P < .001). Across TMD subgroups, CTS was notable only in those with a myogenous TMD diagnosis, but not in arthrogenous TMD (P = .014). CTS was positively associated with: female sex (P = .03), whiplash history, higher verbal pain scores, comorbid headaches, body pain, increased pain on mouth opening, and higher masticatory muscles tenderness scores (MTS) (P < .001 for all). Sex (P < .001), MTS (P < .001), comorbid headache (P = .042), and pain on opening (mild: P = .031; moderate: P = .022) retained significant associations with CTS in the multivariate analysis, and these main effects were influenced by interactions with whiplash history and comorbid body pain. CTS differentiated between TMD patients and controls and between TMD diagnoses. Specific patient and pain characteristics associated with poor outcome in terms of CTS included effects of interactions between myogenous TMD, female sex, whiplash history, comorbid body pain and headaches, and pain on opening. It can therefore be concluded that routine clinical examination of TMD patients should include assessment of the cervical region.

Dopamine receptor D2 and ankyrin repeat domain containing one in temporomandibular disorder of adolescents.

Temporomandibular disorder (TMD) is a multifactorial condition that combines environmental and genetic factors and its prevalence increases during adolescence. To investigate the association between TMD and genetic polymorphisms in the DRD2 and ANKK1 in a population of Brazilian adolescents. The TMD group included adolescents diagnosed with any of the following TMD subgroups according to the RDC/TMD criteria: myofascial pain, arthralgia and disc displacement and painful TMD. Genomic DNA for molecular analysis was extracted from buccal cells, and genetic polymorphism rs6275 in DRD2 and rs1800497 in ANKK1 were genotyped by real-time polymerase chain reactions using the TaqMan assay. Data were analysed using the Epi Info 3.5.7 and Stata software, with significance level of 0.05. Two hundred fifty-one individuals were included in this study, 148 subjects presented TMD. For disc displacement, the genetic polymorphisms rs6275 was associated in a recessive model (P=0.04), whereas the rs6276 and rs1800497 presented only a borderline association in a recessive and dominant models, respectively (P=0.07 and P=0.06). The genetic polymorphism rs6275 in DRD2 was associated with disc displacement in Brazilian adolescents.

Muscle tenderness score in temporomandibular disorders patients: A case‐control study

The total tenderness score (TTS) is commonly used in headache practice and contributes valuable information. To assess muscle tenderness scores in patients diagnosed with Temporomandibular disorders (TMD) and analyse their associations with various demographic and clinical parameters. Masticatory (MTS), cervical (CTS) and TTSs were analysed in this case-control study among 192 TMD patients and 99 controls. The study included a questionnaire and a clinical examination following RDC/TMD guidelines. Data were analysed using: Pearson's chi-square, analysis of variance, t test and Bonferroni post hoc. To examine the factors associated with MTS score in a multivariate manner, a conceptual hierarchical multiple regression model was adopted. Masticatory and TTS differed between TMD sub-groups and controls. Muscle tenderness was positively associated with: female sex, whiplash history, parafunction, co-morbid pains such as headaches and body pain, pain intensity, onset, frequency and duration. In the conceptual hierarchical multiple regression model, pain onset, frequency and duration, co-morbid pains were mediators in the relationship between TMD diagnosis and MTS. Muscle tenderness scores were positively associated with TMD disease characteristics and co-morbid pain conditions, which may reflect associations with disease severity. MTS differed between TMD populations and may be used in routine patient workup, to assess MMD severity and changes over time as well as treatments response and as a research tool. MTS can be used as a common methodology to describe both headaches and masticatory muscle disorders and to facilitate interprofessional research and crosstalk between a headache and oro-facial pain practitioners.

Psychopathologic Profiles of TMD Patients with Different Pain Locations

The aim of this study was to examine whether psychopathologic profile is related to the location of pain in temporomandibular disorder (TMD) patients with myofascial and/or temporomandibular joint pain. A total of 75 painful TMD patients (39 women and 36 men) participated in the study. Participants were divided into three groups (myogenous, arthrogenous, and mixed) using the Research Diagnostic Criteria for TMD (RDC/TMD) Axis I guidelines for assessment of TMD signs and symptoms. Three psychometric instruments were used to assess the psychopathologic profile of the TMD subgroups. Patients' state and trait anxiety were assessed using the State-Trait Anxiety Inventory (STAI-S, STAI-T), depression was measured with the Center for Epidemiological Studies Depression Scale (CES-D), and psychosocial functioning was evaluated using the Global Disability Scale (Glo.Di.S). The three TMD groups were compared with Kruskal-Wallis test followed by pairwise Mann-Whitney tests relative to the psychometric scores. Statistical analyses were performed with SPSS 15.0 software. No significant differences were detected among the different TMD groups in the three psychometric scales; STAI-T, CES-D, Glo.Di.S (P > .05). When the psychometric scale of state anxiety (STAI-S) was considered, significant differences were revealed between the myogenous and the arthrogenous pain groups (P = .008) and also between the mixed and the arthrogenous groups (P < .001). These findings suggest that the psychopathologic profile is not related to the location of pain in TMD patients. However, anxiety was found to be higher in TMD patients with myogenous pain alone or combined with arthrogenous pain compared to those with only arthrogenous pain.

Correction: Rebamipide Attenuates Mandibular Condylar Degeneration in a Murine Model of TMJ-OA by Mediating a Chondroprotective Effect and by Downregulating RANKL-Mediated Osteoclastogenesis

[This corrects the article DOI: 10.1371/journal.pone.0154107.].

Rebamipide Attenuates Mandibular Condylar Degeneration in a Murine Model of TMJ-OA by Mediating a Chondroprotective Effect and by Downregulating RANKL-Mediated Osteoclastogenesis.

Temporomandibular joint osteoarthritis (TMJ-OA) is characterized by progressive degradation of cartilage and changes in subchondral bone. It is also one of the most serious subgroups of temporomandibular disorders. Rebamipide is a gastroprotective agent that is currently used for the treatment of gastritis and gastric ulcers. It scavenges reactive oxygen radicals and has exhibited anti-inflammatory potential. The aim of this study was to investigate the impact of rebamipide both in vivo and in vitro on the development of cartilage degeneration and osteoclast activity in an experimental murine model of TMJ-OA, and to explore its mode of action. Oral administration of rebamipide (0.6 mg/kg and 6 mg/kg) was initiated 24 h after TMJ-OA was induced, and was maintained daily for four weeks. Rebamipide treatment was found to attenuate cartilage degeneration, to reduce the number of apoptotic cells, and to decrease the expression levels of matrix metalloproteinase-13 (MMP-13) and inducible nitric oxide synthase (iNOS) in TMJ-OA cartilage in a dose-dependent manner. Rebamipide also suppressed the activation of transcription factors (e.g., NF-κB, NFATc1) and mitogen-activated protein kinases (MAPK) by receptor activator of nuclear factor kappa-B ligand (RANKL) to inhibit the differentiation of osteoclastic precursors, and disrupted the formation of actin rings in mature osteoclasts. Together, these results demonstrate the inhibitory effects of rebamipide on cartilage degradation in experimentally induced TMJ-OA. Furthermore, suppression of oxidative damage, restoration of extracellular matrix homeostasis of articular chondrocytes, and reduced subchondral bone loss as a result of blocked osteoclast activation suggest that rebamipide is a potential therapeutic strategy for TMJ-OA.

The association between temporomandibular disorders and joint hypermobility syndrome: a nationwide population-based study.

This study aims to investigate the risk factors of temporomandibular disorders (TMDs), including disc or non-disc-related disorders, and joint hypermobility syndrome (JHS) retrospectively and to analyze the factors by estimating the magnitude of the association between the two conditions using a nationwide population-based dataset. A total of 975,788 eligible patients' de-identified data were obtained from a representative database composed of one million of Taiwan's population since 2004 to 2008. All associated factors, such as gender, age, facial trauma, and psychosis, which correlated with TMDs and JHS were examined. Multiple logistic regression modeling adjusted for confounding variables to determine the odds ratio of variables that made an important contribution to TMDs and JHS. For all TMDs patients, only 1.47% patients had disc-related disorders. For all JHS patients, only 3.85% patients are diagnosed with concomitant TMDs. Statistically significant association was observed between joint hypermobility and TMDs. Furthermore, the prevalence of JHS patients shows significant difference within TMD subgroups, in which 9.52% of JHS patients have disc disorders and 90.48% of JHS patients do not. All associated factors, such as gender, age, JHS, facial trauma, and psychosis, had a significant impact on the TMDs. Interestingly, patients with TMJ articular disc disorders are 6.7 times more likely to be diagnosed with JHS compared to patients without disc-related disorders. Our results confirm that there is a significant positive association between TMDs and JHS, highlighting that patients with disc-related TMDs are more likely to experience JHS than patients with TMDs without disc disorders. Individuals with TMD associated with JHS should be carefully evaluated by inter-disciplinary specialists as these factors may eventually have impact on the prognosis of TMDs and JHS.

The reproducibility of temporomandibular joint vibrations over time in the human

The aim of the study was to assess the reproducibility of vibrations recorded from the temporomandibular joint (TMJ) in a group of healthy subjects. The vibrations from TMJ were recorded bilaterally from 34 healthy subjects by electrovibratography in three sessions at intervals of 3min and again after 1week. The total integral of the vibration energy, the ratio of the integral between frequencies above 300Hz and below 300Hz (ratio of >300Hz/<300Hz), peak frequency, median frequency, peak amplitude and distance to centric occlusion position were calculated. Data were analysed with intraclass correlation coefficients (ICC) and two-way anova for repeated measures. All variables showed good to excellent reliability across different sessions (ICCday1 : 0·935-0·987; ICCday2 : 0·910-0·992) and across different days (ICC: 0·738-0·907). According to anova for repeated measures, all variables showed good reproducibility (P>0·05) between sessions at the same day. There was no significant difference between the 2days for the frequency-related variables including peak frequency (P=0·083), median frequency (P=0·188) and ratio of >300Hz/<300Hz (P=0·26). There was a statistical difference between the 2days for the intensity-related vibration variables including total integral (P=0·045) and peak amplitude (P=0·026). The wave patterns of the power-frequency spectra were qualitatively similar over both the sessions and days. Joint vibration analysis could provide a fast, non-invasive, and repeatable method to record the status of TMJ. Further studies are needed to identify the characteristic waveforms for different subgroups of temporomandibular disorders and to evaluate the possibility of diagnostic value.

Multisystem Dysregulation in Painful Temporomandibular Disorders

Multiple physiological and psychological regulatory domains may contribute to the pathophysiology of pain in temporomandibular disorder (TMD) and other bodily pain conditions. The purpose of this study was to evaluate the relationship between multisystem dysregulation and the presence of TMD pain, as well as the presence of different numbers of comorbid pain conditions in TMD. Secondary data analysis was conducted in 131 non-TMD (without comorbid pain) controls, 14 TMD subjects without comorbid pain, 78 TMD subjects with 1 comorbid pain, and 67 TMD subjects with multiple comorbid pain conditions who participated in a TMD genetic study. Twenty markers from sensory, autonomic, inflammatory, and psychological domains were evaluated. The results revealed that 1) overall dysregulation in multiple system domains (OR [odds ratio] = 1.6, 95% confidence interval [CI] = 1.4–1.8), particularly in the sensory (OR = 1.9, 95% CI = 1.3–2.9) and the psychological (OR = 2.1, 95% CI = 2.1–2.7) domains, were associated with increased likelihood of being a painful TMD case; and 2) dysregulations in individual system domains were selectively associated with the increased odds of being a TMD case with different levels of comorbid persistent pain conditions. These outcomes indicate that heterogeneous multisystem dysregulations may exist in painful TMD subgroups, and multidimensional physiological and psychological assessments can provide important information regarding pathophysiology, diagnosis, and management of pain in TMD patients. PerspectiveThe concurrent assessment of multiple physiological and psychological systems is critical to our understanding of the pathophysiological processes that contribute to painful TMD and associated comorbid conditions, which will ultimately guide and inform appropriate treatment strategies that address the multisystem dysregulation associated with complex and common persistent pain conditions.

Assessment of thickness and function of masticatory and cervical muscles in adults with and without temporomandibular disorders

ObjectiveThe aim of this study was to evaluate the maximal bite force (MBF), electromyographic (EMG) activity and thickness of the masseter, anterior part of the temporalis and sternocleidomastoid (SCM) muscles in a group of young adults with and without temporomandibular disorders (TMDs). DesignNineteen individuals comprised the TMD group (6 males/13 females, aged 25.4±3.8 years), classified based on the Research Diagnostic Criteria for TMD (RDC/TMD), and 19 comprised the control group (6 males/13 females, aged 24.1±3.6 years). The MBF was determined with a transducer placed between the dental arches at the first molars level (N). The muscles were evaluated bilaterally at rest and during maximal voluntary clenching (MVC) by assessing EMG activity and performing ultrasonography (USG). The mean values of these measures for both sides of the mouth were used. The normality of the distributions was assessed by the Shapiro–Wilks test. Variables between groups and genders were compared using two-way factorial ANOVA test and correlated using the Spearman coefficient (α=0.05). Unpaired t test was used to compare variables between TMD subgroups. Logistic regression analysis was used to identify the variables associated with the presence of TMD. ResultsMBF, EMG and USG data were similar among clinical groups and among TMD subgroups. The thickness of masseter and SCM muscles in the relaxed and clenching states were significantly higher in males than females. On the other hand, the EMG of the temporalis muscle in the rest state was significantly higher in females than males. Additionally, the MBF was positively correlated with the USG characteristics of masseter and SCM muscles, as well as with the EMG activity of masseter and temporalis muscles in the TMD group. In this group, there was also a positive correlation between the thickness of the masseter muscle and its activity. On the other hand, the thickness of the SCM muscle was negatively correlated with its activity. A lower MBF was independently associated with the presence of TMD. ConclusionsSubjects with TMD exhibited similar values of MBF, thickness and electrical activity of masticatory and cervical muscles when compared with controls; positive correlations observed between these variables may suggest a muscular alteration in TMD patients and a co-activation of masticatory and cervical muscles during mandibular movement. This fact may also be confirmed by the negative association between bite forces and presence of TMD.