Occlusion and temporomandibular disorders (TMD): still unsolved question?

Remodeling dental anatomy vs sham therapy for chronic temporomandibular disorders. A placebo-controlled randomized clinical trial

BACKGROUND

Evidence regarding the etiology or effective treatments for chronic orofacial pain, the majority diagnosed as temporomandibular disorder (TMD), is limited.

PURPOSE

To investigate whether occlusal equilibration therapy (ET) and decreasing the (higher) angle of the lateral guidance on the nonworking-side leads to a reduction in chronic TMDs intensity.

METHODS

It was conducted a randomized, explanatory, single blind with blinded assessment, placebo-controlled trial with strong protection against bias involving patients with chronic TMDs. Participants were randomly assigned to receive equilibration therapy or sham therapy. ET in this study consisted of minimal invasive occlusal remodeling to obtain balanced occlusion with reduction of the steeper angle of lateral mandibular movement with respect to the Frankfort plane. The primary outcome was a change in the pain intensity score (on a 0-10 point scale, with 0 indicating no pain and 10 the worst possible pain) at month 6. Secondary outcomes include maximum unassisted mouth opening and psychological distress.

RESULTS

A total of 77 participants underwent randomization, 39 of whom received ET and 38 sham therapy. The trial was stopped early for efficacy, according to preestablished rules when 67 participants (n = 34, n = 33, respectively) had completed the analysis. At month 6, the mean unadjusted pain intensity score was 2.1 in the ET and 3.6 in the sham therapy group (adjusted mean difference, -1.54; 95% confidence interval [CI] -0.5 to -2.6; P = 0.004; ANCOVA model). The mean increase in maximum unassisted mouth opening (main secondary outcome) was significantly higher in the real therapy group (adjusted mean difference 3.1 mm, 95% CI 0.5-5.7, p = 0.02).

CONCLUSION

ET significantly reduced the intensity of facial pain associated with chronic TMDs and increased maximum unassisted mouth opening, as compared with sham therapy, over the course of 6 months. There were no serious adverse events. Funded by the Instituto de Salud Carlos III from the Ministry of Science and Innovation of the Government of Spain and European Regional Development Fund, Grant nº PI11/02507; "una manera de hacer Europa".

Spontaneous brain activity and connectivity in female patients with temporomandibular joint synovitis pain: a pilot functional magnetic resonance imaging study

OBJECTIVE

It has been proposed that mechanisms in the central nervous system contribute to the development and maintenance of pain in temporomandibular disorders. In this study, we tested whether spontaneous brain activity and functional connectivity (FC) were altered in patients with temporomandibular joint synovitis pain.

STUDY DESIGN

A prospective, cross-sectional design was adopted. Each of 8 patients and 10 healthy controls (HCs) underwent 2 sessions of functional magnetic resonance imaging: mouth closed and mouth open (painful for patients). Regional homogeneity (ReHo) was used to measure spontaneous brain activity in each participant. Brain areas with altered ReHo in patients compared with HCs were identified, and their FCs with the rest of the brain was examined and compared.

RESULTS

Compared with HCs, patients showed decreased pain-related ReHo in the right anterior insula (rAI). The rAI showed a weaker positive FC with the left middle cingulate cortex (MCC) and a weaker negative FC with the right precuneus in patients compared with HCs. Furthermore, the rAI-MCC FC showed a negative correlation with pain intensity in patients.

CONCLUSIONS

These results provide evidence supporting altered pain-related spontaneous brain activity and functional connectivity in the central nervous system in patients with temporomandibular joint synovitis pain.

Role of the Wnt/β-catenin signaling pathway in the response of chondrocytes to mechanical loading

In order to better understand the mechanisms by which chondrocytes respond to mechanical stimulation, ATDC5 mouse embryonic carcinoma cells were induced to differentiate into chondrocytes and then exposed to mechanical loading. To specifically elucidate the role of this pathway, the localization and expression of proteins involved in the Wnt/β-catenin signaling pathway were observed. Chondrogenic-differentiated ATDC5 cells were exposed to a 12% cycle tension load for 1, 2, 4, or 8 h. At each time point, immunofluorescence staining, western blot analysis, and qPCR were used to track the localization of β-catenin and glycogen synthase kinase-3β (GSK-3β) expression. In addition, the mRNA expression of Wnt3a, disheveled homolog 1 (Dvl-1), GSK-3β, and collagen type II were also detected. Activation of the Wnt/β-catenin signaling pathway was investigated in cells treated with Dickkopf-related protein 1 (DKK-1). β-catenin and GSK-3β protein expression increased initially and then decreased over the mechanical loading period, and the corresponding mRNA levels followed a similar trend. After application of the inhibitor DKK-1, Wnt/β‑catenin signaling was suppressed, and the mRNA expression of collagen II was also reduced. Thus, stimulation of chondrocytes with mechanical strain loading is associated with the translocation of active β-catenin from the cytoplasm to the nucleus.

Orthodontics is temporomandibular disorder-neutral

OBJECTIVES

To assess if subjects with a clinical diagnosis of temporomandibular disorders (TMDs) have a similar prevalence of orthodontic history as a population of TMD-free individuals and to assess if those subjects who have a history of ideal orthodontics have fewer symptoms than those with a history of nonideal orthodontics.

MATERIALS AND METHODS

Two groups of age- and sex-matched individuals belonging to either a study ("TMD") or a control group were recruited. Subjects who underwent orthodontic treatment were classified as having a history of ideal or nonideal orthodontics based on the current presence of normal values in five reference occlusal features.

RESULTS

The correlation with a history of orthodontic treatment was not clinically significant for any of the TMD diagnoses (ie, muscle pain, joint pain, disc displacement, arthrosis), with Phi (Φ) coefficient values within the -0.120 to 0.058 range. Within the subset of patients with a history of orthodontics, the correlation of ideal or nonideal orthodontic treatment with TMD diagnoses was, in general, not clinically relevant or was weakly relevant.

CONCLUSIONS

Findings confirmed the substantial absence of clinically significant effects of orthodontics as far as TMD is concerned. The very low correlation values of a negative or positive history of ideal or nonideal orthodontics with the different TMD diagnoses suggest that orthodontic treatment could not have a true role for TMD.

Dental malocclusion is not related to temporomandibular joint clicking: a logistic regression analysis in a patient population

OBJECTIVES

To assess the association of several dental malocclusion features with temporomandibular joint (TMJ) click sounds in a population of temporomandibular disorder (TMD) patients.

MATERIALS AND METHODS

Four hundred forty-two TMD patients (72% female; 32.2 ± 5.7 years, range 25-44 years) were divided into a TMJ clicking and a no-TMJ clicking group, based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) assessment. Seven occlusal features were recorded for each patient: (1) posterior crossbite, (2) overbite, (3) open bite, (4) overjet, (5) mediotrusive and (6) laterotrusive interferences and (7) retruded contact position to maximum intercuspation (RCP-MI) slide length. A logistic regression model was created to estimate the association of occlusal features with TMJ clicking.

RESULTS

The difference between the groups as for the prevalence of the various occlusal features was generally not statistically significant, with minor exceptions. Mediotrusive interferences (P  =  .015) and RCP-MI slide ≥2 mm (P  =  .001) were the two occlusal features that were associated with the probability of having TMJ clicking, even if the adjusted odds ratios for TMJ clicking were low for both variables (1.63 and 1.89, respectively). Moreover, the amount of variance in the prevalence of TMJ clicking that was predicted by the final model was as low as 4.5% (R(2)  =  0.045).

CONCLUSIONS

Findings from the present investigation suggested that in a population of TMD patients, the contribution of dental malocclusion features to predict TMJ click sounds is minimal with no clinical relevance.

Psychosocial behaviour and health care utilization in patients suffering from temporomandibular disorders diagnosed on the basis of clinical findings and MRI examination

The aim of this study was to evaluate psychosocial behaviour and differences in health care utilization between subgroups of patients suffering from temporomandibular disorders, using both clinical examination and magnetic resonance imaging (MRI).

MATERIALS AND METHODS

70 patients were examined according to the research diagnostic criteria for temporomandibular disorders (RDC/TMD), and were divided into groups according to their clinical diagnoses. MRIs were acquired and joint-related RDC/TMD diagnoses were modified on the basis of MRI findings. Group I suffered from joint pathology, group II from myofascial pain and group III from a combination. Non-parametric statistics were used to reveal group-related differences in psychosocial and behavioural aspects. Differences in group assignment based on clinical and MRI examination were assessed (kappa statistics).

RESULTS

MRI findings led to group assignments that were different from clinical assignments (k = 0.3). For both types of assignment, patients with myofascial pain displayed higher somatization scores, used more splints and consulted more physicians. For clinical assignment only, depression scores were higher in the myofascial pain group. For MRI based assignment, sex differences were significant between groups I and III.

CONCLUSION

Somatization-specific behaviour is more widespread in patients suffering from exclusively myofascial pain than in patients presenting joint pathology. Inconsistencies in differences of other psychosocial variables between groups of TMD patients seem to be related to differences in group assignment either with or without objective information on joint pathology.

Chronic myofascial temporomandibular pain is associated with neural abnormalities in the trigeminal and limbic systems

Myofascial pain of the temporomandibular region (M-TMD) is a common, but poorly understood chronic disorder. It is unknown whether the condition is a peripheral problem, or a disorder of the central nervous system (CNS). To investigate possible CNS substrates of M-TMD, we compared the brain morphology of 15 women with M-TMD to that of 15 age- and gender-matched healthy controls. High-resolution structural brain and brainstem scans were carried out using magnetic resonance imaging (MRI), and data were analyzed using a voxel-based morphometry approach. The M-TMD group evidenced decreased or increased gray matter volume compared to controls in several areas of the trigeminothalamocortical pathway, including brainstem trigeminal sensory nuclei, the thalamus, and the primary somatosensory cortex. In addition, M-TMD individuals showed increased gray matter volume compared to controls in limbic regions such as the posterior putamen, globus pallidus, and anterior insula. Within the M-TMD group, jaw pain, pain tolerance, and pain duration were differentially associated with brain and brainstem gray matter volume. Self-reported pain severity was associated with increased gray matter in the rostral anterior cingulate cortex and posterior cingulate. Sensitivity to pressure algometry was associated with decreased gray matter in the pons, corresponding to the trigeminal sensory nuclei. Longer pain duration was associated with greater gray matter in the posterior cingulate, hippocampus, midbrain, and cerebellum. The pattern of gray matter abnormality found in M-TMD individuals suggests the involvement of trigeminal and limbic system dysregulation, as well as potential somatotopic reorganization in the putamen, thalamus, and somatosensory cortex.

Missing posterior teeth and risk of temporomandibular disorders

There is disagreement about the association between missing posterior teeth and the presence of temporomandibular disorders (TMD). Here, the purpose was to investigate whether the number of missing posterior teeth, their distribution, age, and gender are associated with TMD. Seven hundred and forty-one individuals, aged 21-60 years, with missing posterior teeth, 386 with and 355 without TMD, were included. Four variables-gender, age, the number of missing posterior teeth, and the number of dental quadrants with missing posterior teeth-were analyzed with a logistic regression model. All four variables-gender (OR = 1.59, men = 1, women = 2), age (OR = 0.98), the number of missing posterior teeth (OR = 0.51), and the number of dental quadrants with missing posterior teeth (OR = 7.71)-were entered into the logistic model (P < 0.01). The results indicate that individuals who lose posterior teeth, with fewer missing posterior teeth but in more quadrants, have a higher prevalence of TMD, especially young women.

Signs and symptoms related to temporomandibular disorders—Follow-up of subjects with shortened and complete dental arches

OBJECTIVE

To assess prevalence of cardinal signs and symptoms related to temporomandibular disorders (TMD) in subjects with shortened dental arches and to clarify the individual course of these signs and symptoms.

METHODS

In this 9-year follow-up study, subjects with shortened dental arches (n=74) were compared with subjects with complete dental arches (n=72). Of three reported symptoms (pain, noises/clicking and restricted mobility of the lower jaw), and of two clinical signs (palpated clicking of the temporomandibular joint and restricted maximal mouth opening) estimates of mean scores were calculated by a mixed model. Suggested determinants for TMD (gender, time, bruxism, chewing side preference) were investigated by covariate analyses. Subjects with complete 9-year follow-up (shortened dental arches: n=42; complete dental arches: n=41) were described more detailed by frequency distributions, Pearson correlations of signs and symptoms, and fluctuation of the symptoms.

RESULTS

Covariate analyses using the mixed model revealed no significant differences between the shortened and the complete dental arch groups (p>0.05) with respect to symptoms and signs. Most prevailing effect was gender: females reported more frequently pain (p=0.05) and noises/clicking (p=0.03). Restricted mobility was significantly related with chewing side preference and bruxism habits (both: p=0.01). In both groups, subjects with complete 9-year follow-up had low prevalence of serious symptoms and signs and symptoms fluctuated without demonstrable correlation.

CONCLUSION

In this 9-year follow-up, subjects with shortened dental arches had similar prevalence, severity, and fluctuation of signs and symptoms related to TMD compared to subjects with complete dental arches.

The prevalence of myofascial pain and its association with occlusal factors in a threshold country non-patient population

The objective of the study is to assess the prevalence of myofascial pain in a threshold country and to isolate occlusal risk factors. One hundred and seventy-one randomized selected women were examined by a trained examiner in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) examination procedure. Subscales of the SCL 90-R, graded chronic pain status, and anamnestic questionnaires were also used. Logistic regression was performed to compute the odds ratios for six common occlusal features with regard to the presence of myofascial pain, in accordance with the RDC/TMD criteria. Fifteen subjects (15 / 151 = 9.93%) suffered from myofascial pain. Results from logistic regression analysis showed that non-occlusion (posterior teeth, at least one side) and open bite increased the risk of myofascial pain. The prevalence of myofascial pain in this study is comparable with that in another study, in a highly industrialized environment, in which the RDC/TMD was used. The role of occlusion in a non-patient population seems to be restricted to serious alterations of normality. This article presents the prevalence of myofascial pain and its association with occlusal factors. This issue will help the clinicians to assess the influence of occlusion in myofascial pain patients and to send the patient to the appropriate specialist.

Psychological factors and responses to artificial interferences in subjects with and without a history of temporomandibular disorders

OBJECTIVE

It has often been suggested that psychological factors play a role in temporomandibular disorders (TMD). However, reports on psychological factors in TMD patients and controls have been equivocal. In a previous double-blind randomized controlled study, subjects with a TMD history showed more clinical signs and subjective symptoms and adapted less well to the artificial interferences than subjects without an earlier TMD history. In the present study, we analyzed the associations of psychological factors with symptom responses and adaptation to interferences.

MATERIAL AND METHODS

Before the intervention, the subjects filled in questionnaires dealing with personality traits, level of psychological and somatic stress symptoms, coping strategies, and health beliefs. Every day during the 2-week follow-up period, the subjects rated the intensity of their symptoms on 9 modified visual analog scales (VAS).

RESULTS

Health hardiness, positive socialization history and inhibition of aggression were associated with weaker symptom responses and better adaptation to true artificial interferences. Some personality characteristics in subjects with an earlier TMD history tended to associate with higher symptom reporting despite the type of intervention.

CONCLUSIONS

Psychological factors appeared significant for the symptom responses to artificial interferences, and they seem to play a different role in responses in subjects with an earlier TMD history compared to those without.

Correction of the maxillary occlusal plane relieves persistent headache and shoulder stiffness

It has been known for many years that deformations of the occlusal plane of the teeth cause indefinite symptoms such as headaches or stiffness of the shoulders. However, how the occlusal plane of the teeth should be corrected remains uncertain. The purpose of this study was to examine whether a correction of the deviation of the maxillary occlusal plane (MOP) from the center of dens of axis vertebrae (DAV) improves symptoms in patients having intractable headache or shoulder-stiffness. Forty patients who complained of dental abnormalities and persistent headache or shoulder-stiffness that had not responded to conventional medical treatment and 17 healthy controls were recruited. All subjects received a lateral cephalometric x-ray examination to measure a distance from the MOP and the center of DAV. In the healthy subjects, both the upper and the lower shift of the MOP from the center of DAV were minimal (the upper shift was 1 +/- 2 [mean +/- S.D.] mm and the lower shift was 4 +/- 4 mm). By contrast, the patients had a significantly greater deviation of the MOP from the center of DAV. Dental adjustment treatment was performed in fourteen patients who had a substantial deviation of the MOP from the center of DAV. Those patients were asked about their symptoms which were scored using a point system and were compared before and after treatment. An adjustment procedure of the MOP passing through the DAV significantly relieved clinical symptoms in these patients (before 42.5 +/- 34.4 vs after 7.0 +/- 8.2, p < 0.01). Correction of the MOP passing through the near center of DAV might be effective in relieving clinical symptoms associated with dental deformities.

Quantification of the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system

STATEMENT OF PROBLEM

There is no consensus on the association between occlusion and temporomandibular disorders (TMD).

PURPOSE

The purpose of this study was to quantify the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system.

MATERIAL AND METHODS

Eight occlusal features: retruded contact position (RCP) to maximum intercuspation (MI) slide length, vertical overlap, horizontal overlap, unilateral posterior reverse articulation, anterior open occlusal relationship, incisor dental midline discrepancy, mediotrusive interferences, and laterotrusive interferences, were clinically assessed by the same trained operator. The sample consisted of 81 women with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis I diagnosis of muscle disorder, for example myofascial pain, with or without limited opening, and 48 healthy women (control group). A stepwise multiple logistic regression was used to identify the significant associations between occlusal features and disease.

RESULTS

A slide from the retruded contact position to maximum intercuspation > or =2 mm and mediotrusive interferences were the only 2 occlusal features significantly associated with the presence of myofascial pain according to the RDC/TMD criterion symptoms. The odds ratio for myofascial pain was 2.57 for a slide from RCP to MI > or =2 mm and 2.45 for mediotrusive interferences. The percentage of the total log likelihood for myofascial pain explained by the significant occlusal factors amounted to 10.8% (Nagelkerke's R2=0.108). The multifactorial model, including the 2 significant occlusal factors, showed an acuracy to predict disease of 66.7% (sensitivity 71.6%; specificity 58.3%).

CONCLUSION

Occlusal features showed a low predictive value to detect muscle disorders of the stomatognathic system. Multifactorial complex pathologies, such as TMD, should be studied using multivariate statistical analyses, as univariate models may overestimate some resulting associations.