Successful therapy for temporomandibular pain alters anterior insula and cerebellar representations of occlusion

Pain and salivary biomarkers of stress in temperomandibular disorders were affected by maxillary splints

BACKGROUND

Longitudinal intervention studies on treatment options in temporomandibular dysfunction (TMD) including self reports and salivary biomarkers of stress are rare and the exact therapeutic function of occlusal splints widely unknown.

METHODS

We examined the therapeutic effects of a Michigan splint with occlusal relevance in patients with TMD using a placebo-controlled, delayed-start design. Two intervention groups received a Michigan splint, while one of them had a placebo palatine splint for the first 3 weeks. We collected pain intensities (at rest and after five occlusal movements), salivary measures associated with stress (cortisol and alpha-amylase) and self-reported psychological distress (stress, anxiety, catastrophizing) at baseline and 3 and 7 weeks after onset of intervention.

RESULTS

At baseline, we observed increased pain intensity and psychological distress in TMD patients compared to 11 matched healthy controls. Baseline anxiety was linked to movement pain intensity through stress. Over therapy reductions in pain intensity and morning cortisol were more pronounced in those patients starting immediately with the Michigan splint, while psychological distress decreased similarly in both groups.

CONCLUSION

Our results suggest that perceived stress plays a role for the association between anxiety and TMD pain and underlines the need for an interdisciplinary perspective on the pathogenesis and therapy of TMD in a setting where psychotherapeutic knowledge is still scarce or rarely applied.

Anxiety mediates association between sex and jaw function limitation in temporomandibular disorder patients from China

Aim

The objective of this study is to explore the relationship between sex and jaw function and to test whether anxiety mediates the causal relationship between sex and jaw function in temporomandibular disorders (TMDs) patients.

Methods

A total of 488 participants with TMD were included in the analysis. Demographic data were collected. Generalized anxiety symptoms and anxiety severity were initially assessed using the GAD-7 questionnaire. And jaw function limitation was measured using the JFLS-8 scale. A directed acyclic graph (DAG) was used in this study to evaluate the hypotheses. Mediation analysis was conducted to explore causality and to calculate the total effect, natural direct effect (NDE) and natural indirect effect (NIE).

Results

In TMD patients, there was a significant association between female and jaw function (r = 0.17, p < 0.001), female and anxiety (r = 0.15, p = 0.002), anxiety and jaw function (r = 0.35, p < 0.001). In addition, sex can directly lead to differences in impaired jaw function (NDE: 3.719, 95% CI: 1.619-5.828, p < 0.001), and can also be causally related to jaw function through anxiety (NIE: 1.146, 95% CI: 0.267-2.024, p = 0.011). And the total effect was 4.865 (95% CI, 2.709-7.029, p < 0.001).

Conclusion

A causal mechanism was found that anxiety acts as a mediator of sex effects on jaw function. Therefore, psychological factors need to be taken into account in the treatment of female TMD patients. Further clinical trials are needed to explore whether psychotherapy is more beneficial to improve jaw function in female TMD patients.

Thermo-flexible resin for the 3D printing of occlusal splints: a randomized pilot trial

OBJECTIVES

To compare the clinical performance of occlusal splints printed from thermo-flexible resin with milled splints.

METHODS

A parallel two-arm pilot trial was initiated. Forty-seven patients (n women=38) were recruited from a tertiary care center and randomized using an online tool (sealed envelope). Inclusion criterion was an indication for treatment with a centric relation occlusal splint due to bruxism or any form of painful temporomandibular disorder. Patients were excluded if they were younger than 18 years, unable to attend follow-up appointments, or required another type of splint therapy. Patients received either, a 3D-printed (intervention group, V-print splint comfort, VOCO) or a milled splint (control group, ProArt CAD splint, Ivoclar). Construction software Ceramill M-splint (AmannGirrbach), 3D-printer MAX UV 385 (Asiga) and milling unit PrograMill PM7 (Ivoclar) were used. Follow-up assessments were conducted after 2 weeks and 3 months. Outcome measures were survival, adherence, technical complications, patient satisfaction on a 10-point Likert scale, and maximum wear using superimposition of optical scans.

RESULTS

After 3 months, 20/23 intervention group and 18/24 control group participants were assessed. All splints survived. Minor complications were small crack formations on 6 printed and 4 milled splints. Mean patient satisfaction was 8 (SD 1.7) for printed, and 8.1 (SD 2.3) for milled splints (r= .1, p=.52). Median maximum wear was highly dispersed with 153 (IQR 140) in posterior and 195 (IQR 537) in frontal segments of printed, and 96 (IQR 78) respectively 123 (IQR 155) of milled splints, (both: r= .31, p=.084).

CONCLUSIONS

Within the limitations of a pilot trial, 3D-printed and milled splints performed similarly in terms of patient satisfaction, complication rates and wear behavior.

CLINICAL SIGNIFICANCE

Thermo-flexible material was proposed for 3D printing of occlusal splints to overcome mechanical weaknesses of previously available resins. This randomized pilot study provides evidence that this material is a viable alternative to milled splints for at least three months of clinical use. Further evidence on long-term use should be obtained.

Oral splint therapy in patients with Menière's disease and temporomandibular disorder: a long-term, controlled study

PURPOSE

To assess the effect of oral splint therapy on audio-vestibular symptoms in patients with Menière's disease (MD) and temporomandibular disorder (TMD).

METHODS

Retrospective case-control study. Treatment group: 37 patients with MD and TMD who received gnatological treatment.

CONTROL GROUP

26 patients with MD and TMD who had never received gnatological treatment. The number of vertigo spells in 6 months (primary endpoint), pure-tone audiometry average (PTA), MD stage, functional level, Dizziness handicap Index (DHI), Tinnitus handicap Index (THI) and Aural Fullness Scale (AFS) were compared at baseline and after 24 months according to groups. Analysis of Covariance was used to determine the treatment effect.

RESULTS

Groups were comparable for demographic, clinical data, baseline PTAs and the number of vertigo spells. Analysis of covariance showed a significant effect of gnathological treatment on number of vertigo spells ([Formula: see text] = 0.258, p < 0.001), PTA ([Formula: see text] = 0.201, p < 0.001), MD stage ([Formula: see text] = 0.224, p < 0.001), functional level ([Formula: see text] = 0.424, p < 0.001), DHI ([Formula: see text] = 0.421, p < 0.001), THI ([Formula: see text] = 0.183, p < 0.001), but not for AFS ([Formula: see text] = 0.005, p = 0.582). The treatment group showed vertigo control of class A in 86.5% and class B in 13.5% of patients. In the control group, vertigo control was of class A in 19.2% of patients and class B in 11.5%, class C in 30.8%, class D in 11.5%, class E in 19.2% and class F in 7.7%. Classes of vertigo control differed significantly (X² test, p < 0.001).

CONCLUSIONS

Oral splint therapy could represent a viable treatment in patients with TMD and uncontrolled MD disease. The effects are maintained at least after 2 years.

Relationship between dental occlusion and brain activity: A narrative review

Objectives

Occlusal function stimulates different areas of the cerebral cortex. The purpose of this narrative review was to identify the relationship between occlusion and brain activity so as to provide theoretical support to enable future studies on the subject.

Study selection, data, and sources

Relevant case-control studies, clinical trials, and systematic reviews available in English were retrieved from the following databases: MEDLINE, PubMed, ScienceDirect, Wiley Online Library, and Biblioteca Virtual en Salud (BVS). Of the 53 articles obtained, 12 were included.

Conclusion

The sensorimotor cortex is affected by changes in occlusion. It is speculated that occlusion could play an important role in the development of diseases, from anxiety and stress to Alzheimer’s disease and senile dementia. Further investigations into the interactions between occlusion and brain function are needed to elucidate the parts of the brain that are affected when occlusion is disturbed and to determine whether brain function is altered.

Clinical significance

Dentists must consider that alterations in the occlusal pattern during mastication can lead to changes in the activation of different brain regions related to memory, learning, anticipatory pain, and anxiety. This suggests that mastication maintains the integrity of certain brain areas and that it may be a key factor in the onset of neurodegenerative diseases.

Functional MRI in Radiology—A Personal Review

We, here, provide a personal review article on the development of a functional MRI in the radiology departments of two German university medicine units. Although the international community for human brain mapping has met since 1995, the researchers fascinated by human brain function are still young and innovative. However, the impact of functional magnetic resonance imaging (fMRI) on prognosis and treatment decisions is restricted, even though standardized methods have been developed. The tradeoff between the groundbreaking studies on brain function and the attempt to provide reliable biomarkers for clinical decisions is large. By describing some historical developments in the field of fMRI, from a personal view, the rise of this method in clinical neuroscience during the last 25 years might be understandable. We aim to provide some background for (a) the historical developments of fMRI, (b) the establishment of two research units for fMRI in the departments of radiology in Germany, and (c) a description of some contributions within the selected fields of systems neuroscience, clinical neurology, and behavioral psychology.

Clinical and Neurophysiological Effects of Progressive Movement Imagery Training for Pathological Pain

Movement limitation is a common characteristic of chronic pain such that pain prevents the very movement and activity that is most likely to promote recovery. This is particularly the case for pathological pain states such as complex regional pain syndrome (CRPS). One clinical approach to CRPS that has growing evidence of efficacy involves progressive movement imagery training. Graded Motor Imagery (GMI) targets clinical and neurophysiological effects through a stepwise progression through implicit and explicit movement imagery training, mirror therapy and then functional tasks. Here we review experiences from over 20 years of clinical and research experience with GMI. We situate GMI in terms of its historical underpinnings, the benefits and outstanding challenges of its implementation, its potential application beyond CRPS. We then review the neuropathological targets of GMI and current thought on its effects on neurophysiological biomarkers. Perspective This article provides an overview of our experiences with graded motor imagery training over the last 20 years focussing on the treatment of CRPS. It does both cover the theoretical underpinnings for this treatment approach, biomarkers which indicate potential changes driven by GMI, and experiences for achieving optimal treatment results.

Occlusal splint therapy in patients with Ménière's disease and temporomandibular joint disorder

Objective

This retrospective study aimed to verify the outcomes of stabilising occlusal splint therapy prescribed to 22 patients with unilateral definite Ménière’s disease and comorbid temporomandibular joint disorder.

Methods

The results of a battery of audiometric and vestibular tests were recorded before and after 6 months of treatment, as well as the scores of disease-specific questionnaires.

Results

The average hearing threshold in the affected ear and the acoustic immittance were unchanged. No spontaneous and positional nystagmus were recorded. Caloric hypo-responsiveness and vestibular myogenic evoked responses did not vary. No changes of stabilometric body sway parameters in eyes opened condition and with optokinetic stimulation delivered to the unaffected labyrinth were observed. A significant reduction was recorded in eyes closed condition and with the optokinetic stimulation toward the affected ear. The Tinnitus Handicap Inventory, the Situational Vertigo Questionnaire and the Numeric Pain Rating Scale scores improved. The number of vertigo attacks was reduced.

Conclusions

Occlusal splint therapy is a favourable option to reduce aural symptoms of Ménière’s disease and comorbid temporomandibular joint disorder, even if its pathophysiological mechanism remains elusive.

Nonsurgical treatment of class III malocclusion with temporomandibular disorder comorbidity: A clinical report

The treatment of a 57-year-old woman with combined skeletal and pseudo-class III malocclusion who was also suffering from chronic myofascial orofacial pain is described. The challenge was to treat the patient's malocclusion while simultaneously managing the temporomandibular disorder. After a successful 3-month occlusal device therapy, which substantially reduced the patient's discomfort, a nonsurgical therapy by using complete-mouth fixed restorations was planned. The treatment was first tested by using printed interim restorations before monolithic zirconia restorations were provided. Stable occlusion and a pain-free outcome were observed at the 3-month follow-up.

Pre-operative Limbic System Functional Connectivity Distinguishes Responders From Non-responders to Surgical Treatment for Trigeminal Neuralgia

Background: Trigeminal neuralgia (TN) is a severe facial pain condition often requiring surgical treatment. Unfortunately, even technically successful surgery fails to achieve durable pain relief in many patients. The purpose of this study was to use resting-state functional magnetic resonance imaging (fMRI) to: (1) compare functional connectivity between limbic and accessory sensory networks in TN patients vs. healthy controls; and (2) determine if pre-operative variability in these networks can distinguish responders and non-responders to surgery for TN. Methods: We prospectively recruited 22 medically refractory classic or idiopathic TN patients undergoing surgical treatment over a 3-year period, and 19 age- and sex-matched healthy control subjects. fMRI was acquired within the month prior to surgery for all TN patients and at any time during the study period for controls. Functional connectivity analysis was restricted to six pain-relevant brain regions selected a priori: anterior cingulate cortex (ACC), posterior cingulate cortex, hippocampus, amygdala, thalamus, and insula. Two comparisons were performed: (1) TN vs. controls; and (2) responders vs. non-responders to surgical treatment for TN. Functional connectivity was assessed with a two-sample t-test, using a statistical significance threshold of p < 0.050 with false discovery rate (FDR) correction for multiple comparisons. Results: Pre-operative functional connectivity was increased in TN patients compared to controls between the right insular cortex and both the left thalamus [t ₍₃₉₎ = 3.67, p = 0.0007] and right thalamus [t ₍₃₉₎ = 3.22, p = 0.0026]. TN patients who were non-responders to surgery displayed increased functional connectivity between limbic structures, including between the left and right hippocampus [t ₍₁₈₎ = 2.85, p = 0.0106], and decreased functional connectivity between the ACC and both the left amygdala [t ₍₁₈₎ = 2.94, p = 0.0087] and right hippocampus [t ₍₁₈₎ = 3.20, p = 0.0049]. Across all TN patients, duration of illness was negatively correlated with connectivity between the ACC and left amygdala (r ² = 0.34, p = 0.00437) as well as the ACC and right hippocampus (r ² = 0.21, p = 0.0318). Conclusions: TN patients show significant functional connectivity abnormalities in sensory-salience regions. However, variations in the strength of functional connectivity in limbic networks may explain why some TN patients fail to respond adequately to surgery.

Complex Regional Pain Syndrome: Thalamic GMV Atrophy and Associations of Lower GMV With Clinical and Sensorimotor Performance Data

Results on gray matter alterations in complex regional pain syndrome (CRPS) showed heterogeneous findings. Since CRPS is a rare disease, most studies included only small and heterogeneous samples resulting in a low reliability of findings between studies. We investigated 24 CRPS patients with right upper limb affection in the chronic stage of disease using structural MRI and clinical testing. We focused on gray matter volume (GMV) alterations of the brain in comparison to 33 age matched healthy controls, their association to clinical characteristics (duration of pain syndrome and pain intensity ratings) and sensorimotor performance (finger dexterity and spatiotactile resolution). When applying an explorative whole brain analysis CRPS patients showed lower GMV in the bilateral medial thalamus. No other areas showed a relevant GMV difference for the group comparisons. When applying a region of interest driven approach using anatomical masks of the thalamus, ACC/mPFC, putamen, and insula we found relevant associations of clinical and behavioral data in ACC and insula. Whereas, the GMV in ACC showed negative associations with pain intensity and CRPS duration, the GMV of the left posterior insula was negatively associated with sensorimotor performance of the affected hand side. Overall, our results are in accordance to results of others describing a thalamic reduction of GMV in patients with neuropathic pain and are also in accordance with associations of pain intensity and duration with reduced ACC in general in patients with chronic pain syndromes. Sensorimotor performance seems to be related to posterior insula GMV reduction, which has not been described yet for other patient groups.

Gray Matter Brain Alterations in Temporomandibular Disorder Tested in a Population Cohort and Three Clinical Samples

Temporomandibular pain (TMD) is a frequent symptom comprising pain around the mandibular jaw with a high dependence on stressors. Chronic pain has been associated with changes of the brains gray matter volume (GMV), but previous studies on GMV alterations associated with TMD have yielded contradictory results. This might be caused by divergent samples and study methods. We here tested GMV alterations using voxel based morphometry in three clinical samples (summing up to 47 TMD patients) and a population sample with 57 participants who indicated facial pain for the last 6 months. The GMV of pain patients was compared against age-matched and gender-matched participants without chronic pain (60 for the clinical sample comparison and 381 for the cohort sample comparison) who underwent the same assessments as the patient group (MRI measurements and data evaluation using CAT12). In a region of interest analysis, only the clinical samples showed an effect of decreased GMV in the anterior medial cingulate cortex reaching into the medial prefrontal cortex, known to be especially vulnerable for chronic pain gray matter volume reduction. The analysis of the population-based sample did not reveal relevant GMV differences. Overall, an important question remains as to whether most inconsistent results from voxel based morphometry-studies in chronic pain are related to chance results facilitated by small sample size and selection of patient samples. PERSPECTIVE: Using voxel based morphometry 2 samples with chronic temperomandibular pain were compared to controls investigating the brains GMV. Only the clinical sample showed a decrease in anterior cingulate GMV. Contradicting results on GMV loss in temperomandibular pain might be based on small samples in prior studies.

Altered functional connectivity of the insula in a rat model of recurrent headache

Migraine is a pain disorder accompanied by various symptoms. The insula, a “cortical hub,” is involved in many functions. Few studies have focused on the insula in migraine. We explored the resting-state functional connectivity between the insula and other brain areas in rats subjected to repeated meningeal nociception which was commonly used as animal model of migraine. Inflammatory soup was infused through supradural catheters in conscious rats. The rats were subdivided based on the frequency of the inflammatory soup infusions. Magnetic resonance imaging data were acquired on rats 21 days after inflammatory soup infusion and functional connectivity seeded on the insula was analyzed. In the low-frequency inflammatory soup group, magnetic resonance imaging was performed again 1 h after the glyceryl trinitrate injection following baseline scanning. The cerebellum showed increased functional connectivity with the insula in the inflammatory soup groups. The insula showed increased functional connectivity with the medulla and thalamus in the ictal period in the low-frequency inflammatory soup rats. In the high-frequency inflammatory soup group, several areas showed increased functional connectivity with the insula, including the pons, midbrain, thalamus, temporal association cortex, and retrosplenial, visual, and sensory cortices. Our findings support the hypothesis that the headache phase of migraine depends on the activation and sensitization of the trigeminovascular system, and that the chronification of migraine may be related to higher brain centers and limbic cortices. The insula may be a new target for treatment of migraine.

The neuro-pathophysiology of temporomandibular disorders-related pain: a systematic review of structural and functional MRI studies

Chronic pain surrounding the temporomandibular joints and masticatory muscles is often the primary chief complaint of patients with temporomandibular disorders (TMD) seeking treatment. Yet, the neuro-pathophysiological basis underlying it remains to be clarified. Neuroimaging techniques have provided a deeper understanding of what happens to brain structure and function in TMD patients with chronic pain. Therefore, we performed a systematic review of magnetic resonance imaging (MRI) studies investigating structural and functional brain alterations in TMD patients to further unravel the neurobiological underpinnings of TMD-related pain. Online databases (PubMed, EMBASE, and Web of Science) were searched up to August 3, 2019, as complemented by a hand search in reference lists. A total of 622 papers were initially identified after duplicates removed and 25 studies met inclusion criteria for this review. Notably, the variations of MRI techniques used and study design among included studies preclude a meta-analysis and we discussed the findings qualitatively according to the specific neural system or network the brain regions were involved in. Brain changes were found in pathways responsible for abnormal pain perception, including the classic trigemino-thalamo-cortical system and the lateral and medial pain systems. Dysfunction and maladaptive changes were also identified in the default mode network, the top-down antinociceptive periaqueductal gray-raphe magnus pathway, as well as the motor system. TMD patients displayed altered brain activations in response to both innocuous and painful stimuli compared with healthy controls. Additionally, evidence indicates that splint therapy can alleviate TMD-related symptoms by inducing functional brain changes. In summary, MRI research provides important novel insights into the altered neural manifestations underlying chronic pain in TMD.

Oral splints for patients with temporomandibular disorders or bruxism: a systematic review and economic evaluation

BACKGROUND

Splints are a non-invasive, reversible management option for temporomandibular disorders or bruxism. The clinical effectiveness and cost-effectiveness of splints remain uncertain.

OBJECTIVES

The objectives were to evaluate the clinical effectiveness and cost-effectiveness of splints for patients with temporomandibular disorders or bruxism. This evidence synthesis compared (1) all types of splint versus no/minimal treatment/control splints and (2) prefabricated versus custom-made splints, for the primary outcomes, which were pain (temporomandibular disorders) and tooth wear (bruxism).

REVIEW METHODS

Four databases, including MEDLINE and EMBASE, were searched from inception until 1 October 2018 for randomised clinical trials. The searches were conducted on 1 October 2018. Cochrane review methods (including risk of bias) were used for the systematic review. Standardised mean differences were pooled for the primary outcome of pain, using random-effects models in temporomandibular disorder patients. A Markov cohort, state-transition model, populated using current pain and Characteristic Pain Intensity data, was used to estimate the incremental cost-effectiveness ratio for splints compared with no splint, from an NHS perspective over a lifetime horizon. A value-of-information analysis identified future research priorities.

RESULTS

Fifty-two trials were included in the systematic review. The evidence identified was of very low quality with unclear reporting by temporomandibular disorder subtype. When all subtypes were pooled into one global temporomandibular disorder group, there was no evidence that splints reduced pain [standardised mean difference (at up to 3 months) -0.18, 95% confidence interval -0.42 to 0.06; substantial heterogeneity] when compared with no splints or a minimal intervention. There was no evidence that other outcomes, including temporomandibular joint noises, decreased mouth-opening, and quality of life, improved when using splints. Adverse events were generally not reported, but seemed infrequent when reported. The most plausible base-case incremental cost-effectiveness ratio was uncertain and driven by the lack of clinical effectiveness evidence. The cost-effectiveness acceptability curve showed splints becoming more cost-effective at a willingness-to-pay threshold of ≈£6000, but the probability never exceeded 60% at higher levels of willingness to pay. Results were sensitive to longer-term extrapolation assumptions. A value-of-information analysis indicated that further research is required. There were no studies measuring tooth wear in patients with bruxism. One small study looked at pain and found a reduction in the splint group [mean difference (0-10 scale) -2.01, 95% CI -1.40 to -2.62; very low-quality evidence]. As there was no evidence of a difference between splints and no splints, the second objective became irrelevant.

LIMITATIONS

There was a large variation in the diagnostic criteria, splint types and outcome measures used and reported. Sensitivity analyses based on these limitations did not indicate a reduction in pain.

CONCLUSIONS

The very low-quality evidence identified did not demonstrate that splints reduced pain in temporomandibular disorders as a group of conditions. There is insufficient evidence to determine whether or not splints reduce tooth wear in patients with bruxism. There remains substantial uncertainty surrounding the most plausible incremental cost-effectiveness ratio.

FUTURE WORK

There is a need for well-conducted trials to determine the clinical effectiveness and cost-effectiveness of splints in patients with carefully diagnosed and subtyped temporomandibular disorders, and patients with bruxism, using agreed measures of pain and tooth wear.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42017068512.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 7. See the NIHR Journals Library website for further project information.

Comparison of Cerebral Blood Flow Patterns in Patients with Phantom Bite Syndrome with Their Corresponding Clinical Features

BACKGROUND

Phantom bite syndrome (PBS) is characterized by an uncomfortable sensation during occlusion without any evident abnormality. A recent case-control study with single-photon emission computed tomography (SPECT) using ^99mTc-ethyl cysteinate dimer could not find the specific features of regional cerebral blood flow (rCBF), which might be due to the heterogeneity of PBS. We analyzed the brain images of PBS corresponding to the clinical features by studying PBS subgroups.

METHODS

This study contributes to elucidating the pathophysiology of PBS by evaluating regional brain perfusion on SPECT and its clinical features. We performed SPECT using ^99mTc-ethyl cysteinate dimer in 44 patients with PBS. The SPECT images were analyzed qualitatively and quantitatively.

RESULTS

Asymmetrical rCBF patterns were detected, corresponding to symptom laterality. Patients with PBS with right-side symptoms showed right-side-predominant rCBF asymmetry in the parietal region and left-side-predominant rCBF asymmetry in the thalamus, and vice versa. Moreover, the analysis of the association between rCBF and patient behaviors revealed that patients who blamed their dentists for their symptoms tended to have a symmetrical rCBF pattern.

CONCLUSION

Patients with PBS showed blood flow imbalance in the thalamus and parietal region corresponding to symptom laterality. There are two types of symmetrical and asymmetrical rCBF patterns in the pathophysiology of PBS despite similar clinical manifestations.

Association of decrease in insula fMRI activation with changes in trait anxiety in patients with craniomandibular disorder (CMD)

Patients with chronic pain and especially with craniomandibular disorder (CMD) show specific psychopathology in trait anxiety. In a previous longitudinal functional imaging study on CMD we found that the anterior insula was modulated by successful therapy intervention and pain relief. We here intended to investigate possible associations between anterior insula fMRI-activation during occlusal movements and trait anxiety over a splint therapy approach in patients with CMD. Three fMRI-investigations of a craniomandibular occlusion task were performed together with pain score evaluations and scoring of trait anxiety (State -Trait Anxiety Inventory; STAI) before, after two weeks and after three months of a DIR-mandibular splint therapy in a small group (n = 9) of CMD patients. Patients showed increased anxiety levels before therapy assessed with the STAI and the depression and anxiety scale (DASS). Besides of relevant reduction in pain the STAI decreased over time. Reduction in STAI was associated with anterior insular fMRI-activation reduction on both hemispheres. We conclude that the anxiety driven anticipation of pain related to occlusal trigger is processed in the anterior insula and might therefore be a main driver of therapeutic intervention by the splint therapy in CMD.

Effects of occlusal splint therapy in patients with migraine or tension-type headache and comorbid temporomandibular disorder: A randomized controlled trial

BACKGROUND

Migraine and tension-type headache often occur comorbid with temporomandibular disorder; occlusal splint therapy is the most common treatment for temporomandibular disorder. The aim of this study was to assess the effects of occlusal splint therapy on headache symptoms in patients with migraine and/or tension-type headache comorbid with temporomandibular disorder.

METHODS

Sixty adult patients with migraine and/or tension-type headache and comorbid temporomandibular disorder were randomly assigned to individualized occlusal splint therapy applied during day- and nighttime plus usual care (n = 30) or usual care alone (n = 30). Primary outcome was the change in current pain intensity on a 100 mm visual analogue scale from week 1 to week 12. Secondary outcomes included changes in headache days and headache hours assessed by headache diaries over a 2-week period, health-related quality of life (SF-36), and adverse events from week 1 to week 12 and (in the occlusal splint plus usual care group only) to week 24.

RESULTS

No group differences in changes in pain intensity from week 1 to week 12 were found. The number needed to treat was 3.8. Physical quality of life reduced stronger in the usual care group than in the occlusal splint plus usual care group. In the occlusal splint plus usual care group, headache intensity significantly decreased and physical quality of life significantly increased from week 1 to week 12 and to week 24 (all P < .001). No adverse events were reported.

CONCLUSIONS

A day- and night-time occlusal splint therapy in addition to usual care was not superior to usual care alone in patients with chronic headache and comorbid TMD. Four patients need to be treated to induce a minimal clinically relevant improvement in one patient. The small sample size and lack of power limit these findings.

Clinical efficacy of a simplified approach to managing chronic temporomandibular disorders: evidence from a 1-year case series

OBJECTIVE

Chronic temporomandibular disorder (cTMD) produces orofacial pain and limited jaw function and impacts on quality of life. A clinical case series of patients referred to a hospital specialist service is described here.

STUDY DESIGN

In a 1-year consecutive case series of 162 patients with cTMDs, each patient had been managed with self-awareness and jaw exercises, as well as oral appliances. Pain severity and chewing function were scored by using a visual analogue scale (VAS), and quality of life was assessed by using the Oral Health Impact Profile-Temporomandibular Dysfunction (OHIP-TMD).

RESULTS

Females comprised 87% (average age 49 years). Treatment time averaged 20.8 months, and the average pain duration was 2.8 years. The mean VAS pain score fell from 6.9 (standard deviation [SD] 1.6) to 2.0 (SD 1.9) after treatment, giving a "large" effect size of 3.1. Chewing difficulty improvement also showed a "large" effect size (2.5). For the 33 patients for whom longitudinal OHIP-TMD data were available, the mean pretreatment and posttreatment scores of 51.2 (SD 20.9) and 26.2 (SD 17.7) showed a "large" effect size of 1.2.

CONCLUSIONS

A simple noninvasive protocol for managing cTMD with self-help, exercises, and oral devices resulted in clinically and statistically meaningful improvements in pain, function, and quality of life.

Preliminary findings of cerebral responses on transcutaneous vagal nerve stimulation on experimental heat pain

Transcutaneous vagal nerve stimulation (TVNS) is a promising complementary method of pain relief. However, the neural networks associated with its analgesic effects are still to be elucidated. Therefore, we conducted two functional magnetic resonance imaging (fMRI) sessions, in a randomized order, with twenty healthy subjects who were exposed to experimental heat pain stimulation applied to the right forearm using a Contact Heat-Evoked Potential Stimulator. While in one session TVNS was administered bilaterally to the concha auriculae with maximal, non-painful intensity, the stimulation device was switched off in the other session (placebo condition). Pain thresholds were measured before and after each session. Heat stimulation elicited fMRI activation in cerebral pain processing regions. Activation magnitude in the secondary somatosensory cortex, posterior insula, anterior cingulate and caudate nucleus was associated with heat stimulation without TVNS. During TVNS, this association was only seen for the right anterior insula. TVNS decreased fMRI signals in the anterior cingulate cortex in comparison with the placebo condition; however, there was no relevant pain reducing effect over the group as a whole. In contrast, TVNS compared to the placebo condition showed an increased activation in the primary motor cortex, contralateral to the site of heat stimulation, and in the right amygdala. In conclusion, in the protocol used here, TVNS specifically modulated the cerebral response to heat pain, without having a direct effect on pain thresholds.

Amplified Brain Processing of Dentoalveolar Pressure Stimulus in Persistent Dentoalveolar Pain Disorder Patients

AIMS

(1) To determine the brain regions activated by dentoalveolar pressure stimulation in persistent dentoalveolar pain disorder (PDAP) patients, and (2) to compare these activation patterns to those seen in pain-free control subjects.

METHODS

A total of 13 PDAP patients and 13 matched controls completed the study. Clinical pain characteristics and psychosocial data were collected. Dentoalveolar mechanical pain thresholds were determined with a custom-made device over the painful area for patients and were used as the stimulation level during functional magnetic resonance imaging (fMRI) data acquisition. Control subjects received two stimulation levels over matched locations during fMRI scanning: one determined (as above) that evoked equally subjective pain ratings matching those of patients (subjective-pain match) and another nonpainful stimulation level matching the average stimulus intensity provided to patients (stimulus-intensity match). Clinical and psychosocial data were analyzed using independent samples t tests, Mann-Whitney U test, and Spearman rank-order correlation coefficient. fMRI data were analyzed using validated neuroimaging software and tested using a general linear model.

RESULTS

PDAP patients had greater anxiety (P<.0001) and depression scores (P=.001), more jaw function impairment (P<.0001), and greater social impact (P<.0001) than controls. No significant differences were found for brain activation spatial extent (PDAP X Controls subjective pain: P=.48; PDAP X Controls stimulus intensity: P=.12). Brain activations were significantly increased for PDAP patients compared to control subjects when matched to stimulus intensity in several regions related to the sensory-discriminative and cognitive components of pain perception, including the primary and secondary somatosensory cortices, inferior parietal lobule, insula, premotor cortex, prefrontal cortex, and thalamus. When matched to subjective pain ratings, increased brain activations were still present for PDAP patients compared to controls, although to a lesser extent.

CONCLUSION

The present results suggest that dentoalveolar pressure is processed differently in the brain of PDAP patients, and the increased activation in several brain areas is consistent with amplified pain processing.

[Maladaptive plasticity in chronic and neuropathic pain]

Chronic pain results in structural and functional changes of the brain. However, most of the neurophysiologic and imaging studies have been conducted with small sample sizes, some have been reproduced, but studies on larger populations are lacking. Larger epidemiologic studies are currently being performed to show specific structural changes due to chronic pain. Longitudinal studies using neurophysiologic or imaging methods are very rare and often not feasible. Most methods are very complex, which hampers their application in daily practice. But it is not only the complexity of methods, but also a lack of interaction between researchers and practitioners to formulate joint research topics and targets. This article tries to fill the gap between the practicing pain therapist and the researcher in summarizing neurophysiological and imaging results on neuropathic and chronic pain in a clear and simple manner.

Pain-Related Temporomandibular Disorder - Current Perspectives and Evidence-Based Management

Pain-related temporomandibular disorder (TMD) is one of the top three most common chronic pain conditions, along with headaches and back pain. TMD has complex pathophysiology and significant associations with a variety of other chronic pain conditions, eg fibromyalgia, irritable bowel syndrome and migraine. Chronic TMD is associated with a negative impact upon quality of life and high levels of healthcare utility. It is important that clinicians are able to diagnose TMD correctly, provide appropriate management in keeping with current evidence-based practice, and identify when to refer patients to specialist care. The presence of risk factors, eg anxiety, depression, pain-related disability and chronic pain conditions elsewhere in the body, may help to identify which TMD patients require referral for multidisciplinary management. TMD should be managed using a holistic approach, incorporating patient education and encouragement towards self-management. TMD care pathways should consider using the three'pillars'of pain management: physical therapies, pharmacotherapy and clinical psychology.