Scandinavian Center for Orofacial Neurosciences

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Scandinavian Center for Orofacial Neurosciences

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Zhang Y.,Nanjing Medical University | Shao S.,Nanjing Medical University | Zhang J.,Nanjing Medical University | Wang L.,Nanjing Medical University | And 5 more authors.
Pain | Year: 2017

Temporal summation of nociceptive inputs may be an important pathophysiological mechanism in temporomandibular disorders (TMD) pain; however, it remains unknown how natural jaw function relates to underlying pain mechanisms. This study evaluated changes in pain and movement patterns during repeated jaw movements in patients with painful temporomandibular joints (TMJ) compared with healthy controls. Twenty patients with TMD with TMJ pain, and an anterior disk displacement without reduction and 20 age-and gender-matched healthy volunteers were included. Participants performed 20 trials (4 × 5 sessions) of standardized and repeated mandibular movements, and scored the movement-associated pain intensity on 0 to 10 numeric rating scale in addition to measurements of jaw movements. Patients with TMJ pain reported higher baseline pain compared to the control group for all types of jaw movements (P = 0.001) and significant increases in numeric rating scale pain scores by repetition of jaw movements (P < 0.001), which was not observed in the control group (P > 0.05). Jaw total opening distance (P = 0.030), maximum opening velocity (P = 0.043) and average closing velocity (P = 0.044) in the TMJ pain group were significantly reduced during the repeated movements. In the control group, however, total opening distance (P = 0.499), maximum opening velocity (P = 0.064), and average closing velocity (P = 0.261) remained unchanged, whereas average opening velocity (P = 0.040) and maximum closing velocity (P = 0.039) increased. The study demonstrates that repeated jaw movements constitute a sufficient and adequate stimulation for triggering temporal summation effects associated with significant inhibition of motor function in painful TMJs. These findings have practical implications for diagnosis of TMD pain and for more mechanism-driven management protocols in the future. © 2017 International Association for the Study of Pain.

Kothari S.F.,University of Aarhus | Kothari S.F.,Scandinavian Center for Orofacial Neurosciences | Baad-Hansen L.,University of Aarhus | Baad-Hansen L.,Scandinavian Center for Orofacial Neurosciences | And 3 more authors.
Journal of Oral and Facial Pain and Headache | Year: 2017

To propose a visual method to screen and assess psychosocial functioning in temporomandibular disorder (TMD) pain patients in comparison with age- and gender-matched healthy controls by forming individual profiles and to evaluate the association between psychosocial profiles and quantitative sensory testing (QST) findings of TMD pain patients. Methods: TMD patients (n = 58) and control participants (n = 41) completed a set of questionnaires profiling their psychosocial function, and QST was performed at the temporomandibular joint (TMJ) on both sides of the face in all participants. Psychosocial parameters from the Research Diagnostic Criteria for TMD (RDC/TMD), Oral Health Impact Profile (OHIP), and Pain Catastrophizing Scale (PCS) instruments were transformed into T scores, and QST parameters were transformed into z scores based on reference data. Group differences for psychosocial T scores were analyzed with t tests. T scores of psychosocial parameters and z scores of QST parameters were correlated using Spearman's correlation (ρ). Results: Most (96.6%) TMD pain patients exhibited one or more parameters indicative of psychosocial distress, with psychological disability scores being the scores most frequently encountered outside the reference 95% confidence intervals (CI). TMD patients were psychosocially more distressed with regard to all psychosocial parameters compared with controls (P < .009). After Bonferroni corrections, a significant correlation was detected between the sleep dysfunction parameter and mechanical detection threshold (MDT) in TMD pain patients (ρ = 0.427, P < .001). Conclusion: T score psychosocial profiles created an easy overview of psychosocial function in TMD pain patients. Increased sensitivity to tactile stimuli was associated with higher sleep dysfunction T scores. © 2017 by Quintessence Publishing Co Inc.

Dagsdottir L.K.,University of Aarhus | Dagsdottir L.K.,Scandinavian Center for Orofacial Neurosciences | Skyt I.,University of Aarhus | Vase L.,University of Aarhus | And 7 more authors.
Experimental Brain Research | Year: 2015

Patients suffering from persistent orofacial pain may sporadically report that the painful area feels “swollen” or “differently,” a phenomenon that may be conceptualized as a perceptual distortion because there are no clinical signs of swelling present. Our aim was to investigate whether standardized experimental pain and sensory deprivation of specific orofacial test sites would lead to changes in the size perception of these face areas. Twenty-four healthy participants received either 0.2 mL hypertonic saline (HS) or local anesthetics (LA) into six regions (buccal, mental, lingual, masseter muscle, infraorbital and auriculotemporal nerve regions). Participants estimated the perceived size changes in percentage (0 % = no change, −100 % = half the size or +100 % = double the size), and somatosensory function was checked with tactile stimuli. The pain intensity was rated on a 0–10 Verbal Numerical Rating Scale (VNRS), and sets of psychological questionnaires were completed. HS and LA were associated with significant self-reported perceptual distortions as indicated by consistent increases in perceived size of the adjacent face areas (P ≤ 0.050). Perceptual distortion was most pronounced in the buccal region, and the smallest increase was observed in the auriculotemporal region. HS was associated with moderate levels of pain VNRS = 7.3 ± 0.6. Weak correlations were found between HS-evoked perceptual distortion and level of dissociation in two regions (P < 0.050). Experimental pain and transient sensory deprivation evoked perceptual distortions in all face regions and overall demonstrated the importance of afferent inputs for the perception of the face. We propose that perceptual distortion may be an important phenomenon to consider in persistent orofacial pain conditions. © 2015, Springer-Verlag Berlin Heidelberg.

Baad-Hansen L.,University of Aarhus | Baad-Hansen L.,Scandinavian Center for Orofacial Neurosciences | Benoliel R.,Rutgers University
Cephalalgia | Year: 2017

Definition and taxonomy This review deals with neuropathic pain of traumatic origin affecting the trigeminal nerve, i.e. painful post-traumatic trigeminal neuropathy (PTTN). Symptomatology The clinical characteristics of PTTN vary considerably, partly due to the type and extent of injury. Symptoms involve combinations of spontaneous and evoked pain and of positive and negative somatosensory signs. These patients are at risk of going through unnecessary dental/surgical procedures in the attempt to eradicate the cause of the pain, due to the fact that most dentists only rarely encounter PTTN. Epidemiology Overall, approximately 3% of patients with trigeminal nerve injuries develop PTTN. Patients are most often female above the age of 45 years, and both physical and psychological comorbidities are common. Pathophysiology PTTN shares many pathophysiological mechanisms with other peripheral neuropathic pain conditions. Diagnostic considerations PTTN may be confused with one of the regional neuralgias or other orofacial pain conditions. For intraoral PTTN, early stages are often misdiagnosed as odontogenic pain. Pain management Management of PTTN generally follows recommendations for peripheral neuropathic pain. Expert opinion International consensus on classification and taxonomy is urgently needed in order to advance the field related to this condition. © International Headache Society.

Skyt I.,University of Aarhus | Dagsdottir L.,University of Aarhus | Dagsdottir L.,Scandinavian Center for Orofacial Neurosciences | Vase L.,University of Aarhus | And 9 more authors.
Journal of Pain | Year: 2015

Anecdotally, orofacial pain patients sometimes report that the painful face area feels "swollen." Because there are no clinical signs of swelling, such illusions may represent perceptual distortions. In this study, we examine whether nociceptive stimulation can lead to perceptual distortion of the face in a way similar to that of local anesthesia. Sixteen healthy participants received injections of.4 mL hypertonic saline to induce short-term nociceptive stimulation,.4 mL mepivacaine (local anesthetic) to transiently block nerve transduction, and.4 mL isotonic saline as a control condition. Injections were administered in both the infraorbital and the mental nerve regions. Perceptual distortions were conceptualized as perceived changes in magnitude of the injected areas and the lips, and they were measured using 1) a verbal subjective rating scale and 2) a warping procedure. Prior to the study, participants filled in several psychological questionnaires. This study shows that both nociceptive stimulation (P <.05) and transient blocking of nerve transduction (P <.05) can lead to perceptual distortion of the face. A test-retest experiment including 9 new healthy subjects supported the results. Perceptual distortions were positively correlated with the psychological variable of dissociation in several conditions (P <.05). Perceptual distortions may therefore be influenced by somatosensory changes and psychological mechanisms. Perspective Knowledge of the factors that influence the perception of the face is important to understand the possible implications of perceptual distortions in orofacial pain disorders (and possibly other chronic pain states). Such information may ultimately open up new avenues of treatment for persistent orofacial pain. © 2015 American Pain Society.

Kothari S.F.,University of Aarhus | Kothari S.F.,Scandinavian Center for Orofacial Neurosciences | Baad-Hansen L.,University of Aarhus | Baad-Hansen L.,Scandinavian Center for Orofacial Neurosciences | And 4 more authors.
Pain | Year: 2015

The pathophysiology and underlying pain mechanisms of temporomandibular disorders (TMD) are poorly understood. The aims were to assess somatosensory function at the temporomandibular joints (TMJs) and to examine whether conditioned pain modulation (CPM) differs between TMD pain patients (n 34) and healthy controls (n 34). Quantitative sensory testing was used to assess the somatosensory function. Z-scores were calculated for patients based on reference data. Conditioned pain modulation was tested by comparing pressure pain thresholds (PPTs) before, during, and after the application of painful and nonpainful cold stimuli. Pressure pain thresholds were measured at the most painful TMJ and thenar muscle (control). Data were analyzed with analyses of variance. Most (85.3%) of the patients exhibited at least 1 or more somatosensory abnormalities at the most painful TMJ with somatosensory gain with regard to PPT and punctate mechanical pain stimuli, and somatosensory loss with regard to mechanical detection and vibration detection stimuli as the most frequent abnormalities. There was a significant CPM effect (increased PPT) at both test sites during painful cold application in healthy controls and patients (P < 0.001). There was no significant difference in the relative CPM effect during painful cold application between groups (P 0.227). In conclusion, somatosensory abnormalities were commonly detected in TMD pain patients and CPM effects were similar in TMD pain patients and healthy controls. © 2015 International Association for the Study of Pain.

PubMed | University of Aarhus, Chinese PLA General Hospital and Scandinavian Center for Orofacial Neurosciences
Type: Journal Article | Journal: European journal of oral sciences | Year: 2016

The aim of this study was to investigate the impact of visual observational conditions on performance during a standardized tongue-protrusion training (TPT) task and to evaluate subject-based reports of helpfulness, disturbance, pain, and fatigue, due to the observational conditions on 0-10 numerical rating scales. Forty-eight healthy participants performed a 1-h standard TPT task. Participants were randomly assigned to one of the following three groups with different observational conditions: group 1, model observation (participants watched a prerecorded video showing standard TPT before optimal TPT being performed); group 2, self-observation (participants watched live video feedback of their own TPT performance); and group 3, control group (participants performed the TPT with no conditioning). There was no overall difference between groups but TPT performance increased over time. A significant grouptime interaction indicated that the self-observation group performed significantly better than the model-observation group in the last 20 min of TPT. The subject-based reports of video helpfulness showed that the model-observation group rated the prerecorded video as more helpful for TPT performance compared with the other groups but there was no significant difference between groups regarding the level of disturbance, pain, or fatigue. Self-observation of tongue-training facilitated behavioral aspects of tongue motor learning compared with model observation but not compared with control.

PubMed | University of British Columbia, University of Aarhus, Scandinavian Center for Orofacial Neurosciences and Linköping University
Type: Journal Article | Journal: European journal of pain (London, England) | Year: 2016

A randomized, double-blinded, placebo-controlled study was conducted to investigate if single monosodium glutamate (MSG) administration would elevate muscle/serum glutamate concentrations and affect muscle pain sensitivity in myofascial temporomandibular disorders (TMD) patients more than in healthy individuals.Twelve myofascial TMD patients and 12 sex- and age-matched healthy controls participated in two sessions. Participants drank MSG (150mg/kg) or NaCl (24mg/kg; control) diluted in 400mL of soda. The concentration of glutamate in the masseter muscle, blood plasma and saliva was determined before and after the ingestion of MSG or control. At baseline and every 15min after the ingestion, pain intensity was scored on a 0-10 numeric rating scale. Pressure pain threshold, pressure pain tolerance (PPTol) and autonomic parameters were measured. All participants were asked to report adverse effects after the ingestion.In TMD, interstitial glutamate concentration was significantly greater after the MSG ingestion when compared with healthy controls. TMD reported a mean pain intensity of 2.8/10 at baseline, which significantly increased by 40% 30min post MSG ingestion. At baseline, TMD showed lower PPTols in the masseter and trapezius, and higher diastolic blood pressure and heart rate than healthy controls. The MSG ingestion resulted in reports of headache by half of the TMD and healthy controls, respectively.These findings suggest that myofascial TMD patients may be particularly sensitive to the effects of ingested MSG. WHAT DOES THIS STUDY ADD?: Elevation of interstitial glutamate concentration in the masseter muscle caused by monosodium glutamate (MSG) ingestion was significantly greater in myofascial myofascial temporomandibular disorders (TMD) patients than healthy individuals. This elevation of interstitial glutamate concentration in the masseter muscle significantly increased the intensity of spontaneous pain in myofascial TMD patients.

PubMed | Scandinavian Center for Orofacial Neurosciences and University of Sao Paulo
Type: | Journal: Clinical oral investigations | Year: 2017

The nociceptive blink reflex (nBR) can be useful to investigate trigeminal nociceptive function. The aim of this study was to estimate the reliability of the nBR evoked by electrical stimulation of the three branches of the trigeminal nerve under the following conditions: over time (test-retest and intrarater reliability) and by two examiners (interrater reliability).Twenty-one healthy participants were evaluated in two sessions (24h apart). The nBR was elicited by a so-called nociceptive-specific electrode placed over the entry zone of the right supraorbital (V1R), infraorbital (V2R), mental (V3R), and left infraorbital (V2L) nerve. The outcomes were individual electrical sensory (I ICCs were fair to excellent in 82% of the psychophysical measures (fair 21%, good 31%, excellent 30%) and in 86% of V1R, V2R, and V2L nBR parameters, whereas 52% of V3R showed poor reliability. ICCs for intrarater reliability were fair to good in 70% of measurements (fair 20%, good 50%) and in 75% of interrater measurements after the recalibration (fair 55%, good 20%). All kappa values showed at least fair agreement and the majority of the nBR measures (93%) presented moderate to excellent reliability.The nBR and its associated psychophysical measures can be considered a sufficiently reliable test.The nBR can be recommended as an electrophysiological technique to assess trigeminal nociceptive function.

PubMed | Karolinska Institutet and Scandinavian Center for Orofacial Neurosciences
Type: | Journal: Clinical oral investigations | Year: 2016

The study was designed to investigate if alteration of different orofacial afferent inputs would have different effects on oral fine motor control and to test the hypothesis that reduced afferent inputs will increase the variability of bite force values and jaw muscle activity, and repeated training with splitting of food morsel in conditions with reduced afferent inputs would decrease the variability and lead to optimization of bite force values and jaw muscle activity.Forty-five healthy volunteers participated in a single experimental session and were equally divided into incisal, mucosal, and block anesthesia groups. The participants performed six series (with ten trials) of a standardized hold and split task after the intervention with local anesthesia was made in the respective groups. The hold and split forces along with the corresponding jaw muscle activity were recorded and compared to a reference group.The hold force and the electromyographic (EMG) activity of the masseter muscles during the hold phase were significantly higher in the incisal and block anesthesia group, as compared to the reference group (P<0.001). However, there was no significant effect of groups on the split force (P=0.975) but a significant decrease in the EMG activity of right masseter in mucosal anesthesia group as compared to the reference group (P=0.006). The results also revealed that there was no significant effect of local anesthesia on the variability of the hold and split force (P<0.677). However, there was a significant decrease in the variability of EMG activity of the jaw closing muscles in the block anesthesia group as compared to the reference group (P<0.041), during the hold phase and a significant increase in the variability of EMG activity of right masseter in the mucosal anesthesia group (P=0.021) along with a significant increase in the EMG activity of anterior temporalis muscle in the incisal anesthesia group, compared to the reference group (P=0.018), during the split phase.The results of the present study indicated that altering different orofacial afferent inputs may have different effects on some aspects of oral fine motor control. Further, inhibition of afferent inputs from the orofacial or periodontal mechanoreceptors did not increase the variability of bite force values and jaw muscle activity; indicating that the relative precision of the oral fine motor task was not compromised inspite of the anesthesia. The results also suggest the propensity of optimization of bite force values and jaw muscle activity due to repeated splitting of the food morsels, inspite of alteration of sensory inputs.Skill acquisition following a change in oral sensory environment is crucial for understanding how humans learn and re-learn oral motor behaviors and the kind of adaptation that takes place after successful oral rehabilitation procedures.

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