Signal to noise ratio of masticatory muscle activity of functional and non-functional oral tasks.

BACKGROUND: Electromyographic activity (EMG) of masticatory muscles during wakefulness is understudied. It is unclear if single channel ambulatory EMG devices are sensitive enough to detect masticatory muscle activity (MMA) during wakefulness. OBJECTIVES: To compare the MMA of various oral tasks recorded with a single channel EMG device ((Grindcare4-datalogger Prototype device) (GC4-ß)) and a conventional EMG (cEMG) device. METHODS: EMG activity of 30 standardised oral tasks was recorded unilaterally from the masseter and anterior temporalis muscle in 24 healthy volunteers using GC4-ß and a cEMG device. To compare the EMG data, signal-to-noise ratios (SNR) were calculated as a way to normalise EMG activity across tasks. Analysis of variance was used to compare the SNR between the devices, muscles and oral tasks. RESULTS: SNR measured from GC4-ß was overall significantly higher than the cEMG device (p =.001). The SNR for maximum voluntary contraction (MVC) was significantly higher than all other tasks (p <.001). SNR for temporalis with GC4-ß was significantly higher for MVC, hard food, soft food, gum chewing (dominant side), rhythmic clenching and upper lip biting compared to the cEMG device (p <.021). The SNR for masseter with GC4-ß was significantly higher for hard food and gum chewing (dominant side), rhythmic clenching, rhythmic biting of an object and yawning compared to the cEMG device (p <.022). CONCLUSIONS: This study provides novel insight into the EMG patterns of numerous oral tasks enhancing knowledge of physiological differences between the masticatory muscles. Further, single channel EMG devices can effectively measure the EMG activity of various oral tasks during wakefulness.

Comparison of force profiles from two musculoskeletal palpation methods: A methodological study.

BACKGROUND: The Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol recommends a 5 s and 1 kg force dynamic palpation around the lateral condylar pole of the temporomandibular joint. However, the accuracy and precision of the generated force are not known. OBJECTIVE: To assess and compare the force profiles generated from dynamic palpation manually and using a palpometer, based on the forces and time recommendations suggested by the DC/TMD protocol. METHODS: Nineteen healthy adults applied forces of 0.5 kg, 1.0 kg and 2.0 kg on a calibrated force sensor in a circular motion within target times of 2 s and 5 s. Participants used their right index finger for manual palpation and a calibrated palpometer for device-assisted palpation. Ten repetitions of each target force at both target times were applied. Time taken to complete each application was recorded. Repeated measures analysis of variance was used for analysis of accuracy measured as the relative difference between targeted force and actual force values and precision measured as the coefficient of variation (CV) within the 10 repeated measurements. RESULTS: Accuracy was significantly lower (better) and precision higher (lower CV) with the palpometer than with manual palpation (p < .001). There were significant differences in accuracy and precision between the different forces but not palpation times. Most participants could not achieve the target times and tended to be faster, irrespective of the palpation method (p > .063). CONCLUSION: A palpometer is a more accurate and precise palpation method for dynamic force assessment compared to manual palpation; however, it remains difficult to standardize the palpation duration.

Impact of oral motor task training on corticomotor pathways and diadochokinetic rates in young healthy participants.

BACKGROUND: Studies addressing the training-induced neuroplasticity and interrelationships of the lip, masseter, and tongue motor representations in the human motor cortex using single syllable repetition are lacking. OBJECTIVE: This study investigated the impact of a repeated training in a novel PaTaKa diadochokinetic (DDK) orofacial motor task (OMT) on corticomotor control of the lips, masseter, and tongue muscles in young healthy participants. METHODS: A total of 22 young healthy volunteers performed 3 consecutive days of training in an OMT. Transcranial magnetic stimulation was applied to elicit motor evoked potentials (MEPs) from the lip, masseter, tongue, and first dorsal interosseous (FDI, internal control) muscles. MEPs were assessed by stimulus-response curves and corticomotor mapping at baseline and after OMT. The DDK rate from PaTaKa single syllable repetition and numeric rating scale (NRS) scores were also obtained at baseline and immediately after each OMT. Repeated-measures analysis of variance was used to detect differences at a significance level of 5%. RESULTS: There was a significant effect of OMT and stimulus intensity on the lips, masseter, and tongue MEPs compared to baseline (p < .001), but not FDI MEPs (p > .05). OMT increased corticomotor topographic maps area (p < .001), and DDK rates (p < .01). CONCLUSION: Our findings suggest that 3 consecutive days of a repeated PaTaKa training in an OMT can induce neuroplastic changes in the corticomotor pathways of orofacial muscles, and it may be related to mechanisms underlying the improvement of orofacial fine motor skills due to short-term training. The clinical utility should now be investigated.

Characterization of persistent post-traumatic headache and management strategies in adolescents and young adults following mild traumatic brain injury.

Characteristics of persistent post-traumatic headache (PTH) in young individuals are poorly known leading to diagnostic problems and diverse management. We aimed to describe headache phenotypes and self-reported management strategies in young individuals with PTH following mild traumatic brain injury (mTBI). A comprehensive structured questionnaire was used to evaluate headache phenotypes/characteristics and management strategies to relieve headache in 107, 15-30-year-old individuals with PTH. Around 4 months post-injury, migraine-like headache in combination with tension-type like headache (40%) was the most commonly encountered headache phenotype followed by migraine-like headache (36%). Around 50% reported aura-like symptoms before/during the headache attack. Medication-overuse headache was diagnosed in 10%. Stress, sleep disturbances, and bright lights were the most common trigger factors. More than 80% reported that their headache was worsened by work-related activity and alleviated by rest/lying down. Simple analgesics were commonly used (88%) whereas prophylactic drugs were rarely used (5%). Bedrest and physiotherapy were also commonly used as management strategies by 56% and 34% of the participants, respectively. In conclusion, most young individuals with PTH after mTBI presented with combined migraine-like and tension-type-like headache followed by migraine-like headache, only. Preventive headache medication was rarely used, while simple analgesics and bedrest were commonly used for short-term headache relief.

Facilitatory Effect of Intermittent Repetitive Transcranial Magnetic Stimulation on Perceptual Distortion of the Face.

Orofacial pain patients often report that the painful facial area is "swollen" without clinical signs - known as perceptual distortion (PD). The neuromodulatory effect of facilitatory repetitive transcranial magnetic stimulation (rTMS) on PD in healthy individuals was investigated, to provide further support that the primary somatosensory cortex (SI) is involved in facial PD. Participants were allocated to active (n = 26) or sham (n = 26) rTMS group in this case-control study. PD was induced experimentally by injecting local anesthesia (LA) in the right infraorbital region. PD was measured at baseline, 6 min after LA, immediately, 20 and 40 min after rTMS. Intermittent theta-burst stimulation (iTBS) as active rTMS and sham rTMS was applied to the face representation area of SI at 10 min after LA. The magnitude of PD was compared between the groups. The magnitude of PD significantly increased immediately after iTBS compared with sham rTMS (P = .009). The PD was significantly higher immediately after iTBS compared to 6 min after LA (P = .004) in the active rTMS group, but not in the sham rTMS group (P = .054). iTBS applied to a somatotopic-relevant cortical region appears to facilitate facial PD further supporting the involvement of SI in the processing of one´s own face and PD. PERSPECTIVE: This study provides information on neural substrate responsible for processing of perceptual distortion of the face which is speculated to contribute to the chronification of orofacial pain. The findings of this study may aid in mechanism-based management of the condition in orofacial pain disorders and possibly other chronic pain states.

The relationship between headache-attributed disability and lost productivity: 2. Empirical evidence from population-based studies in nine disparate countries.

BACKGROUND: Headache disorders are disabling, with major consequences for productivity, yet the literature is silent on the relationship between headache-attributed disability and lost productivity, often erroneously regarding the two as synonymous. We evaluated the relationship empirically, having earlier found that investment in structured headache services would be cost saving, not merely cost-effective, if reductions in headache-attributed disability led to > 20% pro rata recovery of lost productivity. METHODS: We used individual participant data from Global Campaign population-based studies conducted in China, Ethiopia, India, Nepal, Pakistan and Russia, and from Eurolight in Lithuania, Luxembourg and Spain. We assessed relationships in migraine and probable medication-overuse headache (pMOH), the most disabling common headache disorders. Available symptom data included headache frequency, usual duration and usual intensity. We used frequency and duration to estimate proportion of time in ictal state (pTIS). Disability, in the sense used by the Global Burden of Disease study, was measured as the product of pTIS and disability weight for the ictal state. Impairment was measured as pTIS * intensity. Lost productivity was measured as lost days (absence or < 50% productivity) from paid work and corresponding losses from household work over the preceding 3 months. We used Spearman correlation and linear regression analyses. RESULTS: For migraine, in a linear model, we found positive associations with lost paid worktime, significant (p < 0.05) in many countries and highly significant (p < 0.001) in some despite low values of R2 (0-0.16) due to high variance. With lost household worktime and total lost productivity (paid + household), associations were highly significant in almost all countries, although still with low R2 (0.04-0.22). Applying the regression equations for each country to the population mean migraine-attributed disability, we found pro rata recoveries of lost productivity in the range 16-56% (> 20% in all countries but Pakistan). Analysing impairment rather than disability increased variability. For pMOH, with smaller numbers, associations were generally weaker, occasionally negative and mostly not significant. CONCLUSION: Relief of disability through effective treatment of migraine is expected, in most countries, to recover > 20% pro rata of lost productivity, above the threshold for investment in structured headache services to be cost saving.

The relationship between headache-attributed disability and lost productivity: 1. A review of the literature.

BACKGROUND: Headache disorders are disabling and have a significant impact on productivity. The relationship between these two consequences is of considerable economic and political interest. We enquired into it through a systematic search of the English-language literature. METHODS: We followed PRISMA guidelines in specifying search terms and syntax and in article selection. We used the term "disability" in the search, accepting any meaning that authors attached to it, but this proved problematic. Accordingly, we adopted the definition used in the Global Burden of Disease study. In article selection, we included only those that purported to measure disability as so defined and lost productivity. We reviewed the full texts of those selected. We included further articles identified from review of the bibliographies of selected articles. RESULTS: The literature search found 598 studies, of which 21 warranted further review. Their bibliographies identified another four of possible relevance. On full-text reading of these 25, all were rejected. Ten applied incompatible definitions of disability and/or lost productivity. Two did not measure both. Four reported lost productivity but not disability. Eight studies reported and measured both but did not assess the association between them or provide the means of doing so. One was purely methodological. CONCLUSIONS: The literature is silent on the relationship between headache-attributed disability and lost productivity. In view of its health economic and political importance, empirical studies are required to remedy this. A prerequisite is to clarify what is meant by "disability" in this context.

Painful and non-painful symptoms evoked by experimental bracing and thrusting of the mandible in healthy individuals.

BACKGROUND: Bruxism may involve bracing and thrusting of the mandible, in addition to clenching or grinding of the teeth. It is unclear how bracing and thrusting may contribute to potential musculoskeletal symptoms associated with bruxism. OBJECTIVE: To examine the effect of experimental bracing and thrusting of the mandible on the development of musculoskeletal symptoms in healthy volunteers. METHODS: Thirty healthy volunteers performed six trials of 5 min of repeated bracing and thrusting of the mandible. Bracing involved forcefully maintaining maximum protruded position (5 s with 1 s rest in between), whereas thrusting involved forcefully moving the mandible in a forward direction and back (1 Hz). The participants rated pain, unpleasantness, soreness, fatigue, tension, stiffness, stress and headache on 10-cm visual analogue scales (VAS) before, immediately and 24 h after the tasks. Pain drawings were obtained and maximum voluntary protrusive force (MVPF) was determined before and after the tasks. The outcome parameters for each task were compared between the time points. RESULTS: There was a significant increase in the VAS scores (2-4/10) of pain, unpleasantness, soreness, fatigue, tension, stiffness and stress immediately following the tasks compared to baseline and 24 h after the tasks (p < .008). Pain was frequently reported in masseter muscles. MVPF values were significantly higher immediately (p < .001) and 24 h after thrusting (p < .001) and bracing (p = .012) tasks compared to the baseline. CONCLUSIONS: Experimental bracing and thrusting of the mandible evoked transient, mild-to-moderate levels of muscle pain, fatigue, tension and stiffness and increased unpleasantness and stress scores in healthy volunteers.

Effect of repetitive transcranial magnetic stimulation on altered perception of One's own face.

BACKGROUND: Chronic orofacial pain (COP) patients often perceive the painful face area as "swollen" without clinical signs; such self-reported illusions of the face are termed perceptual distortion (PD). The pathophysiological mechanisms underlying PD remain elusive. OBJECTIVE: To test the neuromodulatory effect of repetitive transcranial magnetic stimulation (rTMS) on PD in healthy individuals, to gain insight into the cortical mechanisms underlying PD. METHODS: PD was induced experimentally by injections of local anesthetic (LA) around the infraorbital nerve and measured as perceived size changes of the affected area. Participants were randomly allocated to inhibitory rTMS (n = 26) or sham rTMS (n = 26) group. The participants rated PD at baseline, 6 min after LA, immediately, 20 and 40 min after rTMS. The rTMS (inhibitory and sham) was applied to face (lip) representation area of primary somatosensory cortex (SI) as an intervention at 10 min after the LA, when the magnitude of PD is large. As inhibitory rTMS, continuous theta-burst stimulation paradigm (50 Hz) for 40s was employed to inhibit cortical activity. RESULTS: We demonstrated a significant decrease in the magnitude of PD immediately and 20 min after the application of inhibitory rTMS compared with sham rTMS (P < 0.006). In two control experiments, we also showed that peripheral muscle stimulation and stimulation of a cortical region other than the lip representation area had no effect on the magnitude of the PD. CONCLUSIONS: Inhibitory rTMS applied to a somatotopical-relevant cortical region modulates PD of the face in healthy individuals and could potentially have therapeutic implications for COP patients.

Quantitative and qualitative assessment of sensory changes induced by local anesthetics block of two different trigeminal nerve branches.

OBJECTIVES: The aims were to use different techniques to assess the degree of sensory changes and magnitude of perceived size changes in the facial region induced by nerve blocks of two different trigeminal nerve branches in healthy participants. MATERIALS AND METHODS: This placebo-controlled study included 30 healthy volunteers. The participants underwent quantitative and qualitative sensory testing (QST and QualST) thrice: before, 10 min, and 2 h after mental (n = 15) and infraorbital (n = 15) nerve blocks and during control (saline) sessions. Perceived numbness, temperature changes, and perceptual distortion were also measured at all time points during the nerve block and control sessions. Differences in outcome parameters between the sessions and time points were analyzed using analyses of variance and McNemar's tests. RESULTS: There was a significant degree of sensory loss to most QST and all QualST parameters, with significant numbness and increased perceived size at the injection site 10 min and 2 h after the nerve blocks compared with saline (P < 0.030) and the baseline (P < 0.042). Two hours after the nerve blocks, the sensitivity was significantly closer to baseline than after 10 min to most of the QST parameters (P < 0.011). CONCLUSIONS: QST and QualST revealed that the nerve blocks in the orofacial region resulted in complete or partial blockade of afferent nerve fibers mediating thermal and mechanical function for more than 2 h with significant numbness and perceptual distortion. CLINICAL RELEVANCE: Both QST and QualST can provide information on the degree of blockade of afferent nerve fibers after nerve blocks in the orofacial region.

Oral Health and Brain Injury: Causal or Casual Relation?

BACKGROUND: To systematically review the current literature investigating the association between oral health and acquired brain injury. METHODS: A structured search strategy was applied to PubMed, Embase, Web of Science, and CENTRAL electronic databases until March 2017 by 2 independent reviewers. The preferred reporting items for systematic review and meta-analysis guidelines were used for systematic review. RESULTS: Even though the objective was to assess the association between oral health and acquired brain injury, eligible studies focused solely on different forms of stroke and stroke subtypes. Stroke prediction was associated with various factors such as number of teeth, periodontal conditions (even after controlling for confounding factors), clinical attachment loss, antibody levels to Aggregatibacter actinomycetemcomitans and Prevotella intermedia. The literature showed no consensus on the possible association between gingivitis and stroke. Patients with stroke generally had poorer oral hygiene practices and oral health. Dental prophylaxis and professional intervention reduced the incidence of stroke. CONCLUSIONS: Overall, oral health and stroke were related. Periodontitis and tooth loss were independently associated with stroke. However, prevention and timely intervention may reduce the risk of stroke. Stroke was the main cerebral lesion studied in the literature, with almost no publications on other brain lesions.

Psychosocial Profiles of Temporomandibular Disorder Pain Patients: Proposal of a New Approach to Present Complex Data.

AIMS: 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.

Oral health status in patients with acquired brain injury: a systematic review.

OBJECTIVE: To undertake a systematic review of the current knowledge and future perspectives regarding the status of various oral health factors, including social and behavioral aspects, in patients with acquired brain injury (ABI). STUDY DESIGN: A structured search strategy was applied to PubMed, Embase, and Scopus electronic databases until January 2016 to identify studies presenting assessments of the oral health status of patients afflicted with any kind of ABI. The search strategy was restricted to English-language publications that enrolled patients aged more than 18 years. Studies on the association of oral health conditions and brain injury were excluded. No study was excluded based on its qualitative analysis. RESULTS: A total of 27 studies were reviewed. Stroke was the most commonly studied ABI. Stroke patients had a higher number of missing teeth, poorer plaque and gingival index scores, and higher colonization of Candida albicans in saliva, all of which were significantly reduced after intervention. Oral health-related quality of life was poorer in patients compared to the general population. CONCLUSION: Stroke was the most predominant brain injury condition studied in the literature, with few publications focusing on other forms of brain injury. Overall, oral health has been noted to be poor in patients with ABI, but oral hygiene and oral health-related quality of life have been found to improve when oral hygiene interventions are provided to patients.

Pain profiling of patients with temporomandibular joint arthralgia and osteoarthritis diagnosed with different imaging techniques.

BACKGROUND: Clinical differentiation between pain mechanisms of temporomandibular joint (TMJ) arthralgia and osteoarthritis (OA) is challenging. The aims were to compare somatosensory function at the TMJs and conditioned pain modulation (CPM) effects between TMJ arthralgia and OA patients diagnosed clinically and based on different imaging techniques and age- and gender-matched healthy controls (n = 41). METHODS: Patients (n = 58) underwent standard clinical examination and three different TMJ imaging modalities. After each examination, they were classified into arthralgia or OA based on the findings. TMJ region somatosensory testing was performed in all participants. Z-scores were calculated for patients based on healthy reference data. CPM was tested by comparing pressure pain thresholds (PPTs) at TMJ and thenar (control) before, during and after the application of painful and nonpainful cold stimuli. Data were analyzed using analyses of variance. RESULTS: Somatosensory abnormalities were commonly detected in both patient groups. Assessment of somatosensory function at the TMJ revealed that arthralgia patients were less sensitive to warmth, cold and tactile stimuli than OA patients (P < 0.048). OA patients showed pressure hyperalgesia compared with arthralgia patients (P = 0.025). There was a significant CPM effect at both test sites during painful cold application in all groups (P < 0.001). There was no significant difference in the relative CPM effect between groups except for clinically diagnosed arthralgia patients showing reduced CPM effect compared with controls (P = 0.047). CONCLUSIONS: Pain profiles including somatosensory function differed between TMJ arthralgia and OA patients although CPM effects were similar in patients and controls. Thus, different TMJ pain conditions may share common pain mechanisms but the present study for the first time also indicated that differential pain mechanisms could be involved.

Somatosensory assessment and conditioned pain modulation in temporomandibular disorders pain patients.

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.

Comparison of techniques for evaluation of deep pain sensitivity in the craniofacial region.

AIMS: To determine whether a new palpometer and manual palpation can detect site-to-site differences in human craniofacial pain sensitivity in a similar pattern to that of an electronic pressure algometer and subsequently to compare between-session and within-session variability of palpometer and manual palpation. METHODS: Sixteen volunteers participated. Experiment 1 was carried out in two sessions. In session 1, pressure pain thresholds (PPT) were determined with a pressure algometer at nine craniofacial sites. Manual palpation and the palpometer were then applied to all sites, and subjects scored perceived pressure/pain on a 0 to 100 numerical rating scale (NRS). Mean scores were compared using analysis of variance (ANOVA). Ten of the volunteers were recalled for a second session and the same protocol was carried out except for assessment of PPTs to establish between-session variability. In experiment 2, three craniofacial sites were examined using the palpometer and manual palpation. Both techniques were repeated 10 times at each site and coefficient of variation (CV) was compared to determine within-session variability. RESULTS: There were no significant differences in NRS scores evoked by manual palpation or palpometer at any test site between repeated sessions. The CV varied between techniques, with lower within-session variability for the palpometer compared with manual palpation (P = .03). CONCLUSION: The palpometer and manual palpation could detect differences in craniofacial sensitivity in healthy subjects, with no significant differences between repeated sessions. All techniques showed the highest sensitivity at the retromandibular site and the lowest at the temporalis muscle site. The palpometer had lower within-session variability compared with manual palpation.