Associations among masticatory muscle activity, physical activity and self-reported oral behaviours in adult women.

OBJECTIVES: To examine the relationship between masticatory muscle activity (MMA), self-reported oral behaviours (OBs) and overall physical activity (PA) in adult women. MATERIALS AND METHODS: MMA and PA were assessed by a wearable electromyography (EMG) device and accelerometer respectively, worn over 2 non-consecutive days by 53 women (mean age 27.5 ± 6.4 years). Following the second recording day, self-reported OBs were assessed. MMA was assessed by the number, amplitude and duration of masseter contraction episodes. Masseter muscle EMG outcome measures were number of contraction episodes per hour (CEs/h) and the relative contraction time (RCT%). PA was assessed by time accumulated in moderate to vigorous physical activity (MVPA) and 10-min bouts of MVPA per hour. Data were analysed using mixed model analysis. RESULTS: MMA in free-living conditions consisted mostly of low-amplitude (<10% maximum voluntary clenching) and short-duration (<10 s) contraction episodes. Masseter CEs/h were not associated with self-reported levels of OB. Masseter CEs/h were positively associated with time accumulated in MVPA (F = 9.9; p = 0.002) and negatively associated with 10-min bouts of MVPA/h (F = 15.8; p <0.001). RCT% was not significantly associated with either. CONCLUSIONS: Objectively assessed MMA is not associated with self-reported OB in free-moving adult females. Moderate to vigorous exercise and physical inactivity are accompanied with an increase in the number of masseter muscle contractions and thus possibly tooth clenching activity. CLINICAL RELEVANCE: OB can be influenced by the type and extent of PA. Subjective assessment of MMA by questionnaire and/or interviews may be invalid.

Occlusal tactile acuity in temporomandibular disorder pain patients: A case-control study.

OBJECTIVE: To compare the smallest thickness that can be perceived between occluding teeth (occlusal tactile acuity, OTA) of temporomandibular disorder pain (TMD-P) patients with that of control (CTR) individuals. METHODS: Twenty TMD-P patients (17 women and 3 men, mean age: 31.3 ± 10.4 years) diagnosed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol and 20 age- and gender-matched controls (17 women and 3 men, mean age: 31.4 ± 10.5 years) were enrolled. The OTA was tested with 10 different thicknesses: 9 aluminium foils (8 µm-72 µm with a constant increment of 8 µm) and 1 sham test (without foil), each thickness being tested 10 times in random order (100 tests in total). The participants were instructed to close their mouth once and to report whether they felt the foil between their molar teeth. A between-group comparison (TMD-P vs CTR) was performed for each testing thickness (analysis of variance for repeated measurements, with Bonferroni multiple correction) (P < .005). RESULTS: Significantly increased OTA was observed in the TMD-P group for the thicknesses between 8 µm and 40 µm, while no significant differences were found for the sham test and for the larger thicknesses tested (from 48 µm to 72 µm). CONCLUSIONS: TMD-pain subjects presented an increased OTA as compared to controls.

Smartphone-assisted monitoring of masticatory muscle activity in freely moving individuals.

OBJECTIVES: To test a smartphone-assisted wireless device for assessing electromyographic (EMG) activity of the masseter muscle in freely moving individuals undertaking routine activities. MATERIALS AND METHODS: EMG activity was detected unilaterally from the masseter muscle in 12 volunteers using surface electrodes connected to both a smartphone-assisted wireless EMG device and a fixed-wired EMG equipment (reference standard). After performing a series of standardized tasks in the laboratory, participants wore the wireless device for 8 h while performing their normal routine. RESULTS: The wireless device reliably detected masseter muscle contraction episodes under both laboratory and natural environment conditions. The intraclass correlation coefficients for the muscle contraction episode amplitude and duration detected by the wireless and the wired equipment ranged from 0.94-1.00 to 0.82-1.00, respectively. Most masseter contraction episodes during normal routine were of low amplitude (< 10% MVC) and short duration (< 10 s), with no significant differences between sexes or facial side. CONCLUSIONS: Within the limitations of the study, smartphone-assisted monitoring of the jaw muscles represents a promising tool to investigate oral behavior patterns in free moving individuals. CLINICAL RELEVANCE: Smartphone-assisted monitoring of masticatory muscle activity may enable possible associations between excessive muscle activity, bruxism, dysfunction, and pain to be investigated, and managed via biofeedback.

"Closed Reduction" Principles Can Manage Diverse Conditions of Temporomandibular Joint Vertical Height Loss: From Displaced Condylar Fractures to Idiopathic Condylar Resorption.

PURPOSE: The aim of this case series was to describe a modification of the classic "closed reduction" technique to manage unilateral or anterior open bite owing to a loss in vertical height (LVH) caused by several disorders and pathologies other than displaced condylar fractures. MATERIALS AND METHODS: The protocol included insertion of an occlusal appliance to increase the height of the premature contact and the width of the open bite, stabilization of the dental arches by rigid arches, and the use, during sleep, of rubber bands in the open bite region to pull the mandible cranially. In addition, when awake, the patient performed physiotherapy exercises to guide the mandible into maximum intercuspation. The increased open bite enhanced the effect of the rubber bands in guiding the mandible into the original habitual occlusion and the rigid arches served to minimize tooth eruption. RESULTS: The present cases showed the favorable outcome of this low-risk treatment in the re-establishment of the original habitual occlusion within 1 to 4 weeks and without reconstruction of the LVH. CONCLUSION: The efficacy of this complication-free approach to correct occlusion in various conditions of LVH suggests that this protocol should be applied before venturing into surgical intervention.

Short-Term Sensorimotor Effects of Experimental Occlusal Interferences on the Wake-Time Masseter Muscle Activity of Females with Masticatory Muscle Pain.

AIMS: To investigate the effects of the application of an acute alteration of the occlusion (ie, interference) on the habitual masseter electromyographic (EMG) activity of females with temporomandibular disorders (TMD)-related muscular pain during wakefulness. METHODS: Seven female volunteers with masticatory myofascial pain participated in a crossover randomized clinical trial. Gold foils were glued on an occlusal contact area (active occlusal interference, AI) or on the vestibular surface of the same molar (dummy interference, DI) and left for 8 days. The masseter electromyogram was recorded during wakefulness in the natural environment by portable recorders under interference-free, dummy-interference, and active-interference conditions. The number, amplitude, and duration of EMG signal fractions with amplitudes above 10% of the maximum voluntary contraction (activity periods, APs) were computed in all experimental conditions. Muscle pain, headache, and perceived stress were each assessed with a visual analog scale (VAS), and an algometer was used to assess masseter and temporalis pressure pain thresholds. Data were analyzed by means of analysis of variance. RESULTS: The frequency and duration of the recorded APs did not differ significantly between the experimental conditions (P>.05), but a small and significant reduction of the EMG mean amplitude of the APs occurred with AI (P<.05). Neither the VAS scores for muscular pain, headache, and perceived stress nor the pressure pain thresholds changed significantly throughout the entire experiment (P>.05). CONCLUSION: An active occlusal interference in female volunteers with masticatory muscle pain had little influence on the masseter EMG activity pattern during wakefulness and did not affect the pressure tenderness of the masseter and temporalis.

Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) for Clinical and Research Applications: recommendations of the International RDC/TMD Consortium Network* and Orofacial Pain Special Interest Group†.

AIMS: The original Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I diagnostic algorithms have been demonstrated to be reliable. However, the Validation Project determined that the RDC/TMD Axis I validity was below the target sensitivity of ≥ 0.70 and specificity of ≥ 0.95. Consequently, these empirical results supported the development of revised RDC/TMD Axis I diagnostic algorithms that were subsequently demonstrated to be valid for the most common pain-related TMD and for one temporomandibular joint (TMJ) intra-articular disorder. The original RDC/TMD Axis II instruments were shown to be both reliable and valid. Working from these findings and revisions, two international consensus workshops were convened, from which recommendations were obtained for the finalization of new Axis I diagnostic algorithms and new Axis II instruments. METHODS: Through a series of workshops and symposia, a panel of clinical and basic science pain experts modified the revised RDC/TMD Axis I algorithms by using comprehensive searches of published TMD diagnostic literature followed by review and consensus via a formal structured process. The panel's recommendations for further revision of the Axis I diagnostic algorithms were assessed for validity by using the Validation Project's data set, and for reliability by using newly collected data from the ongoing TMJ Impact Project-the follow-up study to the Validation Project. New Axis II instruments were identified through a comprehensive search of the literature providing valid instruments that, relative to the RDC/TMD, are shorter in length, are available in the public domain, and currently are being used in medical settings. RESULTS: The newly recommended Diagnostic Criteria for TMD (DC/TMD) Axis I protocol includes both a valid screener for detecting any pain-related TMD as well as valid diagnostic criteria for differentiating the most common pain-related TMD (sensitivity ≥ 0.86, specificity ≥ 0.98) and for one intra-articular disorder (sensitivity of 0.80 and specificity of 0.97). Diagnostic criteria for other common intra-articular disorders lack adequate validity for clinical diagnoses but can be used for screening purposes. Inter-examiner reliability for the clinical assessment associated with the validated DC/TMD criteria for pain-related TMD is excellent (kappa ≥ 0.85). Finally, a comprehensive classification system that includes both the common and less common TMD is also presented. The Axis II protocol retains selected original RDC/TMD screening instruments augmented with new instruments to assess jaw function as well as behavioral and additional psychosocial factors. The Axis II protocol is divided into screening and comprehensive self report instrument sets. The screening instruments' 41 questions assess pain intensity, pain-related disability, psychological distress, jaw functional limitations, and parafunctional behaviors, and a pain drawing is used to assess locations of pain. The comprehensive instruments, composed of 81 questions, assess in further detail jaw functional limitations and psychological distress as well as additional constructs of anxiety and presence of comorbid pain conditions. CONCLUSION: The recommended evidence-based new DC/TMD protocol is appropriate for use in both clinical and research settings. More comprehensive instruments augment short and simple screening instruments for Axis I and Axis II. These validated instruments allow for identification of patients with a range of simple to complex TMD presentations.

Complete ossification of the stylohyoid chain as cause of Eagle's syndrome: a very rare case report.

AIM: To report on a patient with Eagle's syndrome with a complete and very large ossification of the stylohyoid complex on the right side that to our best knowledge has never been published previously. BACKGROUND: Eagle's syndrome is characterized by a set of symptoms that are caused by the irritation of the neurovascular and soft-tissues caused by an elongated styloid process or ossification of stylohyoid ligament. CASE DESCRIPTION: Because of the high discomfort and pain degree as well as limitations of mandibular and head mobility and also the thickness of the ossifed stylohyoid chain, the patient was treated surgically by removing the hypertrophic segment. CONCLUSION: These symptoms subsided completely after the surgical excision of the anomaly. The elongated styloid process on the left side was symptom free. CLINICAL SIGNIFICANCE: Eagle's syndrome symptoms are not specific and can mimic those of other disorders, the syndrome must be included in the differential diagnosis of patients with pain in the orofacial, pharyngeal and cervical area.

Nocturnal masseter electromyographic activity of complete denture wearers.

OBJECTIVE: Collection of normative data on activity patterns of the masseter during sleep in elderly denture wearers by portable electromyography (EMG) recorders. BACKGROUND: Complete denture wearers might suffer from orofacial pain caused by myoarthropathies of the masticatory system. Indeed, denture instability may precipitate parafunctional habits and consequently muscle soreness and/or temporomandibular pain. MATERIALS AND METHODS: We collected normative masseter EMG data during sleep in 15 complete denture wearers (five women, 10 men, 56-88 years) by portable recorders in their natural environment. Activity periods (AP) were signal portions including subthreshold intervals ≤5 s. Signal amplitude was expressed in per cent of maximum voluntary contraction (%MVC). For this reason, maximum bite force was assessed. Twenty age-matched dentate controls were also recorded for the maximum bite force. RESULTS: We found 157.2 ± 86.5 AP per night, i.e. 24.0 ± 12.2 AP/h. Mean amplitude was 15.1 ± 4.3%MVC. AP lasted 6.8 ± 4.1 s, and their time integral was 126.3 ± 112.5%MVC•s. Maximum bite force was 116.8 ± 69.6 N in the edentulous, significantly lower than in controls (344.8 ± 150.4 N). CONCLUSIONS: Healthy complete denture wearers showed intermittent periods of nocturnal masseter activity of very low intensity and short duration.

Macroscopic analysis of human masseter compartments assessed by magnetic resonance imaging.

The human masseter is divided into compartments by aponeuroses. So far, the qualitative and quantitative features of these compartments and their aponeuroses have been scarcely investigated. This study investigated the three-dimensional compartmentalization of the masseter muscle and tested the hypothesis that aponeurosis content varies systematically across different masseter subportions as well as between genders. The right masseter of 14 healthy participants was scanned by magnetic resonance, and the outlines of muscle and aponeuroses were segmented and rendered in three dimensions by AMIRA software. The internal architecture of the masseter muscle varied markedly across individuals, with respect to the number, shape and location of the compartments delimited by aponeuroses. Aponeuroses were widely represented inside the masseter, amounting to 7.1 ± 2.1% of its volume. The aponeurosis content varied systematically across masseter subvolumes and did not differ between genders after adjusting for body height and weight.

Implant-supported mandibular splinting affects temporomandibular joint biomechanics.

OBJECTIVES: Mandibular functional movements lead to complex deformations of bony structures. The aim of this study was to test whether mandibular splinting influences condylar kinematics and temporomandibular joint (TMJ) loading patterns. MATERIALS AND METHODS: Six subjects were analyzed by means of dynamic stereometry during jaw opening-closing with mandibles unconstrained as well as splinted transversally by a cast metal bar fixed bilaterally to two implant pairs in the (pre)molar region. Statistical analysis was performed by means of ANOVAs for repeated measurements (significance level α=0.05). RESULTS: Transversal splinting reduced mandibular deformation during jaw opening-closing as measured between two implants in the (pre)molar region on each side of the mandible significantly by 54%. Furthermore, splinting significantly reduced the distance between lateral condylar poles (average displacement vector magnitude of each pole: 0.84±0.36 mm; average mediolateral displacement component: 45±28% of the magnitude) and led to a medial displacement of their trajectories as well as a mediolateral displacement of stress-field paths. CONCLUSIONS: During jaw opening-closing, splinting of the mandible leads to a significant reduction of mandibular deformation and intercondylar distance and to altered stress-field paths, resulting in changed loading patterns of the TMJ structures.

Taking Sides with Pain - Lateralization aspects Related to Cerebral Processing of Dental Pain.

The current fMRI study investigated cortical processing of electrically induced painful tooth stimulation of both maxillary canines and central incisors in 21 healthy, right-handed volunteers. A constant current, 150% above tooth specific pain perception thresholds was applied and corresponding online ratings of perceived pain intensity were recorded with a computerized visual analog scale during fMRI measurements. Lateralization of cortical activations was investigated by a region of interest analysis. A wide cortical network distributed over several areas, typically described as the pain or nociceptive matrix, was activated on a conservative significance level. Distinct lateralization patterns of analyzed structures allow functional classification of the dental pain processing system. Namely, certain parts are activated independent of the stimulation site, and hence are interpreted to reflect cognitive emotional aspects. Other parts represent somatotopic processing and therefore reflect discriminative perceptive analysis. Of particular interest is the observed amygdala activity depending on the stimulated tooth that might indicate a role in somatotopic encoding.

Do illness perceptions predict pain-related disability and mood in chronic orofacial pain patients? A 6-month follow-up study.

UNLABELLED: In our study, we investigated the predictive value of illness beliefs as measured by the revised illness perception questionnaire (IPQ-R) in the context of other clinical predictors in patients with chronic orofacial pain over a 6-month follow-up period. Consecutive patients (152) referred to the interdisciplinary orofacial pain service at the Centre for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich received questionnaires to assess pain and pain-related disability, anxiety, depression as well as physical and mental quality of life at three time points: prior to treatment, 3 and 6 months after beginning of treatment. RESULTS: significant improvement was found over time for all outcome measures except mental quality of life. RESULTS of the regression analysis indicated that believing pain could have serious consequences on one's life (IPQ subscale consequences) is one of the most important predictors for treatment outcome. The belief in low personal control and in a chronic timeline is also shown to be predictive for outcome, though explaining a smaller proportion of variance. These results provided evidence that beliefs about pain are important predictors for treatment outcome even when controlled for pain and mood. They therefore need to be considered in the management of patients with chronic orofacial pain. Assessing patients' illness beliefs can provide essential information on these important psychological determinants of adjustment to chronic pain and may be specific targets for individualised treatment approaches.