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.

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.

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.

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.

Temporomandibular joint loading patterns related to joint morphology: a theoretical study.

It is unclear which aspects of the temporomandibular joint (TMJ) anatomy and/or kinematics determine shape and location of disk-compressive areas (stress field). The aim of this study was a quantitative analysis of TMJ anatomy to predict stress field path direction. Twenty-five asymptomatic TMJs (12 females and 13 males, aged 20-38 years) were tracked during unloaded opening/closing cycles. All TMJs were magnetic resonance (MR) imaged, reconstructed and animated with the recorded kinematics. Quantitative morphological parameters were calculated and entered into cross-validated multivariate discriminant analysis. Stress field paths during jaw opening were classified as mediolateral (ML) in 14 (9 females and 5 males) and lateromedial (LM) in 11 joints (3 females and 8 males). Curvature and incongruence as well as the dorsoventral position of the condyle in the fossa showed statistically significant differences (Mann-Whitney U test, p < 0.05). A combination of the lateral incongruence, the distance from the posterior slope of the eminence as well as the maximum posterior sagittal curvature enabled to correctly predict the direction of stress field paths in 92% of cases. In particular, ML type joints had laterally more congruent condyles/fossae and condyles more distant from the posterior slope of the eminence than LM type joints. Within the limits of this study, TMJ morphology seems to determine stress field path patterns.

From movement to models: a tribute to professor Alan G. Hannam.

This tribute article to Professor Alan G. Hannam is based on 7 presentations for him at the July 1, 2008 symposium honoring 3 "giants" in orofacial neuroscience: Professors B. J. Sessle, J. P. Lund, and A. G. Hannam. This tribute to Hannam's outstanding career draws examples from his 40-year academic career and spans topics from human evolution to complex modeling of the craniomandibular system. The first presentation by W. Hylander provides a plausible answer to the functional and evolutionary significance of canine reduction in hominins. The second presentation, by A. McMillan, describes research activities in the field of healthy aging, including findings that intensity-modulated radiotherapy improves the health condition and quality of life of people with nasopharyngeal carcinoma in comparison to conventional radiotherapy. The developments in dental imaging are summarized in the third paper by E. Lam, and an overview of the bite force magnitude and direction while clenching is described in the fourth paper by M. Watanabe. The last 3 contributions by G. Langenbach, I. Staveness, and C. Peck deal with the topic of bone remodeling as well as masticatory system modeling, which was Hannam's main research interest in recent years. These contributions show the considerable advancements that have been made in the last decade under Hannam's drive, in particular the development of an interactive model comprising, in addition to the masticatory system, also the upper airways. The final section of the article includes a final commentary from Professor Hannam.

Nonfunctional tooth contact in healthy controls and patients with myogenous facial pain.

AIMS: To investigate how often healthy controls and patients with myogenous masticatory pain have wake-time nonfunctional tooth contact, whether the frequency of nonfunctional tooth contact differs between genders or between weekdays and weekends, and whether it is influenced by stress levels. METHODS: The study was performed on 24 subjects: 15 controls and 9 patients with myogenous facial pain. Before data collection the subjects were trained to ascertain their ability to feel correctly whether their teeth were in contact or apart. Subsequently, for 10 days the subjects were alerted by means of a radio wave-activated wrist vibrator approximately every 20 minutes (8:00 AM to 10:00 PM) in order to report whether the teeth were in contact. Subjects also completed 2 stress assessment questionnaires, the Perceived Stress Scale (PSS) and the short version of the Trier Inventory for Assessment of Chronic Stress (TICS-S). RESULTS: There was a significantly higher frequency of wake-time nonfunctional tooth contact in myogenous pain patients than in controls (median of 34.9% and range of 26.5% to 41.3% for patients; median of 8.9% and range of 2.3% to 14.3% for controls; P < .001). In both groups the frequency of nonfunctional tooth contact did not significantly differ among the various days or between the genders. The patients had significantly higher PSS scores and reported having experienced more stressful situations in the dimensions "social overload" and "overextended at work" than the controls. However, PSS and TICS-S scores were not correlated with the frequency of nonfunctional tooth contact for either group. CONCLUSIONS: Myogenous pain patients had nearly 4 times more nonfunctional tooth contact during wake time than controls.

[The Interdiscipilinary Orofacial Pain Consulting Service at the Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery, University of Zurich, Switzerland]. / Die "interdisziplinäre Schmerzsprechstunde" am Zentrum für Zahn-, Mund- und Kieferheilkunde (ZZMK) in Zürich.

At the Center for Dental and Oral Medicine and Cranio-Maxillofacial Surgery of the University of Zurich, a new interdisciplinary pain consulting service was established in early 2005 due to the increasing number of referrals of orofacial pain patients to the center. This unit comprises specialists of various dental and medical disciplines as well as psychologists and physical therapists. This article highlights the most common clinical pictures of chronic orofacial pain patients and describes the organizational mechanisms associated with referrals to our interdisciplinary pain service.

[Composite resin copings for a perio-overdenture. A newly developed method of making copings for retention with spherical elements]. / Coiffes radiculaires en résine composite dans le cadre de la perio-overdenture. Une nouvelle évolution avec la réalisation de coiffes supraradiculaires en résine composite associées à des ancrages sphériques.

Today's dentistry should aim at minimizing cost, simplifying techniques, allowing procedural revi sions and finally at facilitating corrections and repairs. The development of direct or indirect light-cured composite resin copings, coupled with ball attachments (Dalbo-Rotex according to Brunner) and a suprastructure which is veneered by means of light-cured composite or acrylic resin, may offer a cost-effective perio-overdenture without compromising on periodontal health and providing optimal esthetics. Since July 2003, eighteen new perio-overdentures with a total of 70 copings made of light-cured microhybrid composite resin were delivered. The aim of this article is to discuss the technical aspects and preliminary results regarding this technique.

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.

Biphasic finite element simulation of the TMJ disc from in vivo kinematic and geometric measurements.

Understanding the biomechanical nature of the degeneration of the temporomandibular joint requires a coupling between experimental measurements and numerical simulation. In this study, geometry measured from MRI, and motion obtained from a specially designed optoelectronic system are fed into a three-dimensional biphasic finite element analysis to generate the spatial and temporal mechanical response of the disc. This study demonstrates how this coupling can effectively predict the biomechanical response of the temporomandibular joint disc to physiological loading. For small jaw opening movements, asymmetries in the load of the disc are found, with especially higher shear stresses in the lateral portion.

The mediolateral temporomandibular joint disc position: an in vivo quantitative study.

AIMS: Temporomandibular joint (TMJ) discs displaced simultaneously, dorsoventrally, and mediolaterally are assumed to be rotated. However, a pilot study performed with individualized oblique-axial scans on supposedly rotated discs did not show disc rotation consistently. The aim of this study was the quantitative evaluation of disc rotation on a larger sample size, assessing the mediolateral disc geometry and position by the use of a reference system determined by the condylar long axis. METHODS: Eighty-five TMJs from 50 subjects were analyzed. One series of sagittal and 1 of 14 individualized oblique-axial magnetic resonance (MR) scans were taken for each joint. The dorsoventral disc position was diagnosed by means of the sagittal scans. The mediolateral disc width and position were then measured on every oblique-axial scan. The width and midline was computed for each disc and its deviation from the perpendicular to the condylar long axis was calculated. Finally, a statistical analysis was performed to study whether the disc width and the direction of the disc midline varied between discs normally positioned and anteriorly displaced. RESULTS: The disc width varied significantly more within the anteriorly displaced discs than within the normal ones. The midline of the anteriorly displaced discs deviated more from the perpendicular to the condylar long axis than that of normally positioned discs and was mostly in a lateral direction. The disc midline also deviated more in the ventral than in the dorsal part of the disc. CONCLUSION: Most anteriorly displaced discs were laterally displaced and showed a larger width variation than normally positioned discs. This fact seems to indicate disc deformation.