Maximal Voluntary Clenching Research Articles

Prediction of Ergogenic Mouthguard Effects in Volleyball: A Pilot Trial.

Dental occlusion may affect static and dynamic balance. The effects of a mouthguard on pinpoint accuracy in volleyball were investigated in 28 players who completed a volleyball specific test. Also, masticatory electromyographic tests were performed. The mean pinpoint accuracy was significantly higher with a mouthguard (68.6±9.3 vs. 64.0±7.0 points from 100; p< 0.006). However, differential mouthguard effects were seen, and three subgroups were classified: Group 1 (markedly improved pinpoint accuracy), Group 2 (improved pinpoint accuracy), and Group 3 (reduced pinpoint accuracy). Group 1 had a high masseter resting tone, the masseter activity was low in MVC (maximum voluntary clench) and increased in BOC (maximum bite on cotton rolls; p< 0.04). This indicates a masseter weakness, which would be compensated by a mouthguard. In Group 2, the masseter activity in MVC was high-normal with an imbalance which was improved in BOC (p< 0.01), indicating a possible mouthguard benefit. In Group 3, MVC and BOC were in a high-normal range and showed no relevant deficits. In these subjects the mouthguard had adverse effects. Overall, subjects with masticatory deficits had a benefit from the mouthguard in pinpoint accuracy. Positive or negative mouthguard responders may be detectible from electromyographic tests.

Evaluation of tissue oxygen saturation of the masseter muscle during standardised teeth clenching.

Haemodynamics during recovery after teeth clenching is poorly understood. To clarify factors influencing tissue blood oxygenation recovery after clenching with altered muscle activity and duration, but constant total muscle activity. The following tasks were based on constant maximum voluntary clenching (100% MVC): (a) 50% MVC×30seconds; (b) 30% MVC×50seconds; and (c) 10% MVC×150seconds. Tissue oxygenated (oxy-Hb), deoxygenated (deoxy-Hb) and total haemoglobin (total-Hb) were recorded using near-infrared spectroscopy in the masseter muscle during recovery after each task. Participants rested for 30seconds before each task; average resting values were set as baseline. Respective ratios to baseline at 20, 60, 120 and 180seconds after each task were calculated; the tasks were compared at each time point using one-way repeated-measures ANOVA. Oxy-Hb and total-Hb decreased and deoxy-Hb increased during the tasks and recovered thereafter. For Task 3, not all values recovered to baseline, even after 180seconds (oxy-Hb: 96.85%, total-Hb: 98.31%, deoxy-Hb: 102.98%). Oxy-Hb (after 180seconds, Task 1-Task 3: P<.001, Task 2-Task 3: P=.013) and total-Hb (after 180seconds, Task 1-Task 3: P<.001, Task 2-Task 3: P=.005) were significantly lower, and deoxy-Hb (after 180seconds, Task 1-Task 3: P<.001, Task 2-Task 3: P=.005) was significantly higher for Task 3 than other tasks, at all times during and after recovery. Despite the same total muscle activity, weak-force, long-duration clenching is more harmful than strong-force, short-duration clenching, suggesting a greater effect of awakening bruxism than sleep bruxism on myalgia.

Application of digital mandibular movement record and masticatory muscle electromyography in the evaluation of stomatognathic function in patients with mandibular tumor

To study the clinical characteristics of mandibular movement and masticatory muscle function in preoperative and postoperative patients with unilateral mandibular tumors in the region of mandibular body and ramus by combining digital mandibular movement records with electromyography, and to preliminarily explore the relationship and mechanism between movement and masticatory muscle function. Six preoperative patients with tumor in unilateral body and ramus of mandible were included, and three postoperative patients with unilateral segmental resection and reconstruction of mandibular bone were included. The mandibular movement recording system and surface electromyography system were used to collect the movement trajectory of the patients' mandibular marginal movement and chewing movement, and the surface electromyography of bilateral masseter and temporalis was recorded concurrently. The surface electromyography of bilateral masseter and temporalis was collected when the patients were at relaxation and at maximal voluntary clenching (MVC). The motion trajectory was observed on the digital virtual model, and the motion amplitude and direction of mandibular marginal movements were analyzed. The characteristics of masticatory electromyogram (EMG) activity in affected and unaffected sides at relaxation, MVC and bilateral mastication were analyzed, and the asymmetry indexes and activity indexes were calculated. The preoperative mean maximum opening of the patients was (35.20±6.87) mm. Three patients had mild mouth opening limitation, and all the patients' mouth opening trajectory was skewed to the affected side. During lateral movements, the mean range of motion of the affected side [(10.34±1.27) mm] and that of the healthy side [(6.94±2.41) mm] were significantly different. The maximum opening of the postoperative patients was (30.65±17.32) mm, and the mandibular marginal movement characteristics were consistent with those of the patients before surgery. During MVC in the preoperative patients, the median EMG activities of the masseter muscle [44.20 (5.70, 197.90) μV] and the temporalis muscle [42.15 (22.90, 155.00) μV] on the affected side were slightly lower than those of the masseter [45.60 (7.50, 235.40) μV] and the temporalis muscle [63.30 (44.10, 126.70) μV] on the healthy side. In the postoperative patients, individualized changes occurred. Some patients suffered from weakened electromyographic activity on the affected side, while some other ones showed hyperelectromyographic activity on the affected side. Both benign and malignant tumors as well as their surgery can cause abnormal mandibular movements and change of electromyographic activity of bilateral masseter and temporalis muscles.

Effect of jaw functional status on neck muscle endurance

ObjectiveTo investigate the effect of resting jaw and maximum voluntary clenching on neck flexor and extensor muscle endurance. DesignNeck flexor and extensor endurance was measured in a college health clinic in 85 male college students in two test positions: resting jaw (control) and maximum voluntary clenching. ResultsMean neck flexor muscle endurance values during resting jaw and maximum voluntary clenching were 70.06 SD 28.24, and 60.03 SD 16.5, seconds respectively. Mean neck extensor muscle endurance values during resting jaw and maximum voluntary clenching were 105.54 SD 29.9, and 98.32 SD 24.54, respectively. Both values were significantly lower while maximum voluntary clenching as compared to resting jaw position (p < 0.05). ConclusionModification of jaw position can affect neck muscle endurance. Results of this study further supports sensory-motor relation between jaw and neck region.

EMG-CHARACTERISTIC OF MASTICATORY MUSCLES IN PATIENTS WITH CLASS II MALOCCLUSION AND TEMPOROMANDIBULAR DISORDERS

Introduction: A stable state of musculoskeletal system is provided by harmony of occlusion, the anatomy of temporomandibular joints, and the activity of the masticatory muscles under the control of peripheral and central nervous system. Surface electromyography (EMG) is a well-used modality and is used in dentistry to access the status of the muscles of mastication. The aim of the research was to evaluate the EMG-characteristic of masticatory muscles in patients with TMD and Angle Class II malocclusion. Materials and methods: The study comprised 23 patients with Angle Class II malocclusion and TMD. The average age of the subjects was 26,5 ± 2,3 years. Malocclusion was evaluated according to Angle classification, TMD - according to the Research Diagnostic Criteria (RDC/TMD). Registration of EMG-activity of masseter and anterior temporalis muscles was performed during maximum voluntary clenching, clenching on the right and left sides. Results: EMG-activity of masticatory muscles are characterized by: 1) increased values of EMG-activity of temporal and masseter muscles - peak and average amplitude in tests of unilateral clenching and maximum clenching (values are greater than 2000 μV); 2) in unilateral clenching of jaws (on the left or right) the increased EMG-activity was detected on the balancing side; 3) in unilateral clenching of jaws (on the left or right) the increased muscle activity on the working side with disproportional (asymmetric) load distribution between masseter and temporal muscles has been found. Conclusions: Patients with Angle Class II malocclusion and TMD were found features of EMG-activity of masticatory muscles.

Indexes of jaw muscle function in asymptomatic individuals with different occlusal features.

This study aims to assess the correlation between indexes of jaw muscle function and dento‐skeletal morphology. A sample of 35 temporomandibular disorders‐free healthy individuals (10 males, mean age 26.7 ± 9.8 years) underwent surface electromyographic (sEMG) assessment of bilateral masseter and temporalis muscles, to evaluate sEMG activity during maximum voluntary clenching (MVC) with a dedicated device (Easymyo®, T.F.R. Technology, Udine, Italy). Four outcome parameters were assessed for each individual: MCV on cotton rolls; MVC on teeth; chewing on right and left sides; clench/relax test. Electromyographic recordings were assessed based on five standardized indexes of muscle function, to evaluate the degree of muscle asymmetry during static and dynamic function (i.e., percentage overlapping coefficient [POC], Impact, Asymmetry, Activation, and Torque). For each individual, the presence of a number of occlusal and skeletal features was assessed: asymmetry of molar class; deviated incisor midline; deep bite; open bite; and crossbite. Skeletal class and vertical dimension of occlusion were also evaluated. Based on normality distribution of data, t test and analysis of variance, when needed, were used to compare muscle function indexes between individuals with and without the different dento‐skeletal features. None of the muscle function indexes (POC, Impact, Asymmetry, Activation, and Torque) was significantly different between individuals with or without the various dental and skeletal features. Gender differences were also not significant (p > 0.05). Despite some minor differences were observed, none of them was significant. Thus, the interaction between form and function is too complex for hypothesizing a simple one‐to‐one relationship between interarch tooth relationship and muscle function patterns.

Association Between Contact from an Overerupted Third Molar and Bilaterally Redistributed Electromyographic Activity of the Jaw Closing Muscles

To determine whether the facial side of an overerupted third molar and/or the side exhibiting symptoms of temporomandibular disorders (TMD) has an association with the bilateral distribution of occlusal contact number, occlusal force, or surface electromyographic (SEMG) activity of the anterior temporalis (TA) and masseter muscles. Nineteen patients with unilateral TMD symptoms and one overerupted mandibular third molar were enrolled. Occlusal contacts and the SEMG activity of the anterior temporalis and masseter muscles were recorded simultaneously during maximal voluntary clenching (MVC) in the intercuspal position (ICP-MVC) and in the protrusive edge-to-edge position (Pro-MVC). The associations between the side of overeruption/TMD symptoms and the Δvalues of the differences between the right- and left-side values for the number of occlusal contacts, sectional force value (defined as the ratio of the anterior or posterior sectional arch bite force of the right or left side to the total arch force [SFV]), and SEMG activity of the temporalis and masseter muscles were analyzed. The overeruption side (P < .050), but not the symptomatic side (P > .050), showed an association with the Δvalues, with higher SFVs of the posterior arch and lower values for temporalis SEMG activity in the 100%, 75%, and 50% protrusive clenching positions and larger numbers of occlusal contacts in the posterior arch in the 100% and 75% protrusive clenching positions than the non-overeruption side. The pattern of occlusion, but not TMD symptoms, had an association with the number and distribution of the occlusal contacts, occlusal force, and temporalis SEMG activity.

Evaluation of masticatory muscle activity in patients with unilateral posterior crossbite before and after rapid maxillary expansion.

The relationship between unilateral posterior crossbite (UPCB) and the possible asymmetric activation of the jaw muscles in children is still under debate. This study aimed at evaluating the jaw muscle activity of children with UPCB before and after rapid maxillary expansion (RME) by means of surface electromyography and a standardized sampling protocol. Twenty-nine children with UPCB (UPCB-group, mean age 9.6 ± 1.6 years) and 40 UPCB-free controls (Control-group, 10.5 ± 1.1) were recruited. The activity of the left and right anterior temporalis (AT) and superficial masseter muscles (MM) was recorded during maximum voluntary clenching and a chewing task (T0). In the UPCB-group, data were collected, also, after the correction of the UPCB with RME (T1) and 6 months later (T2), without any further treatment. Electromyographic indices comparing the activity of paired muscle were computed via software to estimate the extent of asymmetric AT and MM activity. Paired and unpaired t-test or Wilcoxon-signed rank and Mann-Whitney U test, ANOVA or Friedman test and chi-squared test were used in the statistical analysis. Both groups presented with asymmetric activity of the muscles, which did not differ between groups (T0, all P > 0.05). The treatment determined a decrease in muscular activity (T1, P = 0.040), and a more asymmetric pattern of muscle activation during chewing (T1, P = 0.040), which returned similar to baseline values at T2 (all P > 0.05). UPCB does not contribute to an asymmetric activation of AT and MM during functional tasks. The treatment of UPCB by RME did not determine a more symmetric activity of the assessed muscles.

Relationship between severity of periodontitis and masseter muscle activity during waking and sleeping hours

ObjectiveThis study was conducted to investigate whether the masseter muscle activity shows any specific pattern in relation to the severity of periodontitis. DesignSixteen subjects with no or mild periodontitis (NMP group) and 15 subjects with moderate or severe periodontitis (MSP group) were enrolled. Plasma IgG antibody titer was examined using Porphyromonas gingivalis as a bacterial antigen. Surface electromyography (EMG) of the masseter muscles was continuously recorded using an ambulatory surface EMG recording device while patients were awake and asleep. Masseter muscle activity was analyzed using intensities of 5%–10% maximal voluntary clenching (MVC), 10%–20% MVC, and >20% MVC. Furthermore, EMG levels of 20% MVC were adopted as the threshold for analysis of phasic, tonic, and mixed EMG activities. The cumulative duration of masseter muscle activity and bruxism episodes was calculated as duration per hour. ResultsThere was no significant difference in plasma IgG antibody titers against P. gingivalis between the NMP and MSP groups (p = 0.423). During waking hours, the duration of masseter muscle activity with an intensity of >20% MVC was significantly longer in the MSP group than in the NMP group (p = 0.037). During sleeping hours, the duration of masseter muscle activity at all MVC intensities was significantly longer in the MSP group than in the NMP group (all p < 0.05). Additionally, the duration of phasic and mixed episodes was significantly longer in the MSP group than those in the NMP group while both awake and asleep (all p < 0.05). ConclusionsThe results of this study suggested that masseter muscle activity might be related to the severity of periodontitis.

Electromyographic activity changes of jaw-closing muscles in patients with different occlusion schemes after fixed prosthetic restoration

Background/Aim: To investigate the electromyographic (EMG) activity changes of jaw-closing muscles in patients with different occlusion schemes and posterior edentulous span, after the placement of teethsupported fixed partial denture (FPD). Material and Methods: The study sample consisted of 20 patients (10 men and 10 women, the mean age being 50 years) with a posterior edentulous area that includes two missing premolars or one premolar and one molar. The participants were divided into two groups with different occlusion schemes: canine-guided occlusion (CGO) and group function occlusion (GFO). The metal-ceramic FPD were fabricated according to the clinic-standardized protocol. EMG activities of masseter and anterior temporalis patients' muscles were recorded with bipolar surface electrodes during maximal voluntary clenching. EMG evaluation was repeated twice: (T1) before the fabrication of FPD (T2) after eight weeks of FPD cementation and intraoral functioning of restoration. The data were subjected to Analysis of Variance-ANOVA within the methodological framework of the General Linear Models with Repeated Measures. The Bonferroni test was used to compare multiple mean measures. Statistical analysis was conducted with SPSS ver. 11.5. The level of significance was predefined at a=0.05. Results: Group 1 with CGO presented significantly higher levels of masseter (mean maximum EMG average before 79.36μV and 139.68μV after) and temporalis (mean maximum EMG average before 79.07μV and 149.37μV after) EMG activity after FPD placement. Group 2 with GFO also showed significantly higher levels of masseter (mean maximum EMG average before 61.57μV and 165.30μV after) and temporalis (mean maximum EMG average before 56.94μV and 133.08μV after) EMG activity after the prosthetic restoration. Conclusions: It may be concluded that fixed prosthetic restoration, in both patients with canine-guided and group function occlusion, results in increased EMG jaw-muscle activity.

Properties of tonic episodes of masseter muscle activity during waking hours and sleep in subjects with and without history of orofacial pain

PurposeTo provide a scientific data related to the tonic activity of masseter muscle in subjects with and without history of orofacial pain during their normal daily life. MethodsThirty-three subjects were divided into two groups, a pain history group (PHG) and a non-pain history group (non-PHG), based on their responses to the Research Diagnostic Criteria for Temporomandibular Disorders questionnaire. After excluding four subjects with incomplete recordings, full-day masseter muscle surface EMGs of 29 subjects (10 men, 19 women; mean age 24.1 years) were analyzed. Tonic episode (TE) was defined as continuous EMG activity with a duration at least 2s with intensities above twice the baseline noise level. TEs were classified into 6 strength categories (<7.5%, 7.5–10%, 10–15%, 15–25%, 25–40% and >40% of the maximum voluntary clenching (MVC)). The mean duration of activity observed in the non-PHG+2 SD was adopted as a cutoff for identifying sustained TE. ResultsDuring waking hours, the incidence of sustained TEs was significantly higher in the PHG than in the non-PHG (p<0.05). The incidence and total duration of sustained TEs were significantly higher in the PHG than in the non-PHG at intensities of 7.5–10% MVC, 10–15% MVC, and 15–25% MVC (p<0.05). No significant difference was observed during sleep. ConclusionsWithin the limitations of this study, it would be concluded that sustained TEs may have a correlation with orofacial pain and the intensity range of 7.5–25% MVC would be an important range for future clenching studies

Evaluation of integral electromyographic values and median power frequency values in women with myogenous temporomandibular disorder and asymptomatic controls

BackgroundSurface electromyography (EMG) has been used as a reliable tool for the evaluation of electrical muscle activity. ObjectiveThe purpose of this study was to evaluate the EMG indices of the masticatory muscles (masseter, anterior temporalis and suprahyoid) in women with temporomandibular disorder (TMD) and asymptomatic controls in the time domain, by the integrated EMG signal (IEMG) and in the frequency domain, using the median power frequency (MPF). MethodsAn observational, cross-sectional study was conducted involving 30 asymptomatic women as the control (mean age: 25.85 ± 2.57 years) and 74 women with myogenous TMD (mean age: 26.54 ± 2.45 years) diagnosed using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Three EMG readings were taken during maximum voluntary clenching (MVC) of the molars on parafilm for five seconds with a three-minute rest interval between readings. The mixed-model analysis of variance test followed by the Bonferroni correction or the Student-t test was used for the analyses, with the level of significance set to 5% (p < 0.05). ResultsIEMG values were significantly higher in the masseter muscles than the anterior temporalis muscles in the control group (p < 0.01). IEMG values were significantly higher in the masseter muscles of the control group than the group with myogenous TMD (p < 0.05). MPF values of the suprahyoid muscles were significantly higher in the myogenous TMD group than the control group. ConclusionsThese significant findings show that women with myogenous TMD have reduction of electrical activity of their masseter muscles and increased firing rate of the motor units of the suprahyoid muscles. These findings may help the treatment of myogenous TMD in women.

Relationship between depression and masticatory muscles function in a group of adolescents

Objective: The aim of the study is to determine association between depressive symptoms and the electrical activity of muscles in maximum voluntary clench in a group of young adults.Methods: A total of 186 volunteers (Females = 98, Males = 88), with a mean age of 19 years, were recruited to the study. All participants took a questionnaire survey stating the level of depression (Beck’s scale), clinical examination, and instrumental diagnostics (EMG).Results: Symptoms of mild or medium depression were found in 35 of the subjects (18.82%). Average electric potentials of the masticatory muscles in maximal voluntary clench were significantly higher among the subjects with depression symptoms in comparison with subjects without those symptoms (85.96 ± 10.25 vs 78.97 ± 15.32, p < . 0.05).Discussion: An increase in the electrical potentials of masseter muscles in maximal voluntary clench was found in the group with depression symptoms. The study should be continued to confirm this finding.

Electromyographic ratio of masseter and anterior temporalis muscles in children with and without temporomandibular disorders

ObjectiveThis study investigated differences in surface electromyography (sEMG) activity of the masseter and anterior temporalis muscles in children with and without temporomandibular disorders (TMD). ParticipantsThirty-four children aged 8–12 years were recruited, comprising 17 children with TMD and 17 without TMD (control group [CG]). The children were quasi-matched for sex, age, weight, and height. sEMG data were obtained using Myosystem® Br-1 equipment with 12 channels to evaluate the bilateral masseter, anterior temporalis, and suprahyoid muscles. For sEMG analysis, raw and normalized root mean square (RMS) values were obtained at rest and during maximum clenching. The sEMG ratios of the raw RMS data of the bilateral masseter in relation to the anterior temporalis muscles (sEMG-M/AT ratio) were also assessed. Mann-Whitney tests (p ≤ 0.05) were used to compare sEMG ratio between TMD group and CG. ResultsSignificant prevalences of pain during chewing (53% vs. 0%, X2 = 5.87, p = 0.01), TMJ pain (58% vs. 0%, X2 = 6.67, p = 0.01), neck pain (58% vs. 18%, X2 = 3.77, p = 0.05) and pain in the temples (47% vs. 6%, X2 = 5.44, p = 0.02) were identified in the TMD group compared to CG. Our results revealed lower sEMG-M/AT ratios during maximum clenching (p = 0.01) in children with TMD compared to those in the asymptomatic CG. ConclusionThe results showed that children with TMD preferentially used their temporalis muscles during maximum voluntary clenching, probably as a consequence of nociceptive inputs in order to obtain pain relief.

Standardised surface electromyography allows effective submental muscles assessment

The aims of this pilot study were to evaluate: (i) the reproducibility and variability of an electromyographical protocol developed for the assessment of submental muscles (SM) (ii) to apply the new protocol to maximal teeth clenching, a simple and largely studied static task in order to quantify the relative contribution of submental muscles. In 20 healthy subjects, aged 19–35years, surface electromyography of SM, masseter (MM) and anterior temporalis (TA) muscles was performed during maximal voluntary clenching (MVC) with and without cotton rolls and the pushing of the tongue against the palate. Clenching on cotton rolls and pushing the tongue against the palate were used to standardise respectively MM and TA, and SM muscular potentials. The exercises were repeated in two appointments (T1–T2); submental muscles standardisation was also repeated twice (A-B) in each session to assess repeatability. Symmetry and activity were calculated for each couple of muscles. A two-way analysis of variance was computed for SM: no Factor 1 (T1 vs T2) or Factor 2 (A vs B) or F1×F2 significant effects were found. SM recruitment was 31% of the maximal activity, with symmetry values larger than 80%. In conclusion, standardised electromyography allows a reliable assessment of Submental muscles activity.

Effects of the functional orthopaedic therapy on masticatory muscles activity.

BackgroundThe purpose of this study was to examine surface electromyographic (sEMG) activity of masticatory muscles before and after functional orthopaedic therapy with Sander appliance.Material and MethodsTen adolescents (5 girls, 5 boys) with an Angle Class II, division I malocclusion, 9-13 years old, were submitted to sEMG before and after functional orthopaedic therapy. To verify the neuromuscular equilibrium, the standardized EMG activities of right and left masseter and anterior temporal muscles were recorded during maximum voluntary clench, and analysed calculating: POC (index of the symmetric distribution of the muscular activity determined by the occlusion); TC (index of presence of mandibular torque) and Ac (index suggesting the position of occlusal barycentre). The total muscular activity was also calculated. Pre- and post- functional therapy data were compared with Wilcoxon Signed-Rank Test.ResultsBefore treatment, all subjects had a good neuromuscular equilibrium, which was not altered by treatment.ConclusionssEMG evaluations allow to quantify the impact of occlusion on masticatory muscle activity and to control that the functional orthopaedic therapy maintain a good muscular coordination. Key words:Functional appliance, Sander appliance, electromyography, masticatory muscles.

Comparison of muscle activity between subjects with or without lip competence: Electromyographic activity of lips, supra- and infrahyoid muscles

Aim: This study compares the electromyographic (EMG) activity of the muscles from the lips and hyoid bone in subjects with or without lip competence.Methodology: Two groups of 20 subjects each, with or without lip competence were studied. EMG activity of the superior orbicularis oris (SOO), inferior orbicularis oris (IOO), suprahyoid (SH) and infrahyoid (IH) muscles was recorded with the subject seated in the upright position during the following tasks: (1) at rest; (2) speaking; (3) swallowing; (4) forced deep breathing; (5) maximal voluntary clenching; and (6) chewing.Results: EMG activity was significantly higher in subjects without competent lips than with competent lips in the SOO and IOO muscles during tasks 3 and 4, SOO during task 2 and IOO during task 6. EMG activity was similar in the SOO and IOO muscles during tasks 1 and 5, SOO during task 6 and IOO during task 2. Activity of the SH and IH muscles was similar in both groups for all tasks.Conclusions: Higher activity in subjects without competent lips implies a higher muscular effort due to the requirement of lip sealing during functional activities. Hyoid muscular activity was not modified by the presence or absence of lip competence.

Simulation of multi-stage nonlinear bone remodeling induced by fixed partial dentures of different configurations: a comparative clinical and numerical study.

This paper aimed to develop a clinically validated bone remodeling algorithm by integrating bone's dynamic properties in a multi-stage fashion based on a four-year clinical follow-up of implant treatment. The configurational effects of fixed partial dentures (FPDs) were explored using a multi-stage remodeling rule. Three-dimensional real-time occlusal loads during maximum voluntary clenching were measured with a piezoelectric force transducer and were incorporated into a computerized tomography-based finite element mandibular model. Virtual X-ray images were generated based on simulation and statistically correlated with clinical data using linear regressions. The strain energy density-driven remodeling parameters were regulated over the time frame considered. A linear single-stage bone remodeling algorithm, with a single set of constant remodeling parameters, was found to poorly fit with clinical data through linear regression (low [Formula: see text] and R), whereas a time-dependent multi-stage algorithm better simulated the remodeling process (high [Formula: see text] and R) against the clinical results. The three-implant-supported and distally cantilevered FPDs presented noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs showed bone resorption or no visible bone formation in some areas. Time-dependent variation of bone remodeling parameters is recommended to better correlate remodeling simulation with clinical follow-up. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodeling. Caution should be exercised when selecting the cantilever FPD due to the risk of overloading bone resorption.

Masseter Muscle Activity in Track and Field Athletes: A Pilot Study.

Teeth clenching has been shown to improve remote muscle activity (by augmentation of the Hoffmann reflex), and joint fixation (by decreased reciprocal inhibition) in the entire body. Clenching could help maintain balance, improve systemic function, and enhance safety. Teeth clenching from a sports dentistry viewpoint was thought to be important and challenging. Therefore, it is quite important to investigate mastication muscles’ activity and function during sports events for clarifying a physiological role of the mastication muscle itself and involvement of mastication muscle function in whole body movement. Running is a basic motion of a lot of sports; however, a mastication muscles activity during this motion was not clarified. Throwing and jumping operation were in a same situation. The purpose of this study was to investigate the presence or absence of masseter muscle activity during track and field events. In total, 28 track and field athletes took part in the study. The Multichannel Telemetry system was used to monitor muscle activity, and the electromyograms obtained were synchronized with digital video imaging. The masseter muscle activity threshold was set 15% of maximum voluntary clenching. As results, with few exceptions, masseter muscle activity were observed during all analyzed phases of the 5 activities, and that phases in which most participants showed masseter muscle activity were characterized by initial acceleration, such as in the short sprint, from the commencement of throwing to release in both the javelin throw and shot put, and at the take-off and landing phases in both jumps.

Reorganization of muscle activity in patients with chronic temporomandibular disorders

ObjectiveTo investigate whether reorganization of muscle activity occurs in patients with chronic temporomandibular disorders (TMD) and, if so, how it is affected by symptomatology severity. MethodsSurface electromyography (sEMG) of masticatory muscles was made in 30 chronic TMD patients, diagnosed with disc displacement with reduction (DDR) and pain. Two 15-patient subgroups, with moderate (TMDmo) and severe (TMDse) signs and symptoms, were compared with a control group of 15 healthy subjects matched by age. The experimental tasks were: a 5s inter-arch maximum voluntary clench (MVC); right and left 15s unilateral gum chewing tests. Standardized sEMG indices characterizing masseter and temporalis muscles activity were calculated, and a comprehensive functional index (FI) was introduced to quantitatively summarize subjects’ overall performance. Mastication was also clinically evaluated. ResultsDuring MVC, TMDse patients had a significantly larger asymmetry of temporalis muscles contraction. Both TMD groups showed reduced coordination between masseter and temporalis muscles’ maximal contraction, and their muscular activity distribution shifted significantly from masseter to temporalis muscles. During chewing, TMDse patients recruited the balancing side muscles proportionally more than controls, specifically the masseter muscle. When comparing right and left side chewing, the muscles’ recruitment pattern resulted less symmetric in TMD patients, especially in TMDse. Overall, the functional index of both TMDmo and TMDse patients was significantly lower than that obtained by controls. ConclusionsChronic TMD patients, specifically those with severe symptomatology, showed a reorganized activity, mainly resulting in worse functional performances.