Surface electromyography in the assessment of jaw elevator muscles

Is there a relationship between the presence of external root resorption in second molars adjacent to impacted mandibular third molars with awake bruxism and masticatory muscle activity?

OBJECTIVES

This study aimed to assess whether awake bruxism and masticatory muscle activity could be related to external root resorption (ERR) in second molars adjacent to impacted mandibular third molars.

MATERIALS AND METHODS

Sixty patients, with requests for a cone-beam, computed tomography, were divided into two groups: ERR (patients with ERR in the second molar, n = 30), and control group (n = 30). Awake bruxism was assessed through the Oral Behaviors Checklist (OBC) and an ecological momentary assessment (EMA). Surface electromyography (EMG) was used to assess the masseter and anterior temporal muscle function. Normality and homogeneity of variances were demonstrated. Descriptive analysis was performed, using the T-test and Chi-square test to compare the characteristics of the groups. A multiple regression model was performed.

RESULTS

The ERR group presented more non-functional oral activities related to awake bruxism than the control group, according to OBC (p = 0.027) and EMA (p = 0.035). In addition, the ERR group had higher EMG activity than the control group in rest and isotonic protocols (p < 0.05).

CONCLUSIONS

Awake bruxism and greater masticatory muscle activity seem to be related to the presence of ERR in second molars adjacent to impacted mandibular third molars.

CLINICAL RELEVANCE

The results of the present study can reinforce the theory that triggering ERR in the second molars adjacent to impacted mandibular third molars may be related to mechanical forces coming from the masticatory function.

A multimodal approach to automated hierarchical assessment of bulbar involvement in amyotrophic lateral sclerosis

Introduction

As a hallmark feature of amyotrophic lateral sclerosis (ALS), bulbar involvement leads to progressive declines of speech and swallowing functions, significantly impacting social, emotional, and physical health, and quality of life. Standard clinical tools for bulbar assessment focus primarily on clinical symptoms and functional outcomes. However, ALS is known to have a long, clinically silent prodromal stage characterized by complex subclinical changes at various levels of the bulbar motor system. These changes accumulate over time and eventually culminate in clinical symptoms and functional declines. Detection of these subclinical changes is critical, both for mechanistic understanding of bulbar neuromuscular pathology and for optimal clinical management of bulbar dysfunction in ALS. To this end, we developed a novel multimodal measurement tool based on two clinically readily available, noninvasive instruments-facial surface electromyography (sEMG) and acoustic techniques-to hierarchically assess seven constructs of bulbar/speech motor control at the neuromuscular and acoustic levels. These constructs, including prosody, pause, functional connectivity, amplitude, rhythm, complexity, and regularity, are both mechanically and clinically relevant to bulbar involvement.

Methods

Using a custom-developed, fully automated data analytic algorithm, a variety of features were extracted from the sEMG and acoustic recordings of a speech task performed by 13 individuals with ALS and 10 neurologically healthy controls. These features were then factorized into 10 composite outcome measures using confirmatory factor analysis. Statistical and machine learning techniques were applied to these composite outcome measures to evaluate their reliability (internal consistency), validity (concurrent and construct), and efficacy for early detection and progress monitoring of bulbar involvement in ALS.

Results

The composite outcome measures were demonstrated to (1) be internally consistent and structurally valid in measuring the targeted constructs; (2) hold concurrent validity with the existing clinical and functional criteria for bulbar assessment; and (3) outperform the outcome measures obtained from each constituent modality in differentiating individuals with ALS from healthy controls. Moreover, the composite outcome measures combined demonstrated high efficacy for detecting subclinical changes in the targeted constructs, both during the prodromal stage and during the transition from prodromal to symptomatic stages.

Discussion

The findings provided compelling initial evidence for the utility of the multimodal measurement tool for improving early detection and progress monitoring of bulbar involvement in ALS, which have important implications in facilitating timely access to and delivery of optimal clinical care of bulbar dysfunction.

Assessment of Electromyographic Changes in Masseter and Temporalis Muscles for Patients Undergoing Lower Third Molar Surgery: A Prospective Study

Introduction Lower third molar impaction surgery is one of the most common minor oral surgical procedures done. Trismus has been one of the most common and disturbing postoperative sequelae for patients. The study aimed to evaluate the electrical activity of the masseter and temporalis muscles after mandibular third molar surgery. Materials and methods The research was conducted at Saveetha Dental College and hospitals in the Department of Oral and Maxillofacial Surgery. The study consisted of 20 individuals. The EMG (electromyography) activities of both masseter muscles in each patient were measured before the tooth extraction surgery, postoperatively after 72 hours, and after seven days. The inter-incisal distance was also measured at similar follow-up intervals. Data were analyzed using IBM Corp. Released 2015. IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp., with p-values less than 0.05 considered statistically significant. The Mann-Whitney U test was used for the comparison of electrical activity between masseter and temporalis on both the operated and non-operated sides during preoperative, postoperative, 72-hour, and postoperative seven-day periods. Results It has been found that the electrical activity of the temporalis is higher than that of the masseter muscle measured at all the intervals of the follow-up period, with statistically significant values (p=0.001). It was noted that all the patients have reduced mouth opening when compared with preoperative (mean mouth opening = 45.6 mm), postoperative 72 hours (mean mouth opening = 31.2 mm), and postoperative seven days (mean mouth opening =35.6 mm). When a comparison was done between temporalis and masseter, the masseter took longer to return to pre-operative electrical activity, which might also imply that for prolonged trismus seen in patients after lower third molar surgery, it is the masseter that is affected and needs recovery for trismus to be resolved.  Conclusion  Based on the results obtained, it can be concluded that there was a reduction in the electrical activity of both the masseter and temporalis post-third molar impaction surgery. It was also found that there was a reduction in mouth opening in patients who underwent lower third molar extraction surgery. Masseter muscle took longer to return to its preoperative electrical activity than temporalis muscle, implying that targeted therapies to accelerate the healing of masseter muscle may prevent prolonged trismus in patients who undergo lower third molar impaction surgery.

Electromyographic Assessment of Muscle Activity in Children Undergoing Orthodontic Treatment-A Systematic Review

Background: Surface electromyography (sEMG) can provide an objective and quantitative image of the functional state of neuromuscular balance in the stomatognathic system. The objective of this systematic review is to examine current scientific evidence regarding the effects of orthodontic treatment on muscle electromyographic (EMG) activity in children. Methods: The search strategy included the PubMed, PubMed Central, Web of Science, Scopus, and Embase databases. The inclusion criteria were studies assessing EMG muscle activity in children undergoing orthodontic treatment compared with untreated children. The Cochrane risk-of-bias tool (RoB2) and the Newcastle-Ottawa Scale (NOS) were used to evaluate the quality of the studies. The quality of evidence assessment was performed using GRADE analysis. The PRISMA diagram visually represented the search strategy, as well as screening and inclusion process. Results: The search strategy identified 540 potential articles. Fourteen papers met the inclusion criteria. Six studies were judged at a low risk of bias. The certainty of evidence was rated as moderate to low, according to the GRADE criteria. Studies showed alterations in EMG muscle activity in children undergoing orthodontic treatment. Conclusions: Orthodontic treatment appears to affect muscle activity in children undergoing orthodontic treatment. However, the quality of evidence is low and, therefore, it is not possible to definitively state this effect. Further long-term studies are needed to confirm the findings of this review. Study protocol number in PROSPERO database: CRD42023491005.

A Fine-Grained Temporal Analysis of Multimodal Oral Diadochokinetic Performance to Assess Speech Impairment in Amyotrophic Lateral Sclerosis

PURPOSE

This study used a semiautomated fine-grained temporal analysis to extract features of temporal oral diadochokinetic (DDK) performance across multiple modalities and tasks, from neurologically healthy and impaired individuals secondary to amyotrophic lateral sclerosis (ALS). The aims were to (a) delineate temporal oral DDK deficits relating to the neuromotor pathology of ALS and (b) identify the optimal task-feature combinations to detect speech impairment in ALS.

METHOD

Mandibular myoelectric, kinematic, and acoustic data were acquired from 13 individuals with ALS and 10 healthy controls producing three alternating motion rate tasks and one sequential motion rate task. Twenty-seven features were extracted from the multimodal data, characterizing three temporal constructs: duration/rate, variability, and coordination. The disease impacts on these features were assessed across tasks, and the task eliciting the greatest disease-related change was identified for each feature. Such "optimal" task-feature combinations were fed into logistic regression to differentiate individuals with ALS from healthy controls.

RESULTS

Temporal deficits in ALS were characterized by (a) increased duration and variability and reduced coordination of jaw muscle activities, (b) increased duration and variability and altered temporal symmetry of jaw velocity profile, (c) increased muscle-burst-to-peak-velocity duration, and (d) increased motion-to-voice onset duration. These temporal features were differentially affected across tasks. The optimal task-feature combinations, which were further clustered into three composite factors reflecting temporal variability, coarser-grained duration, and finer-grained duration, differentiated ALS from controls with an F1 score of 0.86 (precision = 1.00, recall = 0.75).

CONCLUSIONS

Temporal oral DDK deficits are likely attributed to a hierarchy of interrelated neurophysiological and biomechanical factors associated with the neuromotor pathology of ALS. These deficits, as assessed crossmodally, provide previously unavailable insights into the multifaceted timing impairment of oromotor performance in ALS. The optimal task-feature combinations targeting these deficits show promise as quantitative markers for (early) detection of speech impairment in ALS.

Electromyography: Processing, Muscles' Electric Signal Analysis, and Use in Myofunctional Orthodontics

Electromyography, commonly known as EMG, utilizes superficial or needle electrodes to record and analyze the fundamental electrical characteristics of skeletal muscles, determining whether the muscles are contracting. The motor unit, which consists of a collection of group muscle fibers and the motor neurons that govern them, is the structural basis of EMG. Three types of electrode are used in EMG which are needle electrode, fine wire electrode, and surface electrode. A significant amount of literature indicates that the correction of muscle function affects the relationships between teeth within the same jaw and between the jaws on opposing sides. The mechanism of action in myofunctional appliance therapy is linked to neuromuscular and skeletal adaptations resulting from altered function in the orofacial region. Both myofunctional therapy and orthodontics aim to address abnormal muscular behavior, restore abnormal muscle activity, and maintain proper alignment in various areas, including the lips, lower jaw, and tongue. This knowledge is essential for functions such as swallowing, speaking, chewing, and respiration as well as for minimizing incorrect movements and positioning. This article aims to describe the application of surface EMG as a diagnosis tool for assessing muscle activities in various orthodontic disorders, such as class II malocclusion open bite, crossbite, maxillary constriction, cleft lip and palate (CLP), and temporomandibular dysfunction, in patients. The electrodes used in EMG can be utilized to detect bioelectric activity in the muscles of the jaws and abnormalities in jaw movement. Analyzing EMG data is vital for obtaining a comprehensive understanding of the masticatory muscle system.

Muscle activity between dentate and edentulous patients rehabilitated with dental prostheses: A systematic review

BACKGROUND

Adequate muscle activity is important for the success of oral rehabilitation: it maintains the integrity of the stomatognathic system and is responsible for chewing movements needed to break, crush and grind food.

OBJECTIVE

To compare muscle activity using electromyography (EMG) while clenching or chewing soft and/or hard foods among individuals with natural dentition (ND) and edentulous patients rehabilitated with dental prostheses.

METHODS

This review was conducted until March, 2023, and the research question was "Is the muscle activity of edentulous patients rehabilitated with dental prostheses similar to that of dentate individuals?" A search strategy was conducted in PubMed/MEDLINE, The Cochrane Library, Web of Science, Lilacs, Embase and manual journal searches.

RESULTS

Ten studies were included in the analysis. Most of them reported that individuals with ND had significant higher muscle activity (clenching or chewing) than complete dentures (CD) users. However, no difference was observed between patients with full mouth implant-supported fixed dental prosthesis (ISFDP) and ND. Additionally, two studies compared patients with mandibular ISFDP with maxillary CD and individuals with ND and found no differences; however, one study concluded that patients with ISFDP with CD (maxillary or mandibular) had lower muscle activity than individuals with ND. Only one study reported a higher muscle activity in patients with full-mouth ISFDP than in individuals with ND.

CONCLUSIONS

Bimaxillary CD users had lower muscle activity than individuals with ND. During rehabilitation, the muscle activity of patients with full-mouth ISFDP and mandibular ISFDP with maxillary CD is similar to individuals with ND.

Food consumption and masticatory performance of normal weight, overweight and obese children aged 7 to 12 years old

Childhood obesity is a significant public health problem. Studies show that obese children are more likely to become obese adults. In an attempt to ascertain the factors associated with childhood obesity, research has shown that this condition is associated with changes in food consumption and masticatory performance. The aim of this study was thus to evaluate food consumption and masticatory performance in normal weight, overweight and obese children aged 7 - 12 years. A cross-sectional study was carried out with 92 children aged 7 - 12 years, of both sexes, from a public school in a Brazilian municipality. The children were divided into the following groups: normal weight (n = 48), overweight (n = 26) and obese (n = 18). Anthropometric parameters, food consumption, food consistency preference, and masticatory performance were evaluated. Pearson's chi-square test was used to compare categorical variables. To compare numerical variables, the one-way ANOVA test was applied. For variables not conforming to a normal distribution, the Kruskal-Wallis test was used. The level of statistical significance was set at p ≤ 0.05. Our results show that the children with obesity consumed fewer fresh foods (median = 3, IQI = 4.00-2.00, p = 0.026), consumed more ultra-processed foods (median = 4, IQI = 4.00-2.00, p = 0.011), performed fewer mastication sequences (median = 2, IQI = 3.00-2.00, p = 0.007), and ate faster (median = 58.50, IQI = 69.00-48.00, p = 0.026) compared to children of normal weight. We conclude that children with obesity exhibit differences in food consumption and masticatory performance compared to children of normal weight.

Long-term evaluation of masseter muscle activity, dimensions, and elasticity after orthognathic surgery in skeletal class III patients

OBJECTIVE

To evaluate changes in the masseter muscle after orthognathic surgery using electromyography (EMG), ultrasonography (US), and ultrasound elastography (USE) in individuals with skeletal class III anomaly over long-term follow-up and compare with a control group.

MATERIALS AND METHODS

The study group included 29 patients with class III dentofacial deformities scheduled to undergo orthodontic treatment and orthognathic surgery. The control group included 20 individuals with dental class I occlusion. Assessment of the masseter muscles using EMG, US, and USE was performed before orthognathic surgery (T1) and at postoperative 3 months (T2) and 1 year (T3) in the study group, and at a single time point in the control group. All assessments were performed at rest and during maximum clenching. Masseter muscle activity, dimension, and hardness were analyzed.

RESULTS

Electromyographic activity of the masseter muscle during maximum clenching was increased at postoperative 1 year but did not reach control group values. On ultrasonography, the masseter muscle showed minimal changes in dimension at postoperative 1 year compared to preoperative values and remained below control group values. The postoperative increase in masseter muscle hardness at rest and during maximum clenching persisted at postoperative 1 year.

CONCLUSION

The results of this study suggest that after orthognathic surgery, additional interventions and much longer follow-up are needed to ensure better muscle adaptation to the new occlusion and skeletal morphology.

CLINICAL RELEVANCE

All assessment methods are useful for comprehensively evaluating changes in the masticatory muscles after orthognathic surgery.

Maximum bilateral bite strength and RMS EMG for the diagnosis of myogenic TMD

Aim: The study aimed to evaluate the accuracy of the maximum bilateral molar bite force and the Root Mean Square (RMS) Electromyography (EMG) index of the masticatory muscles in the maximum bilateral molar bite (MMBMax) of women with myogenic Temporomandibular Disorder (TMD) and asymptomatic. Methods: This is a cross-sectional study, composed of 86 women allocated to the TMD Group (n=43) and Control Group (n=43) diagnosis through the Diagnostic Criteria for Temporomandibular Disorders. The maximum bilateral molar bite force was evaluated using a bite dynamometer and the RMS EMG index of the masticatory muscles (anterior temporalis, masseter) during 5 seconds of the MMBMax task. Student t-test was used for data comparison between accuracy of the bite force and RMS EMG of masticatory muscles during the MMBMax. Results: The maximum bilateral molar bite force showed high accuracy (AUC=0.99) for the diagnosis of women with myogenic TMD and asymptomatic women, and the RMS EMG index evaluated during the MMBMax showed a moderate level of accuracy for all masticatory muscles (AUC=0.70 to 0.75). Conclusion: The bilateral bite dynamometer with a surface EMG during bilateral bite can be used to diagnose TMD in young women.

Ecological Momentary Assessment of Masseter Muscle Activity in Patients with Bruxism

According to the International Bruxism Consensus, bruxism refers to the activity of the masticatory muscles reflecting contraction disorders, regardless of whether it is during sleep (SB) or an awake (AB) state. The objective of the present study was to evaluate the activity of the masseter muscle by surface electromyographic (sEMG) recordings. This study was performed on 20 participants with self-reported “possible bruxism” (study group) and 20 participants with no self-reported bruxism (control group); all participants underwent an evaluation of the masseter muscle activity using the dia-BRUXO device, which provides numerical parameters regarding sEMG (the total duration and the type of bruxism specific events, the effort made by the masticatory muscles during the recording period, and the personal bruxism index of each participant). Participants from the study group presented more clenching events during AB, three times more frequent than the control group (p = 0.002, Mann−Whitney U test); for SB, the frequency of clenching and grinding events was comparable within the study group, being more frequent than for the control group; the mean value of the effort index was higher for AB (1.177%) than SB (0.470%) and the same for the duration index, with a mean value of 2.788% for AB and 1.054% for SB. All participants from the control group presented reduced values for all acquired parameters. Overall, the personal bruxism index in AB was approximately four times higher for the study group (2.251%) compared to the control group (0.585%) (p < 0.005, Mann−Whitney U test). Similar values were obtained for SB. All participants with “possible bruxism” from the study group presented a higher activity of the masseter muscle, which is specific for bruxism, thus being defined as “definite bruxism”.

Can the subject reliably reproduce maximum voluntary contraction of temporalis and masseter muscles in surface EMG?

OBJECTIVE

To evaluate the repeatability of the surface EMG variables of myoelectric signals from the masseter and temporalis muscles according to three methods to induce maximum voluntary contraction (MVC) in healthy adults.

METHODS

Thirty healthy young subjects performed the following three MVC tasks three times each in three sessions on the same day without replacing surface electrodes: clenching the teeth (MVCIC) and biting down on two cotton rolls bilaterally with the posterior teeth (MVCBP) or first molars (MVCB6).

RESULTS

The intra-class correlation coefficient (ICC) of the amplitudes during the three MVC tasks ranged from 65 to 79%. The ICCs of the spectral variables ranged from 78 to 86%. The ICCs of the asymmetry index of the masseter ranged from 77 to 86%, and those of the activity index ranged from 68 to 90%.

CONCLUSION

The surface EMG measurements according to the three MVC methods exhibited good to excellent reproducibility.

The effect of tooth cusp morphology and grinding direction on TMJ loading during bruxism

Increased mechanical loading of the temporomandibular joint (TMJ) is often connected with the onset and progression of temporomandibular joint disorders (TMD). The potential role of occlusal factors and sleep bruxism in the onset of TMD are a highly debated topic in literature, but ethical considerations limit in vivo examinations of this problem. The study aims to use an innovative in silico modeling approach to thoroughly investigate the connection between morphological parameters, bruxing direction and TMJ stress. A forward-dynamics tracking approach was used to simulate laterotrusive and mediotrusive tooth grinding for 3 tooth positions, 5 lateral inclination angles, 5 sagittal tilt angles and 3 force levels, giving a total of 450 simulations. Muscle activation patterns, TMJ disc von Mises stress as well as correlations between mean muscle activations and TMJ disc stress are reported. Computed muscle activation patterns agree well with previous literature. The results suggest that tooth inclination and grinding position, to a smaller degree, have an effect on TMJ loading. Mediotrusive bruxing computed higher loads compared to laterotrusive simulations. The strongest correlation was found for TMJ stress and mean activation of the superficial masseter. Overall, our results provide in silico evidence that TMJ disc stress is related to tooth morphology.

Relationship between rate-elicited changes in muscular-kinematic control strategies and acoustic performance in individuals with ALS-A multimodal investigation

INTRODUCTION

As a key control variable, duration has been long suspected to mediate the organization of speech motor control strategies, which has management implications for neuromotor speech disorders. This study aimed to experimentally delineate the role of duration in organizing speech motor control in neurologically healthy and impaired speakers using a voluntary speaking rate manipulation paradigm.

METHODS

Thirteen individuals with amyotrophic lateral sclerosis (ALS) and 10 healthy controls performed a sentence reading task three times, first at their habitual rate, then at a slower rate. A multimodal approach combining surface electromyography, kinematic, and acoustic technologies was used to record jaw muscle activities, jaw kinematics, and speech acoustics. Six muscular-kinematic features were extracted and factor-analyzed to characterize the organization of the mandibular control hierarchy. Five acoustic features were extracted, measuring the spectrotemporal properties of the diphthong /ɑɪ/ and the plosives /t/ and /k/.

RESULTS

The muscular-kinematic features converged into two interpretable latent factors, reflecting the level and cohesiveness/flexibility of mandibular control, respectively. Voluntary rate reduction led to a trend toward (1) finer, less cohesive, and more flexible mandibular control, and (2) increased range and decreased transition slope of the diphthong formants, across neurologically healthy and impaired groups. Differential correlations were found between the rate-elicited changes in mandibular control and acoustic performance for neurologically healthy and impaired speakers.

CONCLUSIONS

The results provided empirical evidence for the long-suspected but previously unsubstantiated role of duration in (re)organizing speech motor control strategies. The rate-elicited reorganization of muscular-kinematic control contributed to the acoustic performance of healthy speakers, in ways consistent with theoretical predictions. Such contributions were less consistent in impaired speakers, implying the complex nature of speaking rate reduction in ALS, possibly reflecting an interplay of disease-related constraints and volitional duration control. This information may help to stratify and identify candidates for the rate manipulation therapy.

Effect of facet inclination and location on TMJ loading during bruxism: An in-silico study

•

Sheds new light on the important potential connection between tooth grinding and temporomandibular joint loading

•

Demonstrates a larger effect of grinding inclination than grinding position on TMJ loading

•

Creates a novel computer simulation of TMJ disc stress during dynamic tooth grinding tasks

•

Uses state-of-the-art in silico methods for a highly multidisciplinary investigation, which is not feasible in vivo

•

Presents a tracking simulation approach to work around the highly complicated recording of masticatory muscle EMG acquisition

Introduction

Functional impairment of the masticatory region can have significant consequences that range from a loss of quality of life to severe health issues. Increased temporomandibular joint loading is often connected with temporomandibular disorders, but the effect of morphological factors on joint loading is a heavily discussed topic. Due to the small size and complex structure of the masticatory region in vivo investigations of these connections are difficult to perform.

Objectives

We propose a novel in silico approach for the investigation of the effect of wear facet inclination and position on TMJ stress.

Methods

We use a forward-dynamics tracking approach to simulate lateral bruxing on the canine and first molar using 6 different inclinations, resulting in a total of 12 simulated cases. By using a computational model, we control a single variable without interfering with the system. Muscle activation pattern, maximum bruxing force as well as TMJ disc stress are reported for all simulations.

Results

Muscle activation patterns and bruxing forces agree well with previously reported EMG findings and in vivo force measurements. The simulation results show that an increase in inclination leads to a decrease in TMJ loading. Wear facet position seems to play a smaller role with regard to bruxing force but might be more relevant for TMJ loading.

Conclusion

Together these results suggest a possible effect of tooth morphology on TMJ loading during bruxism.

Smartphone addiction and the relationship with head and neck pain and electromiographic activity of masticatory muscles

BACKGROUND

Excessive use of smartphones may be associated with behavioral and physical health changes and might cause musculoskeletal alterations in the head and neck region.

OBJECTIVE

To evaluate the prevalence of smartphone addiction in college students and its correlation with symptoms of head and neck pain and masticatory and trapezius muscle activity while resting, before and after smartphone use.

METHODS

Twenty university students participated in the study. They answered the Smartphone Addiction Scale and the Fonseca Anamnestic Index. Next, the participants were seated and prepared for electromyography through the placement of surface electrodes on the masseter, temporal, and trapezius muscles. Rest condition data were collected for 10 seconds before and after 30 minutes of smartphone use.

RESULTS

The results showed that 35% of the evaluated individuals were classified as smartphone addicted and 35% reported no head or neck pain in the previous 30 days. There was no association between smartphone use and head and neck pain. In the electromyography, there was an increase in RMS values after smartphone use in the right and left masseter muscles and the left trapezius.

CONCLUSION

College students presented a high prevalence of smartphone addiction and head and neck pain, but these were not statistically associated. There was a change in muscle activity only in the right trapezius muscles before and after 30 minutes of smartphone use. These findings are contrary to the current belief that the use of smartphones correlates with pain in the neck region and changes in the electrical muscle activity, leading to fatigue in the cervical muscles.

Surface Electromyography (sEMG) Activity of Masticatory Muscle (Masseter and Temporalis) with Three Different Types of Orthodontic Bracket

Objective

This pre-post study is aimed at determining the effects of masticatory muscle activity (masseter and temporalis) measured via sEMG between conventional, self-ligating, and ceramic bracket after six months of orthodontic treatment.

Methods

A total of eighteen (18) malocclusion patients were identified. Malocclusion patients were subdivided into 3 groups based on the bracket selection (conventional, self-ligating, and ceramic bracket) with 6 patients for each group. sEMG of muscles were done using a two-channel electromyography device, where pregelled and self-adhesive electrodes (bilateral) were applied. Chewing and clenching of masseter and temporalis muscle activity were recorded for 20 s pre and 6 months of orthodontic treatment using sEMG (frequency 60 Hz). The data were analysed by using repeated measures ANOVA in IBM SPSS Statistics Version 24.0.

Results

Chewing and clenching for masseter muscle showed no significant difference (P > 0.05) in sEMG activity of three types of the brackets. However, for temporalis muscle, there was a significant difference found in sEMG activity during chewing (P < 0.05) and clenching (P < 0.05) between these three brackets.

Conclusion

The activity of temporalis muscle showed significant changes in chewing and clenching, where the conventional group demonstrated better muscle activity pre and at six months of fixed appliances.

Masseter muscle activity of conventional denture, fixed prosthesis, and milled bar overdenture used for All-on-4 implant rehabilitation: A within-subject study

PURPOSE

to examine the electromyographic (EMG) activity of the masseter muscles in patients with conventional dentures and compare it to EMG activity of fixed prosthesis, and milled bar overdentures used to rehabilitate mandibular atrophied ridges according to the All-on-4 concept.

METHODS

Eighteen edentulous subjects with atrophied mandibles received complete dentures (CD, control). After 3 months, four implants were installed between the mental foramina according to the "All-on-4" protocol and loaded immediately. After osseointegration, fixed prostheses (FPD) or milled bar overdentures (MBO) were given to the patients in random order. Primary (amplitude), and secondary (chewing rate, time of the masticatory cycle, time of masticatory burst, and masticatory time) outcomes were evaluated 3 months after using CD, FPD, and MBO. The evaluations were made during mastication of carrot (hard) and cake (soft) foods.

RESULTS

FPD and MBO were associated with a significantly higher (amplitude, time of masticatory cycle, and time of masticatory burst), and significantly lower (chewing rate and masticatory time) compared with conventional dentures. Primary and secondary outcomes did not differ between FPD and MBO. Carrot had significantly higher amplitude, chewing rate, time of masticatory burst, and masticatory time than cake, while cake had a significantly higher time of masticatory cycle than carrot.

CONCLUSIONS

Within limitations of this study, milled bar overdentures for All-on-4 implant rehabilitation of atrophied mandible is not less efficient than fixed prostheses in terms of electromyographic activity of the masseter muscle. Both prostheses significantly improve muscle activity, chewing rate, time of masticatory cycle, time of masticatory burst, and masticatory time compared with conventional dentures.

Evaluation of 1-Piece Versus 3-Piece Framework Designs for the Edentulous Mandible with Fixed Implant-Supported Prostheses: A Clinical, Occlusal and Biomechanical Study

PURPOSE

This study aims to evaluate the clinical, occlusal and biomechanical performance of 1-piece and 3-piece designs for implant-supported fixed dentures in the edentulous mandible.

MATERIALS AND METHODS

A total of 65 patients with edentulous mandibles who underwent fixed implant-supported restorations were recruited and subsequently assigned to 1 of 2 groups based on the framework design (1-piece or 3-piece). The participants underwent clinical and occlusal examination using a periodontal probe, T-Scan III system, and electromyography 12 months after prosthesis delivery. Two mandibular finite element models were created to evaluate stress values and their distribution during function.

RESULTS

Ninety-five point four percent (n = 62) of participants in the follow-up period underwent clinical and occlusal examination after prosthesis delivery. Clinical examination revealed a trend towards increased inflammation around the implants in the 1-piece prostheses. Occlusal parameters indicated that the 1-piece design was superior for the masticatory system than the 3-piece design. Biomechanical analysis revealed the highest stress values in the posterior region of the 3-piece design.

CONCLUSIONS

On the basis of ease of ensuring oral hygiene, when compared to the 3-piece design, the 1-piece framework design might be the superior therapy for restoring an edentulous mandible, based on occlusal and biomechanical outcomes.

Impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency

BACKGROUND

Whether precise orthodontic detailing of occlusion impacts masticatory function is unknown. In this study, we aimed to assess the impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency.

MATERIALS AND METHODS

Fifty-four adults who completed orthodontic treatment were categorized into two groups using the American Board of Orthodontics (ABO) model grading system: one meeting ABO standards (ABO, N = 29), the other failing to meet them (non-ABO, N = 25). The electromyographic (EMG) signals of the anterior temporalis (AT) and superficial masseter muscles were recorded bilaterally during static (clenching) and dynamic (gum chewing) tests. Chewing efficiency was measured by calculating the median particle size (MPS) and broadness of particle distribution (BPD) after five chewing trials of experimental silicone food at a standardized chewing rate.

RESULTS

Participants of the ABO group had a slightly more symmetric activation of the AT muscles during clenching (P = 0.016) and chewed a gum at a slower rate (P = 0.030). During the standardized chewing test with silicone food, ABO subjects had slightly greater EMG potentials at all muscle locations than non-ABO individuals (all P < 0.05). MPS and BDP did not differ significantly between groups (all P > 0.05).

LIMITATIONS

The severity of the initial malocclusion of the study participants was not in the statistical model as a potential confounder on the outcome measures.

CONCLUSIONS

Meeting ABO standards contributes to a slightly more balanced activation of the temporalis muscles during clenching and more efficient muscle recruitment during chewing but does not improve chewing efficiency.

Evaluation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording

INTRODUCTION

Patients undergoing clear aligner therapy (CAT) report muscle tenderness and produce wear facets on their aligner trays. However, little is known about the masticatory muscle response to clear aligners. Here, we measured the activity of the masseter during CAT using ambulatory electromyography. We also explored whether psychological traits modulate the masticatory muscle response to CAT.

METHODS

Using portable data loggers, we recorded the electromyographic (EMG) activity in the right masseter muscle of 17 healthy adults without temporomandibular disorder (16 females, 1 male; mean age ± standard deviation, 35.3 ± 17.6 years) commencing treatment with CAT over 4 weeks, under the following conditions: week 1 without aligners (baseline), week 2 with a passive aligner (dummy), week 3 with their first active aligner (active1), and week 4 with their second active aligner (active2). We used a mixed-effect model to test differences in EMG activity over the 4-weeks and a general linear model to test the effect of psychological traits on EMG activity.

RESULTS

The EMG activity of the masseter increased significantly with aligners compared with baseline. The largest relative increase in EMG activity was seen during the dummy (152%; P <0.001) and active1 (155%; P <0.001) stages. During active2, the activity of the masseter decreased significantly toward baseline levels. Participants' trait anxiety was positively associated with increases in EMG activity (P = 0.027).

CONCLUSIONS

CAT is associated with a transient increase in masticatory muscle activity, possibly because of an increase in wake-time parafunctional tooth clenching. Temporomandibular disorder-free patients adapt well to CAT as the masticatory muscle activity decreases toward baseline levels after 2 weeks.

Hall technique crowns and children's masseter muscle activity: A surface electromyography pilot study

BACKGROUND

Hall technique crowns (HTCs) alter the occlusion temporarily, potentially affecting jaw muscles, particularly the masseter - the primary jaw-closing muscle.

AIM

To assess masseter muscle activity (MMA) in children treated with a unilateral HTC.

DESIGN

In 12 children treated with a single HTC, bilateral MMA was recorded with surface electromyography (sEMG) for ten cycles of Rest Position (RP) and Maximum Voluntary Clenching (MVC) over 20 seconds immediately pre-HTC cementation (P_base ), immediately post-HTC cementation (P_immed ), at 2 weeks post-HTC cementation (P_2w ) and at 6 weeks post-HTC cementation (P_6w ). t test, ANOVA and post hoc statistics were used (P < .05).

RESULTS

As expected, MMA was low at rest and increased during maximal jaw clenching (P < .0001). MMA (mean ± SD) increased significantly (P < .001) between RP and MVC at: P_base [from 1.60 μV·s (±0.96) to 5.40(±2.30)]; P_immed [1.57(±1.15) to 3.75(±1.87)]; P_2w [1.39(±0.54) to 5.54(±1.45)] and finally P_6w [1.46(±0.56) to 6.45(±2.56)]. Rest MMA at P_base , P_immed , P_2w and P_6w remained unchanged (P = .18) whereas P_base clench MMA reduced by a third at P_immed (P < .001), returned to and exceeded baseline levels at P_2w (P = .822) and P_6w (P < .001), respectively.

CONCLUSIONS

This pilot study showed that Hall technique crowns may affect masseter muscle activity in children. Clench MMA was reduced immediately post-treatment but returned to and later exceeded baseline levels at 2 and 6 weeks, respectively. Rest MMA remained unchanged.

Reliable measurement of incisal bite force for understanding the control of masticatory muscles

OBJECTIVE

In the present study, we aimed at evaluating the steadiness of incisal bite force during isometric contractions of masticatory muscles.

DESIGN

Two separate experiments were carried out in 11 healthy young women. A first experiment was performed to test the reliability of our protocol for measurement of incisal bite force steadiness. The second experiment aimed to evaluate the steadiness of incisal bite force at four submaximal (i.e., percentage of maximum voluntary contraction, MVC) levels (5 %MVC, 10 %MVC, 15 %MVC, and 20 %MVC), along with the bilateral myoelectric activity of two masticatory muscles (temporalis and masseter).

RESULTS

The results from the first experiment showed that our protocol is substantially reliable (intraclass correlation coefficient, ICC > 0.80) for estimating force variability and moderate reliable (0.60 < ICC < 0.80) for estimating spectral properties of force signals. In the second experiment, we found that force standard deviation (SD) increased proportionally to the power of mean force, and coefficient of variation (CoV) was higher at low-intensity contractions and maintained at an approximately constant level for high-intensity contractions. The force-EMG relationships were linear for both muscles at the contraction intensities evaluated in the study (5 %MVC to 20 %MVC), and the median frequency did not change with contraction intensity.

CONCLUSION

Therefore, we presented a reliable method to estimate the incisal bite force, along with additional data on force control and myoelectric activity of jaw elevator muscles during isometric steady contractions.

Alterations in Surface Electromyography Are Associated with Subjective Masticatory Muscle Pain

Background

Tenderness of masseters and temporalis can be considered a relevant tool for diagnosis of myo-type craniofacial pain disorders, but a limit of pain score systems is that they are based on subjective pain perception. Surface electromyography (sEMG) is a noninvasive and reliable tool for recording muscle activity. Therefore, we investigated whether a correlation exists between tenderness on masseters and temporalis, assessed by subjective pain scale, and muscles activity, evaluated by sEMG, in patients with painful temporomandibular disorder (TMD) and concurrent tension-type headache (TTH).

Methods

A cross-sectional study on fifty adult volunteer patients with TMD and TTH, who underwent tenderness protocol according to Diagnostic Criteria for TMD (DC/TMD) guidelines, was conducted followed by sEMG recording of temporalis and masseters. Pearson's correlation was performed to investigate the correlation between muscular activity and subjective pain scores.

Results

An overall moderate correlation between muscle tenderness and sEMG values (y = 1 + 1.2 · x; r² = 0.62; p < 0.0001), particularly in the temporalis, was observed. Segregation of data occurred according to tenderness and sEMG values. At the highest pain score, the mean sEMG absolute value was higher at the temporalis than the masseters.

Conclusions

Our study provides evidence that subjective pain perception can be objectively quantified at a magnitude proportional to pain severity. At greater tenderness scores, higher sEMG activity at the level of temporalis could help discriminate clinically prevalent TTH versus prevalent TMD. sEMG confirms to be an accurate tool to reliably objectify the subjective perception of pain. When combined with clinical evaluation and patients' symptoms, sEMG increases diagnostic sensitivity in the field of myo-type craniofacial pain disorders. This trial is registered with NCT02789085.

In vivo prediction of temporomandibular joint disc thickness and position changes for different jaw positions

Temporomandibular joint disorders (TMD) are common dysfunctions of the masticatory region and are often linked to dislocation or changes of the temporomandibular joint (TMJ) disc. Magnetic resonance imaging (MRI) is the gold standard for TMJ imaging but standard clinical sequences do not deliver a sufficient resolution and contrast for the creation of detailed meshes of the TMJ disc. Additionally, bony structures cannot be captured appropriately using standard MRI sequences due to their low signal intensity. The objective of this study was to enable researchers to create high resolution representations of all structures of the TMJ and consequently investigate morphological as well as positional changes of the masticatory system. To create meshes of the bony structures, a single computed tomography (CT) scan was acquired. In addition, a high-resolution MRI sequence was produced, which is used to collect the thickness and position change of the disc for various static postures using bite blocks. Changes in thickness of the TMJ disc as well as disc translation were measured. The newly developed workflow successfully allows researchers to create high resolution models of all structures of the TMJ for various static positions, enabling the investigation of TMJ disc translation and deformation. Discs were thinnest in the lateral part and moved mainly anteriorly and slightly medially. The procedure offers the most comprehensive picture of disc positioning and thickness changes reported to date. The presented data can be used for the development of a biomechanical computer model of TMJ anatomy and to investigate dynamic and static loads on the components of the system, which could be useful for the prediction of TMD onset.

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

Objectives

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.

Subjects and methods

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.

Results

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).

Conclusions

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.

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 teeth-supported 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.

The Role of Stress in the Etiology of Oral Parafunction and Myofascial Pain

Oral parafunction during waking comprises possible behaviors that can be measured with a comprehensive checklist or behavioral monitoring. Multiple studies lead to largely consistent findings: stressful states can trigger parafunctional episodes that contribute to myofascial pain. However, this simple causal pathway coexists with at least 3 other pathways: anxiety and stress are potent direct contributors to pain, pain results in maladaptive behaviors such as parafunction, and parafunction may be a coping response to potential threat coupled with hypervigilance and somatosensory amplification. Awake parafunction remains an important risk factor for myofascial pain onset and overuse models alone of causation are insufficient.

Muscle activity and masticatory efficiency with bilateral extension base removable partial dentures with different cusp angles

STATEMENT OF PROBLEM

Whether masticatory efficiency and electromyographic activity are influenced by type of artificial teeth and food is unclear.

PURPOSE

The purpose of this clinical study was to evaluate the influence of extension base removable partial dentures (RPDs) with different cusp angles: anatomic (33 degrees), semianatomic (20 degrees), and nonanatomic (0 degrees) teeth on masticatory efficiency and muscle activity during the mastication of test foods with different textures.

MATERIAL AND METHODS

Twelve participants with RPDs were selected to perform masticatory efficiency and electromyographic tests. Surface electromyograms (EMGs) were used to record the activities of the masseter and temporalis muscles during the mastication of different types of test foods. The maximal voltage and duration were measured on the integrated EMG signal in each muscle during food mastication, and the mean reading of both sides was then recorded. Analysis of variance and the Tukey post hoc test were used to perform statistical analyses (α=.05).

RESULTS

The masticatory efficiency of RPDs with nonanatomic teeth was significantly inferior to that of RPDs with anatomic and semianatomic teeth (P<.05). However, masticatory efficiency did not differ between anatomic and semianatomic teeth (P>.05). Also, muscle activity (according to EMG) with RPDs with NA teeth was significantly higher than that with anatomic and semianatomic teeth (P<.05).

CONCLUSIONS

RPDs with NA teeth were associated with higher EMG muscle activity and reduced masticatory efficiency than anatomic or semianatomic teeth.

Effects of orofacial myofunctional therapy on masticatory function in individuals submitted to orthognathic surgery: a randomized trial

Objectives

The esthetic and functional results of orthognathic surgery of severe dentofacial deformities are predictable, however there are differences regarding the effects on stomatognathic system. The aim was to investigate the effects of orofacial myofunctional therapy (OMT) on the masticatory function in individuals with dentofacial deformity submitted to orthognathic surgery (OGS).

Material and Methods

Forty-eight individuals (18-40 years) were evaluated, 14 undergoing OMT (treated group-TG), 10 without this treatment (untreated group-UTG) and 24 in a control group with normal occlusion; for clinical aspects the data of an individual was missed (n=46). Chewing was performed using the Expanded protocol of orofacial myofunctional evaluation with scores (OMES-E). Muscle tone and mobility were also analyzed before (P0), three (P1) and six months (P2) after OGS. Surface electromyography of the masseter and temporalis muscles was performed, considering the parameters amplitude and duration of act and cycle, and the number of masticatory cycles. The OMT consisted of ten therapeutic sessions along the postoperative period. The results were compared using parametric and non-parametric tests.

Results

TG showed higher scores in P1 and P2 than P0; for the masticatory type the scores in P2 were significantly higher than P0. In addition, the proportion of individuals with adequate tone of lower lip and adequate tongue mobility for TG increased significantly from P1 and P2 in relation to P0. The EMG results showed a decrease in act and cycle duration in P2 in relation to P0 and P1 for the TG; furthermore the values were close to controls. An increase in the number of cycles from P0 to P2 was also observed, indicating faster chewing, which may be attributed to an improvement of balanced occlusion associated with OMT.

Conclusion

There were positive effects of OMT on the clinical and electromyography aspects of chewing in individual submitted to orthognathic surgery.

Short-term transcutaneous electrical nerve stimulation reduces pain and improves the masticatory muscle activity in temporomandibular disorder patients: a randomized controlled trial

Studies to assess the effects of therapies on pain and masticatory muscle function are scarce.

Comparing the Electromyographic Features of the Masseter and Temporal Muscles in Patients with full Mouth Implant-supported FDPs and Natural Dentition

BACKGROUND

Due to increasing demands for a full mouth implant reconstructions and the fact that the most failures are associated with biomechanical complications, determining the effect of different occlusal patterns on these complications seems inevitable. The aim of this study is to compare affection of different occlusal designs in full mouth implant reconstructed patients on electromyographic activity of temporal and masseter muscles compared to natural dentition.

METHODS

Thirty-two patients were included in this study, considering that 16 patients had natural dentition and the other 16 were full mouth implant reconstruction patients. In both groups, the participants were divided into two subgroups: 8 patients had canine guidance occlusal pattern and the other eight had a group function occlusal pattern. Muscle contractions were studied during both maximum intercuspation and lateral excursions to the point of intercanine contact using an electromyography device.

RESULTS

The average percentages of masseter muscle contraction in lateral excursions relative to maximum intercuspation were as follows: 72.20% in full mouth implant reconstruction patients with group function occlusion 69.49% in natural dentition with group function occlusion 58.85% in full mouth implant reconstruction patients with canine guidance occlusion 30.91% in natural dentition with canine guidance occlusion. The average percentages of temporal muscle contraction in lateral excursions relative to maximum intercuspation were as follows: 70.87% in full mouth implant reconstruction patients with group function occlusion 78.57% in natural dentition with group function occlusion 51.99% in full mouth implant reconstruction patients with canine guidance occlusion 31.55% in natural dentition with canine guidance occlusion.

CONCLUSION

A canine guidance occlusal pattern in both, natural dentition and full mouth implant-supported FDP, patients resulted in decreased muscle contraction. This decreasing is more significant in natural dentition and it is better to establish a canine guided occlusion in a full mouth reconstruction patient.

Influence of time and different tooth widths on masticatory efficiency and muscular activity in bilateral free-end saddles

PURPOSE

To evaluate the influence of time on masticatory efficiency and muscular activity during mastication of different types of test foods in participants fitted with a lower bilateral free-end saddle removable partial denture (RPD) with wide or narrow teeth.

METHODS

Thirty-six participants consented to undergo evaluation of their masticatory efficiency and recording of their muscular activity, while they wore an RPD with a unified bilateral design, during mastication of different types of test foods. The width of the artificial teeth was changed as follows. Initially (A), the length was adjusted so that the distal end of the mandibular second molars occluded with the distal end of the maxillary second molar (buccolingual width of 7-8 mm). Next (B), the width was decreased to half the maxillary second molars (buccolingual width of only 5 mm). A statistical analysis was performed using SAS software. One-way analysis of variance (ANOVA) was performed followed by Duncan's multiple range tests.

RESULTS

At the 2-month follow-up visit, wider teeth demonstrated greater masticatory efficiency than narrower teeth. However, after 4 months, no significant differences were observed between the two tooth widths. No significant differences in muscular activity were observed.

CONCLUSION

A reduction of the occlusal table width in free-end saddle RPDs resulted in decreased masticatory efficiency 2 months after denture fabrication, but there was no significant difference in muscular activity between narrow and wide teeth. However, after 4 months, the masticatory efficiency of the participants with narrower teeth improved without any changes in muscular activity.

Masticatory efficiency and muscular activity in removable partial dental prostheses with different cusp angles

STATEMENT OF PROBLEM

The loss of posterior teeth has a negative effect on the masticatory efficiency and activity of mastication muscles. How these muscles are affected by partial removable dental prostheses (PRDPs) with different cusp angles is unknown.

PURPOSE

The purpose of this clinical study was to evaluate the influence of different cusp angles, with anatomic (33 degrees), semianatomic (20 degrees), and nonanatomic teeth (0 degree), on the masticatory efficiency and muscular activity of participants receiving mandibular bilateral distal PRDPs.

MATERIAL AND METHODS

Fifteen participants consented to the evaluation of masticatory efficiency and electromyographic (EMG) activity with a PRDP with a unified bilateral design. The cusp angles of the artificial teeth were randomly changed from anatomic (33 degrees), semianatomic (20 degrees), and nonanatomic teeth (0 degree). Masticatory efficiency was evaluated by recording 5 parameters, including number of strokes, and time of mastication while the EMG activities of the masseter and temporalis muscles, measured using surface electromyography. The data were analyzed with 1-way ANOVA and the Tukey multiple post hoc test with statistical software (α=.05).

RESULTS

With regard to masticatory efficiency, PRDPs with anatomic and semianatomic teeth exhibited higher masticatory efficiency than those with nonanatomic teeth, whereas no significant differences were found between PRDPs with anatomic and semianatomic teeth. With respect to EMG activity, the least EMG activity was observed in PRDPs with anatomic teeth, whereas the highest activity was observed with nonanatomic teeth. No significant differences were found between the effect of PRDPs with anatomic and semianatomic teeth on masseter activity.

CONCLUSIONS

Changing the cusp angle from 33 to 20 degrees in PRDPs did not influence the masticatory efficiency or the EMG activity of the masseters. However, it did lead to increased EMG activities of the temporalis muscle. PRDPs with nonanatomic teeth were associated with a significant decrease in masticatory efficiency accompanied by a significant increase in EMG activity.

Uses of electromyography in dentistry: An overview with meta-analysis

OBJECTIVE

The purpose of this study was to review the uses of electromyography (EMG) in dentistry in the last few years in related research. EMG is an advanced technique to record and evaluate muscle activity. In the previous days, EMG was only used for medical sciences, but now EMG playing a tremendous role in medical as well as dental sector.

MATERIALS AND METHODS

Several electronic databases such as Google Scholar, PubMed, Science Direct, and Web of Science were systematically searched for studies published until July 2015.

RESULTS

EMG can be used in both diagnosis and treatment purpose to record neuromuscular activity. In dentistry, we can utilize EMG to evaluate muscular activity in function such as chewing and biting or parafunctional activities such as clenching and bruxism. In case of TMJ and myofascial pain disorders, EMG widely is used in the last few years.

CONCLUSIONS

EMG is one of biometric tests that occur in the modern evidence-based dentistry practice.

Electromyography assessment in zygomaticomaxillary complex fractures

OBJECTIVE

The aim of this study was to assess the activity of the masseter and temporalis muscles using surface electromyography (EMG) in patients with zygomaticomaxillary complex (ZMC) fractures.

PATIENTS AND METHODS

This prospective study was carried out on 25 patients who had ZMC fractures. Fifteen patients were managed by open reduction and rigid fixation (ORIF) using titanium miniplates. This study, using surface electromyography, analyzed the activity of the masseter and temporalis muscles of 25 patients with ZMC fractures; 15 of them were surgically treated under general anesthesia (GA). Evaluations were made before surgery and 6 weeks after surgery by recording the mean of muscle contraction of 20 motor unit action potential (MUAP) against resistance, and statistical analyses were performed.

RESULTS

A significant EMG difference between the normal and ZMC fracture sides was found (P < 0.0001) for both masseter and temporalis muscles and was significantly improved after ORIF. However, postoperative EMV values of the repaired side was significantly less than measured postoperatively in the normal side (P < 0.0001) for both muscles.

CONCLUSION

ZMC fractures significantly diminish muscular activity of the masseter and temporalis and even though significant recovery of muscle activity was revealed after 6 weeks, it is still less than normal activity, highlighting the importance of postoperative rehabilitation.

A prospective cross-over study to evaluate the effect of two different occlusal concepts on the masseter muscle activity in implant-retained mandibular overdentures

BACKGROUND

The purpose of this prospective cross-over study is to evaluate the effect of bilateral balanced occlusion and canine guidance occlusion on the masseter muscle activity using implant-retained mandibular overdentures.

METHODS

After evaluation of 12 completely edentulous patients using cone beam computed tomography (CBCT), mucoperiosteal flaps were reflected exposing the mandibular interforaminal region. Two implants were placed in the interforaminal region for each of the 12 patients. After a healing period of 3 months, acrylic maxillary complete dentures and mandibular overdentures were fabricated with bilateral balanced occlusion for 6 patients and canine guidance occlusion for the other 6 patients. Electromyographic evaluation of the masseter muscles, during clenching on a silicon index and chewing peanuts and cake, was conducted on the patients after using their dentures for 4 weeks. Each occlusion concept was then converted into the other concept using the same dentures, and the procedure of evaluation was repeated after 4 weeks. The recordings were analyzed statistically using Wilcoxon signed ranks test. p < 0.05 was considered statistically significant.

RESULTS

The highest electromyographic activity of the masseter muscles was recorded during clenching on a preformed silicon index followed by chewing peanut then cake for both occlusal concepts. The recordings of the masseter muscle associated with canine guidance occlusion were higher than bilateral balanced occlusion but with no statistically significant difference except between the right masseter muscles during clenching (p = 0.042*).

CONCLUSIONS

Both bilateral balanced occlusion and canine guidance occlusion can be used successfully in implant-retained mandibular overdentures without affecting masseter muscle activity.

Association between facial growth pattern and facial muscle activity: A prospective cross-sectional study

OBJECTIVE

To evaluate the relationship between facial growth pattern and electromyography (EMG) of facial muscles: anterior temporalis, masseter, buccinators, orbicularis oris, mentalis and anterior digastric.

PATIENTS AND METHODS

The sample consisted of 77 subjects aged between 18-28 years (mean age 21.10±2.03), with dental Class I relationship, normal overjet and overbite, balanced facial profile, no signs of temporomandibular disorders, and no previous orthodontic treatment. Facial growth pattern was determined on the lateral cephalograms according to the Björk sum (sum of the N-S-Ar, S-Ar-Go, and Ar-Go-Me angles) dividing the sample into three groups: horizontal facial pattern group (24 subjects), normal facial pattern group (41 subjects), and vertical facial pattern group (12 subjects). The EMG of anterior temporalis, masseter, buccinator, orbicularis oris, mentalis and anterior digastric muscles were examined for each patient in the rest position and in functional positions (central maximum intercuspation, chewing on right side, chewing on left side and swallowing). Mean values and standard deviation of EMG were obtained and compared between the three groups.

RESULTS

At rest, the EMG of the masseter, orbicularis oris and anterior digastric were higher in the vertical facial pattern group compared with the other two groups, with a moderate positive correlation between the EMG of these muscles and the Björk sum (P<.01). In contrast, during central maximum intercuspation, the activity of the anterior temporalis, masseter and buccinator was significantly lower in the vertical facial pattern group compared with the two other groups, with a moderate negative correlation between the Björk sum and EMG in the maximum central intercuspation position of these muscles (P<.01).

CONCLUSIONS

A significant relationship was found between facial muscle activity and facial growth pattern. The findings suggest that the activity of masticatory and perioral muscles could play a role in the direction of the facial growth.

Electromyographic and patient-reported outcomes of a computer-guided occlusal adjustment performed on patients suffering from chronic myofascial pain

Objectives: Muscular hyperactivity is a potential source of symptoms in patients with temporal-mandibular disorders. An adequate occlusal adjustment may relieve such symptoms. This study aims to measure the effect of shortening the protrusive disclusion time (DT) and balancing the center of occlusal forces (COF) on the EMG recordings and assess the pain reported by chronic patients one month after the computer-guided occlusal adjustment. Study Design: The sample studied comprised 34 patients suffering from chronic facial pain in which the EMG activity of both masseters was recorded by electromyography. By selective grinding we alleviated all the occlusal interferences during the mandibular protrusion from the habitual closure position in order to establish an immediate posterior disclusion and an equilibration of the COF. Results: At follow-up 76.5% of the patients reported no facial pain. Moreover, the EMG activity and protrusive DT were significantly reduced, and occlusal and muscular function were significantly more symmetric than at baseline. Conclusions: According to this EMG study, this computer-guided occlusal adjustment is able to reduce the activity of the masseters and the self-reported muscular pain of patients one-month after treatment.

Key words:Myofascial pain, occlusal adjustment, electromyography, T-Scan III, occlusal interferences.