Jaw muscle activity patterns in women with chronic TMD myalgia during standardized clenching and chewing tasks

Chewing Analysis by Means of Electromagnetic Articulography: Current Developments and New Possibilities

Chewing is a complex procedure that involves sensory feedback and motor impulses controlled by the trigeminal system in the brainstem. The analysis of mandibular movement is a first approximation to understanding these mechanisms. Several recording methods have been tested to achieve this. Video, ultrasound, the use of external markers and kinesiographs are examples of recording systems used in research. Electromagnetic articulography is an alternative method to those previously mentioned. It consists of the use of electromagnetic fields and receiver coils. The receiver coils are placed on the points of interest and the 3D coordinates of movement are saved in binary files. In the Oral Physiology Laboratory of the Dental Sciences Research Center (Centro de Investigación en Ciencias Odontológicas-CICO), in the Faculty of Dentistry at the Universidad de La Frontera (Temuco, Chile) several research studies have been carried out using the AG501 3D EMA articulograph (Carstens Medizinelektronik, Lenglern, Germany). With this device, they developed a series of protocols to record mandibular movement and obtain new information, such as the 3D Posselt polygon, the area of each polygon, individualized masticatory cycles and speed and acceleration profiles. Other investigations have analyzed these parameters, but separately. The AG501 allows for holistic analysis of all these data without altering natural movement. A limitation of this technology is the interference generated by its metallic elements. The aim of the present work is to show the developed methods used to record mandibular movement in the CICO, using the AG501 and compare them with others used in several research studies.

Orthodontics and Temporomandibular Disorders: An Overview

The relationship between orthodontics and temporomandibular disorders (TMDs) constitutes a subject of paramount significance in dental and craniofacial health. This abstract embarks upon an in-depth examination of the intricate connection between orthodontic practices and TMD, primarily focusing on evaluating the impact of orthodontic treatment modalities on the health and functionality of the temporomandibular joint (TMJ). This exploration elucidates the multifaceted interplay between orthodontic interventions and TMD by traversing a landscape of scholarly research and empirical investigations. The review draws from a broad spectrum of studies to analyze the potential influence of orthodontic treatments, which encompass occlusal adjustments and alterations in jaw positioning, on the development and management of TMD symptoms. The inquiry delves into the diverse range of TMD conditions, considering the implications of orthodontic techniques on occlusal stability, condylar alignment, and overall TMJ function. Through a comprehensive synthesis of the available body of knowledge, this abstract aspires to equip dental practitioners, orthodontists, and researchers with a nuanced understanding of the complex dynamics that govern the relationship between orthodontics and TMD. This knowledge, in turn, offers a foundation for informed clinical decision-making and the formulation of effective treatment strategies for patients presenting with TMD symptoms. By shedding light on the intricate interactions between orthodontic procedures and TMJ health, this abstract contributes to the advancement of clinical practices, promoting improved patient outcomes and well-being in the context of both orthodontics and TMDs.

Masticatory Function in Individuals with Temporomandibular Disorders: A Systematic Review and Meta-Analysis

The literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol in the PubMed, Cochrane Library, LILACS, EBSCO, Scielo, between 2012 and 2022. The methodological quality was assessed by using the Newcastle-Ottawa Study Quality Assessment Scale. Mean differences and 95% confidence intervals were calculated and combined in meta-analyses. A total of 1202 participants were included in this systematic review (690 with TMD; 512 without TMD), with 22 articles being included in the qualitative analysis. Only three studies enabled the comparative analysis of the results. Ten articles showed a high methodological quality and a low risk of bias, and twelve had a low methodological quality and an increased risk of bias. The meta-analysis showed that the differences between the intervention and control groups were not statistically significant for the percentage overlapping coefficient of the anterior temporal muscle, for the masseter, and for the torque coefficient. The parameters analyzed with the compound technique for chewing showed altered mandibular functions in individuals with TMD. With the EMG method, it was possible to suggest that TMD in adult individuals causes compensatory muscle behaviors, and several changes in the masticatory function were found.

Surface electromyography in the assessment of masticatory muscle activity in patients with pain-related temporomandibular disorders: a systematic review

Background

Temporomandibular disorders (TMD) are a set of painful conditions affecting the orofacial region that are prevalent and constitute the most frequent type of non-dental pain complaint in the maxillofacial area. Pain-related TMD (TMD-P) is characterized by ongoing pain in the masticatory muscles, the temporomandibular joint, or surrounding structures. Due to the multiple factors that contribute to the development of this condition, it can be challenging to accurately diagnose. One of the useful method for assessing patients with TMD-P is surface electromyography (sEMG). The aim of this systematic review was to provide a comprehensive overview of the current scientific literature on the evaluation of masticatory muscle activity (MMA) in individuals diagnosed with TMD-P, through the utilization of sEMG.

Methods

To gather relevant information, electronic databases such as PubMed, Web of Science, Scopus, and Embase were searched using specific keywords including: "pain" AND ("temporomandibular disorder*" OR "temporomandibular dysfunction*") AND "surface electromyography" AND "masticatory muscle activity." The inclusion criteria were studies assessing MMA in patients with TMD-P using sEMG. The Effective Public Health Practice Project (EPHPP) Quality Assessment Tool for Quantitative Studies was utilized to evaluate the quality of the studies that were included in the review.

Results

The search strategy identified 450 potential articles. Fourteen papers met the inclusion criteria. Global quality rating for significant part of the articles was weak. Most studies showed greater sEMG activity of the masseter (MM) and temporal anterior (TA) muscles at rest in TMD-P subjects than in the asymptomatic controls, while the MM and TA muscles were less active in the pain-related TMD group compared to the non-TMD group during maximal voluntary clenching (MVC).

Conclusion

There were differences in MMA in the TMD-pain population compared to a healthy control group during various tasks. The diagnostic efficacy of surface electromyography in assessing individuals with TMD-P remains unclear.

Masticatory Myoelectric Side Modular Ratio Asymmetry during Maximal Biting in Women with and without Temporomandibular Disorders

There is no consensus on the role of electromyographic analysis in detecting and characterizing the asymmetries of jaw muscle excitation in patients with temporomandibular disorders (TMD). To analyze the TMD patients (n = 72) in comparison with the healthy controls (n = 30), the surface electromyography (sEMG) of the temporalis anterior muscle (TA) and masseter muscle (M) was recorded while a maximal biting task was performed. The differences in the asymmetry of the relationship between the masseter muscles were assessed in a module to determine the sensitivity (Sn) of binomial logistic models, based on the dominance of the TA or the M muscle, in accurately predicting the presence of TMD. All assumptions were met, and comparisons between the groups showed significant differences for the TA muscle ratio (p = 0.007), but not for the M muscle ratio (p = 0.13). The left side was predominant over the right side in the TMD group for both the TA (p = 0.02) and M muscles (p = 0.001), while the non-TMD group had a higher frequency of the right side. Binary logistic regression showed a significant model (χ² = 9.53; p = 0.002) for the TA muscle with Sn = 0.843. The model for the M muscle also showed significance (χ² = 8.03; p = 0.005) with Sn = 0.837. The TMD patients showed an increased TA muscle ratio and asymmetry of left dominance, compared to the healthy subjects. Both of the binomial logistic models, based on muscle dominance TA or M, were moderately sensitive for predicting the presence of TMD.

Is there an association between EMG activity and temporomandibular disorders during orthotic mandibular advancement in sleep apnea patients undergoing DISE?

OBJECTIVE

To detect whether myotatic reflex activation of masticatory muscles during drug-induced sleep endoscopy (DISE) can be an indirect marker for temporomandibular disorder (TMD) in patients suffering from obstructive sleep apnea (OSA).

METHODS

OSA patients were prospectively recruited and underwent a complete TMD examination prior to undergoing DISE with the addition of electrodes applied over masticatory muscles. A positive activation of myotatic reflex was considered in case of an increase in muscle tone of at least 50%.

RESULTS

Of the 41 patients included, 48.8% presented activation of myotatic reflex. Of these patients, 45% presented a TMD diagnosis, 40% presented pain at masticatory muscles palpation, and 15% did not report pain during clinical examination.

CONCLUSION

An increase in EMG activity during mandibular advancement is not associated with TMD presence, but it can be an indirect marker of pain in the orofacial area in OSA patients.

Association between masticatory muscle activity and oral conditions in young female college students

The purpose of this study was to determine the characteristics of masticatory muscle activity and various oral condition factors, and to analyze their associations in order to improve the prevention and diagnosis of masticatory muscle-related diseases. This study included 30 Korean females (mean age of 20 years, age range of 19-21 years). Participants were instructed to complete a self-written questionnaire on factors that may affect their muscle activity. Surface electromyography was used to measure the activity of the masseter and temporalis muscles. We also observed the buccal mucosa ridge, tongue indentation, tooth cracks and fractures, and mandibular tori in the oral cavity. Spearman correlation analysis and the nonparametric Mann-Whitney U test were applied to the data. When subjects had temporomandibular disorder, the right temporalis muscle exhibited significantly lower activity (P<0.05). Those who had received orthodontic treatment within the previous 2 years showed significantly lower activity of the left masseter muscle (P<0.05). Those who had a left buccal mucosa ridge exhibited lower activity of the left masseter muscle and higher activity of the right temporalis muscle compared with those without such a ridge (P<0.05). Participants with no tongue indentation showed significantly higher activity in the left masseter muscle (P<0.05). These results indicate that there are relationships between masticatory muscle activity and various factors related to the oral condition.

The intensity of awake bruxism episodes is increased in individuals with high trait anxiety

OBJECTIVES

Trait anxiety is associated with an increased occurrence of awake bruxism episodes, a behavior characterized by clenching of the teeth contributing to temporomandibular disorders in some individuals. Here we measured the activity of the masseter and the intensity and duration of spontaneous wake-time tooth clenching episodes in healthy individuals with different levels of trait anxiety (TA).

MATERIALS AND METHODS

Two hundred fifty-five individuals completed a web survey. Using their TA scores, we allocated them in low (< 20^th percentile of the TA score distribution), intermediate (between 20^th and 80^th ), and high (> 80^th) TA groups. We analyzed the electromyographic (EMG) activity of the right masseter during a 15-min silent reading task in forty-three individuals with low (n = 12), intermediate (n = 17), and high TA (n = 14). We tested between-group differences in EMG activity of the masseter, as well as postural activity-the muscular activity that maintains mandibular posture, and amplitude and duration of spontaneous tooth clenching episodes.

RESULTS

The activity of the masseter (mean ± SEM %maximum voluntary contraction/MVC) was greater in the high TA (10.23 ± 0.16%MVC) than the intermediate (8.49 ± 0.16%MVC) and low (7.97 ± 0.22%MVC) TA groups (all p < 0.001). Postural activity did not differ between groups (all p > 0.05). The EMG amplitude of tooth clenching episodes was greater in the high TA (19.97 ± 0.21 %MVC) than the intermediate (16.40 ± 0.24%MVC) and low (15.48 ± 0.38 %MVC) TA groups (all p < 0.05). The cumulative duration of clenching episodes was not different between groups (p = 0.390).

CONCLUSIONS

Increased TA is associated with both increased masseter muscle activity and intensity of wake-time tooth clenching episodes.

CLINICAL RELEVANCE

TA may contribute significantly to masticatory muscle overload.