Comparative analysis of myoelectric activity and mandibular movement in healthy and temporomandibular disorder subjects

doi:10.21203/rs.3.rs-4283713/v1

Objectives: Temporomandibular disorders (TMD) are one of the leading causes of craniofacial pain, and a high incidence of TMD in young adults has been reported. Previous studies have used surface electromyography (sEMG) and mandibular kinematic analysis to diagnose TMD. This study aimed to provide normal reference values of sEMG and mandibular kinematics in Chinese young adults, compare the sex differences and assess the diagnosis value of these indices.

Materials and methods: This was an observational study that 90 healthy young adults (49 women and 41 men) with individual normal occlusion were strictly selected by diagnosis standard, and 26 TMD patients with disc displacement (13 with reduction and 13 without reduction) were recruited. The sEMG signals of the anterior temporalis (TA), masseter (MM), and sternocleidomastoid and digastric were recorded in the mandibular postural positions (MPP) and during maximal voluntary clenching (MVC) with K7 electromyograph. Mandibular kinematics, including maximum opening and opening/closing velocities, were assessed by K7 kinesiograph.

Results: In healthy subjects, the sEMG reference values ranged from 3.0 to 4.3 μV in the MPP. The sEMG values during MVC, maximum opening, and opening velocity were significantly higher in males than in females, and also these indices showed good diagnostic efficiency for articular TMD.

Conclusions: Reference values and sex differences in sEMG and mandibular kinematics in healthy subjects were determined. Compared with them, TMD patientsshowed significantly lower myoelectric activity during maximal biting and restricted mouth opening range and velocity, which may assist in TMD diagnosis.

Clinical relevance: By analyzing sEMG of masticatory muscle and mandibular kinematics data from healthy Chinese young adults and TMD patients with disc displacement, this study evaluated the sex difference and diagnosis value of these indices for TMD.

Clinical Trial Registration ID: NCT06372769

Temporomandibular joint disorder

surface electromyography

mandibular kinematics

sex difference

diagnosis.

Temporomandibular disorders (TMD) constitute a group of symptoms that involve pain and tenderness in the masticatory muscles or temporomandibular joint (TMJ), limitation of jaw movement, and joint noise during mouth opening/closing [1]. A high morbidity rate of TMD was reported, in which over 50% of normal people were prone to have one or more symptoms, and approximately 5%-9% had severe symptoms [2].

Surface electromyography (sEMG) has been used in the study of functional jaw muscle anatomy since the 1950s [3]. It is an objective and accurate tool to assist the diagnosis of muscular dysfunction than palpation and visual observation [4]. Healthy people can relax jaw muscles at rest and tense muscle groups in a coordinated way, while the abnormal electromyographic signal can be collected from TMD patients with muscle pain/dysfunction [5]. Further, the asymmetric sEMG activity also offers a valuable reference for the diagnosis of TMD and evaluation of the therapeutic effect of TMD treatment [6,7].

In addition, the association between mandibular kinematics and muscular diagnoses has been studied, and approximately 97% of TMD patients with mandibular dysfunction have at least one muscular diagnosis, including protective co-contraction, myofascial pain, myospasm, or myalgia [8]. To our knowledge, mandibular kinematic values are also related to specific articular diagnoses. For example, abnormal mouth opening, obvious deviation, limited mandibular maximum excursions, and bony end-feel may be observed in TMD patients with disc displacement, subluxation, or retrodiscitis [9]. In brief, muscle or joint symptoms directly or indirectly affect normal mandibular movement [10].

Establishing normal reference values is a significant step toward diagnosing and treating TMD [11,12]. It was found that the susceptibility of certain joint derangements or the awareness of pain differs among ethnic groups, and such differences refer to a genetic difference in the stomatognathic system that affects the prevalence of TMD [13]. However, there is a lack of quantitative and comprehensive analysis of sEMG activity and mandibular movement in Chinese young adults with normal occlusion. Although many investigators have studied the effect of sex on TMD, which involves psychosocial, hormonal, and genetic factors [14], the results were controversial. Moreover, whether sEMG and mandibular kinematic analysis can be effectively used for the diagnosis of non-painful articular TMD remains unclear.

Ninety young adults in the high-risk age group of TMD and twenty-six TMD patients with disc displacement were recruited in this observational study. The non-invasive measurements of sEMG and mandibular movement made it possible to provide certain clinical references for TMD diagnosis and compare the sex differences in these indices. The hypothesis was sEMG activity and mandibular kinematics had a good diagnostic efficiency for TMD and their normal values in healthy subjects were significantly affected by sex.

Participants

Ninety healthy volunteers (49 women and 41 men; mean age 20.7 ± 0.7 years) wererecruited from college students of Fujian Medical University who fulfilled the following criteria: (1) centred midline and no marked restriction and deviation of mouth opening and closing; (2) overjet and overbite of 1-3 mm, bilateral molar support with molar and cusp relation of Angle’s class I, and (3) presence of complete permanent dentition, except third molars.

Healthy subjects were excluded if they met one or more of the following exclusion criteria: (1) history of local or general trauma; (2) presence of systemic diseases, neurological or psychiatric disorders, muscular diseases, cervical pain, or TMD based on the Research Diagnostic Criteria (RDC) [15];(3) pregnancy; (4) consumption of anti-inflammatory, analgesic, antidepressant, or myorelaxant drugs; (5) presence of parafunctional facets and anamnesis of parafunctional tooth clenching, bruxism, or unilateral chewing; (6) presence of obvious dentition crowding or spacing, malposed, supernumerary or fractured tooth, visible caries, tooth abrasion/hypersensitivity, toothache, periodontal disease, or occlusal discomfort; (7) fixed or removable restorations, tooth filling, or occlusal adjustment that affected the occlusal surfaces; and (8) previous or concurrent orthodontic, orthognathic, or TMJ treatment.

Twenty-six TMD participants were recruited through public invitations, via recruitment posters and personal contacts (19 women and 7 men; mean age 29.7 ± 4.8 years). Patients with unilateral or bilateral TMJ disc displacement symptoms, such as TMJ clicking, TMJ locking, and limitation in opening mouth were included in the study. The study did not cover the patients with muscle disorders (myofascial pain), with arthralgia, osteoarthritis, and osteoarthrosis, with TMJ fracture, with dentofacial deformity, with systemic disease affecting TMJ, and undergone TMD treatments. They were further divided into reversible anterior disk displacement (RADD) group (n=13) and anterior disc displacement without reduction (ADDWR) group (n=13) by magnetic resonance imaging (MRI) images.

Recruitment and tests took place from February 2022 to July 2022. All subjects received the test instructions and were randomly allocated by selecting sealed opaque envelopes before the test. The testers had no information about the allocation pattern.

Surface electromyography

The sEMG of the anterior temporalis (TA), masseter (MM), sternocleidomastoid (cervical group, CG), and digastric (DA) were recorded simultaneously with an sEMG device (K7/EMG, Myotronics-Noromed, Inc., Tukwila WA, USA) using disposable silver/silver chloride bipolar surface electrodes (Duo-Trode, Myotronics-Noromed, Inc., Tukwila WA, USA).

The tests were carried out in a quiet environment, with the subjects comfortably seated on a fixed chair with a straight back, closed eyes, and relaxed head position. The locations of the electrodes were determined by palpation of muscle contraction (Fig. 1A) [11], and the ground electrodes were positioned on the subject’s clavicle bone to provide a common reference to the differential input of the amplifier. Each recording site was thoroughly cleaned and dried, and each pair of electrodes was placed on the site over the belly of the muscle and parallel with the muscle fibers, and conductive paste was used for good electrical contact with the skin. The electrode noise test was conducted to ensure the proper connection of the K7 EMG ground wire to the patient ground electrode, proper cleansing of the skin, quality of electrodes and electrode leads, and low electrical noise caused by an electric motor. The sEMG recording was started only when the software (K7 Program 15.0, Myotronics-Noromed, Inc., Tukwila WA, USA) revealed the absence of noise.

The raw sEMG data were recorded with a sampling frequency of 2000 Hz, and all recorded signals were band-pass filtered with a high- and low-pass Hamming filter with cut-off frequencies of, respectively, 15 and 650 Hz, and an additional 60 Hz 110 dB/decade notch filter. Three consecutive tracks, with a duration of 15 seconds and without any voluntary movement, were recorded. The root mean square (RMS) value of sEMG (in μV) for each channel was displayed at the end of the tracing. First, sEMG was conducted on four pairs of muscles (TA, MM, CG, and DA) in the MPP, and subjects were guided to maintain the face and jaw as relaxed as possible (Fig. 2A) [16]. The results showed that the relative resting activity of the masticatory/cervical muscles and the motor unit activity were averaged over time to quantify the amount of electrical activity.

To determine the relative efficiency of muscle function, the second test was performed to measure the sEMG of TA and MM during the maximal biting force against natural dentition (TA-ND and MM-ND) or cotton rolls (TA-CR and MM-CR). The cotton rolls were used as standard food substitution with a length of 3.0 cm and a diameter of 1.0 mm. Each subject was asked to clench twice with maximum force, hold for 2.0 seconds, and relax for 1.0 second, followed by another clench as before after two wet cotton rolls were placed on the posterior teeth (Fig. 3A).

In the third test, subjects were guided to clench three times to monitor early motor unit recruitment as they closed from rest through freeway space to initial tooth contact. Partial asymmetry indices (PAI) at the peak sEMG values of TA and MM (pTA and pMM) were automatically generated by software (Fig. 3B), and total asymmetry indices (TAI) during maximal voluntary clenching (MVC) were calculated using the following formula to determine muscle balance. ^11,¹² For PAI and TAI, a zero value reflects similar muscle activity on the left and right sides.

Mandibular kinematics

Kinesiographic recordings were performed using a kinesiograph (K7/CMS, Myotronics-Noromed, Inc., Tukwila WA, USA) that measured mandibular movements with an accuracy of 0.1 mm in the vertical, anteroposterior (AP), and lateral axes. An array with eight magnetic sensors mounted on the subject’s head tracked the motion of the small magnet attached to the labial surface of the lower central incisor at a sample rate of 125 Hz (Fig. 1B). The maximum mouth opening (MMO) and opening and closing velocities were measured.

The first tracing was a simultaneous sagittal and frontal trace of the trajectory that the mandibular traversed during mouth opening and closing. Each subject was asked to open their mouth as wide as possible and then close it (Fig. 4A). Then they opened and closed their mouths starting from intercuspal position (ICP) and back as fast as possible, the sagittal, frontal, and velocity tracings were simultaneously recorded. Meanwhile, the maximum velocity of terminal tooth contact (MVTTC) was measured, defined as the closing speed at 0.8 mm below the centric occlusion (CO) (Fig. 4B).

All measurements were repeated twice, with a gap of 15 minutes between two recordings, and the average values were calculated. Additionally, each participant was assessed by two examiners at an interval of three days. Reliability was calculated using the intraclass correlation coefficient (ICC). The inter-and interrater reliability was calculated with ICC using the average data of each test per session.

Statistical analysis

Statistical analysis was performed using SPSS 27.0 software (IBM Corp., Armonk, NY, USA). The level of significance was set at P≤0.05 for all tests. Shapiro-Wilk and Levene tests were used to assess the normality of data and homogeneity of variance, respectively. Significant differences in sEMG values and mandibular kinematics between sexes and between healthy and TMD subjects were established by the analysis of variance (ANOVA) or the Mann‐Whitney U test for non-parametric data. Further, the receiver operator characteristic (ROC) curve was used to analyse their diagnostic efficiency for TMD, and their effect on the severity of TMD was also investigated using Spearman correlation.

Intra-interrater reliability showed high reliability being for the most part above 0.85. As shown in Table 1, there was no significant sex difference in the bilateral sEMG of the TA (L: P=0.19, R: P=0.99), MM (L: P=0.81, R: P=0.54), CG (L: P=0.98, R: P=0.77), and DA (L: P=0.05, R: P=0.63) in the MPP (Fig. 2B).

For the bilateral TA, significantly higher average sEMG values were found in males than in females during MVC with and without cotton rolls (P<0.001) (Fig 3C). Male subjects also had higher sEMG activity of the bilateral MM when clenched against cotton rolls (P<0.001). Table 2 indicates that the muscle asymmetry indices during MVC. The PAI_TAranged from 46.1% to 64.7%, PAI_MMranged from 49.6% to 65.8%, and TAI ranged from 12.7% to 19.1% in healthy subjects. No difference in PAI (TA: P=0.09, MM: P=0.58), and TAI (P=0.24) was found among sexes (Fig 3D).

Table 3 presents the range of jaw movements during MMO and the velocity of quick mouth opening/closing. Higher values of maximum vertical opening (MVO) (P<0.001), maximum AP movement from CO (MAP) (P<0.05), and linear distance from CO to maximum opening (CO-MO) (P<0.001) were found in males than in females (Fig. 4C). Additionally, the male subjects exhibited a faster opening speed according to the maximum opening velocity (MOV) and average opening velocity (AOV) (P<0.05) (Fig. 4D).

In Figure 5, although there was no significant difference in sEMG value of MPP and asymmetry index among healthy subjects and RADD and ADDWR patients, statistically higher sEMG activity of TA and MM were recorded in healthy volunteers during MVC against natural dentition and cotton rolls (P<0.001). Furthermore, RADD patients showed higher sEMG when clenched against cotton rolls than that in ADDWR patients (P<0.05). Moreover, healthy volunteers exhibited larger jaw movement range (MAP and CO-MO) and faster movement speed (MOV, AOV, MCV, and ACV) than those of TMD patients.

For ROC analysis, the area under curve (AUC) of MCV (0.95), MVO (0.90), and TA-ND (0.86) was larger than other indices. The optimal MCV cut-off level was 190.2 mm/s, which had a sensitivity and specificity of 100.0% and 82.7%, respectively. Meanwhile, MVO showed an optimal cut-off at 30.6 mm with a a sensitivity and specificity of 100.0% and 90.2%, respectively (Fig. 6).

Spearman correlation analysis showed that the severity of TMD were strongly correlated with MCV (r_s=-0.6260, P<0.001) and MVO (r_s=-0.6385, P<0.001) (Table 4). Additionally, there was a moderate correlation between TA-ND and the severity of TMD (r_s=-0.4843, P<0.001).

This study attempts to estimate reference values of sEMG activity of the jaw muscle and mandibular kinematics in healthy Chinese young adults with normal occlusion and evaluate the diagnosis efficiency of these indices for TMD. The null hypothesis was supported by the results that sex remarkably influenced the sEMG values during MVC, mouth opening, and opening velocity, which also showed good diagnostic value for TMD.

sEMG is a non-invasive tool for gathering electrical signals produced during muscular contractions, the quantitative analysis of sEMG has become a supplementary diagnostic method of TMD in recent decades [3]. The determination of normal parameters provides an important reference for the health assessment of TMJ. Ferrario et al. [12] measured the average sEMG activity of TA and MM in the MPP and ICP, and during MVC in 92 healthy Caucasian young adults with natural dentition. Similarly, Campillo et al. [11] aimed to establish normal reference values of sEMG in Spanish young adults with ideal dentition. In the present work, the average sEMG activity values in the MPP and during MVC were slightly lower than those of previous studies. Furthermore, 125 µV was regarded as the minimum threshold for physiological clenches by Cooper et al. [17], who collected bioelectronic testing data from dentists in nine countries. Although strict inclusion criteria for the participants were used, variations in experimental methodologies and population features remained among studies, including sample size, test equipment, ethnic group, and dietary habits.

TMD may cause a chronic facial pain besides headache and cervical spine disorders. The craniomandibular region and upper cervical spine are closely related in terms of anatomy, biomechanics, and neurophysiology [18]. There is a functional link between the masticatory and cervical muscles based on a trigeminal-cervical reflex [19]. The TMD patients with myalgia were reported to have higher resting sEMG activity of the sternocleidomastoid and trapezius muscles than that of healthy subjects [20]. However, only the TMD patients without pain in the facial muscle were enrolled in this study, which may explain why they did not show significant difference in sEMG value in the MPP compared with healthy volunteers. Further investigation is needed on the correlation between muscle disorders and sEMG.

In addition, significantly higher sEMG activity was recorded during MVC in males than in females, and Fogle et al [21] also found a significant association between sEMG data and sex while biting rather than resting. This can be explained by the sex differences in muscle recruitment, muscle thickness,and craniofacial morphology, and males were likely to have a higher proportion of thick type II muscle fibres and greater facial length than females [22-24].

Moreover, previous studies have shown that patients with functional disturbances in the masticatory system present decreased bite force, when compared with healthy individuals [25-28]. Although the most common cause of decreased muscle function reported accordingly is the pain of myogenic and/or arthritis, the reduced muscle activity in non-painful TMD patients may be explained by a protective activity of elevator muscles and progressive alterations in the metabolism of energy in the muscle after a chronic fatigue under high pressure. Also, Ow et al. [29] found that patients with TMD demonstrate significant variations in the values of maximal bite force at multiple repeated measures, which indicates the loss of sensory acuity in regulating the masticatory muscle function. Also, the healthy subjects presented statistically higher sEMG values of TA and MM during MVC than those in TMD patients in this work, and TA-ND showed a good diagnostic efficiency and a moderate correlation with the severity of TMD that was similar to the results of Todic’s [25] and Kogawa’s [28]study.

Prior studies have noted the importance of asymmetrical muscle activity. Higher asymmetrical indices were seen in myogenous TMD patients than in healthy participants, which would be improved by an effective treatment with occlusion splints [6,7].The asymmetrical muscle activity and the remission of symptoms may be caused by unstable occlusion brought about more prolonged pressure to the TMJ and tissue ischemia [6]. In this work, PAI_MMwas higher than PAI_TA, which may be attributed to the larger cross-sectional area and more muscle fibres of MM than TA [30]. Meanwhile, TAI ranged from 11.9% to 16.3% in healthy subjects, which was slightly larger than the results of previous studies and even TMD patients without significant difference. Therefore, the diagnostic value of asymmetrical muscle activity should be careful consideration for the wide differences among individuals and patients with muscle disorders [31]. It is more appropriate to be used in self pre- and post-control observation or combined with other diagnostic information.

Abnormal jaw movement is a prominent symptom of TMD patients [8]. Limited jaw movement was reported to be associated with acute pain in the related structures of TMJ or the adaptable protection of the musculoskeletal system against further injury in chronic TMD patients [9,10]. Although significantly larger MVO was observed in males than in females, the sex difference could be affected by many potential confounding factors, such as mandibular length [32],mandibular rotation angles [33],and the shapes of the condylar pathway [34]. Males with larger mandibles and rotation angles and longer pathways would have larger MVO than females. Moreover, TMD patients with disc displacement showed remarkably lower MVO compared with healthy subjects. However, we did not find a significantly positive correlation between TMJ disc reduction ability and mouth opening as the previous study reported, which may be due to the inadequate sample size. Therefore, to further determine RADD or ADDWR, kinesiograph should be combined with other technique (eg., computer vision) to assist clinicians when it is difficult to obtain information through MRI [35].

The significant correlation between movement velocity and intervertebral disc herniation had been described before [36], and the improvement in opening/closing velocity was used to evaluate the efficacy of myorelaxation therapy on TMD [37]. There were significant differences in opening velocity for the types of muscle fibres between the sexes [38,39], and males had a stronger lateral pterygoid muscle activity than females [40]. This can explain the reason for faster MOV and AOV in males than in females in healthy subjects. For diagnosis value, a significantly lower jaw movement velocity was recorded in TMD patients than that in healthy volunteers, and the AUC of MCV was close to 1, indicating its good predictability for disc displacement. Also, there was a strong correlation between the severity of TMD and MCV, which may offer a good reference value for the diagnosis of TMD. This result was similar to the previous study, in which TMD patients’ closing velocity during gum chewing was less compared to their control subjects and it can be ascribed to the inefficient muscle recruitment and muscle fatigue [41,42].

Lower MVTTC was found in severe than in mild periodontitis patients because of the protective co-contraction of antagonistic muscles, which was derived from a neuromuscular feedback mechanism [43]. Although the MVTTC may provide the possibility of assessing the mandible motor function, there was no significant difference between healthy subjects and TMD patients in this study. It may be related to the types of TMD and sample size, further investigation is clearly warranted.

Recording the sEMG and mandibular movement tracings with non-invasive, repeatable, and portable electronic devices is useful in assisting the clinical diagnosis of TMD. Furthermore, the normal reference ranges and sex differences in sEMG activity and kinematics may provide important information about etiological analysis and lesion positioning. However, further research on a larger sample size needs to be carried out, and the limitations are related to the possible interferences that exist in the collection of sEMG and kinematic data. The psychological factors and muscle fatigue in subjects and the weight of the EMG pre-amp and magnetic sensors have a potential risk of bias.

Reference values for sEMG of the jaw muscles and the mandible kinematics were determined in healthy Chinese young adults with normal occlusion.
Sex differences were evident in the sEMG of the anterior temporalis and masseter during maximal voluntary clenching. Significantly higher maximum vertical opening and opening velocity values were found in males than in females.
Maximal closing velocity, maximal vertical opening, and sEMG of the anterior temporalis during maximal voluntary clenching may provide a good diagnostic value for temporomandibular joint disc displacement.

Acknowledgement

Thanks to all the volunteers who participated in the study.

Funding information

This study has been funded by the Science and Technology Innovation Joint Project of Fujian Province (Grant No. 2018Y9103) and the Medical Innovation Project, Health and Family Planning Commission of Fujian Province (Grant No. 2018-CXB-12).HL. Lin designed the study. XJ. Xing, JM. Peng and XY. Wu acquired, analysed and interpreted the data. XJ. Xing and YL. Cheng drafted the manuscript, and H. Cheng and H. Yu revised it critically for important intellectual content. All authors read and approved the final manuscript.

Compliance with ethical standards

Conflicts of Interest The authors declare that they have no conflict of interest.

Ethical approval The study was conducted by the Declaration of Helsinki and approved by the Ethics Review Committee for Biomedical Research of the School and Hospital of Stomatology, Fujian Medical University (Fujian, China), with the IRB number of FJMU 2021-056.

Informed consent Written informed consent was obtained from all individual participants included in this study. No identifying information is included in this article.

Kraus S (2007) Temporomandibular Disorders, Head and Orofacial Pain: Cervical Spine Considerations. Dent Clin N Am 51:161-193. https://doi.org/10.1016/j.cden.2006.10.001.
Köhler AA, Helkimo AN, Magnusson T, et al (2009) Prevalence of symptoms and signs indicative of temporomandibular disorders in children and adolescents. A cross-sectional epidemiological investigation covering two decades. Eur Arch Paediatr Dent 10(1):16-25. https://doi.org/10.1007/BF03262695.
Yemm R (1969) Masseter muscle activity in stress: adaptation of response to a repeated stimulus in man. Arch Oral Biol 14(12):1437-1439. https://doi.org/10.1016/0003-9969(69)90262-3.
Widmalm SE, Lee YS, McKay DC, et al (2007) Clinical Use of Qualitative Electromyography in the Evaluation of Jaw Muscle Function: A Practitioner's Guide. Cranio;25(1):63-73. https://doi.org/10.1179/crn.2007.011.
Okeson JP (2003) Management of Temporomandibular Disorders and Occlusion. J Prosthodont 12(3):230-236. https://doi.org/10.1016/S1059-941X(03)00131-1
Scopel V, Alves da Costa GS, Urias D, et al (2005) An electromyographic study of masseter and anterior temporalis muscles in extra-articular myogenous TMJ pain patients compared to an asymptomatic and normal population. Cranio 23(3):194-203. https://doi.org/10.1179/crn.2005.028.
Ferrario VF, Sforza C, Tartagila GM, et al (2002) Immediate effect of a stabilization splint on masticatory muscle activity in temporomandibular disorder patients. J Oral Rehabil 29:810-815. https://doi.org/10.1046/j.1365-2842.2002.00927.x.
Maulén-Yáñez M, Meeder-Bella W, Videla-Jiménez RJ, et al (2019) Assessment of association between muscular diagnosis in temporomandibular disorders with mandibular kinematics. Cranio 37(6):1-9. https://doi.org/10.1080/08869634.2018.1465513.
Leissner O, Maulén-Yáñez M, Meeder-Bella W, et al (2021) Assessment of mandibular kinematics values and its relevance for the diagnosis of temporomandibular joint disorders. J Dent Sci 16:241-248. https://doi.org/10.1016/j.jds.2020.05.015.
Zhang YX, Shao S, Zhang JL, et al (2017) Temporal summation and motor function modulation during repeated jaw movements in patients with temporomandibular disorder pain and healthy controls. Pain 2017;158:1272-1279. https://doi.org/10.1097/j.pain.0000000000000911.
Campillo B, Martín C, Palma JC, et al (2017) Electromyographic activity of the jaw muscles and mandibular kinematics in young adults with theoretically ideal dental occlusion: Reference values. Med Oral Patol Oral Cir Bucal 22(3):e383-391. https://doi.org/10.4317/medoral.21631.
Ferrario VF, Sforza C, Mianijr A, et al (1993) Electromyographic activity of human masticatory muscles in normal young people. Statistical evaluation of reference values for clinical applications. J Oral Rehabil 20:271-280. https://doi.org/10.1111/j.1365-2842.1993.tb01609.x.
Wu N, Hirsch C, et al (2010) Temporomandibular Disorders in German and Chinese Adolescents. J Orofac Orthop 71(3):187-198. https://doi.org/10.1007/s00056-010-1004-x.
Oakley M, Vieira AR, et al (2008) The many faces of the genetics contribution to temporomandibular joint disorder. Orthod Craniofac Res 11:125-135. https://doi.org/10.1111/j.1601-6343.2008.00426.x.
Schiffman E, Ohrbach R, Truelove E, et al (2014) Diagnostic criteria for temporomandibular disorders (DC/TMD) for clinical and research applications: recommendations of the international RDC/TMD consortium network and orofacial pain special interest group. J Oral Facial Pain Headache 28:6-27. https://doi.org/10.11607/jop.1151.
Al-Nakkash WA, Al-Ani FS, ZS Al-Fehaidi, et al (2005) Electromyographic evaluation of the activity of masseter and anterior fibers of temporalis in mandibular rest position. J College Dentistry 17(2):13-16. https://doi.org/10.1002/1096-8644(200008)112:43.0.CO;2-4
Cooper BC (2004) Parameters of an optimal physiological state of the masticatory system: the results of a survey of practitioners using computerized measurement devices. Cranio 22(3):220-233. https://doi.org/10.1179/crn.2004.027.
Armijo-Olivo S, Magee DJ, Thie NMR, et al (2006) The association between head and cervical posture and temporomandibular disorders: A systematic review. J Orofac Pain 20(1):9-23. https://doi.org/
Palla S., Farella M (2010) Muscle Pain: Diagnosis and Treatment. Springer, Berlin.
Pallegama RW, Ranasinghe AW, Weerastinghe VS, et al (2004) Influence of masticatory muscle pain on electromyographic activities of cervical muscles in patients with myogenous temporomandibular disorders. J Oral Rehabil 31:423-429. https://doi.org/10.1111/j.1365-2842.2004.01266.x.
Fogle LL, Glaros AG, et al (1995) Contributions of facial morphology, age, and gender to EMG activity under biting and resting conditions: A canonical correlation analysis. J Dent Res 74(8):1496-1500. https://doi.org/10.1177/00220345950740081001.
Pradhan A, Malagon G, Lagacy R, et al (2020) Effect of age and sex on strength and spatial electromyography during knee extension. J Physiol Anthropol 39:11. https://doi.org/10.1186/s40101-020-00219-9.
Chang PH, Chen YJ, Chang KV, et al (2020) Ultrasound measurements of superficial and deep masticatory muscles in various postures: reliability and influencers. Sci Rep 10:14357. https://doi.org/10.1038/s41598-020-71378-z.
Tuxen A, Bakke M, Pinholt EM, et al (1999) Comparative data from young men and women on masseter muscle fibres, function and facial morphology. Archs Oral Biol 44:509-518. https://doi.org/10.1016/s0003-9969(99)00008-4
Todic J, Martinovic B, Pavlovic J, et al (2019) Assessment of the impact of temporomandibular disorders on maximum bite force. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 163(3):274-278. https://doi.org/10.5507/bp.2019.001.
Ahlberg JP, Kovero OA, Hurmerinta KA, et al (2003) Maximal bite force and its association with signs and symptoms of TMD, occlusion, and body mass index in a cohort of young adults. Cranio 21(4):248-252. https://doi.org/10.1080/08869634.2003.11746258.
Hotta PTH, Hotta TH, Bataglion C, et al (2008) Bite force in temporomandibular dysfunction (TMD) and healthy complete denture wearers. Braz Dent J 19(4):354-357. https://doi.org/10.1590/s0103-64402008000400012.
Kogawa EM, Calderon PS, Lauris JRP, et al (2006) Evaluation of maximal bite force in temporomandibular disorders patients. J Oral Rehabil 33(8):559-565. https://doi.org/10.1111/j.1365-2842.2006.01619.x.
Ow RK, Carlsson GE, Jemt T (1989) Biting forces in patients with craniomandibular disorders. Cranio 7(2):119-125. https://doi.org/10.1080/08869634.1989.11678274.
Naeije M, McCarroll RS, Weijs WA, et al (1989) Electromyographic activity of the human masticatory muscles during submaximal clenching in the intercuspal position. J Oral Rehabil 16:63-70. https://doi.org/10.1111/j.1365-2842.1989.tb01318.x.
Shan SC, Yun WH, et al (1991) Influence of an occlusal splint on integrated electromyography of the masseter muscles. J Oral Rehabil 18:253-256. https://doi.org/10.1111/j.1365-2842.1991.tb00054.x.
Lewis RP, Buschang PH, Throckmorton GS, et al (2001) Sex differences in mandibular movements during opening and closing. Am J Orthod Dentofacial Orthop 120:294-303. https://doi.org/10.1067/mod.2001.115612.
Dijkstra PU, Hof AL, Stegenga B, et al (1999) Influence of mandibular length on mouth opening. J Oral Rehabil 26:117-122. https://doi.org/10.1046/j.1365-2842.1999.00358.x.
Ingervall B (1971) Variation of the range of movement of the mandible in relation to facial morphology in young adults. Scand J Dent Rcs 79:133-140. https://doi.org/10.1111/j.1600-0722.1971.tb02003.x.
Jeon KJ, Kim YH, Ha EG, et al (2022) Quantitative analysis of the mouth opening movement of temporomandibular joint disorder patients according to disc position using computer vision: a pilot study. Quant Imaging Med Surg. 12(3):1909-1918. https://doi.org/10.21037/qims-21-629.
Spadaro A, Ciarrocchi I, Masci C, et al (2014) Effects of intervertebral disc disorders of low back on the mandibular kinematic: kinesiographic study. BMC Research Notes 7:569. https://doi.org/10.1186/1756-0500-7-569.
Gawriołek K, Azer SS, Gawriołek M, et al (2015) Mandibular function after myorelaxation therapy in temporomandibular disorders. Adv Med Sci 60:6-12. https://doi.org/10.1016/j.advms.2014.05.002.
Korfage JAM, Schueler YT, Brugman P, et al (2001) Differences in myosin heavy-chain composition between human jaw-closing muscles and supra- and infrahyoid muscles. Archs Oral Biol 46:821-827. https://doi.org/10.1016/s0003-9969(01)00042-5.
Ohnuki Y, Saeki Y, et al (2008) Jaw-opening muscle contracts more economically than jaw-closing muscle in rat. Archs Oral Biol 53:193-198. https://doi.org/10.1016/j.archoralbio.2007.09.004.
Kim TH, Kim CH, et al (2020) Correlation between mandibular morphology and masticatory muscle thickness in normal occlusion and mandibular prognathism. J Korean Assoc Oral Maxillofac Surg 46:313-320. https://doi.org/10.5125/jkaoms.2020.46.5.313.
Radke JC, Kamyszek GJ, Kull RS, et al (2019) TMJ symptoms reduce chewing amplitude and velocity, and increase variability. Cranio 37(1):12-19. https://doi.org/10.1080/08869634.2017.1365421.
Hansdottir R, Bakke M (2004) Joint tenderness, jaw opening, chewing velocity, and bite force in patients with temporomandibular joint pain and matched healthy control subjects. J Orofac Pain 18(2):108-113. https://doi.org/10.1046/j.0305-182X.2003.01233.x
Sakagama R, Kato H, et al (1996) The relationship between the severity of periodontitis and occlusal conditions monitored by the K6 Diagnostic System. J Oral Rehabil 23:615-621. https://doi.org/10.1046/j.1365-2842.1996.d01-207.x.

Table 1. The sEMG (µV) of healthy subjects in the MPP (mean and 95% C.I.)

Muscle	Total			Male			Female		P
Muscle	*Mean*		95% C.I.	*Mean*		95% C.I.	*Mean*	95% C.I.	P
LTA	3.2	2.8-3.6			3.0	2.5-3.5	3.4	2.9-4.0	0.19
RTA	3.0	2.6-3.3			3.0	2.5-3.6	3.0	2.5-3.4	0.99
LMM	3.2	2.8-3.6			3.4	2.7-4.1	3.0	2.5-3.5	0.81
RMM	3.2	2.8-3.6			3.6	2.8-4.4	2.9	2.5-3.4	0.54
LCG	3.4	2.9-3.8			3.3	2.6-4.0	3.4	2.8-4.0	0.98
RCG	3.2	2.8-3.7			3.2	2.6-3.8	3.3	2.7-3.9	0.77
LDA	4.0	3.6-4.5			4.5	3.8-5.2	3.7	3.1-4.2	0.05
RDA	4.3	3.8-4.7			4.5	3.8-5.2	4.1	3.5-4.7	0.63

MPP: Mandibular postural position; RTA/LTA: Right/Left temporalis anterior; RMM/LMM: Right/Left masseter; RCG/LCG: Right/Left sternocleidomastoid; LDA/RDA: Right/Left digastric; Independent Sample T-test or non‐parametric Mann-Whitney U-test.

Table 2: The sEMG (µV) and asymmetry indices in healthy subjects during MVC (mean values and 95% C.I.)

Test and muscle	Whole sample		Male		Female		P
Test and muscle	*Mean*	95% C.I.	*Mean*	95% C.I.	*Mean*	95% C.I.	P
Natural dentition
TA	136.9	123.9-149.9	156.2	136.3-176.1	120.9	105.0-136.9	***
MM	135.7	119.8-151.7	143.1	119.9-166.3	129.8	107.9-151.7	0.23
Cotton rolls
TA	138.3	123.5-153.2	174.4	153.5-195.2	107.0	90.3-123.6	***
MM	157.4	138.5-176.3	187.6	156.8-218.4	132.0	111.1-152.9	***
PAI
TA	55.4	46.1-64.7	44.5	33.9-55.2	62.6	49.8-75.4	0.09
MM	57.7	49.6-65.8	54.3	42.5-66.1	60.5	49.3-71.7	0.52
TAI
	14.1	11.9-16.3	13.1	10.2-16.0	15.6	12.2-19.0	0.24

MVC: Maximal voluntary clenching; TA: Temporalis anterior; MM: masseter; PAI: Partial asymmetry indices; TAI: Total asymmetry indices; *P≤0.05; **P≤0.01; ***P≤0.001.

Table 3: The maximum mouth opening (mm) and the opening/closing velocity (mm/s) (mean values and 95% C.I.)

Test and index	Whole sample		Male		Female		P
Test and index	*Mean*	95% C.I.	*Mean*	95% C.I.	*Mean*	95% C.I.	P
MMO
MVO	37.0	35.9-38.1	39.8	38.6-40.9	34.7	33.3-36.2	***
MAP	24.6	23.4-25.8	26.3	24.4-28.1	23.2	21.7-24.8	0.04*
MLD	2.8	2.2-3.3	2.7	2.1-3.4	2.8	2.0-3.5	0.62
CO-MO	44.7	43.3-46.0	47.9	46.2-49.6	42.0	40.3-43.8	***
Opening/closing velocity
MOV	199.4	186.7-212.1	218.8	197.2-240.4	183.1	169.8-196.3	0.03*
AOV	126.0	118.0-134.0	138.0	124.4-151.6	115.9	107.4-124.4	0.03*
MCV	269.1	252.6-285.7	275.7	247.7-303.7	263.6	244.1-283.2	0.62
ACV	156.3	146.4-166.1	163.4	146.8-180.1	150.3	138.8-161.7	0.19
MVTTC	52.0	44.6-59.4	60.4	47.1-73.8	44.9	37.6-52.1	0.09

MMO: Maximum mouth opening; MVO: Maximum vertical opening; MAP: Maximum anteroposterior movement from centric occlusion; MLD: Maximum lateral deviation; CO-MO: Straight-line distance from centric occlusion to maximum opening; MOV: Maximum opening velocity; AOV: Average opening velocity; MCV: Maximum closing velocity; ACV: Average closing velocity; MVTTC: Maximum velocity of terminal tooth contact. *P≤0.05; **P≤0.01; ***P≤0.001.

Table 4. The Spearman correlation analysis of severity of TMD with sEMG signal and mandibular kinetics

Variables		sEMG signal and mandibular kinetics
The severity of TMD
TA-ND	r_s= -0.4843; P < .0001
MM-ND	r_s= -0.4392; P < .0001
TA-CR	r_s= -0.4267; P < .0001
MM-CR	r_s= -0.4080; P < .0001
MVO	r_s= -0.6385; P < .0001
CO-MO	r_s= -0.3896; P < .0001
MOV	r_s= -0.3465; P = .0004
MCV	r_s= -0.6260; P < .0001

TA-ND: sEMG of temporalis anterior during maximal voluntary clenching against natural dentition; MM-ND: sEMG of masseter during maximal voluntary clenching against natural dentition; TA-CR: sEMG of temporalis anterior during maximal voluntary clenching against cotton rolls; MM-CR: sEMG of masseter during maximal voluntary clenching against cotton rolls; MVO: Maximum vertical opening; CO-MO: Straight-line distance from centric occlusion to maximum opening; MOV: Maximum opening velocity; MCV: Maximum closing velocity.

No competing interests reported.

Comparative analysis of myoelectric activity and mandibular movement in healthy and temporomandibular disorder subjects

Status:

Journal Publication

Version 1

Abstract

Figures

Introduction

Methods

Results

Discussion

Conclusion

Declarations

References

Tables

Additional Declarations

Status:

Journal Publication

Version 1