Surface electromyographic response of the neck muscles to maximal voluntary clenching of the teeth

Neuromuscular control of masticatory muscles in people with intellectual disability, middle-aged adults and older adults

BACKGROUND

Motor control issues are common for people with intellectual disabilities (PWID), resulting in difficulties with basic activities of daily living, including eating. Mastication, which is crucial for digestion and overall health, is poorly understood in this population. PWID shows frailty similar to older people, highlighting the importance of comparing masticatory motor control with older adults. This study compared the neuromuscular control of the masticatory muscles in middle-aged, PWID and older adults.

METHODS

A cross-sectional analytical design was used. During the mastication task of a carrot piece (2 cm in diameter and weighing 0.5 g), surface electromyography was used to record muscle activity patterns from the right and left masseter and temporalis muscles. Principal component analysis (PCA) was used to assess neuromuscular control. A z-score normalisation of the first component's variance from PCA to identify those individuals with altered neuromuscular control. A mixed ANOVA was performed to assess the interaction between principal components, groups and body composition.

RESULTS

Thirty PWIDs (aged 35-55 years), middle-aged adults and 32 older adults were recruited. PWID and older adults showed decreased neuromuscular control of the masticatory muscles compared to middle-aged control adults (P < 0.05). PWID had the highest proportion of individuals with altered neuromuscular control of the masticatory muscle (53%) compared to older adults (19%) and middle-aged adults (0%) (P < 0.05).

CONCLUSIONS

Our results indicate that PWID and older adults have reduced neuromuscular control compared to middle-aged adults. Notably, a significant proportion of the PWID showed altered masticatory muscle control compared to older adults. Further research is needed to explore the potential benefits of masticatory muscle training for PWID.

A, Kumari M, . A. Electromyographic Analysis of Masticatory and Accessory Muscles in Subjects With Implant-Supported Fixed Prostheses: A Three-Arm Comparative Clinical Study

Aim This study compares the electromyographic (EMG) activity of the masticatory and accessory muscles in patients with natural teeth and those wearing full-mouth fixed prostheses supported by implants. Method In this study, 30 subjects of 30-69 years performed static and dynamic EMG measurements of masticatory and accessory muscles (masseter, anterior temporalis, SCM, and anterior digastric) and were divided into three groups: Group 1 (G1, Control, Dentate), comprising 10 subjects with 14 or more natural teeth (30-51 years of age); Group 2 (G2, single arch implant-supported fixed prosthesis) composed of 10 patients with unilateral edentulism who were successfully rehabilitated with implant-supported fixed prostheses in the maxilla or mandible, restoring occlusion to 12-14 teeth per arch; (39-61 years of age); and Group 3 (G3, full mouth implant-supported fixed prosthesis) with 10 subjects with completely edentulous arches with full mouth implant-supported fixed prosthesis with 12 occluding pairs of teeth (46-69 years of age). The left and right masseter, anterior temporalis, superior sagittal, and anterior digastric muscles were examined at rest, as well as maximum voluntary clenching (MVC), swallowing, and unilateral chewing. On muscle bellies, disposable, pre-gelled silver/silver chloride bipolar surface electrodes were parallel to muscle fibers. BIO-PAKeight® channels recorded electrical muscle activity (Bio-EMG III, BioResearch Associates, Inc. Brown Deer, WI). Results Full mouth embed upheld fixed prostheses patients had higher resting EMG activity than dentate and single curve implants. Full mouth embeds supported fixed prostheses and dentate patients had significantly different temporalis and digastric muscle mean EMG activity. Dentate people used their temporalis and masseter muscles more during the MVC than those with single-curve embedded upheld fixed prostheses limiting natural teeth or full-mouth implants. No event had the crucial item. Neck muscle differences were insignificant. All groups had higher SCM and digastric EMG activity during MVC than at rest. The single curve embed upheld fixed prosthesis group's temporalis and masseter muscles were significantly more active during gulping than the dentate and entire mouth groups. Single curve and entire mouth gulping SCM muscle EMG activity were similar. Digastric muscular EMG activity differed significantly between those with full-arch or partial-arch fixed prostheses and dentures. When instructed to bite one side, the masseter and temporalis front muscle mean EMG activity increased on the unrestricted side. Unilateral biting and temporalis muscle activation were comparable between groups. For the masseter muscle, the mean EMG was also higher on the functioning side, with no truly large differences between the three groups except for right-side biting when comparing the dentate and full mouth embed upheld fixed prosthesis groups and the single curve and full mouth groups. Conclusion The temporalis muscle activity difference was statistically significant in the full mouth implant-supported fixed prosthesis group. The three groups' static (clenching) sEMG analysis showed non-significant temporalis and masseter muscle activity increases. Full mouth swallowing increased digastric muscle activity. All three groups had similar unilateral chewing muscle activity except for the working side masseter muscle.

Cervical Myofascial Pain Is Associated with an Imbalance of Masticatory Muscle Activity

This study aimed to assess the relationship between the occurrence of cervical myofascial pain with active myofascial trigger points (MTrPs) within the upper trapezius muscle and the electromyographic asymmetry index (AsI) of masticatory muscles: temporalis anterior (TA), superficial part of the masseter muscle (MM), and anterior belly of the digastric muscle (DA). The study group comprised 100 subjects (80 women and 20 men) aged 18 to 30 years (mean 23 ± 2.6 years) reporting pain in the neck muscles, diagnosed with myofascial pain with active MTrPs only within the upper trapezius muscle. The control group comprised 60 healthy, pain-free subjects (42 women and 18 men) aged 20 to 30 years (mean 22.8 ± 2.6 years) without MTrPs in the upper trapezius muscle. The palpation measurement, based on the diagnostic criteria of Travell and Simons, was used to diagnose active MTrPs. The masticatory muscle activity was recorded using an 8-channel device for surface electromyography—BioEMG III^TM. Significant differences in electromyographic patterns between the group with MTrPs in the right side of upper trapezius muscle and the control group were observed within resting activity for the AsI TA (MTrPs: 8.64 vs. controls: −3.22; p = 0.001) and AsI MM (MTrPs: 7.05 vs. controls: −2.09; p = 0.018). Controls presented different electromyographic patterns during maximum voluntary clenching with cotton rolls between teeth within masseter muscle compared to the MTrPs group (MTrPs: 9.27 vs. controls: −0.43 vs. p = 0.041). Participants with MTrPs in the left side of upper trapezius muscle presented predomination of left-sided electromyographic patterns at rest within temporalis anterior in comparison to controls (MTrPs: −19.22 vs. controls: −3.22; p = 0.001). MTrPs within the trapezius muscle may be related to asymmetry within the masticatory muscle activity, suggesting that the presence of myofascial pain within the cervical muscles plays a role in the imbalance of the stomatognathic system. A unilateral active MTrPs within the trapezius muscle may increase the sEMG activity on the same side of the temporalis anterior and masseter muscles.

Electromyography-Guided Adjustment of an Occlusal Appliance: Effect on Pain Perceptions Related with Temporomandibular Disorders. A Controlled Clinical Study

Background: The purpose of this study is to evaluate the effect of an electromyography-guided adjustment of an occlusal appliance on the management of Temporomandibular disorder-related pain. Methods: Data from 40 adult patients (20 males and 20 females), who underwent treatment with occlusal appliances, were recorded. A total of 20 appliances were adjusted according to electromyographic data (group 1), while the others were adjusted by a clinical conventional procedure (group 2). Muscle pain to palpation, pain during articular movements and headache were recorded by a VAS score (from 0 to 100) before the beginning of treatment (T0), at T1 (4 weeks) and T2 (8 weeks). Results: Results showed a reduction of pain in both groups, with a better trend for group 1, where better results were achieved at T1 and maintained stability at T2, with an improved mean value regarding all parameters studied. After 8 weeks, only small recurrences started to occur in muscle pain to palpation in group 2. Conclusions: An occlusal appliance seems to be able to achieve a clinical improvement of Temporomandibular disorder (TMD)-related pain and headache, independently from the adjustment procedure adopted. However, the use of a surface electromyographic activity of masticatory muscles (sEMG) device as an aid in the calibration procedure seems to allow a better trend because the improvement of symptoms was obtained before, after the first four weeks, with an improvement in percentages of all the variables investigated. While the conventional procedure obtained later the improvement.

Effects of sitting posture and jaw clenching on neck and trunk muscle activities during typing

Neck pain is one of the most common musculoskeletal complaints. Evidence suggests that increased activities of neck and trunk muscles are one of the mechanisms related to neck pain. Jaw clenching and sitting posture may modulate the muscle activity in neck and trunk muscles during typing. The present study aimed to assess the effects of different postural positions and clenching conditions on neck and trunk muscle activities. Thirteen healthy adults (39.8 ± 5.0 years) performed computer typing tasks in four conditions (two postural positions [upright vs slouched] and two jaw clenching conditions [clenching vs non-clenching]). Integrated surface electromyography (iEMG) was measured in sternocleidomastoid (SCM), upper trapezius (uTP) and middle trapezius (mTP) muscles and compared between conditions. The Friedman and Wilcoxon signed-rank tests with Bonferroni's corrections were used to estimate the condition-specific differences in the iEMG data. The statistical significance level was set at 5%. In both postural positions, iEMG_SCM was significantly greater under the jaw clenching than under the non-clenching condition (χ²  = 21.700, P < .01). Under both jaw clenching conditions, iEMG_uTP was significantly greater in the slouched than in the upright postural position (χ²  = 23.182, P < .01). No significant differences in iEMG_mTP were seen across conditions (χ²  = 5.018, P = .10). Sitting posture and jaw clenching appear to influence activities of different muscles.

Advanced interdisciplinary treatment protocol for pediatric obstructive sleep apnea including medical, surgical, and orthodontic care: a narrative review

OBJECTIVE

To suggest an updated interdisciplinary treatment protocol for pediatric obstructive sleep apnea (POSA) based on the integration of craniofacial growth modification into medical and surgical sleep practice.

METHODS

PubMed, Scopus, and Cochrane library were searched up to February 2020 using keywords. Among 184 articles, 80 studies were finally included. An integrated treatment protocol for POSA encompassing craniofacial skeletal management as well as medical and surgical care was attempted.

RESULTS

A differential diagnostic workflow for identifying the phenotype of POSA was suggested, and a phenotype-based treatment protocol for POSA was proposed. Despite the lack of high level of evidence, timely skeletal growth modification in three dimensions using craniofacial growth potential could be valuable treatment for upper airway development in POSA patients with craniofacial phenotypic cause.

CONCLUSION

A novel precision treatment protocol will advance clinicians to determine the primary option or to apply the combined strategy for POSA patients.

Evaluation of Masticatory Muscle Function Using Digital versus Traditional Techniques for Mockup Fabrication: A Controlled Prospective Study

Background: the aim of this longitudinal prospective study was to analyze the effect of digital and traditional mockup on masticatory muscle activity in patients with teeth wear, rehabilitated with an increase of occlusal vertical dimension. Subjects and Methods: a sample of 22 adult patients who were about to receive a prosthetic rehabilitation was divided into a study group (3M; 9F; mean age 42 ± 0.8 years), treated using the digital mockup; and a control group (2M; 8F; mean age 37 ± 0.5 years), treated using the conventional technique (traditional) mockup. Electromyographic activity of anterior temporalis and masseter muscles were evaluated before the beginning of the treatment (T0), at mockup insertion (T1), after treatment (T2) and each lapse of time lasted 2–5 months. Results: the comparison between the two groups at different time gaps revealed that at ∆1 (T1–T0) only the impact index (IMP) showed significant difference and no other significant variation was observed between the two groups at ∆2 (T2–T1) and ∆3 (T2–T0). It concludes that traditional and digital methods generally have nonsignificant differences. Conclusions: both methods seem to be effective in prosthetic rehabilitation and give comparable effects on masticatory muscles.

Temporomandibular disorders and cervicogenic dizziness: Relations between cervical range of motion and clinical parameters

OBJECTIVE

To analyze the cervical range of motion (CROM) and clinical parameters in patients affected by myogenous temporomandibular disorders (TMD), cervicogenic dizziness (CGD), both TMD and CGD (TMD/CGD), and a group of healthy subjects (HS).

METHODS

CROM degrees, Dizziness Handicap Inventory (DHI), Tampa Scale for Kinesiophobia (TSK-17), Hospital Anxiety and Depression Scale (HADS), and Jaw Functional Limitation Scale 20 (JFLS-20) scores were compared between 46 TMD patients, 49 CGD subjects, 43 TMD/CGD patients, and 98 HS.

RESULTS

TMD/CGD and CGD patients demonstrated significantly lower CROM degrees and higher DHI, TSK-17, and HADS values when compared to TMD patients. TMD/CGD and TMD patients demonstrated higher JFLS-20 values when compared to CGD and HS. Significant negative correlations were found in TMD/CGD and TMD patients between JFLS-20 and CROM in flexion and extension.

DISCUSSION

Present findings demonstrated a relation between spine movement impairment and TMD.

Dentoskeletal Class II Malocclusion: Maxillary Molar Distalization with No-Compliance Fixed Orthodontic Equipment

Dentoskeletal class II malocclusion due to a protruded upper dental arch is a major reason for an orthodontic treatment. In these cases, the correction of class II can be hindered by molar distalization, obtained with 'no-compliance therapy' that involves the use of appliances which minimize the need for such co-operation and attempt to maximize the predictability of results. The aim of this review was to outline the effectiveness of no-compliance fixed orthodontic devices in the molar distalization. After selection according to the inclusion/exclusion criteria, 16 articles from 2000 to 2019 were qualified for the final analysis. The literature shows various no-compliance fixed devices whose effect is to distalize the maxillary molars. The present revision allows to conclude that there is a need to increase the number of studies, especially with regard to the most recently introduced devices in the literature. The analysed studies allow to hypothesize that these appliances act with a minimal variability of molar distalization and disto-inclination among them, although different effects among the appliances can be observed as regards to the anchorage.

Management of a Facilitated Aesthetic Orthodontic Treatment with Clear Aligners and Minimally Invasive Corticotomy

Accelerating orthodontic tooth movement has become a topical issue and the corticotomy seems to be the only effective and safe technique reported in the literature. Simultaneously, aesthetic orthodontic treatment with removable clear aligners has become commonly requested. The aim of this paper is to illustrate the management of facilitated aesthetic orthodontic treatment, a combined approach including piezocision corticotomy and clear aligners for orthodontic treatment. Orthodontic planning for traditional clear aligners should be modified to take advantage of the corticotomy technique in order to facilitate the most difficult orthodontic movements needed to achieve treatment completion, where each aligner will be used for four days rather than 15 days for a total time of four months. A corticotomy with a modified minimally invasive flapless piezocision technique should be performed in both jaws at the same time, before the time window of the orthodontic treatment, where the most difficult orthodontic movements are planned. Treatment planning where difficult orthodontic movements, such as anterior open-bite closure and extraction space closure, are easily managed with clear aligners and are presented as examples of facilitated aesthetic orthodontic treatment application. The combination between aesthetic treatment with clear aligners and modified piezocision corticotomy, if carefully planned, seems to represent a synergy that achieves the current goals of orthodontic treatment. The primary objectives of this combination should be facilitating difficult orthodontic movements and reducing treatment duration.

Comparative Analysis of the Reproduction Accuracy of Main Methods for Finding the Mandible Position in the Centric Relation Using Digital Research Method. Comparison between Analog-to-Digital and Digital Methods: A Preliminary Report

Purpose: To compare the aspect of the reproduction accuracy in studied methods of determination of the (CR) of jaws using the digital research methods. The methods used were bilateral manipulation by P.E. Dawson, frontal deprogrammer, leaf gauge, and intraoral device for recording of Gothic arch angle. Methods: To determine the reproduction accuracy of the centric relation of jaws, we examined 5 patients with intact dentition in a prosthetic dentistry clinic (first class in Angle’s system). For each method, 20 registrations of the centric jaw relation were carried out by one operator. The breaks between definitions were 30 minutes. A total of 400 CR recording operations were carried out (400 records of CR). In order to study the reproducibility of CR determination methods, 200 recorded mandible positions were analyzed by means of an analog-to-digital method (a macro kit Canon 650D, Canon 60 mm macro IS USM f2.8, Canon macro ring MR-14 EX and the computer program Adobe Photoshop) to assess the first occlusal contact obtained in the CR of jaws, while the other 200 were analyzed by means of a digital method (the computer program Avantis for 3D modeling, Prime as a laboratory 3D scanner (DOF), and Trios as an intraoral scanner (3Shape)) to assess the spatial position of the mandible in the CR. Statistical analysis was carried out using STATISTICA-10. In all statistical analysis procedures, the critical significance level p was assumed to be 0.05. Results: In the study of the data by means of the computer program Avanti 3D, the reproducibility of the mandible position in the CR reached 0.119 ± 0.012 mm for frontal deprogrammer, 0.225 ± 0.028, p ≤ 0.05 for bilateral manipulation by Dawson P.E., 0.207 ± 0.02, p ≤ 0.05 for leaf gauge, and 0.120 ± 0,013, p ≤ 0.05 using an intraoral device for recording the Gothic arch angle. The analog-to-digital method showed an identical tendency for reproduction of the mandible position. Conclusions: The digital analysis we made using the Avantis 3D program showed, with high confidence, that the maximum reproducibility of the CR position was reached by using our own design frontal deprogrammer and the device for recording Gothic arch angle.

Occlusion time analysis in military pilots affected by bruxism

Military pilots are characterized by peculiar job conditions related to intense accelerative stresses. For this, they frequently report work-related neck and back pain and are affected by bruxism. The aim of this case-control study is to analyze the occlusion time (OT) in a sample of military pilots affected by bruxism, compared with healthy non-pilot subjects. 14 military pilots, all males (mean age 35.14 ± 2.32 y), affected by bruxism, were compared with an age matched control group of 14 male subjects (mean age 32.29 ± 4.84 y). The T-Scan computerized occlusal analysis system (Tek-Scan Inc., Boston, MA, USA) was used to record the subjects' occlusion times during 4 mandibular opening-closing movements. Military pilots affected by bruxism showed a statistically significant lower (reduced of 85%) mean OT, compared with control subjects (p < 0.0001). Military pilots are characterized by a highly reduced occlusion time compared to healthy non-pilot subjects. This feature could not be only related with the presence of bruxism but with their particular clinical job-related condition that causes different dental and stomatognathic system problems. Further studies are encouraged to enhance the scientific knowledge in this field.

Occlusion time analysis in military pilots affected by bruxism

Military pilots are characterized by peculiar job conditions related to intense accelerative stresses. For this, they frequently report work-related neck and back pain and are affected by bruxism. The aim of this case-control study is to analyze the occlusion time (OT) in a sample of military pilots affected by bruxism, compared with healthy non-pilot subjects. 14 military pilots, all males (mean age 35.14 ± 2.32 y), affected by bruxism, were compared with an age matched control group of 14 male subjects (mean age 32.29 ± 4.84 y). The T-Scan computerized occlusal analysis system (Tek-Scan Inc., Boston, MA, USA) was used to record the subjects' occlusion times during 4 mandibular opening-closing movements. Military pilots affected by bruxism showed a statistically significant lower (reduced of 85%) mean OT, compared with control subjects (p < 0.0001). Military pilots are characterized by a highly reduced occlusion time compared to healthy non-pilot subjects. This feature could not be only related with the presence of bruxism but with their particular clinical job-related condition that causes different dental and stomatognathic system problems. Further studies are encouraged to enhance the scientific knowledge in this field.

Morphological and Functional Parameters in Patients with Tooth Wear before and after Treatment

Advanced tooth wear often results in lost vertical dimension and impacts facial aesthetics. Complex restorative treatment can replace the lost tooth structure and improve functional occlusal and facial skeleton parameters.

PURPOSE

The aim of the study is to assess changes in the morphological and functional occlusal parameters of the facial skeleton after prosthetic rehabilitation that increased lost occlusal vertical dimension.

MATERIAL AND METHODOLOGY

50 patients with advanced tooth wear were clinically examined, to assess the degree of wear. Each subject underwent cephalometric analysis, digital occlusal analysis, and electromyographic analysis, of the anterior temporalis, superficial masetter, anterior digastric, and the sternocleidomastoid muscles. Prosthodontic treatment was performed to restore the occlusal vertical dimension of each subject's occlusion, which was followed by repeating the pretreatment analyses. Pre and post treatment parameters were statistically compared.

RESULTS

Pre-treatment cephalometric analysis showed that lost vertical dimension reduced anterior facial height and resulted in small angular skeletal parameters. Post treatment anterior facial height increased from the increased occlusal vertical dimension. The mean value of functional electrical activity during clenching post treatment, increased compared to pretreatment.

CONCLUSION

Increasing the vertical dimension of occlusion improved facial aesthetics by positively affecting facial skeletal angles. The restored occlusal surface morphology changed the pre treatment flat broad occlusal contacts into more point contacts. The increased vertical dimension of occlusion after treatment also increased muscle activity levels over the pretreatment levels after three months period of adaptation.

Assessment of thickness and function of masticatory and cervical muscles in adults with and without temporomandibular disorders

OBJECTIVE

The aim of this study was to evaluate the maximal bite force (MBF), electromyographic (EMG) activity and thickness of the masseter, anterior part of the temporalis and sternocleidomastoid (SCM) muscles in a group of young adults with and without temporomandibular disorders (TMDs).

DESIGN

Nineteen individuals comprised the TMD group (6 males/13 females, aged 25.4±3.8 years), classified based on the Research Diagnostic Criteria for TMD (RDC/TMD), and 19 comprised the control group (6 males/13 females, aged 24.1±3.6 years). The MBF was determined with a transducer placed between the dental arches at the first molars level (N). The muscles were evaluated bilaterally at rest and during maximal voluntary clenching (MVC) by assessing EMG activity and performing ultrasonography (USG). The mean values of these measures for both sides of the mouth were used. The normality of the distributions was assessed by the Shapiro-Wilks test. Variables between groups and genders were compared using two-way factorial ANOVA test and correlated using the Spearman coefficient (α=0.05). Unpaired t test was used to compare variables between TMD subgroups. Logistic regression analysis was used to identify the variables associated with the presence of TMD.

RESULTS

MBF, EMG and USG data were similar among clinical groups and among TMD subgroups. The thickness of masseter and SCM muscles in the relaxed and clenching states were significantly higher in males than females. On the other hand, the EMG of the temporalis muscle in the rest state was significantly higher in females than males. Additionally, the MBF was positively correlated with the USG characteristics of masseter and SCM muscles, as well as with the EMG activity of masseter and temporalis muscles in the TMD group. In this group, there was also a positive correlation between the thickness of the masseter muscle and its activity. On the other hand, the thickness of the SCM muscle was negatively correlated with its activity. A lower MBF was independently associated with the presence of TMD.

CONCLUSIONS

Subjects with TMD exhibited similar values of MBF, thickness and electrical activity of masticatory and cervical muscles when compared with controls; positive correlations observed between these variables may suggest a muscular alteration in TMD patients and a co-activation of masticatory and cervical muscles during mandibular movement. This fact may also be confirmed by the negative association between bite forces and presence of TMD.

Atividade elétrica dos músculos cervicais e amplitude de movimento da coluna cervical em indivíduos com e sem DTM

O objetivo da pesquisa foi avaliar a atividade elétrica e a dor à palpação dos músculos cervicais, a amplitude de movimento (ADM) da coluna cervical e a relação entre atividade elétrica e ADM cervical em indivíduos com e sem desordem temporomandibular (DTM). Participaram do estudo 53 voluntários, sendo 24 com DTM e 29 sem, de ambos os gêneros, com 18 a 32 anos de idade. A DTM foi diagnosticada pelo critério de diagnóstico em pesquisa para DTM (Research Diagnostic Criteria for Temporomandibular Disorders). A eletromiografia dos músculos esternocleidomastoídeo (ECOM) e trapézio superior foi realizada bilateralmente, na situação de repouso, com frequência de 2 KHz e filtro passa-faixa de 10-1000 Hz. As medidas de ADM de flexão, extensão, lateroflexão e rotação foram realizadas com um flexímetro e a comparação entre os grupos contou com o teste de Mann Whitney. O teste de Spearman foi aplicado para a correlação entre as variáveis, com nível de significância de 5%. Não foi verificada nenhuma diferença na ADM cervical entre os grupos. A atividade elétrica demonstrou-se significativamente maior nos músculos ECOM direito (p=0,0130), trapézio superior direito (p=0,0334) e esquerdo (p=0,0335) no grupo DTM em relação ao grupo controle. Não houve correlação significante entre atividade elétrica e ADM cervical. A dor nos músculos cervicais apresentou-se significativamente maior apenas no músculo ECOM direito (p=0,0055). Conclui-se que os grupos estudados registraram diferença na atividade elétrica dos músculos cervicais, sendo esta maior em indivíduos com DTM.

Masticatory muscle activity during maximum voluntary clench in different research diagnostic criteria for temporomandibular disorders (RDC/TMD) groups

The research diagnostic criteria for temporomandibular disorders (RDC/TMD) are used for the classification of patients with temporomandibular disorders (TMD). Surface electromyography of the right and left masseter and temporalis muscles was performed during maximum teeth clenching in 103 TMD patients subdivided according to the RDC/TMD into 3 non-overlapping groups: (a) 25 myogenous; (b) 61 arthrogenous; and (c) 17 psycogenous patients. Thirty-two control subjects matched for sex and age were also measured. During clenching, standardized total muscle activities (electromyographic potentials over time) significantly differed: 131.7 microV/muVs % in the normal subjects, 117.6 microV/microVs % in the myogenous patients, 105.3 microV/microVs % in the arthrogenous patients, 88.7 microV/microVs % in the psycogenous patients (p<0.001, analysis of covariance). Symmetry in the temporalis muscles was larger in normal subjects (86.3%) and in myogenous patients (84.9%) than in arthrogenous (82.7%), and psycogenous patients (80.5%) (p=0.041). No differences were found for masseter muscle symmetry and torque coefficient (p>0.05). Surface electromyography of the masticatory muscles allowed an objective discrimination among different RDC/TMD subgroups. This evaluation could assist conventional clinical assessments.

The influence of occlusion on jaw and neck muscle activity: a surface EMG study in healthy young adults

The electromyographic (EMG) characteristics of masseter, temporalis and sternocleidomastoid (SCM) muscles during maximum voluntary teeth clench were assessed in 27 male and 35 female healthy young adults. Subjects were divided into two groups: (i) 'complete' Angle Class I (bilateral, symmetric canine and molar Class I relationships), and (ii) 'partial' Angle Class I (one to three canine/molar Class I relationships, the remaining relationships were Class II or Class III). On average, standardized muscular symmetry ranged 80.7-87.9%. During maximum voluntary teeth clench, average co-contraction of SCM muscle was 13.7-23.5% of its maximum contraction. On average, all torque coefficients (potential lateral displacing component) were >90%, while all antero-posterior coefficients (relative activities of masseter and temporalis muscles) were >85%. The average integrated areas of the masseter and temporalis EMG potentials over time ranged 87.4-106.8 muV/muV s%. Standardized contractile muscular activities did not differ between 'complete' and 'partial' Angle Class I, and between sexes (two-way analysis of variance). A trend toward a larger intragroup variability in EMG indices was observed in the subjects with 'partial' Angle Class I than in those with 'complete' Angle Class I (significant difference for the temporalis muscle symmetry, P = 0.013, analysis of variance). In conclusion, the presence of a complete or partial Angle occlusal Class I did not seem to influence the standardized contractile activities of masseter, temporalis and SCM muscles during a maximum voluntary clench. Subjects with a 'complete' Angle Class I were somewhat a more homogenous group than subjects with 'partial' Angle Class I.