Research progress in effect of chewing-side preference on temporomandibular joint and its relationship with temporo-mandibular disorders / 浙江大学学报·医学版

Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.

Normalization of the electromyographic signals of masticatory muscles during non-habitual chewing activity

There is no consensus on the most appropriate method for normalizing electromyography (EMG) signals from masticatory muscles during isotonic activity. Aim: To analyze the best method for data processing of the EMG signal of the masticatory muscles during isotonic activity (non-habitual chewing), comparing raw data and different types of normalization. Methods: This is a cross-sectional study. Women aged between 18 and 45 years were selected. Anthropometric data were collected (age, height, body mass index ­ BMI, masticatory preference) as well as EMG signal (root mean square ­ RMS) data for the anterior temporal and masseter bilaterally, and for the suprahyoid muscles, during isotonic (non-habitual chewing) and isometric tasks. EMG data were processed offline using Matlab® Software. The normalization of the EMG signal was carried out using the 2nd masticatory cycle, chosen at random, of the 20 cycles collected, the maximum RMS value, and the maximum voluntary contraction (MVC). To analyze the best method of data processing for the isotonic data, the coefficient of variation (CV) was calculated. Descriptive data analysis was adopted, using the mean and standard deviation. ANOVA with repeated measures was used to detect significant differences between the methods of normalization. Statistical significance was set at 5% (α<0.05). Results: The final sample of this research was composed of 86 women. The volunteers presented an average age of 27.83±7.71 years and a mean BMI of 22.85±1.91 Kg/m2. Regarding masticatory preference, 73.25% reported the right side, and 26.75% the left side. Considering the comparison between the methods, the %CV measure of the 2nd cycle showed the lowest variation coefficient during biting for all the muscles from the raw data, RMS Max, and MVC (p=0.001, p=0.003, and p=0.001 respectively). Conclusion: In conclusion, for non-habitual chewing activity, the results of this study recommend data processing using normalization with the second cycle during chewing

Logistic regression analysis of the relationship between abnormal dental occlusion and temporomandibular disorders in lower grade college students / 口腔疾病防治

Objective @#To investigate the influence of abnormal occlusion factors on the incidence of temporomandibular disorders (TMDs) in junior college students and to provide an etiological basis for the prevention and treatment of TMDs.@*Methods @# We examined the temporomandibular joint (TMJ) and dental occlusion in 754 lower grade college students (male 354, female 400) at Zunyi Medical University (Zhuhai campus). A questionnaire was also administered. We analyzed the correlation between TMD and the other three factors (static abnormal occlusion, dynamical abnormal occlusion and oral parafunctional activity) from the perspective of multivariate unconditioned logistic regression and univariate unconditioned logistic regression with dummy variables.@*Results @#The prevalence of TMD was 31.7%. The incidence of TMD was significantly (P<0.05) associated with sleep bruxism (OR=2.070), clenching (OR=2.553), diurnal (OR=2.642) and anterior teeth overbite (OR=1.228). Univariate unconditioned logistics regression analysis by dummy variables was used to analyze the incidence of TMD at different deep overbites (mild, OR=1.558; moderate, OR=2.189; severe, OR=3.236; P<0.05). @*Conclusion@#The risk factors for TMD in lower grade college students included anterior teeth occlusion, sleep bruxism, clenching, and diurnal treatment. Worse deep overbite might increase the risk of TMD.

Study on the correlation between the mandibular masticatory muscle movement and sleep tooth wear / 华西口腔医学杂志

OBJECTIVE@#To investigate the correlation between the clinical diagnostic criteria of sleep bruxism and the frequency of mandibular movements during sleep.@*METHODS@#Video polysomnography was used to record 20 healthy adults with at least one of the following clinical symptoms and signs: 1) report of frequent tooth grinding; 2) tooth wear and dentin exposure with at least three occlusal surfaces; 3) masticatory muscle symptoms in the morning; 4) masseter muscle hypertrophy. The rhythmic masticatory muscle activity (RMMA) and isolated tonic activity were scored to compare the correlations with clinical symptoms and signs. Finally, the incidence of temporomandibular disorders (TMD) was investigated in patients with isolated tonic and RMMA subjects.@*RESULTS@#Among the 20 subjects, RMMA events were observed (5.8±3.1) times·h⁻¹ and isolated tonic episodes were observed (2.1±0.9) times·h⁻¹. The frequency of RMMA events was significantly greater in the patients with acoustic molars than in those without (P<0.05). Similarly, the frequency of RMMA events was significantly greater in the patients with tooth attrition than in those without (P<0.05). However, no difference was observed between the occurrence of RMMA and the symptoms of masticatory muscles or masseter hypertrophy in the morning. The incidence of TMD was significantly higher in the patients with RMMA than in the isolated tonic patients.@*CONCLUSIONS@#The clinical symptoms and signs often used to diagnose sleep bruxism are different clinical and physiological mandibular movements during sleep. RMMA during sleep can reflect the occurrence of tooth attrition and the high risk of TMD.

Miastenia gravis adquirida generalizada en caninos y su presentación con miositis de músculos masticatorios / Generalized Acquired Myasthenia Gravis in Canine and the Presentation with Masticatory Muscle Myositis / Miastenia gravis adquirida generalizada em caninos e apresentação com miosite de músculos mastigatórios

Resumen Cinco caninos de 4 a 9 años de edad fueron diagnosticados con miastenia gravis adquirida en asociación con miositis de músculos masticatorios, en el Hospital Escuela de la Facultad de Ciencias Veterinarias de Buenos Aires, durante el periodo 2013-2016. El diagnóstico se confirmó mediante la realización de pruebas serológicas específicas, electromiografías y biopsias musculares de los músculos masticatorios. Se realizó el tratamiento con bromuro de piridostigmina y prednisolona, por el origen inmunomediado de ambas enfermedades.

Abstract Five canines from 4 to 9 years of age were diagnosed with acquired myasthenia gravis in association with masticatory muscle myositis, in the Hospital School of the Faculty of Veterinary Sciences of Buenos Aires, during the 2013-2016 period. The diagnosis was confirmed by performing specific serological tests, electromyography, and muscle biopsies of the masticatory muscles. The treatment used pyridostigmine bromide and prednisolone, due to the immune-mediated origin of both diseases.

Resumo Cinco caninos de 4 a 9 anos foram diagnosticados com miastenia gravis adquirida em associação com miosite de músculos mastigatórios, no Hospital Escola da Faculdade de Ciências Veterinárias de Buenos Aires, durante o período 2013-2016. O diagnóstico foi confirmado pela realização de testes serológicos específicos, eletromiografias e biópsias musculares dos músculos mastigatórios. Realizou-se o tratamento com brometo de piridostigmina e prednisolona, devido à origem imunomediada de ambas as doenças.

Masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening

Patients with masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) experience limited mouth opening due to restricted muscle extension. Hyperplastic aponeurosis and tendons lead to the restriction of muscle extension. The criteria for the diagnosis of MMTAH are limited mouth opening that progresses very slowly from adolescence, intraoral palpation reveals a hard cord-like structure along the overhang of the anterior border of the masseter muscle on maximum mouth opening, and a square mandible. Conservative treatment, including pharmacotherapy, occlusal splint and physical therapy are ineffective. The standard therapy is surgical treatment, such as anterior partial aponeurectomy of the masseter muscle and coronoidectomy. The long-term results are very satisfying.

Effects of Western Massage Combined with Muscle Energy Technique on Masticatory Muscle Disorders / 中国康复理论与实践

Objective To observe the effect of the Western massage combined with muscle energy technique on masticatory muscle dis-orders. Methods 58 patients with masticatory muscle disorders were randomly divided into control group (n=29) and observation group (n=29). The control group accepted ultrashort wave therapy, while the observation group accepted the Western massage and muscle energy tech-nique. They were assessed with Visual Analogue Scale (VAS) of pain and Friction index of the temporomandibular joint (TMJ) before and 4 weeks after treatment. Results The scores of VAS and Friction index of the TMJ decreased in both groups (P<0.001), and decreased more in the observation group than in the control group (P<0.001). Conclusion The combination of Western massage and muscle energy technique is advanced for masticatory muscle disorders.

Clinical features of the sleep bruxism and gastroesophageal reflux association deserve professional attention / Características clínicas da associação entre o bruxismo do sono e o refluxo gastroesofágico merecem atenção profissional

Introdução: Bruxismo tem sido definido como uma atividade parafuncional oral que consiste em apertar e/ou ranger os dentes durante o sono ou na vigília. Além do bruxismo do sono (BS), outros movimentos orofaciais também podem, esporadicamente, ocorrer durante o sono. A regurgitação ocasional e a queimação no peito devido ao refluxo gastroesofágico (RGE) são freqüentes sintomas relatados pela população em geral. A RGE refere-se à presença de sinais e sintomas secundários, com ou sem sinais de lesões na mucosa do esôfago. Os dentistas são, muitas vezes, os profissionais da saúde que primeiro diagnosticam o RGE por meio da observação de suas manifestações orais. Objetivo: Assim, o objetivo do presente artigo foi discutir os procedimentos clínicos e diagnósticos em dois pacientes com BS e RGE, contribuindo assim para a difusão do conhecimento sobre a interação dessas duas entidades. Recomenda-se aos dentistas estarem atentos para identificar os primeiros sinais de RGE que se manifestam na cavidade oral. Conclusão: Neste ponto, destaca-se a importância de tratar o paciente como um todo, esforçando-se para identificar outras fontes de problema que poderiam atuar como fatores agravantes destas condições.

Introduction: Bruxism has been defined as an oral parafunctional activity that includes clenching and/or grinding the teeth while asleep or awake. In addition to sleep bruxism (SB), various other orofacial movements sporadically occur during sleep. Occasional regurgitation and heartburn due to gastroesophageal reflux (GER) are frequent in the general population. GER refers to the presence of symptoms that are secondary to the reflux of gastric content through the esophagus with or without signs of esophageal mucosal lesions. Dentists are often the first health care professionals to diagnose GER through observation of its oral manifestation. Objective: The aim of the present case reports was to discuss the diagnosis and clinical procedures followed in two patients with SB and GER, thereby contributing to the dissemination of knowledge about these two entities. We therefore recommend dentists to be alert to identifying the first signs of GER that appear in the oral cavity. Conclusion: At this point, we highlight the importance of treating the patient as a whole, in an endeavor to identify other sources of the problems that could contribute as factors aggravating these conditions.

Application of Botulinum toxin Type A: An arsenal in dentistry.

An extremely effective way of preventing damage to and enhancing treatment of dental hard tissues and restorations would be to ''de-programme'' the muscles responsible for excessive destructive forces and other gnathological-related diseases. The new paradigm is the intramuscular injection of Botulinum toxin type A (BOTOX) into the affected muscles. It is a natural protein produced by anaerobic bacterium, Clostridium botulinum. The toxin inhibits the release of acetylcholine (ACH), a neurotransmitter responsible for the activation of muscle contraction and glandular secretion, and its administration results in reduction of tone in the injected muscle. There are seven distinct serotypes of Botulinum toxin, viz., A, B, C, D, E, F, and G, which differ in their potency, duration of action, and cellular target sites. This paper describes the different applications of BOTOX in dentistry.

Using overdenture on implants and complete dentures: effects on postural maintenance of masticatory musculature

Aims: Thanks to advances in osseointegration, oral rehabilitation specialists have had the option of using implants to improve retention and stability in treatments with complete dentures. This study compared the masticatory muscle electromyographic activity in implant-supported overdenture wearers, complete denture wearers and dentate individuals. The electromyographic activity of the right and left masseter muscles, and the right and left anterior temporalis muscles was analyzed in 10 implant-supported overdenture wearers (Group 1), 10 conventional complete denture wearers (Group 2), and 10 dentate individuals (Group 3), with mean age of 65 years, at rest and during postural position maintenance. The analysis was performed using the MyoSystem-Br1 electromyographer with differential active electrodes. Analysis of variance tests were carried out to compare the groups and muscles and revealed different electromyographic values that were statistically significant at 1% significance level. Duncan’s pos-hoc test showed that Group 3 presented the smallest values (pd”0.01). The electromyographic contraction pattern was similar between Groups 1 and 3 (p>0.01), and hyperactivity of anterior temporalis muscles was observed in Group 2 (pd”0.01). Conclusions: dentate individuals had smaller electromyographic values of masticatory muscles and the overdenture use caused electromyographic contraction patterns similar to those of dentate individuals in both positions.

Treatment with Chinese botulinum toxin type A in 16 cases of masticatory spasm / 中华神经科杂志

Objective To study the therapeutic efficacy of Chinese botulinum toxin type A (CBTX- A) in masticatory spasm patients.Methods 16 patients with masticatory spasm were treated with CBTX-A local injection.12 patients showed jaw clench with masseter and temporalis affected (type Ⅰ).Four showed jaw clench and deviation to one side with pterygoid muscle affected unilaterally or bilaterally (type Ⅱ).All patients showed paroxysmal clenched jaw with difficulty in opening their mouths.There were no other clinical manifestations.CT and MRI did not reveal any intracerebral abnormalities.The efficacy and adverse effects were observed.Results CBTX-A were injected into 16 patients,resulting in a significant improvement of symptoms in 13 cases (4 cases of unilateral type Ⅰ,7 of 8 cases bilateral type Ⅰ,2 of 4 type Ⅱ).The spasms ceased within 3-10 days after the injection,and the effects lasted for 8-26 weeks.Four patients were observed to have slight masseter weakness after the injections,which recovered within a few weeks.The benefit persisted after identical repeated injection.Conclusion CBTX-A injection is an effective and safe treatment for masticatory spasm.

A Study on the Relation between Delaire's Ideal Occlusal Plane and Masticatory Muscle Activity in Korean Normal Angle Class I Occlusion Individuals

According to the functional matrix theory, Delaire proposes that individual occlusal plane was determined by variable effects of teeth, maxilla, mandible, cranium, cranial base and soft tissue matrix including the orofacial musculature. and that there is the ideal occlusal plane determined by the most proper spatial position of maxilla and mandible, functionally and esthetically. This study was designed to find out the relation between Delaire's ideal occlusal plane and muscle activity of masticatory muscles in individuals who have normal maxillo-mandibular relationships. Lateral cephalometric radiographs were taken and his/her individual occlusal plane and ideal occlusal plane were analyzed with Delaire's architectural and structural craniofacial analytic method. For evaluation of muscle activities of masticatory muscles, electromyography of anterior temporal muscle, superficial masseter muscle, and anterior belly of digastric muscle was recorded in fifty Korean normal Angle class I occlusion individuals. According to the average value of ideal occlusal plane, fifty normal Angle class I occlusion individuals were classified into three groups: Ideal occlusal plane group(I group), hyperrotation group(I+ group) and hyporotation group(I-group). The result of this study was as follows: 1. The results of Delaire's architectural and structural craniofacial analysis of lateral cephalography of the fifty Korean normal Angle class I occlusion individuals are that twelve persons(24%) have consistent or parallel with ideal occlusal plane and the average of angular difference was 1.22 degrees +/-3.69 degrees. 2. There is no significant difference in muscle activities of masticatory muscles during resting(p0.05) 4. Although there is no significant differences of masticatory muscle activities among the three groups, the fact that increasing tendency of masseter muscle activity of ideal occlusal plane group(I+) than those of any other groups(I+ and I-) during bilateral clenching was noted. There is only the implication that occlusal plane makes some effects on masticatory muscle activities, espacially that of masseter muscle during bilateral clenching. In conclusion, the hypothesis that occlusal plane is one of the factors which affect the muscle activities of masticatory muscles and that anyone whose occlusal plane consistent with Delaire's ideal occlusal plane has an extraordinary functional advantage in masticatory muscle function cannot be proven with electromyography methods.

Analysis of masticatory muscles electromyography of the patients with unilateral posterior crossbite / 实用口腔医学杂志

Objective:To study the effects of unilateral posterior crossbite on masticatory muscle functions pattern by using electromyography(EMG).Methods:20 subjects(11 males and 9 females)with unilateral posterior crossbite were selected.Subjects were instructed to stay mandibular postural position and to make maximum bite in intercuspal position(ICP)and bilateral chewing.EMG data of the left and right masseter and anterior temporalis muscles were recorded.Asymmetry index of masseter muscles(ASMM) and asymmetry index of temporalis muscles(ASTA)were calculated and compared.20 subjects with individual normal occlusion were used as control.Results:Compared to control group,masseter and temporal muscle activities in unilateral posterior crossbite group were lower in maximum bite and bilateral chewing;The activities of two muscles at crossbite side were lower than that at noncrossbite side.Under maximum bite and bilateral chewing,ASMM and ASTA in unilateral posterior crossbite group were significantly higher than those in control group;ASMM and ASTA in Subjects with one posterior tooth crossbite is lower than subjects with several teeth crossbite.Conclusion:It can be suggested that unilateral posterior crossbite may damage the function of mastication muscle.

Effect of occlusal splint oa electromyogram of lateral pterygoid muscie dysfunction / 实用口腔医学杂志

The electromyogram(EMG) of lateral pterygoid muscle (LP) in 43 patients with LP dysfunction was measured before, when and after the use of occlusal splint. The postural and clenching activity of superior LP decreased dramatically when patients were wearing the occlusal splint. Normal EMG was observed in patients with normal arthrograra when the symptoms and signs were eliminated or reduced by occlusal splint. The EMG of dysfunctional LP in some patients with anteriorly displaced disk recovered to that with normal function as the incoordinated condyle -disk rektion was corrected. However, LP dysfunction was still present in most patients with irreversible anterior disk displacement and disk perforation after splint therapy.

THREE-DIMENSIONAL MASTICATORY MUSCLE FORCE VECTORS DETERMINED BY CT AND MRI FUSION IMAGE TECHNOLOGY / 解放军医学杂志

In order to measure and analyze three dimensional masticatory muscle force vectors in craniofacial region, the multiresolution method based on wavelet pyramid was used for the fusion of cranio jaw facial CT and MRI image, then these images were visualized. The results showed that the area of physiological cross section (PCS) and the maximum muscle force were different during functioning in the masticatory muscles system. The various masticatory muscle forces or various sides in the same muscle were also different in the three dimensional directions. The results suggested that determination of three dimensional masticatory muscle vectors is feasible by CT and MRI fusion image technology in craniofacial region, and can provide significant results for the basic research in the masticatory muscle system.

Expression of matrix metalloproteinases mRNA in growing rats masticatory muscle after functional mandibular protrusion / 西安交通大学学报(医学版)

Objective To investigate molecular changes in growing rats masticatory muscle after functional mandibular protrusion.Methods SD rats were randomly divided into eight groups as control 3d,7d,14d,21d and experimental 3d,7d,14d,21d.The RTPCR and qPCR methods were used to find expression and any differences of mRNA of MMPs in growing rats masticatory muscle after functional mandibular protrusion. (Results)(① Expression) of MMP-2,MMP-9 mRNA expressed in all growing rats masticatory muscle.② Expression differences of MMP-2 and MMP-9 mRNA in 3d,21d were found between control and experimental groups after functional mandibular protrusion.Conclusion ①MMP-2 and MMP-9 mRNA participate in masticatory muscle normal development.(② MMPs) mRNA involve changes in growing rats masticatory muscle after functional mandibular protrusion.