Masticatory Muscle Thickness Research Articles

Evaluation of the thickness of masticatory muscles in patients with chronic periodontitis by ultrasonography.

Periodontitis is one of the most common chronic inflammatory diseases. It causes changes in the biting abilities of individuals. However, periodontal treatment has positive effects on masticatory function. The aim of this study is to determine the effect of periodontitis and periodontal treatment on masticatory abilities by measuring masseter and temporal muscle thicknesses with ultrasonography before and after periodontal treatment in chronic periodontitis patients. The patients included in the study were determined by clinical and radiological examination. The thickness of the masseter and temporal muscles of the patients were measured by ultrasonography. Periodontal measurements and treatments of the patients were completed by a single physician. IBM SPSS 20.0 (IBM Corp., Armonk, NY) statistical program was used for statistical analysis. A statistically significant difference was found between the values of periodontal measurements before and after treatment (p<0.05). In the ultrasonography measurements of the thickness of masseter and anterior temporal muscles, a statistically significant increase was observed in both rest and contraction values at all time intervals (p<0.05). Muscle thicknesses of male patients were higher than female patients. Periodontitis negatively affects the masticatory performance of individuals. Chronic periodontitis patients should be referred for periodontal treatment without wasting time.

Comparison of ultrasonography-based masticatory muscle thickness between temporomandibular disorders bruxers and temporomandibular disorders non-bruxers

To compare masticatory muscle thickness in patients with temporomandibular disorders (TMDs) during rest and clenching, and by body position, using ultrasonography. This prospective study included 96 patients with TMD (67 females, 29 males; mean age: 40.41 ± 17.88 years): group 1, comprising 66 patients with TMD without bruxism (TMD_nonbruxer), and group 2, comprising 30 patients with concurrent TMD and bruxism (TMD_bruxer). In patients with TMD, bruxism was correlated with the presence of tinnitus, muscle stiffness, sleep problems, psychological stress, and restricted mouth opening. The masseter muscle significantly thickened during clenching (11.16 ± 3.03 mm vs 14.04 ± 3.47 mm, p < 0.001), whereas the temporalis muscle showed no significant increase in thickness from resting to clenching in an upright position (7.91 ± 1.98 vs 8.39 ± 2.08, p = 0.103). Similarly, during clenching in the supine position, the masseter muscle was significantly thicker compared with rest (11.24 ± 2.42 vs 13.49 ± 3.09, p < 0.001), but no significant difference was observed in temporal muscle thickness (8.21 ± 2.16 vs 8.43 ± 1.94, p = 0.464). In comparison between two groups, the average thickness of the masseter muscle was greater among TMD_bruxers than among TMD_nonbruxers in both the upright and supine positions (all p < 0.05). In the generalized lineal model, female sex (B = − 1.018, 95% confidence interval [CI] − 1.855 to − 0.181, p = 0.017) and bruxism (B = 0.868, 95% CI 0.567 to 1.169, p = 0.048) significantly predicted changes in masseter muscle thickness. Female sex (B = − 0.201, 95% CI − 0.299 to − 0.103, p = 0.011), increased age (B = − 0.003, 95% CI − 0.005 to 0.000, p = 0.038), and muscle stiffness (B = − 1.373, 95% CI − 2.369 to − 0.376, p = 0.007) were linked to decreased temporal muscle thickness. Comparing TMD nonbruxer and bruxer muscle thicknesses in upright and supine positions revealed significant increased thickness in the masseter muscle during clenching but not in the temporalis muscle. Masseter muscle thickness varied significantly by sex, body position, and resting/clenching, notably influenced by bruxism. These findings emphasize the relevance of these factors in clinical examinations of patients with TMD.

Investigation of masticatory muscle thickness and mechanosensitivity of cervical and masticatory muscles in myofascial temporomandibular disorder patients with bruxism: A cross-sectional study

ObjectiveBruxism is a common problem associated with temporomandibular disorders (TMD). The aim of this study was to compare a patient group with Myofascial TMD and bruxism and a healthy control group in terms of masseter and temporal muscle thickness (clenching and resting), mechanosensitivity of neck and jaw muscles, craniofacial pain, and disability and emotional stress status. MethodsThe study included 31 patients with myofascial TMD and bruxism (19 females, 12 males) with a mean age of 29.96 ± 8.12 years (range, 18–45 years), and a control group of 31 healthy subjects (19 females, 12 males) with a mean age of 27.58 ± 9.39 years years (range, 18–45 years). Masseter and temporal muscle thicknesses were evaluated with a mobile ultrasound device both at rest and when clenching the jaw. The mechanosensitivity values between the upper trapezius, obliquus capitis inferior, masseter and temporal muscles were measured with a digital algometer device. Craniofacial pain and disability level were evaluated with the Craniofacial Pain and Disability Index (CFPDI), and emotional stress levels with the Perceived Stress Scale-14 (PSS-14). ResultsNo difference was determined between the two groups in respect of the clenching and resting ratios of muscle thickness in any muscle (p > 0.05). The mechanosensitivity values in all muscles were lower in the myofascial TMD group than in the healthy group (p < 0.05). The CFPDI and PSS-14 scores were higher in the myofascial TMD group (p < 0.05). There was a moderate positive correlation between CFPDI, PSS-14 and Bruxism Frequency Score (p < 0.05). ConclusionThe difference in mechanosensitivity and CFPDI values between the myofascial TMD patients with bruxism and the healthy control group indicates that the problem in this patient group has effects in the craniocervical and cervical regions. In addition, the correlation between CFPDI, PSS-14 and Bruxism Frequency Score in myofascial TMD patients suggests that this problem may be affected by the interaction of different parameters.

Correlation between refractive error, muscle thickness, and bioelectrical activity of selected masticatory muscles

ABSTRACT Objective The aim of this study was to analyze the correlation between the refractive error, muscle thickness, and the bioelectrical activity of selected masticatory and neck muscles in subjects with myopia. Methods For bioelectrical activity analysis within the masticatory muscles, an 8-channel BioEMG III electromyograph was used. An M-Turbo ultrasound machine was used to analyze the masticatory and neck muscle thickness. Results Statistical analysis showed significant positive correlations between masseter muscle thickness at rest on the right side. Statistical analysis showed negative correlations between the digastric muscle and Activity Index within masticatory muscles at rest on the left side when the eyes were closed. Conclusions As refractive error increases in myopic subjects, the resting tension on the temporal muscles increases, an increase in masseter muscle thickness is noted, and a decrease in bioelectrical activity on the digastric muscle at rest.

Masticatory Muscle Thickness and Activity Correlates to Eyeball Length, Intraocular Pressure, Retinal and Choroidal Thickness in Healthy Women versus Women with Myopia.

This study aims to examine the correlations between masticatory and neck muscle thickness and activity versus eyeball length, retinal thickness, choroidal thickness, and intraocular pressure in healthy women versus women with myopia. The study group consisted of 21 women aged 24 years and a control group of 19 women (mean age 23 years). For bioelectrical activity analysis within the temporalis anterior, the superficial part of the masseter muscle, the middle part of the sternocleidomastoid muscle, and the anterior belly of the digastric muscle, an eight-channel BioEMG III electromyograph were used. An M-Turbo ultrasound machine was used to analyze masticatory and neck muscle thickness. The eyeball length was examined by IOL Master 500; choroidal and retinal thickness by Optovue Angiovue; and intraocular pressure by Tono-Pen XL. Refractive errors are related to differences in muscle thickness and electromyographic activity. Bioelectrical activity within the temporalis anterior seems to be associated with ocular length, retinal thickness, and choroidal thickness in women with myopia.

Функціональна матриця в розвитку лицевого скелета в дітей

The aim of the study. Identifying the relationship between the presence of a bad habit and the violation of the formation of the facial skeleton in children. Improving the effectiveness of comprehensive treatment of patients with pathological occlusion and existing bad habits through orthodontic treatment and elimination of bad habits. Research methods. Examined and treated 15 patients aged 9–12 years (group I) and 15 patients aged 12–15 years (group II) with dental and maxillary anomalies and disorders of the architecture of the mouth against the background of bad habits. All patients underwent rehabilitation of the oral cavity, orthodontic treatment with removable and non-removable structures, surgical correction of violations of the architecture of the oropharynx (freneloplasty, plastic connective tissue plastics). Conducted a clinical study, where the main point was the detection of abnormally attached bridles of the lips and tongue, the presence of connective tissue strands in the lateral group of teeth, changes in the dental-maxillary system due to bad habits. Computed tomography – to detect changes in the position of teeth and their rudiments, density and thickness of the bony structure of the jaw bones. We performed the following 3D-modeling of the facial skull and studied the cephalometric parameters of McNamara, the thickness of symmetrical masticatory muscles, analyzed the relationship between muscle thickness and bone thickness. We compared the changes in the photoprotocol before treatment, after treatment. Scientific novelty. Clinical studies have shown that 96.6 % of the examined patients (29 people) have bad habits. Patients who were able to overcome the bad habit were more likely to receive the desired therapeutic effect from the treatment based on the results of clinical and radiological examination, cephalometric analysis and photoprotocol. All patients before treatment had violations of the architecture of the oropharynx, manifested by highly attached strands in the area of the canines, premolars and bridle of the lip on the lower jaw (less than 5 mm); low-attached strands in the area of the canines, premolars and bridle of the lip on the upper jaw (less than 5 mm). Computed tomography data showed changes in the density and thickness of the bony structure of the jaw bones in areas where they were able to eliminate the bad habit. An increase in the thickness of the bony structure of the facial skull and an increase in the thickness of the masticatory muscles on the side where they managed to eliminate the bad habit were observed. Patients in groups I and II had a significant difference in cephalometric parameters according to McNamara before treatment and one year after the start of active treatment (p ≤ 0.05). The indicators in groups I and II did not differ significantly before treatment (p ≥ 0.05), but differed significantly one year after treatment (p ≤ 0.05), which is associated with the properties of bone structure at different ages of patients. Conclusions. Bad habits progress regardless of the patient's age, manifested in 96.6 % of patients.The results of clinical and radiological studies, analysis of cephalometric parameters and data on the thickness of the masticatory muscles confirm the relationship between chronic bad habits and the development of musculoskeletal system. The results indicate the ability of bone tissue to change its thickness, shape after the elimination of bad habits and confirm the presence of a functional matrix of bone structure. Bad habit is often one of the etiological factors in the development of pathological occlusion and only with its conscious elimination the patient achieves the desired therapeutic effect. Key words: bad habits, bone structure, orthodontic treatment.

Intervertebral Disc Degeneration: Functional Analysis of Bite Force and Masseter and Temporal Muscles Thickness.

Intervertebral disc degeneration is a pathological condition associated with the intervertebral disc and is related to functional alterations in the human body. This study aimed to evaluate the maximum molar bite force and masseter and temporal muscles thickness in individuals with intervertebral disc degeneration. Thirty-two individuals were divided into two groups: those with degeneration of intervertebral discs (n=16) and those without degeneration (n=16). The maximum molar bite force (on the right and left sides) was measured using a dynamometer. Masseter and temporal muscle thickness during mandibular task rest and dental clenching in maximum voluntary contraction were analysed using ultrasound. Significant differences in the left molar bite force (p=0.04) were observed between the groups (Student's t-test, p&lt;0.05). The intervertebral disc degeneration group had a lower maximum molar bite force. No significant differences in muscle thickness were observed between the masseter and temporal muscles in either group. However, based on clinical observations, the group with intervertebral disc degeneration presented less masseter muscle thickness and greater temporal muscle thickness in both mandibular tasks. Degenerative disease of the intervertebral discs promoted morphofunctional changes in the stomatognathic system, especially in maximum molar bite force and masticatory muscle thickness. This study provides insight into the interaction between spinal pathology and the stomatognathic system, which is important for healthcare professionals who treat patients with functional degeneration.

Ultrasound Imaging of Head/Neck Muscles and Their Fasciae: An Observational Study.

Background: Masticatory muscle thickness provides objective measurements of the temporomandibular motor function, which may change in patients with oral myofascial pain. Moreover, they are considered as being part of the craniocervical unit by a crucial relationship with cervical muscles and their fasciae. In this study, we aimed to assess by ultrasound (US) imaging the fasciae of the masseter, temporal, and sternocleidomastoid muscles to understand their mean thickness and eventual variation in relationship with the muscles, sides, and sex.Methods: We studied 16 healthy volunteers without temporomandibular joint dysfunction. Concerning each subject were evaluated the range of motion of the temporomandibular joint and of the neck, the thickness of muscles and their fasciae of both sides, and the delta of muscle thickness.Results: All the motor evaluations of the subjects showed normal ranges. The US results showed that the fasciae have a mean thickness of 0.50 ± 0.1 mm, which did not change during muscle contraction. The evaluated muscles presented a symmetry between right and left (p > 0.05), even if the delta of muscle (US) thickness had a huge range between different subjects, for example in the masseter muscle from 0.7 to 4.2 mm.Conclusions: Ultrasound imaging is a suitable and reliable tool to study the muscles and fasciae of the head and neck region, permitting also the evaluation of the ability of the muscles to contract. Finally, identifying functional asymmetry that could become symptomatic, US imaging could allow an early rehabilitation treatment.

Crossfit® An Approach to Bite Force and Masticatory Muscle Thickness

Crossfit® An Approach to Bite Force and Masticatory Muscle Thickness

Evaluation of Stomatognathic System Parameters After Bariatric Surgery.

The present study aimed to evaluate electromyographic activity, bite strength, and masticatory muscle thickness in women without obesity and with severe obesity elected for bariatric surgery. Also, patients with obesity underwent bariatric surgery and were re-evaluated 3 and 6months after surgery to analyze the influence of bariatric surgery outcomes on the stomatognathic system, a functional anatomical system comprising teeth, jaw, and associated soft tissues. Thirty-seven women were enrolled in the study. Twenty-one women with class II and III obesity according to the body mass index (BMI) and eligible for bariatric surgery composed the obesity pre-surgery group (Ob). Sixteen women with a normal weight according to BMI composed the non-obesity group (NOb). Afterward, the patients from the Ob group were followed up for 3 and 6months after undergoing Roux-en-Y gastric bypass. Anthropometry, body composition, and parameters of the stomatognathic system were evaluated. The stomatognathic system of the Ob group had less muscle activity and bite strength, but the thickness of masseter and temporal muscles was larger than the NOb group. We also observed a significant change in the muscular activity and bit strength of the stomatognathic system post-bariatric surgery. Evaluating the stomatognathic system indicated that women with clinically severe obesity have less masticatory efficiency than non-obese. Also, we found a positive influence of bariatric surgery in masticatory activity after 3 and 6months. Thus, monitoring the parameters of the stomatognathic system could be important in the indication and outcomes of bariatric surgery.

Bite Force, Thickness, and Thermographic Patterns of Masticatory Muscles Post-Hemorrhagic Stroke

ObjectiveStroke is a neurological deficit of cerebrovascular origin, considered a 21st-century epidemic that causes functional changes in the human body. This study aimed to evaluate the stomatognathic system of patients after hemorrhagic stroke through the bite force, thickness, and skin temperature in the region of the masseter and temporalis muscles. Material and MethodsTwenty-four subjects were divided into groups: post-hemorrhagic stroke; with right side of the affected body (n = 12) and without the neurological disorder (n = 12). Maximum molar bite force was verified using a digital dynamometer. Muscle thickness was measured using ultrasound images obtained at rest and during maximal voluntary contraction of the masseter and temporalis muscles. Thermographic camera was used to record the thermographic patterns of the masseter and temporalis muscles. Data were subjected to Student's t-test (P < .05). ResultsThe maximum molar bite force showed significant differences in the right (P = .04) and left (P = .03) sides, with a reduction in force in the post-hemorrhagic stroke group on the affected and unaffected sides. There was a significant difference (P < .05) in the thickness of the left temporal muscle at mandibular rest (P = .01) between groups. The post-hemorrhagic stroke group clinically presented greater muscle thickness in almost 100% of the muscles evaluated in both clinical conditions. There were no significant differences in skin temperature in the masseter and temporal muscles between the groups. ConclusionsOur results suggest functional changes in the stomatognathic system of subjects after a hemorrhagic stroke, especially concerning molar bite force and masticatory muscle thickness in the temporal muscle (unaffected side).

Does Systemic Arterial Hypertension Change the Function of the Stomatognathic System?

The aim of this study was to evaluate the stomatognathic system of individuals with controlled systemic hypertension through comparison with a disease-free control group. Seventy individuals (44 female and 26 male) were divided into two groups: a controlled systemic hypertension (n=35) and a disease-free control (n=35). The individuals were evaluated on the basis of masticatory cycle efficiency of the value of the ensemble-averaged integrated linear envelope to the electromyographic signal of the masseter and temporalis muscles in the habitual (peanuts and raisins) and non-habitual chewing (Parafilm M); molar bite force (right and left) and ultrasound images from the bilateral masseter and temporal muscles at rest and maximum voluntary contraction. The data obtained were tabulated and submitted to statistical analysis (p&lt;0.05). There was a significant difference between groups in the habitual (peanuts and raisins) and non-habitual (Parafilm M) chewing with reduced muscle activity to controlled systemic hypertension group. Muscle thickness occurred significant difference between groups at rest and maximum voluntary contraction of the temporalis muscles. There was no significant difference between groups in maximum molar bite force. The present study findings indicate that the controlled systemic hypertension promotes functional changes of the masticatory system, especially with respect to its masticatory efficiency and muscle thickness.

Ultrasonographic observation of anterior temporalis and masseter muscle in open bite patients: A comparative study

Aim: The present study was done to compare the muscle thickness of the masseter and anterior temporalis muscle in adults with normal occlusion and anterior open bite using ultrasonography, in rest position and maximum intercuspation. Material and Methods: Ultrasonographic recording of masseter and anterior temporalis thickness of both sides of nine subjects with anterior open bite and normal occlusion was done. Unpaired t test was used for the intergroup comparison of muscle thickness. Results: A significant correlation between the thicknesses of both the muscles in contracted state was found to be more in anterior open bite. There was no statistically significant correlation between thicknesses of both muscles in relaxed state. Conclusion: Since no detailed investigation was done, it will be premature to give a final verdict on the correlation between the masticatory muscle thickness and facial morphology. A long term follow up will provide a new insight for future clinical purpose. Keywords: Ultrasonography, Temporalis muscle, Masseter, Open bite.

Correlation between mandibular morphology and masticatory muscle thickness in normal occlusion and mandibular prognathism.

ObjectivesThe aim of this study was to evaluate the relationship between masticatory muscle thickness and mandibular morphology in young Korean adults with normal occlusion and mandibular prognathism.Patients and MethodsMultidetector computed tomography (MDCT) was used to measure the masticatory muscle thickness on the right side in 100 Korean young adults (50 normal occlusion group, 50 mandibular prognathism group). Cephalometric analysis was done to measure mandibular morphology. Pearson correlation analysis was done to investigate the relationship between the masticatory muscle thickness and mandibular morphometry.ResultsThe four masticatory muscles showed positive correlation with intergonial width in all subjects. All muscles, except temporalis, positively correlated with height of the ramus and mandibular length. Positive correlation was also observed in all muscles, except medial pterygoid, with thickness of the ramus. In the normal occlusion group, all four masticatory muscles showed positive correlation with intergonial width and ramus thickness. Positive correlation was also observed in all muscles (except lateral pterygoid) with mandibular length. Masseter and lateral pterygoid positively correlated with height of the ramus. In the mandibular prognathism group, all masticatory muscles, except lateral pterygoid, showed positive correlation with intergonial width. The masseter muscle showed negative correlation with ANB.ConclusionThe results suggest a positive correlation of the thickness of masticatory muscles with both horizontal and vertical dimensions of the mandible. However, thickness of the masseter was found to decrease in patients with increasing severity of mandibular prognathism.

Ultrasonographic and electromyographic evaluation of three types of occlusal splints on masticatory muscle activity, thickness, and length in patients with bruxism

ABSTRACT Objective To evaluate occlusal splint type differences in patients with bruxism. Methods Seventeen controls and 51 patients were divided into three subgroups, each assigned to use a different occlusal splint (hard, soft, or semi-soft) for 3 months and assessed by ultrasonography and electromyography (EMG) before (BT) and 3 months after treatment (AT). Results EMG values in all of the occlusal splint groups were significantly lower AT than BT (p < 0.05). BT and AT EMG values in the control group did not differ. Mean muscle thicknesses in bruxism patients was greater than in controls, and the greatest muscle thickness changes occurred with the hard occlusal splint (p < 0.05). Discussion A decrease in EMG activity occurred with all three splint types and was most prominent in the hard occlusal splint group. Ultrasonographic measurements of muscle length and thickness should be used alongside EMG to measure muscle activity in bruxism patients.

Ultrasound measurements of superficial and deep masticatory muscles in various postures: reliability and influencers

Masticatory muscle thickness provides objective measurements of the oral motor function, which may change in patients with oral myofascial pain. In this study, we aimed to establish a reliable ultrasound (US) protocol for imaging the superficial and deep masticatory muscles and to identify the potential influencers of the measurements. Forty-eight healthy participants without orofacial pain were enrolled. The intra-and inter-rater reliabilities of US measurements for masseter, temporalis, and lateral pterygoid muscles were assessed. Intraclass correlation coefficients for all muscles were greater than 0.6. The generalised estimating equation was used to analyse the impact of age, gender, laterality, and body mass index on the measurements, whereby age and body mass index were likely to be associated with an increase in masticatory muscle thickness. The thickness tended to be lesser in females. Laterality seemed to exert minimal influence on masticatory muscle thickness. Our study shows acceptable reliability of US in the evaluation of superficial and deep masticatory muscle thickness. Future studies are warranted to validate the usefulness of US imaging in patients with oral myofascial pain syndrome.

Decreased mandibular cortical bone quality after botulinum toxin injections in masticatory muscles in female adults

This study aimed to clarify how masticatory muscle atrophy induced by botulinum toxin (BTX) injection affects cortical bone quality of the mandible using 3D modeling technology. A total of 39 young (26.9 ± 6.0 years) and 38 post-menopausal (55.3 ± 6.3 years) females were included. Computed tomography (CT) images were obtained before and after 12 months of treatment. Predictor variables were application of a stabilization splint, and/or two times of BTX injection in the bilateral temporalis and masseter muscles within a six-month interval. Outcome variables were changes in average Hounsfield units (HU) and cortical thickness of region of interest (ROI). 3D mandibular models were reconstructed using CT images, and models were used to calculate average HU and cortical thickness of ROIs, including inferior half of the lateral surface of ascending ramus, coronoid process, and temporomandibular joint condyle. Cortical bone quality at muscle insertion site was influenced by decreased muscle thickness but seemed not to be affected by decreased functional loading. Reduced functional loading seemed to influence cortical bone quality of the condyles. These effects were more remarkable in post-menopausal females. Hence, decreased masticatory muscle thickness may lead to alterations of the mandibular cortical structures, especially in post-menopausal females.

Alterations in the stomatognathic system due to amyotrophic lateral sclerosis.

Objectives:To compare the molar bite force, electromyographic activity, chewing efficiency and thickness of the masseter and temporalis muscles in individuals with amyotrophic lateral sclerosis (ALS) and healthy individuals.Material and Methods:Thirty individuals enrolled in the study were divided into the study group (with ALS, n=15) and control group (healthy individuals, n=15). Data regarding molar bite force (right and left), electromyographic activity (mandibular rest, right and left laterality, protrusion, and maximum voluntary contraction), chewing efficiency (habitual and non-habitual), and masticatory muscle thickness (rest and maximum voluntary contraction) were tabulated and subjected to statistical analysis (Student’s t-test, p≤0.05).Results:Comparisons between the groups demonstrated a statistically significant increase in the electromyographic activity of the right masseter (p=0.03) and left masseter (p=0.03) muscles during mandibular rest; left masseter (p=0.00), right temporalis (p=0.00), and left temporalis (p=0.03) muscles during protrusion; and right masseter (p=0.00), left masseter (p=0.00), and left temporalis (p=0.00) muscles during left laterality, in individuals with ALS as compared with healthy individuals. A statistically significant decrease was observed in the habitual chewing efficiency of the right masseter (p=0.00) and right temporalis (p=0.04) muscles in individuals with ALS. No statistically significant difference between the groups was found the masticatory muscle thickness and maximal molar bite force.Conclusions:ALS may lead to modifications in the activities of the stomatognathic system, including muscular hyperactivity and reduction in chewing efficiency; however, no change has been observed in the masticatory muscle thickness and molar bite force.

Impact of temporomandibular disorders on the stomatognathic system in children.

BackgroundTo evaluate the EMG activity and thickness of right masseter (RM), left masseter (LM), right temporal (RT) and left temporal (LT) muscles and bite force in children with temporomandibular disorders (TMD).Material and MethodsForty five children (mean age 8.8 years; 22 boys and 23 girls) were examined on the basis of the RDC/TMD and the Faces Pain Scale-Revised (FPS-R) was used to determine the level of severity of the signs and symptoms of TMD, resulting in four groups: GI - without TMD (n=10); GII - with mild TMD (n=18), GIII: with moderate TMD (n=12) and GIV: with severe TMD (n=5). The data of electromyographic activity, maximum bite force and muscle thickness were tabulated and submitted to statistical analysis (ANOVA, P≤0.05).ResultsChildren with TMD signs and symptoms had lower EMG activity than children of the control group. There was significant difference among the groups for the LT at rest (P=0.01), right (P=0.03) and left (P=0.05) laterality, and for the LM (P=0.01) and LT (P=0.03) muscles in maximum voluntary contraction. There were no statistically significant differences among the groups regarding muscle thickness. The bite force was lower in the TMD groups than children of the control group, with significant statistical difference for the right region (P=0.03).ConclusionsThe severity of TMD signs and symptoms affected the EMG activity and the molar bite force in children. However, structural changes in the thickness of masticatory muscles are not perceptible in children with TMD signs and symptoms. Key words:Children, temporomandibular disorders electromyographic, bite force, ultrasound.

Association between posterior crossbite, skeletal, and muscle asymmetry: a systematic review.

Of the various malocclusions, unilateral posterior crossbite has often been associated to skeletal and muscular asymmetrical growth and function. To assess, by systematically reviewing the literature, the association between unilateral posterior crossbite (UPCB) and morphological and/or functional asymmetries (i.e. skeletal, masticatory muscle electromyographic (EMG) performance, bite force, muscle thickness, and chewing cycle asymmetries). A literature survey covering the period from January 1965 to June 2015 was performed. Two reviewers extracted the data independently and assessed the quality of the studies. The search strategy resulted in 2184 citations, of which 45 met the inclusion criteria. The scientific and methodological quality of these studies was medium-low, irrespective of the association reported. In several studies, posterior crossbite is reported to be associated to asymmetries in mandibular skeletal growth, EMG activity, and the chewing cycle. Fewer data are available on bite force and masticatory muscle thickness. The relationship between unilateral posterior crossbite and skeletal asymmetry is still unresolved. To date, most of the studies available report a skeletal asymmetric growth. EMG activity of masticatory muscles is different between crossbite and non-crossbite sides. Subjects with UPCB show smaller bite force than non-crossbite subjects. There is no consistency of studies reporting masticatory muscle thickness asymmetry in UPCB subjects. UPCB is associated to an increase in the reverse chewing cycle. The literature available on the subject is of medium-low scientific and methodological quality, irrespective of the association reported. Further investigations with higher sample size, well-defined diagnostic criteria, rigorous scientific methodologies, and long-term control are needed.