The use of ultrasound in the investigation of the muscles of mastication

Assessment of Reliability, Agreement, and Accuracy of Masseter Muscle Ultrasound Thickness Measurement Using a New Standardized Protocol

There is no validated method of assessing masseter muscle thickness (MMT) by ultrasound imaging (US). However, this is important to ensure study and measurement quality of MMT by US in future studies, as MMT differs depending on the examined area. Thus, this study's aim was to present a new standardized method for assessing the MMT by US and to evaluate the reliability, consistency, and accuracy of its measurements. We also compared the results of MMT measurements obtained by US and computer tomography (CT). The study included nine healthy adults. The US and CT scans were collected in a supine rest position with the mandible in relaxed position. US measurements were determined according to a new standardized protocol (with precise probe location). The MMT measured by CT and US over a seven-day interval showed excellent intra-rater reliability. The mean MMT measured by CT was 12.1 mm (1.74) on the right side and 11.9 mm (1.61) on the left side. The mean MMT measured by US was 12.7 mm (2.00) on the right side and 11.5 mm (1.37) on the left side. The mean percent error in MMT measurement between CT and US was below 6%. A strong linear relationship was found between the CT and US measurements of the MMT on both body sides (p < 0.001, r ≥ 0.93). The proposed method of MMT measurement using US demonstrated excellent reliability, yielding results similar to those obtained from CT images. We recommend the use of this standardization protocol in further studies where precise assessment of MMT by US is expected.

Ultrasonographic characteristics of myogenous temporomandibular disorders: A scoping review

OBJECTIVE

To identify the available evidence on the ultrasonographic characteristics of masticatory muscles in subjects with myogenous TMD, as well as the potential use of ultrasonography as a diagnostic and treatment assessment outcomes tool.

METHOD

An electronic search of the PubMed, Web of Science and Scopus databases was performed using the following terms: 'ultrasonography', 'ultrasound', 'masseter', 'temporal', 'masticatory muscles', 'temporomandibular disorders', 'temporomandibular joint disorders'. Full-text articles were obtained from the records after applying the inclusion/exclusion criteria.

RESULTS

Thirteen articles were included for analysis: one comparative cross-sectional study, five case-control studies, six clinical trials and one randomised clinical trial. Main ultrasonographic characteristic assessed were local cross-sectional dimension and intramuscular ultrasonographic appearance. Retrieved studies reported the use ultrasonography for diagnosis or treatment assessment purposes showing heterogeneous results. For diagnosis purposes, the results of local cross-sectional dimension are not consistent; therefore, its diagnostic value for myogenous TMD diagnosis is weak. However, more homogeneous results were observed for intramuscular ultrasonographic appearance showing a higher prevalence of type-II pattern in myogenous TMD subjects than non-TMD subjects. On the other hand, for treatment assessment purposes, muscles were observed thinner after treatment compared to pre-treatment. Also, results of intramuscular ultrasonographic appearance show disappearance or reduction of anechoic areas, higher prevalence of type-II pattern and significant distinction of echogenic bands were observed after treating TMD subjects.

CONCLUSION

Ultrasonography cannot be considered as a diagnostic instrument, but maybe as a complementary tool for treatment assessment of myogenous TMD subjects, even though future research is required to confirm its utility.

Evaluation of the efficacy of pharmacological treatment in patients with temporomandibular joint dysfunctions using ultrasonography

STATEMENT OF PROBLEM

Temporomandibular joint dysfunctions (TMDs) are complex problems affecting the temporomandibular joints (TMJs), masticatory muscles, or both. TMDs are considered muscle pain caused by contraction and ischemia in the masticatory muscles, but evaluation of the efficacy of pharmacological treatment is lacking.

PURPOSE

The purpose of this clinical study was to evaluate the changes in masticatory muscles, joint space, and main arteries supplying the TMJs after pharmacological therapy in patients with TMDs using ultrasonography (USG).

MATERIAL AND METHODS

The TMJ space, masseter and temporal muscles, temporal superficial artery (TSA), and facial artery (FA) were examined using USG in 30 participants with acute TMD pain before and after 10 days of symptomatic treatment with analgesic and myorelaxant. The bilateral masseter and temporal muscle thicknesses, joint space, and end-diastolic minimum velocity (Ved), minimum end-diastolic minimum velocity (Vmin), peak systolic maximum velocity (Vmax), pulsatility index (PI), and resistance index (RI) values of the TSA and FA were measured and compared before and after pharmacological treatment. The relationship between the masseter muscle thickness and the Ved and Vmin values of the TSA and FA before and after pharmacological treatment was analyzed using the paired sample t test; the relationship between the temporal muscle thickness, TMJ spaces, and Vmax, PI, and RI values of the TSA and FA was analyzed using the Wilcoxon signed-rank test (α=.05).

RESULTS

A significant difference was found between the right temporal muscle thickness before and after medication (P=.01), whereas no statistically significant difference was found in the left temporal muscle thickness (P>.05). A significant difference was found between pretreatment and posttreatment bilateral masseter thicknesses at rest (right P=.014; left P=.004). No statistically significant difference was found in the bilateral joint space or Vmax, Vmin, Ved, PI, and RI values of the TSA and FA before and after treatment (P>.05).

CONCLUSIONS

Pharmacological treatment in participants with acute TMD led to a reduction in masseter and temporal muscle thickness but did not significantly affect joint space and local blood flow. USG is a useful diagnostic tool in the diagnosis and follow-up of TMDs.

Ultrasonographic examination of masticatory muscles in patients with TMJ arthralgia and headache attributed to temporomandibular disorders

This study used ultrasonography to compare the thickness and cross-sectional area of the masticatory muscles in patients with temporomandibular joint arthralgia and investigated the differences according to sex and the co-occurrence of headache attributed to temporomandibular disorders (HATMD). The observational study comprised 100 consecutive patients with TMJ arthralgia (71 females and 29 males; mean age, 40.01 ± 17.67 years) divided into two groups: Group 1, including 86 patients with arthralgia alone (60 females; 41.15 ± 17.65 years); and Group 2, including 14 patients with concurrent arthralgia and HATMD (11 females; 33.00 ± 16.72 years). The diagnosis of TMJ arthralgia was based on the diagnostic criteria for temporomandibular disorders. The parameters of the masticatory muscles examined by ultrasonography were subjected to statistical analysis. The pain area (2.23 ± 1.75 vs. 5.79 ± 2.39, p-value = 0.002) and visual analog scale (VAS) score (3.41 ± 1.82 vs. 5.57 ± 12.14, p-value = 0.002) were significantly higher in Group 2 than in Group 1. Muscle thickness (12.58 ± 4.24 mm) and cross-sectional area (4.46 ± 2.57 cm2) were larger in the masseter muscle than in the other three masticatory muscles (p-value < 0.001). When examining sex-based differences, the thickness and area of the masseter and lower temporalis muscles were significantly larger in males (all p-value < 0.05). The area of the masseter muscle (4.67 ± 2.69 vs. 3.18 ± 0.92, p-value = 0.004) and lower temporalis muscle (3.76 ± 0.95 vs. 3.21 ± 1.02, p-value = 0.049) was significantly smaller in Group 2 than in Group 1. An increase in VAS was significantly negatively correlated with the thickness of the masseter (r =  - 0.268) and lower temporalis (r =  - 0.215), and the cross-sectional area of the masseter (r =  - 0.329) and lower temporalis (r =  - 0.293). The masseter and lower temporalis muscles were significantly thinner in females than in males, and their volumes were smaller in patients with TMJ arthralgia and HATMD than in those with TMJ arthralgia alone. HATMD and decreased masseter and lower temporalis muscle volume were associated with increased pain intensity.

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

OBJECTIVE

Bruxism 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.

METHODS

The 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).

RESULTS

No 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).

CONCLUSION

The 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.

Surgical management of intramuscular hemangioma of left masseter muscle: A case report

Hemangiomas are benign soft tissue tumors which are congenital and occur due to abnormal proliferations of blood vessels. Most common location of hemangiomas is subcutaneous adipose tissue, but skeletal muscle hemangiomas are very rare which make up to 0.8% of all hemangiomas. Usually, the intramuscular lesions are common in thigh region and calf muscles and are relatively rare in the facial muscles. Long-standing lesions results in phleboliths, and this may cause some symptoms. Conventional treatment of these isolated lesions may not yield satisfactory results. Hence, surgical excision of the lesion in toto results in aesthetically pleasing results with low chances of recurrence. In this article, we report a case of a left masseter intramuscular hemangioma in 19-year-old patient which was successfully managed by complete surgical excision.

Overview of Ultrasound in Dentistry for Advancing Research Methodology and Patient Care Quality with Emphasis on Periodontal/Peri-implant Applications

BACKGROUND

Ultrasound is a non-invasive, cross-sectional imaging technique emerging in dentistry. It is an adjunct tool for diagnosing pathologies in the oral cavity that overcomes some limitations of current methodologies, including direct clinical examination, 2D radiographs, and cone beam computerized tomography. Increasing demand for soft tissue imaging has led to continuous improvements on transducer miniaturization and spatial resolution. The aims of this study are (1) to create a comprehensive overview of the current literature of ultrasonic imaging relating to dentistry, and (2) to provide a view onto investigations with immediate, intermediate, and long-term impact in periodontology and implantology.

METHODS

A rapid literature review was performed using two broad searches conducted in the PubMed database, yielding 576 and 757 citations, respectively. A rating was established within a citation software (EndNote) using a 5-star classification. The broad search with 757 citations allowed for high sensitivity whereas the subsequent rating added specificity.

RESULTS

A critical review of the clinical applications of ultrasound in dentistry was provided with a focus on applications in periodontology and implantology. The role of ultrasound as a developing dental diagnostic tool was reviewed. Specific uses such as soft and hard tissue imaging, longitudinal monitoring, as well as anatomic and physiological evaluation were discussed.

CONCLUSIONS

Future efforts should be directed towards the transition of ultrasonography from a research tool to a clinical tool. Moreover, a dedicated effort is needed to introduce ultrasonic imaging to dental education and the dental community to ultimately improve the quality of patient care.

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.

Single implant overdenture reinforced with a metallic framework: A 2-year clinical follow-up

INTRODUCTION

To prevent single-implant overdenture (SIO) fracture, the inclusion of a framework in the overdenture has been suggested. However, no investigations verified their benefits.

OBJECTIVE

To evaluate prosthetic maintenance events, patient satisfaction, and mastication of SIO reinforced by metallic framework users.

MATERIAL AND METHODS

Fifteen volunteers had a new set of complete dentures converted into an SIO containing a framework. Maintenance events were recorded, while patient satisfaction was assessed using a visual analog scale. Masticatory performance (MP) was evaluated using the sieving method, maximum bite force (MBF) by pressure sensors, and masseter thickness by ultrasound. Measurements were performed 2, 12, and 24 months after SIO use. Repeated-measures ANOVA and paired Student's t-tests (p < 0.05) were applied.

RESULTS

Matrix exchange was the most prevalent maintenance event (83.6%), and no SIO was fractured during the entire follow-up. Satisfaction with the SIO stability decreased (p < 0.01) after 12 months. MP did not change between evaluations (p > 0.05). Conversely, MBF and masseter thickness improved after 12 and 24 months of SIO use (p < 0.05).

CONCLUSIONS

Reinforced SIO did not fracture during 2 years but requires maintenance. It improves bite force and muscle thickness, maintaining MP values. Satisfaction with SIO stability decreased in the first year of use.

Effect of isometric exercises on the masseter muscle in older adults with missing dentition: a randomized controlled trial

Maintaining oral function in older individuals with missing teeth is important for leading a healthy and independent life. This study aimed to evaluate whether simple isometric exercises can maintain and improve the oral function [maximum occlusal force (MOF) and masticatory ability (MA)] and the masticatory muscle properties [masseter muscle thickness (MMT) and echo intensity (MMEI)] in older adults during the maintenance phase of removable prosthetic treatment. Participants were randomly categorized into the intervention and control groups. The mouthpieces were distributed, and participants were instructed to use them for exercising. The intervention group was instructed to perform maximum clenching for 10 s, whereas the control group was instructed to tap the teeth at an arbitrary speed for 10 s. Both were repeated five times at an interval of 5 s between each activity and twice daily for 4 weeks. The outcomes were measured after a month of exercise. The intervention group showed a significant improvement in the MOF, MMT during contraction, MMT at rest and MMEI during contraction. There were no significant differences in the MA and MMEI at rest. In the control group, no improvement was observed in any of the parameters. When the isometric exercises were performed using a mouthpiece, there was an improvement in the oral function and masseter muscle properties in older individuals with Eichner B status who used dentures.

Ultrasonographic Measurement of Masseter Muscle Thickness Associates with Oral Phase Dysphagia in Institutionalized Elderly Individuals

BACKGROUND & AIMS

Oral phase dysphagia is dependent on ability to chew. As people age, general muscle atrophy contributes to decreased masseter strength. The main objective of this study was to assess the relationship between the thickness of the masseter muscle measured by ultrasonography and the presence of dysphagia in a group of institutionalized elderly people. As a secondary objective, we aimed to establish cutoff points of masseters muscle thickness (MMT) to identify elderly individuals at risk of oral dysphagia.

METHODS

Cross-sectional study of all residents from 3 nursing homes. All individuals underwent ultrasonographic measurements of left and right MMT and were classified according to the presence of dysphagia assessed by both the EAT-10 screening questionnaire and the volume-viscosity swallow test (V-VST).

RESULTS

469 patients (69% women, mean age 84.7 yrs) were recruited. Dysphagia was present in 41.6% and 26% of individuals according the EAT-10 and V-VST, respectively. Multivariate logistic regression showed that 1 mm increase in MMT reduced the risk of dysphagia by 21% according to the EAT-10 tool and by 30% using the V-VST after adjusting for age, sex, mini-nutritional assessment score, and body mass index. We used receiver operative characteristic (ROC) curves to identify cutoff points of MMT to detect dysphagic individuals according to either EAT-10 or V-VST.

CONCLUSIONS

The MMT measured by ultrasonography is reduced in elderly individuals with dysphagia. Based on MMT, clinicians may be better informed about the patients'´ ability to masticate solid foods and identify potential nutrient deficiencies in geriatric settings.

Ultrasound dimensional changes of the anterior belly of the digastric muscle induced by orthognathic surgery and botulinum toxin A injection in Class II malocclusion

OBJECTIVES

The aim of the study is to evaluate the ultrasonographic dimensional changes of the anterior belly of the digastric muscle (ABDM), occurring after intramuscular botulinum toxin A (BTX-A) injection during orthognathic surgery, in a series of five Class II malocclusion patients.

METHODS

All the patients received 20 units of BTX-A, into both ABDM, intraoperatively. The length, width and cross-sectional area (CSA) of the ABDM were ultrasonographically measured at three different time points: T₀ (preoperatively), T₁ (postoperatively at 2 weeks after the surgical intervention), and T₂ (postoperatively at 6-9 months).

RESULTS

A statistically significant higher length of the ABDM was noted postoperatively, at T₁ and T₂ compared to T₀. The patients showed an increased length by 12.2% at 2 weeks postoperatively and continued to increase, reaching 24.6% at 6 months. A decreased width of ABDM by 6.5% at T₁ compared with T₀ was also found.

CONCLUSIONS

Postoperative ultrasound (US) follow-up measurements in patients with Class II malocclusion, orthognathic surgery and intraoperative BTX-A injection in the ABDM, showed dimensional changes of the muscle, with elongation and thinning. The muscular modifications were more pronounced at 6 months postoperatively, indicating consistency and potential benefit of using BTX-A in reducing the risk of surgical relapse. Further data on longer-term follow-up and larger number of cases are necessary.

Methods of Masseter and Temporal Muscle Thickness and Elasticity Measurements by Ultrasound Imaging: A Literature Review

BACKGROUND

The positive correlation between changes in the morphology of masseter and temporal muscles and some disorders, inclines diagnosticians to search for an effective method of assessing muscle thickness and elasticity. Ultrasound imaging, as a relatively simple and cheap method, seems to be a useful diagnostic tool.

OBJECTIVE

The aim of this study was to present the existing ultrasound imaging methods in the assessment of the elasticity and thickness of the masseter and temporal muscles.

METHODS

The literature review has been done with a focus on the accurate description of the masseter and/or temporal muscle examination by ultrasonography imaging methods. Articles were categorized into two groups. The first group included articles in which muscle thickness was assessed by ultrasound imaging. The second group concerned the elasticity aspect of mentioned muscles.

RESULTS

It is difficult to achieve an objective protocol of masseter and temporal thickness assessment by ultrasonography and there is no method that has been fully verified in terms of reliability. The shear-wave sonoelastography revealed higher-level reliability of masseter muscle elasticity than strain sonoelastography. During the shear-wave sonoelastography, the effect of scan plane in relation to masseter muscle pennation and the day-to-day variation were statistically significant. With regard to elasticity of temporal muscle, further research is needed.

CONCLUSION

This review has shown that there is a limited number of methods for masseter and temporal muscle thickness and elasticity measurements by ultrasonography. All procedures (methods) were not fully verified in terms of reliability and agreement. Thus, it is still necessary to develop standardized procures to assess thickness and elasticity of the masseter and temporal muscles with appropriate reliability and accuracy.

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.

Comparison of Ultrasonic Thickness of Masseter Muscle Between Individuals With and Without Severe Forward Head Posture: A Cross-Sectional Study

OBJECTIVE

In this cross-sectional descriptive-analytical study, we sought to compare the ultrasonic thickness of the masseter muscle in people with severe forward head posture vs people without forward head posture, and to determine sex differences in muscle thickness.

METHODS

Thirty-eight volunteers (19 with normal head postures and 19 with severe forward head postures), aged 18 to 35 years, entered the study. The severity of the forward head posture was measured by a plumb line and the craniovertebral angle drawn on the recorded images. Based on the recorded images, the masseter muscle thickness was also measured by a 7.5-MHz linear transducer using an ultrasound device in the seated position with 3 mouth positions (closed, half open, and fully open).

RESULTS

The results showed that the head posture affects masseter thickness significantly (P = .01), with masseter thickness significantly lower in the participants without severe forward head postures compared to those with severe forward head postures in the closed, half-open, and fully open mouth positions (P < .05). Comparing the mean masseter thickness across sexes showed that the masseter muscle is significantly thicker in men compared to women (P = .01).

CONCLUSION

Head posture and thickness of the masseter muscle are linked, as the masseter muscle was thicker in all 3 positions in the participants with severe forward head postures.

The ultrasonographic measurement of muscle thickness in sarcopenia. A prediction study

BACKGROUND

Sarcopenia is a common disease in the elderly. Although extensive research has been conducted on muscle mass and quality assessment tools, there are still certain drawbacks preventing their universal use.

AIM

The aim of this study was the evaluation of the thickness of head, neck, upper and lower limb muscles measured with ultrasonography, as a potential predictory tool in sarcopenia.

DESIGN

Prediction study.

SETTING

The Outpatient Sarcopenia Clinic of the Rehabilitation Department of the University Hospital of Patras.

POPULATION

Ninety-four individuals (27 men and 67 women) with a mean age of 75.6 years (SD=6.6), referred for sarcopenia screening, participated in this study.

METHODS

The muscle thickness was measured with transverse and longitudinal ultrasound scans bilaterally.

RESULTS

The thickness of the geniohyoid and medial head of gastrocnemius muscle in all ultrasound sections, and the thickness of the rectus femoris and vastus intermedius muscle, in specific sections, was found to be significantly decreased in patients with sarcopenia (P<0.05). The Receiver Operating Characteristic (ROC) curve analysis of the ultrasound muscle thickness measurements resulted in a significant association with sarcopenia. In the case of the geniohyoid muscle, the measured area under the ROC curve was found to be the highest (0.79). The optimal cut-off for the prediction of sarcopenia from the geniohyoid muscle was 0.65 cm with sensitivity equal to 75.0% and specificity equal to 66.7%.

CONCLUSIONS

The results of this study have shown that the thickness of the neck and lower limb muscles measured ultrasonographically can be utilized in the prediction of sarcopenia with high sensitivity and specificity.

CLINICAL REHABILITATION IMPACT

The prevalence of sarcopenia in the geriatric population and the rehabilitation wards is reported to be high. Therefore, an easy, fast, low cost and with no risk, widely available method such as ultrasonography could be an extremely valuable tool for the screening and follow-up of sarcopenia.

Early and long-term changes in the muscles of the mandible following orthognathic surgery

OBJECTIVES

The aim of the present study is to evaluate the early and long-term postoperative dimensional changes of the muscles of the mandible in patients with orthognathic surgery for class II and class III malocclusions by using ultrasonography (US).

MATERIAL AND METHODS

Twenty-six patients who underwent bimaxillary orthognathic surgery for class II or class III malocclusions (14 and 12 patients, respectively) were ultrasonographically examined. The length, width, and cross-sectional area of the masseter and suprahyoid muscles were measured at three different time points: T₀ (preoperatively), T₁ (early postoperatively at 1 month after the surgery), and T₂ (late postoperatively at 9 months). A repeated measures ANOVA was used to calculate statistically significant dimensional changes of the mandibular muscles.

RESULTS

Statistically significant dimensional changes were found postoperatively in class II malocclusion patients only. The digastric muscle showed higher values for the length and lower values for the width (p < .05) at T₁. The geniohyoid muscles were higher in length at T₁ and lower in cross-sectional area (CSA) (p < .05) at T₂. A decreased measured length and an increased measured width were found in case of the mylohyoid muscle (p < .05) at T₂. The early and long-term postoperative dimensional changes of the masseter muscle were not statistically significant.

CONCLUSIONS

The mandibular muscles showed a variable adaptive response to the orthognathic surgery. US should be considered for the long-term follow-up of muscular dimensional changes in class II malocclusion patients.

CLINICAL RELEVANCE

From a clinical perspective, US is a reliable, non-invasive, and widely available method, which allows monitoring the postoperative muscular changes occurring in class II malocclusion patients.

Masseter Deoxygenation in Adults at Risk for Temporomandibular Disorders

Patients with muscular temporomandibular disorder (TMD) present with abnormal oxygenation of the jaw muscles. Nonetheless, the deoxygenation pattern of jaw muscles of healthy subjects with frequent wake-time tooth-clenching episodes, who are at greater risk for TMD, has never been investigated. This case-control study compared the deoxygenation of the masseter during standardized tasks between TMD-free individuals with frequent self-reports of wake-time clenching and those with infrequent self-reports. University students ( N = 255) filled out the Oral Behavior Checklist. Fourteen females with high versus low scores-high parafunctional (HP) group ( n = 7, ≥80th percentile of score distribution) versus low parafunctional (LP) group ( n = 7, ≤20th percentile)-completed 2 sessions during which they clenched at their maximum voluntary contraction (MVC) for 2 min and at 10% to 20% MVC for 20 min. Tissue oxygen saturation (StO₂) and changes in oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin of the masseter were measured via near-infrared spectroscopy and analyzed with a generalized mixed effect model. A significant interaction effect (task × study group) was found on all outcome measures, indicating that the deoxygenation pattern of the HP group differed from the LP group (all P < 0.001). MVC of the masseter induced an almost 5-times-greater reduction of StO₂ in the HP group as compared with the LP group ( P = 0.023). However, the relative increase in StO₂ at rest after the MVC was similar between groups ( P > 0.05). At the end of the prolonged MVC task (10% to 20%), the blood flow (change in total hemoglobin) was almost 6 times higher in the LP group as compared with baseline. On the contrary, it increased minimally in the HP group (all P < 0.001). Healthy individuals at risk for TMD have abnormalities in masseter deoxygenation. Future prospective studies are needed to test whether this contributes to the onset of muscular TMD.

Influence of lower complete denture use on masseter muscles and masticatory function: A longitudinal study

BACKGROUND

Edentulism can reduce mastication, leading to changes in food pattern, with possible consequences to masticatory muscle thickness.

OBJECTIVES

This study verified masticatory function and oral perception in subjects who did not use lower CDs, and whether the insertion of new upper and lower CDs would improve such variables.

METHODS

Fifteen edentulous elderly who wore only the upper CD were selected and received new upper and lower CD. Volunteers were evaluated at baseline and after 1, 3 and 6 months of new prosthesis use. Masticatory performance (MP) was assessed by the sieving method (X₅₀ values). Masseter thickness (MT) was evaluated by ultrasonography. Oral sensorial ability (OSA) was assessed by oral stereognosis test and maximum tongue pressure (MTP) was verified by pressure sensors. Data were submitted to repeated measures ANOVA and Tukey-Kramer posthoc tests (α = 0.05). Correlation between OSA and MTP was verified by Person's correlation.

RESULTS

X₅₀ and MTP decreased (P < 0.05) after 1 month and remained stable (P > 0.05) for next assessments. After 3 months, MT in rest position was increased (P < 0.05), while during maximum voluntary contraction 1 month was enough to increase MT (P < 0.05). There were no differences for OSA (P > 0.05) and no correlation between OSA and MTP.

CONCLUSION

Masticatory performance and masseter thickness of elderly who did not use the lower dentures were improved after 2 months using new upper and lower CDs. However, new CDs in both dental arch decreased MTP. Brazilian Registry of Clinical Trials (ReBEC #RBR-37gdst).

Experimental and Numerical Characterization of the Mechanical Masseter Muscle Response During Biting

Predictive simulations of the mastication system would significantly improve our understanding of temporomandibular joint (TMJ) disorders and the planning of cranio-maxillofacial surgery procedures. Respective computational models must be validated by experimental data from in vivo characterization of the mastication system's mechanical response. The present pilot-study demonstrates the feasibility of a combined experimental and numerical procedure to validate a computer model of the masseter muscle. An experimental setup is proposed that provides a simultaneous bite force measurement and ultrasound-based visualization of muscle deformation. The direct comparison of the experimentally observed and numerically predicted muscle response demonstrates the predictive capabilities of such anatomically accurate biting models. Differences between molar and incisor biting are investigated; muscle deformation is recorded for three different bite forces in order to capture the effect of increasing muscle fiber recruitment. The three-dimensional (3D) muscle deformation at each bite position and force-level is approximatively reconstructed from ultrasound measurements in five distinct cross-sectional areas (four horizontal and one vertical cross section). The experimental work is accompanied by numerical simulations to validate the predictive capabilities of a constitutive muscle model previously formulated. An anatomy-based, fully 3D model of the masseter muscle is created from magnetic resonance images (MRI) of the same subject. The direct comparison of experimental and numerical results revealed good agreement for maximum bite forces and masseter deformations in both biting positions. The present work therefore presents a feasible in vivo measurement system to validate numerically predicted masseter muscle contractions during mastication.

Relationship of aging, skeletal muscle mass, and tooth loss with masseter muscle thickness

Background

Previous studies have reported a relationship between masseter muscle thickness and tooth loss or limb muscle thickness. However, it is not yet known whether masseter muscle thickness is related to appendicular skeletal muscle mass, and grip strength. The purpose of this study was to determine which of the two variables—tooth loss or appendicular skeletal muscle mass index—is more strongly related to masseter muscle thickness, and to identify a suitable indicator of decreasing masseter muscle thickness in healthy elderly individuals.

Methods

Grip strength, walking speed, body weight, skeletal muscle mass index, tooth loss, and masseter muscle thickness at rest and during contraction were determined in 97 community-dwelling elderly individuals aged ≥65 years (men: 44, women: 53). Masseter muscle thickness was chosen as the dependent variable, while age, skeletal muscle mass index, body weight, grip strength, and tooth loss were chosen as the independent variables. Multiple regression analysis was conducted using the stepwise regression method.

Results

In men, grip strength was the only independent predictor of masseter muscle thickness at rest. Tooth loss and grip strength were independent predictor of masseter muscle thickness during contraction. In women, tooth loss was the independent predictor of masseter muscle thickness both at rest and during contraction, while grip strength and body weight were the independent predictor of masseter muscle thickness at rest only.

Conclusions

We confirmed that in healthy elderly individuals, tooth loss has a stronger relationship with masseter muscle thickness than aging and skeletal muscle mass index do. Masseter muscle thickness in both elderly men and women is also associated with grip strength, suggesting that grip strength can be used as an indicator of masseter muscle thickness in this population.

Cavernous hemangiomas of the temporalis muscle with prominent formation of phleboliths: Case report and review of the literature

RATIONALE

Hemangiomas are benign tumors characterized by an abnormal proliferation of blood vessels, most often occur in the skin and subcutaneous tissue, intramuscular hemangioma, a distinctive type of hemangioma within the skeletal muscle, account for <1% of all hemangiomas, temporalis muscle is a very uncommon site, cavernous hemangioma of the temporalis muscle with prominent formation of phleboliths is rare reported.

PATIENT CONCERNS

A 62-year-old man presented with a slowly increased mass in his right temporal fossa.

DIAGNOSES

Computed tomography (CT) scan showed the lesion across the zygomatic arch, with many calcified nodules differ in sizes and no erosion to the bone, magnetic resonance imaging (MRI) showed an oval lesion with hypointense and isointense on T2-weighted imaging within the temporal muscle, and preoperation diagnosis was hemangioma.

INTERVENTIONS

The tumor was resected under general anesthesia.

OUTCOMES

The mass was excised completely, and the histopathology examination confirmed the diagnosis of cavernous hemangioma with prominent formation of phleboliths. The patient recovered very well without dysfunctions.

LESSONS

Cavernous hemangioma should be suspected when mass occurs in this region. CT and MRI are important for the early diagnosis of tumor, and resection the tumor completely is recommended.

Integration of ultrasound imaging into pre-clinical dental education

INTRODUCTION

Patients have complex healthcare needs and typically require more than one healthcare discipline to address issues regarding their health. Interprofessional teams of healthcare professionals may be able to address these complex needs and improve patient outcomes by combining resources. To evaluate the feasibility of integrating ultrasound into a dental school curriculum to teach anatomy as part of an interprofessional education experience, the current study surveyed first-year dental students to determine their perceptions of the integration of ultrasound techniques into the curriculum.

MATERIALS AND METHODS

Ultrasound laboratory exercises were developed for first-year dental students as part of their anatomy course. The exercises were focused on head, neck and abdominal anatomy. To assess student perception of the integration of ultrasound into the dental curriculum, a survey was created specifically for the current study.

RESULTS

Between 2013 and 2015, two classes of first-year dental students participated in the ultrasound laboratory exercise and completed the survey (n = 83). Student survey responses suggested ultrasound was a valuable teaching tool because it allowed them to visualise anatomical structures using live imaging. They also agreed that the ultrasound laboratory exercises were an efficient learning tool, but the majority did not believe that they would use ultrasound regularly in their future practice.

CONCLUSIONS

Results of the current study suggested first-year dental students were satisfied with the integration of ultrasound techniques into the dental curriculum. Survey results indicated that the students enjoyed the ultrasound laboratory exercise and felt ultrasound was an effective learning tool.

Evaluation of masseter muscles in relation to treatment with removable bite-blocks in dolichofacial growing subjects: A prospective controlled study

INTRODUCTION

The aim of this prospective study was to evaluate the effects of posterior bite-blocks on masseter muscles and on facial growth in prepubertal dolichofacial subjects.

METHODS

The treatment group comprised 21 consecutive prepubertal dolichofacial patients treated with rapid maxillary expansion followed by mandibular removable bite-blocks. Lateral cephalograms and ultrasonographic scans of the masseter muscles were made before (T1) and after (T2) treatment with bite-blocks. The treatment group was compared with a control group of 21 subjects matched for sex, age, and skeletal vertical pattern. An independent samples t test was used to compare the T1 to T2 changes in ultrasonographic scan measurements between the treatment group and the control group, and the T1 to T2 cephalometric changes in the treatment group. Regression analysis was performed to investigate associations between masseter muscle thickness and cephalometric treatment outcomes.

RESULTS

Masseter muscle thickness showed a statistically significant decrease (-0.7 mm) in the treatment group compared with an increase (+0.6 mm) in the control group. A significant anterior rotation of the mandibular plane was observed in the treatment group as well as significant increases in overbite (1.8 mm) and total posterior facial height (1.5 mm). No significant associations were found between masseter muscle thickness and treatment outcomes apart from a tendency for overbite to increase more in subjects with thicker muscles.

CONCLUSIONS

Treatment with removable bite-blocks produced a decrease in masseter muscle thickness and a reduction in vertical facial dimensions due to upward and forward rotation of the mandible. No significant correlation was found between the pretreatment masseter muscle thickness and the T1 to T2 cephalometric changes in the treatment group.

Recent advances of ultrasound imaging in dentistry--a review of the literature

Ultrasonography as an imaging modality in dentistry has been extensively explored in recent years due to several advantages that diagnostic ultrasound provides. It is a non-invasive, inexpensive, painless method and unlike X-ray, it does not cause harmful ionizing radiation. Ultrasound has a promising future as a diagnostic imaging tool in all specialties in dentistry, for both hard and soft tissue detection. The aim of this review is to provide the scientific community and clinicians with an overview of the most recent advances of ultrasound imaging in dentistry. The use of ultrasound is described and discussed in the fields of dental scanning, caries detection, dental fractures, soft tissue and periapical lesions, maxillofacial fractures, periodontal bony defects, gingival and muscle thickness, temporomandibular disorders, and implant dentistry.

Three-dimensional evaluation of masseter muscle in different vertical facial patterns: a cross-sectional study in growing children

The aim of the present study was to analyze the anatomical three-dimensional (3D) characteristics of masseter muscle in growing subjects with different vertical patterns by using an ultrasound (US) method. The sample comprised 60 prepuberal subjects (33 males, 27 females) with a mean age of 11.5 ± 1.6 years with late mixed or permanent dentition and Class I molar and skeletal relationship. For each subject, a lateral cephalogram was required, and according to the mandibular plane angle (Frankfort horizontal plane/mandibular plane angle [FMA]), the subjects were divided into three groups of different underlying vertical facial patterns: brachyfacial: FMA < 22°, mesofacial: 22° ≤ FMA ≤ 28°, and dolichofacial: FMA > 28°. For each subject, an US scan was carried out to analyze the width, the thickness, the cross-sectional area, and the volume of the masseter muscle. Mean differences in measurements between vertical facial subgroups were contrasted by means of analysis of variance (ANOVA) with Tukey's post hoc tests (p < 0.05). Measurements of the whole masseter in dolichofacial patients were significantly smaller when compared with brachyfacial and mesofacial individuals during relaxation and contraction. The volume of the masseter decreased significantly by 10% going from the brachyfacial group to the mesofacial group and from the mesofacial group to the dolichofacial group with no difference between the left and the right sides. A significant negative correlation was found between the US measurements and the divergency (FMA°). Ultrasound is a technique indicated in children for evaluating muscles of mastication in vivo. Growing patients with a dolichofacial vertical pattern present with a reduced dimension of the masseter when compared with brachyfacial and mesofacial subjects.

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.

Intramuscular hemangioma presenting with multiple phleboliths: a case report

A rare case of intramuscular hemangioma of the masseter muscle with multiple phleboliths is described, highlighting features evident in plain radiography, ultrasound, and magnetic resonance imaging (MRI). A 21-year-old woman presented with a complaint of swelling of the right masseter muscle. A plain radiograph from the soft tissue of the right cheek showed a large number of round, target-like radiopacities that varied in size. Ultrasound revealed a lobulated cystic lesion in the right masseter muscle with increased echogenicity. MRI showed a space-occupying lesion in the right masseter muscle, which was isointense on T1-weighted image close to the muscle tissue and hyperintense on T2-weighted image, containing fields with no signal septations. A plain soft tissue radiograph can demonstrate phleboliths and aid in the diagnosis of an intramuscular hemangioma. In addition, nonionized techniques such as ultrasound and MRI can provide useful information to clinicians regarding the location of calcifications and the structure of masses.

Caracterização eletromiográfica e ultrassonográfica da função mastigatória em indivíduos com oclusão normal

OBJETIVO: Caracterizar o controle motor dos músculos masseter e temporal e a morfologia do músculo masseter em atividades da função mastigatória em indivíduos com oclusão normal; verificar a compatibilidade entre os exames de eletromiografia de superfície (EMGs) e ultrassonografia (USG). MÉTODOS: Participaram 22 indivíduos adultos, de ambos os gêneros, sem alterações no sistema miofuncional orofacial. Os procedimentos adotados para avaliação dos participantes foram: EMGs dos músculos masseteres (MM) e temporais (MT); e USG dos MM, na realização de três tarefas - repouso muscular, apertamento dentário com algodão, apertamento dentário sem algodão. RESULTADOS: Para análise estatística dos dados foram utilizados os testes de Kolmogorv-Smirnov, teste-T pareado e Correlação de Spearman, com nível de significância de 5%. Na EMGs observou-se diferença entre a ativação de MM e MT no apertamento dentário com e sem algodão, sendo MT mais ativo que MM em ambas as tarefas. Não foram observadas diferenças entre as hemifaces, tanto na EMGs quanto na USG. Observou-se também correlação positiva entre os exames na condição de apertamento dentário sem algodão esquerdo e na condição de apertamento dentário esquerdo com algodão, e tendência à significância no apertamento dentário direito sem algodão. CONCLUSÃO: A associação da EMGs e USG na investigação da funcionalidade muscular traz importantes informações sobre fisiologia da musculatura esquelética. Os resultados do presente estudo indicam haver correlação entre a EMGs e a USG, ou seja, o aumento da atividade elétrica e o aumento correspondente da espessura do músculo.

Ultrasound measurements of the masseter muscle as predictors of cephalometric indices in orthodontics: a pilot study

This study investigated the potential of ultrasound measurements of the masseter muscle to accurately predict indices normally derived from cephalograms. Masseter muscle measurements on 11 adults (22 to 30 y) were made using lateral cephalometrics and extended field-of-view ultrasound. The ultrasound technique was validated in a simulation pilot study using 12 dry skulls and raw chicken breasts. Twenty cephalometric variables were analyzed against four ultrasound measurements of the masseter muscle. Highly significant correlations (r = 0.81-0.85, p = 0.001-0.002) between ultrasound measurements of the masseter muscle and cephalometric measurements representing the length of the superficial masseter muscle, the length and shape of the mandible and vertical facial proportions were demonstrated. Predictive equations from regression analyses were constructed to deduce ramus length and shape from the ultrasound measurements. The results provide pilot data suggesting that ultrasound is a potential clinical tool for sequential evaluation of masseter muscle length in orthodontics and facial muscle growth studies.

Electromyographic activity and thickness of masticatory muscles in children with unilateral posterior crossbite

The aim of this study was to assess the electromyographic (EMG) activity and thickness of the masseter and anterior temporalis muscles in children with unilateral posterior crossbite (PCB). Thirty-six children (22 boys, 14 girls, and mean age of 8.8 +/- 1.1 years) were divided into the following groups: The case group with 20 PCB patients (10 on the left side, 10 on the right side); the control group with 16 normal occlusion (NOccl) subjects. EMG activity was recorded with bipolar surface electrodes at rest and during maximal clenching. The muscle thickness was measured with real-time ultrasound. Data were compared between groups and between sides. The correlation between EMG activity and muscle thickness was also evaluated. The data were analyzed using the Shapiro-Wilks test, Pearson's correlation and Spearman as appropriate, paired and unpaired t- test, and Mann-Whitney test. The results revealed that the masseter of the crossbite side was more active than that of the non-crossbite side in PCB group during maximal clenching. The comparisons of EMG activity between PCB and NOccl groups revealed some variability in the results, depending on the crossbite side. The ultrasonographic evaluation did not show statistically significant differences between groups, nor between sides in the PCB and NOccl groups. Significant correlation between EMG activity and thickness was observed only in the left masseter in the NOccl group. In conclusion, these findings showed that asymmetric muscle activity of the masticatory muscles was not related to the thickness of these muscles in children with PCB.