Masseter muscle thickness measured by ultrasonography and its relation to facial morphology

Measurement plane of the cross-sectional area of the masseter muscle in patients with skeletal Class III malocclusion: An artificial intelligence model

INTRODUCTION

This study aimed to determine a measurement plane that could represent the maximum cross-sectional area (MCSA) of masseter muscle using an artificial intelligence model for patients with skeletal Class III malocclusion.

METHODS

The study included 197 patients, divided into subgroups according to sex, mandibular symmetry, and mandibular plane angle. The volume, MCSA, and the cross-sectional area (CSA) at different levels were calculated automatically. The vertical distance between MCSA and mandibular foramen, along with the ratio of the masseter CSA at different levels to the MCSA (R), were also calculated.

RESULTS

The MCSA and volume showed a strong correlation in the total sample and each subgroup (P <0.001). The correlation between the CSA at each level and MCSA was statistically significant (P <0.001). The peak of the r and the correlation coefficient between the CSA at different levels and MCSA were mostly present 5-10 mm above the mandibular foramen for the total sample and the subgroups. The mean of RA5 to RA10 was >0.93, whereas the corresponding correlation coefficient was >0.96, both for the entire sample and for the subgroups.

CONCLUSIONS

MCSA could be used as an indicator for masseter muscle size. For patients with skeletal Class III malocclusion, the CSA 5-10 mm above the mandibular foramen, parallel to the Frankfort plane, could be used to estimate the masseter muscle MCSA.

Changes in masseter muscle morphology after surgical-orthodontic treatment in patients with skeletal Class III malocclusion with mandibular asymmetry: The automatic masseter muscle segmentation model

INTRODUCTION

This study evaluated the masseter muscle changes after surgical-orthodontic treatment in patients with a skeletal Class III malocclusion using automatic segmentation.

METHODS

Images of 120 patients with skeletal Class III malocclusion were obtained and reconstructed at T0 (pretreatment), T1 (presurgery), and T2 (6-12-month postsurgery). The patients were divided into symmetrical and asymmetrical groups. The volume, major axis length, maximum cross-sectional area, horizontal cross-sectional area 5 mm above the mandibular foramen (CSAF), and orientation were calculated automatically.

RESULTS

In the asymmetrical group, the volume and major axis length on the deviated side were lower than on the nondeviated side at T0, T1, and T2 (P <0.05). There were no significant differences in maximum cross-sectional area and CSAF bilaterally. The orientation was coronally more vertical and sagittally more forward on the deviated side (both P <0.001). In the symmetrical group, there were no significant bilateral differences at T0, T1, and T2. The volume, major axis length, and CSAF decreased, and the coronal orientation was more vertical on the nondeviated side at T2 than at T0 in both groups (P <0.05). The coronal plane orientation was more inclined on the deviated side at T2 than at T0 in the asymmetrical group (P <0.05).

CONCLUSIONS

The smaller volume on the deviated side at T2 indicates the need for myofunctional training after surgery. The masseter muscle volume and the cross-sectional area did not recover to the preorthodontic levels. Studies with longer follow-up durations are needed to confirm these findings.

A Multicenter Phase II Study Evaluating the Safety and Efficacy of Botulax in Asian Patients with Benign Masseteric Hypertrophy

BACKGROUND

Benign masseteric hypertrophy (BMH) is a condition in which the thickness of the masseter muscle is increased, resulting in jawline prominence with an undesirable cosmetic appearance. Botulinum toxin type A (BTA) injection is a promising treatment option, but its effective dose remains debated.

METHODS

Adults older than 19 diagnosed with BMH through visual examination and palpation related to a masseter muscle prominence were selected, and 80 patients were randomly assigned into five groups (placebo group and four groups with different doses of BTA: 24 U, 48 U, 72 U, or 96 U, on both sides of the jaw) and treated with placebo or BTA once at their baseline visit. During each follow-up, the treatment efficacy was evaluated with ultrasound examination of the masseter muscle, three-dimensional facial contour analysis, visual evaluation by the investigator, and patient satisfaction evaluation.

RESULTS

The mean age of the 80 patients was 42.7 ± 9.98 years; 68.75% were women. The mean change in masseter muscle thickness during the maximum clenching state after 12 weeks of drug administration compared with baseline in the 24-U, 48-U, 72-U, and 96-U groups were -2.33 ± 0.41 mm, -3.35 ± 0.42 mm, -2.86 ± 0.42 mm, and -3.79 ± 0.42 mm, respectively. All treatment groups showed a statistically significant decrease compared with placebo. Regarding subjective satisfaction, all treatment groups, except the 24-U group at 4 weeks, showed higher satisfaction than the placebo group during all visits. No significant adverse events were noted.

CONCLUSION

BTA administration of at least 48 U for BMH is more cost-effective than high-dose units and has a low risk of side effects.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Masseter Muscle Thickness in Relation to Facial Form in Angle's Normal Occlusion and Malocclusions: An Observational Study

Background

Various clinical studies performed in adults have shown the relationship between craniofacial morphology and masticatory muscle function. However, the growth of the masticatory muscle has not received such attention, when compared with the volume of studies on the skeletal growth of face. With this background and considering the widespread use of ultrasonography (USG), the following study was undertaken to provide some insights into the relationship between muscle and bone and facial morphology.

Methods

This was a prospective, observational study conducted over a period of three years from 2012 to 2015 to assess the correlation between the thickness of the masseter muscle in Angle's normal occlusion and the various malocclusions of the dental arch as well as the facial form. Patients with a full complement set of teeth, normal tooth morphology, Angle's normal occlusion, Angle's class I-III malocclusion, those with a history of third molar extraction, and impaction were included in the study. Those with a history of any prior orthodontic treatment, restorations, or any missing teeth (except the third molar) were exempted from the study. The greater thickness of masseter muscle in relaxed and clenched state was recorded on USG. Facial morphology was determined with the aid of facial photographs.

Results

The study was conducted on 140 patients. The class I normal occlusion group had the thickest masseter muscle, while the class III malocclusion group had the thinnest masseter muscle. Facial parameters showed highly significant gender-wise differences in class I normal occlusion, class I malocclusion, and class II division II malocclusion. There was a significant negative co-relation between the thickness of masseter muscle and facial forms in all the categories of Angle's classification as indicated by a negative regression coefficient B (P < 0.05).

Conclusion

The masseter muscle thickness correlated directly with male gender and normal occlusion, and inversely with the degree of malocclusion and facial form.

Effect of rehabilitation by using the shortened dental arch concept on the thickness of the masseter muscle and occlusal force: A pilot study

STATEMENT OF PROBLEM

Knowledge of the effect of a shortened dental arch on masseter muscle thickness and occlusal force is sparse but could help clinicians understand how a shortened dental arch might affect the stomatognathic system.

PURPOSE

The purpose of this pilot clinical study was to evaluate and compare the masseter muscle thickness and occlusal force of participants rehabilitated by using a shortened dental arch with matched completely dentate individuals.

MATERIAL AND METHODS

Twelve partially edentulous participants with a minimum of 1 posterior occluding pair on each side of the arch were enrolled in the study. The mandibular arch of these participants was rehabilitated by using a single posterior mandibular implant crown (group S). The maxillary arch of all participants in group S was intact. Masseter muscle thickness (cm) and occlusal force (N) were recorded before (T1) and 6 months after implant rehabilitation (T2) for each participant. Twelve participants were selected as controls (group C). They were matched for age, sex, height, and weight with group S and evaluated for masseter muscle thickness and occlusal force. Masseter muscle thickness was evaluated by using ultrasonography during the rest position and maximum volumetric clenching. Occlusal force was measured with an occlusal force measuring appliance. All recordings were done for the left and right sides of the arch. Descriptive analysis was followed by comparison between groups and within group S by using the paired t test (α=.05).

RESULTS

Higher masseter muscle thickness and higher occlusal force were observed in group C than in group S before and after rehabilitation. An increase in masseter muscle thickness in the rest position and in maximum volumetric clenching was observed within group S after rehabilitation. Before rehabilitation, a difference in the masseter muscle thickness between group S and group C was statistically significant for the left side at the rest position (P=.017) and during maximum volumetric clenching (P=.016). After rehabilitation, the difference between group S and group C was not statistically significant for masseter muscle thickness at the rest position (P=.890 for right side and P=.555 for left side) and during maximum volumetric clenching (P=.109 for right side and P=.755 for left side). The difference in occlusal force between group S and group C was statistically significant for the right side and left side (P<.001) before rehabilitation and statistically not significant after rehabilitation (P=.161 for the right side and P=.134 for the left side).

CONCLUSIONS

Rehabilitation following the concept of a shortened dental arch increased masseter muscle thickness and occlusal force in partially edentulous individuals, making the masseter muscle thickness and occlusal force comparable with those of a completely dentate arch.

Ultrasonography for Eating and Swallowing Assessment: A Narrative Review of Integrated Insights for Noninvasive Clinical Practice

Dysphagia is a syndrome of abnormal eating function resulting from a variety of causative diseases, and is associated with malnutrition. To date, the swallowing function has been difficult to examine without the use of invasive and expensive methods, such as the videofluorographic swallowing study or fiberoptic endoscopic evaluation of swallowing. In recent years, progress has been made in the clinical application of ultrasound equipment for the evaluation of body compositions near the body surface, including the assessment of nutritional status. Ultrasound examination is a noninvasive procedure and relatively inexpensive, and the equipment required is highly portable thanks to innovations such as wireless probes and tablet monitoring devices. The process of using ultrasound to visualize the geniohyoid muscle, digastric muscle, mylohyoid muscle, hyoid bone, tongue, masseter muscle, genioglossus muscle, orbicularis oris muscle, temporalis muscle, pharynx, esophagus, and larynx, and the methods used for evaluating these structures, are provided in this study in detail. This study also aims to propose a protocol for the assessment of swallowing-related muscles that can be applied in real-world clinical practice for the diagnosis of sarcopenic dysphagia, which can occur in elderly patients with sarcopenia, and has received much attention in recent years.

Long-term evaluation of masseter muscle activity, dimensions, and elasticity after orthognathic surgery in skeletal class III patients

OBJECTIVE

To evaluate changes in the masseter muscle after orthognathic surgery using electromyography (EMG), ultrasonography (US), and ultrasound elastography (USE) in individuals with skeletal class III anomaly over long-term follow-up and compare with a control group.

MATERIALS AND METHODS

The study group included 29 patients with class III dentofacial deformities scheduled to undergo orthodontic treatment and orthognathic surgery. The control group included 20 individuals with dental class I occlusion. Assessment of the masseter muscles using EMG, US, and USE was performed before orthognathic surgery (T1) and at postoperative 3 months (T2) and 1 year (T3) in the study group, and at a single time point in the control group. All assessments were performed at rest and during maximum clenching. Masseter muscle activity, dimension, and hardness were analyzed.

RESULTS

Electromyographic activity of the masseter muscle during maximum clenching was increased at postoperative 1 year but did not reach control group values. On ultrasonography, the masseter muscle showed minimal changes in dimension at postoperative 1 year compared to preoperative values and remained below control group values. The postoperative increase in masseter muscle hardness at rest and during maximum clenching persisted at postoperative 1 year.

CONCLUSION

The results of this study suggest that after orthognathic surgery, additional interventions and much longer follow-up are needed to ensure better muscle adaptation to the new occlusion and skeletal morphology.

CLINICAL RELEVANCE

All assessment methods are useful for comprehensively evaluating changes in the masticatory muscles after orthognathic surgery.

Probable bruxism effects on masseter muscle thickness in children: ultrasonographic evaluation

OBJECTIVE

To compare the masseter muscle thickness (MMT) of patients with probable sleep/awake bruxism and controls without bruxism in mixed dentition as measured with ultrasonography (USG), and to calculate the correlation of MMT with body mass index (BMI).

STUDY DESIGN

The diagnosis of probable bruxism was established based on the parents' reports of the children's behavior, habits, and discomfort, and the presence of clinical signs and symptoms such as attrition-type wear on the teeth and the presence of discomfort, fatigue, and/or pain in the jaw muscles on palpation during clinical examination. The bruxist study group and the control group each included 28 children. MMT was measured separately in relaxed and contracted positions in both groups using USG. The height and weight of the patients were recorded in order to calculate BMI. Statistical analysis was performed with significance established at P < .05.

RESULTS

MMT was found to be significantly larger in the study patients than in controls on the right and left sides in the relaxed and contracted positions (P < .001). No statistically significant correlation was found between MMT and BMI (P ≥ .134).

CONCLUSIONS

MMT as measured with USG can be a beneficial approach in diagnosing bruxism in children. The lack of correlation between MMT and BMI indicates that BMI would not be helpful in diagnosing bruxism.

The Evaluation of the Relationship between Changes in Masseter Muscle Thickness and Tooth Clenching Habits of Bruxism Patients Treated with Botulinum Toxin A

Background

Bruxism is defined as recurrent masticatory muscle activity. Although there is not an agreed treatment method for bruxism, the application of botulinum toxin A (BT-A) has become a reliable lately. This study aimed to evaluate the correlation between the changes in masseter muscle thickness and clenching habits in bruxism patients treated with BT-A.

Methods

Twenty-five patients, 23 females and 2 males, diagnosed with possible sleep bruxism were included in the study. The Fonseca Anamnestic Index was applied to the patients to determine their clenching habits and depression levels both before the treatment, and 6 months after it. The masseter muscle thickness was measured using ultrasonography before the treatment and 3 months and 6 months after the treatment. All the patients were injected with a total of 50 U of BT-A, 25 U to each masseter.

Results

A statistically significant decrease in masseter muscle thickness was observed in the ultrasonography 3 and 6 months after the BT-A treatment. There was a statistically significant decrease in the Fonseca scores, in which the teeth clenching habits of the patients were evaluated 6 months after the treatment. Although there was a decrease in the depression levels of the patients 6 months after the treatment, this difference was not statistically significant.

Conclusion

When the results of this study were evaluated, it was seen that the BT-A injections are an effective, safe, and side effect-free method in the treatment of bruxism and masseter hypertrophy.

The relationship of masseter muscle thickness with face morphology and parafunctional habits: an ultrasound study

OBJECTIVE

The aim of this study was to determine the normal range of masseter muscle thickness by ultrasonographic measurement in individuals over 15 years of age, and to evaluate its relationship with age, gender, facial morphology, body mass index and parafunctional habits.

METHODS

The study was conducted on 115 volunteers whose lateral cephalometric radiography was performed within the indication in Gazi University Faculty of Dentistry, Department of Dentomaxillofacial Radiology. The participants in the study were asked questions about their parafunctional habits, age, height and weight. Individuals were grouped as hypodivergent (n = 28), normdivergent (n = 55), or hyperdivergent (n = 32) according to vertical face morphology by making measurements on lateral cephalometric films. Right and left masseter muscle thicknesses of individuals were measured by ultrasonography while at rest and in contraction.

RESULTS

The mean value of masseter muscle thickness was found to be 13.57 ± 2.57 mm. The rest and contracted muscle thicknesses were significantly higher in males than in females for the right and left masseter muscles (p < 0.05). When the masseter muscle was at rest and contracted, its thickness was higher in individuals with hypodivergent facial morphology, than in the other groups. No statistically significant difference was found in terms of masseter muscle thickness between individuals having parafunctional habits and those who did not have parafunctional habits (p > 0.05).

CONCLUSION

Although masseter muscle thickness varied according to vertical facial morphology, this was not the case for parafunctional habits.

Association of Craniofacial Patterns with the Curve of Spee and the Time Required for Orthodontic Levelling

The curve of Spee (CoS) is an important parameter for an individualized treatment plan. The available information regarding a potential association of the depth of the curve of Spee with various skeletal craniofacial characteristics is conflicting and it is also unknown whether certain craniofacial parameters affect the duration of the levelling phase of orthodontic treatment. A prospective sample of 32 patients with mild to moderate crowding that underwent orthodontic treatment with full fixed appliances was used to study these topics. The craniofacial characteristics were captured on pre-treatment lateral cephalometric radiographs and measurements of the CoS were performed on the initial 3D digital dental models using the Viewbox 4 software. Non-parametric statistics and Spearman’s correlations were applied. Weak negative correlations were detected between the CoS depth and the SNA and SNB angles. There was no other association between the CoS and craniofacial parameters, including various anteroposterior measurements. Furthermore, there was no significant association of any craniofacial parameter with the duration of the levelling. Contrary to certain clinical beliefs, it can be argued that the craniofacial characteristics are not associated with the CoS and the time required for its levelling in subjects with moderate pre-treatment CoS depth.

Correlation of radiomorphometric indices of the mandible and mandibular angle fractures

This study assessed the correlation of radiomorphometric indices of the mandible and mandibular angle fractures (MAFs) in an Iranian population. This retrospective study was conducted on 3D computed tomography (CT) scans of 118 patients between 18 to 60 years. The images were divided into two groups with MAFs and other types of mandibular fractures (non-MAF). The gonial angle, ramus height, condylar neck width, minimum ramus width, and mandibular length were all measured using MARCO PACS software. Age, gender, and presence and eruption status of third molar at the fracture side were all recorded. The correlation between these parameters and MAF was analyzed using R software (alpha = 0.05). Of all patients, 41 samples had MAF. The two groups were not significantly different regarding the mean age and gender (P > 0.05). The mean size of gonial angle and ramus height in the MAF group were significantly larger, and smaller than the corresponding values in the non-MAF group, respectively (P < 0.001). The median minimum ramus width in the MAF group was significantly smaller than that in the non-MAF group (P = 0.001). Patients with a large gonial angle had 6.6 times higher odds of MAF compared with other fracture types (P = 0.046). Condylar neck width, mandibular length, and erupted third molars had no significant correlation with type of fracture. Presence of impacted third molar increased the odds of MAF by 5.55 times.

Patients with a large gonial angle, short ramus height, minimum ramus width, and impacted third molar are more susceptible to MAF. Surgeons can use these indices to predict the risk of MAF in trauma patients with such facial characteristics, and make a diagnosis by radiographic modalities.

Substantial Improvements in Facial Morphology through Surgical-Orthodontic Treatment: A Case Report and Literature Review

Background and Objectives: The long face type is associated with excessive vertical facial growth and most often with anterior open bite. In many cases of anterior open bite of high severity associated with bimaxillary dento-alveolar protrusion, lips are unable to form an adequate seal at rest. This leads to many issues, including facial dysmorphism. The aim of this study was to describe the case of a 15 year old girl who addressed the orthodontist in November 2015, having complaints related to the skeletal and dental open bite. Case Description: A 15.7 year old patient required a consultation with the orthodontic service for impaired dento-facial aesthetics at rest, smile and speech due to an exaggerated superior protrusion of the upper frontal teeth, labial incompetence with excessive gingival exposure at rest and smile associated with upper and lower anterior teeth crowding. The orthodontic diagnostic consisted of skeletal open bite with a hyperleptoprosop morphological facial type, high degree of hyperdivergence, bimaxillary dento-alveolar protrusion, 7 mm skeletal open-bite, 3 mm vertical inocclusion of the anterior teeth, skeletal class II relationships, bilateral half cusp class II molar and canine relationships, labial incompetence, highly increased interlabial gap, facial asymmetry, excessive gingival exposure of 7 mm at smiling and bimaxillary anterior crowding. Because the patient initially refused orthognathic surgery, prior to starting the orthodontic treatment, the patient was recommended to receive a bilateral extraction of the first upper premolars. Key objectives of pre-surgical orthodontic treatment were to achieve a retroclined position of the upper incisors under their normal inclination for the planned upward maxillary rotation, to maintain slightly lower incisor proclination. The orthognathic surgery consisted of Le Fort I impaction osteotomy with 8 mm anterior impactation, bilateral sagittal split osteotomy, and mandibular repositioning using occlusal splint. Conclusions: At the end of the orthodontic-surgical treatment, the patient presented significant improvement in dento-facial aesthetics, and optimal skeletal, muscular and dental balance.

Masseter muscle thickness and vertical cephalometric characteristics in children with Class II malocclusion

Background

Masseter muscle thickness and its relationship with vertical craniofacial morphology have been extensively studied in adults, but data on children are lacking.

Objective

To examine the association between masseter muscle thickness and vertical cephalometric parameters in a group of Class II malocclusion growing children.

Methods

The current study design was retrospective and cross‐sectional, looking at a sample of 211 growing children with Class II malocclusion between the ages of 6 and 15 derived from two centers. Ultrasonographic masseter muscle thickness measurements and vertical cephalometric variables, including the gonial angle, were evaluated before any orthodontic treatment had been carried out. Multiple linear regression analysis was used to examine the association between masseter muscle thickness and vertical cephalometric measurements, including age and patient origin as independent variables in the analysis.

Results

In the present sample, masseter muscle thickness was found to be independent of sex, but correlated with age, with older children presenting thicker masseter muscles. In the total patient sample, using multiple regression analyses, children with thicker masseter muscles had significantly smaller intermaxillary and gonial angles. No other cephalometric vertical characteristics showed associations with masseter muscle thickness.

Conclusion

In growing children with Class II malocclusion, those with thicker masseter muscles are more likely to display smaller intermaxillary and gonial angles respectively.

Comparative assessment of various cephalometric facial planes with intercanine width in orthodontic patients

OBJECTIVE:

The study was conducted to evaluate the relationship of various cephalometric skeletal patterns in the vertical and anteroposterior planes with intercanine width in untreated orthodontic patients.

METHOD AND MATERIAL:

This study included dental cast and cephalometric radiographs of 100 patients (69 females and 31 males) of the age range 13 to 33 years. Skeletal parameters including SNA, SNB, SNMP angles were found from lateral cephalometric radiographs. Intercanine widths including upper intercanine widths (UICW) and lower intercanine widths (LICW) were measured by a digital caliper.

RESULTS:

The correlation of intercanine width with SNA, SNB, and SNMP angles was analyzed by applying Pearson correlation coefficient. According to statistical analysis, the only insignificant correlation was analyzed between UICW with SNB and LICW with SN-MP.

CONCLUSIONS:

The overall result showed statistically significant relationship of various cephalometric skeletal patterns in the sagittal and vertical planes with intercanine width.

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.

Assessments of Muscle Thickness and Tonicity of the Masseter and Sternocleidomastoid Muscles and Maximum Mouth Opening in Patients with Temporomandibular Disorder

The purpose of this study was to compare the muscle thickness and tone of the masseter and sternocleidomastoid (SCM) muscles and maximum mouth opening (MMO) in subjects with and without temporomandibular disorders (TMD), and perform a correlation comparison on the results of the TMD group. Sixty patients were allocated to the TMD group (n = 30) or the non-TMD group (n = 30). Ultrasound imaging, myotonometer, and vernier calipers were used to determine the related changes in muscle thickness and muscle tone in masseter and SCM, and MMO, respectively. The TMD group revealed a significant decrease than the non-TMD group in the muscle thickness of masseter and SCM, respectively (p < 0.001), with a significant increase in frequency (p < 0.001) and stiffness (p < 0.001) in the masseter muscle tone, with a significant increase in frequency (p < 0.001) and stiffness (p = 0.005) in the SCM muscle tone, a significant decrease in the MMO (p < 0.001). There was a moderate negative correlation between the relaxed state of masseter muscle thickness and stiffness of SCM muscle tone (r = −0.40, p = 0.002), and a moderate negative correlation between the relaxed state of SCM muscle thickness and frequency of SCM muscle tone (r = −0.42, p = 0.001). There was a moderate negative correlation between the clenching state of SCM muscle thickness and the frequency of SCM muscle tone (r = −0.47, p < 0.001). In addition, a moderate negative correlation between MMO and frequency of SCM muscle tone (r = −0.44, p < 0.001). The muscle thickness was decreased, and the muscle tone was increased in the masseter and SCM muscle, respectively. Additionally, MMO was decreased in patients with TMD compared with non-TMD.

Miniaturized electromechanical devices for the characterization of the biomechanics of deep tissue

Evaluating the biomechanics of soft tissues at depths well below their surface, and at high precision and in real time, would open up diagnostic opportunities. Here, we report the development and application of miniaturized electromagnetic devices, each integrating a vibratory actuator and a soft strain-sensing sheet, for dynamically measuring the Young's modulus of skin and of other soft tissues at depths of approximately 1-8 mm, depending on the particular design of the sensor. We experimentally and computationally established the operational principles of the devices and evaluated their performance with a range of synthetic and biological materials and with human skin in healthy volunteers. Arrays of devices can be used to spatially map elastic moduli and to profile the modulus depth-wise. As an example of practical medical utility, we show that the devices can be used to accurately locate lesions associated with psoriasis. Compact electronic devices for the rapid and precise mechanical characterization of living tissues could be used to monitor and diagnose a range of health disorders.

[Ultrasound structural assessment of masseter muscles in subjects with different types of craniofacial growth]

THE AIM OF THE STUDY

Was to assess the correlation of various maxillofacial structures in subjects with different types of craniofacial growth.

MATERIALS AND METHODS

The results of comparing the morphology of the masseter muscles (thickness, area, echostructure) in 30 volunteers aged from 18 to 25 years without malocclusions and different type of craniofacial growth were presented.

RESULTS

A significant correlation between the thickness of the masseter muscles and morphology of the facial skull was observed: the smallest thickness of masseter muscles was in subjects with vertical type of craniofacial growth, the largest - in patients with horizontal type of craniofacial growth. The study results improved ultrasound technique of masseter muscles assessment including methods for measuring the thickness, area and echostructure on ultrasound images.

CONCLUSION

The obtained results may be seen as reference points for assessment of the same structures in patients with malocclusions.

An Artificial Intelligence Hypothetical Approach for Masseter Muscle Segmentation on Ultrasonography in Patients With Bruxism

Aim:

The present study is aimed to assess the segmentation success of an artificial intelligence (AI) system based on the deep convolutional neural network (D-CNN) method for the segmentation of masseter muscles on ultrasonography (USG) images.

Materials and Methods:

This retrospective study was carried out by using the radiology archive of the Department of Oral and Maxillofacial Radiology of the Faculty of Dentistry in Ankara University. A total of 195 anonymized USG images were used in this retrospective study. The deep learning process was performed using U-net, Pyramid Scene Parsing Network (PSPNet), and Fuzzy Petri Net (FPN) architectures. Muscle thickness was assessed using USG by manual segmentation and measurements using USG’s software. The neural network model (CranioCatch, Eskisehir-Turkey) was then used to determine the muscles, following automatic measurements of the muscles. Accuracy, ROC area under the curve (AUC), and Precision-Recall Curves (PRC) AUC were calculated in the test dataset and compare a human observer and the AI model. Manual segmentation and measurements were compared statistically with AI ( P < .05). The Mann–Whitney U test was used to analyze whether there is a statistically significant difference between the predicted values and the actual values.

Results:

The AI models detected and segmented all test muscle data for FPN and U-net, while only two cases of muscles were not detected by PSPNet (false negatives). Accuracies of FPN, PSPNet, and U-net were estimated as 0.985, 0.947, and 0.969, respectively. Receiver operating characteristic scores of FPN, PSPNet, and U-net were estimated as 0.977, 0.934, and 0.969, respectively. The D-CNN measurements of the muscles were similar to manual measurements. There was no significant difference between the two measurement methods in three groups ( P > .05).

Conclusion:

The proposed AI system approach for the analysis of USG images seems to be promising for automatic masseter muscle segmentation and measurement of thickness. This method can help surgeons, radiologists, and other professionals such as physical therapists in evaluating the time correctly and saving time for diagnosis.

Electromyographic, Ultrasonographic, and Ultrasound Elastographic Evaluation of the Masseter Muscle in Class III Patients Before and After Orthognathic Surgery

PURPOSE

The aim of this study was to examine changes in the electromyographic activity, thickness, width, and hardness of the masseter muscle from before to after orthognathic surgery.

MATERIAL AND METHODS

The study included 15 patients with Class III dentofacial deformities who were treated with combined orthodontic and orthognathic surgery. Fifteen individuals with normal occlusion and no signs or symptoms of temporomandibular joint dysfunction were used as controls. All records were obtained bilaterally in the study group before surgery (T1), at 3 months after surgery (T2), and in the control group (CG) while at rest and in maximum voluntary contraction (MVC).

RESULTS

There was no difference in resting masseter muscle activity between T1, T2, and CG. Resting thickness and width of the masseter muscle did not differ significantly between T1 and T2. MVC masseter muscle activity and thickness increased significantly and width decreased significantly from T1 to T2 but did not reach CG values. Muscle hardness increased from T1 to T2.

CONCLUSIONS

The authors' findings indicate that despite improved muscle activity and dimensions, postoperative 3 months is still early period for adaptation of the masseter muscles to the new occlusion and skeletal morphology.

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.

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.

Surgical benefit of mandibular morphometric analysis: A new tool to standardize mandibular reconstruction

PURPOSE

The gold-standard for reconstruction of large mandibular defects is the use of free flaps of vascularized autologous bone with the fibula as the preferred donor site. The use of "custom cutting guides" for this indication is becoming increasingly prevalent. But cost of the procedure averages around 2,500 dollars per patient excluding treatment and entails selection criteria. We think it is possible to standardize mandibular reconstructions from an anatomical mean. The objective of this study was to perform a mandibular morphometric analysis in order to obtain a set of "mean" measurements, which can be used by all surgeons interested in mandibular reconstruction.

METHODS

We performed a morphometric analysis consisting of three-dimensional mandibular reconstructions of 30 men and 30 women. Several reference points were set and defined to evaluate specific lengths and angles of interest. We conducted an intra and inter-sexual descriptive analysis of measurements obtained.

RESULTS

We did not identify any major intra-sexual differences within each group. The gonial angle is more open in women and the measurements characterizing the basilar contour are more prominent in men. We did not identify any differences in alveolar region parameters.

CONCLUSION

The results of this study constitute a morphological tool for surgeons, from bone graft to free flap. These results also confirm us that the use of «custom cutting guides» for mandibular reconstruction may be excessive. It is pertinent to examine the value of "custom made" mandibular reconstructions since the differences observed are of the order of millimeters.

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

OBJECTIVES

: The 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 METHODS

Multidetector 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.

RESULTS

The 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.

CONCLUSION

The 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.

Automatic Tracking of Muscle Cross-Sectional Area Using Convolutional Neural Networks with Ultrasound

OBJECTIVES

The purpose of this study was to develop an automatic tracking method for the muscle cross-sectional area (CSA) on ultrasound (US) images using a convolutional neural network (CNN). The performance of the proposed method was evaluated and compared with that of the state-of-the art muscle segmentation method.

METHODS

A real-time US image sequence was obtained from the rectus femoris muscle during voluntary contraction. A CNN was built to segment the rectus femoris muscle and calculate the CSA in each US frame. This network consisted of 2 stages: feature extraction and score map reconstruction. The training of the network was divided into 3 steps with output score map resolutions of one-fourth, one-half, and all of the original image. We evaluated the segmentation performance of our method with 5-fold cross-validation. The mean precision, recall, and dice similarity score were calculated.

RESULTS

The mean precision, recall, and Dice's coefficient (DSC) ± SD were 0.936 ± 0.029, 0.882 ± 0.045, and 0.907 ± 0.023, respectively. Compared with the state-of-the-art muscle segmentation method (constrained mutual-information-based free-form deformation), the proposed method using CNN showed high performance.

CONCLUSIONS

The automated method proposed in this study provides an accurate and efficient approach to the estimation of the muscle CSA during muscle contraction.

The ancient sarcomeric myosins found in specialized muscles

Striated muscles express an array of sarcomeric myosin motors that are tuned to accomplish specific tasks. Each myosin isoform found in muscle fibers confers unique contractile properties to the fiber in order to meet the demands of the muscle. The sarcomeric myosin heavy chain (MYH) genes expressed in the major cardiac and skeletal muscles have been studied for decades. However, three ancient myosins, MYH7b, MYH15, and MYH16, remained uncharacterized due to their unique expression patterns in common mammalian model organisms and due to their relatively recent discovery in these genomes. This article reviews the literature surrounding these three ancient sarcomeric myosins and the specialized muscles in which they are expressed. Further study of these ancient myosins and how they contribute to the functions of the specialized muscles may provide novel insight into the history of striated muscle evolution.

Ultrasonography of the internal architecture of the superficial part of the masseter muscle in vivo

It is unclear whether the deep inferior tendon (DIT) is equally present in vivo, and little anatomical information is available regarding the existence and morphology of the DIT in healthy young subjects. The aim of this study was to characterize the DIT of the masseter muscle in healthy young subjects using ultrasonography and to compare the morphology of this tendon with previously reported data for healthy young subjects in order to provide the most-effective injection methods for botulinum neurotoxin treatments of masseteric hypertrophy. This study investigated two fresh cadavers and 30 healthy subjects. Ultrasonography scanning in both longitudinal and transverse directions was applied to the masseter muscle. The DIT within the superficial part of the masseter was observed in both the fresh cadavers and the living subjects. The posterior region of the masseter muscle was compartmentalized (entirely covered) by the DIT in 26.7% of the specimens. The superficial part of the masseter muscle was divided by the DIT transversely and longitudinally into the superficial and deep muscle bellies in 35% and 38.3% of the specimens, respectively. The present findings suggest applying a DIT-based injection technique under guidance by ultrasonography prior to treating masseteric hypertrophy. Clin. Anat. 32:446-452, 2019. © 2019 Wiley Periodicals, Inc.

Growing patients with Duchenne muscular dystrophy: longitudinal changes in their dentofacial morphology and orofacial functional capacities

Aim

The aim of this study was to describe the longitudinal changes in facial morphology, dental arch alterations and oral functional capacities that occur in growing patients with Duchenne muscular dystrophy (DMD) in order to identify the effects of the progression of the disease.

Subjects and Methods

Twelve DMD patients (6.5-17.5 years of age) and 12 matched controls were screened on two different occasions (T1 and T2), 2 years apart. Dental casts, lateral cephalometric radiographs, maximal posterior bite force and labial force were measured to determine changes in their functional capacities and dentofacial morphology. Furthermore, the thickness and echogenicity of the masseter muscle were measured during clenching.

Statistical evaluation

Unpaired t-tests were performed to evaluate the differences between the DMD patients and their healthy matched controls; paired t-tests were used to assess the changes that occurred within each group between T1 and T2.

Results

Between T1 and T2 the following changes were observed: widening of the lower dental arch for the DMD patients of 2.6mm (±0.9mm) compared to a slight reduction of -0.1mm (±0.8mm) for the control group (P = 0.001). We found a statistically significant reduction of the sagittal skeletal intermaxillary relationship (ANB-angle) of 2.0° (±2.0°) in the DMD group (P = 0.012). In T1 and T2, the maximal posterior bite force and the labial force were lower for the DMD patients compared to the control group (P = 0.001), who showed an increase during this period.

Conclusion

The results indicate that DMD influences the facial morphology, dental arch dimensions and oral functional capacities. The longitudinal perspective of this study revealed that the worsening of most of the measured parameters is associated with the progression of the disease. Besides the expected deterioration of the functional measurements, we found in all patients, a marked transverse increase of the posterior part of the dental arches, more in the lower than in the upper, resulting in posterior crossbites, as well as a tendency towards a skeletal Class III relationship.

Effect of implant-supported mandibular overdentures versus reline on masticatory performance and salivary flow rates in very old adults-A randomized clinical trial

PURPOSE

To compare the masticatory efficiency (ME), maximum voluntary bite force (MBF), masseter muscle thickness (MMT), and salivary flow rates (SFR) in completely edentulous dependent elders treated either with a conversion of their existing mandibular complete removable dental prostheses (CRDPs) into a two-implant overdenture (IOD) or a conventional reline of the CRDP.

MATERIAL AND METHODS

Participants were randomly allocated into intervention (IG) and control (CG) groups. The IG received two implants in the mandibular canine regions, and their CRDPs were transformed into IODs. The CG received a conventional reline of their mandibular CRDPs. Outcomes were recorded at each recall visit (baseline, immediately, 3 months, 12 months after intervention, and subsequently on an annual basis). Statistical analyses used mixed linear regression models (level of significance: p < 0.05).

RESULTS

The IG comprised 16 participants (age = 85.0 ± 6.2 years), while the CG comprised 16 (age = 84.8 ± 5.4 years), with a mean follow-up of 2.7 ± 2.2 years (range: 3 months-7 years). A significant increase of MBF in the IG was observed with an overall gain of 80 N (p < 0.001) compared with the reline group. There were no significant long-term changes in SFR, MMT, or ME within/between groups.

CONCLUSION

Since dependent elders with mandibular IODs present a significant gain in MBF, but no relative increase in SFR, MMT, and ME, it seems that this increased capacity of MBF is not exploited by the elders during their habitual chewing.

Ultrasonographic evaluation of masseter muscle thickness in patients with disk displacement with reduction

OBJECTIVES

This study was performed to ultrasonographically assess the masseter muscle thicknesses of individuals with disk displacement with reduction.

METHODS

The thickness of the masseter muscle in 100 patients (28 male, 72 female; average age 34 years) who presented with one-sided temporomandibular joint pain and a clicking sound and were diagnosed with disk displacement with reduction was measured in relaxation and at maximum contraction using ultrasonography.

RESULTS

In the contracted position, the difference in the masseter muscle thickness between the healthy side and the side with disk displacement with reduction was statistically significant (p < 0.05). However, no statistically significant difference was found between the two sides in the relaxed position.

CONCLUSIONS

Obvious ultrasonographic changes of the masseter muscle were found in patients with temporomandibular disk displacement with reduction, and these changes might be related to unilateral chewing. Individuals with anterior disc displacement probably chew unilaterally because of pain and clicking.

Functional and molecular outcomes of the human masticatory muscles

The masticatory muscles achieve a broad range of different activities such as chewing, sucking, swallowing, and speech. In order to accomplish these duties, masticatory muscles have a unique and heterogeneous structure and fiber composition, enabling them to produce their strength and contraction speed largely dependent on their motor units and myosin proteins that can change in response to genetic and environmental factors. Human masticatory muscles express unique myosin isoforms, including a combination of thick fibers, expressing myosin light chains (MyLC) and myosin class I and II heavy chains (MyHC) -IIA, -IIX, α-cardiac, embryonic and neonatal and thin fibers, respectively. In this review, we discuss the current knowledge regarding the importance of fiber-type diversity in masticatory muscles versus supra- and infrahyoid muscles, and versus limb and trunk muscles. We also highlight new information regarding the adaptive response and specific genetic variations of muscle fibers on the functional significance of the masticatory muscles, which influences craniofacial characteristics, malocclusions, or asymmetry. These findings may offer future possibilities for the prevention of craniofacial growth disturbances.

Relationship between masseter muscle thickness and maxillofacial morphology in pre-orthodontic treatment patients

This study investigated the relationship between masseter muscle thickness and cephalometric facial parameters in pre-orthodontic treatment patients. Participants were grouped according to their vertical facial patterns into low, normal, and high angle facial patterns using standardised lateral cephalometric radiograph. Associations between the masseter muscle thickness (measured using ultrasonography) and different vertical facial patterns were analysed. Masseter muscle thickness in low angle subjects were significantly higher than the normal and high angle cases during both relaxation and contraction phases (P<0.001). Masseter muscle thickness correlated positively with Jarabak ratio and ramus thickness (R1/R2) during both phases, and negatively with LAFH, FMA, MMPA and gonial angle.

Asymmetric Protrusion of the Midface in Young Adults

PURPOSE

This study evaluated midfacial asymmetry using an alternative method that involved comparing bilateral patterns of the zygomaticomaxillary prominence in a young adult population.

MATERIALS AND METHODS

Three-dimensional reconstructed images based on computed tomography scans of 100 Koreans (mean age, 24.7 years) were evaluated with reference to lines spaced at 30° intervals and radiating from the center of an interporion line in a superior view. The surface inclination of the zygomaticomaxillary region was quantified on the same reference lines using a 3-dimensional ruler.

RESULTS

The 30°-interval line (at the level of the zygomaticotemporal suture) was longer on the left side than the right side in both males and females, whereas the left 60°-interval line (at the level of the zygomaticofrontal suture) was longer in females. Comparing the surface protrusion revealed that the zygomaticomaxillary region was more prognathic and inflated on the left side.

CONCLUSION

Functional deviations are considered to be causes of asymmetric craniofacial growth. Postnatal growth allometry across the circummaxillary sutures as elucidated by this study could be useful information in craniofacial surgery.

Assessment of Masseter Muscle Appearance and Thickness in Edentulous and Dentate Patients by Ultrasonography

Objectives:

The purpose of the present study was to examine ultrasonographic appearances of Masseter Muscle (MM) in dentate and edentulous patients without Temporomandibular Disorder (TMD).

Materials and Methods:

The thickness of the MM in 25 dentate (mean age: 30,68 ± 10,49) and 24 edentulous (mean age: 61,46 ± 9,71) patients, who visited routine dental examination, was measured at rest and at maximum contraction bilaterally. Examinations were performed using an Aloka Prosound α6 (Hitachi Aloka Medical Systems, Tokyo, Japan) equipped with an 8 MHz-wide bandwidth linear active matrix transducer (ranging from 1 to 15 MHz). The visibility and width of the internal echogenic bands of the MM were also assessed and the muscle appearance was classified as I of III types. Type I, characterized by the clear visibility of the fine bands; Type II, thickening echogenicity of the bands; Type III, disappearance or reduction in a number of the bands.

Results:

MM thickness at rest and contraction in the dentate group were significantly higher than the edentulous group (p <0.05). Type I was the most common echogenic type in both dentate (right:16 (64%), left; 15 (60%)) and edentulous patients (right; 22 (91.7%), left; 18 (75%)). In a dentate group, type II was significantly higher than the edentulous group in both the right and left sides (p <0.05; p <0.01, respectively). Age and gender seemed to have no significant effect on the echogenic type (p ˃0.05).

Conclusion:

There were significant differences in the thickness at rest and contraction between the dentate and edentulous groups. It was clarified that ultrasonographic features of the MM in dentate and edentulous patients were different.

The relationship between masseter muscle thickness measured by ultrasonography and facial profile in young Korean adults

Purpose

The purpose of this study was to evaluate the relationship between masseter muscle thickness, facial morphology, and mandibular morphology in Korean adults using ultrasonography.

Materials and Methods

Ultrasonography was used to measure the masseter muscle thickness bilaterally of 40 adults (20 males, 20 females) and was performed in the relaxed and contracted states. Facial photos and panoramic radiography were used for morphological analyses and evaluated for correlations with masseter muscle thickness. We also evaluated the correlations of age, body weight, stature, and body constitution with masseter muscle thickness.

Results

In the relaxing, the masseter was 9.8±1.3 mm in females and 11.3±1.2 mm in males. In the contracted state, it was 12.4±1.4 mm in females and 14.7±1.4 mm in males. Facial photography showed that bizygomatic facial width over facial height was correlated with masseter muscle thickness in both sexes in the relaxed state, and was statistically significantly correlated with masseter muscle thickness in males in the contracted state. In panoramic radiography, correlations were found between anterior angle length and posterior angle length and masseter muscle thickness in females, and between body length and posterior angle length, between anterior angle length and body length, between ramal length and body length, and between body length and condyle length in males.

Conclusion

Masseter muscle thickness was associated with facial and mandibular morphology in both sexes, and with age in males. Ultrasonography can be used effectively to measure masseter muscle thickness.

Human mandibular shape is associated with masticatory muscle force

Understanding how and to what extent forces applied to the mandible by the masticatory muscles influence its form, is of considerable importance from clinical, anthropological and evolutionary perspectives. This study investigates these questions. Head CT scans of 382 adults were utilized to measure masseter and temporalis muscle cross-sectional areas (CSA) as a surrogate for muscle force, and 17 mandibular anthropometric measurements. Sixty-two mandibles of young individuals (20–40 years) whose scans were without artefacts (e.g., due to tooth filling) were segmented and landmarked for geometric morphometric analysis. The association between shape and muscle CSA (controlled for size) was assessed using two-block partial least squares analysis. Correlations were computed between mandibular variables and muscle CSAs (all controlled for size). A significant association was found between mandibular shape and muscle CSAs, i.e. larger CSAs are associated with a wider more trapezoidal ramus, more massive coronoid, more rectangular body and a more curved basal arch. Linear measurements yielded low correlations with muscle CSAs. In conclusion, this study demonstrates an association between mandibular muscle force and mandibular shape, which is not as readily identified from linear measurements. Retrodiction of masticatory muscle force and so of mandibular loading is therefore best based on overall mandibular shape.

Masseter Muscle Thickness in Unilateral Partial Edentulism: An Ultrasonographic Study

Introduction:

Teeth and facial muscles play a very important role in occlusal equilibrium and function. Occlusal derangement, seen in unilateral partially edentulous individuals, has an effect on masseter muscle anatomy and function. The present study aims to evaluate masseter muscle thickness in unilateral partial edentulism.

Patients and Methods:

Institutional ethics committee approval was obtained before the commencement of the study. The study involved patients who routinely visited the Department of Oral Medicine and Radiology, Sri Ramachandra University. The study sample included 27 unilateral edentulous patients (Group E) and 30 controls (Group C). The masseter muscle thickness was evaluated using high-resolution ultrasound real-time scanner (linear transducer − 7.5–10 MHz) at both relaxed and contracted states.

Statistical Analysis Used:

The results were analyzed using paired t-test and independent t-test. Duration of edentulism and muscle thickness was assessed using Pearson's correlation coefficient.

Results:

The study patients’ age ranged between 25 and 48 years (mean – 36 years). The comparative evaluation of masseter muscle thickness between the dentulous and edentulous sides of experimental group was statistically significant (P < 0.05). However, no statistically significant difference in masseter muscle thickness was found between the dentulous side of control and experimental groups. The correlation between the duration of partial edentulism and muscle thickness was statistically insignificant.

Conclusion:

The study proves masseter atrophy in the edentulous side. However, since the difference is found to be marginal with the present sample, a greater sample is necessary to establish and prove the present findings as well as to correlate with the duration of edentulism. Further studies are aimed to assess the muscle morphology after prosthetic rehabilitation.

Treatment changes of hypo- and hyperdivergent Class II Herbst patients

OBJECTIVES

To determine the relative effects of Herbst appliance therapy in hypo- and hyperdivergent patients.

MATERIALS AND METHODS

The treated group included 45 growing Class II, division 1, patients treated with stainless steel crown Herbst appliances, followed by fixed edgewise appliances. The untreated control group consisted of 45 Class II, division 1, subjects, matched to the treated sample based on Angle classification, age, sex, and pretreatment mandibular plane angle (MPA). Subjects were categorized as hypo- or hyperdivergent based on their MPAs. Pre- and posttreatment cephalograms were traced and superimposed on cranial base and mandibular structures.

RESULTS

The primary effect of the Herbst in terms of maxillomandibular correction was in the maxilla. It significantly restricted maxillary growth, producing a "headgear effect." Mandibular treatment changes depended on divergence. Hyperdivergent patients experienced a deleterious backward true mandibular rotation with Herbst treatment. Hypodivergent patients, as well as untreated hypo- and hyperdivergent controls, underwent forward true mandibular rotation. However, hypodivergent chins did not advance any more than expected for untreated hypodivergent Class II patients.

CONCLUSIONS

Hypo- and hyperdivergent patients benefit from the Herbst's headgear effect. While the mandibular growth of hypodivergent patients overcomes the negative rotational effects, hyperdivergent patients undergo a deleterious backward mandibular rotation and increases in facial height.

Masseter muscle measurement performed by ultrasound: a systematic review

The aim of this study was to systematically review the existing scientific literature and evidence about (a) the validation of masseter muscle ultrasonography for accurate assessment of muscle thickness and (b) the reproducibility of masseter muscle thickness measures. An electronic literature search was conducted using determined keywords on specific databases. Preliminary search revealed 298 articles listed in Medline, Scopus and Web of Science. 60 duplicates were rejected, leaving 238 articles for review. After reading titles and abstracts, 31 articles remained. 23 articles were assessed for eligibility. These articles were categorized as follows: thickness, cross-section, volume and the length of the masseter muscle measured by ultrasonography. It is possible to verify the thickness of the masseter muscle in males and females in relaxation (10-15 and 9-13 mm, respectively) and contraction (14-19 and 12-15 mm, respectively). A similar tendency can also be evidenced in other measurements. Many studies evaluate masseter muscle dimensions to relate it to cephalometric analysis as such to evaluate morphological variations. It can be concluded that ultrasound is a reliable clinical tool for masseter muscle measurements, yet there is a need for standardization of methods and parameters to be recorded.

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.

Estimating effects of craniofacial morphology on gingival recession and clinical attachment loss

OBJECTIVES

Evidence on possible associations between facial morphology, attachment loss and gingival recession is lacking. We analysed whether the facial type, which can be described by the ratio of facial width and length (facial index), is related to periodontal loss of attachment, hypothesizing that a broad face might be associated with less gingival recession (GR) and less clinical attachment loss (CAL) than a long face.

MATERIALS AND METHODS

Data from the 11-year follow-up of the population-based Study of Health in Pomerania were used. Periodontal loss of attachment was assessed by GR and CAL. Linear regression models, adjusted for age and gender, were used to assess associations between specific landmark based distances extracted from magnetic resonance imaging head scans and clinically assessed GR or CAL (N = 556).

RESULTS

Analysing all teeth, a higher maximum cranial width was associated with a lower mean GR (B = -0.016, 95% CI: -0.030; -0.003, p = 0.02) and a lower mean CAL (B = -0.023, 95% CI: -0.040; -0.005, p = 0.01). Moreover, a long narrow face was significantly associated with increased mean GR and CAL (facial index, P for trend = 0.02 and p = 0.01, respectively). Observed associations were more pronounced for incisors and canines than for premolars and molars.

CONCLUSION

This study revealed craniofacial morphology, specifically the cranial width and the facial index, as a putative risk factor for periodontal loss of attachment.

Size and Orientation of Masticatory Muscles in Patients with Mandibular Laterognathism

Size measurements of jaw muscles reflect their force capabilities and correlate with facial morphology. Using MRI, we examined the size and orientation of jaw muscles in patients with mandibular laterognathism in comparison with a control group. We hypothesized that the muscles of the deviated side would be smaller than those of the non-deviated side, and that the muscles of both sides would be smaller than in controls. In patients, a comparison of deviated and non-deviated sides showed, in orientation, differences for masseter and medial pterygoid muscles, but, in size, differences only for the masseter muscle. Nevertheless, muscle sizes in patients were much smaller than in controls. Lateral displacement of the mandible can explain the orientation differences, but not the smaller muscle size, in patients. It is possible that the laterodeviation initiates an adaptive process in the entire jaw system, resulting in extensive atrophy of the jaw muscles.

The Influence of the Mandibular Gonial Angle on the Incidence of Mandibular Angle Fracture-A Radiomorphometric Study

PURPOSE

The aim of this radiomorphometric study was to analyze the association between the mandibular gonial angle and the risk of mandibular angle fracture.

MATERIALS AND METHODS

A retrospective analysis of medical records and radiographs of patients treated for mandibular fractures was performed. The exposure studied was the presence of a high gonial angle and the outcome was fracture of the mandibular angle. The mandibular gonial angle and mandibular height at the angle were measured using Facad software (Ilexis AB, Linköping, Sweden). Data obtained were analyzed using SPSS 16 (IBM Corp, Armonk, NY).

RESULTS

The study sample was comprised of 210 mandibular fractures (70 mandibular angle fractures and 140 non-angle fractures). The mean gonial angle in patients with mandibular angle fractures was 126.8 ± 7.9°, which was 4.5° larger than in patients with other mandibular fractures (P = .0001). Patients with a high gonial angle were 11.77 times more likely to sustain an angle fracture than those with normal or low gonial angles (adjusted odds ratio = 11.77; 95% confidence interval, 3.65-37.94; P < .001). There also was a statistically significant decrease in mandibular height at the angle in patients with a high gonial angle (P = .0001).

CONCLUSION

This study shows that people with a high gonial angle are at an increased risk for angle fracture and presents the related clinical implications.

Relação da espessura e da atividade elétrica do músculo masseter com a força de mordida: um estudo morfológico e eletrofisiológico

RESUMO: Objetivo: estudar a relação da espessura e da atividade elétrica do músculo masseter com a força de mordida. Métodos: participaram do estudo 17 adultos jovens (21,3 ( 1,4 anos), sendo 7 do gênero feminino e 10 do gênero masculino, saudáveis e clinicamente assintomáticos, quanto a disfunções temporomandibulares. Foi efetuada a medida da espessura do músculo masseter unilateralmente, durante o repouso e contração voluntária máxima. Também foi quantificada a força de mordida para cada lado com um transdutor de força posicionado na região do primeiro molar e simultaneamente avaliou-se atividade elétrica do masseter durante a mordida unilateral. A análise foi baseada na comparação das amostras, sendo utilizados o test t, Wilcoxon, Mann-Whitney e regressão linear multivariada. Resultado: a espessura do músculo masseter foi maior nos homens, tanto no repouso quanto em contração. Observou-se uma simetria entre os lados com os músculos em repouso e em contração. A frequência mediana do sinal eletromiográfico, para o músculo masseter em contração voluntária máxima, não apresentou diferença estatisticamente significante intra-indivíduos e na comparação entre os gêneros. Foi encontrada maior força de mordida nos indivíduos do gênero masculino. Não foi encontrado um modelo de regressão linear multivariada entre as variáveis estudadas. Conclusão: neste estudo, não foi possível encontrar um modelo linear com as variáveis estudadas.

Dystrophic changes in masticatory muscles related chewing problems and malocclusions in Duchenne muscular dystrophy

Dysphagia in Duchenne muscular dystrophy (DMD) worsens with age, with increasingly effortful mastication. The aims of this study were to describe mastication problems in consecutive stages in a group of patients with DMD and to determine related pathophysiological aspects of masticatory muscle structure, tongue thickness, bite force and dental characteristics. Data from 72 patients with DMD (4.3 to 28.0 years), divided into four clinical stages, were collected in a cross sectional study. Problems with mastication and the need for food adaptations, in combination with increased echogenicity of the masseter muscle, were already found in the early stages of the disease. A high percentage of open bites and cross bites were found, especially in the later stages. Tongue hypertrophy also increased over time. Increased dysfunction, reflected by increasingly abnormal echogenicity, of the masseter muscle and reduced occlusal contacts (anterior and posterior open bites) were mainly responsible for the hampered chewing. In all, this study shows the increasing involvement of various elements of the masticatory system in progressive Duchenne muscular dystrophy. To prevent choking and also nutritional deficiency, early detection of chewing problems by asking about feeding and mastication problems, as well as asking about food adaptations made, is essential and can lead to timely intervention.