Assessment of Masseter Volume and Postoperative Stability After Orthognathic Surgery in Patients With Skeletal Class III Malocclusion With Facial Asymmetry.

OBJECTIVE: This study aimed to evaluate the effect of orthognathic surgery on masseter volume in patients with skeletal Class III malocclusion with facial asymmetry and the effect of masseter volume on stability in orthognathic surgery. METHODS: This research studied 16 patients with Class III malocclusion with facial asymmetry who received combined orthodontic-orthognathic treatment and underwent craniofacial computed tomography (CT) before (T0), 2 weeks after (T1), and 6 months after (T2) surgery. Three-dimensional (3D) CT images were retrospectively analyzed, using 3D volume reconstruction to obtain the masseter volume and examine the impact of the masseter volume on stability in orthognathic surgery. RESULTS: A statistically significant difference ( P < 0.05) in the volume of the masseter was found up to 6 months after orthognathic surgery compared with the preoperative period, and the reduction in the masticatory muscle volume on the lengthened side is greater than on the shortened side ( P < 0.05). The volume of both masseters differed according to facial asymmetry, and the difference was significantly reduced after orthognathic surgery ( P < 0.05). During the period time (T1-T2), cephalometric maxillary marker points were not significantly different ( P > 0.05), and mandibular marker points were significantly anteriorly shifted ( P < 0.05). There was an association between the masseter volume and anterior shift of point B (R > 0.5, P < 0.05), the upward and anterior shifts of the gonion point differed between the lengthened and shortened sides ( P < 0.05). CONCLUSION: The size of the masseter becomes smaller 6 months after orthognathic surgery, and orthognathic surgery improves both bone and soft tissue symmetry. A larger sagittal relapse of mandibular setback occurred in patients with greater masseter volume. Considering these alterations may be helpful in planning orthognathic surgery.

MR sialographic assessment of the masseter muscle and the ductal kinking in patients with recurrent parotitis.

Dysfunction of the masseter muscle may cause pathological kinking of the parotid duct leading to parotitis; MR sialography is a non-invasive radiological examination that allows to evaluate dynamically the ductal system of the parotid glands. In the present study we aimed to assess the relationships between Stensen's duct and masseter muscle and their implications in the aetiopathogenesis of recurrent parotitis secondary to masseter muscle dysfunction. Forty-one patients with recurrent unilateral parotitis and nine with bilateral recurrent parotitis, all with a clinical suspicious of masseter muscle hypertrophy due to bruxism were enrolled. They underwent ultrasonography as a first line examination and then MR sialography and sialendoscopy. Different anatomical features were studied. Involved parotid glands had a wider duct compared to contralateral unaffected parotid glands of patients with recurrent parotitis (p = 0.00134); male subjects with parotitis had a longer duct compared to the salivary glands of healthy patients (p = 0.00943 for affected glands and p = 0.00629 for the contralateral). A concordance between the evidence of an acute duct angle during sialendoscopy and a wider duct in patients with parotitis was observed although not statistically significant. These initial findings suggest that the masticatory muscle dysfunction related to bruxism seems to condition alteration of parotid duct course and anatomy thus favouring the occurrence of recurrent parotitis. A specific diagnostic iter based on clinical evaluation, dynamic ultrasonography and MR sialography, is therefore, mandatory to confirm the relationship between masseter muscle anatomy and parotid duct anomalies; this is the premise for an adequate therapeutic approach to underlying masticatory muscle disorder.

Assessment of the masseter stiffness in patients during conservative therapy for masticatory muscle disorders with shear wave elastography.

BACKGROUND: The complex structure of the stomatognathic system plays a vital role in chewing, digestion, speaking, breathing, facial expression and swallowing. Its complexity is the primary reason for creating multidisciplinary teams to manage temporomandibular disorders (TMD). We aimed to assess the masseter stiffness in patients undergoing conservative therapy for masticatory muscle disorders and evaluate the efficacy of manual therapy and stabilization occlusal splint in the treatment of masticatory muscle disorders. METHODS: This uncontrolled prospective cohort study included 35 patients with masticatory muscle disorders. The study lasted for eight weeks. The patients were treated with manual therapy and stabilization occlusal splint and evaluated using shear wave elastography of the masseter muscles and patient-reported outcome measures (PROMs) to assess pain, anxiety, quality of sleep, satisfaction with life and perceived stress. RESULTS: After the treatment, the stiffness of both masseter muscles decreased significantly (by 4.21 kPa). The patients reported a significant reduction in pain. At baseline, the median scores ranged from 5 to 8; after treatment, they ranged from 0 to 1 (p < 0.0001). The patients also reported significant improvement in terms of all patient-reported outcome measures. The reduction in stiffness corresponded to the improvement in pain and PROMs, as shown by correlations which were insignificant for all measures. CONCLUSIONS: Conservative therapy of masticatory muscle disorders involving manual therapy and stabilization occlusal splint is effective. It reduces the masseter stiffness as objectively shown in shear wave elastography and improves subjective PROMs scores, including numerical pain assessment and selected questionnaires. Shear wave elastography has the potential for broad application in clinical practice to monitor masticatory muscle disorders treatment effects due to its objectivity and non-invasive character. Further research is recommended on larger patient populations and longer follow-up. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov ( NCT03844854 ). First posted date: 19/02/2019.

Quantitative assessment of temporomandibular disc and masseter muscle with shear wave elastography.

PURPOSE: To assess the normal stiffness values of temporomandibular joint disc (TMJ) and masseter muscle by shear wave elastography (SWE) in a healthy adult population. This may be helpful in diagnosing and understanding the mechanism of temporomandibular disorders (TMD). METHODS: This prospective study evaluated a total of 160 healthy adult volunteers (77 males, 83 females). The stiffness values of anterior, intermediate and posterior parts of the TMJ disc and masseter muscle were measured. Study cohort was classified into four groups based on age. Additionally, we investigated the changes in mean shear wave elasticity (kPa) and shear wave velocity(m/s) values of disc parts and masseter muscle in closed and open mouth positions, and the correlation of these SWE values with age and gender. RESULTS: Mean stiffness values of the disc were 37.02 ± 23.75 kPa and 3.28 ± 1.09 m/s in the anterior part, 30.47 ± 18.89 kPa and 2.97 ± 1.04 m/s in the intermediate part, 22.61 ± 13.97 kPa and 2.55 ± 0.88 m/s in the posterior part. Stiffness values showed significant decrease in the posterior part compared to the rest of the disc both in males and females. No significant differences in mean stiffness values of masseter muscle related to mouth position, age or gender. CONCLUSION: This study provides the normative quantitative elasticity values of disc and masseter muscle which could be a reference point for upcoming studies. Disc elasticity values are higher in women than men. Maybe this is one of the reason why TMD is more common in women. TMJ disc stiffness was significantly lower in the posterior part. SWE is a useful imaging method that can be used with routine ultrasonography in evaluation of the TMJ disc and masticatory muscles .

[Ultrasound structural assessment of masseter muscles in subjects with different types of craniofacial growth]. / Ul'trazvukovaya otsenka zhevatel'nykh myshts pri razlichnykh tipakh rosta litsevogo cherepa.

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.

Preoperative and postoperative assessment of temporal and masseter muscle size with magnetic resonance imaging in patients undergoing unilateral temporomandibular joint surgery.

The aim of this study was to assess any change between the preoperative and postoperative sizes of temporal and masseter muscles with magnetic resonance imaging (MRI) in patients undergoing unilateral temporomandibular joint surgery. This study was designed and implemented retrospectively. For clinical evaluation, a visual analog scale (VAS) and maximum mouth opening (MMO) were used. In order to make a preoperative diagnosis and perform a 6-month control, muscle size was measured in millimeters (mm) on T1 axial sections in MRI. Statistical analyses were performed using the SPSS 23.0 software package. Numeric variables were compared between two dependent groups using the Wilcoxon signed rank test. Statistical significance was set at p < 0.05. Twelve patients who underwent unilateral discectomy plus dermis-fat grafting, with classical preauricular inverse L incision, were included in the study, and data for eleven female patients were evaluated. The difference in size between the operated and non-operated sides was found to be statistically insignificant at the preoperative stage for both masseter muscle (operated side mM: 13.264 ± 1.822 mm; non-operated side mM: 13.264 ± 2.315 mm; pM = 0.929) and temporal muscle (operated side mT: 20.345 ± 2.609 mm; non-operated side mT: 20.582 ± 2.366 mm; pT = 0.594). There was a significant size reduction in the masseter muscle on the operated side in the postoperative period (preop mM: 13.264 ± 1.822 mm; postop mM: 12.036 ± 1.728 mm; pM = 0.018). Although there was also a size reduction in the operated side of the temporal muscle in the postoperative period, that difference did not reach statistical significance (preop mT: 20.345 ± 2.609 mm; postop mT: 19.445 ± 1.603 mm; pT = 0.182). On the non-operated side, there were no significant postoperative changes in the sizes of either the masseter muscle (preop mM: 13.264 ± 2.315 mm; postop mM: 12.682 ± 2.059 mm; pM = 0.248) or the temporal muscle (preop mT: 20.582 ± 2.366; postop mT: 19.891 ± 3.487 mm; pT = 0.625). Considering the study findings as a whole, a size reduction was observed in the operated side of the masseter muscle after TMJ surgery. The etiology of this change may be surgical trauma to the temporal and masseter muscles, skeletal alteration resulting from condylar change secondary to discectomy, and patients restraining themselves from application of maximum bite force as a result of a self-protection mechanism due to postoperative pain.

Great potential of ultrasound elastography for the assessment of the masseter muscle in patients with temporomandibular disorders. A systematic review.

OBJECTIVE: To summarize the available evidence on the use of elastography in the assessment of the masseter muscle in healthy individuals and patients with masseter muscle disorders. METHODS: Systematic literature review has been performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. RESULTS: 16 of 142 studies identified were analyzed. Elastography was used in seven studies. Heterogeneity was observed in terms of study protocols, devices, patients, units of measure, and results. Elasticity values showed a correlation between the left and right masseter muscle side in healthy people, but not in patients with temporomandibular disorders (TMDs). Elasticity values increased in TMD and were correlated with the severity of TMD symptoms. Phantom studies proved the high reliability of elastography. CONCLUSION: Elastography is a promising tool for the assessment of the masseter muscle elasticity, but the evidence is insufficient. Studies on larger groups are needed to determine the accuracy of elastography to characterize masticatory muscle disorders.

Infrared thermography assessment of patients with temporomandibular disorders.

OBJECTIVES: To assess patients with and without temporomandibular disorders (TMD) infrared thermography according to the differences in thermal radiance using quantitative sensitivity and specificity tests; and to evaluate the thermal asymmetry and the correlation of the thermal intensity with the intensity of pain upon palpation. METHODS: This cross-sectional study performed a quantitative evaluation of clinical and thermographic examinations. The volunteers were evaluated for the presence of TMD using RDC/TMD (Diagnostic Research Criteria for Temporomandibular Disorders), and were divided into two groups: TMD group (n = 45); control group (n = 41), composed of volunteers without TMD, according to the Fonseca Anamnestic Index. The images were assessed for selected regions of interest for the masseter, anterior temporal and TMJ muscles. The mean values ​​of the areas of both groups were compared under the receiver operating characteristic curve. Spearman correlation analysis (non-parametric data) between pain level and mean temperature, by region, and the Pearson's χ2 test was used to verify the association between the presence of temperature and pain asymmetry. The level of significance was set at p < 0.05. RESULTS: Both Groups, with and without TMD, presented with absolute and non-dimensional mean temperature without statistical differences (p>0.05). When correlating temperature with intensity of pain upon palpation, a negative correlation was observed for the masseter muscle. CONCLUSION: Infrared Thermography resulted in low area under the curve, making it difficult to differentiate TMD via thermographic analysis. The intensity of pain upon palpation in patients with TMD may be accompanied by a decrease in local temperature.

Assessment of Masticatory and Cervical Muscles' Thickness by Ultrasonography in Patients with Facial Asymmetry.

OBJECTIVE: The aim of this study was to determine the relationship between the thickness of masticatory and cervical muscles (temporalis, masseter and sternocleidomastoid) and facial asymmetries in young patients. METHODS: 21 subjects were selected, through a detailed anamnesis and clinical examination, in order to assess the normality of oral tissues, the presence of normal occlusion, the absence of alteration in tooth dimensions and of congenital or developmental anomalies of lips, mouth or face. RESULTS: The present investigation showed that temporalis, masseter and sternocleidomastoid muscles in untreated and growing individuals with facial asymmetries are thinner on the omolateral side when compared with controlateral normal side, but in the untreated one this value is more statistically significantly. CONCLUSIONS: In conclusion, the cervical muscle's thickness resulted increased in young patients Ultrasound is beginning to be recognized to have potential use in dentistry as a safe, noninvasive, comfortable and cost-effective adjunct to diagnosis by producing high-resolution images more easily than magnetic resonance (MRI) and computed tomography (CT) (27-kubo).

Assessment of changes in masseter muscle by three-dimensional close-range photogrammetry after Botulinum toxin type-A injection: A case report with review of literature.

Masseter muscle hypertrophy (MMH) is a benign, unilateral or bilateral, painless enlargement. Treatment protocols include surgical excision or a non-invasive option, using botulinum toxin type A (BTX-A). There is no study in the literature that measures this dimensional change in the masseter muscle (MM). The aim of this case report is to present changes in volume and surface area in MM with three-dimensional closer an gestereophotogrammetry (3DCS). For treatment 30 units of BTX-A was injected into the three points hypertrophic muscle and patient records were taken to compare with 3DCS with a non-metric Canon EOS 550 D camera before and after injection. The changes in the surface area and volume of this muscle were mapped and the objective data were obtained. This technique is useful for predicting the results of BTX-A application, and can be a useful tool for better physicianpatient communication.

Three-dimensional computed tomographic assessment of mandibular muscles in growing subjects with different vertical facial patterns.

AIM: The present study was undertaken to assess the relationship between the mandibular muscles and dentofacial skeletal morphology in children with different underlying vertical facial patterns, using three-dimensional computed tomography (3D-CT). METHOD: Thirty children (mean age 12.24 ± 1.57 years) underwent cranial CT examination for diagnostic purposes. 3D-CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter and medial pterygoid muscles. These muscle parameters were also assessed in relation to the vertical facial pattern, gender and skeleto-dental form. RESULTS: Significant differences were found in muscular angulation for subjects with different underlying patterns. Greater masseter volumes were associated with increased facial width. Greater intermolar widths were found in brachyfacial subjects, with less acute muscular angulations in relation to horizontal reference lines, compared with dolichofacial subjects. This was also more obvious in the maxillary arch. CONCLUSION: Clinicians should note the likely differences in masseter and medial pterygoid orientation and volume in subjects with different underlying vertical facial patterns and that these differences may, in turn, be related to both facial skeletal width and naturally-occurring transverse dental arch dimensions.

Quantitative assessment of the masseter muscle's elasticity using Acoustic Radiation Force Impulse.

AIMS: The study proposes Acoustic Radiation Force Impulse (ARFI) assessment of the masseter muscle elasticity in the healthy population and in patients who have undergone head and neck radiation therapy. PATIENTS AND METHODS: Twenty-five healthy controls constituted group A, and 13 patients who had underwent radiotherapy (35Gy minimum) formed group B. ARFI was performed bilaterally in the periphery (P) and the muscle center (C), in relaxation and contraction. Means and standard deviations were obtained for the recorded shear waves velocities (SWV). RESULTS: For group A: in the relaxed right muscle C = 1.87±0.52 m/s and P = 1.96 ±0.55 m/s and in the left muscle C = 1.66 +/- 0.47 m/s, P = 1.67 +/-0.53 m/s. For group B, in relaxation, the right side presented C = 1.67 +/-0.6 m/s, P 1.72 +/-0.56 m/s, the left muscle C = 1.6 +/-0.34 m/s, P = 1.73 +/-0.37 m/s. There were no differences (p> 0.05) between P and C of both groups, regardless of the muscle state. The values for relaxation and contraction in A and B (merged values of the right and left) presented no differences (1.79+/-0.52 m/s vs 1.72 +/-0.73 m/s, p = 0.72 and 1.70 +/-0.48 m/s and vs 1.59 +/-0.77 m/s, p = 0.98). All measurements of group A vs B were not different (1.79 +/-0.52 m/s vs 1.65 +/-0.63 m/s, p = 0.78). CONCLUSIONS: ARFI with SWV measurement enables the quantification of normal and post irradiation elasticity of the masseter. Further studies on a larger population are required to validate the normal and pathologic values.

Assessment of cross-sectional thickness and activity of masseter, anterior temporalis and orbicularis oris muscles in oral submucous fibrosis patients and healthy controls: an ultrasonography and electromyography study.

OBJECTIVES: Oral submucous fibrosis (OSMF) is an insidious chronic disease that is associated with significant functional morbidity and an increased risk for malignancy. It initially affects the lamina propria of the oral mucosa, and, as the disease progresses, it involves the submucosa and deeper tissue, including muscles of the oral cavity, resulting in loss of fibroelasticity. OSMF is a pre-malignant condition mainly caused by areca nut chewing. The aim of this study was to find out the involvement of muscles of mastication and facial expression in patients with OSMF by assessing the cross-sectional thickness and activity of the masseter, anterior temporalis and orbicularis oris muscles by ultrasonography and electromyography and comparing with healthy controls and also to find out any correlation between the ultrasonographic cross-sectional thicknesses of the masseter, anterior temporalis and orbicularis oris muscles with electromyographic activity. METHODS: 40 patients with OSMF were included in the study group, and the patients were divided into four groups on the basis of interincisal mouth opening, i.e. Group I (mouth opening >35 mm), Group II (mouth opening between 30 and 35 mm), Group III (mouth opening between 20 and 30 mm) and Group IV (mouth opening <20 mm). Ultrasonographic cross-sectional thickness and electromyographic activity (amplitude and duration) of the masseter, anterior temporalis and orbicualris oris muscles were recorded in patients with OSMF and 20 controls. Intergroup comparison of ultrasonographic cross-sectional thickness and activity (amplitude and duration) was done, and Pearson's correlation coefficient was applied to find out any relation between ultrasonographic and electromyographic findings. RESULTS: Thickness and activity of the masseter muscle was significantly reduced in Group IV (mouth opening <20 mm) when compared with the control group. The anterior temporalis and orbicularis oris muscles remained unaffected. A positive correlation was observed between the thicknesses of the masseter muscle and the amplitude in Groups I, II and III; the anterior temporalis muscle in Group II and the control group; and the orbicularis oris muscle in Groups II, III and IV. CONCLUSIONS: It was concluded that, among the muscles studied, there was an early involvement of the masseter muscle in patients with OSMF compared with that of other muscles.

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.

[Contributions to the methodology of study in the functional assessment of temporomandibular joint dysfunctional syndrome]. / Contributii la studiul metodologiei de evaluare functionala a articulatiei temporo-mandibulare în sindromul algo-disfunctional.

AIM: Dysfunctional syndrome of the temporomandibular joint through the complexity and variability of the symptoms may result in significant structural and functional changes leading from discomfort to disability and a negative impact on quality of life. MATERIALS AND METHODS: A prospective study was conducted between October 2009-December 2010, in 52 subjects diagnosed with rheumatoid arthritis and complaining of symptoms in the temporomandibular joint. The functional examination of the joint and muscle has included the assessment of the active range of motion, passive range of motion, resistance range of motions of the temporomandibular joint, dermatomes and the pain in the region of masseter, temporalis, median and lateral pterigoids, digastric, sternocleidomastoid and longus colli muscles. The ultrasound examination has included clinical aspects of alignment, shape, dynamics of the mandibular condyle, of the temporal fossa, aspects regarding the temporal and masseter muscles at rest and at contraction phases. RESULTS: The clinical examination highlighted the presence of pain at temporomandibular jointlevel for all tested pacients. The majority complained the pain from moderate to severe level. For the majorityof cases (59,60%) the pain stars spontaneously, during the day time (80,80%) and the night time (50,60%). Over 50% from the research cases complained cracks at the temporomandibular joint level released by a movement. At the oral and dental examination of the research group 55,8% from the tested pacients presented dental cavities toothless partially or totally duet o additionally overworking temporomandibular joint. The limitation of the range of motion is not the most important detected dysfunction, affecting approximately 30% of the cases that have been studied. Pain and spasm in a very large proportion are present in the masseter and temporal muscles regions. Atrophy is present in a lesser extent. The dysfunctional index shows an involvement of the temporomandibular joint, for over 45% of patients tested. The ultrasound examination revealed degenerative inflammatory lesions at a rate of 38.46%, inflammatory lesions at a rate of 28.85% and mixed lesions at a rate of 9.62%. CONCLUSIONS: The research regarding the clinical paraclinical and functional aspects of temporomandibular joint, permited to highlight the fact that rheumatic inflamatory and degenerative, pathology, characterises it self through a high index of morbidity and disability that lowers the life quality. Establishing a treatment plan involves customizing all clinical, functional and laboratory data.

Electromyographic and ultrasonographic assessment of the masseter muscle in normal individuals: a pilot study.

BACKGROUND: recent studies have used ultrasonography with the purpose of measuring muscle cuts. AIM: to characterize the motor control and the morphology of the masseter muscle in normal individuals, verifying the compatibility between surface electromyography and ultrasonography. METHOD: five adult individuals, with no alterations of the stomatognathic system. The adopted assessment procedures for all participants were: 1. Surface Electromyography; 2. Ultrasonography. RESULTS: a high correlation was observed only when comparing both hemifaces in the ultrasonographic assessment (rest 0.95; biting 0.86). CONCLUSION: the results indicate that there is no correlation between the tested methods, suggesting that both methods are complementary and not mutually excludent.

Assessment of ramus, condyle, masseter muscle, and occlusal force before and after sagittal split ramus osteotomy in patients with mandibular prognathism.

PURPOSE: The purpose of this study was to examine the relationship between the morphologies of the masseter muscle and the ramus and occlusal force before and after sagittal split ramus osteotomy (SSRO) in patients with mandibular prognathism. PATIENTS AND METHODS: The study group consisted of 26 patients with mandibular prognathism. All patients underwent bilateral SSRO as well as 3-dimensional computed tomography on which the masseter muscle, ramus, and condyle were measured preoperatively and at 1 year postoperation. Occlusal force and contact area were also recorded with pressure-sensitive sheets. RESULTS: In the cross-sectional area of the masseter muscle, there were no significant differences between the pre- and postoperative status. However, postoperative ramus width and area were significantly larger than preoperative values (P < .0001). Postoperative right condylar area was significantly larger than the preoperative value (P = .0120). Occlusal force and contact area 1 year after surgery were significantly larger than the preoperative values (P = .0016, P = .0190). CONCLUSION: This study suggested that the masseter muscle area did not significantly differ from preoperative status 1 year after SSRO, although occlusal force, contact area, and ramus area and width increased significantly 1 year after SSRO.

Ultrasonographic assessment of local cross-sectional dimensions of masseter muscle sites: a reproducible technique?

Local cross-sectional dimensions (LCSDs) of masseter muscle sites may now be measured non-invasively using ultrasonography. The purpose of the present study was to determine (i) whether the muscle site may affect LCSD measurements and (ii) whether measurements made at identical sites may be reproducible. The study included 17 patients who had signs and symptoms of temporomandibular disorders (TMD). Bilateral ultrasonographic investigation was performed with a linear (B-scan) 7.5 MHz small-part transducer to visualize the antero-superior, antero-inferior, medio-superior, medio-inferior, postero-superior, and postero-inferior sites of the masseter muscle. Measurements were made in two sessions with a time interval of at least five minutes. Data were analysed for reproducibility by using the intraclass correlation coefficient (ICC) and the method error (ME). Muscle site had no significant effect on muscle measurements (P = 0.090). Measurements from the various side-related sites did not differ significantly (P = 0.425). Measurements recorded at a given site were consistent across the testing sessions (P = 0.605). The muscle site with highest reproducibility was the medio-inferior site (ICC = 0.92; ME = 6.4%). The data suggest that ultrasonography is a reproducible method for measuring LSCDs of the masseter muscle.

Odontogenic infection pathway to the submandibular space: imaging assessment.

The aims of this study were to determine the pathways of odontogenic infection spread into the submandibular space and their relationship to the clinical symptoms. Computerized tomography (CT) and magnetic resonance (MR) images of 33 patients with submandibular involvement were analyzed. The spread of infection was evaluated by lateral asymmetry of the shape and density of the fascial spaces and tissues, and by obliteration of the interfascial fat spaces. Imaging findings were classified into three types: in 19 patients (57.6%), infection spread through the mylohyoid muscle or sublingual space (type I). In five patients (15.2%), infection spread through the bony structures of the mandible with periosteal reaction or perforation of the cortical plate (type II) and was associated with relatively mild symptoms. In four patients (12.1%), infection spread from the masticatory space (type III). Seven of 11 patients with dysphagia or fever showed submandibular involvement spreading into the parapharyngeal space. CT and MR imaging clearly demonstrated different pathways of the spread of odontogenic infection into the submandibular space, which influenced the manifestation of clinical symptoms.