Masseter Research Articles

A Controlled Phase 2b Trial to Assess the Efficacy and Safety of a Single Intervention of OnabotulinumtoxinA for Treating Masseter Muscle Prominence.

Masseter muscle prominence (MMP) is a benign condition characterized by a wide, square, or trapezoidal lower facial shape, which may be considered undesirable. To evaluate onabotulinumtoxinA (onabotA) efficacy and safety for MMP treatment. In a phase 2b study, adults with investigator- and participant-assessed bilateral grade 4/5 MMP on the 5-grade MMP Scale (MMPS) and MMPS-Participant, respectively, were randomized 1:1:1 to receive a single intramuscular injection of onabotA 48 U, 72 U, or placebo in the masseter muscles. The primary endpoint was the proportion of subjects achieving investigator-assessed MMPS grade ≤3 at day 90. Adverse events were monitored throughout. Subjects received onabotA 48 U (n=53), 72 U (n=46), or placebo (n=46). Significantly greater proportions achieved MMPS grade ≤3 with onabotA vs placebo (90.6%, 91.3%, and 21.7% for onabotA 48 U, 72 U, and placebo, respectively, at day 90; P<0.0001). Improvements in lower facial volume, width, and angle were significantly greater for onabotA vs placebo at all timepoints. At day 90, the proportion of subjects perceiving improvements was significantly greater with onabotA treatment vs placebo. Significantly more subjects were "satisfied/very satisfied" with onabotA vs placebo through day 180. Treatment was well tolerated; both onabotA groups had a similar incidence of treatment-emergent adverse events (TEAEs). Nasopharyngitis (onabotA, 3.9% vs placebo, 0%) and upper respiratory infection (2.9% vs 0%, respectively) were the most common TEAEs. One injection of onabotA 48 U or 72 U was well tolerated and effective in reducing MMP severity as assessed by investigators and subjects.

Three-Dimensional Changes of Masseter Muscle in Patients With Class III Asymmetry After Bimaxillary Orthognathic Surgery.

The present study was aimed to comprehensively evaluate changes in the masseter muscle in patients with Class III facial asymmetry after bimaxillary orthognathic surgery and explore potential correlations between masseter muscle changes and facial morphology or postoperative mandibular stability. Fifty-two eligible patients with Class III facial asymmetry who underwent Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO) with or without genioplasty between January 2019 and June 2023 were included. Cone-beam computed tomography (CBCT) was collected for each patient at 3 stages: 1 week preoperatively (T0), immediately after surgery (T1), and at least 12 months postoperatively (T2). Masseter muscle changes including volume, surface area, length, and width were measured using ITK-SNAP and 3D Slicer and correlations between these changes and facial morphology, skeletal stability were further explored. The length, width, surface area, and volume of the nondeviated side (NDS) masseter muscle were greater than those of the deviated side (DS) before surgery (T0). These parameters of masseter muscle at both sides decreased significantly after surgery (T2), except the length of DS masseter increased slightly. The differences in bilateral masseter length, width, surface area were reduced significantly after surgery and NDS masseter muscle remained greater than DS masseter muscle. Changes in the NDS masseter surface area negatively correlated with FH-MP. However, no significant correlations between masseter volume changes and mandibular postoperative skeletal stability were found. Taken together, our results revealed detailed masseter muscle changes following surgical correction of Class III facial asymmetry.

Using Deep Learning to Perform Automatic Quantitative Measurement of Masseter and Tongue Muscles in Persons With Dementia: Cross-Sectional Study.

Sarcopenia (loss of muscle mass and strength) increases adverse outcomes risk and contributes to cognitive decline in older adults. Accurate methods to quantify muscle mass and predict adverse outcomes, particularly in older persons with dementia, are still lacking. This study's main objective was to assess the feasibility of using deep learning techniques for segmentation and quantification of musculoskeletal tissues in magnetic resonance imaging (MRI) scans of the head in patients with neurocognitive disorders. This study aimed to pave the way for using automated techniques for opportunistic detection of sarcopenia in patients with neurocognitive disorder. In a cross-sectional analysis of 53 participants, we used 7 U-Net-like deep learning models to segment 5 different tissues in head MRI images and used the Dice similarity coefficient and average symmetric surface distance as main assessment techniques to compare results. We also analyzed the relationship between BMI and muscle and fat volumes. Our framework accurately quantified masseter and subcutaneous fat on the left and right sides of the head and tongue muscle (mean Dice similarity coefficient 92.4%). A significant correlation exists between the area and volume of tongue muscle, left masseter muscle, and BMI. Our study demonstrates the successful application of a deep learning model to quantify muscle volumes in head MRI in patients with neurocognitive disorders. This is a promising first step toward clinically applicable artificial intelligence and deep learning methods for estimating masseter and tongue muscle and predicting adverse outcomes in this population.

Forensic facial reconstruction: A computer tomography study of facial soft tissue thickness in Nigerian adult male multi-ethnic population.

Facial soft tissue thickness (FSTT) was measured from computer tomography scans of 55 Nigeria adult males. Forensic facial reconstruction (FFR) with own population FSTT values can be vital in recognition of skeletal remains and has been used as an adjunct in forensic science.There are no published FSTT values for this population. Measurements were obtained at 12 mid-sagittal and 19 bilateral points totalling 50 and by use of a software package called RadiAnt. In comparison to previous studies in Africa, measurements were taken from more points and with a diverse age of 18 to 100 years. Mean FSTT values were determined for these combined Nigerian male ethnicities. These values will suffice in FFR for this population and for the Hausa adult male. This population homogenously showed more soft tissue volumes on the left than the right side at all FSTT points with the most relative difference at the frontal eminence and the least at the mid-point of the masseter muscle. The low relative difference at the mid-masseters may relate with the soft floury diets of this population. These combined Nigerian male ethnicities midline FSTT values showed significant differences in the lower third of the face when compared with other population data. The values for the right side of the face shows even more substantial differences at multiple points when compared with published data of other populations. The change with age compares well with other studies. These data will be applicable for FFR in the CNME than data of other populations.

P2Y12 signaling in muscle satellite cells contributes to masseter muscle contraction-induced pain.

P2Y12 signaling in muscle satellite cells contributes to masseter muscle contraction-induced pain.

The efficacy of combining pulsed radiofrequency with low-temperature continuous radiofrequency for the treatment of primary trigeminal neuralgia: a randomized controlled trial.

Pulsed radiofrequency (PRF) combined with low-temperature continuous radiofrequency (CRF) might be a novel technique for relieving trigeminal neuralgia (TN). This study aimed to evaluate the efficacy and safety of high-voltage PRF combined with low-temperature CRF in primary TN. This randomized controlled trial was performed between December 2, 2020, and October 26, 2022. Eligible patients with TN were randomly assigned at a 1:1 ratio to receive either PRF with a voltage of 70 V at 42°C for 600 seconds followed by CRF at 60°C for 270 seconds (PRF+CRF group) or PRF with a voltage of 70 V at 42°C for 600 seconds (PRF group). The primary outcome was the response rate to treatment after 12 months. The secondary outcomes were the proportion of responders at 1 day, 1 week, 2 weeks, 1 month, 2 months, 3 months, and 6 months following the procedure and the 11-point numeric rating scale (NRS) scores at 1 day, 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months, and 12 months following the procedure. Adverse events associated with surgery were also observed. A total of 169 patients with TN were screened, and 146 patients were randomized. The groups were well balanced across baseline characteristics. The percentage of responders at 12 months after surgery was significantly greater in the PRF+CRF group compared with the PRF group (83.6% [61/73] vs 67.1% [49/73], risk ratio 1.2 [95% CI 1.0-1.5], absolute difference 16.5%; p = 0.021). There was a higher proportion of responders after 1 day, 1 week, 2 weeks, 1 month, 2 months, 3 months, and 6 months (ratio difference 16.5%, 35.6%, 16.4%, 12.3%, 12.3%, 12.3%, and 15.1%, respectively; all p < 0.05). Moreover, lower NRS scores were observed in the PRF+CRF group at 1 day, 1 week, 2 weeks, 1 month, 2 months, 3 months, 6 months, and 12 months following the procedure (all p < 0.05). Postoperative facial numbness scores were higher in the PRF+CRF group at 1 day, 1 week, 2 weeks, 1 month, and 2 months (all p < 0.05). Overall, 5.5% of patients in the PRF+CRF group and no patients in the PRF group reported masseter muscle weakening. No other complications, such as anesthesia dolorosa and corneal anesthesia, were observed in either group. High-voltage PRF combined with low-temperature (60°C) CRF could provide a significant improvement compared with high-voltage PRF alone. Clinical trial registration no.: NCT04174443 (ClinicalTrials.gov).

Determination of optimal points for botulinum toxin injections in the treatment of patients with temporomandibular myofascial pain syndrome

To understand the processes occurring during the development of temporomandibular myofascial pain syndrome, a clear description of the anatomical components is necessary. In the literature, the term «stomatognathic system» is used for this, the elements of which are the temporomandibular joint, masticatory muscles and the dental periodontal complex. Each component of the system is influenced by a number of factors, primarily psychological, which causes the subjectivization of clinical manifestations from headaches to pathological tooth cutting and the development of temporomandibular joint dysfunction. One of the methods of treating this pathology is to inject botulinum toxin type A into the chewing muscles. However, the question of the choice of methods of administration of botulinum toxin and its dosage remains relevant.Materials and methods. Botulinum toxin injections were performed outside and intraoral in 30 patients with temporomandibular myofascial pain syndrome. The effectiveness of the therapy was evaluated on the basis of clinical examination data, analysis of the degree of mouth opening before the start of treatment, after 14 days, 6 and 12 months.Results. The high efficiency of botulinum toxin type A injections in the treatment of the above pathology has been proven.Conclusion. It is important to evaluate the effectiveness of treatment based on the developed clinical examination methods, if necessary, correct it in a timely manner at all stages of treatment and follow-up of patients with temporomandibular myofascial pain syndrome.

Subcutaneous implantation of tooth germ stem cells over the masseter muscle in mice: An invivo pilot study.

Subcutaneous implantation of tooth germ stem cells over the masseter muscle in mice: An invivo pilot study.

Postmortem proteolysis and its indicators vary within bovine muscles: Novel insights in muscles that differ in their contractile, metabolic, and connective tissue properties

Postmortem proteolysis and its indicators vary within bovine muscles: Novel insights in muscles that differ in their contractile, metabolic, and connective tissue properties

Botulinum toxin type A inhibits hyperalgesia in the rat masseter muscle in a carrageenan model of myofascial pain

Botulinum toxin type A inhibits hyperalgesia in the rat masseter muscle in a carrageenan model of myofascial pain

Assessment of pain location according to different types of bruxism.

This study aimed to assess the influence of bruxism types and frequencies on pain localisation in individuals with temporomandibular disorders (TMD). The study participants included 100 TMD patients. Participants consented to undergo clinical evaluations based on the Diagnostic Criteria for Temporomandibular Disorders Assessment Instruments Protocol (DC/TMD). Pain was determined by palpating the temporal and masseter muscles and the temporomandibular junction (TMJ). The oral behavior checklist (OBC) was used in DC/TMD to assess participants' risk for parafunctional movements and types of bruxism. The parafunctional risk assessment was performed with the assessment method reported by The International Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Consortium Network. Most participants are at high risk for parafunction. There was a statistically significant relationship between masseter, temporal and TMJ pain and parafunctional movements (p < 0.05). Masseter pain on palpation showed significant relationships with sleep bruxism and awake grinding frequency (p < 0.05). Temporal muscle pain on palpation showed significant relationships with the presence and frequency of awake clenching (p < 0.05). A significant correlation exists between TMJ pain on palpation and awake grinding and clenching and with awake clenching frequence (p < 0.05). Based on their frequency and presence, different types of bruxism may be associated with different pain symptoms.

Tooth loss-associated neuroplasticity of mastication-related motor cortical neurons.

Tooth loss-associated neuroplasticity of mastication-related motor cortical neurons.

Effects of botulinum toxin type A on the masseter muscles of a patient with a temporomandibular joint disorder of muscular origin: A case report

Effects of botulinum toxin type A on the masseter muscles of a patient with a temporomandibular joint disorder of muscular origin: A case report

Ultrasound protocols for measuring masseter muscle

Ultrasound protocols for measuring masseter muscle

A Prospective Clinical Trail to Evaluate the Role and Efficacy of Botulinum Toxin Type-A for Masseter Muscle Hypertrophy

ABSTRACT Background: Masseter muscle hypertrophy (MMH) is a condition characterized by the enlargement of the masseter muscles, leading to facial asymmetry, pain, and functional issues. Traditionally treated through surgical resection, Botulinum toxin type-A (BTX-A) has emerged as a minimally invasive alternative that reduces muscle bulk and relieves symptoms. Objective: This study aims to evaluate the efficacy and safety of BTX-A in reducing muscle size, and pain, and improving aesthetic outcomes in patients with MMH. Methods: A prospective clinical trial was conducted with five patients diagnosed with bilateral MMH. Each patient received 30 units of BTX-A per side, with follow-ups at 3 and 6 weeks post-injection. Outcomes were measured using the Masseter Muscle Prominence (MMP) scale, pain scores, and patient satisfaction questionnaires. Descriptive statistics and paired t-tests were used for analysis. Results: All patients demonstrated a significant reduction in muscle size, averaging 60% at 6 weeks. Pain scores were reduced by 80–100%, and aesthetic satisfaction scores ranged from 8 to 10. No severe adverse effects were reported, with only mild transient bruising and masticatory fatigue observed. Conclusion: BTX-A is an effective and safe option for the management of MMH, providing significant aesthetic and functional improvements with minimal side effects. Further research with larger sample sizes and longer follow-ups is recommended to validate these findings.

A Study on Three-Dimensional Expression in Body Painting through a Prism of Skeletal Muscle: Focusing on Base Makeup

This study aimed to explore AR-based highlight and shading design through the understanding of middle-aged women’s face shapes and their phrenological features in aging face, with the intention of proposing how to apply base makeup to make them look younger. The findings of this study are as follows. First, for egg-shaped face, highlighting applied to under the eyes, and from the center of the forehead to the glabella, and down 1/2 of the bridge of the nose. And applied in a round way with brightness in +1.5 phase lighter than a skin tone in order for the zygomatic part where levator labii superioris is placed, both cheeks and the center of the chin where the mentalis are placed to appear chubby. As shading is applied in a diagonal line way following follow the contours of the face, from the alveolar process of the mandible and maxilla which has it origin at masseter muscle and biceps muscle, and zygomatic part of zygomatic arch above the ear, to the chin. And brightness is applied in –1.5 phase darker than the skin tone. Second, for long face, highlighting is given in a way to connect as short as possible the forehead and the glabella to the bridge of the nose, and to divide the forehead and under the eyes horizontally to enable the cheeks to appear chubby. With the chin omitted. And connecting frontalis to temples and above corrugator supercilii muscle in a round way following both temples and above the corrugator supercilii muscle, with brightness applied in +1.5 phase lighter than the skin tone. Shading is overall horizontally applied to parts comprising the tip of the forehead where frontalis and galea aponeurotica are placed, the lower end of nasalis muscle, and mentalis; and brightness is applied in –1.5 phase darker than the skin tone. Third, for round-shaped face, highlighting is placed on under the eyes, from the center of the forehead to the glabella, and down 1/2 of the bridge of the nose. And is given in a way for frontalis to appear more round and wide, and in a long way to connect under the eyes to levator labii superioris muscle of front cheek, with the application of brightness in +1 phase lighter than the skin tone. In practice, such highlighting proved to have the desired effect. Shading is placed on the masseter muscles of both cheeks, the zygomatic parts of zygomatic arch of both sides of the face, and nasal walls, in an oblique line way from zygomaticus major and minor to the outer sides of the lips, with the application of brightness in-1phase darker than the skin tone. Fourth, for square-shaped face, highlighter is used on the T zone in a vertically round way toward above corrugator supercilii muscle and nasal muscle. And is applied to connect the glabella to long down the bridge of nose, in a diagonal way from under the eyes to the tip of the nose, and in a long way from the center of mentalis muscle to the lower corner of the mandible of the line of the tip of the chin. Brightness is applied in –1 phase darker than the skin tone. The practice proved such highlighting to have the desired effect. Shading is curved on both sides of the angular chin line and forehead; and it is applied in an oblique way from zygomaticus major and minor muscles under zygomatic bones toward oral angle.

Differences in the Size and Morphology of Masseter Muscle and Mandible Assessed Using Three-Dimensional Computed Tomography.

Mandibular angular hypertrophy and hemifacial microsomia involve deformities in the mandibular region, resulting in facial asymmetry that severely affects patients' appearance. This study evaluated the masseter muscle-mandibular correlation in patients with hemifacial microsomia and those with mandibular angular hypertrophy using three-dimensional CT and compared them with normal individuals. This study included 310 participants. Craniofacial scans were performed using three-dimensional CT in all participants to obtain masseter muscle and mandibular size and morphology data. In the normal population, there are sex differences in the shape and size of the masseter muscle and mandible, and the size of masseter muscle correlates with the mandible. In all three groups, there were differences in morphology and size of masseter muscle and mandible between the right and left sides (healthy and affected sides). Compared with the normal population, patients with hemifacial microsomia have a smaller masseter muscle and mandible on the affected side, while the healthy side is similar to the normal population. The measurement results significantly differed among patients with different severities of hemifacial microsomia and tended to worsen with increasing severity. In addition, the masseter muscle and mandibles on the left and right sides of patients with mandibular hypertrophy were larger than those of the normal population. Three-dimensional CT proved reliable and accurate for measuring the masseter muscle and mandible size and morphology. We report masseter muscle and mandible characteristics in different populations. These findings can guide medical personnel in determining the diagnosis, treatment, and prognosis of these diseases. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Optimizing the Host Niche to Fuel Cleft Lip Muscle Regeneration.

Lip muscle reconstruction is a key strategy for cleft lip repair, but the outcome of muscle regeneration is suboptimal. The lack of relevant models restricts studies on cleft lip muscle regeneration. In this study, we developed an animal xenograft model by transplanting muscle samples from patients with cleft lip into different host sites in immunodeficient mice. The grafted muscles were harvested after 1, 2, and 5 months to investigate the temporal dynamics of myofiber growth and maturation. Comparisons were made among muscle biopsies, xenografts in the masseter (MAS) muscle of the mice, and xenografts in the tibialis anterior (TA) muscle of the mice to determine the optimal host niche. The muscles from cleft lip patients underwent an active degeneration-regeneration cycle. The fiber diameter in the MAS niche was significantly larger than that in the TA niche and was comparable to the fiber diameter of the donor biopsy from which it originated. The innervation and blood supply of the muscle grafts at the MAS host site were also superior to those of the grafts at the TA host site. The MAS muscles of mice provided the most favorable microenvironment for cleft lip muscle regeneration. This patient-centered xenograft model offers a platform for cleft lip muscle regeneration studies.

Jaw-Muscle Structure and Function in Primates: Insights Into Muscle Performance and Feeding-System Behaviors.

The jaw-adductor muscles drive the movements and forces associated with primate feeding behaviors such as biting and chewing as well as social signaling behaviors such as wide-mouth canine display. The past several decades have seen a rise in research aimed at the anatomy and physiology of primate chewing muscles to better understand the functional and evolutionary significance of the primate masticatory apparatus. This review summarizes variation in jaw-adductor fiber types and muscle architecture in primates, focusing on physiological, architectural, and behavioral performance variables such as specific tension, fatigue resistance, muscle and bite force, and muscle stretch and gape. Paranthropus and Australopithecus are used as one paleontological example to showcase the importance of these data for addressing paleobiological questions. The high degree of morphological variation related to sex, age, muscle, and species suggests future research should bracket ranges of performance variables rather than focus on single estimates of performance.

Therapeutic exercises, manual therapy, and health education program for adolescents with temporomandibular disorders: face-to-face and online multimodal rehabilitation protocol for a randomized controlled clinical trial

BackgroundMultimodal rehabilitation has shown good results in adults with temporomandibular disorder (TMD), but there is still doubt regarding the protocol’s ideal format (face-to-face or online), and its effectiveness among adolescents. The purpose of this study is to describe a randomized clinical trial protocol of face-to-face and online multimodal rehabilitation, in adolescents with TMD, and to determine its effects on pain, peripheral oxygenation of the masseter muscle, and mandibular range of motion, kinesiophobia and parafunction.MethodsA randomized, controlled clinical trial, blinded to statistical analyses, will be carried out, involving 26 adolescents, diagnosed with TMD. After randomization, the participants will be allocated into two groups: (1) telerehabilitation and (2) face-to-face treatment groups. Each group will undergo an initial assessment, followed by three treatment sessions, reassessment, and follow-up. Appointments and reassessments will be face-to-face, with instruments validated and adapted for adolescent age groups. The intervention protocol also aims at practicality, ease of execution, and strategies for the patient to easily self-manage and perform independently, adapted for face-to-face or online formats. The Diagnostic Criteria for Temporomandibular Disorders, physical and psychosocial aspects, algometry, near-infrared spectroscopy, and the Tampa scale for kinesiophobia will be used to assess the outcomes.DiscussionIt is expected that this study will contribute to online and face-to-face assessments and demonstrate the differences in the practice of rehabilitation of adolescents with TMD. Data will be published after the study is completed, and if the benefits are proven, care modalities may be implemented.Trial registrationREBEC—RBR-5scd5tm, UTN code: U1111-1288–4495. Registered on 19 May 2023.