Botulinum Toxin Injections for Masseter Reduction in East Asians

Treatment of masseter muscle hypertrophy with botulinum toxin type A injection: A review of adverse events

BACKGROUND

The popularity of noninvasive botulinum toxin type A (BTX-A) injections for masseter muscle hypertrophy is increasing among Asian individuals with a square-shaped lower face.

AIMS

This study aimed to analyze the adverse events (AEs) caused by BTX-A injections into the masseter muscle.

PATIENTS/METHODS

This observational study retrospectively evaluated 46 250 patients who underwent BTX-A injections into the masseter muscle in 2022. The inclusion criteria were the diagnosis of an AE by the physician at the return visit and subsequent follow-up of progress (n = 223). The patients who were lost to follow-up (n = 40) were excluded from the study.

RESULTS

Among the 223 patients with AEs, the most common AE was paradoxical bulging (88.3%, n = 197/223). The average period from treatment until confirmation of improvement was 159.6 ± 113.6 days (range 13-667 days) for all AEs, all of which were temporary. The period until improvement was 166.1 days in the intervention group (n = 122) and 151.9 days in the observation group (n = 101) (p = 0.24). As the period until improvement of AEs included the period until the patients visited the clinics and the improvements were confirmed by physicians, the actual period was likely to have been shorter.

CONCLUSIONS

(1) All AEs were temporary. (2) All AEs improved within 22.2 months (within 5.3 ± 3.8 months on average). (3) There was no significant difference between the intervention and observation groups in the period until the improvement of AEs.

Novel single-entry point injection technique for masseter hypertrophy treatment using botulinum neurotoxin based on patient-reported comfort

INTRODUCTION

Botulinum neurotoxin (BoNT) injections are widely used for the treatment of masseter muscle hypertrophy in Southeast Asia. However, there remains a lack of consensus regarding the optimal injection technique. This study aimed to compare the efficacy and patient discomfort associated with single-entry point injections versus multiple three-point injections for masseter muscle hypertrophy treatment with BoNT.

MATERIALS AND METHODS

Sixteen participants, comprising both male and female Korean adults aged 22-63, were enrolled in the study. On the left side of the face, single-entry point injections were administered, followed by multidirectional injections, while on the right side, three-point injections were given. Pain intensity during the procedure was assessed using visual analogue scale scores.

RESULT

Our results revealed that participants experienced lower levels of pain with single-entry point injections compared to three-point injections (average visual analogue scores of 3.31 and 5.19, respectively).

CONCLUSION

These findings highlight the potential benefits of single-entry point injections in reducing patient discomfort during masseter muscle hypertrophy treatment with BoNT. We advocate for further research to validate these findings and encourage practitioners to consider single-entry point injections as a viable option for enhancing treatment outcomes in their clinical practice.

Three-Dimensional Photography for Evaluating the Effectiveness of Botulinum Toxin Injection for Masseter Hypertrophy

BACKGROUND

Masseter hypertrophy is a common condition that causes a undesirable square face, and often treated with botulinum toxin type A (BoNTA). Subjective assessments of BoNTA effectiveness vary from physician to patient, necessitating an objective approach for evaluation. This study introduces three-dimensional photography (3DP) for the first time in clinical assessment to evaluate BoNTA treatment for masseter hypertrophy.

METHODS

Ten patients received 36U of BoNTA at three injection points on each side masseter muscle. 3DP scanner using Artec Eva® was taken at the first, third, and sixth postoperative months for objective evaluation. Patient's self-perceived prominence, patients self-rated satisfaction, and physicians provided 5-grade scores were the subjective indicators.

RESULTS

A significant decrease in left masseter volume at the sixth month (P = 0.002, P = 0.004 at rest and clenching, respectively) was observed. Patient's self-perceived prominence decreased at the first (P = 0.021) and third (P = 0.039) months. Physicians' scores significantly decreased at all postoperative months. No significant changes were noted in the right masseter volume and patients self-rated satisfaction. Patient self-rated satisfaction did not consistently correlate with objective measures, except for left masseter with clenching at the sixth month.

CONCLUSION

Three-dimensional photography accurately quantifies facial changes post-BoNTA treatment. Despite objective improvements, patient satisfaction may not align consistently. Reliable assessment tools are crucial in cosmetic surgery to manage expectations and prevent disputes.

LEVEL OF EVIDENCE IV

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 .

Prospective Analysis of the Effectiveness of Targeted Botulinum Toxin Type A Injection Using an Ultrasound-Guided Single-Point Injection Technique for Lower Face Contouring

Background: Botulinum toxin type A (BoNT-A) injection is widely used for masseter hypertrophy. Traditional BoNT-A injection methods often incorporate landmark-guided blind injections, which approximate the shape of the masseter muscle inject across various points. Conversely, ultrasound (US)-guided injection techniques offer real-time visualization and dynamic monitoring, enhancing accuracy. Patients and Methods: 50 patients who underwent BoNT-A injections were included in this trial. One on the face side received a landmark-guided injection, and the other side was treated with a US-guided injection. Initial and post-procedure measurements of muscle thickness at the upper, middle, and lower regions were collected using ultrasound. Results: Both methods led to a significant reduction in muscle thickness one month after injection. In the upper area, the absolute difference in muscle thickness between the two methods was observed as a mean ± standard deviation (SD) value of 0.37 ± 0.0314 (p < 0.0001), indicating a superior effect with US-guided injection. Similarly, in the middle area, the mean ± SD difference was 0.41 ± 0.0608 (p < 0.0001) and in the lower area, the mean ± SD difference was 0.24 ± 0.0134 (p = 0.0004). Conclusions: This study demonstrated that the US-guided single-point injection technique is a more effective and accurate method for BoNT-A injection compared to the conventional method.

Aesthetic Considerations for Neuromodulator Use in Transgender Patients

BACKGROUND

The aesthetic dimension of transgender experiences involves various aspects linked to the visual representation and expression of one's gender identity. Nonsurgical cosmetic procedures, such as neuromodulators, have consequently become a viable treatment option for patients with gender dysphoria because of the ability to yield significant, although temporary, results with minimal associated risks and downtime.

OBJECTIVE

To comprehensively review literature pertaining to the aesthetic considerations for use of neuromodulators in transgender and nonbinary individuals.

MATERIALS AND METHODS

A literature review of PubMed/MEDLINE for studies was published through January 2024 for nonsurgical facial and body modification using neuromodulators. Searches were conducted with relevant keywords. Peer-reviewed articles and their references published within the past 10 years were given emphasis in the review.

RESULTS

Based on the limited publications to date, the authors prepared a comprehensive review on indications for neuromodulator treatment in this population, including brow positioning, lower face contouring, lip eversion, trapezius slimming, and leg contouring.

CONCLUSION

Dermatologists play a crucial role in facilitating the achievement of gender affirmation goals.

Lifting With Neuromodulators

BACKGROUND

The use of botulinum toxins for facial rejuvenation and improvement of dynamic wrinkles has become a mainstay in the aesthetic treatment armamentarium. However, using these same neuromodulators (NMs) for lifting the structures of the face, is a newer addition to antiaging protocols. The muscles of facial animation all interplay with each other. Lifting can be accomplished by treating those muscles that are responsible for depression, leaving the elevators unopposed and resulting in a rejuvenated, lifted outcome. Brow lifting, cheek lifting, and even contouring of the lower face and jawline are all possibilities using NMs.

OBJECTIVE

To review the literature and current practices in techniques for lifting the different anatomic facial zones.

METHODS

The authors present and discuss the published data and personal experiences of using NM for lifting and retraining of the facial musculature. This article will discuss the effects and approaches to lifting with botulinum toxin injections, including the potential success and side effects associated with these off-label injections.

RESULTS/CONCLUSIONS

The use of botulinum toxins has expanded beyond its traditional use as a reducer of dynamic wrinkles. A significant amount of published data now exists for the off-label use of botulinum toxins for lifting and shaping the face. These can be considered advanced techniques as each region has its own anatomic intricacies and side effects can occur. More placebo-controlled objective data would also help elucidate exact dosing strategies for each region.

Cosmetic injectables in skin of color: A review of uses, safety, and effectiveness of neuromodulators and dermal fillers

BACKGROUND

Skin of color (SOC) individuals represent a growing market for cosmetic injectables and can have different aesthetic goals and responses to treatment.

OBJECTIVE

A review of the uses, safety, and effectiveness of injectable neuromodulators and dermal fillers in SOC individuals.

METHODS AND MATERIALS

A search of the PubMed/MEDLINE database was conducted from August 1960 to December 2020. Studies that were included either had a focus on SOC (>20% SOC study participants) or dedicated article content commenting on the safety and/or efficacy of injectables in SOC participants.

RESULTS

Of the 503 publications identified, a total of 88 articles were selected for this review. Differences in aging and cultural factors can influence aesthetic goals amongst SOC populations. Available data suggests that botulinum toxin (BTX) and dermal fillers are safe and effective in SOC populations, with the largest amount of data existing for Asian populations. There remains a paucity of research on Black and Latinx populations.

CONCLUSION

BTX and dermal fillers are generally effective and well tolerated in SOC populations, particularly Asian populations for which the greatest amount of data exists. More high quality, randomized controlled trials in Black and Latinx populations are warranted.

Exploring botulinum toxin's impact on masseter hypertrophy: a randomized, triple-blinded clinical trial

The present study aimed to assess the effectiveness and functional adverse effects of a single and multiple injections of botulinum toxin A (BoNT-A) for masseter hypertrophy (MH). Twenty-six women complaining about lower third facial enlargement due to MH, received 75 U of BoNT-A (abobotulinum toxin) in each masseter muscles. After 3 months, patients were randomly assigned to receive a second treatment session of Saline Solution: (G1; n = 11) or BoNT-A: (G2; n = 12). Muscle thickness (ultrasound), electrical activity (electromyography; EMG), masticatory performance, and subjective perception of MH were evaluated. Follow-up was performed at 1, 3 and 6 months. Muscle thickness, EMG activity, and masticatory performance were analyzed using ANOVA two-way and Sidak test as post-hoc. Masticatory performance was analyzed by the Friedman's test and Mann-Whitney test. Regarding inter-groups comparisons, there was a significant decrease in the left masseter muscle thickness in the G2 group at the 6 month follow-up (p < 0.02). For EMG, significant differences were evident at the 6 month assessment, with higher masseter activity for G1 (p < 0.05). For masticatory performance, no significant differences were observed throughout the study (p > 0.05) and a higher improvement in subjective perception of MH was observed in the 1 month follow-up for G2 (p < 0.05). In conclusion, BoNT-A is effective for MH, however multiple injections cause functional adverse effects in masseter muscle.

Functional and esthetic effects of botulinum toxin injection into the masseter muscles: evaluation of 80 patients from a dermatological perspective

BACKGROUND

Masseter muscle hypertrophy is characterized by a symmetrical or asymmetrical increase in muscle volume. Although it can be asymptomatic, it may be associated with bruxism. Therefore, patients may seek intervention for esthetic and/or functional concerns. This study aimed to establish patient characteristics, purpose of undergoing botulinum toxin injection into the masseter muscles, efficacy, and side effects of the procedure at a dermatology clinic.

METHODS

A retrospective chart review was carried out over a period of one year from January 2022 to January 2023 for the patients who underwent botulinum toxin injection into the masseter muscles. The general characteristics of patients, the purpose of botulinum toxin treatment, relief levels regarding bruxism according to the Visual Analog Scale (VAS), side effects, and complications were recorded.

RESULTS

The study group comprised 74 female and 6 male patients with a mean age of 31.20 ± 6.71 years. Eighteen (22.5%) patients were treated only for narrowing the lower face contour, 28 (35%) patients were treated only for the relief of bruxism, and 34 (42.5%) patients were treated for both indications. Fifteen (18.8%) patients experienced 16 treatment-related side effects, including two (2.5%) with smile asymmetry and two (2.5%) with paradoxical bulging.

CONCLUSIONS

Botulinum toxin injection into the masseter muscles with the intention of lower face contouring and/or relieving bruxism offers a minimally invasive, safe, and effective treatment option. Although it has a favorable safety profile, the risks of significant side effects or complications remain.

Efficacy and Safety of PrabotulinumtoxinA in Subjects With Benign Masseteric Hypertrophy: A Double-Blind, Randomized, Placebo-Controlled, Multicenter, Phase 3 Trial and Open-Label Extension Study

BACKGROUND

Despite the widespread use of botulinum toxin (BTX) injection for the treatment of masseter muscle hypertrophy (MMH), there is no standard treatment option.

OBJECTIVE

We report the efficacy and safety for BTX in MMH over a period of 48 weeks.

METHODS

In double-blinded, placebo-controlled phase 3 trials, 180 patients (randomized 1:1) received treatment with placebo (normal saline) or prabotulinumtoxinA (48 units). Masseter muscle thickness (at maximal clenching and resting positions), 3D imaging analysis, and masseter muscle hypertrophy scale grades were analyzed at each time point. After the 24-week CORE study, all patients who met the same criteria of the CORE study at week 24 ( n = 114) received only prabotulinumtoxinA, regardless of previous treatment, for an additional 24 weeks (48 weeks in total) for the open-label extension study.

RESULTS

The largest differences in mean and percent changes from baseline in masseter muscle thickness were observed at 12 weeks, and there were significant differences between the 2 groups at all time points (all p < .001). The effect was independent of the number of injections. No serious adverse event was observed.

CONCLUSION

PrabotulinumtoxinA could effectively ameliorate MMH without major complications.

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.

Analysis of Sexual Dimorphic Features of the Jawline and Chin in White Celebrity Faces

BACKGROUND

The jawline greatly influences facial shape and contributes to facial dimorphism. Analysis of lower facial shape and sexual dimorphic differences in contemporary attractive white faces can advance the goals of lower facial aesthetics and facial gender-affirming surgery (FGAS).

METHODS

Full-face, front-view photos of 47 white female and 21 white male celebrities were included from a list generated using GQ magazine's Highest Paid Models issue, People Magazine's Beautiful issue (1991-2022), and celebrities featured on lifestyle websites. Facial landmarks were detected through a facial analysis program using Vision framework and MATLAB. After converting pixel distances to absolute distances, lower face measurements were compared between males and females.

RESULTS

The mean lower facial height was 6.08 cm in females and 7.00 cm in males ( P value<0.001). The mean bigonial width was 11.21 cm in females and 12.30 cm in males ( P value<0.001). The ratio of facial height to lower facial height was 2.98 in females and 2.76 in males ( P value<0.001), signifying that symmetry in facial thirds is more prevalent in attractive female faces, while a longer lower face is more common in attractive male faces. The greatest differences in female and male facial contours were at gonial angles and chin.

CONCLUSIONS

Analysis of contemporary white celebrity faces demonstrated significantly wider and longer lower facial measurements in males. The overall contour of the female lower face was more tapered at the gonial angles and chin compared to males. These results are important when planning lower facial rejuvenation or FGAS, as lower face size and proportions influence perceived gender and attractiveness.

The Volumetric Effect of Botulinum Toxin Type A Injection on the Parotid Gland: A Randomized Controlled Trial

BACKGROUND

Botulinum neurotoxin type A (BTX-A) to the masseter muscle is a useful tool for the aesthetic narrowing of the width of the lower face. The administration of BTX-A to visible parotid glands is also effective to reduce lower facial width. However, no studies have quantitatively analyzed the effect of BTX-A on the parotid glands.

METHODS

The purpose of this study was to confirm the impact of BTX-A injection on the parotid gland and to suggest the effective dosage of BTX-A in facial slimming. This study was conducted by selecting patients who desired facial slimming from among patients who required surgery for a facial bone fracture. Patients undergoing BTX-A injection were randomized to high-dose, low-dose, and placebo groups, and different doses of BTX-A for each group were injected into both parotid glands during facial bone surgery.

RESULTS

A total of 30 patients were enrolled in this study. Ten patients in the high-dose group, eight in the low-dose group, and nine in the control group completed the clinical trial. There were significant changes in both the high- and low-dose groups compared with the control group ( P < 0.001, P < 0.001), and in interaction of time and group ( P < 0.001). Volume recovery after 3 months was found in 7.6% in the high-dose group and in 4.8% in the low-dose group.

CONCLUSION

BTX-A injection into parotid glands can be an effective treatment option in managing salivary gland enlargement for lower face contouring.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Achieving the Attractive Asian Midface Profile with Hyaluronic Acid-Based Fillers

Despite different ethnic origins among Asians, midface enhancement is the most frequent noninvasive procedure for hyaluronic acid injection either as a stand-alone treatment or as part of the pan-facial beautification strategy. Because Asians often have an aesthetically undesirable wide, flat, and short face, improving the projection of midface and midline facial structures is an indispensable aesthetic procedure in creating a smaller facial appearance with better three-dimensionality. Achieving an oval facial shape together with increased facial height is also required in most circumstances for a natural and balanced result.

Treatment of Facial Flaccidity and Sagging after Botulinum Toxin A Injection into the Masseter

BACKGROUND

Botulinum toxin A injection for masseter reduction is generally considered minimally invasive, safe, and effective. However, this approach may lead to facial flaccidity and sagging, especially in older patients with reduced elasticity of the skin and the soft tissue.

METHODS

The authors analyzed 27 cases of patients who presented with the above complications and treated them with botulinum toxin A injections into the platysma and the depressor anguli oris muscle. The efficacy of treatment was evaluated by both patients and physicians.

RESULTS

Ninety-six percent of patients were satisfied with the treatment outcome. One patient considered the treatment outcome unsatisfactory because of the lack of significant improvement in nasolabial folds. Physician evaluation suggests significant improvement in all patients, including the one who considered the treatment outcome unsatisfactory.

CONCLUSION

Botulinum toxin A injection into the platysma and the depressor anguli oris muscles is a safe, convenient, and effect treatment to correct the complication of facial flaccidity and sagging after masseter reduction.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Botulinum Toxin Injection for Masseteric Hypertrophy Using 6 Point Injection Technique - A Case Report. Proposal of a Clinical Technique to Quantify Prognosis

Introduction

Masseter hypertrophy presents as unilateral or bilateral swellings over the ramus and angle of the mandible. It is caused by malocclusion, clenching, TMJ disorders, etc and alters facial symmetry, leading to discomfort and negative cosmetic impact in many patients, making this a popular request for aesthetic and functional correction.

Materials and Methods

This case report involves injecting Botulinum toxin into 6 equidistant bulging points on the masseter. Standardized photography and clinical parameters were used to assess facial contour and masseter muscle thickness at baseline and successive follow ups.

Results and Discussion

Significant masseteric bulk reduction was observed in subsequent follow ups.

Conclusion

The 6-point technique was found to be an effective treatment modality for Botox injection in masseteric hypertrophy. The clinical method to quantify prognosis was easy and economical.

Ultrasonographic observation of the masseter muscle after injection of different botulinum toxin type A

BACKGROUND

Botulinum toxin type A (BoNT-A) injection is a popular cosmetic procedure in East Asian countries, and there are multiple types of toxins on the market. Whether different toxin types induce different changes in the masseter has not been studied.

OBJECTIVE

We aimed to investigate and compare the changes induced by injection of different types of BoNT-A in the masseter.

METHODS

Upon retrospective review of clinical records and routine ultrasound examination results of patients who underwent BoNT-A injection, four groups were set for comparison: unapproved toxin, OnabotulinumtoxinA, LanbotulinumtoxinA, and non-injected. Clinical records and ultrasound images were collected. Ultrasound images were taken in both horizontal and coronal planes. Elasticity of the masseter muscle was also investigated by measuring the surface wave speed.

RESULTS

A total of 24 patients were included (six patients per group). All patients were young females. For the non-injected group, the deep inferior tendon was clear and the muscle bundles were arranged, with little fibrous content. Patients who received unapproved toxin injection showed highly disarranged muscle and fiber bundles, with much fiber content present. The changes in OnabotulinumtoxinA and LanbotulinumtoxinA groups were in between those in the non-injected and unapproved toxin groups. Muscle rigidity was the highest in the unapproved toxin group, and generally higher in injected groups compared with the non-injected group.

CONCLUSION

Different types of BoNT-A may induce different changes in the masseter.

Botulinum toxin A in dentistry and orofacial surgery: an evidence-based review - part 2: cosmetic applications

Objective An evidence-based review on the role of botulinum toxin type A (BoNTA) on diverse cosmetic applications of interest to dental practitioners and allied specialities. In this context, to identify the cosmetic treatments that have an evidence-based rationale against areas requiring further research, with a view to assess the safety and efficacy of BoNTA.Data source and selection A comprehensive search was conducted using Cochrane Library of Systematic Reviews, Cochrane Central Register of Controlled Trials, and PubMed (Medline) electronic databases. Thirty-nine studies of variable quality were included. The Best Evidence Topics (BETs) Critical Appraisal Tool was used to facilitate the quality assessment of relevant studies.Data extraction Based on current level II evidence, BoNTA was safe and effective to improve facial contour, reduce volume and thickness of bilateral hypertrophic masseter. Conservative doses using a combined approach of BoNTA and hyaluronic acid was recommended as a safe and effective treatment for perioral enhancement supported by level II evidence. There was limited evidence, not higher than level III, to support BoNTA effectiveness for gummy smile associated to perioral musculature hyperactivity, while jawline sculpting targeting the platysma muscle had lower level IV evidence up to this date.Conclusion BoNTA has been widely used off-label for the investigated cosmetic orofacial conditions, with reports of 'good patient and practitioner satisfaction'. However, there is limited high-quality evidence to support the long-term safety and effectiveness of repetitive BoNTA injections. Additionally, no studies were found that provided a cost-effectiveness evaluation of BoNTA formulations against other current cosmetic interventions. Well-designed clinical trials, including long-term follow-up, would help to provide robust evidence-based recommendations for clinical practice, supporting BoNTA popularity, independently or in a combined approach.

Can Botulinum Toxin-A Contribute to Reconstructing the Physiological Homeostasis of the Masticatory Complex in Short-Faced Patients during Occlusal Therapy? A Prospective Pilot Study

The physiological homeostasis of the masticatory complex in short-faced patients is too robust to be disintegrated and reconstructed due to the powerful masseter muscle. This study innovatively introduced the botulinum toxin-A (BTX-A) into the field of dental occlusal treatment, providing a novel and minimally invasive therapy perspective for the two major clinical problems in these patients (low treatment efficiency and high rates of complications). In total, 10 adult patients with skeletal low angle seeking occlusal treatment (age: 27.0 ± 6.1 years; 4 males and 6 females) were administered 30−50 U of BTX-A in each masseter muscle and evaluated before and 3 months after injection based on cone-beam computed tomography (CBCT). We found a significant reduction in the thickness of the masseter muscle (MMT) (p < 0.0001). With regards to occlusion, we found a significant increase in the height of the maxillary second molar (U7-PP) (p < 0.05) with significantly flattened occlusal curves (the curve of Spee [COS] (p < 0.01), and the curve of Wilson [COW] (p < 0.05)). Furthermore, the variations in the temporomandibular joint exhibited a significant reduction in the anterior joint space (AJS) (p < 0.05) and superior joint space (SJS) (p < 0.05). In addition, the correlation analysis of the masticatory complex provided the basis for the following multiple regression equation: MMT = 10.08 − 0.11 COW + 2.73 AJS. The findings from our pilot study indicate that BTX-A, as a new adjuvant treatment attempt of occlusal therapy for short-faced patients, can provide a more favorable muscular environment for subsequent occlusal therapy through the adjustment of the biting force and may contribute to the reconstruction of healthier homeostasis of the masticatory complex. However, further research is required to establish the reliability and validity of these findings.

Efficacy of botulinum toxin in masseter muscle hypertrophy for lower face contouring

BACKGROUND

Masseter muscle hypertrophy (MMH) usually presents with cosmetic concerns as it may lead to widening of the lower face. Apart from the traditional surgical approaches, botulinum toxin type A (BTA) injection is a non-invasive treatment option available. There are no standard guidelines for this procedure.

OBJECTIVES

To study the efficacy of botulinumtoxin A in MMH for lower face contouring.

METHODOLOGY

The Cochrane Library, PubMed/MEDLINE, Google-scholar, Science-Direct database, and ResearchGate from inception until September 2021 were searched using the keywords "botulinumtoxin type A," "masseter muscle hypertrophy," "lower face contouring," and "masseter botox." All available retrospective and prospective studies, case-series, case-reports, and expert reviews were included with an emphasis on efficacy of BTA in MMH and units injected into the muscle, points of placement, adverse events, and the duration of its effect. Reference lists of the resultant articles, as well as relevant reviews, were also searched.

RESULT

40 articles were shortlisted for the review, of which 14 studies with sample-size ≥10 in accordance with the study requirements were summarized in a tabular form for analysis and easy comparison and reference.

CONCLUSION

BTA injection is a non-invasive, safe, and effective treatment for MMH. The optimum number of BTA units could not be ascertained due to wide variability in the studies as well as ethnicity of patients and extent or some measurement of MMH. The points of placement of injection should be well within the boundaries of the masseter muscle. The maximum effect of BTA after a single injection session is usually seen in ~3 months, and the duration may last for 6-12 months. Multiple injection sessions may be required to maintain a long-term effect. Injection technique and total number of injection units of neuromodulator must be individualized for each patient.

Long-term Effects of Repeated Botulinum Toxin Injection in Cosmetic Therapeutics

BACKGROUND

Botulinum toxin (BT), a potent neurotoxin, has been used in clinical medicine since the 1970s for cosmetic and therapeutic purposes. Studies have consistently shown positive outcomes with a very limited adverse effect profile and a conventional understanding that results dissipate after 3 to 5 months. However, more recent evidence suggests that changes in muscle composition, function, and appearance persist for much longer, even years. To examine the potential implications of these findings on cosmetic use of BT injections in reduction of skin lines and wrinkles, we first needed to further our understanding of the current literature on long-term outcomes after repeated BT injections.

METHODS

A comprehensive review of the literature on long-term outcomes after repeated BT injections for cosmetic indications was performed. We evaluated the study designs, and results were compared.

RESULTS

A total of 22 publications met our inclusion criteria, of which 14 were clinical trials. Few studies extended outcome measurement past 6 months postinjection, and many were funded or supported by industry. However, the studies that extended follow-up saw persistent changes after BT injection, in some cases as far as 4 years postinjection.

CONCLUSION

The current body of knowledge on the long-term results after repeated cosmetic BT injections is very limited, and the available literature provides insufficient evidence on how prolonged effects could alter clinical use of BT. Further clinical studies with extended follow-up periods with inclusion of both subjective and objective measured outcomes of appearance and muscle function are required to better understand the long-term impacts of repeated BT injections.

The "Visible" Muscles on Ultrasound Imaging Make Botulinum Toxin Injection More Precise: A Systematic Review

BACKGROUND

Botulinum toxin (BoNT) injection is the most commonly performed procedure in cosmetic surgery. However, blind injection is unable to take individual anatomical variations into consideration, which is the main contributing factor to complications. Ultrasound (US) imaging was introduced to reduce complications and improve effects. This article will review uses of US in aesthetic BoNT injection.

METHOD

A systematic electronic search was performed using the PubMed, MEDLINE, Web of science. Search terms were set to focus on aesthetic BoNT injection. Two independent reviewers subsequently reviewed the resultant articles based on strict inclusion and exclusion criteria. Selected manuscripts were analysed and grouped by procedure categories. Clinical cases were all performed by one plastic surgeon in our department.

RESULTS

The search finally retained 24 articles. Five procedural categories were identified, including masseter (n = 16), frontalis (n = 2), glabella complex (n = 2), trapezius (n=1), and gastrocnemius (n = 3). US imaging is practical and instructive for pre-operative assessments as in needle-type selection, injection point localization and depth setting, as well as post-operative follow-ups regarding injection feedback (for instance, the extent of muscle volume decreases). What's more, ultrasound-guided injection makes needle trajectory visualized so as for the needle to reach the target muscle in avoidance of potential damage to neurovascular bundle, gland or adjacent muscle.

CONCLUSION

Muscles, such as masseter, frontalis, glabella complex, trapezius and gastrocnemius, and their adjacent structures can be well visualized using US, and as such, US can be a useful tool for a variety of pre-operative, intra-operative and post-operative procedures.

LEVEL OF EVIDENCE IV

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 .

Tips and Tricks for Facial Toxin Injections with Illustrated Anatomy

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Recognize facial muscle contraction direction and muscle morphology based on skin surface movements and facial rhytides. 2. Classify different muscle contraction patterns and target respectively with the recommended dosage and injection technique. 3. Apply the presented injection techniques to the patients' individual anatomy with greater precision and without affecting adjacent muscles or causing other adverse events.

SUMMARY

Facial muscular anatomy has recently gained increased attention, with new investigative methodologies and new injection techniques arising on the market. These recent advancements have increased our understanding about the functional anatomy of facial muscles and have changed the way health care professionals see and understand their interplay during various facial expressions and in determining facial shape. This new anatomical understanding of facial muscles and their interaction has resulted in superior neuromodulator treatment outcomes with fewer side effects and with increased precision. The latter is of greatest importance, as all facial muscles act as a unit and connect with each other. It is therefore paramount to target during neuromodulator treatments only the muscle responsible for the aesthetic effect desired and not other adjacent muscles, which can have different or even antagonistic effects. Conventional anatomy was previously limited to two-dimensional explanations of muscle locations without incorporating their detailed action or their three-dimensional location of extent. The "new" anatomy incorporates those novel concepts and, once understood, will help health care providers to understand better and to "read" the underlying muscular anatomy based on the wrinkle status and based on the change in skin surface landmarks based on the actions of the underlying musculature. The following article summarizes tips and tricks, pearls and pitfalls, and dos and don'ts during facial neuromodulator injections along with a guide toward adverse event management and patient outcome assessment with special focus on the underlying anatomy.

Pivotal role of injection volume on sunken cheek prevention in masseter muscle BoNT-A injection: A cadaver study

BACKGROUND

Botulinum neurotoxin A injection is a popular noninvasive alternative for the treatment of masseter hypertrophy. This study was conducted to identify a safe injection volume to avoid sunken lateral cheek after botulinum neurotoxin A injection in the masseter muscle.

METHODS

One milliliter or 0.5 ml of indocyanine green was randomly injected into either side of the masseter muscles of 18 fresh cadaver heads. The bilateral spreads of indocyanine green within the masseter were observed by a fluorescence imager. The masseters were then dissected, and the spreading distance was measured.

RESULTS

Dye spreading showed an oval shape parallel to the long axis of the masseter muscle. The lower edges of the masseters were all stained with indocyanine green. The upward spreading exceeded the mouth corner-tragus line in 94.44% (17/18) of the masseters on the 1-ml side, and 11.11% (2/18) of the masseters on the 0.5-ml side. The spreading area and upward spreading distance on the 1-ml side (9.95 ± 0.48 cm² , 3.18 ± 0.31 cm) were significantly larger than the 0.5-ml side (7.13 ± 0.80 cm² , 2.08 ± 0.32 cm).

CONCLUSIONS

The spread of indocyanine green within the masseter occurs in direct proportion to its volume. A bolus of 1 ml easily exceeded the mouth corner-tragus line and cause sunken cheek.

The Effect of Orthognathic Surgery on Changes in Masticatory Muscle Volume in Patients With Facial Asymmetry

ABSTRACT

The masseter muscle changes remarkably with orthognathic surgery and has a marked influence on the contours of the lower face. If the postoperative volume change of masticatory muscles, including the masseter muscles, can be predicted, it will facilitate preoperative planning and outcome prediction. This study investigated the association of masticatory muscle volume according to the presence or absence of facial asymmetry, and evaluated whether the volume of masticatory muscles, including that of the masseter muscle, changes after orthognathic surgery in facial asymmetry patients.Twenty patients who underwent LeFort I osteotomy and bilateral sagittal segmentation ramus osteotomy (BSSRO) with facial asymmetry between 2011 and 2017 were assigned to the asymmetric group. Additionally, 207 patients with a simple nasal fracture between 2016 and 2019 were included as the common group. Three-dimensional computed tomography images were retrospectively analyzed and compared between the asymmetric group and common group.The volume of both temporal and masseter muscles differed according to facial asymmetry, with the asymmetry in the muscle volume increasing in proportion to the degree of facial asymmetry. The difference in masseter volume on the shortened and lengthened sides was significantly reduced after orthognathic surgery, but a difference of about 1 cm3 remained. Additionally, the masticatory muscle volume on the lengthened side tended to be decreased more than that on the shortened side.Consideration of the postoperative change in the volume of the masticatory muscles may be helpful in planning orthognathic surgery in facial asymmetry patients.

Efficacy and safety of botulinum toxin injection in reducing deltoid muscle hypertrophy

With the increasing demand for body contouring, botulinum toxin (BTX) injection is being widely used off-label for muscular hypertrophy. However, to the best of our knowledge, no study has investigated the clinical efficacy of BTX type A (BTX-A) in deltoid muscle hypertrophy. This study was conducted to evaluate the efficacy and safety of intramuscular injection of BTX in reducing deltoid muscle hypertrophy. Overall, 10 patients with bilateral deltoid muscle hypertrophy were treated with an intramuscular injection of prabotulinum toxin A, with a total of 50 units [U] administered per patient. As measured by ultrasonography, the thickness of the deltoid muscles was significantly decreased at weeks 2 and 12. In addition, the clinical assessment score by blinded investigators was improved after the treatment; however, patients' satisfaction scores were relatively low. No major complications were reported. Therefore, intramuscular injection of BTX-A seems to be a candidate for novel treatment option for deltoid muscle hypertrophy. Further larger clinical studies are warranted to confirm the efficacy of BTX-A.

Surgical Versus Nonsurgical Lower Face Contouring: Layperson Perceptions of Attractiveness and Personality Traits

BACKGROUND

Traditional approaches to lower face contouring involve ostectomy of the mandibular angle or body. More recently, nonsurgical techniques have gained popularity, including neurotoxin injection to the masseter muscle. This study aims to evaluate layperson perceptions of patient attractiveness and personality traits following lower face contouring using either surgical or nonsurgical treatment.

METHODS

In this survey study distributed via Amazon's Mechanical Turk, respondents viewed a series of 14 patient images obtained in clinic before and after surgical or nonsurgical jawline slimming, or without any facial aesthetic procedure. Respondents rated changes in attractiveness and personality trait scores between the before and after image (score: -50 to 50, with 50 representing the greatest posttreatment increase and 0 representing no change). We used descriptive statistics and multivariable regression to determine differences in respondent ratings between patient images.

RESULTS

A total of 415 respondents (mean age 38 years, 50.6% female) successfully completed the survey. Compared to patients who underwent nonsurgical treatment, those who received surgery had significantly greater increases in perceived attractiveness (P < 0.001), femininity (P < 0.001), friendliness (P < 0.001), intelligence (P < 0.001), trustworthiness (P < 0.001), financial wealthiness (P < 0.001), dominance (P < 0.01), and self-esteem (P < 0.001). Gonial angles increased and jaw widths decreased following both surgical and nonsurgical intervention, with no statistically significant difference between treatment groups.

CONCLUSIONS

From the layperson perspective, surgical compared to nonsurgical jawline contouring offers greater improvements in perceptions of attractiveness and favorable personality traits.

A Cadaveric Study of Dye Spreading: Determining the Ideal Injection Pattern for Masseter Hypertrophy

BACKGROUND

Masseter hypertrophy is the main cause of an asymmetrical and squared lower facial contour in the Asian community. Botulinum toxin injection technique is crucial to treat this condition.

OBJECTIVE

To improve injection techniques for masseter hypertrophy by elucidating the distribution of the injections within the masseter.

METHODS

Thirty masseter muscles were divided into 6 groups of 5 muscles each. Each group received one 0.2- or 0.3-mL injection at Point A, B, or C according to a three-point technique. Muscle dimensions and dye of the primary and secondary dye spreading were measured.

RESULTS

The average muscle length, width, and thickness were 69.87, 33.50, and 11.23 mm, respectively. The average primary longitudinal and horizontal spreading was 36.56 and 15.60 mm, respectively. No statistically significant difference was found between 0.2- and 0.3-mL injections at each point.

CONCLUSION

The three-point technique best fits in the safe zone and should be the standard injection technique for masseter hypertrophy. Injection at Points B and C may create secondary spreading that affect the risorius muscle and the parotid gland which are the cause of asymmetrical smiling and xerostomia, respectively. The dosage should be adjusted according to the muscle volume and not only the thickness.

Botulinum toxin type A injections for masticatory muscles hypertrophy: A systematic review

The aim of this study is to compare the efficacy of single-point injection of botulinum toxin A versus multi-point operative protocols found in the literature in reducing hypertrophy in patients with masticatory muscle hypertrophy. A systematic review was performed in accordance with the Park et al., 2018 guidelines, selecting articles from PubMed, Google Scholar, Web of Science and Ovid databases up to July 8, 2020.28 studies met the eligibility criteria. 748 patients were treated for masseter hypertrophy (MH) and 4 patients for temporal muscle hypertrophy. As for MH: in 45.2% of cases 3 injection sites (IS) were used, in 18.8% 1 IS, in 16.2% 2 IS, in 13% 5 IS, in 4.1% 6 IS, 2.7% 4 IS. At three months, the mean reduction in masseter muscle thickness is 26-31% when 1 IS was used, 28% in 2 IS, 12-27% in 3 IS and 22-30% in 6 IS. Heterogeneity of results, high bias level and selective reports led to a difficult efficacy comparison of the injection techniques described. Data suggest that the lowest number of IS possible should be used until stronger evidences are presented. Homogeneity in pre- and post-operative protocols is needed to establish a reliable setting for the condition under study.

High Superficial Musculoaponeurotic System Lamellar Facelift Under Local Anesthesia

PURPOSE

Patients, nowadays, prefer easy, low-risk, day-case procedures under local anesthesia for facial rejuvenation. Therefore, they favor facelift operations applied under local anesthesia.

MATERIALS AND METHODS

A total of 160 patients who underwent high superficial musculoaponeurotic system (SMAS) lamellar facelift under local anesthesia between 2010 and 2020 were included in this study. Patients operated under general anesthesia were excluded from this study. High SMAS lamellar facelift under local anesthesia was performed in all patients, consisting of 145 women and 15 men without any additional disease aged between 38 and 65 years. About 140 of these patients underwent primary facelift, whereas 20 of them had undergone SMAS plication more than 10 years ago. Lidocaine was used as a local anesthetic and the patients were not sedated. The duration of the operation was 80 minutes on average. The patients were left to rest for 1 hour after the operation and then sent home until their follow-up every other day for the first week.

RESULTS

This study shows that high SMAS facelift operations for the mid-face can easily be performed under local anesthesia under operating room conditions without sedation. However, an important point to keep in mind is that although the results of this surgery satisfy the patients, the outcomes do not entirely match the expectations from total face and neck lift performed under general anesthesia. High SMAS facelift with local anesthesia should be considered as an alternative for patients who do not want to undergo general anesthesia or who are at risk of undergoing general anesthesia. Especially during the COVID-19 pandemic, local anesthesia was considered much safer for the patients.Level of evidence: Level V.

Biphasic Injection for Masseter Muscle Reduction with Botulinum Toxin

Masseter Muscle Hypertrophy (MMH) is a well-known clinical benign condition that is not gender-specific and it can be monolateral or bilateral. Botulinum Toxin type A (BoNTA) injection has been widely described for MMH treatment and non-surgical facial slimming. BoNTA masseter injections have high efficacy and safety profile, but the risks of side effects remain. Muscular bulging during mastication is a complication due to the superficial overcompensation of masseteric fibers in response to neurotoxic weakening of the deep masseter. We present a biphasic-injection technique for BoNTA administration, based following anatomical concept and developed in order to prevent paradoxical bulging. A total of 98 treatments from 2015 to 2020 were performed with this technique. No remarkable complications occurred in our study. No cases of loss of full smile, difficulty in mouth opening, dizziness, headache, neurapraxia, and xerostomia were reported. A case of asymmetric smiling was self-resolved within a week. No patient claimed transient muscle weakness as distressing. No cases of paradoxical bulging were observed. Extensive knowledge of muscular anatomy and appropriate injection technique are key factors in achieving the desired result and avoiding complications. We feel that sharing this tip could be helpful for all the physicians involved in MMH treatment with BoNTA.

Autogenous Fat Transplantation and Botulinum Toxin Injection Into the Masseter Muscle to Create an Ideal Oval Face

BACKGROUND

East Asian faces vary in shape but only oval faces seem to be considered attractive. Many patients with wide faces seek removal of part of the mandibular angle and/or zygoma to achieve an ideal facial contour, but the procedure is high risk and the recovery period is relatively protracted.

OBJECTIVES

We sought to achieve ideal facial contours through the use of autologous fat grafting (AFG) combined with masseter botulinum toxin (BTX) injection for patients with wide faces and masseter hypertrophy.

METHODS

Fourteen patients with wide faces underwent AFG of the forehead, temporal region, cheeks, zygomatic body, nose, nasolabial fold, tear trough, and chin; and BTX injection into the masseter muscles. Each patient was photographed more than 6 months after the operation. The pre- and postoperative ratios pertaining to the facial aesthetics of the face were calculated. The Hollowness Severity Rating Scale (HSRS) and Ricketts's E-line were used to evaluate the photographs. Patient satisfaction was also investigated.

RESULTS

All patients received AFG and 1 to 3 BTX injections. The face length:bizygomatic breadth, bigonial breadth:bizygomatic breadth, and lower-face height:middle-face height ratios improved greatly after treatment. The mean HSRS score decreased from 2.214 preoperatively to 1.071 postoperatively. The chin and nose became more prominent than before. Facial swelling persisted for an average of 11.929 days. All patients were satisfied with the treatment outcome.

CONCLUSIONS

A combination of AFG and BTX injection was able to achieve an ideal oval face in East Asian patients with wide faces and masseter hypertrophy, with very few complications. Recovery was rapid and patient satisfaction was high.

LEVEL OF EVIDENCE: 4

Comparison between Conventional Blind Injections and Ultrasound-Guided Injections of Botulinum Toxin Type A into the Masseter: A Clinical Trial

The aim of the study was to propose a more efficient and safer botulinum toxin type A (BoNT-A) injection method for the masseter by comparing the conventional blind injection and a novel ultrasonography (US)-guided injection technique in a clinical trial. The 40 masseters from 20 healthy young Korean volunteers (10 males and 10 females with a mean age of 25.6 years) were included in this prospective clinical trial. The BoNT-A (24 U) was injected into the masseter of each volunteer using the conventional blind and US-guided injection techniques on the left and right sides, respectively, and analyzed by US and three-dimensional (3D) facial scanning. One case of PMB (paradoxical masseteric bulging) was observed on the side where a conventional blind injection was performed, which disappeared after the compensational injection. The reduction in the thickness of the masseter in the resting state differed significantly at 1 month after the injection between the conventional blind injection group and the US-guided injection group by 12.38 ± 7.59% and 17.98 ± 9.65%, respectively (t(19) = 3.059, p = 0.007). The reduction in the facial contour also differed significantly at 1 month after the injection between the conventional blind injection group and the US-guided injection group by 1.95 ± 0.74 mm and 2.22 ± 0.84 mm, respectively (t(19) = 2.908, p = 0.009). The results of the study showed that the US-guided injection method that considers the deep inferior tendon by visualizing the masseter can prevent the PMB that can occur during a blind injection, and is also more effective.