Effect of the masseter muscle injection of botulinum toxin A on the mandibular bone growth of developmental rats

Botulinum toxin: a new differential diagnosis for a lytic bone lesion

BACKGROUND

Botulinum toxin, produced by the Gram-positive anaerobe Clostridium botulinum, is composed of seven antigenic subtypes (A, B, C, D, E, F, and G). Currently, only Botulinum toxin type A, commonly referred to as "Botox," is approved for clinical use, given its relatively safe clinical profile. Botulinum toxin type A has a wide range of therapeutic indications, including treatment for dystonia, migraine headache, neurogenic bladder, and large muscle spastic disorders. However, the toxin is most widely known for its cosmetic effects in treating wrinkles and facial lines.

CASE PRESENTATION

This article describes a 62-year-old Caucasian female who presented for investigation and workup of an isolated lytic lesion of her frontal bone a few weeks after administration of botulinum toxin injection into the corresponding site in the frontalis muscle. This presented as a large, palpable, painless forehead lump causing significant psychological distress. After no neoplastic cause for the lesion was found and histopathology was performed, our researchers concluded that the most likely explanation was that the bony lytic lesion resulted from inadvertent injection of the "Botox" neurotoxin through the intended target muscle and into the cortex of the underlying bone.

CONCLUSIONS

Our search of the literature failed to identify any previous cases of this occurring. However, as the popularity of this cosmetic procedure only increases, we believe that this represents an important possible differential for isolated lytic lesion after administration of "Botox" injection.

Unilateral injection of botulinum toxin type A into the masseter muscle induces mandibular asymmetry in adolescent rats by suppressing the angular process growth

INTRODUCTION

Mandibular asymmetry has negative impacts on maxillofacial aesthetics and psychological well-being. This study investigated the effects of unilateral injection of botulinum toxin type A (BTX-A) into the masseter muscle on mandibular symmetry.

METHODS

Forty Wistar rats (4-week-old) were divided into 4 groups (n = 10): control, group 1 (1U BTX-A), group 2 (3U BTX-A), and group 3 (1U BTX-A for 3 times). BTX-A was injected into the right masseter of treatment groups. Cone-beam computerized tomography scans were taken before the injection and then at 2 weeks, 4 weeks, and 6 weeks after injection. Histologic and immunohistochemical staining were done for the condylar cartilage. RNA sequencing and quantitative reverse transcription polymerase chain reaction were used to detect gene expression in the angular process.

RESULTS

In Groups 2 and 3, the right angular process length and the ramus height were reduced 4 weeks after injection, resulting in the mandibular midline deviating to the right side; the right condylar cartilage had reduced thickness and decreased expression of RUNX2, SOX9, and COL II (P <0.05). Two hundred sixty-one genes were differentially expressed (256 downregulated) in the angular process at 3 days post-BTX-A injection, and the calcium signaling pathway was unveiled through the Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis. Furthermore, TRPC1, Wnt5a, CaMKII, Ctnnb1, and RUNX2 expression were significantly downregulated at 1 and 3 days postinjection.

CONCLUSIONS

Unilateral injection of BTX-A into the masseter muscle in adolescent rats induces mandibular asymmetry by suppressing the angular process growth on the injected side.

Effect of the Correction of Bilateral Differences in Masseter Muscle Functional Pressure on the Mandible of Growing Rats

The objective of this study is to clarify the effect of restoring the lowered masticatory muscle functional pressure and correcting bilateral differences in masticatory muscle functional pressure on jawbone growth during growth and development with a quantitative evaluation of the changes in the micro/nanostructural characteristics of entheses. Male Wistar rats aged 4 weeks were divided into an experimental group injected with a botulinum toxin serotype A (BoNT/A) formulation to reduce muscle function (BTX group) and a control group (CTRL group). They were euthanised after 6, 8, 10, 12, and 16 weeks after measuring the difference between the midline of the upper and lower incisors. The mandibles were harvested for histological examination, second harmonic generation imaging, and the quantitative evaluation of biological apatite (BAp) crystal alignment. The midline difference decreased with age in weeks. In rats from 6 weeks after BoNT/A administration to 12 weeks after administration, the collagen fibre bundle diameter was significantly smaller in the BTX group; the difference between the two groups decreased with increasing age. BAp crystal alignment was significantly different on the x-axis and the y-axis on the BTX group from 6 weeks after BoNT/A administration to 10 weeks after administration. Asymmetry of mandibular bone formation caused by load imbalance during growth could be corrected by the adjustment of the function of the masseter muscle on either side.

The perioral muscle continuum affects premaxillary development in Wistar rats

Craniofacial deformities involve soft tissue and skeletal abnormalities. Facial bone growth is based on congenital defects and iatrogenic factors, in which muscle activity is important. Understanding the effects of muscle function on facial bone growth may help us in clinical treatment. Although there have been some studies, fewer have focused on the effects of perioral muscle continuity on maxillary development, which needs further research. In our study, mimic perioral muscle surgeries were performed in twenty 3-day Wistar rats, which were divided into four equal groups, including five untreated rats as control (Ctrl), five rats by unilateral perioral muscle incision (MI), five rats by unilateral perioral muscle incision combined with muscle stripping (MIMS) and five rats treated by unilateral perioral muscle incision combined with periosteal stripping (MIPS). After six weeks, skulls were imaged and measured by micro-CT scan and hematoxylin-eosin staining. Differences in the rats' premaxilla were analyzed with self-contrasted and group-control studies. Compared with Ctrl group, there were significant premaxillary developmental defects in the affected side of the rats in all three surgical groups. In the affected side, both the width and the length of the premaxilla were less than the unaffected side, particularly in MIMS and MIPS groups. Group-control study showed that the ratio of premaxillary length of affected side to unaffected side had significant differences between MI and MIMS. The conclusion was that complete perioral muscle continuity with intact muscle attachment on the premaxilla is the driving force for the premaxillary development.

Influence of botulinum toxin A on craniofacial morphology after injection into the right masseter muscle of dystrophin deficient (mdx-) mice

BACKGROUND

Severe craniofacial and dental abnormalities, typical for patients with progressive Duchenne muscular dystrophy (DMD), are an exellcent demonstration of Melvin L. Moss "functional matrix theory", highlighting the influence of muscle tissue on craniofacial growth and morphology. However, the currently best approved animal model for investigation of this interplay is the mdx-mouse, which offers only a limited time window for research, due to the ability of muscle regeneration, in contrast to the human course of the disease. The aim of this study was to evaluate craniofacial morphology after BTX-A induced muscle paralysis in C57Bl- and mdx-mice, to prove the suitability of BTX-A intervention to inhibit muscle regeneration in mdx-mice and thus, mimicking the human course of the DMD disease.

METHODS

Paralysis of the right masseter muscle was induced in 100 days old C57Bl- and mdx-mice by a single specific intramuscular BTX-A injection. Mice skulls were obtained at 21 days and 42 days after BTX-A injection and 3D radiological evaluation was performed in order to measure various craniofacial dimensions in the sagittal, transversal and vertical plane. Statstical analysis were performed using SigmaStat®Version 3.5. In case of normal distribution, unpaired t-test and otherwise the Mann-Whitney-U test was applied. A statistical significance was given in case of p ≤ 0.05.

RESULTS

In contrast to C57Bl-mice, in mdx-mice, three weeks after BTX-A treatment a significant decrease of skull dimensions was noted in most of the measurements followed by a significant increase at the second investigation period.

CONCLUSIONS

BTX-A can induce changes in craniofacial morphology and presumably partially inhibit muscle regeneration in mdx-mice, but cannot completely intensify craniofacial effects elicited by dystrophy. Further research is necessary in order to fully understand muscle-bone interplay after BTX-A injection into dystrophic muscles.

Obvious morphologic changes in the mandible and condylar cartilage after triple botulinum toxin injections into the bilateral masseter

INTRODUCTION

Nonsurgical treatments that can prevent or reduce the extent of the mandibular excess at an early stage are desirable. A single botulinum toxin (BTX) injection into the unilateral and bilateral masseter can regulate mandibular contour and condylar cartilage. However, BTX injection is frequency dependent when used in facelifts. This study aimed to evaluate the effect of BTX injection into the bilateral masseter at different frequencies on the mandibular contour and condylar cartilage.

METHODS

In the present study, 24 female Sprague Dawley rats (4 weeks old) were divided into 3 groups: control, single injection, and triple injection. Contour measurement of the mandible was carried out by radiographic imaging. Microcomputerized tomography was performed to determine the change in bone volume in the subchondral bone. Hematoxylin and eosin staining was used to observe the morphologic changes of condylar cartilage. Immunohistochemistry was performed to detect the expression level of biomechanically sensitive factors, including transforming growth factor-β1, parathyroid hormone-related protein, SRY-box 9, and type II collagen.

RESULTS

Bone volume and/or total volume, trabecular number, and trabecular thickness of the mineralized cartilage and subchondral bone significantly decreased in the triple injection group when compared with the single injection group. Mandibular contour also diminished after increased BTX injection frequencies. Chondrocyte proliferation ability and the expression levels of transforming growth factor-β1, parathyroid hormone-related protein, SRY-box 9, and type II collagen significantly decreased in all BTX injection groups and more in the triple injection group.

CONCLUSIONS

Morphologic changes of the mandible and condylar cartilage become more obvious after increased BTX injection frequencies, suggesting that multiple BTX injections into the masseter of patients may relieve the severity of mandibular deformity at an early stage.

Classification of the journal category "oral surgery" in the Scopus and the Science Citation Index Expanded: flaws and suggestions

Objectives

The aim of this study was to evaluate the journal category “oral surgery” in Scopus and in the Science Citation Index Expanded (SCIE).

Materials and Methods

The Journal of Oral and Maxillofacial Surgery (JOMS), The Journal of the Korean Association of Oral and Maxillofacial Surgeons (JKAOMS), and The Journal of Prosthodontic Research (JPR) were selected from the Scopus list of journals as oral surgery journals. Maxillofacial Plastic and Reconstructive Surgery (MPRS) was selected from PubMed as a Scopus oral surgery title. From these titles, 10 recently published articles were collected and used for reference analysis.

Results

The percentage of citations from oral surgery journals was 26.7%, 24.5%, and 40.1% for JKAOMS, MPRS, and JOMS, respectively. In total, 1.1% of JPR's citations were from oral surgery journals and significantly fewer from other journals (P<0.001). The percentage of citations from dentistry journals excluding oral surgery journals was 11.9%, 34.4%, and 15.8% for JKAOMS, MPRS, and JOMS, respectively. For JPR, 80.6% of citations were from dentistry journals and significantly more were from other journals (P<0.001).

Conclusion

Selected samples revealed that JPR is incorrectly classified as an oral surgery journal in Scopus. In addition, the scientific interaction among JKAOMS, MPRS, and JOMS was different to JPR in the reference analysis.

Botulinum toxin A injection into the anterior belly of the digastric muscle increased the posterior width of the maxillary arch in developing rats

Background

The purpose of this study was to evaluate the effects of botulinum toxin A (BTX) injection into the anterior belly of the digastric muscle on a growing rat.

Methods

Ten Sprague Dawley rats were used in this study. When the rats were 13 days old, 0.5 units of BTX was injected into the anterior belly of the digastric muscle for the experimental group (n = 5). For the control, the same volume of normal saline was injected (n = 5). The rats were sacrificed at 60 days old, and the skulls were harvested for micro-computed tomography (μCT) analysis.

Results

In anthropometric analysis, the zygomatic arch and mandibular bi-condylar width were significantly lower in the experimental group than those in the control group (P = 0.025 and 0.027, respectively). The maxillary point width was significantly higher in the experimental group than that in the control group (P = 0.020).

Conclusion

BTX injection into the anterior belly of the digastric muscle had effects on the maxillofacial bony width in growing rats.

Effect of bisphosphonate on temporomandibular joint in osteopenia-induced rats by botulinum toxin A injection on masticatory muscle: a preliminary study

Background

Botulinum toxin injection on the masticatory muscle induces the osteopenic condition on the ipsilateral condyle. Bisphosphonate suppresses bone resorption and is used to treat osteopenic or osteoporotic condition. This study aimed to evaluate the effect of bisphosphonate administration on prevention of condylar resorption and botulinum toxin A-induced disuse osteopenia in rats.

Results

The volume of the condyle and bone volume/tissue volume (BV/TV, %) showed a strong tendency towards statistical significance (p = 0.052 and 0.058). Trabecular thickness (Tb.Th, mm) and trabecular number (Tb.N, 1/mm) were significantly smaller in the Botox group than in the other groups (p < 0.05). The volume of the condyle and BV/TV in the bisphosphonate 100 and bisphosphonate 200 groups showed similar values when compared with the control group.

Conclusion

Bisphosphonate administration after botulinum toxin A injection in the masticatory muscles appears to prevent condyle resorption and botulinum toxin-induced disuse osteopenia in rats.

Mandibular Bone Loss after Masticatory Muscles Intervention with Botulinum Toxin: An Approach from Basic Research to Clinical Findings

The injection of botulinum toxin type A (BoNT/A) in the masticatory muscles, to cause its temporary paralysis, is a widely used intervention for clinical disorders such as oromandibular dystonia, sleep bruxism, and aesthetics (i.e., masseteric hypertrophy). Considering that muscle contraction is required for mechano-transduction to maintain bone homeostasis, it is relevant to address the bone adverse effects associated with muscle condition after this intervention. Our aim is to condense the current and relevant literature about mandibular bone loss in fully mature mammals after BoNT/A intervention in the masticatory muscles. Here, we compile evidence from animal models (mice, rats, and rabbits) to clinical studies, demonstrating that BoNT/A-induced masticatory muscle atrophy promotes mandibular bone loss. Mandibular bone-related adverse effects involve cellular and metabolic changes, microstructure degradation, and morphological alterations. While bone loss has been detected at the mandibular condyle or alveolar bone, cellular and molecular mechanisms involved in this process must still be elucidated. Further basic research could provide evidence for designing strategies to control the undesired effects on bone during the therapeutic use of BoNT/A. However, in the meantime, we consider it essential that patients treated with BoNT/A in the masticatory muscles be warned about a putative collateral mandibular bone damage.

The effect of botulinum toxin-A injection into the masseter muscles on prevention of plate fracture and post-operative relapse in patients receiving orthognathic surgery

Background

Botulinum toxin-A (BTX-A) injection into muscle reduces muscular power and may prevent post-operative complication after orthognathic surgery. The purpose of this study was (1) to evaluate BTX-A injection into the masseter muscle on the prevention of plate fracture and (2) to compare post-operative relapse between the BTX-A injection group and the no injection group.

Methods

Sixteen patients were included in this study. Eight patients received BTX-A injection bilaterally, and eight patients served as control. All patients received bilateral sagittal split ramus osteotomy for the mandibular setback and additional surgery, such as LeFort I osteotomy or genioplasty. Post-operative plate fracture was recorded. SNB angle, mandibular plane angle, and gonial angle were used for post-operative relapse.

Results

Total number of fractured plates in patients was 2 out of 16 plates in the BTX-A injection group and that was 8 out of 16 plates in the no treatment group (P = 0.031). However, there were no significant differences in post-operative changes in SNB angle, mandibular plane angle, and gonial angle between groups (P > 0.05).

Conclusions

BTX-A injection into the masseter muscle could reduce the incidence of plate fracture.