Facial dog bites in children: A public health problem highlighted by COVID-19 lockdown.

BACKGROUND: Stay-at-home injunction during COVID-19 pandemic led to new dynamics in households and increased the risk of domestic accidents involving pets. The aim of the study was to demonstrate an increase of facial dog bites in children during first lockdown period in France, compared to the same period in 2018 and 2019. Secondary objective was to investigate the demographics and circumstances in which dog bites occurred. METHODS: A retrospective multicentric study was conducted nationwide. Patients under 18 years old managed in fifteen oral and maxillofacial surgery departments for a dog bite were included. RESULTS: Eighty-seven patients were included. A significant increase of the number of children managed for facial dog bite was noticed in 2020 (p = 0.0005). The male-to-female ratio was significantly reversed in 2020 with more bites in girls than boys (p = 0.02). In 2020, children were mostly bitten to cheeks (28.6 %), lips-and-chin region (26.2 %), and eyelids (23.8 %). Severe bites increased in 2020, in comparison with 2018 and 2019. Dog bites occurring while petting or playing significantly increased in 2020 (31 %) (p = 0.03). CONCLUSION: The process leading to bites is highly dependent on the balance of dog-owner relationship. This was strongly disrupted during COVID-19 pandemic, resulting in the increase of dog bites in households. Regarding dog bites, face is the most vulnerable area in children. Its injury has lots of esthetic and functional consequences and maxillofacial surgeons have a key role to play in their prevention. Reminders of some of these management and prevention strategies are presented in this article.

Masseter muscle pressure injury: First report of a prone position complication in patients with COVID-19.

We report the case of a 59-year-old, obese woman who underwent prolonged prone position during the medical management of an acute respiratory distress syndrome induced by SARS-CoV-2 infection, complicated by a masseter muscle pressure injury. Such side effect may be underestimate in intensive care units and should be prevent by prophylactic dressings on facial weight-bearing sites. The understanding of facial deep tissue injury is essential to guide clinical detection and management of such a complication in COVID-19 patients.

Script concordance test acceptability and utility for assessing medical students' clinical reasoning: a user's survey and an institutional prospective evaluation of students' scores.

Script Concordance Testing (SCT) is a method for clinical reasoning assessment in the field of health-care training. Our aim was to assess SCT acceptability and utility with a survey and an institutional prospective evaluation of students' scores.With a user's online survey, we collected the opinions and satisfaction data of all graduate students and teachers involved in the SCT setting. We performed a prospective analysis comparing the scores obtained with SCT to those obtained with the national standard evaluation modality.General opinions about SCT were mostly negative. Students tended to express more negative opinions and perceptions. There was a lower proportion of negative responses in the teachers' satisfaction survey. The proportion of neutral responses was higher for teachers. There was a higher proportion of positive positions towards all questions among teachers. PCC scores significantly increased each year, but SCT scores increased only between the first and second tests. PCC scores were found significantly higher than SCT scores for the second and third tests. Medical students' and teachers' global opinion on SCT was negative. At the beginning SCT scores were found quite similar to PCC scores. There was a higher progression for PCC scores through time.

Long-term dentoskeletal side effects of mandibular advancement therapy in patients with obstructive sleep apnea: data from the Pays de la Loire sleep cohort.

OBJECTIVES: Mandibular advancement devices (MADs) are the main therapeutic alternative to continuous positive airway pressure for obstructive sleep apnea. Our aim was to evaluate the long-term dentoskeletal side effects of MADs and to identify the predictive factors for these side effects. MATERIALS AND METHODS: Patients from the Pays de la Loire cohort treated with a custom-made MAD for at least 1 year were included in this retrospective study. Digital cephalometric analyses were performed at baseline and at follow-up. RESULTS: We included a total of 117 patients, treated with a MAD for a median [interquartile range] of 4.6 [2.6-6.6] years. The main significant side effects were a decrease in overbite (- 0.5 ± 1 mm), overjet (- 0.7 ± 1 mm) and maxillary incisor inclination (- 2.5 ± 2.8°) and an increase in mandibular incisor inclination (+ 2.2 ± 2.7°). Subjective side effects were not linked to the observed dentoskeletal changes. Current smokers were at higher risk of overjet modifications. A pre-existing anterior open-bite was associated with a greater decrease in overbite. Treatment duration was associated with a more pronounced mandibular incisor proclination. Propulsion was negatively associated with maxillary incisor retroclination. CONCLUSIONS: Long-term dentoskeletal side effects were mainly moderate dental side effects. Some predictive factors were shown to be associated with more pronounced changes. Subjective side effects did not appear to be reliable tools to detect dentoskeletal side effects. CLINICAL RELEVANCE: Regular follow-up with clinical examination and regular radiographs is mandatory. The predictive factors could be of interest for a better selection of patients and to individualize follow-up.

Predicting treatment response to mandibular advancement therapy using a titratable thermoplastic device.

OBJECTIVES: Mandibular advancement device (MAD) therapy is the most commonly used second-line treatment for obstructive sleep apnea (OSA), but MAD may be ineffective in a subgroup of patients. We describe the use of a trial of a titratable thermoplastic MAD to predict treatment outcomes with a custom-made MAD. MATERIALS AND METHODS: Patients treated with a thermoplastic MAD as a trial before custom-made MAD manufacturing were included in the study. Sleep recordings and clinical outcomes assessed after 6 months of treatment with each device were compared. Predictive utility of thermoplastic MAD to identify custom-made MAD treatment success defined as a reduction greater than 50% and final apnea-hypopnea index (AHI) less than 10 events/h was evaluated. RESULTS: Thermoplastic MADs were installed in 111 patients, but only 36 patients were finally treated with both devices and were included in the analysis. A significant correlation was observed between the impact of the two devices on the AHI (r=0.85, p<0.0001), oxygen desaturation index (r=0.73, p<0.0001), snoring index (r=0.85, p<0.0001), and Epworth sleepiness scale (r=0.77, p<0.0001). A high positive predictive value (86%) but a low negative predictive value (46%) was observed regarding AHI decrease. CONCLUSIONS: Similar impacts of both MADs were observed on major OSA severity markers and symptoms. The ability of thermoplastic MAD to indicate likelihood of success with custom-made MAD will require further controlled studies. CLINICAL RELEVANCE: Thermoplastic MADs could represent a useful and easily implemented tool to predict the likelihood of success of a custom-made MAD as treatment for OSA.

In vivo osseointegration and erosion of nacre screws in an animal model.

The use of resorbable devices for osteosynthesis has become a subject of interest. Nacre has been proposed as a resorbable and osteoconductive material favoring bone apposition without triggering an inflammatory reaction. We compared the in vivo osseointegration and erosion of nacre screws in an animal model with titanium screws. Implantation of similar nacre and titanium screws was performed in the femoral condyles of adult rats. Animals (n = 41) were randomized in four groups sacrificed at day one, 1, 6, and 12 months. Microcomputed tomography (microCT) allowed 3D morphometry of erosion of nacre. Osseointegration was measured as the volume of trabecular bone bone volume/tissue volume (BV/TV) in a standardized volume of interest around each screw. Undecalcified bone histology was also done. Gross examination revealed a similar clinical osseointegration for titanium and nacre screws. A progressive erosion of nacre screws, but no erosion of titanium screws, was observed in microCT. The volume of nacre screws progressively decreased over time whereas no modification occurred for titanium. For titanium screws, BV/TV remained stable throughout the study. For nacre screws, the BV/TV decrease was not statistically different. A significant difference was found between nacre and titanium screws at 6 months but not at 12 months. The screw heads, outside the bone shaft, were not eroded even after 12 months. Erosion of nacre occurred during the entire study period, only within the bone shaft in direct contact with bone marrow. Bone apposition was observed on nacre surfaces without signs of erosion. Nacre is a promising biomaterial in maxillofacial surgery.

Computational fluid dynamics simulation from microCT stacks of commercial biomaterials usable for bone grafting.

Granules of calcium/phosphate biomaterials are used to fill small bone defects in oral and maxilla-facial surgery. Granules of natural (e.g., trabecular bone, coral) or synthetic biomaterials are provided by industry. Small granules can also form of putty. The 3D geometry of granules creates a macroporosity allowing invasion of vascular and bone cells when pores are larger than 300 µm. We analyzed the 3D-porosity of 11 different stacks of biomaterials: Osteopure®, CopiOs®, Bio-Oss®, TCP Dental HP®, KeraOs®, TCH®, Biocoral®, EthOss® and Nanostim®. For each granular biomaterial, two sizes of granules were analyzed: small and large. Microcomputed tomography (microCT) determined porosity and microarchitectural characteristics of the biomaterials stacks. Computational fluid dynamics (CFD), a simulation method, was used on the stacks of microCT images. Stacks of small granules had a much lower permeation and fluid velocity than large granules and the hydraulic tortuosity was increased. Significant correlations were observed between microarchitecture parameters (porosity, mean pore diameter and specific surface) and fluid dynamic parameters. The two putties were associated with low (or absence of) porosity and permeation study revealed a very low (or absence) of flow rate. Stacks of granules represent 3D scaffolds resembling trabecular bone with an interconnected porous microarchitecture. Small granules create pores less than 300 µm in diameter; this induces a low fluid flow rate. CFD simulates the accessibility of body fluids and progenitor cells and confirms that it is depending on the shape and 3D arrangements of granules within a stack. Large granules must be preferred to putties and small granules.

Mandibular bone effects of botulinum toxin injections in masticatory muscles in adult.

OBJECTIVE: Botulinum toxin (BTX) is injected into masticatory muscles to treat various conditions. Animal studies have demonstrated bone loss at the condylar and alveolar regions of the mandible after BTX injection into masticatory muscles. The aim of the present study was to investigate mandibular bone changes in patients who received BTX injections in masticatory muscles. STUDY DESIGN: Twelve adult patients who received BTX injections into masticatory muscles were included in this study. Cone beam computed tomography (CBCT) was performed before and 12 months after the injection. The condylar and alveolar regions of the mandible were analyzed by using texture analysis of the CBCT images with the run length method. Condylar cortical thickness was measured, and 3-dimensional analysis of the mandible was also performed. Six patients who did not receive BTX injections were used as controls. RESULTS: A run length parameter (gray level nonuniformity) was found to be increased in condylar and alveolar bones. A significant cortical thinning was found at the anterior portion of the right condyle. Three-dimensional analysis showed significant changes in the condylar bone and at the digastric fossa. No changes in mandibular angles were found. CONCLUSIONS: This study identified mandibular bone changes in adult patients who received BTX injection into masticatory muscles.

Maxillary sinus floor elevation using Beta-Tricalcium-Phosphate (beta-TCP) or natural bone: same inflammatory response.

Sinus elevation is a common procedure to increase bone volume in the atrophic maxilla to allow placement of dental implants. Autogenous bone is the gold standard but is limited in quantity and causes morbidity at the donor site. ß-TCP is a synthetic biomaterial commonly used in that purpose. It appears to induce a poor inflammatory response. This study aimed to evaluate the degree of edema of the sinus mucosa after sinus lift surgery according to the type of biomaterial. Forty sinuses (20 patients) were included retrospectively and divided into 2 groups according to the biomaterial that was used: synthetic biomaterial (BTCP group), natural bone (BONE group). A control group (CTRL group) was constituted by the non-grafted maxillary sinuses. Twelve measurements per sinus were realized on pre- and post-operative computed tomography and averaged to provide the sinus membrane thickness value (SM.Th). SM.Th was thicker post-operatively in the BTCP and BONE groups in comparison with the CTRL group and in comparison with pre-operative measurements. No difference was found post operatively between the BTCP and BONE groups. We found that a synthetic biomaterial (ß-TCP) induced the same degree of edema, and thus of inflammation, as natural bone. It constitutes therefore an interesting alternative to autogenous bone for maxillary sinus lifts.

Giant cells and osteoclasts present in bone grafted with nacre differ by nuclear cytometry evaluated by texture analysis.

Nacre (mother of pearl) is a natural biomaterial used to prepare orthopedic devices. We have implanted screws and plates made with nacre in five sheeps. Bone were harvested after two months and embedded in poly(methyl methacrylate). Blocks were saws and the thick slabs were grinded, polished and surface stained. Sections were photographed at an ×1000 magnification. Giant cells were found in contact with nacre in eroded areas and true osteoclasts were found at distance in the neighboring bone in Howship lacunae. A texture analysis of the nuclei of giant cells and osteoclasts was done using the run-length method of the MaZda freeware. The size of the nuclei was reduced in osteoclast and their mean gray level appeared reduced. Texture analysis revealed that chromatin had a completely different pattern in giant cells when compared to osteoclasts. Giant cells had a fine repartition of the chromatin with large clear areas around prominent nucleoli. On the contrary, osteoclast nuclei had chromatin blocks evenly dispersed in the nuclei. This reflects the different origin of these cells expressing different functions.

Muscle Forehead Flap: Salvage Surgery for Closure of Cutaneous Fistula After Cranioplasty Exposure.

BACKGROUND: Infection and skin fistula are well-known complications after cranioplasty leading to reconstruction exposure and usually requiring new surgical procedure with poor condition for cutaneous closure. We describe 2 cases using muscle forehead flap (MFF) to treat skin fistula and cranioplasty exposure. CASE DESCRIPTION: The first case was a 43-year-old man who underwent a calvarial bone graft of the frontal sinus anterior wall after craniofacial trauma. Three months postoperatively, osteitis of the bone reconstruction and a skin fistula occurred in the median frontal region. The second case was a 37-year-old woman treated for a cingular glioblastoma by 3 surgeries, concomitant chemoradiation therapy, and frontal reconstruction using a titanium plate. She presented a plate exposure associated with cerebrospinal fluid leak and meningitis. Both patients were successfully treated by surgical removal of the frontal cranioplasty and skin closure using MFF. We observed a satisfying cosmetic result with no recurrence of infection or fistula at 12 and 4 months, respectively. CONCLUSIONS: MFF is a surgical option to treat complex cases of cutaneous fistula secondary to cranioplasty exposure of the anterior cranial fossa.

Biomaterial granules used for filling bone defects constitute 3D scaffolds: porosity, microarchitecture and molecular composition analyzed by microCT and Raman microspectroscopy.

Biomaterials are used in the granular form to fill small bone defects. Granules can be prepared with a grinder from trabecular bone samples or provided as synthetic biomaterials by industry. Granules occupy the 3D-space and create a macroporosity allowing invasion of vascular and bone cells when the inter-granular pores are larger than 300 µm. We compared the 3D-porosity of granule stacks obtained or prepared with nine biomaterials Osteopure® , Lubboc® , Bio-Oss® , CopiOs® , TCP Dental® , TCP Dental HP® , KeraOs® , and TCH® in comparison with that of human trabecular bone. For each biomaterial, two sizes of granules were analyzed: 250-1000 and 1000-2000 µm. Microcomputed tomography determined porosity and microarchitectural characteristics of granular stacks and Raman microspectroscopy was used to analyze their composition. Stacks of 250-1000 µm granules had a much lower porosity than 1000-2000 µm granules and the maximum frequency of pores was always centered at 200-250 µm. One biomaterial contained substantial amount of cortical bone (Bio-Oss® ). The highest porosity and pore size was obtained with TCP Dental HP. Raman spectroscopy found differences in biomaterials of the same composition. Stacks of granules represent 3D scaffolds resembling trabecular bone with an interconnected porous microarchitecture. Small granules have created pores <300 µm in diameter; this can interfere with vascular colonization. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 415-423, 2019.

Bone mineralization and vascularization in bisphosphonate-related osteonecrosis of the jaw: an experimental study in the rat.

OBJECTIVES: Pathogenesis of bisphosphonate-related osteonecrosis of the jaws (BRONJ) is not fully explained. An antiangiogenic effect of bisphosphonates (BPs) or an altered bone quality have been advocated. The aims of the present study were to analyze alveolar mandibular vascularization and bone quality in rats with BRONJ. MATERIALS AND METHODS: Thirty-eight Sprague-Dawley rats were randomized into two groups: zoledronic acid (ZA), n = 27, and control (CTRL) n = 11. The ZA group received a weekly IV injection of ZA (100 µg/kg) during 10 weeks. The CTRL group received saline. After 6 weeks, extraction of the right mandibular molars was performed. Rats were sacrificed after 14 weeks. Microtomography characterized bone lesions and vascularization after injection of a radio-opaque material. Raman microspectroscopy evaluated bone mineralization. RESULTS: Fifty-five percent of ZA rats presented bone exposure and signs of BRONJ. None sign was found at the left hemimandible in the ZA group and in the CTRL group. Vascular density appeared significantly increased in the right hemimandibles of the CTRL group compared to the left hemimandibles. Vascularization was reduced in the ZA group. A significantly increased of the mineral-to-amide ratio was found in the alveolar bone of ZA rats by Raman microspectroscopy. CONCLUSIONS: In a rat model of BRONJ, microtomography evidenced osteonecrosis in BRONJ. Raman spectroscopy showed an increased mineralization. Vascularization after tooth extraction was impaired by ZA. CLINICAL RELEVANCE: Prolonged BP administration caused an increase in the mineralization and a quantitative reduction of the vascularization in the alveolar bone; both factors might be involved concomitantly in the BRONJ pathophysiology.

Congenital Midline Upper Lip Sinuses: 3 Rare Cases.

Congenital sinuses of the upper lip are rare congenital malformations. There have been only 40 cases described in the literature. We report 3 cases of congenital midline upper lip sinus in Caucasian children. Two of those lesions were associated with other anomalies (complete cleft palate and hemifacial macrosomia or submucous cleft palate with bifid uvula). The pathophysiology remains unexplained yet. Congenital upper lip sinuses can be considered as possible microforms of cleft-lips. Associated anomalies are frequent and must be sought. The treatment is a full excision of the sinus tract and of the skin around the punctum in order to avoid risks of recurrence.

Tooth Extraction Locally Stimulates Proliferation of Multiple Myeloma in a Patient with Mandibular Localizations.

OBJECTIVES: Multiple myeloma (MM) is characterized by the occurrence of osteolytic lesions. MM treatment usually involves antiresorptive drugs (mainly bisphosphonates). CASE REPORT: A patient with an MM presented osteolytic lesions of the mandible. Extraction of teeth 45 and 46 was performed 5 years after the diagnosis of periodontitis. Four months later, osteonecrosis of the jaw (ONJ) was diagnosed at the extraction site. X-ray showed an extension of osteolytic lesions on the right side, close to the extraction site, without modification of the lesions on the left side. Two months later, a curettage was performed because of a painful bone sequestration. X-ray showed an extension of the osteolytic lesions on the right side. RESULTS: Histological analysis found a vascularized plasmacytoma of the soft tissues around the ONJ. Analysis of the bone showed mixed lesions with osteonecrotic areas and living bone resorbed by active osteoclasts surrounding a plasmacytoma. The surface area of the osteolytic foci has considerably increased only close to the extraction site. CONCLUSIONS: Tooth extraction triggered an ONJ associated with bisphosphonate treatment. However, it also seemed to induce a considerable proliferation of plasma cells at the extraction site; we hypothesize that it is due to the increase in bone remodeling related to the surgical trauma.

Comparison of titrable thermoplastic versus custom-made mandibular advancement device for the treatment of obstructive sleep apnoea.

BACKGOUND AND OBJECTIVES: The disadvantages of custom-made mandibular advancement devices (MAD) for obstructive sleep apnoea (OSA) therapy are the cost and delay required to manufacture the device. This study aimed to evaluate the efficacy of a titrable, thermoplastic MAD compared to a custom-made MAD for OSA therapy. METHODS: In this prospective nonrandomized study, 158 patients with OSA from two French sleep centers were treated for 6 months with a titrable thermoplastic MAD (n = 86) or a custom-made MAD (n = 72). The primary outcome was the change in sleep-disordered breathing (SDB) severity. RESULTS: After adjustment for baseline values, age, body mass index and study site, no significant intergroup differences were observed between thermoplastic and custom-made MAD for the outcome of apnoea, hypopnoea and oxygen desaturation indices. No between treatment differences were observed for the outcome of subjective sleepiness, symptoms of snoring and fatigue, depressive symptoms, and quality of life. Thermoplastic MAD therapy was associated with higher side effects scores for tooth pain (p < 0.0001) and self-reported occlusal changes (p = 0.0069). Mean (SD) reported compliance was lower in the thermoplastic MAD group than in the custom-made MAD group (6.4 [0.2] vs 7.1 [0.1] h/night; p = 0.035). CONCLUSIONS: This study demonstrates the efficacy of a titrable thermoplastic MAD in reducing SDB and related symptoms in patients with mild to severe OSA. Reported compliance at 6 months was high despite more dental discomfort than with custom-made MAD.

Contrast enhancement with uranyl acetate allows quantitative analysis of the articular cartilage by microCT: Application to mandibular condyles in the BTX rat model of disuse.

Microcomputed tomography (microCT) is well adapted to quantitative analysis of calcified tissues but soft tissues (such as cartilage) are radiolucent and need a contrast enhancement procedure for microCT. We developed a "staining" method allowing microCT imaging of articular cartilage using uranyl acetate (UA). The method was used to see whether adult rats with a botulinum toxin (BTX) injection in masticatory muscles present a change at the condylar cartilage of the mandible in association with a localized trabecular bone loss. Human femoral head samples were used to develop the enhanced contrast method using UA or lanthanides (recently proposed as a substitute for UA). The method was then applied to the condylar cartilage of rat mandibles. Mature male rats (n=11) were randomized into 2 groups: control (CTRL; n=4) and BTX group (n=7). Rats of the BTX group received a single injection of BTX into the right M. Masseter and M. Temporalis. Rats of the CTRL group were similarly injected with saline. Rats were sacrificed 4 weeks after injection. Condyles were harvested, fixed in formalin and immersed in UA. MicroCT was performed for bone and cartilage measurements. After UA impregnation, articular cartilage of human femoral head samples was clearly seen on its full thickness whereas lanthanides produced a much less pronounced contrast, with a faint labeling at the upper layer. In BTX rats, microCT analysis showed a significant bone loss at the right condyles. After UA, the whole thickness of articular cartilage was clearly evidenced. Cartilage thickness measurement showed no difference when comparing the right with the left sides of the BTX group nor between the two sides of the CTRL group. Contrast enhancement with UA is a simple technique allowing quantitative analysis of cartilage by microCT.290 words.

Asymmetric bone remodeling in mandibular and maxillary tori.

OBJECTIVES: Tori are frequent paucisymptomatic bony outgrowths of the oral cavity in three locations: torus palatinus (TP), mandibularis (TM), and maxillaris (TMax). Their usually described histological characteristics are unspecific: normal cortical bone with more or less trabecular bone. The aim of this study was to describe tori's specific morphological and histomorphometric characteristics. MATERIALS AND METHODS: Histological characteristics in a series of 18 tori collected after surgical removal were analyzed. Microcomputed tomography provided a 3D analysis. Mineral apposition rate (MAR) was measured after double tetracycline labeling. Osteoid tissue was identified by Goldner's trichrome and osteoclasts by the tartrate resistant acid phosphatase identification in undecalcified sections. Iron and aluminum were detected by histochemical staining methods. Osteoid thickness and MAR were determined at the outer surface of the torus and in the Haversian canals. RESULTS: Tori appeared made of lamellar Haversian bone in 16/18 cases. Osteoid thickness did not differ between the outer surface and within the canals. An asymmetric bone remodeling was observed in the Haversian canals of 15 tori: osteoid seams were deposited on the side close to the free torus surface, and Howship's lacunae with numerous osteoclasts were observed on the opposite side. A high MAR was found at the surface of the tori and within the canals. There was no iron or aluminum deposit. CONCLUSIONS: Tori may be characterized by a specific asymmetric bone remodeling which seems to determine their shape. CLINICAL RELEVANCE: This finding could constitute a specific histological feature allowing to differentiate tori from exostoses. Graphical abstract.

Botulinum toxin in masticatory muscles of the adult rat induces bone loss at the condyle and alveolar regions of the mandible associated with a bone proliferation at a muscle enthesis.

In man, botulinum toxin type A (BTX) is injected in masticatory muscles for several indications such as trismus, bruxism, or masseter hypertrophy. Bone changes in the mandible following BTX injections in adult animal have therefore became a subject of interest. The aim of this study was to analyze condylar and alveolar bone changes following BTX unilateral injections in masseter and temporal muscles in adult rats. Mature male rats (n = 15) were randomized into 2 groups: control (CTRL; n = 6) and BTX group (n= 9). Rats of the BTX group received a single injection of BTX into right masseter and temporal muscles. Rats of the CTRL group were similarly injected with saline solution. Rats were sacrificed 4 weeks after injections. Masticatory muscles examination and microcomputed tomography (microCT) were performed. A significant difference of weight was found between the 2 groups at weeks 2, 3 and 4 (p < 0.05). Atrophy of the right masseter and temporal muscles was observed in all BTX rats. MicroCT analysis showed significant bone loss in the right alveolar and condylar areas in BTX rats. Decrease in bone volume reached -20% for right alveolar bone and -35% for right condylar bone. A hypertrophic bone metaplasia at the digastric muscle enthesis was found on every right hemimandible in the BTX group and none in the CTRL group. BTX injection in masticatory muscles leads to a significant and major mandible bone loss. These alterations can represent a risk factor for fractures in human. The occurrence of a hypertrophic bone metaplasia at the Mus Digastricus enthesis may constitute an etiological factor for tori.