0. 1em 0.0 1em Key clinical Message :The treatment of mandibular osteonecrosis remains a challenge in medical and surgical care; This is particularly true given that invasive surgery can compromise healing and lead to complications. The aim of this case report is to consider a therapeutic gradient that favors local flaps rather than resection surgery.Abstract :Medications such as bevacizumab and denosumab are known to have vascular and bone effects that can lead to osteoneocris of the jaw. The presence of dental implants with limited dental hygiene can promote chronic local inflammation and exacerbate the phenomenon of medication related osteonecrosis of the jaw. Local flaps are an indicated in cases of moderate bone exposure.Introduction :Medication-related osteonecrosis of the jaw (MRONJ) is an adverse event associated with antiresorptive and antiangiogenic agents, characterized by an exposed bone or bone that can be probed through an intraoral or extraoral fistula in the maxillofacial region that has persisted for more than eight weeks in the absence of any history of radiation therapy to the jaws or metastatic disease to the jaws. (1)The pathophysiology of MRONJ is multifactorial, involving inhibition of bone remodeling, suppression of angiogenesis, and altered immune response, leading to impaired bone turnover and mucosal healing, particularly in inflammatory environments such as peri-implantitis, for example. (1)Bevacizumab, an anti-VEGF agent, interferes with neovascularization and tissue repair while denosumab, a monoclonal antibody against RANKL, inhibits osteoclastic activity and bone resorption. The concomitant administration of these two agents synergistically increases the risk of MRONJ by combining vascular compromise and reduced osseous remodeling capacity. (1,2)Although MRONJ most commonly occurs following tooth extraction or around pre-existing teeth, cases involving dental implants have also been reported, often presenting with advanced necrosis and soft tissue breakdown. (3) The development of an orocutaneous fistula is a rare and particularly challenging complication, as it reflects both the extent of necrosis and the difficulty of achieving durable closure in compromised tissues.Reconstructive management of such lesions remains complex due to the poor vascularity of the surrounding bone and soft tissues, as well as the increased risk of postoperative dehiscence. In this report, we present a case of mandibular MRONJ with orocutaneous fistula around dental implants in a patient receiving bevacizumab and denosumab, successfully treated with a buccinator myomucosal flap after failure of primary closureCase report :A 62-year-old patient presented to the Department of Oral and Maxillofacial Surgery at the University Hospital of Nice, France, referred by his dentist for exposed bone adjacent to the right mandibular dental implants.His medical history included a poorly differentiated hepatocellular carcinoma initially treated in 2023 with a regimen of folinic acid, fluorouracil, and oxaliplatin. In 2024, following the development of a bone metastasis, his treatment was modified to include bevacizumab and denosumab. He was also receiving long-term corticosteroid therapy for an immune-related rheumatic disease. His toxicological history was notable for a 45-pack-year smoking habit and alcohol dependence, from which he had been abstinent since 2020.Initial clinical and radiographic examination revealed exposed bone in relation to the right mandibular implants, without signs of infection, inflammation, or pain. The bone appeared avascular, with no bleeding upon probing, and implant mobility was estimated at approximately 1 mm along a transverse axis. A scintigraphy and an injected CT scan showed no abnormalities. (Figure 1)In the absence of significant local or systemic deterioration, a conservative approach was initially chosen, consisting of reinforced local oral hygiene measures and close clinical monitoring.Four months later, after a brief interruption in follow-up, the patient returned with a cutaneous fistula associated with purulent cervico-oral drainage. A bacteriological sample was obtained before local irrigation, and antibiotic therapy with amoxicillin–clavulanic acid (3 g/day for two weeks) was initiated. The antibiogram confirmed the appropriateness of the prescribed regimen.Given the unfavorable evolution, primary surgical closure was considered as a first-line intervention. A local sequestrectomy with bone contouring was performed using a piezoelectric device, preserving the most anterior implant. Following debridement and irrigation of the operative field, primary mucosal closure was achieved, along with closure of the orocutaneous fistula. The pathological examination of the bone showed findings consistent with osteonecrosis with actinomycotic superinfection. As a result, antibiotic therapy with amoxicillin-clavulanic acid 2 grams per day was administered for 2 months. (Figure 2-3) (4)Postoperatively, however, the patient wore his temporary removable prosthesis despite explicit instructions, resulting in early wound dehiscence and recurrent bone exposure.In light of this progression and the compromised quality of the surrounding tissues, reconstruction with a buccinator myomucosal flap was subsequently indicated.The flap was designed on the internal aspect of the ipsilateral cheek, with a posteriorly based pedicle located at the level of the retromolar trigone. The parotid duct orifice was identified prior to incision, and the anterior limit of the flap was placed 1 cm posterior to the labial commissure to preserve oral mobility and prevent postoperative traction.Dissection included the muscular portion of the buccinator, in accordance with the principles of the myomucosal flap technique. Once elevated, the flap was rotated and positioned to cover the mandibular defect, providing well-vascularized tissue and a tension-free closure.Resorbable sutures were used to secure the flap in place, and a fibrin sealant (Tisseel®) was applied over the closure to enhance watertightness and support tissue stabilization. (Figure 4)Healing at 6 months post op is satisfactory and allows the removable prosthesis to be worn. (Figure 5)Discussion :According to the AAOMS, MRONJ is defined as exposed bone persisting for more than eight weeks in a patient receiving antiresorptive or antiangiogenic therapy, without a history of radiation therapy or metastatic disease to the jaws. (1)The reported incidence of MRONJ varies considerably. As highlighted by the work of Al Rowis et al., it ranges form 1.9 to 11%, depending on the therapeutic indication and route of administation. The concomitant use of bevacizumab and denosumab significantly increases the risk of MRONJ.(5)Both agents contribute to hypovascularization, tissue hypoxia, and impaired bone remodeling, ultimately leading to chronic bone necrosis. (1) The patient’s immunocompromised state, combined with poor oral hygiene, further predisposes to MRONJ development. Dental implants placed before the initiation of antiresorptive therapy are generally considered safe; however, the lack of adequate oral hygiene in this case led to localized inflammation and progression of the osteonecrotic process. The proinflammatory cytokine IL-36α has a key role in the MRONJ incidence and is associated with remarkable upregulation, which is found in the infected periodontal tissue and gingival crevicular fluid. It leads to inhibiting collagen expression.(6)The initial attempt at primary closure followed the therapeutic principle of minimal invasiveness. After achieving sufficient tissue mobilization, a tension-free edge-to-edge closure was attempted. However, it is likely that excessive suture tension compromised the healing process. In addition, the patient wore a removable temporary prosthesis fabricated by his dentist immediately after hospital discharge, which probably exacerbated local mechanical irritation and impeded proper mucosal healing.The buccinator myomucosal flap (BMF) in the present case was guided by the need for a well-vascularized, pliable, and mucosa-lined tissue capable of achieving tension-free closure in a compromised surgical field. After the failure of primary closure, the local tissues showed poor perfusion and reduced elasticity due to the local inflammatory environment. In such a context, the BMF provides an ideal reconstructive option because of its reliable vascularization and anatomic proximity to the defect. (7,8)The flap is based on the buccal artery, a branch of the maxillary artery, ensuring robust blood supply even in the presence of partial vascular compromise of the periosteal or gingival tissues. Its myomucosal composition offers a mucosal surface suitable for intraoral reconstruction, with excellent color and texture match, while the inclusion of a thin layer of buccinator muscle improves vascular reliability and resistance to postoperative infection. (7,8)The arc of rotation and ease of harvest make the BMF particularly well suited for reconstruction of posterior mandibular defects, oroalveolar or orocutaneous fistula, and defects following osteonecrosis resection. Moreover, the donor site morbidity is minimal, with primary closure of the donor mucosa and preservation of buccal function and aesthetics. (8)Several local and regional flaps have been described for intraoral reconstruction in medication-related osteonecrosis of the jaw (MRONJ), each with specific indications and limitations.The facial artery musculomucosal (FAMM) flap is among the most widely reported alternatives. It provides a larger surface area and excellent reach, but requires careful dissection of the facial artery and is technically more demanding. In addition, venous congestion and limited mobility in posterior mandibular defects may occur. (9)The submental island flap provides a well-vascularized option for larger defects but involves a cervical incision, potential interference with oncologic surveillance, and aesthetic concerns—factors that are particularly relevant in patients with systemic cancer. (9)Free flaps (fibula, radial forearm, scapular) remain the gold standard for extensive segmental mandibular reconstruction, but their use in MRONJ is often limited by patient comorbidities, ongoing systemic therapy, and the risk of flap failure in a compromised vascular environment.Compared with these options, the buccinator myomucosal flap offers an optimal balance between vascular reliability, minimal invasiveness, functional preservation, and adaptability to small-to-medium defects. It can be performed under local or general anesthesia, without external scarring or need for microsurgical expertise, which makes it particularly suitable for fragile or polymedicated patients such as those with metastatic disease.The present case reinforces the principle that vascularized tissue coverage is crucial for achieving long-term healing in MRONJ, especially in patients under anti-angiogenic therapy. The early use of local myomucosal flaps such as the buccinator or FAMM flap should be considered whenever tissue tension, ischemia, or poor local healing conditions are anticipated.In addition, adjunctive therapies may enhance outcomes:Platelet-rich fibrin (PRF) membranes or other autologous platelet concentrates can improve angiogenesis and soft-tissue integration. (10,11)Photobiomodulation and low-level laser therapy have been reported to promote mucosal healing and reduce postoperative pain. (12)Systemic optimization, including discontinuation or temporary suspension of antiresorptive/antiangiogenic agents when possible, control of infection, and maintenance of good oral hygiene, remains essential. (13)Future research should focus on defining clear reconstructive algorithms for MRONJ according to defect size, drug exposure, and tissue quality. The buccinator myomucosal flap deserves greater attention in this context as a reliable, low-morbidity option for localized defects, especially after failure of conventional primary closure.In 2016, Woo experimented with this work in a sub-centimeter defect. (14). Our case involved a defect greater than two centimeters in length, associated with dental implants and complicated by an orocutaneous fistula, which further challenged reconstructionConclusion :The present case illustrates the complexity of managing MRONJ in patients receiving combined antiresorptive and antiangiogenic therapy. The buccinator myomucosal flap represents a reliable and minimally invasive reconstructive option for achieving durable closure in compromised tissues. Early use of well-vascularized local flaps should be considered in advanced MRONJ cases when tissue ischemia or mechanical tension is anticipated, particularly in patients receiving antiangiogenic therapy.
