Ikuya Miyamoto

Background: Medication‐related osteonecrosis of the jaw (MRONJ) is a side effect mainly caused by antiresorptive agents (ARAs), but multi‐kinase inhibitors can also rarely cause MRONJ. Here, three cases of MRONJ that occurred in a single center during the use of cabozantinib for renal cell carcinoma are described. Case Presentations: Identified local triggers during cabozantinib therapy included inflammation around a bridge pontic, apical periodontitis, and ill‐fitting dentures. During MRONJ development, > 84, 2, and 31 months had elapsed since the last administration of ARAs, respectively. Conclusion: Dental oncologists and general dentists should be aware of the potential risk of MRONJ in patients receiving cabozantinib, particularly those with prior exposure to ARAs.

Mandibular osteoradionecrosis (ORN) is difficult to reconstruct because irradiated tissues are fibrotic and devitalized, and postoperative malalignment—particularly loss of condylar position—can compromise function and aesthetics. A 74-year-old man developed advanced right mandibular ORN after chemoradiotherapy for oropharyngeal carcinoma; conservative management failed, and segmental mandibulectomy was indicated. Reconstruction was performed with a left fibula free flap guided by an in-house computer-aided design/computer-aided manufacturing (CAD/CAM) workflow using patient-specific instruments (PSI), including mandibular and fibular cutting guides and a fibula assembly guide. The mandibular guide integrated anterior and posterior cutting components with stabilizing bars to help preserve mandibular continuity and condylar position, and aligned screw holes enabled accurate transfer of the virtual plan and facilitated plate fixation. Operative time was 9 h 58 min with an estimated blood loss of 700 mL. Postoperative imaging showed minor surface deviation of the reconstructed segment (<3 mm) with medial drift of the ipsilateral condyle (~7 mm). At 3 months, the patient maintained stable occlusion with a maximum mouth opening of 30 mm without complications. This case illustrates that PSI-guided fibula free flap reconstruction using an in-house CAD/CAM process can provide a practical and reproducible approach for advanced mandibular ORN while supporting postoperative mandibular alignment.

Purpose Discontinuing bone-modifying agents (BMAs) during management of medication-related osteonecrosis of the jaw (MRONJ) remains controversial. This retrospective study evaluates the impact and potential risks of BMA drug holidays in cancer patients with MRONJ. Methods We retrospectively classified 156 cancer patients with MRONJ into four groups: BMA withdrawal with conservative therapy (WC, n = 40), withdrawal with surgical therapy (WS, n = 63), non-withdrawal with conservative therapy (nWC, n = 30), and non-withdrawal with surgical therapy (nWS, n = 23). In the WS group, surgery was performed after radiographic confirmation of bone sequestration following BMA discontinuation. Healing rates and skeletal-related events (SREs) incidence were analyzed. Results The healing rates from MRONJ onset were 94.7% in the WS group, 53.6% in the nWS group, 25.5% in the WC group, and 0% in the nWC group. Among surgical patients, the healing rate from the time of surgery was significantly higher in the WS group (92.3%) than in the nWS group (47.8%) (hazard ratio = 3.23, p < 0.05). The incidence of SREs was 52.3% in the WC group, 15.8% in the WS group, 16.7% in the nWS group, and 4.2% in the nWC group. The WC group showed a significantly higher incidence of SREs compared with the WS and nWS groups. Conclusion A therapeutic strategy involving planned BMA discontinuation followed by delayed surgical intervention after radiographic confirmation of sequestrum formation, may be associated with improved healing outcomes. This approach does not appear to increase the incidence of SREs, particularly when BMA therapy is appropriately resumed after successful surgical healing.

The relationships among bacterial flora, diseases, and diet have been described by many authors. An operational taxonomic units (OTUs) are the result of clustering the 16S rRNA gene sequences at a certain cutoff value, and they are considered compositional data. As Pearson’s correlation coefficient is difficult to interpret, Aitchison’s ratio analysis was used to develop a method to handle compositional data. Multivariate analysis was developed because univariate analysis can be subject to large biases. Simulations regarding absolute abundance based on certain assumptions and some analyses, such as nonparametric multidimensional scaling (NMDS), principal component analysis (PCA), and ratio analysis, were conducted in this study. The same content as a 100% stacked bar graph could be expressed in low dimensions using PCA. However, the relative diversity was not reproducible with NMDS. Various assumptions were made regarding absolute abundance based on the relative abundance. However, which assumptions are true could not be determined. In summary, ratio analysis and PCA are useful for analyzing compositional data and the gut microbiota.

The purpose of this retrospective study was to evaluate computer-assisted virtual surgery and the outcomes of mandibular reconstruction using an autogenous particulate cancellous bone and marrow (PCBM) graft combined with a custom-made titanium mesh (TiMesh) using a three-dimensional (3D) printing model. Eighteen consecutive patients were included, and preoperative virtual simulation surgery was performed using digital data. Segmental bone defects showed deviation of the mandible due to displacement of the condyle and segments, unnatural length of the mandibular body, or poorer intermaxillary relationship compared to the marginal bone defect caused by previous operations. These mandibular disharmonies could be simulated, and virtual surgery was performed on a computer with adjustment of displaced mandibular segments, length of the mandibular body, and dental arch with digital bone augmentation. TiMesh was manually pre-bent using a 3D printing model, and PCBM from the iliac crest was grafted with TiMesh. The short-term clinical results were good; reconstruction of the alveolar crest was prosthetically desirable; and minor complications were observed. In conclusion, virtual reconstruction is crucial for treating complex deviated mandibles. Accurate condylar and dental arch positions with an optimum mandibular length are important for prosthetically satisfactory mandibular reconstruction.

Myxoma is a benign tumor of mesenchymal origin. It frequently occurs in the muscles of the hip and extremities; however, it rarely occurs in the head and neck region. This report describes the second case of an intramuscular myxoma of the tongue. A 23-year-old woman was referred to our institution for the diagnosis and treatment of a left tongue lesion. T2-weighted magnetic resonance imaging revealed an - mm mass in the tongue. Based on a clinical diagnosis of a tongue tumor, excisional biopsy was performed under general anesthesia. The histopathological diagnosis was an intramuscular myxoma. The postoperative course was uneventful, and there was no evidence of tumor recurrence 3 years after surgery.

This study aimed to clarify the advantages and disadvantages of conventional visual inspection (CVI), endoscopic white light imaging (WLI), and narrow-band imaging (NBI) and to examine the diagnostic accuracy of intraepithelial papillary capillary loops (IPCL) for the detection of oral squamous cell carcinoma (OSCC). This cross-sectional study included 60 participants with oral mucosal diseases suspected of having oral potentially malignant disorders (OPMDs) or OSCC. The patients underwent CVI, WLI, NBI, and incisional biopsy. Images were evaluated to assess the lesion size, color, texture, and IPCL. Oral lichen planus (OLP) and oral leukoplakia lesions were observed in larger areas with NBI than with WLI; 75.0% were associated with low-grade (Type 0–II) IPCL. Various types of oral leukoplakia were seen; however, all OSCC cases showed high-grade (Type III–IV) IPCL. The diagnostic accuracy of high-grade IPCL for OSCC showed a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 80.9%, 59.1%, 100%, and 85.0%, respectively. A non-homogeneous lesion with high-grade IPCL strongly suggested malignancy. Overall, our results indicate that WLI and NBI are powerful tools for detecting precancerous and cancerous lesions using IPCL. However, NBI is influenced by mucosal thickness; therefore, image interpretation is important for accurate diagnosis.

Pseudogout is a disease characterized by calcium pyrophosphate crystal deposition. Involvement of the temporomandibular joint (TMJ) is rare. We herein report a case of tophaceous pseudogout of the TMJ with cranial extension. An 83-year-old woman was referred to our institution for treatment of right TMJ pain. The patient’s medical and family histories were unremarkable. Magnetic resonance imaging showed a mass of about 35 mm in diameter compressing the bottom of the right temporal lobe of the brain. Based on a clinical diagnosis of a right TMJ tumour, biopsy was performed under general anaesthesia. The histopathological diagnosis was pseudogout. Considering the risk of surgically induced brain damage, the patient’s advanced age and her relatively good quality of life, the treatment plan simply involved the observation of the lesion. Fourteen months after biopsy, the patient’s activities of daily living remained unchanged and she had no TMJ pain.

Osteosarcoma is a malignant tumor in which the cancerous cells produce an osteoid matrix or mineralized bone. Jaw bones are affected in 6% of all osteosarcomas and are the fourth most common site of origin. Surgical treatment of osteosarcoma in elderly patients is rarely reported. Here, we report successful treatment of osteosarcoma arising in the mandible of a 90-year-old man. The patient was referred to our institution for diagnosis and treatment of an oral lesion. Intraoral examination revealed that a hard mass measuring was located on the floor of the oral cavity, attached to the bone, and its growth displaced the tongue posteriorly. Therefore, he experienced difficulty in speech and swallowing. Biopsy of the mandibular mass was suspicious for chondrosarcoma. Preoperative examination did not detect critical risks for general anesthesia or surgery. Based on a clinical diagnosis of a malignant bone tumor of the mandible, segmental mandibular resection with reconstruction using a titanium plate was performed. Surgical site infection occurred on postoperative day 12, which was resolved by drainage, local irrigation, and administration of antibiotics. There was no delirium or cardiovascular or pulmonary complications. Surgery resolved the patient’s difficulties in speech and swallowing. There was no evidence of tumor recurrence or metastasis 4 years after surgery. This case showed that it was not necessary to exclude surgical treatment merely because the patient was 90 years old. Indications for surgery should be determined individually to improve the patient’s quality of life.

Mandibular reconstruction using a titanium mesh tray and autologous bone is a common procedure in oral and maxillofacial surgery. However, there can be material problems—such as broken titanium mesh trays—which may undermine long-term functionality. This study was designed to investigate the optimal conditions for a titanium mesh tray with an ideal mandibular shape and sufficient strength, using computer-aided design, computer-aided manufacturing technology, and electron beam additive manufacturing. Specimens were prepared using Ti-6Al-4V extra low interstitial titanium alloy powder and an electron beam melting (EBM) system. The mechanical strength of the plate-shaped specimens was examined for differences in the stretch direction with respect to the stacking direction and the presence or absence of surface treatment. While evaluating the mechanical strength of the tray-shaped specimens, the topology was optimized and specimens with a honeycomb structure were also verified. Excellent mechanical strength was observed under the condition that the specimen was stretched vertically in the stacking direction and the surface was treated. The results of the tray-shaped specimens indicated that the thickness was 1.2 mm, the weight reduction rate was 20%, and the addition of a honeycomb structure could withstand an assumed bite force of 2000 N. This study suggests that the EBM system could be a useful technique for preparing custom-made titanium mesh trays of sufficient strength for mandibular reconstruction by arranging various manufacturing conditions.