Published papers

BACKGROUND: Parosteal osteosarcomas are usually low-grade tumors, however, sometimes they transform to high-grade tumors, which is named dedifferentiation. This phenomenon has been reported in long bones. Recently, we encountered a patient with dedifferentiated parosteal osteosarcoma occurring in the maxilla. Here, we report a first case of dedifferentiated parosteal osteosarcoma of the head and neck region. CASE PRESENTATION: A 45-year-old Japanese woman with a refractory bone lesion in the maxilla presented to our hospital. A biopsy showed atypical spindle cell proliferation involving dedifferentiated high-grade component, which was diagnosed as dedifferentiated parosteal osteosarcoma. Three cycles of neoadjuvant chemotherapy using ifosfamide and pirarubicin were performed followed by sub-total maxillectomy. Histopathological results showed that neoadjuvant chemotherapy was effective for high-grade component. The decision to perform adjuvant chemotherapy (cisplatin and pirarubicin) was made because distant metastasis has been reported, even in cases with dedifferentiated parosteal osteosarcoma in which complete necrosis of high-grade component was achieved due to neoadjuvant chemotherapy. There was no recurrence 15 months after surgery. CONCLUSIONS: Dedifferentiated parosteal osteosarcoma can occur in the head and neck region. Chemotherapy including anthracycline anticancer agent could be effective for high-grade component of dedifferentiated parosteal osteosarcoma.

Background: Microsurgery requires high skills for suturing using fragile threads, often within narrow surgical fields. Precise tension is required for good healing and to avoid the risk of thread breakage. Methods: To meet the demands, we developed a novel assist robot utilizing high-precision sensorless haptic technology. The robot adopts a cable-driven mechanism to maintain a distance from the surgical area and enhances compatibility with surgical equipment such as microscopes. The robot performance was verified through in vitro and in vivo experiments using a rat model. Results: The realization of precise tension control was confirmed in both experiments. In particular, in the in vivo experiments, the developed robot succeeded to produce a knot with an accurate tension of 0.66% error. Conclusions: The developed robot can realize to control traction force precisely. This technology might open up the window for a full assist robot for microsurgery with haptic feeling.

Low energy availability in female athletes often causes hypothalamic amenorrhea and osteoporosis, in turn promoting stress fractures. Mechanisms underlying these conditions remain unclear. Here we show that model mice subjected to food restriction (FR) or FR-plus-voluntary running exercise exhibit significantly reduced bone mineral density, cortical bone parameters and uterine weight than do control mice, and that these parameters worsen in the FR-plus-exercise group. Relative to controls, FR and FR-plus-exercise groups showed significantly lower mineral apposition rate and osteoclast number and significantly reduced serum insulin-like growth factor-1 (IGF1) levels. Outcomes were rescued by ED71 or 1.25(OH)2D3 treatment. Thus, we conclude that administration of active vitamin D analogues represents a possible treatment to prevent these conditions.

Ossification of the posterior longitudinal ligament (OPLL), a disease characterized by the ectopic ossification of a spinal ligament, promotes neurological disorders associated with spinal canal stenosis. While blocking ectopic ossification is mandatory to prevent OPLL development and progression, the mechanisms underlying the condition remain unknown. Here we show that expression of hydroxyacid oxidase 1 (Hao1), a gene identified in a previous genome-wide association study (GWAS) as an OPLL-associated candidate gene, specifically and significantly decreased in fibroblasts during osteoblast differentiation. We then newly established Hao1-deficient mice by generating Hao1-flox mice and crossing them with CAG-Cre mice to yield global Hao1-knockout (CAG-Cre/Hao1flox/flox; Hao1 KO) animals. Hao1 KO mice were born normally and exhibited no obvious phenotypes, including growth retardation. Moreover, Hao1 KO mice did not exhibit ectopic ossification or calcification. However, urinary levels of some metabolites of the tricarboxylic acid (TCA) cycle were significantly lower in Hao1 KO compared to control mice based on comprehensive metabolomic analysis. Our data indicate that Hao1 loss does not promote ectopic ossification, but rather that Hao1 functions to regulate the TCA cycle in vivo.

Objective: This study aimed to reveal the relationship between the approach of extraction and the position of the mesiodens by systematic classification. Methods: This retrospective study included patients with impacted mesiodens that required computed tomography for extraction. The direction, sagittal and axial position, eruption from the nasal floor, surrounding bone thickness, surgical approach, and anesthesia type for the impacted mesiodens were analyzed. Mesiodens were classified into three groups (V: vertical position, H: horizontal position, and D: direction), and each group was classified into three subgroups (V1, 2, 3; H1, 2, 3; D1, 2, 3). Results: A total of 169 impacted mesiodens were included in this study. The palatal approach was the most common (151 teeth, 89.3%), followed by the labial approach (11 teeth, 6.5%) and nasal floor approach (6 teeth, 3.6%). The bone thickness from the mesiodens to the palatal surface were significantly shorter in palatal far region of nasopalatine duct (H3) than in palatal near region (H2) (P < 0.05). In vertical high position (V3), the percentage of the palatal approach in H3 (87.5%) was higher than that in H2 (71.4%). Additionally, 15 teeth erupting from the nasal floor wherein four were extracted by the nasal floor approach in H2 but only one tooth in H3. Conclusions: Even at higher positions, mesiodens located in the palatal far region tended to be extracted by the palatal approach because of the thin bone thickness.

This prospective cohort study aimed to investigate the impact of medication-related osteonecrosis of the jaw (MRONJ) on health-related quality of life (HRQOL) and oral health-related QOL (OHRQOL) and the association between the downstaging of MRONJ and OHRQOL. The HRQOL and OHRQOL of 44 patients with MRONJ were assessed using the SF-36v2 and the General Oral Health Assessment Index (GOHAI), respectively. Treatment was performed in accordance with the AAOMS position paper (2014). The SF-36v2 and GOHAI scores at the beginning of the survey were used to evaluate the impact of MRONJ on QOL. Potential confounders affecting the association between downstaging and QOL improvement were selected using directed acyclic graphs. Multiple regression analysis was performed to evaluate causal inferences. HRQOL scale scores declined below the national average. The three-component summary score (3CS), comprising the physical component summary (PCS), mental component summary (MCS), and role/social component summary (RCS), revealed that performance status and primary disease significantly affected the PCS and RCS (P = 0.005 and P < 0.001, respectively) and PCS and MCS (P = 0.024 and P = 0.003, respectively). The MRONJ stage did not influence the 3CS; however, OHRQOL declined in a stage-dependent manner (P = 0.005). Downstaging of MRONJ was independently associated with the improvement rate of the total GOHAI scores after adjusting for variables (P = 0.045). The HRQOL of patients with MRONJ declined; however, this may depend on the underlying disease status rather than the MRONJ stage. Improvement of the disease status can potentially predict an improvement in OHRQOL, regardless of the treatment modality.

ABSTRACT Redox regulation is a key mechanism supporting tumor survival and an attractive therapeutic target. In this study, we screened 1161 FDA‐approved compounds to identify agents that induce reactive oxygen species (ROS) accumulation in head and neck squamous cell carcinoma (HNSCC) cells. Pimozide, a dopamine D2 receptor antagonist, emerged as the most potent ROS inducer. It selectively suppresses the growth of HNSCC cells with high oxidative stress resistance while exhibiting only modest effects on less resistant cells and normal keratinocytes. Notably, pimozide exhibited anti‐tumor effects as a monotherapy and in combination with paclitaxel at clinically relevant doses. Mechanistic analysis revealed that pimozide rapidly induced ROS accumulation via a mechanism distinct from its known action on dopamine D2 receptors and STAT3/5. To identify markers of ROS‐induced responses, we examined ROS‐responsive genes and found that early growth response 1 (EGR1) was selectively induced in sensitive cells and correlated with pimozide responsiveness. Functional analysis revealed that EGR1 knockdown suppressed pimozide‐induced cytotoxicity, suggesting its role as a functional pharmacodynamic marker of pimozide sensitivity. In a patient‐derived xenograft model of HNSCC, pimozide significantly reduced the tumor burden alone and in combination with paclitaxel. While tumor volume reduction in the combination group was not statistically greater than that in the monotherapy group, fluorescence immunohistochemistry revealed a marked decrease in undifferentiated tumor cells, indicating enhanced therapeutic effects of combination treatment. Taken together, these findings indicate that pimozide is a promising candidate for repurposing as a novel therapeutic agent against HNSCC.

Calcium-phosphate cement (CPC), a paste-like artificial bone, is a material form that allows minimally invasive treatment. However, CPC is not infection resistant, which may lead to surgical site infections. We recently developed a paste-like organic/inorganic hybrid artificial bone that is compatible with the bone remodeling cycle. In this study, we added silver-loaded tricalcium phosphate, which has antibacterial properties, to the hybrid CPC and fabricated a prototype “antibacterial CPC”. Antibacterial and non-antibacterial CPCs were implanted into a rabbit jaw defect model in which infection could occur, and the in vivo responses were compared. In cement specimens retrieved from rabbit jaws, residual material was observed with the non-antibacterial CPC, whereas with the antibacterial CPC, almost all of the material was resorbed and replaced with host bone. These results suggest that placement of antibacterial CPC in a rabbit jaw bone defect model susceptible to bacterial infection promotes material resorption and bone formation. The antibacterial CPC developed in this study is thus a novel paste artificial bone exhibiting good bioresorption and osteogenic potential in biological hard tissues. (Figure presented.)

Myelodysplastic syndrome is an acquired hematopoietic disorder showing symptoms of pre-leukemia and refractory anemia. In the tooth extraction process of such cases, bleeding tendency due to pancytopenia, infection etc., becomes a problem. As such, a cautious approach is required. We have confirmed platelet transfusion refractoriness prior to tooth extraction in a myelodysplastic syndrome patient, and hereby report a case of tooth extraction following human leukocyte antigen (HLA)-compatible concentrated platelet transfusion. The patient was a 55-year-old female who was examined at our department due to a request for the extraction of tooth No. 36. Following consultation at the Hematology Department, platelet transfusion was performed as a pretreatment upon hospitalization. Increased body temperature, chills, shivers, and feelings of discomfort in the pharynx were observed. A close examination was performed due to a lack of increase in platelet count, and revealed platelet transfusion refractoriness caused by anti-HLA antibodies. Therefore, the patient was re-hospitalized and transfused with a platelet concentrate-HLA preparation. One hour later, an increase in platelet count was confirmed and the tooth extraction was performed. There was no evidence of bleeding or infection following extraction, and the prognosis was good.

© 2019 Asian AOMS(+) ASOMP(+) JSOP(+) JSOMS(+) JSOM(+) and JAMI Spindle cell lipomas and pleomorphic lipomas are uncommon and distinct variants of benign lipomas. Although spindle cell lipomas and pleomorphic lipomas were originally considered different entities, the recent WHO classification defines them as spindle cell/pleomorphic lipoma (SCL/PL). This is because of their similar clinical features and the existence of intermediate histopathological features between them. A 77-year-old male presented to our clinic with a painless swelling on the left inferior border of the mandible. Computed tomography revealed a clearly defined mass in the subcutaneous lesion. With a histopathological diagnosis of myxolipoma, demonstrated by biopsy, excisional surgery was performed under general anesthesia. The histopathology revealed SCL/PL with the presence of spindle cells and mature adipocytes. No tumor recurrence had been noted at two year after surgery.

BACKGROUND: Calcium pyrophosphate dihydrate crystal deposition disease is a condition in which calcium pyrophosphate dihydrate crystal is deposited in joint cartilage and ligaments. Calcium pyrophosphate dihydrate crystal deposition disease that involves calcification around the odontoid process of the second cervical vertebra is called crowned dens syndrome. Crowned dens syndrome is accompanied by fever in addition to acute and intense neck, posterior head, and temporal pain; thus, distinguishing crowned dens syndrome may be difficult in the presence of odontogenic infection. To the best of our knowledge, this is the first report describing a patient with crowned dens syndrome with coexisting odontogenic infection. CASE PRESENTATION: A 75-year-old Japanese woman was examined in the Emergency Department of this hospital due to a chief complaint of worsened buccal swelling on the left side. An odontogenic infection was considered, and she underwent her first examination. She presented with a body temperature of 37.4 °C, marked swelling and tenderness of her left lower eyelid through to her left cheek, and pain on the left temporal area. Blood tests revealed a leukocyte count of 6700/μL and a C-reactive protein level of 7.15 mg/dL. There was swelling and pain around the gingiva and acute purulent apical periodontitis of left maxillary second premolar. Cellulitis of the left cheek was diagnosed. After performing drainage of the pus, antibiotic treatment was initiated. Although her clinical symptoms improved, blood tests on day 9 of hospitalization revealed a leukocyte count of 6500/μL and a C-reactive protein level of 25.62 mg/dL, which were indicative of worsening symptoms. Computed tomography was performed to evaluate remote infection and images revealed a calcification around the odontoid process of her second cervical vertebra. When she was referred to the Orthopedic Surgery Department, pseudogout of the cervical spine was diagnosed. Subsequently, oral acetaminophen was initiated, and both her leukocyte count and C-reactive protein improved markedly. CONCLUSIONS: In the presence of persistent fever and abnormally high leukocyte and C-reactive protein indicative of an inflammatory reaction, coexistence of pseudogout should be considered. In particular, when symptoms of temporal pain are present, the possibility of pseudogout of the cervical spine must be considered in the differential diagnosis.

Clear cell carcinoma (CCC) is a malignant neoplasm of epithelial origin classified in the 2017 World Health Organization (WHO) classification as a low-grade salivary gland tumor consisting of glycogen-rich clear cytoplasm. We report a case of a 34-year-old woman presented in our department following the complaint of a mass in her right retromolar area. The tumor measured 10-mm in diameter and was elastic and hard mass. Spontaneous pain or tenderness and desensitization of the tongue were not observed. Marginal resection of the mandible was performed under general anesthesia. The lesion was located in the minor salivary gland that is mainly composed of mucus glands and had a relatively clearly defined circular shape. However, there was no film fabrication in the surrounding resions. Additionally, atypical cells comprising a clear cytoplasm and irregularly shaped pyknotic nuclei were growing in sheet form or island form, and markedly hyalinized fascicles were observed between the alveolar walls of the atypical cells. Immunohistochemical stains revealed these tumor cells to be positive for epithelial cell markers but negative for myoepithelial ones. Considering the above findings, the tumor was diagnosed as CCC. The patient is currently free from disease 37 months after surgery.

Octacalcium phosphate and its collagen composite have been recognized as bone substitute materials possessing osteoconductivity and biodegradation properties. We evaluated the effectiveness of octacalcium phosphate and its collagen composite used for bone augmentation in major oral and maxillofacial surgeries in a clinical trial. Octacalcium phosphate and its collagen composite were used in cases of sinus floor elevation in 1- and 2-stage, socket preservation, cyst, and alveolar cleft procedures. A total of 60 patients were evaluated for effectiveness after the implantation of octacalcium phosphate and its collagen composite. Although sinus floor elevation in 1-stage, cyst, and alveolar cleft cases met the criteria for the judgment of success, sinus floor elevation in 2-stage and socket preservation groups did not meet the criteria in the initial evaluation. However, an additional evaluation for reconfirmation revealed the effectiveness of octacalcium phosphate and its collagen composite in those groups, and all evaluation results ultimately indicated the success of this clinical trial. Therefore, this clinical trial suggested that application of octacalcium phosphate and its collagen composite for oral and maxillofacial surgery was safe and effective and that octacalcium phosphate and its collagen composite could be a bone substitute candidate instead of autologous bone.

BACKGROUND: Although various reconstruction techniques are available for anterior cruciate ligament (ACL) injuries, a long recovery time is required before patients return to sports activities, as the reconstructed ACL requires time to regain strength. To date, several studies have reported use of mesenchymal stem cells in orthopaedic surgery; however, no studies have used adipose-derived stem cell (ADSC) sheets in ACL reconstruction (ACLR). HYPOTHESIS: ADSC sheet transplantation can improve biomechanical strength of the autograft used in ACLR. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 68 healthy Japanese white rabbits underwent unilateral ACLR with a semitendinosus tendon autograft after random enrollment into a control group (no sheet; n = 34) and a sheet group (ADSC sheet; n = 34). At 2, 4, 8, 16, and 24 weeks after surgery, rabbits in each group were sacrificed to evaluate tendon-bone healing using histological staining, micro-computed tomography, and biomechanical testing. At 24 weeks, scanning transmission electron microscopy of the graft midsubstance was performed. RESULTS: The ultimate failure load for the control and sheet groups, respectively, was as follows: 17.2 ± 5.5 versus 37.3 ± 10.3 (P = .01) at 2 weeks, 28.6 ± 1.9 versus 47.4 ± 10.4 (P = .003) at 4 weeks, 53.0 ± 14.3 versus 48.1 ± 9.3 (P = .59) at 8 weeks, 66.2 ± 9.3 versus 95.2 ± 43.1 (P = .24) at 16 weeks, and 66.7 ± 27.3 versus 85.3 ± 29.5 (P = .39) at 24 weeks. The histological score was also significantly higher in the sheet group compared with the control group at early stages up to 8 weeks. On micro-computed tomography, relative to the control group, the bone tunnel area was significantly narrower in the sheet group at 4 weeks, and the bone volume/tissue volume of the tendon-bone interface was significantly greater at 24 weeks. Scanning transmission electron microscopy at 24 weeks indicated that the mean collagen fiber diameter in the midsubstance was significantly greater, as was the occupation ratio of collagen fibers per field of view, in the sheet group. CONCLUSION: ADSC sheets improved biomechanical strength, prevented bone tunnel enlargement, and promoted tendon-bone interface healing and graft midsubstance healing in an in vivo rabbit model. CLINICAL RELEVANCE: ADSC sheets may be useful for early tendon-bone healing and graft maturation in ACLR.

Objectives: We aimed to evaluate the clinical value of an entire-circumferential intraoperative frozen section analysis (e-IFSA) for the complete resection of superficial squamous cell carcinoma (SCC) of the tongue. Materials and Methods: A total 276 specimens from 51 patients with pT1-2, N0, mucosal or submucosal invasion SCC were analyzed to evaluate the diagnostic accuracy of the e-IFSA and the added value of the e-IFSA to iodine staining. The e-IFSA results were compared with the final histologic results obtained using permanent sections. All specimens for the e-IFSA were taken over the entire circumference 5 mm outside from the iodine unstained areas. The outline of the main resected specimen after taking these outer mucosal specimens were defined as the surgical margins determined by iodine staining alone. Results: The e-IFSA results were in excellent agreement with final histological results (Cohen's kappa value: 0.85) and the e-IFSA showed high sensitivity (100%) and high negative predictive value (100%). The actual complete resection rate with an e-IFSA was 100% (51/51), and no patient required additional resection after surgery. In contrast, 10/51 patients (20%) patients showed residual atypical mucosal epithelium at or beyond the margin determined by iodine staining alone; this difference was statistically significant (P = 0.002). The 5-year local control rate and 5-year overall survival rate after this procedure were both 100%. Conclusion: An e-IFSA has additional value when performed in conjunction with iodine staining. An e-IFSA would be useful for achieving complete resection of superficial SCC of the tongue.

Abstract Currently, implants are utilized clinically for bone transplant procedures. However, if infectious osteomyelitis occurs at implant sites, removal of bacteria can be challenging. Moreover, altered blood flow at peri-implant infectious sites can create an anaerobic environment, making it more difficult to treat infection with antibiotics. Thus, it would be beneficial if implants could be modified to exhibit antibacterial activity, even in anaerobic conditions. Here, we show antibacterial activity of silver ions coated on titanium rods, even against the anaerobic bacteria Porphyromonas gingivalis (P. gingivalis), both in vitro and in vivo. Specifically, we implanted silver-coated or control uncoated titanium rods along with P. gingivalis in mouse femoral bone BM cavities and observed significantly inhibited P. gingivalis infection with silver-coated compared with non-coated rods, based on in vivo bio-imaging. Osteonecrosis by infectious osteomyelitis and elevation of the inflammatory factors C-reactive protein and IL-6 promoted by P. gingivalis s were also significantly reduced in the presence of silver-coated rods. Overall, our study indicates that silver ion coating of an implant represents a therapeutic option to prevent associated infection, even in anaerobic conditions or against anaerobic bacteria.

Background: Limited research is available regarding the role of nonoperative therapy in managing medication-related osteonecrosis of the jaw (MRONJ) as it relates to progression or resolution of disease. Purpose: The study purpose was to estimate the time to MRONJ stage improvement and risk for relapse among patients managed nonoperatively. Study Design, Setting, Sample: This retrospective cohort study included subjects diagnosed with MRONJ at Keio University Hospital between April 2012 and July 2024. Exclusion criteria included absence of a panoramic radiograph, prior operative therapy, or an observation period of less than 3 months. Predictor Variable: The predictor variable was a set of heterogeneous factors including age, sex, disease stage at the initial visit, presence of diabetes, use of steroid, radiographic findings, primary disease, type of bone-modifying agent (BMA), and BMA holiday before improvement. Disease stage after the stage improvement and BMA holiday after the disease improvement were included as covariates for evaluating the risk of relapse. Main Outcome Variable: The main outcome variable was therapeutic response measured as the time between initial treatment and MRONJ stage improvement, which was defined as an improvement of at least one stage. The secondary outcome was relapse measured as the time between maximal therapeutic response measured by MRONJ stage and worsening of the MRONJ stage. Analyses: The Fine-Gray subdistribution hazard model was used to estimate the cumulative incidence function (CIF) of outcomes, and Gray's test was used to compare CIF curves for relapse after stage improvement. Results: The sample was composed of 118 subjects with a mean age of 73.4 (±10.03), 54 (45.8%) were male, and the median interquartile range (IQR) duration of follow-up was 23 (11 to 32.5) months. During the study interval, 84 (71.2%) subjects achieved stage improvement, resulting in a 12-month CIF of 0.594. After achieving maximal therapeutic effect, 34 subjects (40.5%) experienced relapse. Incomplete healing after the stage improvement was associated with a higher risk of relapse (P = .0016), with a CIF of 0.661 at 36 months. Conclusions and Relevance: More than half of the subjects experienced stage improvement within 12 months. Incomplete healing following initial intervention may increase the risk of relapse.

Abstract Introduction Osteoclasts and foreign body giant cells (FBGCs) are multi-nuclear cells established by fusion of their mono-nuclear forms. Multi-nucleation via cell–cell fusion is a common characteristic of osteoclasts and FBGCs, and Dendritic Cell-Specific Transmembrane Protein (DC-STAMP) and Osteoclast Stimulatory Transmembrane Protein (OC-STAMP) are both required for the process. Thus, it is thought that DC-STAMP and OC-STAMP interaction likely induces this fusion, but details of these mechanisms are not clear. Materials and methods We crossed DC-STAMP knockout (KO) with OC-STAMP KO mice to obtain DC-STAMP/OC-STAMP doubly deficient (DKO) mice. Osteoclasts and FBGC common progenitors were isolated from wild-type (WT), DC-STAMP KO, OC-STAMP KO or DKO mice. We then set up 4 co-culture systems: (1) WT with DC-STAMP KO cells, (2) WT with OC-STAMP KO cells, (3) WT with DKO cells, and (4) DC-STAMP KO with OC-STAMP KO cells to induce osteoclast or FBGC formation. We evaluated osteoclast and FBGC formation by TRAP and May–Gruenwald Giemsa staining, respectively. Finally, we performed bone morphometric analysis of WT, DC-STAMP KO, OC-STAMP KO, and DKO mice. Results Cell–cell fusion occurs normally in co-cultures of DC KO with WT cells, OC KO with WT cells, and DKO with WT cells in both osteoclast and FBGC-inducing conditions. By contrast, co-cultures of DC-STAMP KO with OC-STAMP KO cells did not show cell–cell fusion. Bone morphometric analysis revealed enhanced bone formation in DKO mice. Conclusion DC-STAMP and OC-STAMP cooperate to promote osteoclast and FBGC cell–cell fusion. DC-STAMP and OC-STAMP doubly deficient mice exhibit increased osteogenesis.

Abstract Peri-implantitis, an inflammatory condition caused by bacterial infection around an implant, is currently the leading cause of implant failure. Porphyromonas gingivalis ( P. gingivalis ), an anaerobic bacterial pathogen associated with periodontitis, is known to play a key role in peri-implantitis. To address this issue, the present study examined the antibacterial properties of silver ion (Ag + )-coated titanium implants against P. gingivalis and their ability to prevent bone loss. Ag + -coated implants, i.e., Ti implants coated with Ag + ions on a hydroxyapatite film chelated with inositol hexaphosphate, demonstrated significant antibacterial activity against P. gingivalis in the Ti wire configuration in inhibition zone assays ( n  = 4 per group). Furthermore, in a murine model of ligature-induced peri-implantitis, these implants significantly reduced alveolar bone resorption compared to uncoated titanium controls. This preclinical study suggests that applying an Ag + coating to dental implants is an effective strategy for preventing P. gingivalis –induced peri-implantitis. In the control group, bone loss of 19–25% relative to baseline was observed at day 28, whereas the Ag + -coated group exhibited only 15–20% bone loss ( n  = 8 per group per time point). These findings suggest the potential of Ag + coating as a preventive strategy against peri-implantitis-associated bone loss.

61歳男。右上顎第2大臼歯遠心部歯肉潰瘍精査依頼および疼痛と主訴とした。初診時には右上顎に潰瘍を伴う歯肉の腫脹を認め、右上顎歯肉癌(T2N0M0、扁平上皮癌)と診断された。化学療法と外科的切除を行い、病理組織診断は中分化型・浸潤様式2型の扁平上皮癌であった。1次癌の術後1年2ヵ月に左下顎第1大臼歯部頬側歯肉にびらん形成と周囲の白斑を認め、左下顎歯肉癌(T2N0M0、扁平上皮癌)と診断された。化学療法と外科的切除を行い、病理組織診断は中分化型扁平上皮癌であった。2次癌の術後8年10ヵ月に右下顎第2小臼歯・第1大臼歯舌側歯肉に外向性の腫瘤を認め、右下顎歯肉癌(T2N0M0、扁平上皮癌)と診断された。化学療法と外科的切除を行い、現在まで再発・転移を認めず経過良好である。自験例は12年間にわたって上下顎歯肉に異所性、異時性に発生した典型的な多発性癌であった。