Changes in oral pathology teaching methods during the COVID-19 pandemic and the impact on student performance (oral pathology teaching changes during the COVID-19 pandemic).

Abstract Background/purpose: Coronavirus disease 2019 (COVID-19) has influenced the dental education in Osaka Dental University. The purpose of this study was to summarize the impact of COVID-19 on student performance and the current more appropriate teaching methods by comparing the changes in various oral pathology exam results before and after COVID-19. Materials and methods: The experimental and control groups consisted of second year students in the department of dentistry at our university for the years 2019 (136 people) and 2020 (125 people). The impact of different teaching methods on student performance was compared by calculating the mean scores and percentage of failures on various exams and whether or not class credits were earned between the two years. A t test was used to determine statistical significance. Results: The mean scores on the mini-tests were lower in 2020 than in 2019, while the average score of the intermediate exam and the number of students receiving class credits were higher. The mean scores on the practical and unit exams were not statistically significant between the years, but the failure rate on both exams was higher in 2019 than in 2020. Conclusion: COVID-19 had impacts on student performance. A comparison of the mean scores on the exams revealed that the use of microscopy, oral questions, and online animations contributed to improved performance on different exams. Therefore, to promote students' understanding and retention of memorized knowledge of oral pathology, the use of microscopes will be resumed whenever possible, as well as continuation with oral questions and online animations.

Bone augmentation with a prototype coral exoskeleton-derived bone replacement material applied to experimental one-wall infrabony defects created in alveolar bone.

Bone regeneration requires cells, growth factors, and scaffolds that should have biocompatibility, porosity, and physical strength. Therefore, coral granules (CG) with diameters of 600-1,000 µm were prepared as a potential graft material from cultured edaphic thermostable corals. X-ray and electron microscopy characterization revealed that CGs were porous and permeable with lumen diameters of approximately 200 µm. Human periodontal ligament fibroblasts showed significantly increased mitochondrial activity in culture seven days after adding CG. After CG filling into an experimentally created one-wall infrabony defect in a beagle dog jawbone, the defect almost completely disappeared within approximately 8 weeks, and bone tissue growth was observed in the replacement area. This could indicate extremely rapid healing of a bone defect previously considered incapable of self-healing. Based on stable supply of cultured coral (Montipora digitata), CG is potentially an ideal replacement material for alveolar and jawbone defects.

Biocompatibility of a High-Plasticity, Calcium Silicate-Based, Ready-to-Use Material.

The Bio-C Sealer is a recently developed high-plasticity, calcium-silicate-based, ready-to-use material. In the present study, chemical elements of the materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of the Bio-C Sealer was investigated using cytotoxicity tests and histological responses in the roots of dogs' teeth. XRD, SEM, and FTIR produced hydrated calcium silicate in the presence of water molecules. In addition, FTIR showed the formation of calcium hydroxide and polyethylene glycol, a dispersing agent. The 1:4 dilutions of Bio-C Sealer presented weaker cytotoxicity than the Calcipex II in an in vitro system using the V-79 cell line. After 90 d, the periradicular tissue response of beagle dog roots was histologically evaluated. Absence of periradicular inflammation was reported in 17 of the 18 roots assessed with the Bio-C Sealer, whereas mature vertical periodontal ligament fibers were observed in the apical root ends filled with the Bio-C Sealer. Based on these results and previous investigations, the Bio-C Sealer is recommended as an effective root-end filling material. These results are relevant for clinicians considering the use of Bio-C Sealer for treating their patients.

Palmitate induces apoptosis and inhibits osteogenic differentiation of human periodontal ligament stem cells.

OBJECTIVE: The aim of the present study was to investigate the effect of palmitate on human periodontal ligament stem cells (PDLSCs). DESIGN: PDLSCs were isolated from the third molars of healthy adult donors, and cultured in normal or osteogenic medium supplemented with palmitate (0, 100, or 250 µM) for 21 days. Cell proliferation was evaluated by measuring the amount of formazan at 6, 24, 48, and 72 h. Apoptosis was detected by ELISA and terminal deoxynucleotidyl transferase dUTP nick end labeling assay at days 3 and 7. Osteogenic differentiation was evaluated by measuring the alkaline phosphatase (ALP) activity, production of procollagen type I C-peptide and osteocalcin, mineralization, and mRNA expression of Runx2 at days 3, 7, 14, and 21. In addition, mRNA expression of IL-6 and IL-8 was measured at day 3. RESULTS: Palmitate inhibited the proliferation, ALP activity, production of procollagen type I C-peptide and osteocalcin, mineralization, and mRNA expression of Runx2 in the cultured PDLSCs. Palmitate also induced apoptosis and mRNA expression of IL-6 and IL-8 in the PDLSCs. CONCLUSIONS: The results of the present study demonstrate that palmitate induces apoptosis and inhibits osteogenic differentiation of PDLSCs. These findings may help clarify the relationship between palmitate and periodontal tissue regeneration.

Diagnostic usefulness of panoramic imaging of the pterygopalatine fossa: case of a schwannoma causing pterygopalatine fossa expansion.

The pterygopalatine fossa is a small area between the posterior wall of the maxillary sinus and the anterior surface of the pterygoid process of the sphenoid bone. The pterygopalatine fossa can be seen clearly on panoramic imaging. We present the case of a 57-year-old man who exhibited right pterygopalatine fossa expansion on panoramic imaging. Computed tomography (CT), magnetic resonance imaging (MRI), and panoramic imaging all showed a tumor at the right pterygopalatine fossa in this patient. CT indicated that the tumor replaced right retromaxillary fat and displaced the posterior wall of the maxillary sinus. On MRI, the tumor showed intermediate signal intensity at the paranasal area on T1-weighted images, and variable intermediate and high signal intensities on fat-suppressed T2-weighted images. It was eventually diagnosed as a schwannoma. Thus, panoramic imaging can be used for disease screening at the posterior border of the maxilla. Our conclusion is based on this report of a patient with a schwannoma at the posterior wall of the maxillary sinus, which panoramic imaging revealed to have pterygopalatine fossa expansion.

Differential diagnosis of well-differentiated squamous cell carcinoma from non-neoplastic oral mucosal lesions: New cytopathologic evaluation method dependent on keratinization-related parameters but not nuclear atypism.

BACKGROUND: The cytology of oral squamous cell carcinoma (SCC) is challenging because oral SCC cells tend to be well differentiated and lack nuclear atypia, often resulting in a false negative diagnosis. The purpose of this study was to establish practical cytological parameters specific to oral SCCs. METHODS: We reviewed 123 cases of malignancy and 53 of non-neoplastic lesions of the oral mucosa, which had been diagnosed using both cytology and histopathology specimens. From those, we selected 12 SCC and 4 CIS cases that had initially been categorized as NILM to ASC-H with the Bethesda system, as well as 4 non-neoplastic samples categorized as LSIL or ASC-H as controls, and compared their characteristic findings. After careful examinations, we highlighted five cytological parameters, as described in Results. Those 20 cytology samples were then reevaluated by 4 independent examiners using the Bethesda system as well as the 5 parameters. RESULTS: Five cytological features, (i) concentric arrangement of orangeophilic cells (indicating keratin pearls), (ii) large number of orangeophilic cells, (iii) bizarre-shaped orangeophilic cells without nuclear atypia, (iv) keratoglobules, and (v) uneven filamentous cytoplasm, were found to be significant parameters. All malignant cases contained at least one of those parameters, while none were observed in the four non-neoplastic cases with nuclear atypia. In reevaluations, the Bethesda system did not help the screeners distinguish oral SCCs from non-neoplastic lesions, while use of the five parameters enabled them to make a diagnosis of SCC. CONCLUSION: Recognition of the present five parameters is useful for oral SCC cytology. Diagn. Cytopathol. 2017;45:406-417. © 2017 Wiley Periodicals, Inc.

High Glucose Concentrations Suppress the Proliferation of Human Periodontal Ligament Stem Cells and Their Differentiation Into Osteoblasts.

BACKGROUND: Diabetes mellitus (DM) is a major risk factor for periodontal disease and affects various cellular functions. Periodontal ligament stem cells (PDLSCs) play an important role in periodontal tissue regeneration; however, the effect of hyperglycemia on PDLSCs is unclear. The aim of this study is to investigate whether hyperglycemia affects periodontal tissue regeneration, using human PDLSCs and high-glucose medium as a model of DM. METHODS: PDLSCs were obtained from healthy adult human mandibular third molars. Cell proliferation, osteoblastic differentiation, and proinflammatory cytokine expression were investigated by culturing PDLSCs in media supplemented with four different glucose concentrations representative of control patients (5.5 mM), patients with postprandial or controlled DM (8.0 mM), and patients with uncontrolled DM (12.0 and 24.0 mM). The molecular effects of hyperglycemia on PDLSC physiology were examined with a focus on the nuclear factor (NF)-(κB signaling pathway. The involvement of NF-κB was investigated with a specific NF-κB inhibitor in PDLSCs under hyperglycemic conditions. RESULTS: High glucose levels inhibited PDLSC proliferation and differentiation into osteoblasts but induced NF-κB activation and subsequent interleukin (IL)-6 and IL-8 expression. Treatment with an NF-κB inhibitor rescued the defects in cell proliferation and osteoblastic differentiation and inhibited the IL-6 expression caused by the high-glucose environment. CONCLUSION: The results of this study demonstrate that hyperglycemia inhibits human PDLSC proliferation and osteoblastic differentiation.

Simultaneous occurrence of keratocystic odontogenic tumor and ameloblastoma in the mandible: A case report.

Keratocystic odontogenic tumors (KCOTs) and ameloblastomas are benign odontogenic tumors that primarily occur in the molar region of the mandible. However, it is uncommon for these tumors to arise simultaneously in a patient's jaw. The present study reported the diagnostic process and features of a rare case of the simultaneous occurrence of KCOT and ameloblastoma in the mandible of a 45-year-old male. Image-based diagnosis was challenging due to several conditions, including the intactness of the teeth and bone cortex as well as the sizes and locations of the lesions. Based on radiographic evidence, the patient was initially misdiagnosed and underwent a biopsy for a radicular cyst and a simple bone cyst prior to the correct diagnoses of KCOT and ameloblastoma, respectively. In addition, the present study discussed the diagnostic process of the present case and reviewed previous literature regarding the simultaneous occurrence of benign tumors of the jaw.

Porphyromonas gingivalis LPS inhibits osteoblastic differentiation and promotes pro-inflammatory cytokine production in human periodontal ligament stem cells.

OBJECTIVE: Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) induces pro-inflammatory cytokines, such as interleukin-1 ß (IL-1ß), IL-6, and IL-8, which induce periodontal tissue destruction. Periodontal ligament stem cells (PDLSCs) play an important role in periodontal tissue regeneration and are expected to have future applications in cellular therapies for periodontitis. However, no studies have examined the effects of P. gingivalis LPS on PDLSCs. The aim of this study was to investigate how P. gingivalis LPS affects the osteoblastic differentiation and pro-inflammatory cytokine production of PDLSCs. DESIGN: PDLSCs were obtained from healthy adult human mandibular third molars. The identification of PDLSCs was confirmed by immunohistochemical evaluations of the mesenchymal stem cell markers STRO-1 and SSEA-4. Cell proliferation and osteoblastic differentiation were investigated by culturing the PDLSCs in a normal or osteogenic medium with P. gingivalis LPS (0, 1, or 10µg/mL) and then measuring the alkaline phosphatase (ALP) activity and the production of collagen type 1 Alpha 1 (COL1A1), osteocalcin production, and mineralisation. Additionally, we examined the production of IL-1ß, IL-6, and IL-8 in the PDLSCs. RESULTS: P. gingivalis LPS inhibited the ALP activity, COL1A1 and osteocalcin production, and mineralisation in the PDLSCs, which are positive for STRO-1 and SSEA-4. P. gingivalis LPS also promoted cell proliferation and produced IL-1ß, IL-6, and IL-8. CONCLUSIONS: This study provides the first findings that P. gingivalis LPS inhibits osteoblastic differentiation and induces pro-inflammatory cytokines in PDLSCs. These findings will help clarify the relationship between periodontitis and periodontal tissue regeneration.

A synthetic oligopeptide derived from enamel matrix derivative promotes the differentiation of human periodontal ligament stem cells into osteoblast-like cells with increased mineralization.

BACKGROUND: In a previous study, the authors obtained a synthetic peptide (SP) for useful periodontal tissue regeneration. Periodontal ligament stem cells (PDLSCs) have multiple potentiality to contribute to tissue regeneration. The aim of this experiment is to investigate the effect of SP on human PDLSCs. METHODS: Periodontal ligament cells were obtained from healthy adult human third molars and used to isolate single PDLSC-derived colonies. The mesenchymal stem cell nature of the PDLSCs was confirmed by immunohistochemical evaluation of STRO-1 expression. Proliferation and osteoblastic differentiation were investigated by culturing PDLSCs in normal or osteogenic medium with and without SP (100 ng/mL). Osteoblast differentiation was assessed by measuring alkaline phosphatase (ALP) activity, osteocalcin production, mRNA expression of osteonectin, mineralization, and calcium deposition. RESULTS: Isolated PDLSCs were immunohistochemically positive for vimentin and STRO-1 and negative for cytokeratin. A greater number of calcified nodules were observed in osteogenic medium culture with SP than without. In the early and later stages of PDLSC culture with SP, osteonectin production and osteocalcin production were increased. SP in culture with osteogenic medium significantly enhanced proliferation of PDLSCs, as well as ALP activity, expression of osteonectin, osteocalcin production, formation of calcified nodules, and mineralization. CONCLUSIONS: SP enhances the formation of calcified nodules and osteocalcin production in the culture of PDLSCs into osteoblast-like cells and is a useful material for periodontal tissue regeneration.

Analysis of eosinophilic round bodies formed after injection of enamel matrix derivative into the backs of rats.

BACKGROUND: Enamel matrix derivative (EMD) is used in dental clinics for the regeneration of alveolar bone. Its effects have not yet been clarified, although it induces eosinophilic round bodies (ERBs) and cartilage formation at the injection site. The objective of this experiment was to examine the histopathologic and biochemical properties of ERBs formed after EMD injection. METHODS: The backs of Sprague-Dawley rats injected with various concentrations of EMD were examined histopathologically. For biochemical examinations, ERBs were microdissected out from the sections. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS), and database analysis of ERBs were carried out. RESULTS: The histopathological findings were consistent with a foreign body reaction. Numerous ERBs were observed 7 days after injection of 30.0 mg/ml EMD. Histopathologically, ERBs did not contain polysaccharide, amyloid, or hemosiderin. The cells surrounding ERBs were not macrophages or vascular endothelial cells. SDS-PAGE of the microdissected ERBs revealed an intense band at around the 40-kDa region. MALDI-TOF MS showed that the spectrum for ERBs has only a single strong ion intensity. Analysis of the amino acid sequence revealed that the ERBs were composed of various molecular fragments, which all contained an identical seven amino acid sequence. In addition, these peptides are a component of amelogenin. CONCLUSIONS: A high concentration of EMD induces ERBs that consist of a 40-kDa protein which includes a constituent part of amelogenin. The ERBs (or remaining EMD) might promote mesenchymal cell differentiation into hard tissue-forming cells around the EMD injection site.

Bone repair analysis in a novel biodegradable hydroxyapatite/collagen composite implanted in bone.

The purpose of this study was to evaluate a biodegradable hydroxyapatite/collagen composite and to examine the use of the calcium ion contained for bone formation and growth. Surgical holes were prepared in the femora and tibiae of beagle dogs, and were filled with the hydroxyapatite/collagen composite labeled with alizarin red. After 4 weeks, calcein was administered to the experimental dogs. After 1 additional week, the femora and tibiae were removed surgically and fixed in formalin. Light microscopy and confocal laser scanning microscopy were used to examine the surgical holes with their implanted materials and the surrounding bone. There were only a few inflammatory cells adjacent to the hydroxyapatite/collagen composite. The newly formed bone in the cortical bone was stained with calcein, which binds to serum calcium, and new bone near the hydroxyapatite/collagen composite in the holes was stained positive for alizarin red, which binds to the calcium in the hydroxyapatite/collagen composite. In addition, osteoblasts near the hydroxyapatite/collagen composite as well as newly formed bone adjacent to the osteoblasts showed alizarin red staining, but the new bone at a distance from the hydroxyapatite/collagen implant reacted only to calcein staining. These results, using the tissue labeling method with calcein and alizarin red, suggested that the calcium bound to the alizarin red released from the hydroxyapatite/collagen composite materials might have been translocated to sites of new bone formation. The present experiment showed that the novel hydroxyapatite/collagen composite is a useful implant material for bone augmentation and that the calcium in the newly formed bone might have been released from the implant.

E1A activates transcription of p73 and Noxa to induce apoptosis.

p73, a member of the p53 family of proteins, transcriptionally activates a number of genes involved in the control of cell cycle and apoptosis. Overexpression of p73 was detected in a large number of primary head and neck cancers, and in the established cell lines examined, these all contained inactivating p53 mutations. The significance of p73 overexpression in the pathogenesis of head and neck cancer is currently unclear. We have shown that the expression of adenovirus 5 E1A in a panel of head and neck cancer cell lines induces apoptosis independently of their p53 status. In this study we examined the role of p73 and its transcriptional targets in E1A-mediated induction of apoptosis. E1A expression resulted in significant activation of the TAp73 promoter but had no effect on the alternative, DeltaNp73 promoter. E1A also increased expression of endogenous TAp73 mRNA and protein. E1A mutants lacking the p300- and/or pRB-binding sites showed reduced ability to activate the TAp73 promoter. Additionally, mutations in the E2F1-binding sites in the TAp73 promoter impaired activation by E1A. Importantly, expression of the 13S isoform of E1A substantially induced the p53 apoptotic target Noxa in several p53-deficient cancer cell lines. Our results indicate that E1A activation of p73 and the p53 apoptotic target Noxa can occur in the absence of a functional p53. This activation is likely to play a key role in the mechanism of p53-independent apoptosis induced by E1A in some cancers and may provide an avenue for future cancer therapies.