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BackgroundOnline teaching is being widely adopted to achieve medical teaching objectives during the COVID-19 pandemic. To explore the dental virtual clerkship so as to continue the education of final-year dental undergraduate interns, combined mode of courses including small private online course, problem-based learning, online dental practice broadcasting and dental practice based on relatives’ or friends’ oral health management were applied for clerkship education for final-year interns.MethodsCombined courses of virtual clerkship was conducted from March to May, 2020 for final-year interns, while online preclerkship curriculum teaching was conducted for non-final-year students. Using the online students’ engagement scale (OSE), Biggs’ revised two-factor version of the study process questionnaire (R-SPQ-2F), student engagement and study process were evaluated for both. Teaching efficacy were evaluated via teachers' sense of efficacy scale (TSES) as well. ResultsStudents’ engagement was higher in final-year students, especially the emotion and participation categories (P0.05).ConclusionThis combined mode of courses on dental virtual clerkship could be potentially applied during the pandemic or be supplementary for traditional by-chair clerkship after the pandemic.

Background Excessive inflammatory reactions participate in primary Sjögren’s syndrome (pSS) progression. In addition, biological clock genes have been detected in the salivary glands, which indicates that clock genes regulate the growth and development of the salivary glands as well as the quality and quantity of saliva secretion. Melatonin is an amine hormone secreted by the pineal gland that has many physiological functions, such as regulating immunity and correcting disorder in the biological clock rhythm. The purpose of this study was to clarify the correlation between pSS and the biological clock rhythm and explore the possibility of applying melatonin to treat pSS. Methods Melatonin (10 mg/kg/d or 15 mg/kg/d) or vehicle was administered to NOD/Ltj mice by intraperitoneal injection for 4 weeks. Clock gene expression levels in labial gland biopsy specimens from pSS patients and submandibular gland specimens from mice were measured by Western blotting (WB) and RT-PCR. The salivary flow rate of mice was measured at 12, 14, and 16 weeks. The severity of lymphocyte infiltration in the salivary glands was analysed by haematoxylin and eosin (H&E) staining. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemical staining were used to detect the expression levels of related inflammatory factors in mice. The percentages of Th17, Th2, and Treg cells were analysed by flow cytometry. Results There was a distinct expression profile for clock genes in pSS patients compared with controls. Continuous melatonin administration improved salivary gland function in NOD/Ltj mice, with decreased lymphocyte infiltration in the submandibular glands and reduced related inflammatory factor expression in the serum and salivary glands. Melatonin treatment skewed T cells towards the Treg and Th2 subsets while suppressing Th17 responses. Additionally, melatonin administration regulated clock gene expression in NOD/Ltj mice. Conclusion pSS pathogenesis and progression are correlated with abnormal circadian gene expression. Melatonin improves the hypofunction of the salivary glands and inhibits the inflammatory development of pSS in NOD/Ltj mice. This study provides a theoretical basis and potential approach for the clinical prevention and treatment of pSS.