[A survey on the application of online and offline blended teaching in microendodontics].

Objective: To evaluate the effect of online and offline blended teaching in microendodontics, attempting to promote the widespread application of blended teaching mode in Operative Dentistry and Endodontics. Methods: A questionnaire survey was carried out among 865 trainees who attended the blended teaching in microendodontics combined the online theory curriculum and offline practice training from April 6 to 28 in 2022, organized by Department of Operative Dentistry and Endodontics, Hospital of Stomatotogy, Sun Yat-sen University. The content of questionnaire included trainees' basic information as well as their perspectives and expectations on the teaching mode. Data was analyzed by SPSS 24.0 and Chi-square test was used for enumeration data. Results: A total of 855 trainees participated in the valid survey with the effective recall rate of 98.8% (855/865), 50.3% (430/855) of which were young people in 18-30 years old. Their working period ranged from 0.5 to 40 years. Physicians and physician assistants occupied 40.9% (350/855) and 32.9% (281/855), respectively. And the intermediate and senior titles accounted for 26.2% (224/855). The proportion of trainees who had used and never used dental operative microscope (DOM) were 70.5% (603/855) and 29.5% (252/855), respectively. The blended teaching in microendodontics was universally approved by the trainees, which showed more superiority in the improvement of learning efficiency and interest, comprehension of knowledge as well as practical ability, etc., compared to the traditional offline teaching. For the current stomatology education, trainees were inclined to choose the blended teaching mode combining online theory curriculum and offline practice training, whereas 41.3% (353/855) and 39.6% (339/855) of trainees agreed that the teaching effectiveness was likely influenced by the condition and frequency of the offline training, respectively. Besides, significant differences were detected in the question about the factors affecting the blended teaching effectiveness of microendodontics between the trainees who had used and not used DOM (χ²=13.37, P=0.004). Conclusions: The application of online and offline blended teaching in microendodontics was affirmed to have some advantages, and it should be considered that the discrepancy in the level of expertise among trainees probably influenced the teaching effectiveness, which may promote the quality and effect of teaching, the spread and sharing of microendodontics, and provide experience and reference for the practice teaching of Operative Dentistry and Endodontics.

[A preliminary study on the construction and application of the smart classroom teaching mode in endodontics].

Objective: To evaluate the application effect of smart classroom teaching mode in undergraduate teaching of endodontics. Methods: Through micro-lecture and massive open online course which were closely integrated with clinical practice and frontier advances, we build a new smart classroom teaching mode of endodontics relying on information technology such as the medical education cloud APP platform. The mode was applied to the undergraduate teaching of grade 2017 (110 students) and grade 2018 (107 students) in 2020 and 2021 respectively (experimental group). The theoretical examination was conducted for the grade 2016 (control group, 111 students applied traditional teaching methods) in 2019, and for two experimental grades in 2020 and 2021 respectively. A questionnaire survey was conducted for the 2018 undergraduates to investigate the experience of the smart classroom teaching mode, and the application effect of the smart classroom teaching mode was evaluated by comparing the offline theoretical test scores of grades 2016, 2017 and 2018. Results: The results of the questionnaire showed that students in grade 2018 recognized the overall form of smart classroom teaching mode, and 75.2% (79/105) of the students satisfied with the teaching process, considering that it could enhance learning interest and enthusiasm, improve self-learning ability, facilitate the understanding and memory of knowledge points, as well as increase the extension and expansion of professional knowledge. Thirty-seven point one percent (39/105) of the students thought that smart classroom teaching mode was not conducive to the interaction between teachers and students and couldn't improve learning efficiency. Comparing the final theoretical examination scores of students in three years, it was found that the average scores of 2021 (78.79±9.88) and 2020 (76.45±8.33) were significantly higher than that of 2019 (67.67±10.58) (t=6.77, P<0.001; t=8.51, P<0.001). The average score in 2021 was higher than that in 2020, although the difference was not significant (t=1.79, P=0.223). Conclusions: The application of smart classroom mode improved the teaching effect of endodontics, which is worthy of further promotion to provide a positive reference in improving the educating effects of oral medicine.

[Mechanisms of fosfomycin resistance of extended-spectrum ß-lactamases-producing Escherichia coli and Klebsiella pneumoniae].

Objective: To study the in vitro activity of fosfomycin to extended-spectrum ß-lactamases (ESBLs)-producing Escherichia coli and Klebsiella pneumoniae and to explore the mechanisms of fosfomycin resistance. Methods: A total of 1 052 ESBLs-producing E. coli(ESBL-EC) and K. pneumoniae(ESBL-KP) isolates were collected from bloodstream infections of 28 hospitals of 22 provinces and municipalities, which were stored by our laboratory.Minimum inhibitory concentrations (MICs) of fosfomycin against these clinical isolates were determined by agar dilution methods according to the Clinical and Laboratory Standards Institute (CLSI)(2015). The genes related to fosfomycin resistance were confirmed by Polymerase Chain Reaction (PCR) and sequencing. Results: The susceptibility rates of ESBL-EC and ESBL-KP isolates to fosfomycin were 91.3% (818/896) and 91.7% (143/156), respectively. A total of 91 fosfomycin-non-susceptible isolates were detected, of which 73 (80.2%) isolates carried fosA3 genes.Amongst 18 fosA3-negative isolates, 16 isolates were detected to have chromosomal mutations or insertion inactivation, while the rest two isolates had not been detected any resistant mechanisms. Conclusions: Fosfomycin shows great in vitro antimicrobial activity to ESBL-EC and ESBL-KP. The primary mechanism of fosfomycin-non-susceptible isolates is fosA3 gene.Chromosomal mutations may also involve in the fosfomycin resistance.

[Naked cuticle homolog 2 positively regulates the osteogenic differentiation of rat dental follicle cells].

Objective: To examine the expression of naked cuticle homolog 2 (Nkd2) in the process of root development and osteogenic differentiation of dental follicle cells of rat (rDFC), in order to explore the molecular mechanisms of Nkd2 on the osteoblast differentiation of rDFCs. Methods: Immunohistochemical analysis was used to detect the expression of Nkd2 in the base dental follicle of the mandibular first molar of rat at 1, 3, 5, 7, 9, 11 and 13 days postnatal. Mineralization nodule formation of rDFCs was detected by alizarin red staining and cetylpyridine. The change of Nkd2 during osteogenic differentiation of rDFCs was evaluated by Western blotting and the associations between Nkd2 and osteogenic cytokines of alkaline phosphatase (ALP), Runt-related transcription factor-2 (RUNX2) and osteocalcin (OCN) were examined. The rDFCs were transfected with small interfering RNA (siRNA) to knock down the expression of Nkd2 and Western blotting and quantitative real-time PCR (qPCR) were adopted to explore the effects of Nkd2 on osteogenic differentiation by detecting variations of Nkd2 and osteogenic factors ALP, RUNX2, OCN among silencing group (Si), negative control RNA group (Nc) and mock control group (Mock), respectively. Results: The expression of Nkd2 in the base dental follicle of the mandibular first molar of rat was time dependent. Mineralization nodules of rDFCs and absorbance of cetylpyridine after osteogenic induction increased gradually (the absorbances of cetylpyridine were 0 week: 0.017±0.005, 1 week: 0.702±0.044, 2 weeks: 1.812±0.531, 3 weeks: 2.767±0.253, respectively). Results of Western blotting showed that Nkd2 (1.60±0.23) of mineralization group was significantly higher than that of control group (1) (P<0.05) at the early stage of osteogenic differentiation along with the expression of other osteogenic factors. The protein and mRNA of Nkd2 and osteogenic factors were significantly decreased in Si group compared with Nc and Mock groups (P<0.05), and no changes between Nc and Mock groups were observed. The changes of protein in Si, Nc and Mock groups were Nkd2: 0.42±0.10, 1.12±0.07, 1, ALP: 0.70±0.15, 1.11±0.14, 1, RUNX2: 0.58±0.08, 0.93±0.08, 1 and OCN: 0.64±0.06, 0.99±0.02, 1, respectively. The mRNA variances in Si, Nc and Mock groups were Nkd2: 0.39±0.05, 0.96±0.10, 1, ALP: 0.15±0.13, 1.01±0.07, 1, RUNX2: 0.39±0.31, 0.97±0.13, 1, OCN: 0.17±0.08, 1.08±0.21, 1, respectively. Conclusions: Nkd2 participates in the root development process in rat and may acts as a positive role in the early stage of osteogenic differentiation of rDFCs in rat.

[The activity of moxalactam against Enterobacteriaceae and anaerobia in vitro].

OBJECTIVE: To observe the antibacterial activity of moxalactam against Enterobacteriaceae bacteria and anaerobic bacteria in vitro, and to compare with other antibacterial drugs, for providing experimental basis for the clinical application of moxalactam. METHODS: Minimum inhibitory concentrations (MICs) of moxalactam and other antibacterial agents against 491 Enterobacteriaceae spp. and anaerobic spp.collecting from clinical settings were determined by agar dilution methods and E-test strips according to the Clinical and Laboratory Standards Institute (CLSI)(2014). RESULTS: Moxalactam showed great antibacterial activity to Enterobacteriaceae spp., including ESBLs-producing Escherichia coli, Klebsiella pneumoniae, and Proteus spp., with the MIC(50), MIC(90), and susceptibility rates of 0.25-4 mg/L, 0.5-8 mg/L, and >90%, respectively. The susceptibility rates of Enterobacteriaceae with ESBLs-producing or non-ESBLs-producing to imipenem and meropenem were both higher than 90%. The susceptibility rates of ESBLs-producing Escherichia coli, Klebsiella pneumoniae, and Proteus spp.to piperacillin/tazobactam and cefoperazone/sulbactam were 90%, 68%, 53% and 76%, 66%, 76.6%, respectively, while the susceptibility rates of non-ESBLs-producing Escherichia coli, Klebsiella pneumoniae, and Proteus spp.were all more than 95%. The susceptibility rates of Enterobacter spp. and other Enterobacter to piperacillin/tazobactam were 80%, 80%and that to cefoperazone/sulbactam were 80%, 76.7%, respectively.The MICs range of moxalactam on anaerobic spp.was from ≤0.064 to >256 mg/L, while MIC(50) was 2 mg/L and MIC(90) was 64 mg/L. CONCLUSIONS: Moxalactam showed well activity against ESBLs-producing and non-ESBLs-producing Enterobacteriaceae and anaerobia.