Objective:To investigate the ability of fluoride toothpaste and fluoride varnish on enamel remineralization and acid resist-ance.Methods:Enamel specimens were prepared from bovine incisors,and were randomly divided into 4 groups(n=3)after acid-etching by 37%phosphoric acid.Specimens in group A(control)was processed daily with normal saline;those in group B and C were treated once with Duraphat varnish and Fluor Protector varnish respectively;in group D was daily processed with fluoride toothpaste. All specimens were incubated in artificial saliva for 2 weeks.Then all specimens received acid-etching again.Micro-hardness test, SEM observation and image analysis were performed before and after each step.Results:After 2 weeks of processing,no remineraliza-tion was found in group A.Varnish layers were observed on the surface of specimens in group B and C.In group D remineralization was detected on the enamel surface.After re-etching,micro-hardness decreased in group A and D.Fluoride varnish layers in group B and C showed strong resistance to acid-etching.After re-etching,area of micro-holes in group A and D increased(P<0.05 ),but that in group D was smaller than in the control(P<0.05).No micro-hole was observed in group B and group C.Conclusion:Protec-tive layer formed on the enamel surface by fluoride varnish is resistant to acid-etching and promotes enamel remineralization.Fluoride toothpaste application can promote enamel remineralization,but with less resistance to acid.

Objective:To explore the application effect of flipped classroom model based on Simodont dental training system in the standardized training teaching of prosthodontics.Methods:The control experiment was used in this study. Seventy two students from Batch 2018 and Batch 2019 of Stomatology Hospital of Air Force Medical University were selected and randomly divided into experimental group (flipped classroom model based on Simodont dental training system) and control group (Simodont dental training system training mode after traditional teaching), with 18 students every academic year in each group. Questionnaire survey was conducted to evaluate the teaching effect, and the results of after-class theory test and practical computer test were compared between the two groups. SPSS 20.0 was used for chi-square test and t test. Results:The experimental group was better than the control group in enhancing classroom interest, improving the ability of independent analysis and problem-solving, and cultivating the ability of cooperation and expression ( P<0.05). The scores of after-class theory test and practical computer test in the experimental group [(23.36±0.21) points and (90.56±0.52) points] were significantly better than those in the control group[(21.81±0.25) points and (88.31±0.48) points] ( P<0.01). Conclusion:The flipped classroom model based on Simodont dental training system can effectively improve the effect of standardized training and teaching of professional skills in prosthodontics. At the same time, the students' ability of independent analysis and problem solving, cooperation and communication and expression are effectively improved.