Objective To investigate the inhibitory effects of silencing expression ofEZH2 gene on the cell proliferation of human QBC939 cells and its mechanisms. Methods The targeting siRNA was designed and trans-fected into QBC939cells. The expressions of EZH2 mRNA and protein were detected by real-time qPCR and west-ern blotting,respectively. The ability of cellproliferationwas analyzed by MTT assay and plate clone formation assay. Cell apoptosis and cycle percentage weremeasured by flow cytometry. Cell senescence was assessed byβ-galactosi-dase dyeing.The expressions of H3K27me3,P14ARF,P16INK4a,P53,P21 and E2F1 proteinwere determined by West-ern blotting.Results Compared with the control group ,the expressions of mRNAand protein were significantly elevat-ed in experimental group. The ability of cellproliferation in the experiment group was significantly down regulated , which could also cause a rise of G1/S phase ,but not a marked variation of apoptosis rate. Silencing EZH2 would induce a obvious senescence phenotype in QBC939 cells. EZH2-siRNA transferredcould also down-regulate the expressions of H3K27me3 and E2F1 protein,while up-regulating the expressions of P14ARF,P16INK4a,P53 and P21 protein in QBC939 cells.Conclusions Silencing EZH2 could induce a significant inhibition on cell proliferation of QBC939 cells,the mechanism of which may be associated with the senescence pathway regulation.

Objective: To investigate the effect of frequently used Duraphaton preventing dental demineralization of patients with fixed orthodontic appliances. Methods: A total of 50 orthodontic patients wearing fixed appliances at Department of orthodontics, Affiliated Stomatological Hospital, Nanjing Medical University from June to December 2021 were selected as study subjects by convenient sampling method. They were then randomly divided into experimental group and control group according to random numbers. The experimental group received high-frequency fluoride treatment for unilateral maxillary lateral incisors and no treatment on the contralateral side. Meanwhile, the control group received placebo treatment for unilateral maxillary lateral incisors and no treatment on the contralateral side. Each patient was followed up for 6 months. The initial and final photographs of patients' maxillary lateral incisors were observed and scored to determine the mean demineralization progression index for each group. Results: The difference in mean demineralization progression index was statistically significant when comparing different groups(P<0.05), and the lowest incidence of demineralization was reported in the Duraphattreated group (0.960±0.465), followed respectively by the fluoride-free control group (1.213±0.713), the placebo control group (1.267±0.720) and the placebo treatment group (1.307±0.713). Conclusion High frequency use of Duraphatis is effective in reducing the incidence of demineralization in patients with fixed orthodontic appliances.