Background: Mesoporous calcium-silicate nanoparticles (MCSNs) have good prospects in the medical field due to their great physicochemical characteristics, antibacterial activity and drug delivery capacity. This study was to analyze the antibiofilm activity and mechanisms of silver (Ag) and zinc (Zn) incorporated MCSNs (Ag/Zn-MCSNs) with different percentages of Ag and Zn. Methods: Ag/Zn(1:9, molar ratio)-MCSNs and Ag/Zn(9:1, molar ratio)-MCSNs were prepared and characterized. Endocytosis of nanoparticles by Enterococcus faecalis (E. faecalis) treated with Ag/Zn-MCSNs was observed using TEM to explore the antibacterial mechanisms. The antibiofilm activity of Ag/Zn-MCSNs with different ratios of Ag and Zn was tested by E. faecalis biofilm model in human roots. The human roots pretreated by different Ag/Zn-MCSNs were cultured with E. faecalis. Then, SEM and CLSM were used to observe the survival of E. faecalis on the root canal wall. Cytotoxicity of the nanoparticles was tested by CCK8 kits. Results: The Ag/Zn-MCSNs release Ag + and destroy the cell membranes to kill bacteria. The MCSNs containing Ag showed antibacterial activity against E. faecalis biofilms in different degrees, and they can adhere to dentin surfaces to get a continuous antibacterial effect. However, MTA, MCSNs and Zn-MCSNs could not disrupt the bacterial biofilms obviously. MCSNs, Ag/Zn(1:1, molar ratio)-MCSNs and Ag/Zn(1:9)-MCSNs showed no obvious cytotoxicity, while Ag-MCSNs and Ag/Zn(9:1)-MCSNs showed cytotoxicity. Zn-MCSNs can slightly promote cell proliferation. Conclusion: Ag/Zn-MCSNs have good antibiofilm activity. They might achieve an appropriate balance between the antibacterial activity and cytotoxicity by adjusting the ratio of Ag and Zn. Ag/Zn-MCSNs are expected to be a new type of root canal disinfectant or sealer for root canal treatment.

Background: Better understanding of the danger zone anatomy in mesial roots (MRs) of mandibular first molars (MFMs) may serve to decrease the risk of mishaps. This study aimed to measure the minimal distal dentine thicknesses of danger zone in MRs of MFMs in a native Chinese population using cone-beam computed tomography (CBCT). Methods: CBCT images of 1792 MFMs from 898 Chinese patients were analyzed. The minimal distal dentine thicknesses of the mesiobuccal (MB) and mesiolingual (ML) canals below the furcation 1, 2, 3, 4, 5 mm were measured. The association between the minimal distal dentine thicknesses and the root lengths, patient's age and gender, side were assessed. Results: The minimal distal dentine thicknesses of MB and ML canals are located 3 ∼ 4 mm below the furcation for both men and women. There are no differences between MB and ML canals, while the minimal distal dentine thicknesses of MB and ML canals were higher in men than women (P < 0.05), except at 1 and 3 mm of ML canals (P > 0.05). The minimal distal dentine thicknesses of MB and ML canals increased with age in both men and women at each location (P < 0.05). The minimum distal dentine thickness at every location were significantly different between long teeth and short teeth both in men and women (P < 0.05), with short teeth having the smallest mean values. There are no significant differences between two sides (P > 0.05). Conclusions: The minimal distal dentine thicknesses of MRs in MSMs have close correlation with root length, patient's age and gender.

Background: Better understanding of the danger zone anatomy in mesial roots (MRs) of mandibular first molars (MFMs) may serve to decrease the risk of mishaps. This study aimed to measure the minimal distal dentine thicknesses of danger zone in MRs of MFMs in a native Chinese population using cone-beam computed tomography (CBCT). Methods: CBCT images of 1792 MFMs from 898 Chinese patients were analyzed. The minimal distal dentine thicknesses of the mesiobuccal (MB) and mesiolingual (ML) canals below the furcation 1, 2, 3, 4, 5 mm were measured. The association between the minimal distal dentine thicknesses and the root lengths, patient’s age and gender, side were assessed. Results: The minimal distal dentine thicknesses of MB and ML canals are located 3∼4 mm below the furcation for both men and women. There are no differences between MB and ML canals, while the minimal distal dentine thicknesses of MB and ML canals were higher in men than women ( P <0.05), except at 1 and 3 mm of ML canals ( P >0.05). The minimal distal dentine thicknesses of MB and ML canals increased with age in both men and women at each location ( P <0.05). The minimum distal dentine thickness at every location were significantly different between long teeth and short teeth both in men and women ( P < 0.05), with short teeth having the smallest mean values. There are no significant differences between two sides ( P >0.05). Conclusions: The minimal distal dentine thicknesses of MRs in MSMs have close correlation with root length, patient’s age and gender.

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The fluorinated polyacrylate latex were successfully prepared with semi- continuous seeded emulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA) and hexafluorobutyl methacrylate (HFMA) which was initiated with potassium persulfate (KPS) initiator and emulsified with the novel mixed surfactants of sodium lauryl glutamate (SLG) and alkylphenol ethoxylates (OP-10). The structure of the resultant latex was confirmed by Fourier transform infrared spectroscopy (FTIR). The particle size of the latex was measured by Zetatrac dynamic light scattering detector. The film of latex was tested by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and contact angle (CA). The optimum conditions of preparing the novel fluorinated polyacrylate latex are optimized and the results are as follows: the amount of emulsifiers is 4.0%; mass ratio of SLG to OP-10 is 1:1, the amount of the initiator is 0.6%. The mass ratio of MMA to BA is 1:1 and the amount of HFMA is 7.0%. In this case, the conversion is high and the polymerization stability is good. In addition, the water resistance and thermal properties of the latex films were improved significantly in comparison with the film of the latex prepared without the fluorinated monomer.