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In this study, we composited mineralized collagen and magnesium-calcium alloy by freeze-drying, followed by dip-coating PMMA bone cement to enhance the composite of mineralized collagen and magnesium-calcium alloy. In vitro degradation test was performed to observe the pH and weight loss of the material. The contact angle test was used to detect the hydrophilicity of the material. Subsequently, MC3T3-E1 were used to assess cell biocompatibility In vitro by cell adhesion, cytotoxicity, alkaline phosphatase, alizarin red staining, and cytoskeleton. The results showed that the pH changes of the PMMA/NHAC/Mg–Ca was slower than that of the Mg–Ca , and the weight loss rate at 7 d and 14 d were lower than that of the Mg–Ca (P < 0.05) in degradation test. Wettability experiment showed that PMMA/NHAC/Mg–Ca was a hydrophilic material and Mg–Ca was a hydrophobic material (P < 0.05). In vitro cell experiments, the PMMA/NHAC/Mg–Ca had more cell adhesion than Mg–Ca and more synapses were connected to others. In the cytotoxicity experiment, the cell proliferation lever of PMMA/NHAC/Mg–Ca was higher than that of Mg–Ca at each time point (P < 0.05). In the 7 d alkaline phosphatase experiment, the PMMA/NHAC/Mg–Ca showed higher ALP activity than the Mg–Ca (P < 0.05), and in the alizarin red experiment at 14 d and 28 d, there were more obvious calcified nodules and mineralized area. After 1 day of culture in the PMMA/NHAC/Mg–Ca extract, the cells showed a clearer and more complete cytoskeletal structure and better cell morphology. In conclusion, PMMA/NHAC/Mg–Ca orthopedic implants had a better hydrophilicity, cytotoxicity and osteogenic ability, besides with a slower rate of degradation, and could be implanted in animals for further research, which were expected to be used for the repair of clinical bone defects.

To study the effect of continuous irrigation of rotating nickel-titanium instrument with several common clinical fluids on the diameter, breaking length and breaking position of nickel-titanium instrument, so as to provide some reference and theoretical basis for clinical operation and instrument improvement. A standardized curved root canal model was established, and ProTaper Universal (PTU) F1 instrument was selected for root canal preparation. The nickel-titanium F1 instrument was flushed with distilled water, 0.9% NaCl, 0.2% chlorhexidine, 1% sodium hypochlorite and 5% sodium hypochlorite, and the diameter, length and position of the instrument before and after breakage were recorded. Only 5% sodium hypochlorite influenced the diameter of 6 mm marker points under different irrigation conditions (P < .05). There was no statistical difference in the length of broken instruments among all the groups, and torsional deformation mainly occurred at the end of broken instruments. The broken positions of instruments in all the groups were located at the bending segment of the root canal. The breaking frequency of the 5% sodium hypochlorite group was the highest in the area 3–5.5 mm away from apical foramen, while the other 4 groups had the highest breaking frequency in the area 0 to 1.5 mm away from apical foramen. External irrigation with different fluids did not influence the breaking length of instruments. The closer to the apical foramen was, the higher the breaking frequency of instruments was. However, only 5% sodium hypochlorite can affect the diameter of rotary nickel-titanium instruments, and may lead to early breakage of the instrument, indicating that the use of disinfectants, except 5% sodium hypochlorite, cannot reduce breakage resistance of nickel-titanium instrument compared with distilled water flushing. Furthermore, 5% hypochlorite could not be recommended for irrigation in clinical practice.

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Effects of Gd addition on microstructure, corrosion behavior and mechanism of cast and extruded MgZn1.2GdxZr0.18 alloys are investigated through microstructure observation, weight loss and electrochemical tests. Increasing Gd from 0 to 2.0 at.%, grains are refined, MgZn2 phase, W-phase and X-phase are formed successively, and basal texture intensity is decreased. The significantly decreased grain size by extrusion and Gd addition induces formation of protective Gd2O3 and MgO layer. The extruded MgZn1.2Gd2.0Zr0.18 alloy shows decreased corrosion rate of 3.72 ± 0.36 mm/year, owing to fine and homogeneous microstructure, dual-role (micro-anode and barrier) of Xphase, compact oxidation layer and basal crystallographic texture.