Cytocompatibility And Bonding Property Of Bioinspired Nacre-like Zirconia-resin Composites

Objective: By imitating the microstructure of natural seashells,our team previously developed the bioinspired zirconia-polymethyl methacrylate(PMMA)dental restorative composites with suitable mechanical properties for human teeth,excellent fracture toughness and machinability.Its hardness and elastic modulus are suitable for dentin and enamel respectively,which are applicable to the field of oral repair.Good bonding performance and non-cytotoxicity are the two most important properties in clinical application of the novel biomimetic dental prosthesis material.Therefore,based on the previous study,the first part of this paper focuses on the cytocompatibility of the biomimetic composite material.On the basis of confirming the cellular safety of the material,the second part studies the basic bonding properties of the biomimetic composite material.Through the study of the above two parts,the potential of the bioinspired zirconia-polymethyl methacrylate composite in oral clinical application is explored.Methods: Two kinds of biomimetic zirconia-resin composites were used for this study.Their hardness and elastic modulus were respectively compatible with human dentin and enamel,which were lamellar structure(about 77% resin)and brick-and-mortar structure(about 20% resin).In the first part of this paper,CCK-8 assay was used to detect the cytotoxicity of lamellar and brick-and-mortar composite materials on human periodontal ligament fibroblasts(HPDLF)in vitro,and the morphological changes of HPDLF cells at different time points were observed.In the second part,the clinical zirconia material(Vita In-Ceram YZ)was used as the control group,and the shear test was selected to test the bonding strength of the two composite materials.At the same time,the influence of sandblasting surface treatment and different shear directions on bonding strength were studied.SPSS 22.0 software was used for one-way ANOVA of all data,P < 0.05 was statistically significant.Results: The results of CCK-8 experiment in the first part showed that the cytotoxicity levels of the two composites were rated as grade 0 or 1 at 1,2,3,and 5 days.Both the lamellar and the brick-and-mortar composite materials had no negative effect on cell proliferation during the experimental period.In the second part of this paper,the shear test results showed that the bonding strength of the two composites is improved compared with the control group(Vita in-Ceram YZ).After sandblasting,the vertical and horizontal bond strengths of the lamellar structure group were 17.56±1.56 MPa and18.67±1.92 MPa,and those of the brick-and-mortar structure group were 16.36±1.30 MPa and 16.99±1.67 MPa,respectively.The lamellar structure had higher bonding strength than the brick-and-mortar(P < 0.05),while the shear direction had no statistically significant effect on the bonding strength of the two composites(P > 0.05).Conclusion: 1.Two kinds of the novel bioinspired zirconia-resin composites suitable for human teeth were non-cytotoxicity to HPDLF cells cultured in vitro.2.The bonding strength of the two composites was higher than that of zirconia material(Vita In-Ceram YZ),and the lamellar composite was higher than that of the brick-and-mortar composite.The shear direction has little effect on the bonding strength of the composites,and the sandblasting surface treatment method can improve the bonding strength of the composites.