Zirconia is a promising material for dental implant with its excellent biocompatibility, good mechanical properties, and esthetic effect similar to natural teeth. To improve the bioactivity and osteogenic properties of zirconia, pre-sintered zirconia discs were divided into C, T 3 , T 5 , and T 7 group. Group C was as control. T 3 , T 5 , and T 7 groups were soaked in hydrofluoric acid (HF) for 30, 50, and 70 s, respectively. Then, they were placed into CaCl 2 solution and heated in NaOH solution. After sintering, the samples were characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction, which confirmed the ZrO 2 polycrystalline particulates in situ synthesized on the treated sample discs. The surface roughness of the treated samples was increased with the prolonged of acid treatment time (p < .05), while the three-point bending strength did not decrease significantly (p > .05). MC3T3-E1 cells were cultured on zirconia discs to evaluate the bioactivity and osteogenic effect of modified zirconia. The living&dead fluorescence staining and CCK-8 assay showed that the specimens were non-toxic and significantly promoted cell proliferation. In addition, the cell proliferation was enhanced with the increase of zirconia surface roughness. Polycrystalline particles modified zirconia were beneficial to cell spreading. After osteogenic induction, MC3T3-E1 cells inoculated on modified zirconia exhibited higher alkaline phosphatase activity, mineralization activity and upregulated osteogenesis-related gene expression. Above all, in situ synthesized polycrystalline particulates significantly improve the biological activity of zirconia, which will promote the widespread application of zirconia implants.bioactivity, in situ synthesized, osteogenesis, polycrystalline particulates, zirconia
| INTRODUCTIONWith the development of dental materials and the increasing awareness of dental health, implantation has become the main choice for patients subjected to dentition defects and dentition loss. [1][2][3][4] Although titanium and titanium alloy have long been the dominant implant materials, they still have a series of problems, such as the gray color reducing esthetic outcomes, 5 hypersensitivity caused by Ti ion precipitation 6 and the corrosion occurring in saliva. 7 Zirconia with its excellent biocompatibility, desirable esthetics characteristic, and durable corrosion resistance is the most promising alternative material for titanium and titanium alloy implants. 8-11 However, zirconia is considered to be an inert biomaterial and its osteogenic effect needs to be improved to promote its wide application in the field of dentistry. 12,13 For successful long-term treatment of zirconia implants, modifications have been proposed to alter the surface chemistry, morphology, and bioactivity, as is widely used in Ti implants. [14][15][16][17] Many studies have focused on zirconia surface modifications to improve its