[Pseudo allergic reaction to metal implant]

Zirconia Based Dental Biomaterials: Structure, Mechanical Properties, Biocompatibility, Surface Modification, and Applications as Implant

Zirconia, with its excellent mechanical properties, chemical stability, biocompatibility, and negligible thermal conductivity, is ideal for dental and orthopedic applications. In addition, the biocompatibility of zirconia has been studied in vivo, and no adverse reactions were observed when zirconia samples were inserted into bone. However, their use is controversial among dentists and researchers, especially when compared with mature implants made of titanium alloy. The advantages and limitations of zirconia as biomaterials, such as implant materials, need to be carefully studied, and the design, manufacture, and clinical operation guidelines are urgently required. In this review, the special components, microstructure, mechanical strength, biocompatibility, and the application of zirconia ceramics in biomaterials are detailly introduced. The review highlights discussions on how to implement innovative strategies to design the physical and chemical properties of zirconia so that the treated zirconia can provide better osteointegration after implantation.

In vitro and in vivo evaluations of nano-hydroxyapatite/polyamide 66/yttria-stabilized zirconia as a novel bioactive material for bone screws: Biocompatibility and bioactivity

Zirconia and its derivatives have been receiving increased levels of attention with regard to their potential application in bone tissue engineering. These materials are of particular interest because of their excellent characteristics, such as superior biological and mechanical properties. In this study, yttria-stabilized tetragonal zirconia (YTZ)-reinforced nanohydroxyapatite/polyamide 66 (nHA/PA66) bone screws were prepared. The biocompatibility and bioactivity of nHA/PA66/YTZ were evaluated in vitro using MC3T3-E1 cells. Biocompatibility and bioactivity experiments (cell counting kit-8 tests, cell immunofluorescence analysis, and polymerase chain reaction) showed that nHA/PA66/YTZ could facilitate the biological functions of MC3T3-E1 cells. The attachment, proliferation, spreading, and expression of genes associated with osteogenesis (collagen 1, osteopontin, and osteocalcin) in cells cultured with the nHA/PA66/YTZ composite were all superior compared with the control groups (P < 0.05). In addition, nHA/PA66/YTZ bone screws were implanted into the femoral condyles of rabbits, and titanium screws were employed as a control group; postoperative histology and blood analysis revealed no obvious damage to the liver, kidneys, or any other major organs in either of the experimental groups. Moreover, nHA/PA66/YTZ screws resulted in significantly better bone-implant contact interfaces and enhanced formation of trabecular bone (P < 0.05); these characteristics were markedly better than those in the group that received titanium screws. These observations indicate that YTZ-reinforced nHA/PA66 composites have significant potential for applications in bone tissue engineering.