Improving bioactivity and durability of yttria-stabilized zirconia

Because of its excellent mechanical properties, yttria-stabilized zirconia is currently used as an orthopedic and dental material. In this study, we have improved the bioactivity of yttria-stabilized zirconia by a combination of electrical polarization and chemical treatment. The phase transformation from tetragonal to monoclinic ZrO₂ after alkaline treatment was inhibited on positively charged yttria-stabilized zirconia surfaces compared with negatively charged and conventional surfaces. During polarization, some oxide ions move from the positively charged surface to the negatively charged surface, leading to an increase in oxygen vacancies on the positive surface and hence greater formation of Zr–OH when this surface was exposed to alkaline solution. This then reduced the water adsorption at this surface and consequently reduced the rate of cleavage of Zr–O–Zr bonds. The bioactivity was assessed by immersing the samples in simulated body fluid and evaluating the growth of apatite on the surfaces. The combination of polarization and alkaline treatment increased the bioactivity in vitro.