Local surface damage and material dissolution in 45S5 bioactive glass: Effect of the contact deformation

Bioactive glasses react with the human physiological solution in control of their biofunctionality. The stress state in bioactive glasses determines the chemomechanical reaction and their biofunctionality. Using the microindentation technique, the effect of the indentation deformation on the surface damage and material dissolution of 45S5 bioglass was investigated. The indentation-induced local surface damage, including ring cracks and radial cracks, was revealed before and after the immersion tests in phosphate buffer solution (PBS). There existed a critical load for the formation of the radial cracks, which emanated from the periphery of the outmost ring crack. The growth of the radial cracks in the PBS solution displayed the stress-corrosion behavior with the crack-growth speed being a linear function of the indentation load. Fast dissolution occurred at the edges of the surface-damaged zone due to stress-assisted dissolution under the action of local tensile stress, which was different from the dissolution behavior of stress-free 45S5 bioglass.