Demineralization characteristics of cortical bone under voltage application in phosphate-buffered saline

抄録

Bone tissue is a composite material consisting of hydroxyapatite and collagen. It is known that bone tissue becomes brittle with age not only because of decreased bone density but also because of excessive apatite deposition in the tissue. Demineralization provides a means for changing the mechanical properties of bone. Although demineralization decreases the elastic modulus of bone tissue, it also increases the flexible deformation compliance of the tissue. Previous studies have shown that localized demineralization around the areas of stress concentration in cortical bone specimens can improve impact fracture toughness despite reducing the stiffness. Demineralization is usually performed via chemical reactions in solution. This method is not suitable for limited demineralization at specific areas because of the infiltration and outflow of the solution. In this study, we focus on reactions induced by electric stimulation and investigate the possibility of demineralization by applying voltage. X-ray diffraction was used to verify the demineralization progression. The absence of apatite peaks in the X-ray diffraction pattern of the bone specimen after voltage application shows that demineralization has occurred after this treatment. To investigate the relationship between the electrode shape and the demineralized area, the hardness distribution on the surface of specimen was measured via multiple-point micro-indentation tests. The impact fracture characteristics in the limited areas demineralized by voltage application were measured through Charpy loading tests. As a result, it was found that the demineralization was accelerated at the contact area of the electrode to specimen surface during the voltage application. And it was suggested that the limited demineralization may improve the fracture strength of the bone tissue.