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Abstract
Heat treatment of an MgO-CaO-SiO2-P2O5 glass gave a glass ceramic containing crystalline
apatite (Ca10(PO4)6O,F2] and beta-wollastonite (CaO,SiO2) in an MgO-CaO-SiO2 glassy
matrix. It showed bioactivity and a fairly high mechanical strength which decreased
only slowly, even under load-bearing conditions in the body. It is used clinically
as artificial vertebrae, iliac bones, etc. The bioactivity of this glass ceramic was
attributed to apatite formation on its surface in the body. Dissolution of calcium
and silicate ions from the glass ceramic was considered to play an important role
in forming the surface apatite layer. It was shown that some new kinds of bioactive
materials can be developed from CaO,SiO2-based glasses. Ceramics, metals and organic
polymers coated with bone-like apatite were obtained when such materials were placed
in the vicinity of a CaO,SiO2-based glass in a simulated body fluid. A bioactive bone
cement which was hardened within 4 min and bonded to living bone, forming an apatite,
was obtained by mixing a CaO,SiO2-based glass powder with a neutral ammonium phosphate
solution. Its compressive strength reached 80 MPa comparable to that of poly(methyl
methacrylate) within 3 d. A bioactive and ferromagnetic glass ceramic containing crystalline
magnetite (Fe3O4) in a matrix of CaO,SiO2-based glassy and crystalline phases was
obtained by a heat treatment of a Fe2O3-CaO.SiO2-B2O3-P2O5 glass. This glass ceramic
was shown to be useful as thermoseeds for hyperthermia treatment of cancer.