Summary Pseudowollastonite ceramic (psW) composed of CaO·SiO2 was found to be bioactive in a simulated body fluid environment. The chemical reaction initiated at the material surface resulted in hydroxyapatite (HA)formation. These bone‐bonding properties are essential for securing the necessary physico‐chemical integration of the material with living bone. Materials behaving in this way can be considered for potential biomedical application as bone tissue substitute for a natural bone repair or replacement as implant. A mechanism of hydroxyapatite formation on pseudowollastonite ceramics surface was investigated during exposure to a simulated body fluid (SBF) for a period of 3 weeks. Morphology and structure of the surface product and its original substrate was examined by thin‐film X‐ray diffraction, scanning electron microscopy and high‐resolution transmission electron microscopy. HA crystals were found to form on an amorphous silica intermediate layer. (100) lattice planes of HA were resolved and identified. Concentration of ions in the SBF and pH of the SBF were monitored throughout the exposure. Additional pH measurements were made at the interface of psW with SBF. The HA formation occurred when there was a sudden increase of pH from 7·25 to 10·5 at the interface of psW with SBF as a result of ionic exchange between 2H+ and Ca2+ within the psW network. This ionic exchange transformed the psW crystals into an amorphous silica phase. The appropriate pH and the ion concentrations were essential for partial dissolution of the amorphous silica phase and subsequent precipitation of a Ca‐P rich phase which then transformed to HA.

No abstract

The synthesis of a number of halogenated aromatic methacrylate monomers was achieved by (1) the esterification of hydroxyl‐containing methacrylate esters with 2,3,5‐tri‐iodobenzoic acid and (2) by the nucleophilic addition of 2,3,5‐tri‐iodobenzoic acid, or polyhalogenated phenols, to 2,3‐epoxypropyl methacrylate, yielding white crystalline products which were fully characterized. These monomers could be homopolymerized in the melt to produce clear, intensely X‐ray opaque glasses possessing high refractive indices. The monomers themselves were soluble in a variety of methacrylate monomers with which they could be copolymerized to produce clear radiopaque materials. The stability of the homopolymers in an aqueous environment was excellent as was thermal stability, exhibiting little decomposition below 300°C. © 1997 SCI.