title: Fabrication of hydroxyapatite block from gypsum block based on (NH4)2HPO4 treatment.
abstract: The aim of this study was to evaluate the feasibility of fabricating low-crystalline, porous apatite block using set gypsum as a precursor based on the fact that apatite is thermodynamically more stable than gypsum. When the set gypsum was immersed in 1 mol/L diammonium hydrogen phosphate aqueous solution at 100 degrees C, it transformed to low-crystalline porous apatite retaining its original shape. The transformation reaction caused a release of sulfate ions due to an ion exchange with phosphate ions, thus leading to a decrease in the pH of the solution. Then, due to decreased pH, dicalcium phosphate anhydrous--which has similar thermodynamic stability at lower pH--was also produced as a by-product. Apatite formed in the present method was low-crystalline, porous B-type carbonate apatite that contained approximately 0.5 wt% CO3, even though no carbonate sources--except carbon dioxide from air--were added to the reaction system. We concluded therefore that this is a useful bone filler fabrication method since B-type carbonate apatite is the biological apatite contained in bone.
authors.affiliation: Department of Biomaterials, Faculty of Dental Science, Kyushu University, Higashi-ku, Fukuoka, Japan. yumi-szk@dent.kyushu-u.ac.jp
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shigeki
authors.initials: S
authors.lastname: Matsuya
authors.forename: Koh-ichi
authors.initials: K
authors.lastname: Udoh
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nakagawa
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Tsukiyama
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Koyano
authors.forename: Kunio
authors.initials: K
authors.lastname: Ishikawa
mesh_terms: D018786:Bone Substitutes / Q000138:chemical synthesis*; D002133:Calcium Sulfate / Q000737:chemistry; D017886:Durapatite / Q000138:chemical synthesis*; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D018786:Bone Substitutes; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; C024788:ammonium phosphate; D017886:Durapatite; D002133:Calcium Sulfate