Fabrication of hydroxyapatite block from gypsum block based on (NH 4)2HPO4 treatment

Yumiko Suzuki, Shigeki Matsuya, Koh Ichi Udoh, Masaharu Nakagawa, Yoshihiro Tsukiyama, Kiyoshi Koyano, Kunio Ishikawa

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


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°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.

Original languageEnglish
Pages (from-to)515-521
Number of pages7
Journaldental materials journal
Issue number4
Publication statusPublished - Dec 2005

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Dentistry(all)


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