Calcium phosphate bioceramics research in Latvia

Calcium phosphate bioceramics including glass-ceramics and hydroxyapatite have been manufactured and investigated for implantation purposes. Three glass systems were selected based on CaO and P2O5 and an inert metal oxide (either Ta2O5, TiO2 or Nb2O5). Different compositions were found giving crystal phases in a glassy matrix. These glass-ceramics were tested for strength with 4-point bending, and the biocompatibility ascertained using in vitro and in vivo tests. The Nb2O5 containing glass-ceramic showed bone apposition and was found to be a suitable material for implantation. Hydroxyapatite was produced using the wet method and it was found that the pH during the reaction and the dispersivity of the Ca(OH)(2) influence the purity of the powder. The pH was controlled by addition of ammonium hydroxide to the precipitate. Hydroxyapatite sprayed onto grit blasted titanium showed low strengths of 20-30 MPa with adhesive failure but was increased to 60-70 MPa with an intermediate glass layer. Composites of glass-ceramic with hydroxyapatite exhibited a higher strength than hydroxyapatite with a value of 100-120 MPa. (C) 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved.