Phase composition and in vitro bioactivity of porous implants made of bioactive glass S53P4

This work studied the influence of sintering temp. on the phase compn., compression strength and in vitro properties of implants made of bioactive glass S53P4.  The implants were sintered within the temp. range 600-​1000 °C.  Over the whole temp. range studied, consolidation took place mainly via viscous flow sintering, even though there was partial surface crystn.  The mech. strength of the implants was low but increased with the sintering temp., from 0.7 MPa at 635 °C to 10 MPa at 1000 °C.  Changes in the compn. of simulated body fluid (SBF)​, the immersion soln., were evaluated by pH measurements and ion anal. using inductively coupled plasma optical emission spectrometry.  The development of a calcium phosphate layer on the implant surfaces was verified using SEM-​electron-​dispersive X-​ray anal.  When immersed in SBF, a calcium phosphate layer formed on all the samples, but the structure of this layer was affected by the surface cryst. phases.  Hydroxyapatite formed more readily on amorphous and partially cryst. implants contg. both primary Na₂O·CaO·2SiO₂ and secondary Na₂Ca₄(PO₄)​₂SiO₄ crystals than on implants contg. only primary crystals.