Preparation of dense hydroxylapatite or rhenanite containing bioactive glass composites

The effect of time at 600 degrees C and of small additions of Al2O3 and B2O3 on the sintering of two composite materials of (1) hydroxylapatite (Ca10(PO4)6(OH)2) and bioactive glass (SiO2-CaO-P2O5-Na2O) or (2) rhenanite (CaNaPO4) and bioactive glass were studied. Scanning microscopy, quantitative EDX, x-ray diffraction, helium gas density measurements, and diametral measurements were performed on the resulting composites. No reactions were observed with the SEM or XRD between the hydroxylapatite particles and the glass matrix within sufficient sintering times to achieve maximum density. The rheunanite-containing composites were observed to form Na2O2CaO3SiO2 crystals by x-ray diffraction, probably as a result of dissolution of the rhenanite particle surfaces into the glass phase, the crystals formed in the glass or at the interface of the glass, and the ceramic particles. However, within the short sintering times needed to achieve maximum density the rhenanite particles remained mostly intact. The rhenanite-containing materials gave better results than the hydroxylapatite-containing materials. The glass composition had a great effect on the densification process.