Glass-reinforced hydroxyapatite: a comprehensive study of the effect of glass composition on the crystallography of the composite.

Glass-reinforced HA composites were produced using phosphate-based glasses, and a structure refinement was carried out to determine the effect of the glass on the structure of the residual HA. Quantitative phase analysis showed that the glass causes some of the HA to decompose to beta-TCP and, at higher temperatures, to alpha-TCP. It also was indicated that when three phases were present, the formation of the alpha-TCP arose from decomposition of the beta-TCP and not from further decomposition of HA to alpha-TCP. The unit cell dimensions showed a decrease in the a axis and an increase in the c axis, giving an overall unit cell decrease in volume. There also was a significant effect based on the amount of glass added. The changes found in the composite containing the 4 wt% glass were attributed to the loss of carbonate and loss of hydroxyl. This was expected to cause shrinkage in the unit cell; however this was not seen, and therefore the major changes in the unit cell were attributed to the ions from the glass taking an interstitial role in the HA structure, thus not allowing the unit cell to shrink as much as expected.