Nilen R W N, Richter P W
Materials Science and Manufacturing Unit, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001, South Africa.
J Mater Sci Mater Med. 2008 Apr;19(4):1693-702. doi: 10.1007/s10856-007-3252-x. Epub 2007 Sep 25.
Biphasic calcium phosphate ceramics (BCP) comprising a mix of non-resorbable hydroxyapatite (HA) and resorbable beta-tricalcium phosphate (beta-TCP) are particularly suitable materials for synthetic bone substitute applications. In this study, HA synthesised by solid state reaction was mechanically mixed with beta-TCP, then sintered to form a suite of BCP materials with a wide range of HA/beta-TCP phase content ratios. The influence of sintering temperature and composition on the HA thermal stability was quantified by X-ray diffraction (XRD). The pre-sinter beta-TCP content was found to strongly affect the post-sinter HA/beta-TCP ratio by promoting the thermal decomposition of HA to beta-TCP, even at sintering temperatures as low as 850 degrees C. For BCP material with pre-sinter HA/beta-TCP = 40/60 wt%, approximately 80% of the HA decomposed to beta-TCP during sintering at 1000 degrees C. Furthermore, the HA content appeared to influence the reverse transformation of alpha-TCP to beta-TCP expected upon gradual cooling from sintering temperatures greater than 1125 degrees C. Because the HA/beta-TCP ratio dominantly determines the rate and extent of BCP resorption in vivo, the possible thermal decomposition of HA during BCP synthesis must be considered, particularly if high temperature treatments are involved.
由不可吸收的羟基磷灰石（HA）和可吸收的β-磷酸三钙（β-TCP）混合而成的双相磷酸钙陶瓷（BCP）是用于合成骨替代应用的特别合适的材料。在本研究中，通过固态反应合成的HA与β-TCP进行机械混合，然后烧结以形成一系列具有广泛HA/β-TCP相含量比的BCP材料。通过X射线衍射（XRD）定量烧结温度和组成对HA热稳定性的影响。发现预烧结β-TCP含量通过促进HA热分解为β-TCP而强烈影响烧结后HA/β-TCP比，即使在低至850℃的烧结温度下也是如此。对于预烧结HA/β-TCP = 40/60 wt%的BCP材料，在1000℃烧结期间约80%的HA分解为β-TCP。此外，HA含量似乎影响从高于1125℃的烧结温度逐渐冷却时预期的α-TCP向β-TCP的逆转变。由于HA/β-TCP比主要决定了BCP在体内的吸收速率和程度，因此在BCP合成过程中必须考虑HA可能的热分解，特别是如果涉及高温处理。
