Bone Substitutes
Analysis of Medical Ceramics
In bone surgery and implantology, hydroxylapatite and β-tricalcium phosphate are used as synthetic bone substitute materials. It is slowly resorbed and replaced by autologous bone. Additionally, it is also used as a bioactive coating for titanium implants to improve bone integration. Hydroxylapatite is also contained as an additive in special toothpastes, known as sensitive toothpastes.
Particle Size and Shape
The processing properties of ceramics and their resorption in the body are critically dependent on particle size. The smaller the particles, the larger the surface area, and the faster they can be metabolized by the body.
The measurement is carried out in our laboratory using laser diffraction as part of routine raw material control.
Using scanning electron microscopy (SEM), the particle shape can also be examined. This is particularly true when the material is composed of nanocrystals and agglomerates into larger particles.
Phase Purity
There are various ceramics based on the elements Ca, P, and O, which differ in their crystal structure. The different phases can be distinguished from each other by X-ray diffraction (XRD) and a comparison with a crystal structure database. Additionally, crystalline foreign phases can be identified in this way.
Subsequently, the most important phases are quantified regarding their proportion according to ISO 13779-3. Based on the reflection widths, the crystallite size can be determined. Through supplementary measurements after heat treatment (calcination), the Ca/P ratio of the sample, as well as the crystallinity content of hydroxylapatite, can also be determined.
Phase purity can also be verified for other materials used in the medical field, such as zirconium dioxide, which is employed as an X-ray contrast agent or in dental and orthopedic implants and coatings. Resorbable calcium sulfate, frequently used in bone substitute composites, is another example.
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