Mechanical testing of chemically bonded bioactive ceramic materials

Most chemically bonded ceramics that are used as biomaterial are resorbable. Therefore their mechanical properties often change over time. Calcium aluminate has proven to be bioactive but non-resorbable. This opens up new application areas compared to the conventional chemically bonded ceramics, especially for load bearing applications where the long-term mechanical properties are important, e.g. in dentistry. So far no consensus has been reached upon how to test the material to obtain reliable results. This paper describes how to test hardness, expansion pressure, flexural strength and compressive strength The delicate chemistry of the material makes mechanical testing difficult. The final microstructure develops through water uptake both from the initially added water and from the storage medium. Thus some of the materials properties will be dependent on how the material has been handled, e.g. the expansion pressure. It is therefore of outermost importance to store the material in a medium that resembles the real application as close as possible. It is also important to be very careful when preparing and polishing the samples so that no flaws or defects are introduced, especially when measuring strength and hardness.