Hard Tissue Testing

The Challenge

Bone, dentin, and dental enamel are all considered to be hard tissues. Specimens of this type are most commonly tested in compression and flexural. The most common results obtained from a compression or flexural test on hard tissues is modulus and force at fracture. Typically, these specimens come from mice, rats, or other mammals and are small in size. Despite being small in size, hard tissues have high stiffness. A typical challenge with measuring modulus is accurate measurement of displacement. For a given force, a hard tissue such as bone will exhibit small displacement. In addition to compression testing, 3-point and 4-point bend tests are common to quantify force at fracture on bone sections. Often, this testing must be conducted at physiologically relevant test conditions, such as in a hydrated bath and at body temperature.

When conducting compression testing on hard tissues, it is critical that users choose appropriately sized compression platens to closely match specimen size, ensure the compression platens are spherically seated or self-aligning to apply even pressure on the specimen, and use an accurate source to measure system displacement. For example, an accurate measurement source of displacement could be via compliance correction in the software, or by using a strain measuring device, such as a linear variable deflection transducer (LVDT) or a video extensometer. When testing flexural specimens, it is critical that the anvils on the flexural fixture are appropriately sized to the specimen and that the flexural fixture properties, such as span length, are easily entered into the software.