What are Calcium Phosphates?
Calcium phosphates comprise a family of highly biocompatible solid materials that can be used for a variety of grafting and tissue augmentation procedures. Chemically, all calcium phosphates are calcium salts of phosphoric acid. Their physical properties can range from hard and insoluble to soft, friable and soluble. Control of the properties is by a variety of factors that including setting the calcium to phosphorous ratio, the presence of traces of other biocompatible metal ions, the control of density and the inclusion of porosity.
The only calcium phosphate that is stable in contact with water is hydroxylapatite (HA), and this is the form found naturally as bone mineral. In applications where a stable, but biocompatible material is desired, HA is the material of choice. If the goal is remodeling, then more soluble forms might be of interest. Additionally, calcium phosphate dissolution can provide a local source of calcium and phosphate ions in the graft site which serve as the raw materials from which new bone can be constructed by osteoblast cells.
Regardless of the composition, all calcium phosphates are osteoconductive. This means bone bonds directly to the calcium phosphate surface without an intervening soft tissue layer. Osteoconduction helps to increase the activity of bone forming cells (osteoclasts). Benefits include the ability to bridge larger gaps, and a better chance to form bone in the presence of micromotion which is found in unstable grafting sites.
As well as the chemical composition, the physical forms of calcium phosphate materials can also be optimized for specific applications. Bone cells preferentially grow inside of porous materials. An ideal scaffold consists of interconnected pores in the size range of 50 to 400 microns. This tendency of bone to grow in pores is so strong that bone will even grow inside of materials that normally will not support bone growth at all, such as polyethylene. Porosity, especially interconnected porosity with open pores, combined with an osteoconductive calcium phosphate composition, provides a powerful bone growth scaffold.
In contrast, for applications where inertness is required such as soft tissue augmentation, dense, nonporous, nearly insoluble HA particles with a minimal surface area are ideal.
The experts at CaP Biomaterials understand calcium phosphates and can supply a wide variety of calcium phosphates with properties tailored for virtually any application. In addition, CaP can produce custom materials for specialty applications.
