July 25, 2007
Just over a decade ago, the Food and Drug Administration approved the first calcium phosphate cement to repair craniofacial wounds and/or birth defects. The paste was self setting in the cavity, promoted new bone growth, and gave way to new bone as it formed. However, calcium phosphate cement arrived on the market with a major limitation. The material is of such low strength and high susceptibility to severe fracture that doctors can use it only to reconstruct non-stress bearing bone, raising the need for a tougher new generation of calcium phosphate cement. As reported online last May in the journal Biomaterials, scientists partially supported by NIDCR have taken an important step in that direction. According to the authors, they devised a unique two-step approach that starts with filling the bone cavity with a calcium phosphate cement paste that is macroporous, or contains needed pores to allow the ingrowth of new bone. Thereafter, they introduce a stronger, fiber-reinforced layer that provides the needed early structural support. Simultaneous with new bone filling in and around the macropores to provide natural strength, the reinforcing fibers of the second layer begin to dissolve and produce additional macropores. In a series of laboratory experiments, the authors found the layered structure greatly improved the mechanical strength of the calcium phosphate cement implant. They also determined the relationships between flexural strength, stiffness, and the optimum implant layer thickness ratios.