This project evaluates the feasibility of a new multiphasic, composite bone repair material composed of calcium sulfate (CS) particulate, protected from rapid degradation by an absorbable polymer either coated on, or within, a CS matrix. Repair of bone defects often requires the use of permanent or resorbable biomaterials. These materials can comprise autogenous or allogeneic bone graft, a range of alloplastic (calcium phosphate materials, bioglass, calcium sulfate materials) materials and composite combinations of these materials. Calcium sulfate (CS) is a fully degradable material for repair of bone defects. It is one of the oldest and safest biomaterials in current use. Recent research has shown that it is biocompatible, completely degradable, osteoconductive, does not cause inflammation and evokes minimal foreign body response. It can be used in combination with other bone graft materials such as autograft, calcium phosphate, bioglass and allografts. It has strong hemostatic activity and it prevents the ingrowth of soft tissue in the defect area acting as a barrier material. It stimulates the growth of micro blood vessels and hence is angiogenic. It causes precipitation of calcium phosphate deposits as it undergoes dissolution. These precipitates stimulate and direct the formation of new bone. The principal concern and complaint by practitioners using CS is that it (dissolves) too rapidly and outpaces the formation of new bone in some applications. Poly (L Lactic acid), (PLLA) is another biomaterial used in many biomedical devices with an excellent safety record. It is biocompatible and biodegradable. Our previous studies have shown that a composite of calcium sulfate and PLLA undergoes much slower dissolution in simulated body fluid than pure CS. Calcium phosphate precipitate formed as this composite degraded (which would stimulate the formation of bone in vivo). Depending upon the ratio of CS:PLLA, the degradation rate of the composite can be controlled. The product described here represents a cement that can be formulated to dissolve at controlled rates that can be matched with bone repair for a specific surgical application. This composite would overcome the disadvantage of fast dissolution of calcium sulfate, but would still retain all of its unique properties for bone grafting. There is a ready market for a new material to fill extraction sites, enhance maxilla and mandibular bone to accept dental implants, and to speed up the osseointegration of dental implants. ? ? ?
| Mamidwar, Sachin; Weiner, Michael; Alexander, Harold et al. (2008) In vivo bone response to calcium sulfate/poly L-lactic acid composite. Implant Dent 17:208-16 |
