Implant material bone grafting

Another important trend in the future will be the improvement in the biological properties of bone substitutes, the aim being to transform a bone defect into new mature bone as fast as possible. This implies that the focus will be set on resorbable materials that possess an open-porous structure allowing cells to invade the structure. Another potential focus could be set on osteoinductive ceramics. A number of authors have indeed observed that ceramic bone graft substitutes implanted under the skin or in muscles are filled or coated with bone over time. However, despite very intensive research, there is only a poor understanding of the mechanisms leading to osteoinduction, and as a result, it is not possible at the moment to design an osteoinductive ceramic. 

Allograft bone has been very extensively investigated as a commercial bone graft material. One of the first studies on the development of an injectable lysine-derived polyurethane bone graft investigated an LDI-based carrier for demineralized bone matrix [18]. An LDI-poly(p-dioxanone-co-glycolate) prepolymer was mixed with demineralized bone matrix to form a reactive putty. Implantation of the putty in an intramuscular site did not elicit an adverse inflammatory response. Several more recent studies have... 

Based on observed tissue response, synthetic bone-graft substitutes can be classified into inert (e.g., alumina, zirconia), bioactive (e.g., hydroxyapatite, bioactive glass), and resorbable substitutes (e.g., tricalcium phosphate, calcium sulfate). Of these, resorbable bone-graft substitutes are preferred for bone defect filling because they can be replaced by new natural bone after implantation, p-tricalcium phosphate (Ca3(PO )2, p-TCP) is one of the most widely used bone substitute material, due to its faster dissolution characteristics. Preparation of magnesium-substituted tricalcium phosphate ((Ca, Mg)3(PO )2, p-TCMP) has been reported by precipitation or hydrolysis method in solution. These results indicate that the presence of Mg stabilizes the p-TCP structure (LeGeros et al., 2004). The incorporation of Mg also increases the transition temperature from p-TCP to a-TCP and decreases the solubility of p-TCP (Elliott, 1994 Ando, 1958). 

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