Resorbable materials

Figure 7. Proposed metabolic pathway of diflubenzuron in rats (percentages of resorbed material)...

Campoccia D, et al. (1998). Semisynthetic resorbable materials from hyaluronan esterification. Biomat. 19 2101-2127. 

Campoccia, D., Doherty, E, Radice, M., Brun, E, Abatangelo, G. and Williams, D.E, Semisynthetic resorbable materials from hyaluronan esterification. Biomaterials, 19, 2101, 1998. 

Although Plaster of Paris was used inl892asabone substitute [Peltier, 1961], the concept of using synthetic resorbable ceramics as bone substitutes was introduced in 1969 [Hentrich et al., 1969 Graves et al., 1972]. Resorbable ceramics, as the name implies, degrade upon implantation in the host. The resorbed material is replaced by endogenous tissues. The rate of degradation varies from material to material. Almost all bioresorbable ceramics except Biocoral and Plaster of Paris (calcium sulfate dihydrate) are variations of calcium phosphate (Table 39.8). Examples of resorbable ceramics are aluminum calcium phosphate, coralline. Plaster of Paris, hydroxyapatite, and tricalcium phosphate (Table 39.8). 

Gogolewski, S. and Pennings, A.J., 1983. Resorbable materials of poly(iJactide). II. Fibres spun from solutions of poly(Llactide) in good solvents. /. Appl. Polym. Sci., 28 1045-1061. 

N. Tiberiu, Concepts in biological analysis of resorbable materials in oro-maxiUofacial surgery. Rev. Chir. Oro-maxilo-fac. Implantol. 2 (2011) 33-38. 

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. 

The CBBCs can be divided into two main groups resoibable and stable biomaterials. Ca-aluminate based biomaterials and to some extent Ca-sihcates are stable materials after hydration, and can favorably be used for load-bearing applications. The Ca-phosphates, Ca-sulphates and Ca-carbonates are known to be resorbable or slowly resorbable when inserted in the body, and their main applications are within bone void filUng with low mechanical stress upon the biomaterial. The resorbable materials are after various time depending on the specific chemical composition replaced by new bone tissue. This can start immediately after injection and the material can be completely dissolved after months and in some cases after a few years. 

Significant eftort is now focusing on tissue-engineered vessels and heart valves. The history of this effort is found in the seeding or culturing of endothelium on synthetic vascular prostheses. The clinical outcomes did not justify continued development. However, rrew technology allows vascular tissue to be formed on scaffolds of either synthetic or resorbable materials. The awareness that endothelium alone was not suitable has led to the evolution of techniques to recreate the vascular tissue utilizing multiple cells types. - This approach utilizes the cell types expected in final structure, e.g., endothelium, smooth muscle cells, and fibroblasts, or pluripotential cells such as stem cells. 

TCP is an osteoconductive and resorbable material, with a resorption rate dependent on its chemical structure, porosity, and particle size [10]. 

Leenstag JW, Pennmgs AJ, Bos RRM et al (1987) Resorbable materials of polyl-lactides VI. Plates and screws for internal fracture fixation. Biomaterials 8 70-73... 

Stents are typically inserted to stay in the vessel permanently. After a few weeks it is impossible to remove it, as by then it has become an integral part of the vessel through cellular in-growth. To target situations where stents are used on a temporary basis the stent can be made out of resorbable material. An alternative solution is a new concept where the stent is knitted and the loose ends kept at the end of the tube formation in such a way that it can easily be unravelled. When pulling one of the ends from the outside, the stent will reverse to the thread from which the structure was made and allows the removal of the stent without local anaesthesia (GraftCraft AB, 2014). 

Form and function of resorbable materials—based medical devices... 

The design of a safe and effective device must consider the entire medical device hfe cycle and include considerations about manufacturing, sterility and shelf life. All these steps contribute in creating a reliable device, particularly when resorbable materials are used. 

---