Applications bone substitute

M. D. Grynpas, R. M. Pilliar, R. A. Kandel, R. Renlund, M. Filiaggi and M. Dumitriu (2002). Porous calcium polyphosphate scaffolds for bone substitute applications in in vivo studies. Biomaterials, 23, 2063-2070. 

Considerable development has occurred on sintered ceramics as bone substitutes. Sintered ceramics, such as alumina-based ones, are uru eactive materials as compared to CBPCs. CBPCs, because they are chemically synthesized, should perform much better as biomaterials. Sintered ceramics are fabricated by heat treatment, which makes it difficult to manipulate their microstructure, size, and shape as compared to CBPCs. Sintered ceramics may be implanted in place but cannot be used as an adhesive that will set in situ and form a joint, or as a material to fill cavities of complicated shapes. CBPCs, on the other hand, are formed out of a paste by chemical reaction and thus have distinct advantages, such as easy delivery of the CBPC paste that fills cavities. Because CBPCs expand during hardening, albeit slightly, they take the shape of those cavities. Furthermore, some CBPCs may be resorbed by the body, due to their high solubility in the biological environment, which can be useful in some applications. CBPCs are more easily manufactured and have a relatively low cost compared to sintered ceramics such as alumina and zirconia. Of the dental cements reviewed in Chapter 2 and Ref. [1], plaster of paris and zinc phosphate... 

The last method to be discussed, which is used to form polymer/ceramic composites by electrospinning, is extremely different to the methods previously described, but worth mentioning. Zuo et al. [129] used a method to create a composite scaffold that is actually the reverse of what most people are doing. Instead of mineralizing the nanofibers, Zuo et al. actually incorporated electrospun polymer nanofibers into a ceramic bone cement in order to form a composite scaffold. It was found that by incorporating electrospun nanofibers into the cement, the scaffold became less brittle and actually behaved similarly to that of a ductile material because of the fibers. Composite scaffolds with different polymers and fiber diameters were then tested in order to determine which scaffold demonstrated the most ideal mechanical properties. However, no cell studies were conducted and this method would most likely be used for a bone substitute instead of for bone regeneration applications. 

Berven S, Tay BK, Kleinstueck FS, Bradford DS. Clinical applications of bone substitutes in spine surgery consideration of mineralized and demineralized preparations and growth factor supplementation. Eur Spine J 2001 10 S169-S177. 

Pilliar RM, Filiaggi MJ, Wells JD, Grynpas MD, Kandel RA. Porous calcium polyphosphate scaffolds for bone substitute applications - in vitro characterization. Biomaterials 2001 22(9) 963-972. 

It is important to emphasize that many natural tissues are essentially composed of nanoscale biopolymers or biocomposites with hierarchical architectures. Therefore, by mimicking the structure and property of their natural counterparts, synthetic nanopoiymers and nanocomposites are very likely to enhance/regulate the functions of specific cells or tissues. This principle has been demonstrated by the success of bioinspired polymers and composites in both clinical practice and in laboratory research. In particular, bone is the hierarchical tissue that has inspired a myriad of biomimetic materials, devices, and systems for decades. This chapter focuses on this well-developed area of biomimetic or bioinspired nanopoiymers and nanocomposites for bone substitution and regeneration, especially those with high potentials for clinical applications in the near future. 

First orthopaedic bone substitute application Smith (3)... 

Alumina and zirconia ceramics are also being used for alveolar ridge reconstruction (20), maxillofacial reconstruction, as ossicular bone substitutes (21), and in ophthalmology (22), knee prosthesis (8), bone screws as well as other applications as dental biomaterials, such as dental crown core, post, bracket and inlay (23,24). 

Nather, A. Bone grafts and bone substitutes basic science and clinical applications. World Scientific Hackensack, N.J., 2005. 

Inorganic particulate fillers such as calcium carbonate and china clay can be compounded with PHB and extruded or moulded. The mechanical properties of the resultant products, however, provide no particular surprises, being stiffer but more brittle than the base polymer. Even so, calcium hydroxyapatite filled PHB is currently being evaluated as a potential bone substitute in maxillofacial surgery, for example, and in fracture fixation plates in much the same way as the recent development of apatite filled polyethylene. The main advantages of PHB over polyethylene (PE) in these applications are its biocompatibility and biodegradability, which will be discussed in more detail later. 

The metal nanoparticles have potential uses in technological and biomedical applications in particular silver ones are widely used due to their well-known antibacterial effects. In medicine silver nanoparticle (Ag-NPs) have found application as wound dressings, surgical instruments and bone substitute biomaterials [65]. 

---