Bioceramic types

Our researchers have worked very hard to accomplish our goals by doing things we felt would enhance our synthetic bone materials and their performance to enable them to equal and often exceed the performance of autograft as implants as well as in other types of bone augmentation and replacement. The nonporous tooth enamel solid calcium phosphate materials have flexural strengths of over 20,000 lb in.2 However, without pores it would take an extremely long time to resorb this nonporous bioceramic. 

In Fig. 7, electron microscope photographs of two different types of high-po-rosity bioceramics are shown. The bone material on the left has 250- j. pore size with a background of micropores [Fig. 7(a)], The specimen on the right-hand side has 400- i pores with a background of 250-p pores as well as displaying micro-porosity within the pores [Fig. 7( >)]. We are also able to regulate the size and distribution of porosity in our bioceramic materials. 

Bone is a natural composite comprised of type I collagen and calcium phosphate minerals, of which nanocrystalline apatite is the main component [39, 40]. Certain osteoconductive bioceramics exert an effect on bone cell attachment and growth factor binding or release, and can accelerate the treatment of bone defects [41-43]. Polymer composite scaffolds can be produced, via electrospinning, which contain a specific amount of electrical charge in order to form non-woven fibrous meshes with fibre dimensions in the nano- to microscale [44-46]. 

CaP synthesis methods and their technological parameters can significantly impact stoichiometry of the synthesis product, its grade of crystallization, particle size, bioceramic phase composition, thermal stability, microstructure and mechanical properties. The important technologic parameters that impact properties of calcium phosphate synthesis product and then also of bioceramic, are temperature of synthesis, pH of synthesis environment, reagent type and concentration, as well as selection of raw materials, their purity and quality. All of the above mentioned also brings a significant impact on the tissue response of these bioceramic implants. 

An additional parameter that should be considered in evaluating chemical stability and surface activity of bioceramics is the simulated in vivo environment. Factors such as the type and concentration of electrolytes in solution and the presence of proteins or cells may influence in vitro immersion results. For example, in a study on glass-ceramic A-W that can be generalized to other bioceramics, a solution with constituents, concentrations, and pH equivalent to human plasma most accurately reproduces in vivo surface structural changes, whereas more standard buffers do not reproduce these changes (Kokubo et al., 1990b). Such control of the ionic environment also forms the basis for biomimetic approaches discussed in the last section of this chapter. 

Figure 6.3 Time dependence of interfacial bone formation for various types of bioceramic implants.

Bioceramics is a generic term that covers all inorganic, nonmetaDic materials that have been used in the human body as implants or prostheses. According to the type of tissue attachment, there are three types of bioceramics bioinert, bioactive, and bioresorbable [1,6]. Inert bioceramics are biol( caUy inactive, with a characteristic lack of... 

Active enzymes were encapsulated into a sol-gel matrix for the first time in 1990 719 About 60 different types of hybrid bioceramic materials with inotganic matrices made from silicon, titanium, and zirconium oxides Ti02-cellulose composites etc. were described. Recentiy, bioceramic sensors, solid electrolytes, electrochemical biosensors, etc. have been surveyed in a review. The moderate temperatures and mild hydrolytic and polymerization conditions in sol-gel reactions of alkoxides make it possible to trap proteins during matrix formation. This prevent proteins denaturation. The high stability of the trapped biomolecules, the inertness, the large specific surface, the porosity, and the optical transparency of the matrix facilitate use of sol-gel immobilization. The principal approaches ate considered below. 

Aramugam MQ, Ireland DC, Brooks RA, Rushton N, Bonfield W (2006) The effect of orthosilicic acid on collagen type 1, alkaline phosphatase and osteocalcin mRNA expression in human bone-derived osteoblasts in vitro. Bioceramics 18 (1-2) Key Engn Mater 309-311 121-124 Batchelor L, Loni A, Canham LT, Hasan M, Coffer JL (2012) Manufacture of mesoporous silicon from living plants and agricultural waste an environmentally friendly and scalable process. Silicon 4 259-266... 

Bioceramic materials have developed into a very powerful driver of advanced ceramics research and development. For many years bioceramics, both bioinert materials such as alumina, zirconia and, to a limited extent titania (Lindgren et al., 2009), and bioconductive materials such as hydroxyapatite, tricalcium phosphate and calcium phosphate cements, have been used successfully in dinical practice. In addition, applications continue to emerge that use biomaterials for medical devices. An excellent account of the wide range of bioceramics available today has recently been produced by Kokubo (2008), in which issues of the significance of the structure, mechanical properties and biological interaction of biomaterials are discussed, and their clinical applications in joint replacement, bone grafts, tissue engineering, and dentistry are reviewed. The type and consequences of cellular responses to a variety of today s biomaterials have been detailed in recent books (Di Silvio, 2008 Basu et al., 2009 Planell et al., 2009). 

Biodegradable bioceramics, 39-9 Biodegradable linear aliphatic polyesters, 42-3-42-9 Biodegradable or resorbable ceramics, 39-8-39-16 Biodegradable polymeric biomaterials, 40-12-40-13,42-1-42-16 biodegradable linear aliphatic polyesters, 42-3-42-9 non-aliphatic polyesters type biodegradable polymers, 42-9-42-10 Biodegradation, see also... 

A strong interest in the use of ceramics for biomedical engineering applications developed in the late 1960 s. Used initially as alternatives to metallic materials in order to increase the biocompatibility of implants, bioceramics have become a diverse class of biomaterials presently including three basic types relatively bioinert ceramics maintain their physical and mechanical properties in the host and form a fibrous tissue of variable thickness surface reactive bioceramics which form a direct chemical bonds with the host and bioresorbable ceramics that are dissolved with the time and the surrounding tissue replaces it. 

A review of the composition, physicochemical properties and biological behaviour of the principal types of bioceramics is given, based on the literature and some of our own data. The materials include, in addition to bioceramics, bioglasses and bio-glass-ceramics. Special attention is given to structure as the main physical parameter determining nor only the properties of the materials, but also their reaction with the surrounding tissue. 

Biodegradable or resorbable As the name implies, the ceramic dissolves with time and are gradually replaced by the natural tissues. A very thin or non-existent interfacial thickness is the final results. This type of bioceramics would be the ideals, since only remain in the body while their function is necessary and disappear as the tissue regenerates. Their greater disadvantage is that their mechanical strength diminishes during the reabsorption process. One of the few bioceramics that fulfil partially these requirements is the tricalcium phosphate (TCP). 

Dense or porous bioactives bioceramics. The bond to the tissue is of chemieal type and the fixation bioaetive. Typical example of the group is HA, bioglasses and bioactive glass-... 

Carbon presents a great variety of forms amorphous carbon, graphite, diamond, vitreous carbon and pyrolitic carbon. Some of them display the most excellent properties of biocompatibility, chemical inertia and thromboresistance that any other bioceramic. On the other hand, another advantage of these materials is that their physical characteristics are next to those of the bone [40]. Thus, their densities, according to the type carbon, change between 1.5 - 2.2 g/cm, and their elastic modules between 4-35 GPa. In spite of all the mentioned... 

The appearance of this type of bioceramics bom of the need to eliminate the interface movement that takes place with the implantation of bioinert ceramics. Consequently, L. L. Hench proposes in 1967 to the U.S.A. Army Medical Research and Development Command, a research based on the modification of the chemical composition of ceramics and glasses so that they have chemical reactivity with the physiological system and form chemical bond between the adjacent tissue and the surface of implant materials. 

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