Do Dou Really Know about Bioactive Ceramic?

Bioceramic materials are classified into bioactive ceramic materials and bioinert ceramic materials according to their combination with tissues. This article mainly introduces bioactive ceramic materials.

Bioactive ceramics

Bioactive ceramics include surface bioactive ceramics and biodegradable ceramics. The composition of these materials contains elements such as calcium and phosphorus that can be replaced by the normal metabolic pathways of the human body; or contains hydroxyl groups (OH-) that can bond with human tissues, and their surface can achieve complete affinity with human tissue through bond bonding; or partially or completely absorbed and replaced by the human body. Therefore, bioceramics can be used as a scaffold and vacancy filling body for infiltration or replacement of body components. However, the strength of this kind of bioactive ceramics is severely reduced during the absorption process, especially the fully absorbable bioceramics. Therefore, mechanical design factors must be carefully considered so that the body tissue and bioactive ceramics do not rupture in the middle stage of healing.

Classification of bioactive ceramic materials

Hydroxyapatite

Hydroxyapatite (HAP), abbreviated as HAP, has the chemical formula (Ca10(PO4)6(OH)2). It is a surface active material. Since the main component of the hard tissues (teeth and bone) of the living body is hydroxyapatite, some people also call hydroxyapatite ceramics artificial bone.

Advantages: The composition and structure of the human bone crystal are basically the same. It has the characteristics of good biological activity and biocompatibility, non-toxic, non-rejection, non-carcinogenic, degradable, and can be directly combined with bone. It is used as a filling material for bone defects, can provide a scaffold for the formation of new bone, play the role of bone conduction, and is an ideal hard tissue substitute material.

Disadvantages: low strength and high brittleness; limitations of low flexural strength, poor toughness and mechanical properties, etc., have affected its wide application in clinical medicine. But this does not affect people's research on various composite materials of the HAP series to obtain biomedical composite materials with excellent mechanical properties and good biological activity, such as: the combination of hydroxyapatite and metal; the hydroxyapatite is compounded with inert bioceramic materials; the hydroxyapatite is compounded with organic matter.

Bioactive glass

In 1969, Professor Hench of the University of Florida in the United States first developed bioactive glass (BG) and applied it to the field of biomedicine for the first time, creating a new field of biomaterial research—bioactive glass and bioactive glass ceramics. Bioactive glass is a silicate glass material with a special composition and structure. BG has a composition similar to that of natural bone. It has good biocompatibility and can directly chemically bond with biological tissues. After being implanted in the human body, it can participate in metabolism. It is a good type of artificial bone (tooth) material to grow bone tissue.

Advantages: It has good biocompatibility and can form bond; it has stronger bonding strength than HAP and metal implant; it has faster osteogenesis and is conducive to the early retention of implant; the porosity can be selected according to the applicable target.

Disadvantages: Compared with human bones, bioactive glass is more brittle, especially the lack of bending strength, which severely limits the application range of this type of material. It is composed of a series of subsequent processing by melting at about 1400?. The preparation process is complex. High temperature volatilization and pollution can lead to fluctuation of product composition and unstable performance.

Tricalcium phosphate ceramic material

Tricalcium phosphate, molecular formula Ca3(PO4)2, referred to as TCP, has a calcium-phosphorus ratio of 1.5, which is very similar to that of normal bone tissue, has good biocompatibility, and has no rejection reaction with bone integration. The currently widely used biodegradable ceramic is?-tricalcium phosphate (?-TCP for short), which is a high-temperature phase of calcium phosphate.

Advantages: Compared with HAP, the biggest advantage of TCP is that it is easier to dissolve in the body. After being implanted in the body, it is directly fused with bone and absorbed by bone tissue. It is a bone reconstruction material. According to the different bone properties of different parts and the requirements of the degradation rate, a hollow structural member with a certain shape and size can be made to treat various orthopedic diseases.

Disadvantages: Calcium phosphate ceramics have high brittleness and are difficult to process or fix holes. However, dense calcium phosphate ceramics can improve their fracture toughness by adding an enhancement phase, and although porous calcium phosphate ceramics can be greatly enhanced by new bone ingrowth, they must also be toughened and strengthened in order to replace their function early before the complete formation of remodeling bone.

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