1. Clinical application of bioactive glass
The most representative bioactive glass for clinical application is developed by Americans with a composition of (wt%) Na2O 24 5、CaO 24、SiO2 45、P2O56. 0 glass (i.e. Bioglass 45S5). This glass is not only harmless to human body and has good affinity, but also can be firmly combined with natural bones. The binding mechanism can be explained as follows:
Bioglass is implanted into the human body to dissolve Na + from the surface of the glass to form a silica rich sol layer. On the natural bone side of the sol layer, bone growth cells reproduce into bone collagen fibers. With the dissolution of Ca2 + and P5 +, hydroxyapatite crystals are formed around bone collagen fibers and combined together. That is, the combination of active apatite layer and organic matter shows the firm bonding performance between active glass and bone.
Clinical studies show that bioactive glass as artificial bone material is stable for long-term embedding in tissue. 45S5 Bioglass block was placed in animals for a long time without mechanical damage or interface damage.
At present, materials that can be firmly combined with bones and have higher mechanical strength and less fatigue than bones are being explored. Its research directions are: ① strengthening by precipitation of other crystals in apatite glass ceramics; ② The apatite polycrystal was compounded with inorganic fiber for strengthening; ③ Glass, glass ceramics or apatite polycrystals containing CaO and P2O5 are coated on alumina or stainless steel, etc.
2. Clinical application of hydroxyapatite ceramics
The results of animal experiments confirmed that hydroxyapatite was safe in vivo and had good affinity with bone and skin. On this basis, it was used in clinical practice.
At present, hydroxyapatite has been used in artificial tooth root, bone defect, repair and filling of brain surgery at home and abroad; Material for manufacturing ear ossicular chain and plastic surgery.
In addition, hydroxyapatite ceramics are also used in medicine as a drug release carrier implanted in the human body – artificial bone nucleus in the treatment of bone tuberculosis. This application is mainly using hydroxyapatite ceramics (artificial bone core) as an anti tuberculosis drug – Li Fuping carrier, so that hydroxyapatite ceramics containing drugs can be implanted into the tuberculosis foci, continuously releasing drugs, producing high local concentration, killing Mycobacterium tuberculosis, and achieving the purpose of controlling residual infection and preventing recurrence. This method can prevent the side effects of drugs due to the low drug concentration in the whole body.
The hydroxyapatite artificial bone core as a drug delivery carrier requires evenly distributed connecting pores. When the hydroxyapatite artificial bone core filled with powdered drugs is put into the body, because the body fluid is wet to the artificial bone core, under the action of capillary force, the body fluid can enter the core to dissolve the powdered drugs. Because there is a drug concentration gradient inside and outside the nucleus, the high concentration drug solution diffuses to the low concentration, the drug solution outside the nucleus is continuously absorbed, and the drug solution inside the nucleus is continuously exuded until all the drugs are released.
This method can be used to treat thoracolumbar tuberculosis, sacral joint tuberculosis, femoral greater trochanter tuberculosis and other cases.
3. Biological characteristics and application of tricalcium phosphate ceramics
The composition, structure and physical properties of tricalcium phosphate are similar to hydroxyapatite, so its biological characteristics such as biocompatibility and biocompatibility are also very similar to hydroxyapatite. On the basis of animal experiments, clinical applications were also carried out. Because its solubility is greater than that of hydroxyapatite, that is, its bone replacement speed is faster. Therefore, the initial application is to make porous body for filling the bone defect or as skull. After implantation, the new bone slowly enters the hole of the sintered body and will eventually be replaced by its own bone. That is, tricalcium phosphate can induce the growth of new bone and can be swallowed by stromal cells and gradually disappear from the implantation site.
However, at the beginning of the degradation process, its strength is low (lower than that of metal and non degradable materials). When completely replaced by its own bone, its function is better than metal and non degradable materials.
Recently, TCP was coated on metal Ti and TA as artificial bone root. The central part is titanium, and the outer side is a composite of TCP ceramic and polycarbonate. In addition, powdered TCP is also used as a filling material for bone defects caused by periodontal disease.