Silicon nitride (Si3N4) is a kind of ceramic material with excellent structure and function integration. It is widely used in machinery, metallurgy, chemistry, Aviation, semiconductor and other fields.
With the continuous deepening of biomedical materials research, it has been found that silicon nitride ceramics not only have good biocompatibility and osteoconductivity, but also exhibit good affinity with biological tissues such as cells, and also have good biocompatibility and osteoconductivity. Imaging performance, is an ideal human implant material.
Advantages of Silicon Nitride as a Human Implant Material
Biocompatibility
In order to ensure the safety of clinical application, human implant materials must have good biocompatibility. Good biocompatibility is embodied in that the interaction between the material and the organism tissue does not cause obvious clinical response, and does not produce biological rejection and destruction in the host. The cytotoxicity assay is one of the most commonly used in vitro assays for testing biocompatibility. The cytotoxicity and applicability of dense silicon nitride as biomaterials were investigated by the researchers using dense silicon nitride samples (SN1, SN4) of two different sintering aid systems, Al2O3-Y2O3-Yb2O3 and Al2O3-Y2O3. In vitro cytotoxicity assay. The results showed that the two silicon nitride system samples and their preparation process were negative for cytotoxicity, and the content of free Si4+ (0.02ppm~0.05ppm) and other ions (Al3+, Y3+, Yb3+) content (<0.006ppm) were all traces , not enough to be toxic, thus proving that silicon nitride ceramics are a very promising biomaterial.
Radiographic
Silicon nitride ceramics can block the transmission of radiation well, and as a biological implant material, it is more clear in X-ray imaging. In addition, silicon nitride ceramics are non-magnetic, and can clearly show the integration of peri-implant tissues on computed tomography (CT) and magnetic resonance (MRI) imaging, without producing the usual observations around titanium alloy implants. Radial artifacts.
Antibacterial
The implant material must be able to inhibit the production and attachment of bacteria and reduce the occurrence of inflammation in the tissue adjacent to the implant. The researchers studied the growth of three common bacteria (Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa) on silicon nitride, titanium alloy, and polyetheretherketone through in vitro experiments. The study showed that after 72h culture, the biofilm yields of Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa on silicon nitride were 1/4, 1/5, 1/10 and 1/10 of that of PEEK, respectively. 1/2, 2/3, and 1/4 of the titanium alloy, indicating that silicon nitride can reduce the formation of biofilm and the number of bacteria without relying on antibiotics.
Osteoconductivity
In foreign countries, a large number of animal implantation experiments have been carried out in terms of osteoconductivity. After implanting silicon nitride into the tibia of rabbits for two months, Guedes et al. observed by histology and scanning electron microscope that the tissue around the implant had good compatibility, no side effects, and the new bone tissue grew well, and the silicon nitride surface had Bone bridge is formed, indicating that it has good bone conduction properties.
Application of Silicon Nitride as Human Implant Material
Dentistry
Silicon Nitride Dental Implants
At present, the commonly used dental implant materials are PEEK, titanium alloy and so on. PEEK has poor mechanical strength, biocompatibility, and bonding properties; titanium alloys are complex in production process, high in price, low in surface activity, and not resistant to wear, which can easily cause allergic reactions and gingival recession in patients. Silicon nitride ceramics can avoid the above problems to a large extent due to its excellent comprehensive properties. It is a promising new dental implant material. At present, bone nails, surgical steel plates, screw shafts, etc. for dental implants have been developed. and test.
Silicon nitride post and core crown
Due to the existence of micro-leakage, metal post-core crowns will be oxidized to different degrees, and metal ions will be precipitated after long-term use, causing color infiltration to the gingival teeth. The all-ceramic post and core crown does not have the problem of oxidation, and will not affect the basic color of the gums and teeth.
Application of Silicon Nitride as Human Implant Material
Hip and Knee
Artificial hip and knee replacement weight-bearing surfaces require biomaterials with low wear rates and good coefficients of friction that can maintain a stable life span in the human body for decades. The mechanical properties of dense silicon nitride ceramic materials are superior to those of alumina-based ceramics and composites currently used in total hip and knee replacements. When in contact with itself or CoCr alloys, silicon nitride has a lower wear rate than alumina to alumina articular surfaces and is the lowest of any articular surface material used in orthopedic surgery. Therefore, silicon nitride is a good material for artificial hip and knee joint prostheses, especially when this material rubs against itself in water, it has very good tribological properties.
Craniomaxillofacial
Craniomaxillofacial surgery (CMF) involves the correction of congenital and acquired conditions of the head and face. In the United States, a large number of patients require surgery for these types of diseases. Historically, pre-formed metal, polymer or bioactive ceramic implants have been used in situations requiring bone repair or replacement. However, these materials have an average failure rate of 5.5%, and the resulting infection, material corrosion, degradation and fracture, often requires surgical repair, debridement, long-term antibiotic use and implant replacement, so better materials are needed to overcome these questions. At present, the application of silicon nitride implant materials in craniomaxillofacial surgery is relatively potential. Compared to existing materials, it has been shown to accelerate bone healing, reduce infection rates, eliminate metal toxicity, enhance imaging studies, reduce patient pain and disability, and reduce the overall healthcare burden associated with failed implants.
Cervical spine, spine
Cervical spacers and spinal cages made of silicon nitride composites have been put into use with successful clinical results. Especially in the spine, the implant material for spinal interbody fusion surgery made of porous silicon nitride has been clinically used in Australia for more than 15 years; dense silicon nitride has been implanted in spine applications in the United States for more than 3 years.