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Applications:

Bioactive glass offers good osteoconductivity and bioactivity, it can deliver cells and is biodegradable. This makes it an excellent candidate to be used in tissue engineering applications. Although this material is known to be brittle, it is still used extensively to enhance the growth of bone since new forms of bioactive glasses are based on borate and borosilicate compositions. Bioglass can also be doped with varying quantities of elements like Copper, Zinc, or Strontium which can allow the growth and formation of healthy bone. The formation of neocartilage can also be induced with bioactive glass by using an in vitro culture of chondrocyte-seeded hydrogels and can serve as a subchondral substrate for tissue-engineered osteochondral constructs.

The borate-based bioactive glass has controllable degradation rates in order to match the rate at which actual bone is formed. Bone formation has been shown to enhance when using this type of material. When implanted into rabbit femurs, the 45S5 bioactive glass showed that it could induce bone proliferation at a much quicker rate than synthetic HA. 45S5 glass can also be osteoconductive and osteoinductive because it allows for new bone growth along the bone-implant interface as well as within the bone-implant interface. Studies have been conducted to determine the process by which it can induce bone formation. It was shown that 45S5 glass degrades and releases sodium ions, as well as soluble silica, the combination of all these ions is said to produce new bone. Borate bioglass has proven that it can support cell proliferation and differentiation in vitro and in vivo. It also has shown that it is suitable to be used as a substrate for drug release when treating bone infection. However, there has been a concern as to whether or not the release of boron into a solution as borate ions will be toxic to the body. It has been shown that in “static” cell culture conditions, borate glasses were toxic to cells, but in “dynamic” culture conditions.

Another area in which bioactive glass has been investigated to use is enamel reconstruction, which has proven to be a difficult task in the field of dentistry. Enamel is made up of a very organized hierarchical microstructure of carbonated hydroxyapatite nanocrystals. It has been reported that Bioglass 45S5-phosphoric acid paste can be used to form an “interaction layer” that can obstruct dentinal tubule orifices and can therefore be useful in the treatment of dentin hypersensitivity lesions. This material in an aqueous environment could have an antibacterial property that is advantageous in periodontal surgical procedures. In a study done with 45S5 Bioglass, control biofilms of S. sanguis were grown on inactive glass particulates and the biofilm grown on the Bioglass was significantly lower than those that were on the inactive glass. It was concluded that Bioglass can reduce surface bacterial formation, which could benefit post-surgical periodontal wound healing. The most effective antibacterial bioactive glass is S53P4, which has exhibited a growth-inhibitory effect on the pathogens that was tested on it. Bioactive glasses that are sol-gel derived, such as CaPSiO and CaPSiO II, have also exhibited antibacterial property. Studies done with S. epidermidis and E. coli cultured with bioactive glass have shown that the 45S5 bioactive glass have a very high antibacterial resistance. It was also observed in the experiment that there were needle-like bioglass debris which could have ruptured the cell walls of the bacteria and rendered them inactive.

Bioactive glass has even been applied to medical devices to help restore the hearing to a deaf patient using Bioglass 45S5 in 1984. The patient went deaf due to at ear infection that degraded two of the three bones in her middle ear. An implant was designed to replace the damaged bone and carry sound from the eardrum to the cochlea, restoring the patient’s hearing. Before this material was available, plastics and metals would be used because they did not produce a reaction in the body, however they eventually failed because tissue would grow around them after implantation. A prosthesis made up of Bioglass 45S5 was made to fit the patient and most of the prosthesis that were made were able to maintain functionality after 10 years. The Endosseous Ridge Maintenance Implant made of Bioglass 45S5 was another device that could be inserted into tooth extraction sites that would repair tooth roots and allow for a stable ridge for dentures.

This material has also been used in jaw and orthopedics applications, in this way it dissolves and can stimulate the natural bone to repair itself. GlaxoSmithKline is using this material as an active ingredient in toothpaste  under the commercial name NovaMin, which can help repair tiny holes and decrease tooth sensitivity. Currently, bioactive glass is still be researched and has yet to reach its full capacity of use.

How It’s Made:

Bioglass 45S5 is manufactured by conventional glass-making technology, using platinum or platinum alloy crucibles to avoid contamination. Contaminants would interfere with the chemical reactivity in organism. Annealing is a crucial step in forming bulk parts, due to high thermal expansion of the material. Heat treatment of Bioglass reduces the volatile alkali metal oxide content and precipitates apatite crystals in the glass matrix. The resulting glass-ceramic material, named Ceravital, has higher mechanical strength and lower bioactivity [5]. When Larry Hench first manufactured the material in 1969, he used the method of melting a mixture of oxide precursors, which include 46.1 mol% SiO2, 24.4 mol%Na2O, 26.9 mol% CaO, and 2.6 mol% P2O5 at high temperatures. The first batch of derived bioglass was melt-derived and given the name Bioglass [21], [22].