Bioglass 45S5
NovaMin is the active ingredient in Sensodyne "Repair & Protect" toothpaste, except when sold in the United States, containing stannous fluoride instead.
Compared to soda-lime glass (commonly used, as in windows or bottles), Bioglass 45S5 contains less silica and higher amounts of calcium and phosphorus.
[6] Bioglass 45S5 is the first formulation of an artificial material that was found to chemically bond with bone, and its discovery led to a series of other bioactive glasses.
He began discussing his research with a fellow traveller on the bus, Colonel Klinker, who had recently returned to the United States after serving as an Army medical supply officer in Vietnam.
[8] After listening to Hench's description of his research, the Colonel asked, “If you can make a material that will survive exposure to high energy radiation can you make a material that will survive exposure to the human body?”[8] Klinker then went on to describe the amputations that he had witnessed in Vietnam, which resulted from the body's rejection of metal and plastic implants.
Ted Greenlee, Assistant Professor of Orthopaedic Surgery at the University of Florida, implanted them in rat femurs at the VA Hospital in Gainesville.
[8] The first successful surgical use of Bioglass 45S5 was in replacement of ossicles in the middle ear as a treatment of conductive hearing loss, and the material continues to be used in bone reconstruction applications today.
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.
When implanted into rabbit femurs, the 45S5 bioactive glass showed that it could induce bone proliferation at a much quicker rate than synthetic hydroxyapatite (HA).
An implant was designed to replace the damaged bone and carry sound from the eardrum to the cochlea, restoring the patient's hearing.
[11] Another area in which bioactive glass has been investigated to use is tooth enamel reconstruction, which has proven to be a difficult task in the field of dentistry.
[13] 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.
The inclusion of fluoride within the glass rather than as a soluble addition, such as the toothpaste BioMin,[15] is claimed to optimise the rate of development of apatite, which shields the teeth from sensitivity for up to 12 hours.
[16] When implanted, Bioglass 45S5 reacts with the surrounding physiological fluid, causing the formation of a hydroxyl carbonated apatite (HCA) layer at the material surface.
Heat treatment of Bioglass reduces the volatile alkali metal oxide content and precipitates apatite crystals in the glass matrix.
However, the scaffolds that result from melt quench techniques are much less porous compared to other manufacturing methods, which may lead to defects in tissue integration when implanted in vivo.
A gel is then formed through hydrolysis and condensation reactions, and it undergoes thermal treatment for drying, oxide formation, and organic removal.
In addition, sol-gel bioglasses have much higher porosity, which leads to a greater surface area and degree of integration in the body.
[25] For example, Touri et al. developed a method to incorporate carbon nanotubes (CNTs) into the structure without interfering with the material's bioactive properties.
By synthesizing Bioglass 45S5 on a CNT scaffold, the researchers were able to create a composite that more than doubled the compressive strength and the elastic modulus when compared to the pure glass.
The authors loaded graphene nanoplatelets (GNP) into the glass structure through a spark plasma sintering method.
Graphene was chosen because of its high specific surface area and strength, as well as its cytocompatibility and lack of interference with Bioglass 45S5's bioactivity.
