Hench believed there must be a better way of repairing shattered bones and started to work on materials that could bridge a gap where bone is missing. Up until this point biomaterials had been designed to be inert. But Hench realised that if a material could bond with bone the connection would be stronger. He started with the idea that as bone is primarily made of calcium and phosphorus, the material would need a source of this to bond with bone.
Two years later, after experimenting with different combinations of minerals, he found the right balance of calcium, phosphorus, sodium and silicate and Hench’s first bioactive glass was created. Trademarked as BIOGLASS, it has been successfully used in medicine ever since to mend bones and accelerate bone growth.
Like repairing holes in wall
If it hadn’t been for more inquisitive scientists, the story may have ended there. But in 1996 two dentists, Dr Len Litkowski and Dr Gary Hack, who were studying sensitive teeth, along with researcher Dr David Greenspan, experimented with using BIOGLASS on teeth. Teeth, like bones, are primarily made of calcium and phosphorus, and it was this structural similarity that made them consider experimenting.
Dental hypersensitivity is caused by tiny holes in the dentine – the material which lies under the enamel and makes up the bulk of the tooth - that allow sensations like hot and cold to reach the nerves. The hypothesis was that BIOGLASS could fill the holes and stop the sensation reaching the nerves.
Their experiments showed that in the presence of water or saliva, calcium, sodium, silica and phosphorus react to form a calcium phosphate layer which crystallises to form hydroxyapatite. Hydroxyapatite is similar both chemically and structurally to the minerals in teeth and works to fill the holes, similar to using filler to repair holes in a wall. They called their formulation NovaMin, and at first it was only used in a few small products.
In 2001, GSK acquired the Sensodyne brand and the Oral Healthcare R&D team soon started to think about how they could move the brand forward from a technology and science perspective, building upon its strong heritage. They wanted innovative technologies based on thorough scientific research to differentiate GSK’s Oral Healthcare products. This led them to investigate NovaMin.