Bioglass puts shine on teeth

A UK innovation could soon give the nation's dental patients a brighter smile and the confidence to indulge in their favourite ice-cold deserts without incurring any pain.

OSspray, a spin-out from Kings College London and Imperial College, has developed a patented compound that can be used with conventional air polishing equipment to buff and whiten teeth while also desensitising them.

The material the company uses is a bioactive calcium sodium phosphosilicate material, or bioglass, which closely resembles tooth enamel. Prof Larry Hench, a pioneer of bioceramics and one of the co-founders of the company, first invented bioglasses in the late 1960s, which were used as bone-graft substitutes for blast victims returning from the Vietnam War.

Dr Ian Thompson, company chief technical officer, first started working with orthopaedic bioglasses, regenerating bone tissue for patients and people who had been in motor vehicle accidents. Through work for a facial surgeon at Guys Hospital, he was put in contact with a dentist who works on fillings and restoring teeth.

'He was interested in a powder they could use to cut teeth, because the old-fashioned mechanical burr that we all love to hate isn't a terribly good cutting tool,' said Thompson. 'It tends to cause sub-surface cracking through the tooth structure.'

This original powder proved unsuccessful as a cutting tool, but the data showed it worked well as a polishing powder, not only removing stains more effectively than the current incumbent, sodium bicarbonate, but also offering desensitisation.

Simon Cartmell, OSspray chairman, said: 'The current technologies for whitening teeth all have disadvantages. Whitening toothpastes are basically ineffective unless under laboratory conditions, hydrogen peroxide is damaging to the teeth if used over a prolonged period, and sodium bicarbonate used in air polishing doesn't do that good a job.'

OSspray's bioglass is a composite of component chemicals loosely held together in a 45 per cent silica network. When the powder, consisting of particles around 50 microns in size, is fired at the surface of the tooth, the compound fractures so it does not damage the surface of the tooth. There is so little silica in that network that the calcium and phosphorus in the structure can imbed into the tooth surface, remineralising and desensitising the surface of the tooth.

'Tooth dentine consists of fluid-filled tubules, like drinking straws,' said Cartmell. 'On the biting surface they are covered with enamel, but in the gumline the tubules are exposed. Our material, because of its particle size and distribution, embeds in the mouth of the tubules, bonding to the surface and locking them off. After repeated use, you build up a thin layer of bioglass, which is remarkably like tooth enamel.'

OSspray manufactures its own powders using a traditional glass-casting technique, where raw reagents are mixed in large crucibles and heated in a furnace. It is now working on a range of other bioglass dental solutions, including orthodontic glues and drilling powders, which will be created by tweaking the chemical properties of the original formula.

Despite the earlier failure, OSspray is now carrying out proof of concept on a powder that can selectively cut just the decayed area of the tooth.

'Where you have a small caries lesion — a little brown spot on the tooth — the dentist would usually go in with the dental burr and overcut the site until the brown spot is no longer visible,' said Thompson.

'Our selective technique will only ever remove that soft, brown, decayed tissue, it will never cut the healthy underlying white enamel and you wouldn't need local anaesthetic.'

The company was recently awarded a £3m investment from Imperial Innovations, the Capital Fund, NESTA and private investors to launch its products in North America and Europe.

'We're intent on launching these products quickly in these markets. It's a classic case of a British technology being bold in its commercial ambitions,' said Cartmell.

Berenice Baker