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Last Updated: Monday, 5 September 2005, 23:32 GMT 00:32 UK
Minute spheres to cut tooth pain
Nanospheres (Jonathan Earl / University of Leeds)
Nanospheres packing a hole in a tooth
Microscopic spheres could help dentists fill tiny holes in our teeth that make them incredibly sensitive and cause severe pain for millions.

Dental hypersensitivity is a condition that arises when the inner layer of dentine in the tooth is exposed.

Preliminary research shows creating tiny nanospheres of a ceramic material called hydroxyapatite could be a long-term fix.

The Leeds University work was presented to an Institute of Physics conference.

Dentine is made up of thousands of tiny fluid-filled channels which radiate outwards from the nerve endings at the centre of the tooth.

We found these tiny spheres are really good at filling the channels in teeth
Dr Jonathan Earl

Heat, some chemicals, and physical contact can cause the fluid in these channels to move - in or out - triggering the nerve endings and causing sharp pain.

If these channels - or tubules - are fully or partially blocked, the flow can be reduced and the pain stopped or significantly reduced.


Currently, the only way to treat this condition is through good dental hygiene - using special toothpastes and fluorine mouthwashes which encourage re-mineralization of the dentine coating.

The Leeds team have found the most successful particle shape for filling these channels is a nanosphere.

They are now trying to synthesize nanospheres of hydroxyapatite - a ceramic which is highly compatible with teeth and bone.

It is widely used by medics for bone grafts or dental coatings because it binds strongly with the bone material.

The researchers grew hydroxyapatite at various pH levels to vary the size of its constituent particles.

At normal pH, it is composed of long rod-like structures but at high pH levels the particles become smaller and more rounded, better for fitting inside the tiny channels in teeth.

To see whether nanospheres would be successful at filling the channels they used commercially available silica nanospheres of around 40nm in diameter.

Good fit

Researcher Dr Jonathan Earl said: "We found these tiny spheres are really good at filling the channels in teeth, packing inside them quite evenly and going down the holes to a good depth.

"They'd be the perfect shape of particle for filling these channels and reducing or preventing the pain caused by sensitive teeth."

The next stage of their research will be to work out how to synthesize nanospheres of hydroyapatite or a combination of hydroxyapatite and fluorine.

In theory this would not only fill the holes, but also encourage re-mineralization at the same time and so be an incredibly powerful repair tool for dentists.

A British Dental Association spokesperson said: "The results of this study appear interesting.

"The BDA looks forward so seeing further investigation in this area building on the conclusions of this research."

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