Dental fillings of the future will be custom-built by a computer from porcelain, according to researchers from Liverpool University.

They will be tooth-coloured and will last much longer than normal fillings.

The dental surgery of the next millennium was unveiled last week at the annual meeting of the British Dental Association in Birmingham. It uses CAD-CAM (computer aided design and computer-aided manufacture).

In future the patient will lie back while the dentist scrapes out old fillings and decay. Then, a three-dimensional camera will scan the remaining hole.

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The camera data will feed into a computer which will design a filling to fit, cut it out using a miniature milling machine, and produce it for the patient within ten minutes.

The fillings will be tooth-coloured porcelain instead of silver-coloured dental amalgam and will last longer than amalgam, which can corrode to half its size within five years, says Nicolas Jedynakiewicz, lecturer in clinical dental science at Liverpool University.

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Porcelain, he hopes, will last for decades, although he is still working out just how long.

The new filling will stick to the remaining bits of tooth - unlike current fillings, which just slot in but are not adhesively joined. "So the remaining parts of your tooth are less likely to break away", said Dr Jedynakiewicz. He and Nicolas Martin, also at the university, are now checking how the porcelain sticks and whether or not the fillings leak.

The display will also feature a technique that Dr Jedynakiewicz is teaching students: taking X-rays of the mouth that appear immediately rather than taking several days to be processed.

At present, when an X-ray is taken, a roll of film is put into the patient's mouth. Using the new technique, an imager is put into the mouth instead, which sends the X-ray photograph directly to a screen. The system is very sensitive so the X-ray dose is lower.

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