LONDON (REUTERS) - A dreaded trip to the dentist - and a filling - but has the stuff of nightmares had its day?

A team of researchers at King's College London have regrown teeth in mice - using stem cells.

"We've developed a really simple system. It involves putting a drug on a little sponge that goes inside the tooth, in the hole that the dentist has made. It stimulates this natural process, which is starting to occur anyway following the damage, but it over-activates the process so you actually get the big hole repaired and the repair is a production of the natural material, the dentine," said Professor Paul Sharpe of King's College London Centre for Regenerative Dentistry.

The research repurposes a drug already approved for use in clinical trials to treat Alzheimer's disease - offering a potential fast-track to trials

"So the hope is that that kind of safety data, that's been obtained with very high concentrations, given repeatedly into the bloodstream, will put us in a very good position to go along to the regulatory authorities and say, look, this drugs already had all this safety data, this is the concentration we're using, this is how we're delivering it and our hope is that that will accelerate the time we can get this into a clinical trial and get it into patients," Prof Sharpe added.

The commercially available biodegradable collagen sponges are also already approved - a simple technique with exciting implications for the 3rd world.

"I think this is so much further forward that it really could be quite exciting and offer an alternative when we look at filling materials that are currently available. We're looking at an agreed phase down of silver-amalgam, the silver fillings that we have in our teeth and some of the other composite alternatives whilst very good have question marks over them as well. So actually regrowing the tooth that's been lost with a cavity would be really a huge step forward but it's also important that we remember that we shouldn't be getting the cavity in the first place. We're talking about a totally preventable disease," said Dr Nigel Carter, chief executive of the Oral Health Foundation.

The filling may have serious competition within a matter of years but the dentist's drill still has a future

Any decay needs to be removed and the sponge needs to be inserted in a hole.