Scientists have developed a mouthwash that allows plaque-causing bacteria to be destroyed using nothing more than a bright light.

It works using the same principles as some skin cancer treatments.

Leeds Dental Institute say it may be available inside three years for home use - perhaps with the light attached to the head of a toothbrush.

The same team is also working on a "repair solution" to help the body grow new enamel.

They believe this could reduce the need for "drilling and filling".

Both projects are being spearheaded by Professor Jennifer Kirkham, who believes they could make a big difference to dental care.

The mouthwash uses "photodynamic therapy", and Professor Kirkham sees it as a way to help people who find it hard to use a toothbrush.

Antibacterial molecules in the liquid are absorbed only by plaque-causing bacteria, and activated when a bright light is shone into the mouth, killing them.

Cancer application

The same technique is used in certain types of skin cancer, with the substance painted on the target area, taken up by cancer cells, then exposed to light of a certain wavelength, which activates it to kill the cancer cell.

Although the molecule is known to be safe for human consumption, full trials have yet to be completed.

Prof Kirkham said: "The laboratory is looking to find safe new ways to control plaque which do not rely on toothpaste.

"We see patients in the clinic who are not able to brush effectively - the shape of the mouth may not allow sufficient access, the patient could be disabled or just not a proficient brusher."

Machines offering photodynamic therapy in dental clinics already exist, but another researcher, Dr Simon Wood, said that the aim was to find a way the mouthwash could be used at home.

He said: "In our experiments, we've been using standard white light - I've been using a conventional security light.

"While you'd need a bright light to make it work, you could in theory have something in the head of a toothbrush."

Self-repair

The "repair solution" is made from a protein which encourages the laying down of new enamel over microscopic holes in teeth, including those caused by acid produced by plaque bacteria.

The liquid is painted on, enters the holes, then attracts the calcium needed to patch them.

Prof Kirkham said it could help people with early damage which could eventually lead to dental decay, or who have tiny holes in their teeth which make consuming hot or cold food or drink painful.

The repair solution will not eliminate the need for the dentist's drill - bigger cavities filled with decay would still have to be treated in the conventional way.

It is hoped that it will enter trials next year, and gain a licence for wider use within five years.