The implants are inserted into the bone of the jaw, which then grows around them, embedding them firmly in place. After installation, the implants are left for three months in the lower jaw and six months in the upper jaw to ensure that the bone joins on to them.
Dental implantation is now a routine procedure for patients who have lost teeth in accidents, young people who do not grow the full complement of teeth, and those who find it impossible to wear dentures, either because of the way their mouths are formed or because of severe gagging problems.
However, some patients have been incapable of this treatment because of a lack of bone in which the implants could be installed. Now researchers at the United Medical and Dental School at Guy's and St Thomas's Hospital, London, have succeeded in promoting bone regrowth in the jaws of four patients who need implants because they are unable to wear dentures.
The principle of guided bone-tissue regeneration was developed in the early 1980s but, according to Richard Palmer of the Department of Periodontology, this is the first time it has been proved to work in dental implant treatment.
The technique involves preparing the site of the implant and covering it with a barrier membrane made from Gore- Tex, best known as a weather- proof clothing fabric.
'The Gore-Tex cover acts like a tent, protecting the bone and preventing other cells such as connective tissue growing into the surgical site to compete with the bone cells,' Dr Palmer says.
'We have been able to verify that the regenerated tissue is bone. This is the first evidence of this in human subjects.'
It will be about a year before the researchers know whether the regenerated bone is strong enough.
A single tooth implant fitted by a private dentist would cost around pounds 1,500, but implant treatment is available on the National Health Service for people who need it for medical rather than cosmetic reasons. Dr Palmer says discussions are now under way over which conditions should be treated with implants.