False teeth smeared with a new biocompatible gel that contains molecules of medicinal drugs could revolutionise the treatment of denture stomatitis, a disease affecting up to two thirds of denture wearers, and oral infections such as Candida albicans. The polymer gel, being developed by Ian Sample, a PhD student at Queen Mary & Westfield College in London, UK, will be biocompatible, easy to use and will be more efficacious than traditionally available treatments.
An estimated 40 per cent of the UK's adult population wear dentures with up to two thirds of these suffering from denture stomatitis (pictured) at some stage. The disease is thought to be caused by either poorly fitting dentures, oral infections or poor oral hygiene. Current treatment for denture stomatitis involves the use of a basic polymer gels to cushion the denture against the gum, allowing the gum time and space to heal. These gels are traditionally made by mixing together powdered polyethyl methacrylate (PEM), a liquid containing a plasticiser and up to 50 per cent ethanol. The dentist applies this gel to the denture which is re-fitted to the patient. Within a few hours of application, ethanol can begin to leach from the gel, causing problems with toxicity in the patient's body. After a longer period of time, the plasticiser (phthalate) used in the polymer gel can also begin to leach.
Sample's new gel is made using a copolymer of butyl methacrylate and PEM which is less dense than PEM alone. This means that a gel can be formed in a reasonable amount of time despite the dentist having to use less ethanol (around 2 per cent) in the preparation. The powdered plasticiser used to form the new gel is a high molecular weight citrate that leaches from the material at a much slower rate than the conventional plasticiser and as such has a much superior biocompatibility profile.
By including chlorhexidine, an antifungal drug, in the copolymer powder Sample has been able to produce a gel that can also be used to treat oral infections. Current treatments for oral infections often rely on patients using an antifungal mouthwash or lozenge. "Being inconvenient," says Sample, "this type of regime often falls foul of poor patient compliance, and administering the drug in this fashion leads to inefficient, cyclic levels of drug in the mouth." The new gel slowly releases the drug directly into the infected area over a longer period of time. This, Sample suggests, is a much more effective way of treating the infection as the level of drug in the mouth remains constant throughout the period of treatment.
Tests on the new gel and a commercially available gel laced with the same antifungal drug have shown that after a week in storage the new gel kills 100 per cent of a fungal colony over a 4 hour period compared to 46 hours for the conventional gel. "The commercial conditioner had leached so much during the first week, that its efficacy during the second week was compromised," says Sample. Clinical trials on the gel may begin in the near future. Other applications for this material include attaching it to a tooth to help treat infections in the mouths of patients receiving radiotherapy for oral cancer. Another possible application involves using the polymer gel to allow treatment after facial surgery, delivering antibiotics directly to the site of surgery and possibly even the inclusion of growth hormones to aid wound healing.