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Mimicking Saliva

Saliva provides perhaps the most effective means of ridding the mouth of harmful bacteria. Indeed, without enough saliva, the 2 million people with Sjogren’s syndrome, which causes severe drying of mucosal surfaces, suffer a variety of oral infections. So, too, do millions of people whose saliva glands are affected by radiation treatments for head and neck cancers, bone-marrow transplants, some chemotherapy, or the more than 400 prescription and over-the-counter drugs that have been reported to cause mouth dryness.

Unfortunately, a quest to develop artificial saliva has proven largely unsuccessful. The main reason is that many of its components have not even been identified, says Philip Fox, clinical director of the National Institute of Dental Research (NIDR). These include the viral and bacterial components, as well as the myriad substances that aid in chewing, initial digestion, and swallowing. Researchers therefore haven’t been able to replicate its physical and chemical properties, nor have they been able to identify all the ways in which it contributes to the functioning of the mouth as an ecosystem.

Until they can say exactly what saliva is, NIDR researchers such as Fox are focusing instead on other options. For people who retain some part of their saliva gland, researchers have had success with a drug, pilocarpine, that stimulates the gland to produce more saliva. They are also searching for ways to control Sjogren’s syndrome through the use of steroids and other drugs that aim to calm down the immune response that shuts down saliva glands.

“We’re also attempting to reengineer the saliva gland,” says Fox, by using gene-transfer technology to try to reconstitute a damaged gland. In one method, NIDR researchers Brian O’Connell and Bruce Baum are using standard gene-transfer technology in which a virus that infects a cell is used to carry a gene that will cause the cell to produce a substance that its own DNA is not programmed to produce. When salivary glands have been damaged by radiation or disease, cells may still be there, but they are not water-secreting cells. In animal studies, the researchers have been able to transfer genes into cells and get them to produce water. Fox says that within two to three years, the same techniques may be able to be used on humans.

Because the field of oral ecology is at its beginning stages and the fruits of the new research still need to go through the long process of clinical trials, most new techniques will not see the inside of people’s mouths for 5 to 10 years, say researchers. Until then, Bonta of Colgate Oral Pharmaceuticals advises that “although you can afford not to brush for 72 hours, if you pass that threshold, the bacteria will have taken hold and multiplied to such concentrations that the acid they produce has begun making holes in the teeth. Moreover, you may not be able to remove the plaque and bring the infected parts of the teeth back to health.”

It’s also best to brush for more than a minute, says Ernest Newbrun, a dental researcher in the University of California at San Francisco’s Department of Oral Biology. That’s the effort required to clean the 150 tooth surfaces found in most people’s mouths and to bring the bacteria count down to a manageable and healthy 1,000 to 100,000 per tooth.

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Tagged: Biomedicine

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