Predicting cavities
The sad truth is this: Some people are almost destined to suffer from tooth decay -- regardless of whether they drink fluoridated water, avoid sweets, and brush and floss with determination.
They can blame their genes. The tendency to develop cavities is inherited. On the other hand, family history isn’t always a good indicator of risk.
Soon a new saliva test may be able to identify those most at risk for cavities, how many they’re likely to develop and even predict which parts of the mouth are the most vulnerable. That way, preventive steps can be taken before cavity-causing bacteria take hold in the mouth.
The test would be most beneficial for children; by adulthood, decay has taken root.
“This is exciting research,” says Dr. Lawrence A. Tabak, a dentist and director of the National Institute of Dental and Craniofacial Research in Bethesda, Md.
“A test that would identify children who are most at risk for dental decay would be a tremendous step forward because it would allow us to target preventive measures in a highly focused way,” Tabak said.
Developed by USC School of Dentistry scientists, the Caries Assessment and Risk Evaluation test measures sugar proteins in the saliva; these sugar chains also coat the surfaces of the teeth.
These proteins’ effect on the teeth is similar to the way “good’ and “bad” cholesterol act on blood vessels, says Paul Denny, a USC saliva researcher and a co-inventor of the test.
Certain combinations of sugar proteins fend off the bacteria that cause tooth decay (dental caries), while others promote decay by allowing the microbes to stick to the tooth’s surface.
Although being cavity-prone is genetic, family history isn’t always a good predictor.
“There is case after case of parents who have great teeth and their children who have rotten ones, and vice versa,” says Denny. “How these genes are parceled out to prevent caries is an extremely complicated process, and every single sugar protein chain is a composite of up to 20 or 30 different genes.”
The saliva test uses a piece of paper that is dipped into the person’s saliva and then bathed in a battery of sensitive chemicals that can detect the presence of these different sugar proteins.
“The color the saliva spot turns can tell you the person’s risk level,” says Denny.
In a 2004 study, the saliva of 29 children ages 7 to 10 was compared to the saliva of 20 young adults, revealing that the makeup of sugar chain proteins could predict a child’s cavity history with more than 98% accuracy.
More long-term research is needed, but Denny hopes the test will be available in dental offices within several years.
The test will enable families to take preventive measures, such as applying sealants to vulnerable teeth before the caries form.
The sealants can help prevent caries from getting established in the mouth and stop the lifelong process of deterioration that often leads to costly and painful root canals, crowns and loss of teeth.
Because sealants can be expensive, knowing which teeth -- or which people -- are more vulnerable could allow the sealants to be targeted only to potential trouble areas and could open the door for better insurance reimbursement.
“In the future,” says Denny, “even a kid at the highest risk could arrive at adulthood without any cavities, with the proper preventive dental care.” *
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The saliva test as diagnostic tool
Saliva may eventually supplant blood and urine as the favored fluid for detecting disease. Because saliva tests don’t require a needle or the collection of urine in a cup, they are easier to administer, more convenient and much less expensive.
“They’re pain-free and as user friendly as possible because you just have to spit in a tube,” says Dr. David T. Wong, a saliva researcher at UCLA’s Jonsson Comprehensive Cancer Center and School of Dentistry.
Saliva tests are already used to detect HIV, blood alcohol levels and illicit drugs. But they may soon be able to identify a host of diseases. In a 2004 study of 64 patients, for example, half of whom had head and neck cancers, researchers found that measuring elevated levels of cancer-related molecules in saliva enabled them to distinguish with 91% accuracy the cancer patients from the healthy control group.
Scientists at UCLA and other research centers are deciphering the set of proteins normally present in saliva, and the signature proteins produced by breast and ovarian cancers, heart disease, osteoporosis, rheumatoid arthritis, diabetes, Alzheimer’s disease and even viral and bacterial infections.
“We’re looking for a biochemical marker or fingerprint for these disease processes,” says Wong, describing the first step in devising a diagnostic test.
