University of Southern California spit test predicts cavities

A simple saliva test can predict whether children will get cavities, how many cavities they will get and which teeth are most vulnerable.

Developed by researchers at the University of Southern California in Los Angeles, the test quantifies the genetic component of tooth decay, spotting the risk when something can be done about it.

"When we apply this to young children, it allows us to predict what might be their future caries history&mdash;the number of cavities that they'll get by, say, their late 20s or early 30s," says researcher Paul Denny.

Called the Caries Assessment and Risk Evaluation (CARE) test, the test measures the relative proportions in saliva of different types of sugar chains called oligosaccharides. The same sugar chains are present on tooth surfaces.

The effect of sugar chains on teeth's resistance to disease is analogous to the effect of "good" and "bad" cholesterol on blood vessels. "Good" sugar chains tend to repel bacteria that cause cavities while "bad" allow bacteria to bond to teeth and start the decay process. Unlike cholesterol, however, sugar chain makeup in humans is 100% genetically determined.

Denny and colleagues have found that the sugar chain makeup in saliva can predict a child's future cavity history to plus or minus one cavity with greater than 98% confidence.

The findings suggest that in developed areas of the modern era genes play a more significant role in tooth decay than in former times or third world nations where gross malnutrition and negligent oral hygiene held the greatest impact on dental health.