Imagine if a dentist could predict how many cavities your child will have later in life just by asking your son or daughter to spit. That may soon become dental reality, say researchers at Southern California University who developed a saliva-based test that measures levels of compounds called sugar chains, or oligosaccharides. These sugar chains have an effect similar to that of “good” and “bad” cholesterol. The good sugar chains repel cavity-causing bacteria, but the bad ones let bacteria bond to teeth and begin decay. The test suggests that genetics have a lot to do with tooth decay—but this doesn’t mean kids should give up the toothpaste and stop seeing the dentist for routine checkups. Instead, researchers hope that eventually the test will help identify those at high risk for cavities so they can tailor preventive measures to individual children.