Kids’ teeth are under attack by a rising menace, a new study found. When dentists at the University of Texas Health Science Center in San Antonio checked the teeth of 900 local middle-school students, they found that an alarming 30 percent of them were already showing signs of tooth erosion. The culprit, researchers said, is the acidity in soda, sport drinks, and other popular beverages; the acid in those drinks slowly eats away at the protective enamel surface of teeth. Researchers also note that young people today are consuming less protective fluoride than their elders did, because they drink less tap water. Dental erosion often goes untreated in the early stages, since it causes no pain, but it can lead to more serious problems, study author Bennett Amaechi tells LiveScience. “Most patients are not aware that they are suffering from the condition until the problem becomes severe.”