Some parents avoid giving their kids fruit juice, for fear that it might rot their teeth. But the bad effects of juice on a child's oral health could be short-lived, thanks to the remarkable properties of saliva, according to a new study. Saliva protects teeth and gums from bacteria by creating a slippery film on teeth, and also can help repair early damage to tooth enamel, researchers said. Sipping some apple juice temporarily disrupts this protection, but the effect begins to wear off within