Quite distinct from the oral damage done by other drugs, sugar and smoking, methamphetamine seems to be taking a unique, and horrific, toll inside its users' mouths. In short stretches of time, sometimes just months, a perfectly healthy set of teeth can turn a grayish-brown, twist and begin to fall out, and take on a peculiar texture less like that of hard enamel and more like that of a piece of ripened fruit.