From the moment on Thursday when the young man sat down in Dr. Richard Stein's dental chair in southwestern Kansas and opened his mouth, Dr. Stein was certain he recognized the enemy. This had to be the work, he concluded, of methamphetamine, a drug that is leaving its mark, especially in the rural regions of the Midwest and the South, on families, crime rates, economies, legislatures -- and teeth.

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.

The condition, known to some as meth mouth, has been studied little in dentistry's academic circles and is unknown to many dentists, whose patients are increasingly focused on cosmetic issues: the bleaching and perfect veneers of television's makeover shows. But other dentists, especially those in the open, empty swaths of land where methamphetamine is being manufactured in homemade laboratories, say they are seeing a growing number of such cases.

These are the same towns, in some cases, that have wrestled in recent years with shortages of dentists. They are places where dentists have struggled to sell their practices as populations shrink; where new dentists have been reluctant to settle, out of fear that they will not get enough business to make ends meet; and where political leaders have offered financial incentives to lure young dentists to town. For good or ill, meth mouth is creating more business.