"Mountain Dew mouth"

From a story at NPR:

[O]ver in Appalachia, the region that stretches roughly from southern New York state to Alabama, the fight against soda is targeting an altogether different concern: rotted teeth. Public health advocates say soft drinks are driving the region's alarmingly high incidence of eroded brown teeth — a phenomenon dubbed "Mountain Dew mouth," after the region's favorite drink...

Dentists have also found that the effects of soda on teeth are strikingly similar to the effects of methamphetamine or crack on teeth... Drinking more than a soda a day raises the risk that found in many soft and energy drinks will eat away at your tooth enamel and its pearly white color...

Harris says that dental problems are especially bad because dental care is harder to get in Appalachia, which includes many of the poorest and most remote communities in the country. Many people don't trust the well water in their homes because of pollution concerns and probably drink more soda because of it...

More information at the link.  Photo from a related article at First Choice Dental.