Fluorosis, characterized by brown stains on teeth, can result from massive fluoride intake in drinking water.

“you have these big brown stains on the teeth but the hots have a lot of those brown stains and it's hard to know whether that's smoking marijuana fluoride in the water you know where they getting it from are they getting a contaminated river but i don't think that the hots necessarily have cavities as much as they have a lot of brown stains people will look at them and be like their teeth don't look great but if you look at generally hunter-gatherers like the maasai if they don't smoke a lot they have big broad white smiles”