Do they have bad teeth (in the stereotype anyway) because the meth (or process of using the meth or something meth related) does something bad to the teeth, or is it more they just spend so much time acquiring meth, using meth, and thinking about using and acquiring meth that they neglect their teeth.
i believe smoking meth eats the enamel on your teeth.
Nope, mostly because meth inhibits saliva.
IIRC it not only inhibits saliva (which helps keep the teeth clean) but it also makes what saliva is still there more acidic which isn’t good for your teeth. Couple that with the fact that most meth addicts (ones that are bad enough to get meth mouth) probably don’t have very good oral hygiene and probably don’t see the dentist when they start to notice a problem.
Your link seems to imply they are too stoned to brush their teeth and drink too much Coke.
Correct - methamphetamine use inhibits saliva and causes bruxism, a/k/a teeth grinding.