It looks like he's getting his teeth capped in that photo. They basically file down the outer part of the teeth and replace it with this cap. It's not dentures and they don't come out. Notice he's not missing teeth in the photo and they're not blackened from rot.

Also, you're reading something written by a liberal arts degree (probably journalism or another writing degree). That's a journalism degree interpreting dentistry extrapolating drug mechanisms from self reported meth users.

There are reasons why street meth is bad, but I don't think the tooth decay is proven. It does appear that Hunter's pipe had meth in it, too.