You're getting downvoted but that's exactly what happened to my mother. In the 1950s doctors prescribed methamphetamine to overweight children. It was considered a miracle cure. Worked great! But her first root canal was at 19 and it went downhill quickly from there.
This isn't the US none of them are using meth, my GF's father lost most of the teeth by 45, my GF for 6 years now is using what I call "Industrial Strength" toothpaste (3000 PPM fluoride) which was prescribed by the dentist because she were getting lesions left and right on her teeth which could lead to cavities, she was also ordered to stop using mouthwash because it apparently kills the "wrong" bacteria and to stay away from gum and soda.
Can Meth fuck up your teeth? sure, so can working in a sulfur mine it doesn't mean that everyone who has dental issues is a meth head.
There is plenty for room for genetics and lifestyle to affect your teeth without having to go into social extremes. And while some what anecdotal but on the other hand I open beer bottles with my teeth, I used to smoke for almost 10 years, didn't use to really brush that regularly especially between say the ages of 10 to 18 and I didn't had a single cavity yet.
And in one occasion when I had to get some dental work on a wisdom tooth that needed to be ground down a bit to not hit my upper gum the dentist said I was lucky and that my teeth were like 2000 year old cement and that he had to increase the water flow to keep the tooth and the drill head cool.
Different people have different teeth there is variation in tooth composition and density between people just like with bones and many other body parts. Add to that different bacterial ecosystems, different immunoresponse, different saliva production (amount, mineral count, acidity etc.) and you get a large spectrum of outcomes for your teeth even without you doing meth or getting constant preventative dental treatment.
