It's impossible to deny the link between tooth decay, sugars and acidic diets and bacteria growth. On a sidenote, kissing your child when you have caries might also not be such a good idea. [1]
[0] http://www.nidcr.nih.gov/DataStatistics/FindDataByTopic/Dent...
[1] http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1678...
Source: wife is a dentist.
source: not a dentist, but have had a bunch of dental work done...
I have couple of friends that had to get implants and they kept quite a good dental hygiene.
Bleaching, diet, life style and genetics potentially play a more critical role than age.
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.