This one is always controversial - I have several vegan friends on Steemit who say the same thing - but we sell supplements and joke that half our customers are ex vegans with bad teeth! (except we are not actually joking)

http://www.naturefoods.co.nz/coconut-products/coconut-oil/zenian-coconut-oil-philippines

http://www.naturefoods.co.nz/nutra-organics-bone-broth-herb-garlic

The best explanation we have is that teeth heath is dependent on the animal products eaten by the parents, and by the child for their first 5-10 years.

But starting with a depleted nutrient store a vegan diet will destroy a person's teeth in 1- 15 years (longest time before problems starting we have heard of)

So any vegan without a history of eating some animal food is unlikely to maintain good teeth for more than a decade