I haven't been to the dentist coming up on two years now, and I haven't had any problems. In the past couple months or so I've noticed that I can't really eat any frozen foods, since it makes my teeth hurt, although I've had sensitive teeth since I was young. I used to eat so many Warheads that it made my teeth hurt, and I kind of have a feeling I've damaged my enamel due to that. I used to take calcium supplements (generic Oscal, ground up oyster shells), which I stopped about a month and a half ago. I'm thinking about starting to take it again, thinking that it might take care of the sensitive teeth thing.
I'm no dentist, but I would think that low-carb aspects of paleo lend itself to teeth-protecting diet, being that there are not a lot of starches/sugars present for bacteria to break down into lactic acid. I just started using Tom's fluoride-free propylis and myrrh toothpaste, mainly because I saw it on sale. It works pretty good, has a good taste, and it leaves my teeth feeling clean.
I'm a little undecided about going to the dentist, since it's not covered in my health insurance, so I'm thinking that I would only go if one of my teeth start showing trouble, either visibly or if I feel pain.