I don't think that blood suckers ever have to worry about blood sugar levels. It's pretty much a protein/pre-digested diet so-to-speak. There are stories of weakened vamps, due to not getting their, erm, diet on time. As for a dentist, that would assume decay. Only in the case of a vamp, if they are dead and not decaying, maybe that is why their teeth don't decay. I mean they are dead. So they should decay anyway, but they don't.

Look, if I meet a vamp, I'll be sure and ask after his dentist, assuming my crucifix holds. I'll let him know you're curious and send him your way. No, no need to thank me. Be happy to send him along.