
I’m not a dentist, but since healthy human blood is not acidic (in fact, it’s slightly basic), it shouldn’t wear on the enamel. Additionally, since human blood has quite a small amount of sugar (only a few teaspoons throughout the entire body) and nearly no other carbohydrates, the bacteria in a vampire’s mouth would have a lot less to feed on, therefore building up plaque and producing acid at a MUCH slower rate.
So while a vampire would still probably want to brush and floss a bit, they’d actually have a LOT more lenience with oral hygiene than an ordinary person does. The only thing I’m unsure about is if a lack of chewing would negatively affect their jaw or gum health. Sure, vampires bite, but that isn’t really the same.