Vampires may be able to take a bullet just fine, but unfortunately for many of them, gingivitis doesn't care if you're 40 years old or 800, and fangs don't brush themselves.
If a few years of lax flossing leaves you squirming in the dentist's chair, imagine what a few centuries of haphazard dental hygiene will do. Spring a cavity in one of those teeth, and a vampire may as well get a wooden stake to the gums.
It would take several hundred yards of dental floss per month ($30) plus a specially designed toothbrush for dogs ($50) just to adequately clean those enormous canine teeth. Of course, as everyone who knows anything about vampires knows, vampires' fangs detract when they're relaxed and going about their daily errands. You don't have to be a dentist to recognize the host of gum-infection risks this presents. Even the best dental plans wouldn't fully cover that sort of disaster, leaving a vampire out up to $5,000 every several years to get those evil ivories reconstructed.
In the end, basic -- albeit humiliating -- caps may be necessary. The self-proclaimed "Vampire's Dentist" will provide most variations of fangs at a reasonable cost, including the top-of-the-line "Interview with the Vampire" set for only $40, excluding shipping. Did we mention he's based in South Africa?