With the 1.1 version, I'm really pretty happy with this.
If you want just fangs, neg prompt "vampire." I had some success with "fangs visible over lower lip."
Very often Occasionally there are double sets, assymetrical, or random fangs. This is mostly because the model seems to have been trained that fangs belong to animals: dogs, cats, etc. The shotgun approach is what I use; sometimes it's going to be hit and miss but 1.1 hits more than 1.0.
Both meet the bar I set for release: gives vampires fangs, but also gives people fangs without other vampire characteristics (skin, eyes, clothes). I also gave an example for giving fangs to a werewolf transformation. 1.1 even lets you draw fangs in Cyber Reality 4.2! I recommend a "photorealism" prompt even though it's a realistic output as it helps break the strong realism bent of the checkpoint. You can also use a photorealistic/art checkpoint, then use a realistic checkpoint in Refiner or Hires Fix.