Vampire Dragons are members of the undead. They sustain themselves by drinking the blood of others. It is said that they are only “alive” at night, and seem dead or asleep during the day, as they cannot endure sunlight for long periods of time. Vampire Dragons can only reproduce by changing the eggs of other dragons, puncturing the shell with their fangs and injecting venom that kills the baby inside.

Dragons are highly-intelligent reptilian creatures that—from a human perspective, at least—appear to live forever. Many different varieties of dragon exist, each with their own unique qualities, habitats, and behavior. Adolescence in dragons is usually marked by the growth of a hatchling’s wings, although not all breeds of dragons grow wings and some breeds have other traits that indicate the beginning of maturation. In Galsreim, dragons and humans coexist peacefully.

The Vampire Handbook: Book 1, page 250.

"Regarding Fangs"

"Fangs on a vampire are like legs on a horse. One cannot be a true Vampire without them. Most Vampires have a single pair of Fangs on their upper jaw. These are mainly used for the purpose of biting, although there are many other uses. Fangs can be used for feeding, scaring, maiming, dismembering and occasionally smiling. For the sake of dignity smiling should be avoided as much as possible. Vampires are creatures of fierce, bloodthirsty rage, not cute smiling babies. No, we eat cute, smiling babies."

-About the author: Angel's Smile (Otherwise known as Devil's Grin) was named so because of the fact that he has twice as many sharp, perfectly symmetrical teeth than a regular Vampire.

This brings him up to a total of four, which actually makes for a surprisingly charming smile, considering the source.