Lower budget films might turn to a number of companies which produce high-grade vampire fangs, either in the form of whole "dentures" or caps that are placed over an actor's canine teeth. These teeth differ from the kind of vampire teeth you find in Halloween stores because of their attention to detail. Otherwise, a film may instead call on its special effects crew to create custom fangs for their actors by sculpting them onto casts of their teeth and making a mold from that.
Because of the nature of close-up shots, makeup for movies has to look extremely realistic. This means that vampire fangs have to fit just right in the actor's mouth. This presents a problem, since there is a lot of variation in the shape of one person's gum line to another's. Manufacturers solve this one of two ways: Either they make fangs that, when heated, become pliable and take on the shape of the person's mouth, or they make custom fangs based on a mold of the actor's mouth.
If a movie production company is going to make its own custom fangs based on an actor's mouth, molds of that mouth must be made. The substance used for this is called alginate, and it is the same substance that dentists use to make molds of your teeth. It comes in the form of a white powder that, when mixed with water, begins to harden over a matter of minutes. It is one of the few molding compounds out there that is safe to put in your mouth.
Although you can get cheap fangs in any Halloween store, realistic-looking, Hollywood-grade vampire teeth can be quite expensive. Instead of paying a lot of money, you can create your own by making a mold of your teeth from alginate and making a resin cast. You can then modify the cast with polymer clay to make fangs and make another mold of that. Then simply swish liquid acrylic inside the second mold and allowing it to harden. Just be sure to use safe, nontoxic paints or makeup when you color it.
Acrylic is the material of choice for most movie fangs, particularly since it can be safely dyed. Latex, on the other hand, does not look quite as realistic as acrylic. It does not have the same texture and appearance as real teeth, but it can be used to good effect for flesh such as gums. In other words, it provides supporting detail for the full visage.