These custom fit vampire fangs are fantastic!  The owner of Halloween Asylum swears by her pair.  The fangs come with a moldable material that will form to the shape of your tooth, allowing for a perfect fit - they will not fall out.  If you make a mistake with the fit, just warm up the material and remold, it's that simple.  You can even use a nail file along the top edge of the tooth to shape it to your gumline exactly.  Nothing looks more like real fangs!  If you want to take a break from character to grab a bite to eat (not of the human form), you can take the teeth right out and when you're ready, slide them back on.  No need for adhesive material.  Wear them over and over again.