l wanna get fake vampire teeth put over my real teeth by a dentist but l do not know how to ask

just tell him what you put here if your dentist can not do it they can point you in the right direction

So u want them done permanently? If that is the case, do not hesitate to ask ur dentist. He or she will probably tell u how to go about it.

If u want them only temporarily, there r party supply stores or costume stores that have some that r of pretty good quality for a descent price. Now that Halloween is coming there should be lots. Here is an example:

http://partycity.com/cgi-bin/parties/accessories.cgi?parties=Halloween&productstype=Make%20Up&products=176261&&zoom=1

If u r talking about semi-permanent vampire teeth tell ur dentist u want Vampire Fang Dental Caps. If later in life u decide u do not want them any more they can be removed. Talk with ur dentist & discuss ur options.

If ur talking about novelty fangs that will stay in ur mouth for a day u should get Scarecrow Vampire Fangs. Make sure u follow the instructions.
http://vampfangs.com/Scarecrow_Fangs_s/32.htm

If u r going to get the semi-permanent teeth l would still get the Scarecrow Vampire Fangs. They have different sizes & u can see which ones will be more comfortable for everyday wear, before u get the caps.