I am currently reading 'Hannibal' and at one point the Sardinian character Carlo is desctribed as chewing on the gristle of a stag's tooth. To me, this makes it seem likely that it is an actual tooth or at least some sort of animal product, although I am not sure what it really is. Perhaps Sardinians do really chew on stag's teeth in the way that British and American arable farmers were often depicted chewing on a piece of straw. I would certainly like to find out more about this and may try to email Thomas Harris to see if I can get the answer straight from the horse's, or should that be stag's, mouth.