Why not just change the genetics off the coral so that the immune system accepts it?
LOL are you guys serious with this coral idea? Do you actually mean
coral or some coral-like creature? Corals don't grow in mouths.
Then, supposing you mean a generic 'creature', what if growing on your teeth will not be enough for it and it decides to take over your whole body, like, say, sacculina takes over a crab?

A semblance of a lymphatic system on this crab is parasite's tendrils that permeate its whole body. Sacculina controls crab's behavior and reproduction (it castrates the crab and enslaves it to tend for its own young). The crab's immune sys ignores the parasite, but is otherwise functional.
How's that for a side effect?
PS that would make a fun sci-fi story lol
Edited by xEva, 03 January 2013 - 10:48 AM.