I have taught a number of Women's Assault Prevention courses with a guy who used to teach while he was living in Southern California. At that time, he went to the top Hematologist at UCLA Medical School because of a concern about biting as a defensive tactic leading to the contraction of AIDS. The response was that there was about a 1 in 10,000 chance of contracting AIDS if you bit the end of a person's nose clean off and spat it out, then rinsed at some point relatively quickly. There was a 100% chance, for all practical purposes, of contracting the AIDS Virus if you were successfully forcibly raped and ejaculated into. So, when the stakes are high, the risk is worth it was the lesson that he, I and most of our students take from that.
The jaw and teeth are incredibly strong natural weapons in extreme close quarters.
-RJP