hi ! HIV infection also enters the body through tooth bite if the person has any mouth boils or throat ulcers etc. but in general the infection enters the body only when infected persons body fluids like blood, semen, vaginal discharges, saliva if he has mouth ulcers or throat ulcers, or through surigcal instruments or syringes, when these get in contact with the mucosal surface or open wounds of the unifected person.