There are clear methods of how HIV can be transmitted. Transmission occurs through blood-to-blood contact. Sexual contact is the No. 1 method of HIV transmission, according to the CDC. This risk is greatly increased with trauma to the oral cavity. Persons with bleeding gums, ulcers, genital sores or STDs have an increased risk of transmission through oral contact. Following is transmission through needles, usually involving drug use, blood products (in third world countries without antibody detection), mother to child transmission and one documented case of dentist to his patients.