Dr. Stephen Abel, 43, a New York City periodontist, has been named to the American Advisory Council on HIV/AIDS. Abel is the only dentist on the 30-member panel of health-care providers to advise the president on public-health policies and research issues concerning AIDS. Abel is the director of the Spellman Center at St. Clare`s Hospital in New York, one of the first facilities dedicated to providing dental care to HIV and AIDS patients. He will be working on a wide range of issues relating to the disease, in addition to oral-health issues. Since half of all AIDS patients eventually are covered by Medicaid, Dr. Abel says it is important for a dentist to be on the panel. "Someone has to be saying, `Don`t forget dentistry,` " he said. "If you ask persons with AIDS, what are the important issues, one of the usual responses is unmet dental needs."