The risk of AIDS infection among dentists and hygienists is low, even though many of them do not wear gloves or take other precautions against the AIDS virus, a study concluded. Researchers tested the blood of 1,309 dentists, hygienists and dental assistants and found that only one of them had been infected through apparent on-the-job exposure to their patients. That case, a New York City dentist, was widely publicized last June when it was reported at an AIDS meeting in Washington. Researchers who conducted the survey reported details of their findings in today's New England Journal of Medicine. The study was conducted by Dr. Robert S. Klein and colleagues at Montefiore Medical Center in New York.