DALLAS -- Officials at the nation's third-largest state prison system, citing a policy that prohibits discrimination in providing health care, have fired a staff dentist who refused to treat inmates with AIDS.

The Texas Department of Corrections dismissed Dr. David T. Spence, a dentist at the Coffield prison unit near Palestine in northeast Texas, after he told authorities he wanted the option to refuse "treatment for anyone suspected of, or diagnosed with AIDS, at any time, now or in the future."

"Your stated threat of termination of employment pales when compared with the reality of AIDS," Spence wrote in the memo that resulted in his firing earlier this month.

The case highlights the fear many dentists have of contracting the universally fatal illness -- a fear based on their frequent contact with blood. According to the federal Centers for Disease Control, 12 health care workers have contracted the virus on the job since 1981, and only one was a dentist.

The concern, nonetheless, has led many private dentists to begin wearing rubber gloves, sending demand for the gloves to record levels. Others, with the endorsement of their professional organization, have referred AIDS patients to special clinics.

State-hired prison dentists, however, are required to treat all patients.

While others among the 44 staff dentists in the prison system, smaller in population only than California's and New York's, have expressed concern over treating inmates infected with the human immunodeficiency virus (HIV), Spence's open defiance violated a department policy that forbids medical staff to discriminate in providing care.

"I don't think we had much choice," said corrections department spokesman David Nunnelee. "He just flat-out said he wasn't going to do it."

The American Dental Association guidelines advise dentists to wear protective gloves, goggles and masks while treating every patient, said spokeman Richard Asa. The guidelines say dentists may turn down any new patient they suspect has AIDS, and may make "informed, sensitive referrals if it is in the best interest of the patient's health." All patients must be treated in emergencies, the guidelines say. While some dentists refer patients to special AIDS treatment centers, others continue providing care discreetly to keep other patients from being frightened away.

The fears are heightened among those who work closely with prison populations, which have a high incidence of homosexuality and intravenous drug use -- two activities conducive to spreading the AIDS virus, prison officials said.

To reduce the risk of infection for prison dentists, Texas corrections officials have instructed their staff at each of the 27 prisons to follow precautions set out by ADA: sterilizing instruments with heat, and use of protective apparel when treating all patients.

Texas prisons provide voluntary testing of inmates for AIDS infection, Nunnalee said. The latest figures show that in a population of 39,000 inmates, 1,050 have been tested, with 166 turning up postive for the presence of AIDS antibodies.

Prisoners with AIDS, AIDS-related complex (ARC) or who tested positive without symptoms must be allowed to remain in the general population unless they are "engaged in homosexual or needle activity," a determination each prison commander must make, Nunnelee said. In those cases, inmates are assigned to single-occupancy cells, he said. Currently, eight such prisoners have been isolated.