ATLANTA, JULY 26 -- In the first case of its kind, federal researchers reported today that a woman apparently got AIDS from her dentist during a tooth pulling, even though he was wearing gloves and a mask.

The case has prompted the government to review its guidelines for AIDS prevention during medical procedures even though "the possibility of another source of infection cannot be entirely excluded," the federal Centers for Disease Control said.

It said all evidence was "consistent with" the patient being infected during her trip to the dentist.

Public health experts said the incident does not change their belief that AIDS cannot be transmitted by casual contact. Nor does it indicate that any new mode of transmission has been discovered.

They said it had always been assumed that there was a slim chance for some freak accident to cause blood from the doctor or dentist to get into a patient's body.

The dentist, who had been diagnosed with AIDS three months earlier, was wearing gloves and a mask, as recommended, while extracting two molars for the patient.

"We don't know exactly what happened during that procedure," said Harold Jaffe, deputy director for science in the CDC's HIV-AIDS program. "We have to assume there was some kind of an accident that exposed the patient to the dentist's blood."

But the patient didn't remember the dentist having any cuts, and the dentist didn't recall any accidents, such as sticking himself with the anesthetic needle, the CDC said.

The CDC said the woman was not a user of intravenous drugs and had only two boyfriends before her diagnosis, both of whom tested negative for the virus. Also, tests showed the viruses in the woman and the dentist were much more alike in genetic sequence than is typical for AIDS viruses from unlinked persons.

Still, officials of the American Dental Association said the CDC may have jumped to conclusions.

"We think it is not a totally conclusive case of transmission," said Enid Neidle, director of scientific affairs for the Chicago-based association. "We are not happy at any report that could raise fears on the part of the public that the dental office is a place of danger and infection."

CDC officials stressed that there is no reason to believe the virus was transmitted just because a dentist with AIDS came close to a patient.

"We are not suggesting some unique, previously undescribed kind of transmission," Jaffe said. "And we're certainly not suggesting to people they should be afraid to go to their doctors and dentists."