AIDS Virus Found to Survive in Dentist’s Tools : Health Equipment washed with disinfectant but not heat-sterilized poses a potential peril of disease transmission, study finds.

The viruses that cause AIDS and hepatitis B can survive within dental tools that are washed with disinfectant but not heat-sterilized, posing a potential risk of disease transmission, according to a new study.

The recent case of a Florida dentist who transmitted the virus to five patients ignited widespread fear about catching AIDS from dental procedures. But the infected patients in Florida got the virus from the dentist, not from contaminated equipment, according to investigations by the U.S. Centers for Disease Control.

Experts said the findings of the study published in the Nov. 21 issue of The Lancet are plausible, but the risk of catching AIDS from dental tools is probably very low. No such cases of have been reported.

However, finding pieces of AIDS virus in dental tools is “worrisome, mainly because the material was present in internal areas of the equipment that are not readily accessible to chemical germicides,” said Dr. David L. Lewis, the investigator and microbiologist in the department of Ecology at the University of Georgia.

“The new standard of dentistry should be that everything that goes into a patient’s mouth should either be disposed of or heat treated,” said Lewis.

Simply scrubbing tools with germicides is not good enough. These cleansers do not penetrate deep inside tools where blood and saliva contaminated with viruses can lodge, he said.

Responding to fears of AIDS transmission during dental procedures, the Food and Drug Administration sent a letter to American dentists on Sept. 28 advising that “reusable dental hand pieces and related instruments be heat sterilized between patients,” said Sharon Snider, an FDA spokeswoman.

Snider said the FDA’s guidelines are the same as those of the U.S. Centers for Disease Control and The American Dental Assn.

“The study is valid but for practical purposes I don’t think it’s any measurable risk at all,” said Dr. Thomas Schulz, an AIDS researcher at the Chester Beatty Laboratories at Institute of Cancer Research in London.

Investigators did two experiments, one with the AIDS virus and the other with hepatitis B virus.

The AIDS experiment included one healthy patient, one person with HIV suffering from AIDS symptoms, and one person with the virus but no symptoms.

After cleaning the volunteers’ teeth, investigators scrubbed and rinsed the tools with a disinfectant and turned the tools on inside a cup of toothpaste.

They detected pieces of the AIDS virus in the toothpaste from the tools used on the patient with full-blown AIDS. They did not detect the virus in the toothpaste from tools used on the other two patients.

Pieces of hepatitis virus were found in the toothpaste mixed with tools used on the hepatitis patient as well.