Dental-Drill/Aids Link Claimed -- Researcher Says Failure To Sterilize Instrument Can Easily Spread Virus

STUART, Fla. - A soon-to-be-published study shows a dentist's drill can easily spread germs from patient to patient and could explain how at least five people were infected with the AIDS virus in a Jensen Beach, Fla., dentist's office.

David Lewis, University of Georgia research associate, said the internal parts of the multipurpose dental handpiece - usually used as a polisher and drill - can be coated with blood, saliva and tiny tooth fragments.

Most dentists neglect to sterilize the often-used handpiece properly, said Lewis, a microbiologist who has studied the instrument for 15 years.

Lewis' article is to appear by September in the "ASM News," published by the American Society for Microbiology based in Washington, D.C.

"We consider the dental handpiece as a piece of equipment that could have been contaminated with blood," said Dr. Harold Jaffe of the national Centers for Disease Control in Atlanta.

But he emphasized that method of transmission "is only a theoretical possibility."

The CDC determined with genetic tests that dentist David Acer of Jensen Beach probably contaminated equipment while treating himself and then infected the five patients.

"They're going to find out in the end that it's the handpiece," Lewis said. "The Acer case does not come as a surprise to the industry."

Dr. Joseph Chasteen, associate dean for clinical affairs of the University of Washington School of Dentistry, also said it is quite

logical to raise a question about the handpiece. "It does sound both possible and plausible" that the virus could have spread through the instrument, said Chasteen, who is responsible for infection control in the dental school.

The handpiece is the "single most common source for contamination," said Todd Meyers, with the marketing department of Midwest Dental in Des Plaines, Ill., one of the nation's largest manufacturers of handpieces.

"We have a primary concern," Meyers said. "We started manufacturing fully autoclavable handpieces in 1981. In '84, '85 and '86, we had the introduction of the AIDS scare, which accelerated the need of autoclaving between patients."

Autoclaving is the most effective method in killing disease-causing microorganisms that can live in bodily fluids, Lewis and other experts agree.

An autoclave is a sterilization device for dental equipment that acts like a pressure cooker, Lewis said. Autoclaving takes about 45 minutes, and its frequent use significantly deteriorates handpieces, which can cost up to $700 each.

Chasteen said that until the past five years or so, many dentists were slow to purchase the new handpieces that can be sterilized in autoclaves because some didn't believe the instruments could withstand the autoclave. They are more accepted now, he said.

In a survey, Lewis found less than 1 percent of dentists properly sterilize the handpiece between patients. A similar nationwide study by the University of Texas showed less than 15 percent of dentists autoclave.

Lewis, 43, has worked at the university for five years since earning his doctorate there. He also works as a microbiologist for the U.S. Environmental Protection Agency and is widely published in professional journals.

While the handpiece is being used, it is cooled by water propelled through it. Lewis said that blood, saliva and tooth fragments sometimes are imbedded in the cavities and grooves of the handpiece and develop into something known as biofilm.

Lewis, whose specialty is biofilms, said layers of bodily fluids build in these areas. On the surface, the microorganisms appear dead. That surface insulates live microorganisms underneath.

The CDC-recommended infection control calls for wiping the handpieces with a cloth soaked in a germicide and flushing water through it. Handpieces cannot be immersed in a germicide because it corrodes the internal mechanisms.

Lewis says the disinfectant is insufficient.

"That's only killing the microorganisms on the outer layers," Lewis said. "It will look quite dead. . . . But live ones are hiding in the middle layers."

As the handpiece is used on the next patient, the dead layers can "break loose and set live organisms free," Lewis said.

In one experiment, Lewis and dentist Robert Boe sought to learn how much contamination could occur under such a circumstance.

Boe drilled on teeth contaminated with a purple bacteria. Even after flushing water through the handpiece for 30 seconds, Lewis found in 10 seconds of operation that the handpiece was expelling bacteria equal to five pricks by a needle.

Lewis didn't wipe off the handpiece, as suggested by the CDC, to examine the full potential of passing microorganism. Some dentists rarely use the germicides between patients, Lewis said, opting to clean handpieces thoroughly at the end of the day.

HIV, or the human immunodeficiency virus, is the suspected cause of acquired immune deficiency syndrome. HIV is normally transmitted through sexual intercourse, sharing needles between intravenous drug users, from a mother to her unborn child and rarely through blood transfusions.

When Kimberly Bergalis of Fort Pierce, Fla., appeared with no identifiable risk factor, CDC investigators were forced to look at Acer, her dentist. Bergalis, 23, was the first to say Acer infected her with HIV. Four other patients later surfaced because of Bergalis' public stand.

Still, the Acer case is the only documented spread of the virus from any health-care practitioner to a patient. This is in the context of a 10-year epidemic, more than 180,000 reported AIDS cases and an estimated 1 million other Americans infected with the virus.

The American Dental Association recommends autoclaving, or heat sterilizing, of dental equipment between patients. But the association says when autoclaving is impossible, disinfectant should be used.

A spokesman for the association, , Phil Weintraub, disagrees with Lewis' view of the risk of dental procedures.

"Since 1987, not one case of hepatitis B transmission has occurred in a dentist office," Weintraub said. "The Acer case in Florida is an anomaly."

However, Chasteen, of the UW dental school, said he "absolutely believes" that dental instruments should be heat sterilized - through autoclaves or other accepted means - whenever possible.

It is also a legitimate question, he said, for patients to ask their dentists and dental hygienists if they use such sterilization.

-- Times staff and The Associated Press contributed to this report.