Since 1991, only three cases of dental infection in patients have been documented -- two with hepatitis B and one with HIV, according to the CDC. No cases of hepatitis C have been reported.
"This is exceedingly rare," said Dr. Matt Messina, a consumer adviser and spokesman for the American Dental Association, of the allegations levied against Harrington. "I'm just angry, because this is a case, I think, so far outside of the bounds of normal that it makes it remarkable."
The infection risks are compounded given that Harrington told investigators he had a higher-than-normal population proportionally of HIV and hepatitis patients, Rogers said.
HIV is a condition that over time destroys a body's immune system, thus its ability to fight infections. If not treated, nearly all those infected with HIV will develop AIDS, according to the National Institutes of Health. Hepatitis -- the most common types being hepatitis A, B and C -- refers to inflammation or viral infections of one's liver. Some 4.4 million Americans have chronic hepatitis, though most of them don't know it, the CDC says.