Dr. Wayne Scott Harrington, an Oklahoma dentist, maintained a frighteningly unsanitary practice that endangered roughly 7,000 patients to the harms of HIV and hepatitis.

The Oklahoma dental board is offering free disease testing for Harrington’s patients, after the practice was found to be putting them in danger by not properly sterilizing medical instruments, reported Fox News. The Tulsa Health Department first sent out a letter to the dental patients on Friday, alerting them to the sobering findings and urging them to get screened.

Harrington’s practice drew attention from the Oklahoma Board of Dentistry when a patient of his with no known risk factors tested positive for HIV and hepatitis C after receiving treatment from him, according to ABC News.

When they paid an unexpected visit to the dentist’s office, they found one set of instruments used for those with infectious diseases, and another set for people not believed to be carrying any such diseases. They also found that the autoclave, a dental instrument sterilizer, had not been checked for efficiency in six years – it’s supposed to be checked every month,

Drug cabinets, which contained medicine that expired two decades ago, were left unlocked. Harrington also had patients treated with morphine through 2012, but had not received an order of the drug since 2009. The dentist even allowed unlicensed and unauthorized employees to perform tasks they were unqualified to perform, according to CNN.

Accused of 17 violations, including endangering the public health, Harrington is likely to have his dentistry license formally revoked. He elected to surrender the license as well as his permits for anesthesia and medications on Mar. 20.

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