(CNN) -- About 7,000 patients who visited a suburban Tulsa, Oklahoma, dentist in the past six years may have been exposed to HIV and hepatitis, health investigators say.
Investigators were left grasping for words to describe what they found inside W. Scott Harrington's dental practice: Assistants did techniques that only a dentist should, and sterilization procedures and needles were handled improperly.
"I will tell you that when ... we left, we were just physically kind of sick," said Susan Rogers, executive director of the Oklahoma Board of Dentistry. "I mean, that's how bad (it was), and I've seen a lot of bad stuff over the years."
The state health department will offer free HIV and hepatitis testing to the thousands of patients who sat in Harrington's chairs.
Joyce Baylor, who said she was Harrington's patient in the past, said she heard about the health risk from a news report.
Baylor said she has not yet received a letter from health officials but she was going to see her doctor next week.
"The (dental) office was clean," Baylor said. "I had no idea that things weren't what they should have been."
Harrington also allowed "unauthorized, unlicensed" employees to perform intravenous sedation of patients, Rogers said.
"That is completely unacceptable and illegal in Oklahoma," she said.
Investigators do not know if that practice led to infections in any patients of Harrington, who surrendered his dental license on March 20, two days after health officials visited his office as part of their investigation. He also surrendered permits for anesthesia and medications.
Harrington's office was a "perfect storm" for infections, Rogers said.
The state health department is contacting about 7,000 patients seen by Harrington since 2007 to urge them to be tested for hepatitis B, hepatitis C and HIV.
Harrington, 64, is a veteran oral surgeon who started practicing more than 35 years ago. He worked in the Tulsa suburb of Owasso.
An official complaint filed before the state dental board described the violations, including "multiple sterilization issues, multiple cross-contamination issues, (and) the drug cabinet was unlocked and unattended."
There were no logs of inventory for the drug cabinet, the complaint states. One drug found in the cabinet had expired in 1993. Other records showed that morphine had been used in patients throughout 2012, even though the dentist had not received a morphine delivery since 2009.
Also, Harrington's dental assistants did not have permits, the complaint says.
The investigation began after the health department alerted the dentistry board to a potential hepatitis C infection from Harrington's office.
Rogers told the Tulsa World newspaper that dentists' offices in Oklahoma are only inspected after a complaint is filed. The board lacks the personnel to monitor the more than 10,000 licensed dentists in the state, she said.
The outward cleanliness of the dentist's office belied the mess that was behind the cabinets, Rogers said.
"Some of the things we found were just absolutely incredible," she said. "It's just basic universal precautions for blood-borne pathogens that they were just not following regular protocols" for.
Individual states are in charge of licensing, inspection and regulation of dentists, said Dr. Matt Messina, consumer adviser and spokesman for the American Dental Association. He said he practices in Ohio, where random inspections are done every other year.
"This is exceedingly rare. ... I'm just angry, because this is a case I think is so far outside of the bounds of normal that it makes it remarkable," he said.
At the dentist: 5 safety tips
The Centers for Disease Control and Prevention provides national guidelines for dental offices to help prevent the spread of infections. They include cleaning and sterilizing all non-disposable items such as dental tools between patients; disinfecting surfaces; and requiring staff members to wear protective wear like masks, gloves and eye protection.
Patients should look for gloves being changed after every patient and sterilized instruments -- sometimes in sterilized bags or wrappings opened after the patient is seated, Messina said. Patients should feel free to ask questions about sterilization procedures.
Since 1991, only three cases of dental infection in patients have been documented -- two with hepatitis B and one with HIV, the CDC said. No cases of hepatitis C have been reported.
Rogers said Harrington told investigators that he had a higher population of HIV and hepatitis patients. That compounded the infection risks, Rogers said.
He would accept Medicaid for oral surgery, which often meant treating lower-income people who popped up at emergency rooms and were transferred to him to do extractions and other procedures, she said.
Many of these procedures were invasive and exposed patients' blood, tissue and bones, and investigators discovered that these procedures were being carried out in an unsanitary environment.
"The instruments that came out of the autoclave were horrible," Rogers said, referring to a device used to sterilize tools. "I wouldn't let my nephews play with them out in the dirt. I mean, they were horrible. They had rust on them."
Furthermore, at Harrington's office, the autoclave was not being used properly, the complaint states. There should be a monthly test to ensure the autoclave is properly sterilizing the equipment, but no test had been done in at least six years, the complaint says.
According to the document, when the dentist was asked about the sterilization and drug procedures in his office, he replied: My staff "takes care of that, I don't."
In all, Harrington is accused of 17 violations, including negligence and "being a menace to the public health." He faces possible punishment including the revocation of his license.
Infection in a setting such as a dentist's office is rare, the health department said, but the patients should be tested as a precaution.
"Hepatitis B, hepatitis C and HIV are serious medical conditions, and infected patients may not have outward symptoms of the disease for many years," the department said.
CNN's Joe Sutton, Ashley Hayes, Jacque Wilson and Trisha Henry contributed to this report.