A former employee of the Oklahoma dentist accused of exposing thousands of patients to HIV, hepatitis B and hepatitis C told ABCNews.com that he sent her to Dallas for an anesthesia training program to learn more about intravenous anesthesia.
What he didn't tell her was that putting those skills to use in Oklahoma was illegal.
"My understanding is that after we were properly trained, we could start an IV," said Harrington's former dental assistant, who worked for Harrington in the 1990s and asked to remain anonymous to protect her identity. "A little jug of the sedative drug sits on the side of the chair and he'd be like 'give one,' 'give two,' and you just are giving one cc, two cc's. It's always dictated by him what to give them."
On Friday, the Tulsa Health Department sent 7,000 warning letters to the patients of Dr. Wayne Scott Harrington, an oral surgeon with practices in Tulsa and Owasso, informing them of an investigation into Harrington's practice and advising them to get tested for HIV, hepatitis B and hepatitis C.
The dentist's alleged practices came to light after a patient tested positive for HIV and hepatitis C, and had no known risk factors. State health officials traced the infections to the dentist.
Investigations by the state dental board, the state health department, the state bureau of narcotics and the federal Drug Enforcement Agency are just getting underway, and Harrington could face criminal charges, Susan Rogers, president of Oklahoma Board of Dentistry, told ABCNews.com.
The thing that "stunned" Rogers most during the investigation was that Harrington's dental assistants were administering anesthesia, which is illegal in Oklahoma, she said.
According to the Oklahoma Dental Act, only the dentist can administer intravenous anesthesia. A certified registered nurse can administer it, too, but only under the supervision of a dentist.
"No one else in a dental office is even allowed to use a needle on the exterior of a patient in a dental office except the dentist," Rogers said. "Dental assistants can't do anything with needles at all."
Harrington's former employee called ABCNews.com to defend her old boss because she thought being sent to Dallas for the two-day American Association of Oral and Maxillofacial Surgeons course on anesthesia assistance in 1995 was a sign Harrington invested in his employees' education.
Indeed, the course was -- and still is -- the highest level of education the association offered, said its associate executive director of practice management and governmental affairs, Karin Wittich. In some states, taking the course is enough to be legally allowed to assist with anesthesia, but they expect attendees to abide by state laws, she said.
Rogers said dental assistants can't set up IVs or push sedation drugs into patients in Oklahoma. Since anesthesia is only supposed to be administered by a dentist, the assistants were technically practicing dentistry without a license, which was a misdemeanor in 1995, but has been a felony since 2005.
"Why would you let an assistant with no training other than a weekend class do anesthesia when it's required for you to be a doctor to do that procedure?" Rogers asked.
Oklahoma has between one and four fatalities a year "directly related" to anesthesia procedures in dental offices, Rogers said.
"For that lady to call and say she did that, I'm sorry our statute of limitations doesn't go back further," she said.
But Harrington's former employee said she had no idea it was illegal. She said she didn't think Harrington knew either.
"I'm still praying that all this comes back positive for him," she said. "He was a great guy to work for, so I'm floored and very defensive about all this stuff they're coming up with. Either things have really changed in that office or they're digging really deep for dirt."
The former employee said she "bawled" on the day she left Harrington's practice for a job closer to home. Despite the allegations against Harrington, she said she would bring her children to see him today if they needed oral surgery.
She said she suspected that even though it's illegal for dental assistants in Oklahoma to help with anesthesia, dentists other than Harrington probably allow them to administer it, too. She said she doesn't know a single oral surgeon who has a registered nurse on staff, and that surgeons likely often ask their assistants to handle anesthesia when they're in the middle of surgery and have bloody gloves.
"It's common sense to have someone with available hands as opposed to you breaking surgery, getting the vial, getting anesthesia, then going back," she said. "He would never, never harm anybody."
Harrington's lawyer did not respond to repeated requests for comment.