TULSA, Okla. >> The crisp, stucco exterior of an Oklahoma dental clinic concealed what health inspectors say they found inside: rusty instruments used on patients with infectious diseases and a pattern of unsanitary practices that put thousands of people at risk for hepatitis and the virus that causes AIDS.

State and local health officials planned to mail notices today urging 7,000 patients of Dr. W. Scott Harrington to seek medical screenings for hepatitis B, hepatitis C and HIV. Inspectors allege workers at his two clinics used dirty equipment and risked cross-contamination to the point that the state Dentistry Board branded Harrington a "menace to the public health."

"The office looked clean," said Joyce Baylor, who had a tooth pulled at Harrington’s Tulsa office 1½ years ago. In an interview, Baylor, 69, said she’ll be tested next week to determine whether she contracted any infection.

"I’m sure he’s not suffering financially that he can’t afford instruments," Baylor said of Harrington.

Health officials opened their investigation after a patient with no known risk factors tested positive for both hepatitis C and HIV, the virus that causes AIDS. After determining the "index patient" had a dental procedure about the likely time of exposure, investigators visited Harrington’s office and found a number of unsafe practices, state epidemiologist Kristy Bradley said.

"I want to stress that this is not an outbreak. The investigation is still very much in its early stages," Bradley said.

Harrington voluntarily gave up his license, closed his offices in Tulsa and suburban Owasso, and is cooperating with investigators, said Kaitlin Snider, a spokeswoman for the Tulsa Health Department. He faces a hearing April 19, when his license could be permanently revoked.

"It’s uncertain how long those practices have been in place," Snider said. "He’s been practicing for 36 years."

The Centers for Disease Control and Prevention is consulting on the case, and agency spokeswoman Abbigail Tumpey said such situations involving dental clinics are rare. Last year a Colorado oral surgeon was accused of reusing needles and syringes, prompting letters to 8,000 patients, Tumpey said. It wasn’t clear whether anyone was actually infected.

"We’ve only had a handful of dental facilities where we’ve had notifications in the last decade," Tumpey said.

The Oklahoma Dentistry Board lodged a 17-count complaint against Harrington, saying he was a "menace to the public health by reasons of practicing dentistry in an unsafe or unsanitary manner." Among the claims was one detailing the use of rusty instruments in patients known to have infectious diseases.

"The CDC has determined that rusted instruments are porous and cannot be properly sterilized," the board said.

Health officials are sending letters to 7,000 known patients but cautioned that they don’t know who visited his clinics before 2007. The letters urge the patients to be tested for hepatitis B, hepatitis C and HIV — viruses typically spread through intravenous drug use or unprotected sex, not occupational settings.

Harrington could not be reached for comment Thursday. A message at his Tulsa office said it was closed, and the doctor’s answering service referred callers to the Tulsa Health Department. Phone numbers listed for Harrington were disconnected. A message left with Harrington’s malpractice attorney in Tulsa, Jim Secrest II, was not immediately returned.

Harrington’s Tulsa practice is in a tony part of town, on a row of some of the city’s most upscale medical practices. The white-and-green stucco, two-story dental clinic has the doctor’s name in letters on the facade.

According to the complaint, the clinic had varying cleaning procedures for its equipment, needles were re-inserted in drug vials after their initial use and the office had no written infection-protection procedure.

Harrington told officials he left questions about sterilization and drug procedures to his employees.

"They take care of that, I don’t," the dentistry board quoted him as saying.

The doctor also is accused of letting his assistants perform tasks only a licensed dentist should have done, including administering IV sedation. Also, the complaint says the doctor’s staff could not produce permits for the assistants when asked.

Susan Rogers, executive director of the state Dentistry Board, said that as an oral surgeon Harrington regularly did invasive procedures involving "pulling teeth, open wounds, open blood vessels." The board’s complaint also noted Harrington and his staff told investigators a "high population of known infectious disease carrier patients" received dental care from him.

Despite the high-risk clientele, a device used to sterilize instruments wasn’t being properly used and hadn’t been tested in six years, the board complaint said. Tests are required monthly.

Also, a drug vial found at a clinic this year had an expiration date of 1993 and one assistant’s drug log said morphine had been used in the clinic last year despite its not receiving any morphine shipments since 2009.

Officials said patients will be offered free medical testing at the Tulsa Health Department’s North Regional Health and Wellness Center.

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Associated Press reporter Jeannie Nuss in Little Rock, Ark., contributed to this report.