TULSA, Okla. — Hundreds of patients of an Oklahoma oral surgeon accused of unsanitary practices showed up at a health clinic Saturday, looking to find out whether they were exposed to hepatitis or the virus that causes AIDS.

Letters began going out Friday to 7,000 patients who had seen Dr. Scott Harrington during the past six years, warning them that poor hygiene at his clinics created a public health hazard. The one-page letter said how and where to seek treatment but couldn’t explain why Harrington’s allegedly unsafe practices went on for so long.

Testing for hepatitis B, hepatitis C and the virus that causes AIDS began at 10 a.m. Saturday, but many arrived early and stood through torrential downpours. The Tulsa Health Department said 420 people were tested Saturday at its North Regional Health and Wellness Center. Screenings resume Monday morning.

Kari Childress, 38, showed up at 8:30 a.m., mainly because she was nervous.

“I just hope I don’t have anything,” said Childress, who had a tooth extracted at one of Harrington’s two clinics five months ago. “You trust and believe in doctors to follow the rules, and that’s the scariest part.”

Inspectors found a number of problems at the doctor’s clinics in Tulsa and suburban Owasso, according to the state Dentistry Board, which filed a 17-count complaint against Harrington pending an April 19 license revocation hearing. According to the complaint, needles were reinserted into drug vials after being used on patients, expired drugs were found in a medicine cabinet and dental assistants, not the doctor, administered sedatives to patients.

One patient, Orville Marshall, said he didn’t meet Harrington until after he had two wisdom teeth pulled about five years ago at the Owasso clinic. A nurse inserted the IV for his anesthesia; Harrington was there when Marshall came to.

“It’s just really scary. It makes you doubt the whole system, especially with how good his place looked,” said Marshall, 37.

An instrument set reserved for use on patients with infectious diseases was rusty, preventing its effective sterilization, and the office autoclave — a pressurized cleaner — was used improperly and hadn’t been certified as effective in at least six years, according to the complaint.

Dr. Matt Messina, a Cleveland dentist and a consumer adviser for the American Dental Association, said creating a safe and hygienic environment is “one of the fundamental requirements” before any dental procedure can be performed.

“It’s not hard. It just takes effort,” he said.

Weekly autoclave testing can be performed for less than $400 annually, according to the website of the Autoclave Testing Services of Pearl River, New York.

Autoclaves typically can be purchased for $1,000 to $8,000, depending on their size and features. And an average dental practice can expect to pay more than $40,000 a year in equipment, tools and supplies alone, according to several dental organizations.

No one answered the door Thursday at Harrington’s Oklahoma home, which property records show is worth more than $1 million. His practice a few miles away, in a tony section of Tulsa where plastic surgeons operate and locals congregate at bistros and stores such as Saks Fifth Avenue, has a fair-market value of around $851,000.

Property and tax records show Harrington owns another residence in Carefree, Ariz., in an area of upscale homes tucked into in the boulder-strewn mountains north of Phoenix.

Nobody was at home Saturday at the low-slung, 1950s-style vacation home, across from the Boulders Resort. A message at Harrington’s Tulsa office said it was closed and an answering service referred callers to the Tulsa Health Department.

Suzy Horton, an old friend of Harrington’s, said she can’t believe the allegations about the man who removed two of her teeth in the early ’90s. Horton’s ex-husband sold Harrington his home in Carefree — a home where she once lived.

“I’ve been to dentists my whole life, so I know what a professional office looks like,” Horton, who now lives in Phoenix, said. “His was just as professional as anybody.”

Horton hasn’t seen Harrington in years, but she said he has sent her a Christmas card and wreath every year since her 1999 divorce.

“It was a long time ago, so I suppose anything can change, but the kind of person they’re portraying in the news is not the kind of person who sends you a Christmas” card, she said.