The state health department said 90 patients have tested positive for hepatitis C, six for hepatitis B, and four for HIV, according to a press release.

More than 4,200 people have been tested since the dental board launched in investigation in March. Health officials have notified 7,000 of Dr. Harrington's patients that they may have been exposed to blood-borne viruses at his Tulsa and Owasso offices and should be tested for hepatitis B, hepatitis C, and HIV.

The Oklahoma Board of Dentistry launched the investigation after being notified that health officials were looking into complaints about potential hepatitis C contamination at Dr. Harrington's practice. Investigators found numerous violations of health and safety laws, including the use of rusty instruments on patients known to have infectious diseases.

Two new lawsuits were filed against Dr. Harrington in November, according to a newson6.com story. The most recent case was filed on behalf of a man who had 14 teeth extracted last December.

A class-action lawsuit was filed in September by seven former patients, including five who claim they contracted infectious diseases during treatment at Dr. Harrington's dental clinics.

Dr. Harrington is scheduled to appear before the dental board on January 17, 2014, in Oklahoma City.

Patients sue Okla. oral surgeon over pathogen exposure
A class-action lawsuit has been filed against an Oklahoma oral surgeon accused of exposing thousands of patients to hepatitis and HIV because of contaminated...