Thousands of people in Colorado may have been infected with HIV or hepatitis after a local dentist was discovered to have been reusing dirty sedation syringes and needles to some of his 8,000 patients for 12 years.

Colorado state health officials are warning patients of Dr. Stephen Stein to get tested immediately after an investigation revealed that the dentist used the same syringes and needles for multiple patients to administer intravenous medications, including sedation medication between September 1999 and June 2011.

"Needles and syringes were used repeatedly, often days at a time," a fact sheet on the state's public health website explains.

"Because there can be a small amount of blood that remains in syringes and needles after an injection through an IV line, there is a risk of spread of blood borne viruses, such as HIV, hepatitis B, and hepatitis C, between patients," according to the fact sheet.

Stein had been working out of Stein Oral and Facial Surgery at South Quebec Street, Highlands Ranch for more than 20 years, and between August 2010 and June 2011, he also practiced at another surgery known as New Image Dental Implant Center, located at East 1st Avenue, Denver.

Authorities say that another surgeon Dr. Jeremy Miner, has taken over the Highlands Ranch office.

The state is contacting at least 8,000 patients, identified through dental records, to advise them to get tested for HIV, Hepatitis B and Hepatitis C. Officials are also appealing to the public and asking those who know at-risk patients to reach those the state has no addresses for.

Patients who were given local, oral anesthetic shots are not believed to be at risk of any of these potentially deadly viruses, and no infections have yet been reported.

Hollynd Hoskins, a Denver attorney who represented victims who had been infected with Hepatitis C at Rose Medical Center in 2009, said that Stein's alleged practice of reusing syringes and needles on his patients was "mind-blowing and indicates an utter disregard of the known consequences of spreading life-threatening diseases," according to the Denver Post.

Colorado public health director Dr. Chris Urbina told the paper that because the latest case is "very unusual" officials are taking it even more seriously.

The state recommended that patients who don't know whether they received IV medication should also get tested as well as people who were treated by Stein before 1999 because the state doesn't known whether syringes were being reused back then.

Only patients who are sure they did not get any IV do not need to go get checked.

The Dental Examiners' Board had forced Stein to stop practicing on June 24, 2011, but the ruling was unrelated to the current allegations.

The Colorado Department of Regulatory Agencies overseeing medical licenses in the state did not disclose the nature of the complaint that prompted its investigation which brought Stein's reuse of dirty syringes to light.

"When public safety became an issue, we immediately jumped on it,: spokesman Maulid Miskell told the Colorado newspaper.