Some 8,000 former patients of Colorado-based dentist Stephen Stein were told by the Colorado Department of Public Health and Environment to seek testing for HIV and hepatitis after learning that the suspended dentist had a nasty habit of reusing needles and syringes.

It was unclear how many patients had been exposed to recycled medical equipment as Stein's records were incomplete.

Health officials took no chances and warned all former patients [pdf] that having received an injection of any sort at Stein's two Denver-area clinics between 1999 and 2011 might have put them at risk of contracting HIV, hepatitis B, or hepatitis C.

Stein's had his license suspended last year, but the reason for the suspension remains confidential while an investigation is ongoing. According to a U.S. Attorney's Office spokeswoman, a criminal probe into allegations of prescription fraud preceded the recently emerged concerns over reused syringes.

[screengrab via CBS Denver]