A Sydney dentist will only be able to practice under supervision, after almost 1,000 patients were potentially exposed to HIV and other viruses, including hepatitis B and C, while being treated at two dental clinics across the city.

An investigation was launched after patients complained to the dental board about Doctor Nuha Kamil, who runs clinics on Castlereagh Street in the CBD, as well as in North Sydney.

The investigation uncovered problems with infection control as well as the cleaning and sterilisation of dental instruments.

The South Eastern Sydney Local Health District sent letters to 980 people this month, warning them they may have been exposed to blood borne viruses like HIV, Hepatitis B and C while undergoing procedures over the past 10 years.

Doctor Vicky Sheppeard from New South Wales Health says there is a low risk of infection.

"This is really a precaution," she said.

"We're not aware that anyone has been exposed to that infection."

She says the dental board will decide what action should be taken against the dentist.