Tens of thousands of Sydney dental patients face an anxious wait after discovering they could be at risk of infection with HIV and hepatitis.

Health authorities say 40,000 people have visited The Gentle Dentist, which has operated at Campsie since 2005 and Sussex Street in the city since 2008, and has been found to have had serious deficiencies in its cleaning and sterilisation practices that have put its patients at risk of infection.

However, of that group only the 11,251 who had an invasive procedure who should be tested for the infectious diseases, NSW Health told a press conference this morning.

On Wednesday Fairfax Media revealed that the owner of the clinics, dentist Samson Chan, has had his dental registration suspended over the breaches, along with four other dentists working at the practice. A further six have had conditions placed on their registration.

NSW Health's director of health protection, Jeremy McAnulty, said all patients who had procedures at the clinic, not just those patients of the suspended or disciplined doctors, should be tested if they had any invasive procedures that involved things such as instruments in their gums or complex surgery.

"We are hopeful that there will not have been any transmission but there is a risk to some people," he said. "[But] the risk is low and people should bear that in mind".

Patients at another two clinics, run by another unrelated dentist, Robert Starkenburg, have also been warned to see their GP.

Dr Starkenburg, who was known to be an HIV-friendly doctor, is thought to have seen about 800 patients in the period he was not complying with infection control rules. NSW Health said all those people could be at risk of infection because "due to inadequate patient records at Dr Starkenburg's surgeries, it is not possible to determine which patients had invasive procedures".

But Dr McAnulty said despite the work Dr Starkenburg did with HIV patients, who can have compromised immune systems and can be at risk not only of transmitting HIV but catching other conditions, there was no extra risk to patients at his clinic.

"Taking into account the type of patients and treatment for the practice we believe the risk to patients is low," he said. He said infection control procedures had a number of steps and all would need to be compromised for an infection to spread.

Dr Starkenburg on Wednesday told Fairfax Media that he was "very sorry" about what had happened, and his older age had made it difficult to keep up with changing rules around infection control, but he did not believe any of his patients would be infected.

At the press conference in the NSW Health headquarters in North Sydney this morning, Dr McAnulty also defended the delays in announcing the infection risks at both clinics, despite Dr Starkenburg being suspended in December and serious problems at The Gentle Dentist being discovered in February.

He said all 40,000 patient records needed to be assessed in that time, contacts made through Medicare and repeat assessments of the clinic done.

Shane Fryer, a member of the Dental Council of NSW that assessed the dental clinics, said the majority of dental practitioners did the right thing and the public should not be scared of infection at their dentist.

He said while The Gentle Dentist was continuing to operate at the moment, he was confident that the remaining practioners were practicing appropriate hygiene control - so much so that he would be willing to undergo a root canal surgery there.

The Dental Council has referred Dr Starkenburg and The Gentle Dentist practitioners who have had action taken against them to the Health Care Complaints Commission for further investigation.

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