Dr Robert Starkenburg, who had practices in Surry Hills and Bondi Junction, as well as The Gentle Dentist operator Dr Samson Chan and four of his staff, have been suspended for poor hygiene controls, it was announced on Thursday.
Up to 12,000 people are at risk of contracting blood-borne diseases.
Dr Shane Fryer from The Dental Council of NSW says most dentists do the right thing despite the cases illustrating more could be done to educate practitioners.
"I want to assure the public that there are stringent guidelines in place in relation to infection control, that dental practitioners must adhere to," he told reporters on Thursday.
NSW Health says there has been no evidence of transmission, and the risk of infection is low.
But patients of Dr Starkenburg and anyone who had invasive procedures at The Gentle Dentist's Campsie or Sussex St practices should be tested for blood-borne diseases.
Authorities have defended their decision not to go public with the exposure until seven months after Dr Starkenburg's suspension.
Investigations included trawling through the records of 40,000 patients.
"The investigations have been very extensive," Dr Jeremy McAnulty, NSW Health director of Health Protection said.
"It required a number of visits to all the clinics, to reassess issues around infection and control, what the procedures were, what the risks might present."
Investigations into all four surgeries were carried out last year after customer complaints.
Dr Starkenburg was suspended in December and his practice has now closed.
The Gentle Dentist was first investigated in December but significant breaches were not found until February.
Dr Chan was suspended a month later and a further four dentists sometime after that.
Six other staff of The Gentle Dentist also had restrictions put on their licences.
The surgeries remain open but will be subject to continuing investigations and monitoring, Dr Fryer said.
A hotline has been set for those concerned, and people can check whether their dentist is registered on the Dental Board of Australia's website.
Authorities are writing to those patients they think could be affected