Patients of former dentist William Tam, who practised at Strathfield in Sydney's inner west for more than 25 years, are being urged to test for hepatitis B and C and HIV after the NSW Dental Council inspected his clinic in April.
The audit found deficiencies in sterilisation of equipment and cleaning practices and substandard and incomplete records that have prevented authorities from individually identifying and contacting patients.
Dr Tam's former patients who underwent invasive procedures, including those that drew blood or pierced skin, may be at slightly higher risk of bloodborne virus infection, but the risk was still considered to be low, NSW Public Health Unit specialist Zeina Najjar said.
"Any former patient of Dr Tam's is at a low risk of bloodborne virus transmission," Dr Najjar said.
"There have been no cases of bloodborne virus transmission linked to this practice, but we're still recommending testing as a precaution."
Dr Tam has since retired and is no longer a registered dentist but people who might have contracted any of these viruses may not show any symptoms for decades, so the need for testing is still high, Dr Najjar said.
The alert comes a year after clients of a beauty clinic in inner Sydney were warned about their possible exposure to the same viruses due to misuse of equipment.
Inspectors for the NSW Health Care Complaints Commission found in March 2025 that workers might have been pretending to be doctors and injecting people with botox, hyaluronic acid and dermal fillers.
A large amount of surgical equipment was seized that was "clearly marked as being for veterinary use only", as well as large amounts of controlled medication were found, the commission said.
NSW Health put out a similar alert in October after an audit of dental practitioner Safuan Hasic's practice identified potential infection breaches.
A bloodborne virus could have spread from one patient to another on dental instruments. All of his patients were urged to see a GP for precautionary testing.
12°C