Hundreds of dental patients have been offered blood tests over fears they could have been exposed to HIV or Hepatitis B or C.
Dirty equipment may have been used to treat 563 patients of a former hygienist at Dentality@Hoddesdon.
Public Health England (PHE) said it was investigating “potential breaches of infection control procedures”.
The practice said an independently contracted hygienist had been dismissed following an investigation.
Letters have been sent to all the Hertfordshire practice’s patients who are understood to have received dental ultrasonic scaling from the self-employed hygienist, Ekta Parikh.
Principal dentist Dr Vishaal Shah said: “As soon as we became aware of behaviour from a hygienist that did not meet the rigorous standards we expect from our entire team, we immediately launched a full investigation, and escalated