About 2500 children who visited Pukekohe Intermediate Dental Clinic between September 13, 2016 and January 23 could be at risk due to malfunctioning dental equipment.
Counties Manukau DHB said there was a "very small chance" children who had particular procedures have been exposed to unsterilised water, possibly containing blood or saliva from other children.
An investigation is under way into the exact nature of the problem and how it occurred.
Specialist public health nurses will contact parents and caregivers of children who might have been affected to arrange appropriate screening.
Children who have had a procedure involving compressed air, a drill, extraction or suction, will be offered testing for blood-borne viral infections, in particular Hepatitis B, Hepatitis C and HIV.
However, infectious disease specialists have indicated the risk of cross-infection is very low as it is extremely rare for New Zealand children to have any of these conditions.
"If we do find cases of pre-existing infection, then we will prioritise screening for those children who were treated on the same day," Counties Manukau chief medical officer Dr Gloria Johnson said.
"Some children may also need catch-up immunisations against Hepatitis B."
There is extremely low risk of infection, if any, to other family members.
Engineers are investigating how the problem could have occurred including involving a specialist maintenance company and the United States manufacturers of the equipment.
"The problem occurred due to equipment assembly and is not related to the clinical practice of the dental staff at the clinic, or the high quality care given to children across Auckland," Dr Johnson said.
Dr Johnson said incidents of this nature are extremely rare and parents should not let this affect their children's attendance at school dental clinics.
"Our investigation will determine what longer term mitigations need to be put in place to ensure this type of fault doesn't occur in future."
As a result of this incident, all Auckland Regional Dental Service dental clinics in the Auckland Region have been reviewed and the issue is only with the Pukekohe Intermediate Dental Clinic.
Anyone with concerns is encouraged to contact Healthline on 0800 611 116 or talk to their GP if they require further information or support.
