Children had rotten teeth removed under general anaesthesia because of delays and follow-up problems in the public dental service.
Families of the two children affected - one a preschooler - have received apologies from the Auckland Regional Dental Service (ARDS), which provides care to children across wider Auckland, mostly through school clinics and mobile dental vans.
The failures have been revealed in a report by Waitematā DHB, which is responsible for the service and has published a list of serious adverse events over 2018/19 - incidents where patients were seriously harmed.
• Health Minister David Clark considering dental care report as calls for free treatment grow
• Junk food ads to be banned from around schools in anti-obesity actions agreed with industry
• Warning as power drills, pliers used in DIY dentistry by Kiwis who can't afford dentists
In one incident, a child was seen by a graduate who didn't seek assistance from a more experienced colleague. The wrong schedule for ongoing treatment was set-up, and fluoride varnish wasn't used on the two occasions the child was seen by ARDS.
There wasn't any ongoing support given to the family, or treatment given in the interim after a referral was made. The delays resulted in the child being put under general anaesthesia to have badly rotten teeth removed.
Recommendations made after the failure in treatment included all new graduates being assigned a mentor, to examine and chart all teeth every time a child is examined, and for at-risk preschoolers to be put on a six-monthly recall visit roster, unless there are good reasons not to.
In the second incident, the service made numerous attempts to contact a child's family, but these were mostly unsuccessful and "the social circumstances of the child's family, including where the child was living, were not understood or sought".
Eventually, a private dental clinic contacted ARDS and told them urgent treatment was needed for the child. However, there was no active follow up, causing a delay of nearly eight months. That resulted in "extensive treatment" under general anaesthesia.
Recommendations that followed included checking a family's contact details at each visit, and to complete annual audits to ensure contact information is properly recorded.
A spokeswoman for Waitematā DHB said the recommendations had been implemented, along with ongoing monitoring. Transparency about such events was important to prevent them happening again.
"We are pleased to see that these improvements are having positive benefits for the children accessing the service across our 83 dental clinics."
The service had about 280,000 children on its books and the two events were outliers, the spokeswoman said. Apologies had been given to the families involved.
According to 2018 national data from community dental services, nearly 40 per cent of 5-year-olds who were checked had some decay of a tooth or bone.
The problem is much worse in poorer areas. A recent survey at Auckland's Pt England School found that by the time they were five-and-a-half, a quarter of new entrants either had or needed tooth extractions under general anaesthesia.
The New Zealand Dental Association has led calls for the Government to take stronger action to curb consumption of sugary drinks and food, including through a sugar tax, restrictions on advertising and marketing, and warning labels on sugar content.
However, the Government has ruled out a sugar tax, and has favoured voluntary measures suggested by industry, including banning junk food and drink advertising from around primary and intermediate schools.
Health Minister David Clark has also declined to introduce policy to remove junk food and drink from school tuckshops or vending machines, saying such efforts should be driven by communities and not central government.