Some pre-schoolers are already so self-conscious about their teeth, they are afraid to smile.
Fizzy and sugary drinks - now often cheaper than buying water - take a share of the blame, as do a lack of regular brushing or missed dental appointments which could have caught problems early.
But missing appointments did not mean someone was a bad parent, CDHB community and public health advisory committee member Rochelle Faimalo said.
"A lot of the hubs are open during school hours, which makes it very hard for working parents," she said.
As a busy parent, it was easy to lose track of when children were due for check-ups, she said.
Part of the problem is families falling through the cracks in the dental system.
Pre-schoolers are supposed to have free dental check-ups each year, when they are two, three and four, and then when they start school.
Under the current system, families are called three times within the space of a month to remind them of a check-up.
But if they don't respond or can't be reached within that time, they are cut from the system.
Then unless the family approaches a dentist, the child may completely miss out on check-ups until they start school.
In Canterbury, one in every six pre-schoolers had their enrolment in the programme cancelled.
That was even worse for Māori or Pasifika children.
One in every four pre-schoolers who identified as Māori had their enrolment cancelled, and almost half of Pasifika children.
CDHB health board member Jo Kane said the numbers showed the system had been "an epic fail in many areas".
"This model has been around for a long time, and I think it is time now to ask has it made a difference?" she said.
The children's enrolments are being cancelled even though other departments within the CDHB often have up-to-date contact information for those families.
Planning and funding project specialist Bridget Lester said they were not allowed to share it between departments, because of privacy laws.
That could change next year,
as a new "opt out" system is rolled out.
Under the new system, families will register their children at birth with a range of health providers, and give permission to have their contact information shared within the services, unless they opt out.
Community Dental Service clinical director Martin Lee (above) said it could make a big difference.
"I would be very disappointed if we did not see significant changes within two years," he said.
But it will only catch children born or signed up after it is rolled out.
In the meantime, hundreds of children could still miss out.
Fluoridation has also been raised as an option to try to improve pre-schoolers' teeth.
New legislation which would give district health boards rather than councils the power to decide if water will be fluoridated will come into force in 2018.
BY THE NUMBERS:
•One in every three Canterbury children will have problems with their teeth, from cavities to extractions, by the time they start school
•The average Canterbury pre-schooler will have problems with one tooth, a Māori child two teeth, and a Pasifika child three
•One in every six pre-schoolers had their dental enrolments cancelled because their family could not be contacted - 1184 children in total.
•The CDHB aims to have 95 per cent of preschoolers enrolled in dental services. Last year just 61 per cent were, a drop from 69 per cent in 2014
