Two in five children living in Auckland and Northland have one or more decayed, missing or filled teeth when they start school, a new study has found.
The research, conducted by the University of Auckland, found that the rate is higher still in Māori and Pacific children (59 per cent and 65 per cent, respectively); children from very deprived neighbourhoods (60 per cent) and those living in Northland (54 per cent).
Their findings, published in the New Zealand Medical Journal, analysed records from the school-entry dental exams of 27,333 children in 2014-15. It also revealed that children who had been hospitalised for an injury at least once had a higher chance of rotten teeth at school entry.
In a statement, researchers said their findings highlight the urgent need for society-wide actions to improve oral health in young children and to tackle inequalities, including water fluoridation; measures such as a tax and health warnings to reduce consumption of sugary drinks; and oral health promotion that is meaningful in communities where children currently experience poorer oral health.
"Oral health is so important for the wellbeing of children. As a doctor, it is distressing to see children who have painful, eroded teeth when caries [tooth decay and cavities] are so preventable," Waitakere Hospital community paediatrician and researcher Dr Tim Jelleyman said.
"It causes sleepless nights, loss of appetite, and general misery. And the bugs that set up in our mouths early in life probably impact the later health of our permanent teeth."
Researchers said the higher rates in Northland could be reflected in part by the lack of community water fluoridation in the region, a shortage of dentists and minimal regulation on the availability and promotion of sugary foods and drinks in the country.
Researcher Dr Sandar Tin Tin added that while previous overseas studies linked several other childhood medical conditions and infectious diseases, such as asthma and middle ear infections, to an increased risk of tooth decay and cavities, the researchers said they found no evidence supporting it once other risk factors were taken into account.
"Instead, we found that children who had been hospitalised for injuries at least once had a 17 per cent higher chance of caries at school entry," Dr Tin Tin said.
"When we see children with injuries and other illness, probably we should be checking their mouths and discussing good care of teeth with them and their whānau," Dr Jelleyman said.
"Ideally, we want to make water the first drink choice at home, early childhood centres and school, but this kind of shift takes time," says Dr Jelleyman said.
"Avoiding sweet snacks between meals and providing water instead of sugary drinks in places where children play and learn would be worthwhile steps in this direction."