Childhood caries experience in two Aotearoa New Zealand birth cohorts: implications for research, policy and practice.

Oral health in Aotearoa New Zealand has improved in the last seven decades, but improvements among young children have stagnated in the last two. Four out of ten 5-year-olds are affected by caries and many pre-schoolers require dental treatment under general anaesthesia. We analysed data from two longitudinal studies, the Dunedin Multidisciplinary Health and Development Study and the Christchurch Health and Development Study. We compared their methods, cohort characteristics and childhood oral health findings and discuss their implications for policy, research, and practice. Age 5 dmft was obtained in the Dunedin Study from clinical examinations, and from School Dental Service records in the Christchurch Study. Findings were consistent with respect to childhood socioeconomic status, exposure to community water fluoridation, and maternal education. Despite overall improvements, caries rates remain relatively unchanged: dmft in these cohorts, measured in the 1970s-1980s, resemble New Zealand's statistics for 5-year-olds in the 2000s. Notwithstanding the steep caries decline observed over the years, the caries distribution has shifted, whereby the greatest severity of disease is now concentrated among a smaller group of the most deprived children. Early childhood caries appears to be a useful indicator of deprivation that should inform interventions for those in greatest need.