Race- and Income-Related Inequalities in Oral Health in Australian Children by Fluoridation Status

Inequality in child oral health exists by race and income. Water fluoridation (WF) is effective in caries prevention, but evidence for WF reducing inequality in caries experience is equivocal. This study tested the hypothesis that WF reduces race- and income-related inequality in child caries experience. A cross-sectional national population-based study of child oral health was conducted across 2012 to 2014 for Australian children aged 5 to 14 y, involving a parental questionnaire and an oral epidemiological examination. Children were stratified by fluoridated (F) and nonfluoridated (NF) area of residence, equivalized household income quartiles, and Indigenous and non-Indigenous status. Directly standardized caries experience (measured by the decayed, missing, or filled tooth surfaces [dmfs/DMFS] in both primary [age 5-10] and permanent dentitions [age 9-14]) was estimated for each stratum accounting for the complex sampling design. Differences in caries experience by Indigenous status and equivalized income quartiles were examined between F and NF strata. Socioeconomic inequality in caries experience was examined using the Absolute Concentration Index (ACI), Slope Index of Inequality (SII), Relative Concentration Index (RCI), and Relative Index of Inequality (RII). A total of 21,328 (86.5%) children had complete data. Caries experience was higher in NF than F strata. Race- and income-related gradients in caries experience were observed in both F and NF areas. All indexes of inequality indicated that caries experience was concentrated among lower income groups. Absolute inequalities were consistently lower in F than in NF areas. For the primary dentition, SII values were -4.18 versus -6.20 in the F and NF areas, respectively. The respective values were -0.60 versus -1.66 for the permanent dentition. Income-related inequality in caries was lower in F than in NF areas for both Indigenous and non-Indigenous children. WF was associated with lower caries experience and reduced inequality among children. Knowledge Transfer Statement: The results of this study greatly increase the evidence base that water fluoridation is effective and socially equitable. Dental caries has remained one of the most prevalent chronic conditions in children worldwide. The presented evidence can be used by policy makers and the profession to support the maintenance or expansion of this important public health program to benefit those most at risk of dental caries, the groups at the lowest socioeconomic position in any society.