Measuring inequalities in the distribution of dental caries.

OBJECTIVES: To evaluate different measurements of prevalence and inequality in the distribution of dental caries as to their partial collinearity, and ability in expressing associations with the supply of fluoridated tap water, indices of socioeconomic status and provision of dental services. METHODS: The DMFT, the Significant Caries (SiC) Index, the proportions of children with high- (DMFT > or = 4) and rampant- (DMFT > or = 7) caries experience, caries-free children (DMFT = 0), the Gini coefficient and the Dental Health Inequality Index (DHII) were the dental outcomes appraised in a sample comprising 18 718 oral examination records for 11- and 12-year-old schoolchildren in 131 towns of the state of São Paulo, Brazil. Spatial data analysis assessed the association between aggregate figures of dental indices and several covariates. RESULTS: The DMFT, the SiC Index and the proportions of children with high- and rampant-caries experience presented strong linear associations (Pearson r near or higher than 0.95), and an analogous profile of correlation with indicators of socioeconomic status, dental services and access to fluoride tap water. The same was observed for the DHII, the Gini coefficient and the proportion of caries-free children. These observations involve the perception of variables in each set as interchangeable tools for ecological studies assessing factors influencing, respectively, prevalence levels and inequality in the distribution of dental disease. CONCLUSION: An improved characterization of the skewed distribution of caries experience demands the concurrent estimation of figures of prevalence and inequality in dental outcomes. This strategy may contribute to the design of socially appropriate programmes of oral health promotion.

Quantifying dental inequality--developing the methodology.

OBJECTIVE: To develop a simple quantitative measure of dental health inequality. METHOD: Define equality based on statistical theory and construct a formula to compare actual and theoretical disease distributions. RESULT: A new index (DHII) is proposed, based on the ratio of the distribution of the actual disease to a (theoretical) Poisson distribution. An example using caries data is provided. CONCLUSION: Use of DHII will allow quantitative measurement of dental health inequality.