Income-related inequalities in inadequate dentition over time in Australia, Brazil and USA adults

To assess changes over time of the absolute and relative household income-related inequalities in inadequate dentition (ID) among Australians, Brazilians and USA adults.

This study used nationwide oral health survey data from Australia (n = 1200 in 1999; n = 2729 in 2005), Brazil (n = 13 431 in 2003; n = 9779 in 2010) and USA (n = 2542 in 1999; n = 1596 in 2005). Absolute income inequalities were calculated using Absolute Concentration Index (ACI) and Slope Index of Inequality (SII), while relative inequalities were calculated using Relative Concentration Index (RCI) and Relative Index of Inequality (RII).

Prevalence of ID in the studied period dropped from 8.7% to 3.1% in Australia; from 42.1% to 22.4% in Brazil; and remained stable in USA, nearly 8.0%. Absolute income inequalities were highest in Brazil, followed by the USA and Australia; relative inequalities were lower in Brazil than in Australia and the USA. ID was higher among Brazilian females (2010) and for the poorest group in all countries and periods. A remarkable reduction in absolute inequalities were found in Australia [Slope Index of Inequality (SII) and AIC 60%] and in Brazil (SII 25%; ACI 33%) while relative inequalities increased both in Australia (RCI and RII 40%) and in Brazil (RCI 24%; RII 38%). No changes in absolute and relative income inequalities were found in the USA.

There were still persistent absolute and relative income inequalities in ID in all examined countries. There has been a reduction in absolute income inequalities in ID but an increase in relative income inequalities.