Comparing the magnitude of oral health inequality over time in Canada and the United States.

OBJECTIVES To assess the magnitude of, and changes in, absolute and relative oral health inequality in Canada and the United States, from the 1970s till the first decade of the new millennium. METHODS Data were obtained from four national surveys; two Canadian (NCNS 1970-1972 and CHMS 2007-2009) and two American (HANES 1971-1974 and NHANES 2007-2008). The slope and relative index of inequality were used to measure absolute and relative inequality, respectively. Percentage change in inequality was also calculated. RESULTS Relative inequality for untreated decay increased by 91% in Canada and 189% in the United States, while for filled teeth it declined by 63% in Canada and 16% in the United States. Relative inequality in edentulism rose by 200% and 78% in Canada and United States, respectively. Absolute inequality declined in both countries. CONCLUSIONS There was persistent absolute and relative inequality in Canada and the United States. An increase in relative inequality for adverse outcomes suggests that improvements in oral health were occurring primarily among the rich, while reductions in relative inequality for filled teeth indicate higher utilization of restorative services among the poor. These results point to the necessity of tackling the sociopolitical determinants of health to mitigate oral health inequality in Canada and the United States.