Tooth loss in the United Kingdom--trends in social inequalities: an age-period-and-cohort analysis.

This study assessed trends in social inequalities in tooth loss in the United Kingdom between 1988 and 2009. Data from 20,126 adults who participated in the latest three national Adult Dental Health Surveys in England, Wales and Northern Ireland were used. Social class was determined using the 6-point Registrar General's Social Class. Three indicators of tooth loss were analysed; the proportion of edentate people among all adults and the number of teeth and the proportion with functional dentition (defined as having 20+ teeth) among dentate adults. Trends were modelled within an age, period and cohort framework using partial least squares regression (PLSR). Confidence intervals for PLSR estimates were obtained using non-parametric bootstrapping. The Slope and Relative Index of Inequality (SII and RII) were used to quantify social inequalities in tooth loss. Between 1988 and 2009, absolute inequalities in total tooth loss narrowed (SII changed from -28.4% to -15.3%) while relative inequalities widened (RII from 6.21 to 20.9) in the whole population. On the other hand, absolute and relative social inequality in tooth loss remained fairly stable over time among dentate adults. There was an absolute difference of 2.5-2.9 in number of teeth and 22-26% in the proportion with functional dentition between the lowest and highest social classes. In relative terms, the highest social class had 10-11% more teeth and 25-28% higher probability of having functional dentition than the lowest social class. The findings show pervasive inequalities in tooth loss by social class among British adults despite marked improvements in tooth retention in recent years and generations. In the whole adult population, absolute inequalities in tooth loss have narrowed while relative inequalities have increased steadily. Among dentate adults, absolute and relative inequalities in number of teeth and proportion of people with functional dentition have remained significant but unchanged over time.