This series of four papers reports and interprets the findings of the Adult Dental Health Survey (ADHS), 2009, published in early 2011. This is the fifth in a series of surveys repeated every decade since 1968. The evolution of the surveys and the way the supporting methodology has changed to meet the changing needs and circumstances over the last 40 years is described. In 1968, 37% of adults in England and Wales were edentate. By 2009, only 6% of the combined population of England, Wales and Northern Ireland were edentate. Among the dentate in 1968, there were a mean of 21.9 teeth. By 2009, not only had the dentate increased by 30 percentage points as a fraction of the population, but the number of teeth in this group had also increased by nearly four teeth on average to 25.7. There were significant variations in oral health according to geography and social variables and smaller differences according to sex. The retention of 21 or more teeth is widely used as a way of defining a minimum functional dentition. The proportion of adults with 21+ teeth increased from 73% in 1978 to 86% in 2009. Further huge improvements are projected as younger generations age, assuming future tooth loss continues at current low rates. We might expect that over 90% of those aged 35-44 in 2009 have a realistic prospect of retaining a functional natural dentition of 21 or more teeth by age 80.