The importance of understanding barriers to dental attendance of adults in the UK was acknowledged in the first Adult Dental Health Survey in 1968 and has been investigated in all subsequent ADH surveys. In 1968, approximately 40% of dentate adults said they attended for a regular check-up; by 2009 this was 61%. Attendance patterns were associated with greater frequency of toothbrushing, use of additional dental hygiene products, lower plaque and calculus levels. Just under three-fifths of adults said they had tried to make an NHS dental appointment in the previous five years. The vast majority (92%) successfully received and attended an appointment, while a further 1% received an appointment but did not attend. The remaining 7% of adults were unable to make an appointment with an NHS dentist. The majority of adults were positive about their last visit to the dentist, with 80% of adults giving no negative feedback about their last dentist visit. Cost and anxiety were important barriers to care. Twenty-six percent of adults said the type of treatment they had opted for in the past had been affected by the cost and 19% said they had delayed dental treatment for the same reason. The 2009 survey data demonstrated a relationship between dental anxiety and dental attendance. Adults with extreme dental anxiety were more likely to attend only when they had trouble with their teeth (22%) than for a regular check-up.

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.

When coordinating movements, the nervous system often has to decide how to distribute work across a number of redundant effectors. Here, we show that humans solve this problem by trying to minimize both the variability of motor output and the effort involved. In previous studies that investigated the temporal shape of movements, these two selective pressures, despite having very different theoretical implications, could not be distinguished; because noise in the motor system increases with the motor commands, minimization of effort or variability leads to very similar predictions. When multiple effectors with different noise and effort characteristics have to be combined, however, these two cost terms can be dissociated. Here, we measure the importance of variability and effort in coordination by studying how humans share force production between two fingers. To capture variability, we identified the coefficient of variation of the index and little fingers. For effort, we used the sum of squared forces and the sum of squared forces normalized by the maximum strength of each effector. These terms were then used to predict the optimal force distribution for a task in which participants had to produce a target total force of 4–16 N, by pressing onto two isometric transducers using different combinations of fingers. By comparing the predicted distribution across fingers to the actual distribution chosen by participants, we were able to estimate the relative importance of variability and effort of 1∶7, with the unnormalized effort being most important. Our results indicate that the nervous system uses multi-effector redundancy to minimize both the variability of the produced output and effort, although effort costs clearly outweighed variability costs.

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