September 2019

Objective: A review of the distribution of d3mft scores for Wales was undertaken to inform decisions on future reporting of decay experience. Visual examination of data from one survey suggested that caries in Wales is distributed along an exponential decay curve. Basic Research Design: Weighted d3mft data from 2007/8, 2011/12 and 2014/15 was utilised. The data was compared with a pragmatically chosen exponential decay model. Distribution curves for d3mft were plotted for each data set, correlation coefficients calculated and residuals plotted. Results: The three surveys demonstrate similar exponential decay distributions across the range of d3mft scores. Plots of each curve against the exponential decay model demonstrated close correlation (0.9826 – 0.9871). The progressive shift of these similarly shaped curves suggest similar levels of caries reduction across the spectrum of caries experience and thus improved oral health without widening of health inequality. The close fit with this simple mathematical model suggests that caries prevalence could be used to generate a theoretical distribution and thereby and estimate of mean d3mft score. Such an approach could facilitate simplified oral health surveillance in areas where caries distributions are known from previous surveys. Conclusions: Within Wales caries does seem to be distributed in line with an exponential decay curve. As a result decay prevalence and mean d3mft are mathematically related. This finding may have potential to support simplified local oral health surveillance. The data provides evidence suggesting improvements in caries experience in Wales are not at the expense of increased inequality. Key words: Dental caries/epidemiology; DMF Index; Models, statistical