The relative cost effectiveness of water fluoridation across communities: analysis of variations according to underlying caries levels.

The effectiveness of water fluoridation as a means of reducing the prevalence of dental caries is well established in the dental literature. The case for water fluoridation however rests on the size of this reduction and the benefits that could be produced by using the same resources in other oral health or dental care programmes. In this paper the cost-effectiveness of water fluoridation is analysed for communities of different sizes and with differing oral health levels. Using the traditional model of economic evaluation, data from recent epidemiological studies, and a number of simplifying assumptions, it is shown that the cost per unit health benefit produced from water fluoridation varies by a factor of four according to the existing level of caries prevalence. Furthermore this is likely to be a conservative estimate of the differential impact given the nature of the assumptions. Marked differences in cost-effectiveness are also found for communities of different sizes suggesting that important economies of scale occur in water fluoridation projects. As a consequence cost effectiveness estimates of water fluoridation projects should be assessed on their own merits to ensure that scarce health care resources are used efficiently, i.e. in a way which maximises the impact these resources have on population health status.