This was confirmed by a study reported this month in the New Zealand Medical Journal:
Caroline Fyfe, Barry Borman, Guy Scott, S. B. (2015). A cost effectiveness analysis of community water fluoridation in New Zealand. New Zealand Medical Journal, 128(1427).
The study is available to download as a poster presentation here.
Previous studies – most recently in 2001 – had shown CWF to be cost-effective. However, oral health has improved in both fluoridated and fluoridated areas so the new study was undertaken to check if CWF “remained a cost-effective public health intervention in New Zealand in the 21st century.”
The results show that CWF is still cost-effective. The post concludes:
“This cost effectiveness analysis supports an earlier economic analysis of community water fluoridation in New Zealand by Wright et. al. (2001) 3 . CWF remained a cost effective public health intervention in New Zealand despite an overall reduction in dental caries. This finding also agrees with a number of economic analyses of CWF conducted in countries similar to New Zealand, 7, 9-11 . It should be noted however, that for smaller communities cost effectiveness was more marginal. Wright et. al. (2001) identified a ‘break even’ community size for CWF of 700-900 people 3 . In smaller communities cost effectiveness was more dependent on the risk profile of the population. CWF would be more cost effective in communities with a higher risk of dental caries.”
The reduced cost-effectiveness for smaller communities is due to the relatively greater per-capita cost of the fluoridation plants and chemicals in such situations. This table below from the poster gives an idea of how community size influences the cost-effectiveness of CWF. It might need a bit of thinking – the negative values are the average annual per capita net cost of CWF per unit of decayed, missing and filled teeth (dmft/DMFT).