Water fluoridation, tooth decay in 5 year olds, and social deprivation measured by the Jarman score: analysis of data from British dental surveys.

OBJECTIVE To examine the effect of water fluoridation, both artificial and natural, on dental decay, after socioeconomic deprivation was controlled for. DESIGN Ecological study based on results from the NHS dental surveys in 5 year olds in 1991-2 and 1993-4 and Jarman underprivileged area scores from the 1991 census. SETTING Electoral wards in three areas: Hartlepool (naturally fluoridated), Newcastle and North Tyneside (fluoridated), and Salford and Trafford (non-fluoridated). SUBJECTS 5 year old children (n = 10,004). INTERVENTION Water fluoridation (artificial and occurring naturally). MAIN OUTCOME MEASURE Ward tooth decay score (score on the "decayed, missing, and filled tooth index" for each electoral ward). RESULTS Multiple linear regression showed a significant interaction between Jarman score for ward, mean number of teeth affected by decay, and both types of water fluoridation. This confirms that the more deprived an area, the greater benefit derived from fluoridation, whether natural or artificial (R2 = 0.84, P < 0.001). At a Jarman score of zero (national mean score) there was a predicted 44% reduction in decay in fluoridated areas, increasing to a 54% reduction in wards with a Jarman score of 40 (very deprived). The area with natural fluoridation (at a level of 1.2 parts per million-higher than levels in artificially fluoridated areas) had a 66% reduction in decay, with a 74% reduction in wards with a Jarman score of 40. CONCLUSION Tooth decay is confirmed as a disease associated with social deprivation, and the more socially deprived areas benefit more from fluoridation. Widespread water fluoridation is urgently needed to reduce the "dental health divide" by improving the dental health of the poorer people in Britain.