The relationship between social background, water fluoridation, use of fluoride tablets and dmf scores was studied in a birth cohort of 7-yr-old New Zealand children. This analysis showed that the level of exposure to additional fluoride was a complex variable influenced by at least three factors: the use of fluoride toothpaste; the child's length of residence in a fluoridated area; the length of time for which the child had been provided fluoride tablets. Log linear modelling of the data suggested the presence of a relatively complex relationship between exposure to additional fluoride, social background and dental health. First, both duration of residence in a fluoridated area and the provision of fluoride tablets made significant net contributions to the variability in the dmf score. However, exposure to additional fluoride from these sources was differentially influenced by social background: while there were relatively strong associations between social background and the use of fluoride tablets, there was no significant association between duration of residence in a fluoridated area and social background. Finally, independently of an association with exposure to additional fluoride, family social background made a significant net contribution to the variability in dmf scores.