• caries;
  • fluoride;
  • fluoridation;
  • preeruptive hypothesis;
  • posteruptive hypothesis;
  • evidence-based dentistry;
  • epidemiology;
  • laboratory.


Discussion, which can get spirited, has been going on about fluoride's primary mode of action for some years. In the early days of fluoride research, it was assumed that the anticaries benefits of fluoride came from preeruptive effects; however, posteruptive action was soon evident. Today the primacy of the posteruptive hypothesis is hardly questioned; remaining questions concern the role of preeruptive fluoride. We are in the age of evidence-based dentistry, where we expect scientific evidence to shape our conclusions. In this cursory look at the data from fluoride studies, the data to support the posteruptive hypothesis are consistent from laboratory to epidemiology; findings in human populations support the mechanisms of action that have been demonstrated in the laboratory. With the preeruptive hypothesis, there is some evidence in support; however, the data are not consistent across the different areas of study. As a result, the posteruptive hypothesis can be readily adopted as the primary mechanism for fluoride's anticariogenic action. Preeruptive fluoride may have some anticaries action; but when the evidence-based philosophy is applied, the inconsistencies around the preeruptive hypothesis make it hard to adopt.