Serendipitous results of a pilot study: precaution indicated.

A pilot study was conducted to estimate sample size for a clinical trial in a F area. In 1992, 98 children 14 years of age living in Fall River, MA were examined for dental caries: Fall River was fluoridated in 1973. Residence histories showed that 74% lived there from birth (B), 12% were residents from kindergarten or 1st grade (K1) and 14% moved into the community at a later time (LT). Findings on caries prevalence showed an inverse relation between DMFS and initial age of residence; mean DMFS was 3.00 for Group B, 5.33 for Group K1 and 6.93 for Group LT. A one-way ANOVA indicated significant differences among the groups (p=0.05). Because residence from birth or from early life can be considered a proxy for systemic fluoride exposure, and because controversy currently surrounds the issue of topical versus systemic benefits in explaining the mechanism of action of fluoride, the results appeared to have importance. However, internal analyses of the data comparing surface-specific (pit and fissure) results among the groups for early erupting teeth with varying systemic exposure to fluoridated water and for late erupting teeth, all with appreciable systemic exposure, showed comparable relative differences in DMFS scores. Lack of internal validity, therefore, discounted a conclusion from overall results of the role of systemic fluorides in providing decay preventive benefits. If there is any conclusion that can be drawn it is that serendipitous escapades with data from a pilot study, if not rigorously analyzed and cautiously interpreted, tend to further muddy the waters (fluoridated in this case) on controversial issues and should best be avoided.