In the annual inspection of the school children of Rochester, a high incidence of dental caries was found. This corresponds roughly to observations elsewhere in the northern states. In order to evaluate the possible etiologic factors, two groups of children were selected for comparison: twenty-five with perfect or nearly perfect teeth and twenty-five with marked dental caries. It seemed probable that the differences would be most striking if extremes were chosen.
In the inspection of the children in the Rochester public schools, the names were recorded of all who had exceptionally good or exceptionally poor teeth. In the first group were those whose teeth were free from caries and had not required dental work or had possibly two or three small fillings, and the enamel appeared smooth, hard and healthy, although not necessarily well cared for. In the second group were those whose teeth showed dental caries involving