The method Adopted.
Twenty-five centres were selected for study, extending from Whangarei in the north to Invercargill in the south. The localities were chosen as being representative of all parts of the Dominion, including farming, industrial, fruit growing and coal mining areas,
in addition to typical town and city residential areas of varying economic status. In each area the new school entrants for the year were examined, that is, children in the 5–6 year age group. In most cases the group included all the new entrants for the period, thus reducing the possibility of deliberate or unconscious selection to a minimum. The new school entrants were selected because any later age group would be receiving regular dental attention from the School Dental Service, and consequently would not present such a favourable field for study. The dental examinations of the 1,475 children were made by officers of the School Dental Service, in accordance with detailed instructions designed to secure uniformity, and a caries index was calculated for every child in accordance with a formula evolved by the writer. An endeavour was made to have a general physical examination made in each case, but this proved only partially successful, and the number who were medically examined was relatively small.