The Influence of War and Post-War Conditions on the Teeth of Norwegian School Children. II. Caries in the Permanent Teeth of Children Aged 7-8 and 12-13 Years
A study of bilateral symmetry for examinations in 1 year showed that the occurrence of caries in each side of the mouth is nearly equal in terms of prevalence rates for specific teeth affected by caries. The percentages of children aged 7 to 8 years who had no caries in the permanent dentition increased 3 to 4 times from 1941 to 1946. After 1946, the percentages decreased to 1949 but remained above the initial levels. The average number of DMF (decayed, missing, filled) teeth per child and also the percentage of total teeth DMF showed a definite decrease in 1942, or in 1943, in almost every instance. In the younger age group (7 to 8 years), the minimum values usually were reached in 1946, whereas in the older age group (12 to 13 years) the lowest values occurred 1 to 3 years later. The percentage reduction in DMF rates was greater at the younger than at the older ages; and varied for different community groups from 31 to 83% at the younger ages and from 27 to 64% at older ages. The trend of curves for the percentage of total surfaces DMF was generally similar to that for the percentage of teeth DMF. Here, too, an inverse correlation between caries susceptibility and caries reduction was found. The rate of extraction of 1st molars dropped in all communities, and in most of them from a level, in the older age groups, of 40-45% in 1941 to a point close to zero at the end of the 1st period, 1949. In all groups the per cent of total teeth DMF, the per cent of total surfaces DMF, the per cent of specific teeth DMF, and the per cent of surfaces DMF in specific teeth increased during the 2nd period of study, 1951-1952 and 1952-1953. Except for a few instances, the latest values did not, however, reach the levels of the initial rates. Girls generally showed higher caries rates than boys.