Cross-sectional comparisons of caries time trends in nursery school children in Sendai, Japan.

The aim of this study was to clarify the trends in caries experience in the primary dentition of nursery school children in Sendai, Japan, over a period of 20 yr. An annual clinical dental examination of children aged 2-5 yr at 13 nursery schools in Sendai City was carried out in 1972, 1977, 1982, 1987 and 1992. Data obtained from all five surveys were compared in each age group respectively. The percentages of 2-, 3- and 4-yr-olds free from caries increased remarkably until 1977, while that in 5-yr-olds started increasing several years later. After such increments, percentages in all age groups except 3-yr-olds remained almost at the same level with slight fluctuations. The mean deft and defs values per child in 2-, 3- and 4-yr-olds decreased remarkably until 1977, but then remained almost at the same level thereafter. That in 5-yr-olds continued decreasing slightly during the 20-yr period. The marked reduction of caries experience in nursery school children shown during the 1970's did not continue through the 1980's or the beginning of the 1990's.