Changes in dental caries in Zurich school-children over a period of 45 years.

In 16 rural communities of the Canton of Zurich, school-children of all age groups participated in dental examinations conducted at intervals of 4 years since 1963/64. The same standardised method was used throughout the entire period. This study documents the caries experience over a period of 45 years. From 1964 to 2009, the DM*FT per 14-year-old child fell from 12.50 to 1.31, corresponding to a caries reduction of 90%. The caries experience in 8-, 10- and 12-year-olds decreased by 90% to 92%. From 1964 to 2009, the "Significant Caries Index" (the mean DM*FT in the third of 12-year-olds with the highest DM*FT values) fell from 13.09 to 2.20, corresponding to a caries reduction of 83%. The observed caries decline was unexpectedly high. The effect of fluorides may explain a caries reduction of roughly 50%. A large part of the decline, however, remains unexplained. Possible causes are discussed in this paper.