TOOTH AND TOOTH SURFACE SURVIVAL RATES IN BIRTH COHORTS FROM 1965, 1970, 1975, AND 1980 IN LAHTI, FINLAND

Differences in the tooth and tooth surface survival rates between four cohorts born in 1965, 1970, 1975, and 1980 were analysed in a histori cal cohort study including data on the permanent teeth of children age d 5-7 years at baseline and 19 years at the end of the study. A statis tically significant reduction in caries occurrence in fissured surface s in the three oldest cohorts was seen during the 3 years after the er uption of the teeth. Caries occurrence in the cohorts born in 1975 and 1980 did not differ from each other. The occurrence of caries in smoo th surfaces was low in all age cohorts. Therefore, despite a systemati c decrease in caries occurrence towards the younger cohorts, no signif icant differences were found between the cohorts in smooth surface dec ay. After the 3 first posteruptive years, practically no differences i n survival rates between the cohorts were observed. In the two younges t cohorts, the figures during the 3 first years after eruption did not differ from the figures for the later years. Throughout the study, ca ries occurrence was symmetric and no gender differences were observed. No postponement of decay was found by the end of the follow-up time.