Caries experience in primary teeth of four birth cohorts: a practice-based study

To investigate the survival of caries-free primary teeth in four age cohorts in the city of Kemi, Finland, as well as association of survival of primary teeth among boys and girls and among high and low caries risk individuals.

This was a practice-based follow-up study based on dental records.

The data were collected from the electronic oral health patient records of the municipal health centre of the city of Kemi, covering four different birth cohorts (1985, 1990, 1995 and 2000). The total number of children was 4,488.

Kaplan-Meier curves were drawn to illustrate the survival of caries-free primary molars . Statistical difference between the groups was analysed using the log-rank test and Cox proportional hazards regression analysis. The retrospective caries risk definition for individuals was based on the early restorations in the first permanent molars.

In the earlier cohorts, primary molars survived caries-free for a shorter period than in the later cohorts (p < 0.001). However, in the 2000 cohort, the survival curve, having shown at the beginning only some caries incidence, bended strongly downwards at the age of 8 years. The survival time of the primary molars remaining caries-free was shorter for those with high caries risk (p < 0.001) as well for boys compared with girls in all cohorts (p = 0.001).

The course of the survival curve of the 2000 age cohort indicates a halt in the improvement of dental caries prevalence, but the follow-up period was too short to allow monitoring the progress further. Continuing oral health promotion to all children, and particularly risk individuals must be emphasised.