AIM: To longitudinally follow and analyse caries prevalence and development in primary dentition in Swedish preschool children from 3 to 6 years of age.

STUDY DESIGN: A longitudinal clinical study.

METHODS: Three hundred 3-year-old children in the Public Dental Service were consecutively included. The children underwent annual clinical examinations at 3, 4, 5 and 6 years of age, performed by four calibrated dentists in clinical settings. Initial (d1-2) and manifest (d3-5) lesions were registered at surface and tooth level. Radiographs were taken when indicated and possible.

STATISTICS: Chi-squared test was used for group comparisons. Friedman's test, Wilcoxon non-parametric test and logistic regression analyses explored caries development over the years.

RESULTS: The parents of 271 children agreed to their children participating in the study (total dropout rate at 6 years, 10.3%). At baseline, 27.3% of the children had carious lesions (d1-5 mean 0.98, SD ± 2.44), and only 50.6% of the children were totally caries-free at 6 years (d1-5 mean 1.88, SD ± 2.81). Initial carious lesions made up the greater share at all ages. The greater part of the caries increment occurred between 3 and 4 years of age (p < 0.001). Having initial and/or manifest carious lesions at 3 years of age was a significant explanatory factor for new lesions at 6 years of age (OR 2.29; 95% CI 1.58-3.31).

CONCLUSION: Children with an early caries experience had a high risk of further disease progression. Oral health promotion and prevention programmes should target small children and their carers.