The aim of the study was to examine the caries experience of 10-year-olds as measured with dmft/DMFT, to explain how caries increases by the age of 10 years, and which factors would explain caries increments. The setting was a representative population sample of first-born children in southwestern Finland. Dental health at 10 years of age was found to be good in 45%, fairly good in 40% and poor in 15% of the children. The caries index remained stable in 23% of carious children from 7 to 10 years of age. Daily consumption of sweets at the age of 3 years (OR 2.7; 95% CI 1.5-4.8; p < 0.001) was associated with a caries increment between 7 and 10 years of age (both deciduous and permanent teeth). This daily consumption of sweets and a child's late bedtime (OR 1.9; 95% CI 1.1--3.1; p = 0.023) were explanatory factors in the permanent teeth alone. In the deciduous teeth, mother's previous caries and child's earlier tooth brushing habits were explanatory factors of caries. As hypothesized, all five significant factors remaining in the final logistic regression analysis were family-related. Parental ability to care for and educate a child could be seen in dental health still at the age of 10 years. The family-related factors which were associated with caries should be emphasized much more comprehensively in everyday dental health care practice.