Objective: The first aim was to describe presence of plaque, caries and oral health behaviours in 2-year-old children. The second aim was to measure increments in caries experience from 2 to 5 years of age and to study whether national background, visible plaque, caries and oral health behaviour at 2 years of age were associated with increments in caries experience. Methods: The study population consisted of 392 children, of whom 211 were monitored from 2 to 5 years of age. At age 2 years, parents completed a questionnaire about family background and oral health behaviour. The presence of plaque and caries at tooth level was obtained from dental records. Data were tested with chi-square statistics and Mann-Whitney U test. Negative binomial regression analysis was conducted to explore the association between caries increment between 2 and 5 years of age and national background, visible plaque, caries and oral health behaviour at 2 years of age. Results: Caries was found in 4.6% of 2-year-olds, and 4.6% had visible plaque. More than half of these children (57.9%) brushed twice daily, toothbrushing was introduced when the child was 7 months or older in 61.0% of the children, and 15.6% consumed sugary snacks daily. Non-Western children more often had caries, visible plaque and unfavourable oral health behaviour than Western children (P < .05). At age 5 years, 28.9% of the children had caries experience. Non-Western background, toothbrushing less than twice daily, not using fluoridated toothpaste, not using fluoride lozenges, consuming sugary drinks at night, consuming sugary snacks daily, presence of plaque and caries at 2 years of age were associated with caries increment between 2 and 5 years of age in bivariable analyses. The results from multivariable analysis showed that children who started toothbrushing late, children who brushed less than twice daily at 2 years of age and children of non-Western background had a higher probability of having caries increment from 2 to 5 years of age than other children. Conclusions: A small proportion of 2-year-olds had caries, but these children had several decayed teeth. Substantial differences in oral health and oral health behaviour were found between Western and non-Western children. The preventive care delivered to the studied children failed to prevent caries increment from 2 to 5 years of age.
