Introduction Despite dental pain being an important public health issue, very few studies have investigated its occurrence in preschool children using a life course approach. The objective of this study was to describe the prevalence of dental pain in preschool children and its association with life course characteristics.

Methods This study was nested in a population-based birth cohort from Pelotas, Brazil, started in 2004. A sample of 1129 children aged 5 years old underwent dental examination and their mothers were interviewed. Exploratory variables included sociodemographic factors, maternal oral health status and associated behaviours, and children's primary dental caries. Data were analysed using multi-variable Poisson regression.

Results Toothache was present in 16.5% of the population in the 6 months prior to interview. Adjusted analyses showed that dark-skinned children [Prevalence ratio (PR)=1.6 (95% CI 1.1 to 2.4)], from low economic level [PR 1.9 (1.2 to 3.0)], whose mothers had <4 years of study [PR 1.9 (1.0 to 3.6)], and whose mothers with <10 teeth in one arch at least [PR 1.66 (1.09 to 2.53)], and those with high caries prevalence at age 5 years [PR 4.8 (3.3 to 7.1)] were associated with dental pain.

Conclusions Low family income and lack of children's schooling are the main early life risk factors for dental pain in preschool children. Poor maternal and child dental status are associated with dental pain. The socioeconomic and family context in which dental pain occurs should be taken into account when dental pain preventive measures are implemented.