AbstractBackgroundInitial caries lesions in primary teeth have presented a low progression rate after 2 years, but it could be higher in longer follow‐ups.AimTo evaluate the progression rates of sound surfaces and initial and moderate caries lesions after 7 years.DesignThis prospective 7‐year cohort study included 639 preschool children aged 1–5 years in 2010. In 2017, 449 children were reassessed (70.3% retention rate). Dental caries was collected using the International Caries Detection and Assessment System (ICDAS) in both assessments. Incidence rate (IR) per 100 surface‐years estimated the progression rates of sound surfaces and initial and moderate lesions for worse conditions. Cox regression with shared frailty evaluated the possible risk factors.ResultsIR was 1.0% for sound surfaces, 2.8% and 4.2% for ICDAS scores 1 and 2, respectively, and about 17.0% for moderate lesions. The most significant risk factor for the progression was the presence of cavitated lesions in other teeth. The type of surface and tooth also influenced the outcome.ConclusionThe progression rate of initial caries lesions in primary teeth remains low even after 7 years, but cavitated caries lesions in other teeth increase this risk. Moderate lesions demonstrate a higher risk of progression when compared to sound surfaces and initial caries lesions.