This study aim was to evaluate the need for orthodontic treatment of mixed to permanent dentition using the Dental Aesthetic Index (DAI) in a 4-year follow-up. A longitudinal study was conducted with 353 children in the stages from mixed (T1) to permanent (T2) dentition. The need for orthodontic treatment was assessed using the DAI categorized into: DAI 1 (absence of malocclusion and orthodontic treatment need; DAI ≤ 25); DAI 2 (malocclusion is defined and elective orthodontic treatment is needed; DAI = 26 to 30); DAI 3 (severe malocclusion and a desirable orthodontic treatment need; DAI = 31 to 35) and DAI 4 (severe malocclusion and a mandatory orthodontic treatment need; DAI ≥ 36). The Bowker symmetry test was used to determine agreement in the categorization of DAI at T1 and T2, with a significance level of 5%. The results showed a significant disagreement in the need for orthodontic treatment between T1 and T2 (p<0.05). In 34.6% of children evaluated in T1, the same need for orthodontic treatment was maintained in T2. According to the DAI, in 60.8% of the children, the need decreased, and in 39.2% their need for orthodontic treatment increased. This preliminary longitudinal study using DAI, showed a decrease in malocclusion and need for orthodontic treatment as the dentition transitioned from mixed to permanent occurred. This finding has valuable implications for epidemiological data in orthodontics.