Objectives <p>This study aimed to investigate the dynamic changes in dental arch size and shape in children with normal occlusion and to evaluate and visualize the effects of early orthodontic treatment.</p> Methods <p>A total of 274 normal occlusion subjects (4 to 12 years, mean age 7.38 years) were selected from a pool of 2,695 school-age children in Chengdu. These subjects were divided into 5 age groups according to Hellman’s dental ages. The complete dental arch forms were described using polynomial fitting curves. To observe changes in arch size, the average arch width, depth, and perimeter were measured for each group. To analyze changes in arch shape, the arch forms were normalized using the max-min normalization and then divided into 6 clusters (grouping of shapes) using the k-means algorithm. The proportions of these clusters across different age groups were then determined.</p> Results <p>The periods of rapid occlusal development occur between the ages of 4 to 8 years and 11 to 12 years, during which the arch width, depth, and perimeter increase rapidly. As children grow, the complete dental arch shape becomes more elongate. To assess and visualize early orthodontic treatment effects, typical normal arch shapes can be scaled to fit the size of individual cases.</p> Conclusion <p>The size and shape of arch form change dynamically from late primary dentition to early permanent dentition. Notably, the arch depth tends to increase more than the arch width.</p> Clinical relevance <p>A well-conducted early orthodontic treatment may bring the arch form closer to the typical normal one.</p>