Objectives: This clinical trial investigated the effectiveness of three minimal intervention dentistry protocols in arresting dentin caries in primary molars of preschool children. Treatment time, anxiety in children, adverse events, and parents’ esthetic perception were all assessed. Materials and methods: One hundred thirty-five 3–5-year-old children with active dentin caries lesions on the occlusal surface of primary molars were randomly allocated to the control group receiving atraumatic restorative treatment (ART) and two test groups receiving 38% silver diamine fluoride (SDF) or ultraconservative treatment (UCT). The existence and activity of caries were assessed using the International Caries Detection and Assessment System II (ICDAS II) criteria. Children were followed up at 3, 6, and 12 months. The time required to perform the treatments was recorded, and a facial image scale (FIS) was applied to assess anxiety. Questions posed to caregivers were used to investigate adverse events and esthetic assessment. Results: After a year, the overall success rates of UCT, SDF, and ART were 61.6, 87.2, and 84.6%, respectively, with a statistically significant difference (p < 0.05). The time required to treat with SDF was significantly lower than that needed for ART and UCT (p < 0.01). Anxiety levels were significantly lower in the SDF group (p = 0.003). There was no difference in the percentage of adverse events and parental esthetic perception (p = 0.604). Conclusion: After 3 months, the arrest rates of ART, SDF, and UCT were similar. However, after 1 year, the arrest rate of UCT was significantly lower. Clinical significance: Silver diamine fluoride takes significantly less chair time and has success rates comparable to ART. Ultraconservative treatment has a short-term successful application. It was confirmed that there were no variations in adverse events between SDF, ART, and UCT. Clinical trial registration number: NCT05314660.