Relevance. The average time of orthodontic treatment in children is often several years. However, the final mineralization of erupted permanent teeth occurs during this period. The skills developed at this age rarely guarantee a high level of individual oral hygiene. Thus, modern removable appliances (aligners) in children with mixed dentition have several advantages. Remineralization therapy performed simultaneously with orthodontic treatment is one of the essential advantages of using aligners.Purpose. The study aimed to conduct a comparative clinical assessment of changes in the enamel acid resistance and remineralization effectiveness in patients undergoing orthodontic treatment with removable appliances (aligners). Material and methods. Orthodontic follow-up observation involved 59 patients aged 8 to 14 years for six months. They made up three observation groups. The first (control) group included 17 people who visited the orthodontist for a check-up. The second (21 people) and third (21 people) groups comprised patients undergoing orthodontic treatment with aligners. Patients of the second group added ASEPTA TEENS paste to their daily oral care complex. Patients of the third group used ASEPTA remineralizing gel for children besides ASEPTA TEENS paste. The TER test assessed enamel acid resistance, and remineralization effectiveness was determined throughout the study.Results. The comparative analysis revealed that the enamel acid resistance increased in patients of the third group who had followed our recommended scheme of oral care product use with a complex of ASEPTA TEENS paste and ASEPTA remineralizing gel for children. The group showed a remineralization effectiveness of 39.5% after six months. Patients of the second group who used ASEPTA TEENS paste without gel applications for six months also showed an increase in remineralization effectiveness of 19.5% compared to the baseline.Conclusion. The results obtained during the study allow us to recommend ASEPTA remineralizing gel for children for oral care during orthodontic treatment with removable appliances (aligners) in patients with mixed dentition. Removable aligners allow you to combine orthodontic treatment and the preventive use of mineralizing agents for forming strong enamel and protecting it from demineralization.