Ectopic eruption of the second permanent molar is a tooth replacement disorder during adolescence. If not treated in time, it can cause hard tissue of the adjacent first molar resorption, early tooth loss, decreased chewing efficiency, and other serious malocclusions. Timely detection and treatment of ectopic eruption of the second permanent molar are of great significance in preventing malocclusions in adolescents and establishing normal occlusion relationships. However, current case reports on the ectopic eruption of the mandibular second molar are relatively rare and are mostly concentrated on surgical and orthodontic treatments, and long-term follow-up is lacking. This paper reports a case in which brass wire ligation was used to treat ectopic eruption of the mandibular second permanent molar, allowing the permanent teeth to erupt smoothly and establish a normal occlusion. The patient was observed for five years after the operation. The occlusion was stable, and the tooth root development, pulp vitality, and periodontal conditions were normal. This paper provides a clinical approach that is short in treatment duration, simple, and minimally invasive for young mandibular second permanent molars with moderate mesial inclination and partial eruption. This method is of importance in helping children establish physiological occlusion.
