Ectopically erupting mandibular first permanent molar: treatment of a case.

This case report presented a rare case of irreversible ectopic eruption of right mandibular first permanent molar in a 6-year-old boy. Distal root resorption of primary second molar was found during routine radiographic examination. Early treatment of ectopically erupting permanent first molar was considered in favor of preventing space loss. Using a modified Humphrey appliance as the correcting appliance, the ectopic eruption of permanent first molar had been successfully uprighted and retained.