Fused teeth, with all its lower prevalence, produce many problems in orthodontic treatment because of their altered form, large root, and unbalance of teeth numbers between upper and lower jaws. The authors have reviewed on its etiology, differential diagnosis, prevalence, clinical features and complications. Orthodontic treatment cases of 2 sisters with malocclusion including fused teeth were presented, in which asymmetrical extractions were performed and edgewise appliances were utilized.