A 15-year-old female presented with the chief complaint of crowding. Extraoral examination revealed little facial asymmetry, which was related with mandibular deviation caused by constriction of the maxilla. Upon intraoral examination, Class III molar and Class II canine relationships were seen on the right side, and Class III molar and Class III canine relationships were seen on the left side. A morphological lower midline shift was detected (4 mm to the right). After the start of treatment with rapid maxillary expansion, miniscrews were inserted into the buccal shelf and canine-premolar areas in order to solve the morphological deviation without extractions. Because there was a need to shift the lower midline to the right side, miniscrews were inserted into the left buccal shelf at the right canine-premolar area. The miniscrews were placed vertically so that the angle between the long axes of the teeth and the long axes of the screws were approximately 20 degrees. Acceptable correction of the midline deviation lasted for four months. At the end of the treatment, a good occlusal relationship was obtained.

Keywords: Dento-alveolar asymmetries, diagnosis, midline deviation, treatment strategies, mini-screw