I use Korean cephalometric norms to determine the position of the maxillary incisors. You have to consider inclination of maxillary incisors on the sagittal plane. Then, the center of maxillary central incisors should correspond to facial midline at the frontal position. Angulation of the maxillary incisors should be considered, which is associated with canting correction of the maxilla. In addition, display of the maxillary incisor (2 mm at rest) and gingiva (about 2 mm during smile) should be also considered.
From Dr. Sug-joon Ahn :
I use Korean cephalometric norms to determine the position of the maxillary incisors. You have to consider inclination of maxillary incisors on the sagittal plane. Then, the center of maxillary central incisors should correspond to facial midline at the frontal position. Angulation of the maxillary incisors should be considered, which is associated with canting correction of the maxilla. In addition, display of the maxillary incisor (2 mm at rest) and gingiva (about 2 mm during smile) should be also considered.