Fig. 2

Calculation of facial asymmetry index on orbitale (Or). The formula was designed to show the degree of facial asymmetry by using the difference between the distances from the reference point to bilateral measurement landmarks. If both orbitales were on 3 dimensionally symmetric positions to the 3 reference landmarks (nasion, sella, MidZ), the value of facial asymmetry index was 0. As the asymmetry of both orbitales increased, the facial asymmetry index on orbitale increased. The formula was designed so that the right deviation had a negative value while the left deviation had a positive value. The facial asymmetry indices were calculated on the 5 bilateral landmarks—orbitale (Or), condylion (Co), gonion (Go), upper 1st molar (U6), lower 1st molar (L6)