Table 2 Measurement indexes and annotations of the vertical orientation of the jaw

MP-SN(°)

The intersection angle of the mandibular plane MP (the line tangent to the lower edge of the mandibular angle through Me) and the plane of the anterior skull base (the line connecting S and N)

FH-MP(°)

The intersection angle between the FH plane and the MP plane

Y-axis angle(°)

The lower front corner where the line connecting S and Gn (SGn) intersects with FH

Po-NB(mm)

The vertical distance from Po to N-B line

SN-FH(°)

N point variation comparison value, the angle between the SN plane and the FH plane