Illustration of 15 commonly used measurement items.
U1-NA
1. SNA: the angle between the sella-nasion plane and the nasion-subspinale plane; 2. SNB: the angle between sella-nasion plane and the nasion-supramental plane; 3. ANB: the angle between the nasion-subspinale plane and the nasion-supramental plane; 4. NP-FH: the posterior-inferior angle between the facial plane and the Frankfort horizontal plane; 5. NA-PA: the angle between the nasion-subspinale plane and the pogonion-subspinale plane; 6. U1-NA (mm): the distance from the upper central incisor tip to the nasion-subspinale plane; 7. U1-NA: the angle between the upper central incisor and the nasion-subspinale plane; 8. L1-NB (mm): the distance from the lower central incisor tip to the nasion-supramental plane; 9. L1-NB: the angle between the lower central incisor and the nasion-supramental plane; 10. U1-L1: the angle between the upper central incisor and the lower central incisor; 11.Y axis angle: the anterior-inferior angle between the Frankfort horizontal plane and the sella-pogonion plane; 12. Po-NB (mm): the distance from the pogonion point to the nasion-supramental plane; 13. FMA: the angle between the Frankfort horizontal plane and the mandibular plane; 14. FMIA: the angle between the Frankfort horizontal plane and the long axis of the lower central incisor; 15. IMPA: the angle between the long axis of the lower central incisor and the mandibular plane. The profile tracing was completed with the Uceph software (Uceph, Chengdu, China).