A point (A) — this is the point of deepest concavity on the anterior profile of the maxilla. It is also called subspinale. This point is taken to represent the anterior limit of the maxilla and is often tricky to locate accurately. However, tracing the outline of the root of the upper central incisor first and shielding all extraneous light often aids identification. The A point is located on alveolar bone and is liable to changes in position with tooth movement and growth.

Anterior nasal spine (ANS) — this is the tip of the anterior process of the maxilla and is situated at the lower margin of the nasal aperture.

B point (B) — the point of deepest concavity on the anterior surface of the mandibular symphysis. The B point is also sited on alveolar bone and can alter with tooth movement and growth.

Gonion (Go) — the most posterior inferior point on the angle of the symphysis. This point can be ‘guesstimated’, or determined more accurately by bisecting the angle formed by the tangents from the posterior border of the ramus and the inferior border of the mandible .

Menton (Me) — the lowest point on the mandibular symphysis.

Nasion (N) — the most anterior point on the frontonasal suture. When difficulty is experienced locating nasion, the point of deepest concavity at the intersection of the frontal and nasal bones can be used instead.

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