SELLA Mid point of Sella Turcica.

PORION Uppermost point of bony external auditory meatus.

POINT A Deepest midline point above upper incisors between anterior nasal spine and most anterior point on the alveolar process.

POINT B Deepest midline point in the concavity of bone below the lower incisors.

ORBITALE Lowest point on the infraorbital margin.

MENTON Lowest point on the shadow of the symphysis menti.

GONION Lowest, most posterior point on angle of mandible, obtained by bisecting angles formed by tangents to inferior and posterior borders of the mandible.

FRANKFORT HORIZONTAL PLANE

Represented by the line connecting lower border of orbit and Porion.

MANDIBULAR PLANE

Represented by line connecting Menton and Gonion.

SIGNIFICANT CEPHALOMETRIC VALUES:

SNA – relationship of maxilla to cranial base: 81 degrees.

SNB – relationship of mandible to cranial base: 78 degrees.

ANB – relationship of maxilla to mandible: 2 to 5 degrees.

– if ANB < 2, then sk. III relationship

– If ANB > 5, then sk. II relationship

FMPA (Frankfort-Mandibular plane angle) – is equivalent to the vertical jaw relationship: 27 degrees. [+/- 3]

– LOW FMPA means reduced lower 1/3 face height.

– HIGH FMPA means an increased lower 1/3 face height.

– Inclination of upper and lower incisors to Frankfort and Mandibular planes gives indication of any proclination or retroclination.

- Upper incisors to Frankfort plane: 109 degrees. [+/- 6]

- Lower incisors to Frankfort plane: 92 degrees [+/- 6]