The relationship of the structures of the face to each other. It is assessed with the patient seated in an upright position looking straight ahead, with the head positioned so that the Frankfort plane is parallel to the floor and the teeth are in occlusion. It can be assessed in antero-posterior, vertical, and transverse planes. The antero-posterior plane can be assessed with the tips of the index and middle fingers placed in the concavities between the upper lip and the base of the nose and the lower lip and the chin; the skeletal pattern is class I if the index finger is horizontal during the examination (the mandible is 2–3mm posterior to the maxilla), class II when the index finger slopes down (the mandible is retruded relative to the maxilla), and class III when the index finger slopes upwards (the mandible is protruded relative to the maxilla).
The vertical plane is assessed from the side of the patient with the Frankfort plane parallel to the floor and the teeth in occlusion. In a patient with an average Frankfort mandibular plane angle (FMPA), a finger placed on the lower border of the mandible and one placed on the Frankfort plane will produce an angle in which the long axes of the fingers will cross at the occiput; with an increased FMPA the long axes will cross in front of the occiput, and with a reduced FMPA the long axes will cross behind the occiput.
The face height is divided into upper and lower parts. The lower face height (LFH) is of normal proportion when the distances from the glabella to the columella and the columella to the lower border of the chin are equal: the LFH is increased if the distance from the glabella to the columella is less than the distance from the columella to the lower border of the chin, and decreased if the distance from the glabella to the columella is greater than the distance from the columella to the lower border of the chin.
In the transverse plane, discrepancies may be either unilateral or bilateral depending on whether one or both sides respectively are affected. The transverse plane is in normal proportion if the width of the base of the nose is approximately the same as the inter-inner canthal width and the width of the mouth is the same as the distance between the medial sides of the irises.
Antero-posterior skeletal pattern
Skeletal pattern—vertical plane
Skeletal pattern—face height