Geometrical interpretation for abnormal facial behaviour with possible correction of angle S‐N‐A and S‐N‐B

Abstract

The orientation of the sella nasion (SN) line in lateral skull radiographs is important for accurate assessment of antero-posterior and vertical facial relationship. Lateral skull radiographs of a random sample were traced and digitized to produce a mean shape template of the sample, with the craniofacial centroid line (CFC) used as a base for superimposition of the sample. A geometrical triangle was formed using the sella nasion line, craniofacial centroid line and the mandibular plane as the sides of the triangle. Simple geometric calculations were done to re-orient both the mandibular plane and sella nasion line in cases with balanced clinical profiles, while the S-N-A and S-N-B measurements indicate otherwise.

Reliability of a Centroid method to estimate head position in cephalometric diagnosis

“…Centroid is a mathematical point that describes the geometric center of a polygon or also described in physics as the center of gravity of an object's shape. It has been introduced fifty years ago and its use in cephalometric research has been reported by a few investigators [14][15][16][17][18]. The explanation of why use Centroid in cephalometric research lies in that, Centroid represents the least variable, therefore, the most stable point of any area or volume, and it is not affected by increasing in size and/or changing in shape [17].…”