Which is the most stable and most often used plane for the superimposition of lateral cephalograms in studying the growth of a child?
Superimposition on SN
Brodie used sella–nasion line registered at ‘S’ as a method of orientation and superimposition of cephalograms. This is the most popular and practical method used for orientation and superimposition of lateral cephalograms. The ‘Sella’ was considered a stable point for it distinguishes cranial base from the face, presuming that the major cranial base growth is completed by 7 years of age. Two or more hand-drawn tracings or computerised images are superimposed on SN plane registration at ‘S’. Resultant changes are seen in the location of teeth and structures consequent to growth or orthodontic treatment including growth. Since most patients are beyond 7 years of age, we commonly use SN plane for orientation to evaluate changes in growth or by treatment in the face and dental structures.
Ref: Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities, 3e, Om P. Kharbanda pdf no 1192
Frankfort plane
S-N Plane
Mandibular plane
Occlusal plane