The FH plane was traditionally the logical choice of anthropologists as the Porion and infraorbital points (Po-Or Plane) were easily visible in dry skulls. Most cephalometric analyses adopted the FH plane for use in clinical cephalometry. Steiner highlighted difficulties in the accurate location of the Porion point and its relative variation, which could be observed in successive radiographs. The inability to locate the Porion point precisely affected the correct orientation of the FH plane.

On the contrary, the Sella and Nasion points were easily discernible on a lateral cephalogram and could be located with relatively higher accuracy. Moreover, the Sella and Nasion points had another advantage. These landmarks are located in the mid-sagittal plane of the head and moved minimally with any deviation of the head from the actual profile position. Hence, considering these observations, Steiner considered the SN plane a better, more accurate and predictable alternative to the FH plane.

Impressed by Richard Riedel, Steiner used the Sella-Nasion-A point (SNA) and Sella-Nasion-B point (SNB) angles to compare the position of the chin in the lower jaw with other structures of the cranium and the upper jaw. He used the A point-Nasion-B point (ANB) angle to compare the relative sagittal positioning between the maxilla and mandible.

Steiner suggested assessing the upper and lower incisors by comparing their relative position and angulations to the Nasion-A point (NA) and Nasion-B point (NB) planes as a guide.

He felt there were more direct reference planes on the lower jaw than the mandibular plane (MP), which is not a straight-line reference plane but a curved one and a highly variable one. Although he cited the above limitation, he continued to use the mandibular plane angle as a reference line for evaluating the position and inclination of the lower incisors.

Initially, even the distance of the upper molars (U6’s) was measured from the NA to be used as a reference at a later date to determine if any migration of molars (U6’s) had occurred over time.

Downs’ method of measuring the interincisal angle was retained as an additional method of appraising the inclination of these teeth to each other. Moreover, Downs’ philosophy of evaluating the occlusal plane to determine the position of teeth in occlusion to the face and skull was also retained.

Wylie and Johnson’s method of determining any malformation of the mandible was incorporated into the analysis. Riedel’s Gonion-Gnathion (Go-Gn) plane was used to represent the body of the mandible. According to Steiner, the mandibular plane can be drawn between the Gonion and Gnathion.

Skeletal analysis entails relating the upper and lower jaws to the skull and each other ( Fig. 24.1 and Table 24.1 ).

Skeletal variables used by Steiner.

Dental analysis focused on the sagittal liner and angular relations to each other and respective bases.

Dental variables used by Steiner.

He also incorporated skeletal variables SL and SE used by Wylie.

The maxillary and mandibular first molars are measured at their mesial contact points.

The soft tissue analysis provides a means of assessing the balance and harmony of the lower facial profile. A line is drawn on the soft tissue contour of the chin to the middle of the S formed by the lower border of the nose. This facial contour line is called Steiner’s S line.

In a well-balanced face, the lips should touch the line. The S line partially excludes the effect of nasal growth on the soft-tissue profile. Fig. 24.3 shows landmarks leading up to the S line and its relationship with the lips in an ideal profile.

‘S’ line is drawn from the soft tissue of the chin (pogonion) to the midpoint of the base of the nose (subnasale-pronasale line).

The plane used by Steiner to define the relationship between the lips and the S line, which is drawn from the soft tissue pogonion to the sub-nasale.

Source: Based on Steiner CC. Cephalometrics in clinical practice. Angle Orthod 1959; 29: 8–29 .

Steiner found that some acceptable dental compromises naturally occur in different skeletal maxillomandibular relations (i.e. ANB values). Based on his observations, he devised a novel method of orthodontic treatment planning for non-growing patients.

He concluded that correcting dentition might not be possible according to ideal norms in non-growing patients whose skeletal relations cannot be altered with growth modification.

The imperative here is to devise an acceptable compromise for the dentition that will mask the underlying skeletal deformity as much as possible. These calculations help define our orthodontic goal and assist in making the extraction or non-extraction decision in non-growing subjects. Fig. 24.4 depicts the norm values for an ANB of 2 degrees.

Steiner suggested using average measurements as norms.

The two lines on the graph represent the long axis of the upper and lower incisor. The ANB angle is written on top of the apex of the long axis of the upper incisor. In this figure, it is 2 degrees. The outside values are linear (4 mm) for the upper-incisor-to-NA and lower-incisor-to-NB distances. The inside values are angular (in degrees) for the upper incisor to NA and the lower incisor to NB in degrees.

Based on the data and concept of Steiner CC. Cephalometrics in clinical practice. Angle Orthod 1959; 29: 8–29 .

Any change in the ANB means objectives for the position of the lower incisor and upper incisor with respect to the NA and NB lines will not be ideal. According to Steiner, overall treatment planning is based on several parameters, including discrepancy and anchorage requirements, the estimated position of the Pogonion and average acceptable compromise based on clinical experience. He called them rough estimates; they may vary but are good starting points.