The Steiner analysis, developed and promoted by Cecil Steiner in the 1950s, can be considered the first of the modern cephalometric analyses for two reasons:1. It displayed measurements in a way that emphasized not just the individual measurements but their interrelationship into a pattern.2. It offered specific guides for use of cephalometric measurements in treatment planning. Elements of it remain useful today.
The Steiner numerical analysis, also suggests a series of measurements not only to diagnose the problem but it also provides guidelines for treatment planning based on the prediction of changes that take place as a result of growth and/or orthodontic therapy.
REFRENCE PLANE Steiner use SELLA to NASION(anterior cranial base) line as a reference plane for his analysisADVANTAGE According to Steiner S-N plane is a best reference plane because “If head deviate from true profile position thesetwo mid line points are minimally moved, even if thehead rotates in a cephalostat”
SKELETAL ANALYSIS Relate upper and lower jaw with skull and each other in antero posterior axis It consist of 5 Angular measurements
SNA ANGLE(82±2) A commonly used measurement (of the R. A. Riedel analysis) introduced by Steiner for assessment of the anteroposterior position of the maxilla with regards to the cranial base. The inferior posterior angle formed by the intersection of lines SN and NA is measured.
SNB angle(80±2) A measurement introduced by Steiner to evaluate the anteroposterior position of the mandible in relation to the cranial base (also part of the R. A. Riedel analysis). The inferior posterior angle formed by the intersection of lines NA and NB is measured.
Angle ANB (3 ± 1) The difference between SNA and SNB-the ANB angle- indicates the magnitude of the skeletal jaw discrepancy. This to Steiner was the measurement of real interest.
The magnitude of the ANB angle, however, is influenced by two factors other than the anteroposterior difference in jaw position.1. The vertical height of the face: As the vertical distance between nasion and points A and B increases, the ANB angle will decreases.2. If the antero- posterior position of nasion is abnormal, the size of the angle will be affected.
As SNA and SNB become larger and the jaws are more protrusive, even if their horizontal relationship is unchanged, it will be registered as a larger ANB angle. Because of this criticism different indicators of jaw discrepancy are now a days used.
Mandibular plane angle(32±4) A measurement introduced by C. C. Steiner for assessment of the steepness of the mandibular plane in relation to the cranial base. The anterior angle formed by the intersection of SN and GoGn is measured. W. B. Downs defined the mandibular plane angle as the anterior angle formed by the intersection of the Frankfort horizontal plane and a tangent to the lower border of the mandible and symphysis.
SN-OCCLUSAL PLANE ANGLE(17±4) According to Steiner occlusal plane is “Region of overlapping cusps of first premolar and molar” Determine the relation of teeth in occlusion with cranial basei. Increased in angle shows HIGH ANGLE CASE(SEKELETAL OPEN BITE)ii. Decreased in angle shows LOW ANGLE CASE(SKELETAL DEEP BITE)
DENTAL ANALYSIS Relates upper and lower incisors with each other and with their respective jaws 3 Angular measurements 2 Linear measurements 1 Ratio
UI-NA angle(22) Angle formed between the long axis of upper incisors and line drawn from nasion to pogonoin Describe axial inclination of upper incisors Determine relative angular relationship of upper incisor teetho Increased: Greater angulation of upper incisoro Decreased: Lesser angulation of upper incisor
UI-NA DISTANCE(4mm) Determine A-P position of upper incisor with relation to N-A line Distance measured from most anteriorly placed point on labial side of crown of upper incisor to N-A line Increased: Forwardly placed upper incisor Decreased: backwardly placed upper incisor
LI-NB angle(25) Angle formed between the long axis of lower incisors and line drawn from nasion to pogonoin Describe axial inclination of lower incisors Determine relative angular relationship of lower incisor teeth Increased: Greater angulation of lower incisor Decreased: Lesser angulation of lower incisor
LI-NB DISTANCE(4mm) Determine A-P position of lower incisor with relation to N-A line Distance measured from most anteriorly placed point on labial side of crown of lower incisor to N-A line Increased: Forwardly placed lower incisor Decreased: backwardly placed lower incisor
It is important to understand that it is possible for both upper and lower incisors to have normal angular(axial)relation with N-A line but have disturbance in A-P positioning(forward or backward placed incisors) Reverse relationship of A-P positioning and axial inclination or angular relation is also true.
INTERINCISAL ANGLE(135±5) Angle between long axes of upper and lower incisors. Average value: 135.4’ ( 130 to 150.5’) increased in class I bimaxillary protrusion
Holdaway ratio (LI-NB/Pg-NB) A measurement introduced by R. A. Holdaway to evaluate the relative prominence of the mandibular incisors, as compared to the size of the bony chin. It is calculated as the ratio of the linear distance from the labial surface of the mandibular central incisor to the NB line, over the linear distance of the chin to the same line.
If ratio is 2:1 it means that lower incisors are more proclined as compared to chin prominence. If discrepancy is 2mm=acceptable 3mm=less desirable 4mm=correction indicated
SOFT TISSUE ANALYSIS To assess balance and harmony of lower facial profile 2 linear measurements
S-line (Esthetic plane of Steiner) A line connecting the midpoint of the columella of the nose to the soft tissue pogonion. According to C. C. Steiner, the lips should fall on this line and any deviation shows prominence or flatness of the lips.