Steiner Analysis by Dr Nay Aung PhD

1. Steiner analysis in Orthodontics
Nay Aung, BDS PhD
15-7-2022

2. Cephalometric landmarks used in Downs Analysis

3. Skeletal, Dental & Soft tissues Measurements
Interincisal angle

4. Describe SNA (Sella-Nasion-A point)
Mean: 82° ± 3°
Maxilla to Cranial Base
Determine whether the maxilla is positioned anterior
or posteriorly to the cranial base
SNA (interpretation)
< normal range (79°) → skeletal maxillary retrusion
> normal range (85°) → skeletal maxillary protrusion
Greater angle indicates relative forward positioning of
maxilla & lesser angle indicates recessive location of
maxilla.

5. Describe SNB (Sella-Nasion-B point)
Mean: 79° ± 3°
Mandible to Cranial Base
B point is the most anterior measure point of the
mandibular apical base.
This angle expresses the horizontal position of the
mandible relative to the cranial base using B-point as a
cephalometric landmark.
Determine whether the mandible is positioned anterior
or posteriorly to the cranial base
SNB (interpretation)
< normal range (76°) → retrognathic mandible
> normal range (82°) → prognathic mandible

6. Describe ANB angle (A point – Nasion – B point)
Average: 3° ± 2
Maxilla to Mandible
The ANB angle measures the relative position of the
maxilla to mandible.
The ANB angle can be measured or calculated from the
formula: ANB = SNA – SNB.
A positive ANB angle indicates that the maxilla is
positioned anteriorly relatively to the mandible (Class I or
Class II malocclusion cases).
A negative ANB angle indicates that the maxilla is
positioned posteriorly relative to the mandible (Class III
malocclusion cases).
The normal range is 1° - 5°.
>5° indicates a Class II skeletal jaw relationship, protrusive
maxilla or retrognathic mandible.
<1° indicates a Class III skeletal jaw relationship, deficient
maxilla or prognathic mandible.

7. Occlusal plane to S-N
Occlusal plane drawn through the region of
overlapping cusps of 1st premolars & 1st
molars.
Angle of occlusal plane & S-N is measured.
Mean reading is 14°.
The angle is increased in long face or
vertically growing individuals and also
skeletal open bite cases.
It may be decreased in horizontally growing
individuals or cases with a skeletal deep bite.

8. S-N to Mandibular Plane (Go-Gn) Angle
Drawn between gonion & gnathion
The mandibular plane angle is formed by joining
the mandibular plane to the anterior cranial base
(S-N plane).
Mean reading is 32°.
Excessively high or low mandibular plane angles
suggest unfavorable growth pattern in
individuals.

9. U1 – NA
Angle between upper incisor to NA line, Mean angle: 22°
Distance from upper incisor to NA line, Mean distance: 4 mm
Angle is formed by intersection of long axis of
upper central incisors & line joining N-A line.
22° angle & 4mm distance is ideal.
> 22° may be seen in Class II div 1 case.
< 22° may be seen in Class II div 2 case.
> 4mm is common in Class I bimaxillary
protrusion or in Class II div 1 relationship.
< 4mm common in Class II div 2.
22 degrees
4 mm

10. Incisor angle at 22 degrees but
(a) Retro positioned (-2mm)
(b) Ideally positioned (4mm)
(c) Positioned too far forward (8mm)
Show inadequacy of relating incisor
tip to millimeter reading only.
All three teeth are 4 mm from the N-A
line but angled differently

11. L1 – NB
Angle between lower incisor to NB line, Mean angle: 25°
Distance from lower incisor to NB line, Mean distance: 4 mm
Angle is formed by intersection of long axis of
lower central incisors & line joining N-B line.
25° angle & 4mm distance is ideal.
> 25° may be seen in Class II div 1 case.
< 25° common in Class II div 2 or Class III
25 degrees
4 mm

12. Upper incisor to Lower incisor angle (Interincisal angle)
U1 – L1
Mean value of 130° - 131°
Reduced angle suggests Class II div 1.
Larger angle indicates Class II div 2.

13. L1 – Chin (mm)
Holdaway Ratio
This measurement is introduced to evaluate the
relative prominence of the mandibular incisors,
as compared to the size of the bony chin.
According to Holdaway distance between labial
surface of mandibular incisor to N-B line and the
distance from pogonion to N-B line should be
equal (i.e. 4mm)
Discrepancy
If discrepancy is
2mm = acceptable
3mm = Less desirable
4mm exceeds = correction indicated

14. The facial contour line called ‘S’ line of Steiner.
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.
In a well-balanced face, the lips should touch the
line.
If the lips are located beyond this line, lips are
believed to be protrusive & interpreted as convex
profile.
If the lips are behind this line, it is said to be
retrusive with a concave profile.
Soft tissue analysis
‘S’ line

15. Thank you so much for your kind attention.

16. What is E line?
In Ricketts analysis, E line or esthetic line runs
from the tip of the nose to the soft tissue
pogonion.
What is S line?
S line extending from soft tissue contour of the
chin to the middle of an ‘S’ formed by the lower
border of the nose.
Soft tissue analysis
‘E’ line