This document summarizes Dr. Pratik Yadav's journal club presentation on Downs WB Analysis of the dento-facial profile. It discusses the 10 parameters in Downs analysis, which includes 5 skeletal and 5 dental measurements. The parameters are measured based on landmarks and reference planes on lateral cephalograms. Downs analysis is one of the most commonly used cephalometric analyses originally developed based on Caucasian patients with excellent occlusion.

1. Department of Orthodontics
Journal club on
Downs WB Analysis of the dento-facial profile .
Angle orthod 1956;26:191
Presented by-
Dr. Pratik Yadav
PG 1st Year

2. Analysis
• Skeletal and dental relationships are
measured by reference to a landmark or plane
drawn on the lateral cephalogram.
• These can be either ‘ hand traced’ or more
commonly now digitised using specialized
cephalometric software (e.g. QuickCeph
(Mac), Dolphin Imaging (Windows)

3. • The first published
comprehensive analysis was by
Downs in 1948
• It is one of the most frequently
used cephalometric analysis.
• Downs analysis consists of
– Ten parameters of which
 five are skeletal
 five are dental
William Downs
Down’s Analysis

4. • These ten variables were obtained from
comparison and correlation of 20 Caucasian
patients,10 males and 10 females, having
clinically excellent occlusion and were
untreated by orthodontics means
• Patients age is 12-17 years

5. Reference Plane
• ACCORDING TO DOWN
“Balance of face is determined by position of
mandible”.
• In order to find this balance DOWNS use
FRANKFURT HORIZONTAL PLANE as a reference
plane i.e. line from anatomic porion to orbitale.
• Downs elected to use this plane as a reference
base from which he determine the degree of
retrognathism, orthognathism, or prognathism

6. Skeletal Parameters
Facial angle;
• it is the inside inferior angle formed by
intersection of nasion-pogonion plane
andF.H. plane.
• average value; 87.8’ ( 82 –95’)
Significance;
• indication of antero- posterior positioning
of mandible in relation to upper face .
Interpretation
• increased in skeletal class III with
prominent chin
• decreased in skeletal class II

7. Angle of Connvexity
• Nasion-point A to point A-
pogonion.
• Average value; 0⁰(-8.5 to 10⁰)
Significance;
• A positive angle suggest a
prominent maxillary denture base
in relation to mandible.
• Negative angle is indicative of
prognathic profile

8. Mandibular plane angle
• Intersection of mandibular plane
with F.H Plane.
• Average value; 21.9⁰ ( 17 to 28⁰)
• Mandibular plane according to
DOWNS is “tangent to gonial angle
and lowest point of symphsis
• High MP angle occur in both
retrusive & protrusive face and are
suggestive of unfavourable
hyperdivergent face

9. Y-Axis
• Sella gnathion to F.H. plane.
• Average value; 59⁰ ( 53 to 66⁰)
Interpretation
• Increased in class II facial patterns.
and also Indicates vertical growth
pattern of mandible
• Decreased in class III facial patterns
and also indicate horizontal
patterns of mandible growth

10. A-B plane angle
• point A–point B to nasion–pogonion.
• Average value; -4.6⁰ (-9 to 0⁰)
Significance;
• indicative of maxillo mandibular
relationship in relation to facial plane.
• Negative since point B is positioned
behind point A.
• Positive in class III malocclusion or
class I malocclusion with mandible
prominence

11. Dental parameters
Cant of occlusal plane;
• OCCLUSAL PLANE TO F.H. Plane
• Average value; 9.3⁰ ( 1.5 to 14⁰)
• Gives a measure of slope of
occlusal plane relative to F.H.
Plane .
• Increase in class II facial paterns
• Decreases in long rami

12. Inter incisal angle; (135.4±5.8)
Angle between long axes of upper
and lower incisors.
• Average value: 135.4⁰ ( 130 to
150.5⁰)
• decreased in class I bimaxillary
protrusion & class II division 1
• Increases in class II division 2

13. Incisor occlusal plane angle;
• This is the inside inferior angle formed
by the intersection between the long
axis of lover central incisor and the
occlusal plane and is read as a plus or
minus deviation from a right angle
• Average value: 14.5⁰ ( 3.5 to 20⁰)
• An increase in this angle is suggestive of
increased lower incisor proclination
Incisor mandibular plane angle:
• This angel is formed by intersection of
the long axis of the lower incisor and the
mandibular plane.
• Average value: 1.4⁰(-8.2 to 7⁰)
• An increase in this angle is suggestive of
increased lower incisor proclination

14. Upper incisor to A-pog line (2.7+-1.8)
• This is a linear measurement
between the incisal edge of the
maxillary central incisor and the
line joining point A to pogonion.
• This distance is on an average 2.7
mm(range-1 to 5mm)
• The measurement is more in
patients presenting with upper
incisor proclination

15. Cephalomtric polygon
• Because of the difficulty of
developing a suitable mental
picture of a sizable table of
figures varhirs & Adams developd
a polygon that express the
reading graphically
• By reversing the maximum and
minimum limits , it was possible
to indicate class II on the left side
& class III on the right