This document provides an overview of Down's analysis for cephalometric evaluation. Down's analysis uses skeletal and dental landmarks on lateral cephalograms to measure facial form and the position of the mandible. Skeletal parameters include the facial angle, angle of convexity, A-B plane angle, mandibular plane angle, and Y-axis. Dental parameters include cant of the occlusal plane, inter-incisal angle, incisor occlusal plane angle, incisor mandibular plane angle, and upper incisor to A-Pog line. Reference planes used in the analysis include the F-H plane, occlusal plane, and mandibular plane. The analysis provides information

1. ARUNESH VERMA
DOWN’S ANALYSIS

2. CONTENTS
• INTRODUCTION
• CEPHALOMETRIC LANDMARKS
• REFERENCE PLANE
• DOWN’S ANALYSIS
• Skeletal analysis
• Dental analysis

3. INTRODUCTION
• Origin : “cephalo” means head and “metric” is measurement.
• The science of study and analysis of cephalogram is called
cephalometry.
• In 1931 Herbert Hofrath in Germany and Broadbent in the United
States simultaneously but separately published articles in which they
had refined the technique of cephalogram.

4. Uses of cephalometry
• For aid in treatment planning for orthodontics .
• For differentiating skeletal from dental malocclusion.
• For assessment of treatment related changes.
• For planning of orthognathic surgery.
• For assessing growth status of child.

5. TYPES OF CEPHALOGRAM
• Lateral cephalogram
• Frontal cephalogram
TECHNIQUE

6. CEPHALOMETRIC LANDMARKS
• Anatomical landmarks
• Derived landmarks
• Unilateral landmarks
• Nasion
• Sella
• Basion
• Articulare
• Anterior nasal spine
• Posterior nasal spine
• Subspinale
• Supramentale (point B)
• Pogonion
• Gnathion
• Menton

7. • Bilateral landmarks
• Gonion
• Orbitale
• Porion

8. DOWN’S ANALYSIS
• William B Down introduced a method
of recording the skeletal and dental
pattern to measure facial form on a
cephalogram in 1948.
• According to Down “balance of face
is determined by position of
mandible”.

9. Reference plane used in Down’s analysis
F-H PLANE
OCCLUSAL PLANE
MANDIBULAR PLANE

10. Skeletal parameters
1.Facial Angle
• Mean value 87.8°
• Range 82° to 95°
• This angle gives us an indication of the
anteroposterior positioning of mandible in
relation to Upper face.
• In class 3 Case : angle will increases.
• In class 2case :angle will decreases.

11. 2. Angle of convexity
• Mean value 0°
• Range -8.5° to 10°
• Measure the placement of maxillary
basal arch relative to total facial profile
• Positive angle-convex profile (class2)
• Negative angle - concave profile (
class3)

12. 3. A-B plane angle
• Formed by line joining Point A to Point B and
line joining N to Pg.
• It indicates the maxillomandibular relationship in
relation to facial plane.
• Mean value -4.6°
• Range 0° to -9°
• Large negative angle - clsss 2
• Positive angle- class 3

13. 4. Mandibular plane angle
• Mean value 21.9°
• Range 17° to 28°
• An increased mandibular plane
angle is suggestive of a vertical
growth pattern
• Decreased angle - horizontal
growth pattern

14. 5. Y axis( Growth Axis)
• Formed by the line joining Sella to Gnathion
and F-H plane.
• Mean value 59.4°
• Range 53° to 66°
• If angle increases = indicates greater vertical
growth of mandible
• If angle degrees = it indicates greater
horizontal growth of mandible

15. Dental parameters
1. Cant of occlusal plane
• Angle between occlusal plane and F- H plane
• Mean value 9.3°
• Range 1.5° to 14°
• And it gives a measure of the slope of the
occlusal plane.
• Increase angle shows vertical growth pattern.
• Decrease angle shows horizontal growth pattern.

16. 2. Inter incisal angle
• Line passing through incisal edge and apex of root of
maxillary and mandibular incisor
• Mean 135.4°
• Range 130 to 150°
• Small angle - Proclined incisors
• Large angle - Retroclined incisors

17. 3. Incisor occlusal plane angle
• Mean value 14.5°
• Range 3.5° to 20°
• An increase in this angle suggest
increase lower incisors proclination.

18. 4. Incisor mandibular plane angle
• Mean value 1.4°
• Range -8.5° to 7°
• An increase in this angle indicates
lower incisors proclination.

19. 5. Upper Incisor to A Pog line
• Linear measurement between the incisal
edge of maxillary central incisor and line
joining point A and pogonion
• Mean value: 2.7 mm
• Range: -1.0 to +5 mm
• The upper incisor proclined, the
measurement will be more.

20. • Contemporary Orthodontics by William R. Proffit
• Orthodontics-Principles And Practice by Thomas
M. Graber
• Textbook of Orthodontics:Gurkeerat Singh
References