CEPHALOMETRICS FOR ORTHOGNATHIC SURGERY

1. PRESENTED BY –
Dr. Firdosh Rozy

2. CONTENTS :
Background history and philosophy
The Analysis
References
HARD TISSUE ANALYSIS
SOFT TISSUE ANALYSIS

3. CHARLESJ.BURSTONE
 Charles J. Burstone (April 4, 1928
February 11, 2015)
 He was an American orthodontist who
was notable for his contributions to
biomechanics and force-systems in the
field of orthodontics.
 He wrote more than 200 articles in
scientific fields.

4. HarryL.Legan
Dr. Legan is an internationally
recognized orthodontic expert
on diagnosis and treatment
planning, obstructive sleep
apnea, orthognathic surgery,
biomechanics, and distraction
osteogenesis.

5.  Charles J. Burstone et al (1978, 1980) developed an analysis
specially designed for patients requiring Orthognathic surgery.
 They used the landmarks and the measurements that can be altered by
common surgical procedures.
 This analysis is also called as Cephalometrics for Orthognathic
Surgery (COGS)
Burstone and Legan in their 1980 proposed a paper for constructed
horizontal line. This line is drawn through nasion at an angle of 7
degrees to the SN line.
They developed this line because of reliability issues with the SN
line when one can easily place the Sella point up/down which can
change the cephalometric measurements

6. Horizontal plane 7º to SN plane
Burstone CJ et al Cephalometrics for orthognathic
surgery, J Oral Surg . 1978 Apr ; 36(4):269-77.
HORIZONTAL PLANE SUBSTITUTED S-N
PLANE:

7. ANALYSIS
HARD TISSUE SOFT TISSUE

8. HARD TISSUE
ANALYSIS
CRANIAL
BASE
HORIZONTAL
SKELETAL
PROFILE
VERTICAL
SKELETAL
VERTICAL DENTALMAXILLA &
MANDIBLE
DENTAL

9. 1.

10.  Ar-Ptm is the distance between Ar
and Ptm which is measured parallel to
HP
 Standard Value
MALES 37.1 ± 2.8 mm
FEMALES 32.8 ± 1.9 mm
 Ar-Ptm indicates the position of
mandible in relation to posterior
surface of maxilla

11.  Ptm-N is the distance between Ptm and
N which is measured parallel to HP
 Standard Value
MALES - 52.8 ± 4.1 mm
FEMALES - 50.9 ± 3 mm
 Ptm-N indicates the position of
posterior border of maxilla in relation to
Nasion .
If this value
increases it indicates more posterior
position of maxilla in relation to N and
if it decreases it indicates anterior
position of maxilla in relation to N.

12.  A few simple measurements should be made on the skeletal
profile to assess the amount of discrepancy in anteroposterior
direction.
 It is called as Horizontal Skeletal Profile analysis because all the
measurements in this set of analysis are made parallel to HP
2.

13. ANGLE OF SKELETAL CONVEXITY
It is the angle formed between N-A and A-Pg
 Standard Value
MALES 3.9⁰ ± 6.4⁰
FEMALES 2.6⁰ ± 5.1⁰
 A positive angle indicates convex profile while
negative angle indicates concave profile

14. A perpendicular to HP is dropped from
N (N perpendicular) and horizontal
distance parallel to HP is measured from
point A
Standard Value
☺MALES 0 ± 3.7 mm
☺FEMALES -2 ±3.7 mm
This measurement describes the position
of apical base of maxilla in relation to
nasion

15. It is obtained by measuring the
distance between Point B and Nasion
perpendicular (N perpendicular)
Standard Value
MALES -5.3 ± 6.7 mm
FEMALES -6.9± 4.3 mm
This measurement describes the
position of apical base of mandible in
relation to nasion

16. It is obtained by measuring the
distance between Pogonion and Nasion
perpendicular (N perpendicular to HP)
Standard Value
MALES -4.3 ± 8.5 mm
FEMALES -6.5 ± 5.1 mm
This measurement describes the
position of mandibular chin in relation
to nasion

17. 3.
A Vertical skeletal discrepancy may reflect an anterior,
posterior or complex dysplasia of the face .

18. Distance between N and ANS measured
perpendicular to HP gives us the Middle
third facial height.
Standard Value
MALES 54.7 ± 3.2 mm
FEMALES 50 ± 2.4 mm
Any increase or decrease in this value
indicates increased or decreased middle
third facial height respectively

19. Distance between ANS and Gn
measured perpendicular to HP gives us the
Lower third facial height.
Standard Value
MALES 68.6 ± 3.8 mm
FEMALES 61.3 ± 3.3 mm
 Any increase or decrease in this value
indicates increased or decreased lower
third facial height respectively

20. Distance between PNS and HP
gives us the posterior maxillary
height.
Standard Value
MALES 53.9 ± 1.7 mm
FEMALES 50.6 ± 2.2 mm
Any increase or decrease in this
value indicates increased or
decreased posterior maxillary
height respectively

21. Mandibular plane angle in relation to
Horizontal plane intersecting at Gn gives
us posterior divergence of mandible .
Standard Value
MALES 23⁰ ± 5.9⁰
FEMALES 24.2⁰ ± 5⁰
Any increase or decrease in value
suggests increased or decreased posterior
facial divergence

22. 4.

23. To obtain upper anterior dental height,
perpendicular distance from incisal edge of
upper incisor to palatal plane is measured
 Standard Value
MALES 30.5 + 2.1 mm
FEMALES 27.5 + 1.7 mm
 Any increase or decrease in this value
indicates increased or decreased upper
anterior dental height respectively

24. To obtain lower anterior dental height,
perpendicular distance between incisal
edge of lower incisor to MP is measured
 Standard Value
MALES 45 ± 2.1 mm
FEMALES 40.8 ± 1.8 mm
Any increase or decrease in this value
indicates increased or decreased lower
anterior dental height respectively

25. To measure upper posterior dental height
a perpendicular line is dropped from the
tip of mesiobuccal cusp of upper first
molar to palatal plane
Standard Value
MALES 26.2 ± 2.0 mm
FEMALES 23 ± 1.3 mm
Any increase or decrease in this value
indicates increased or decreased upper
posterior dental height respectively

26. To measure lower posterior dental height
a perpendicular line is dropped from the
mesiobuccal cusp of lower first molar to
MP
Standard Value
MALES 35.8 + 2.6 mm
FEMALES 32.1 + 1.9 mm
Any increase or decrease in this value
indicates increased or decreased lower
posterior dental height respectively.

27. 5.

28. ANS and PNS are projected on HP
Distance between these two points on
HP gives us total effective maxillary
length
Standard Value
MALES 57.7 + 2.5 mm
FEMALES 52.6 + 3.5 mm

29. Mandibular ramal length is the linear
distance between Articulare and Gonion.
Standard Value
MALES 52 ± 4.2 mm
FEMALES 46.8 ± 2.5 mm
Variation in Ramal length can be a
causative factor for skeletal open bite or
deep bite

30. Mandibular body length is the linear
distance between Gonion and Pogonion
 Standard Value
MALES 83.7 ± 4.6 mm
FEMALES 74.3 ± 5.8 mm
increase in length denotes skeletal class III
decrease in length signifies skeletal class II

31. This measurement describes the prominence
of chin in relation to mandibular apical base.
It is obtained by measuring the distance b/w
point B and a perpendicular to mandibular plane
passing through Pg.
Standard Value
MALES 8.9 ± 1.7 mm
FEMALES 7.2 ± 1.9 mm

32. This measurment represents the
relationship between the ramal plane and
mandibular plane
Standard Value
MALES 119.1 ⁰ + 6.5 ⁰
FEMALES 112⁰ + 6.9 ⁰
Gonial angle also contributes to skeletal
open bite or deep bite.

33. 6.

34. OP is Occlusal Plane constructed from
buccal groove of first permanent molars
through a point 1 mm apical to the incisal
edge of the upper central incisors.
When incisors are not in proper overbite
relation, two OP are to be constructed,
upper and lower and mean to be taken.
Standard Value
MALES 6.2 ⁰ ± 5.1 ⁰
FEMALES 7.1 ⁰ ± 2.5 ⁰
An increased OP-HP angle may be associated
with skeletal open bite, lip incompetence and increased anterior facial height
An decreased OP-HP angle may be associated with skeletal deep bite,
decreased anterior facial height and lip redundancy.

35. This distance is obtained by measuring
the distance between projection of Point A
and Point B on OP .
Standard Value
MALES - 1.1 + 2.0 mm
FEMALES - 0.4 + 2.5 mm
 This distance gives us relationship
between maxillary and mandibular apical
bases in relation to OP.

36. This angle is constructed by intersecting
a line passing through the tip of insical
edge through the root tip of upper incisor
and NF line.
 Standard Value
MALES 110 ± 4.70
FEMALES 112.50 ± 5.30
This angle gives us the inclination of
upper incisors in relation to palatal plane.

37. This angle is constructed by intersecting
a line joining the incisal edge of lower
incisor passing through its root tip and MP.
 Standard Value
MALES 95.9⁰ ± 5.2 ⁰
FEMALES 95.9⁰ ± 5.7 ⁰
 This angle gives inclination of lower
incisors in relation to MP

38. SOFT
TISSUE
FACIAL
FORM
LIP
POSITION
& FORM

39. Glabella (G)
The most prominent point in the
midsagittal plane of the forehead.

40. Columella point (Cm)
The most anterior point on the
columella (nasal septum) of the
nose.

41. Subnasale (Sn)
The point at which the columella
merges with the upper lip in the
midsagittal plane.

42. Labrale superius (Ls)
A point indicating the
mucocutaneous border of the upper
lip

43. Stomion superius (Stms)
The lower most point on the
vermilion border of the upper lip.

44. Stomion inferius (Stm i )
The upper most point on the
vermilion border of the lower lip.

45. Labrale inferius (Li)
A point indicating the
mucocutaneous border of the lower
lip.

46. Soft tissue Pogonion (Pog’)
The most prominent or anterior
point on the chin in midsagittal
plane.

47. Soft tissue Menton (Me’)
lowest point on the contour of the
soft tissue chin.

48. Cervical Point (C)
The innermost point between the
submental area and neck.

49. Soft tissue Gnathion (Gn’)
The constructed midpoint between
soft tissue pogonion and soft tissue
menton.

50. Facial
Convexity
Angle
G-Sn-Pg
G-Sn G-Pg G-Sn/Sn-
M
Sn-Gn-C
Angle
Sn-Gn/C-
Gn
FACIAL
FORM

51. Facial Convexity Angle
G-Sn-Pg
Drop a line form Glabella ‘G’ to
Subnasale ‘Sn’ and a line Sn to soft tissue
pogonion ‘Pg’.
Mean value : 12 ± 4⁰
increased +ve value - convex profile
 Increased -ve value - concave profile
(class3 skeletal and dental relationship)

52. MAXILLARY PROGNATHISM
G-Sn
Drop line perpendicular to horizontal
plane from Glabella. Measure the distance
from perpendicular line to Sn ( parallel to
HP)
 Mean value: 6 ± 3 mm
Describes the amount of maxillary
excess/deficiency in anteroposterior
dimension.
 +ve=maxillary prognathism.
 –ve=maxillary retrognathism.

53. MANDIBULAR PROGNATHISM
G-Pg
Drop a perpendicular line to HP from
Glabella. Measure the position of the
pogonion from this line parallel to HP.
 Mean value: 0 +/- 4
Increased –ve value indicate mandible is
retrognathic.

54. VERTICAL HEIGHT RATIO
G-Sn/Sn-M
Drop a perpendicular line to HP from
Glabella, to this line drop a perpendicular
line to Sn and M. Measure the distance
from G-Sn and Sn – Me ( all perpendicular
to HP )
 The ratio of middle 3rd to lower 3rd
facial height measured perpendicular to
HP.
 Ratio less than 1 = denotes
disproportionality and there is large lower
3rd face and vice versa.
Disadvantages - Further evaluation of
lower 3rd of face is needed.

55. LOWER FACE THROAT ANGLE
Sn-Gn-C Angle
 Formed by the intersection of lines Sn-
Gn & Gn-C
.
 Mean value:100⁰ ± 7⁰
INFERENCE
Obtuse lower face neck angle indicates
that any procedures that reduce the
prominence of chin should not be done.

56. LOWER VERTICAL HEIGHT DEPTH RATIO
Sn-Gn/C-Gn
Drop a line from Sn to Gn and C to Gn .
Measure the distance from Sn – Gn and C
–Gn .
 Mean value : 1.2 : 1
 If the ratio is more than 1 = short neck .
 Useful in determining the feasibility of
reducing / increasing the chin prominence.

57. LIP
POSITION
& FORM
Cm-Sn-
Ls Angle
Ls to
Sn-Pg
(Linear)
Li to Sn-
Pg
linear
Si to Sn-
Pg
Sn-
StmS/
Sn-
StmI
StmS-
U1
INTER-
LABIAL
GAP

58. NASOLABIAL ANGLE
Cm-Sn-Ls Angle
Cm – Sn - Ls - NASOLABIAL ANGLE
 Draw a line from Sn to Cm and drop a
line from Sn to Ls. Measure the angle
formed.
 Mean value : 102⁰ ± 8⁰
Important measurement in assessing the
anteroposterior maxillary dysplasias
ACUTE nasolabial angle = treated by
retracting the maxilla / maxillary incisors /
both.
OBTUSE nasolabial angle = suggests the
degree of maxillary hypoplasia and indicates
for maxillary advancement or orthodontic
proclination of maxillary incisors.

59. UPPER LIP PROTUSION
Ls to Sn-Pg (Linear)
Draw a line from Sn to soft tissue Pg,
the amount of lip Protrusion / Retrusion is
measured with perpendicular linear
distance from this line to the prominent
point of the lip.
 Standard value - 3±1mm
The abnormal values can be treated by
retracting or protracting the incisors ,
surgically or orthodontically advancing or
retracting the maxilla accordingly.

60. LOWER LIP PROTUSION
Li to Sn-Pg linear
Drop a line from Sn to Pg and the
amount of lip protrusion / retrusion is
measured with perpendicular linear
distance from this line to the most
prominent point of both lips .
 standard value - 2±1mm
By retracting / protracting the incisors
surgically / orthodontically advancing or
reducing the chin prominence , possible to
achieve desired lower lip.

61. MENTOLABIAL SULCUS DEPTH
Si to Sn-Pg
It is perpendicular distance
between deepest point on the
mentolabial sulcus to LiPg’ line.
Standard Value 4 ± 2 mm

63. VERTICAL LIP CHIN RATIO
Sn-StmS/Sn-StmI
To assess lower third of face
 Mean values : ( 1 : 2 )
Lower 3rd of the face ( Sn-Me ) can be
divided into three parts : length of the
upper lip ( distance from Sn to Stms )
should be approximately 1/3rd the total
and distance from Stmi to Me should be
2/3rd.
If the ratio becomes less than the normal
( ½ ) -- vertical reduction genioplasty is
recommended.

64. MAXILLARY INCISOR EXPOSURE
StmS- U1
 It is obtained by measuring the distance
between tip of upper central incisor and
Stms.
 Standard Value -2 ± 2 mm
Increased incisor exposure may be due
to vertical maxillary excess or short upper
lip .
Decreased incisor exposure may be due
to vertical maxillary deficiency or larger
upper lip.

65. INTER-LABIALGAP
It is the distance between Stms and Stmi
Standard Value - 2 ±2 mm
Patients with vertical maxillary excess
tend to have large interlabial gap and lip
incompetence
Patients with vertical maxillary
deficiency tend to have no Inter labial gap
and Lip redundancy.

66. HARD TISSUE

67. SOFT TISSUE

68. REFERENCES :
 Radiographic Cephalometry – Alexander Jacobson
Charles J. Burstone, H. Legan et al –Cephalometrics for
orthognathic surgery, J Oral Surgery, 1978, vol 36; 269-277
Charles J. Burstone, H. Legan- Soft tissue cephalometric
analysis for orthognathic surgery 1980, J Oral Surgery, 198, vol
38;744-750