This document provides an overview of cephalometric analysis for orthognathic surgery (COGS). It describes the skeletal, dental, and soft tissue landmarks used in COGS and defines various linear and angular measurements between these landmarks. These measurements assess aspects of the cranial base, maxilla, mandible, dentition, facial height and depth, and soft tissue contours to evaluate skeletal and dental relationships for surgical treatment planning.

1. Department of orthodontics
Surgical Orthodontic Treatment Planning:
Profile Analysis and Mandibular Surgery
FRANK W. WORMS, ROBERT J. ISAACSON and T. MICHAEL
SPEIDEL
The Angle Orthodontics Jan 1976, Vol. 46, No. 1 (January
1976) pp. 1-25

2. • Charles J. Burstone et al (1978) 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)

3. • COGS system describes the horizontal and
vertical positions of the facial bones by the
use of constant coordinate systems as follows:
• Size of the bone are represented by direct
linear measurements.
• Shape of the bones are represented by the
angular measurements.

4. Skeletal And Dental Analysis
• ☺Landmarks
• Sella (S) - The center of Pituitary Fossa
• Nasion (N) – The most anterior point of
the nasofrontal suture in the
midsagittal plane
• Anterior Nasal Spine (ANS) – The
anterior most midsagittal point on the
tip of sharp bony process of maxilla
• Subspinale (A) – The deepest
midsagittal point on the concavity
between Anterior Nasal Spine and
Prosthion
• Supramentale (B) – The deepest point
in mid sagittal plane on the concavity
between infradentale and pogonion

5. • Pogonion (Pg) – Most anterior
mid sagittal point on the contour
of the chin
• Gnathion (Gn) – Constructed by
bisecting the Facial plane and
tangent to lower border of
mandible
• Menton (Me) – Most inferior
point on the inferior contour of
the chin
• Pterygomaxillary fissure (Ptm) –
The most posterior point on the
anterior contour of the maxillary
tuberosity

6. • Posterior Nasal Spine (PNS) – The
most posterior point on the contour
of the palate.
• Articulare (Ar) – The intersection of
sphenoid and the posterior border
of the condyle
• Gonion (Go) – constructed by
bisecting the posterior ramal plane
and mandibular plane.
• Mandibular Plane (MP) – It is the
line joining Gonion and Gnathion
• Nasal Floor (NF) – A plane
constructed by joining ANS and PNS

7. Reference plane
• The base line used for
comparison of most of the data
in this analysis is a constructed
plane called as Horizontal Plane
(HP)
• Most measurements in this
analysis will be made either
parallel to or perpendicular to
this Horizontal Plane.
• It is constructed by drawing a
line 7⁰ from SN, intersecting at
N

8. ☺Parameters
Cranial Base
☺Ar-Ptm (linear)
☺Ptm-N (linear)
Horizontal Skeletal Profile
☺N-A-Pg (angle)
☺N-A (linear)
☺N-B (linear)
☺N-Pg (linear)
Vertical Skeletal
☺N-ANS (linear)
☺ANS-Gn (linear)
☺PNS-N (linear)
☺MP-HP (linear
Vertical Dental
☺Upper 1 – NF (linear)
☺Lower 1 – MP (linear)
☺Upper 6 – NF (linear)
☺Lower 6 – MP (linear)
Maxilla and Mandible
☺PNS-ANS (linear)
☺Ar-Go (linear)
☺Go-Pg (linear)
☺B-PG (linear)
☺Ar-Go-Gn (angle)
Dental
☺OP-HP (angle)
☺A-B parallel to OP (linear)
☺Upper 1 – NF (angle)
☺Lower 1 – MP (angle)

9. • Cranial Base Length
☺Cranial base length is measured
by measuring the distance
between Ar and N
☺It is measured parallel to HP
☺The measurement Ar to N is a
relatively stable anatomical
plane, however it can be
changed by cranial surgery
☺Le Forte II and Le Forte III
surgery changes position of N
☺Autorotation of Mandible
changes position of Ar

10. ☺Two measurements are
considered in Cranial Base
length – Ar-Ptm and Ptm-N
☺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. Horizontal Skeletal Profile Analysis
☺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

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. N Perpendicular to A, parallel to HP
☺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. N Perpendicular to B, parallel to HP
☺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. N Perpendicular to Pg, parallel
to HP
☺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. Vertical Skeletal Analysis
☺A Vertical skeletal discrepancy may reflect an
anterior, posterior or complex dysplasia of the
face
☺It is divided into two components
☺Anterior component
☺Posterior component

18. N-ANS perpendicular to HP
☺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. ANS-Gn perpendicular to HP
☺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. PNS-N, perpendicular to HP
☺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. MP – HP Angle
☺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. Upper 1 to platal plane
☺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

23. Lower 1 to MP
☺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

24. Upper 6 to NF
☺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

25. Lower 6 to MP
☺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 respectivel

26. Maxilla and Mandible
ANS to PNS
☺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

27. Ar to Go
☺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

28. Go to Pg
☺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

29. Ar-Go-Gn Angle (Gonial angle)
☺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

30. Dental parameters
OP-HP (Angle)
☺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

31. ☺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

32. A-B parallel to OP
☺ 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

33. Upper 1 to NF (Angle)
☺ 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 (NF)

34. Lower 1 to MP (Angle)
☺ 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

35. SOFT TISSUE ANALYSIS

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

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

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

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

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

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

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

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

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

45. Cervical Point
(C) – the
innermost
point between
the submental
area and neck

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

47. G – Sn – Pg ( angle ) -Facial convexity /
contour angle
• 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)

48. G - Sn - Maxillary prognathism
• Drop line perpendicular to horizontal
plane from Glabella. Measure the
distance from perpendicular line to
Sn ( parallel to HP)
• Mean value: 6 ± 3 mm
Inference
• Describes the amount of maxillary
excess/deficiency in anteroposterior
dimension
• +ve=maxillary prognathisum
• –ve=maxillary retrognathisum

49. G - Pg - Mandibular prognathism
• 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 indicated
mandibal is retrognathic .

50. G-Sn / Sn-Me - Vertical height ratio
• (G-Sn / Sn-Me) 1:1
• 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 )
INFERENCE • 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

51. Sn – Gn - C - Lower face throat
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

52. ( Sn – Gn / C – GN ) - Lower vertical
height depth ratio.
• 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

53. LIP POSITION AND FORM
• 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

54. • 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.

55. Ls To Sn - Pg --- Upper lip protrusion.
• 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

56. • Li to Sn-Pg -- Denotes the amount of
protrusion of lower lip.
• 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

57. • Mentolabial Sulcus Depth
• It is perpendicular distance
between deepest point on
the mentolabial sulcus to Li-
Pg’ line
• Standard Value 4 ± 2 mm

58. is due to :
1. Flared lower incisors.
2. Extruded upper incisors
impinging on lower lip.
3. Flaccid lip tone and
abnormal morphology of
the lip itself .
4. Prominence of the chin also
contributes to deepened
mento labial sulcus
TREATMENT
• Up righting the lower
incisors.
• Intruding the maxillary
incisors.
• Cheiloplasty to retract lower
lip – helps in reducing the
MLS.
• Advancement genioplasty
increases the deepening of
MLS.
• Reduction genioplasty
decreases the excess MLS

59. • ( Sn – Stms / Stmi – Me ) -- Vertical Lip
Chin Ratio
• 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

60. • Maxillary Incisor Exposure
• 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

61. Inter Labial Gap
• 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

62. Thank you