Cogs soft tissue cephalometric analysis /certified fixed orthodontic courses by Indian dental academy

SOFT TISSUE ANALYSIS
• BURSTONE

• FACIAL FORM ( describes overall
horizontal soft tissue profile )

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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 +/- 4*

• Inference
• +ve value =angle is smaller (clockwise)
• -ve value=angle is large
(counterclockwise)
• increased +ve value  convex profile
increased-ve value  concave profile
(class3 skeletal and dental relationship)

• Disadvantages
• The location of deformity cannot be
assessed since it is not specific.

• Uses
• To analyze the soft tissue profile.

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

Inference
• Describes the amount of maxillary
excess/deficiency in anteroposterior
dimension

• +ve=maxillary retrusion (anterior)
• –ve=maxillary procumbency (posterior)

• Disadvantages

• some individuals have Glabella placed
more anteriorly / posteriorly. Therefore
correction of placement of glabella and
then analyzing is recommended

USES
• To determine whether the problem is in
maxilla/mandible.
• In treatment plan for anterior maxillary
advancement setback(+) total
alveolar/lefort-1 maxillary horizontal
advancement/set back .


G - Pg
• Mandibular prognathism
• Drop a perpendicular line to HP from
Glabella. Measure the position of the
pogonion from this line parallel to HP.

• Inference
• Increased –ve value indicated mandibular
deficiency is severe.
• Uses
• Indicates mandibular prognathism or
retrognathism

• Disadvantages
• This measurement should be evaluated in
conjunction with other values to distinguish
between microgenia ,macrogenia /
retognathia ie, if Pg is positioned posteriorly
further examination is necessary to
determine if the defect is a small hard tissue
chin, small mandible, average sized
mandible positioned posteriorly thin softtissue chin or a combination of these .

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 from Sn. Transfer the HP through
Menton. Measure the distance from G-Sn
and Sn – Me ( all perpendicular to HP )


1:1


• 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.

• Uses

• Anterior face proportionality is assessed by
taking the ratio of middle 3rd facial height to
lower 3rd facial height measured
perpendicular to HP.


Sn – Gn - C
• Lower face throat length/angle
• Formed by the intersection of lines Sn-Gn
& Gn-C.
• Mean value:100* +/- 7*


C


• INFERENCE
• Obtuse lower face neck angle indicates
that any procedures that reduce the
prominence of chin should not be done
(worms & others)
• USES
• For treatment planning to correct
anteroposterior facial dysplasias.

• Class III patients also have short , heavy
throats and obtuse lower face throat
angles . Should not undergo mandibular
setbacks.
• Alternate such as maxillary advancement ,
mandibular subapical, mandibular setback
with advancement genioplasty /
compromised tooth position may be
employed. www.indiandentalacademy.com

( 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


Sn
1.2
C
1

• Ratio of Sn – Gn and C – Gn is a little
larger than 1.
• If the ratio is more than 1 = short neck .
• Useful in determining the feasibility of
reducing / increasing the chin prominence.


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 : 102* +/- 8*
• Important measurement in assessing the
anteroposterior maxillary dysplasias.

• Useful in evaluating the position of upper
lip.
• 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.

Ls To Sn - Pg
• Upper lip protrusion.
• It denotes the amount of protrusion of
upper lip.
• Draw a line from Sn to soft tissue Pg and
the amount of lip Protrusion / Retrusion is
measured with perpendicular linear
distance from this line to the prominent
point of the lip.

• The abnormal values can be treated by
retracting / protracting the incisors ,
surgically / orthodontically / advancing the
maxilla.


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 .

• By retracting / protracting the incisors
surgically / orthodontically
advancing / reducing the chin prominence
, possible to achieve desired lower lip .


Si to Li - Pg
• Mento labial sulcus.
• To assess the prominence of the chin.
• Measured from the depth of the sulcus
perpendicular to Li – Pg.
• Mean value : 4 +/- 2


•

Deepened mento labial sulcus 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.

( Sn – Stms / Stmi – Me )
• Vertical Lip Chin Ratio
• To assess lower third of face .
• Hjfhwhfwhfoihfoi

• Mean values : ( 1 : 2 )

• Lower 3rd of the face ( Sn-Me ) can be
divided into three parts :
length of the upper lip ( distance from SnStms ) should be approximately 1/3rd the
total and distance from Stmi to Me should
be 2/3rd.
• 1:2 ratio should be maintained.
• If the ratio becomes less than the normal (
½ ) -- vertical reduction genioplasty is
recommended.

Stm-U1 Maxillary Incisor
Exposure

• Distance from upper lip to maxillary
incisor, is the key factor in determining
vertical position of maxilla. Also
corresponds to the pleasing smile.
• Drop a line parallel to HP from Stms and
another line from U1 ( incisal edge ) .
Measure the distance between them.

• 2mm of maxillary incisor show below the
upper lip when lip at rest is desirable.
• Pts with vertical maxillary excess tend to
show a larger amount of upper incisors
with the lips in repose.
• Treated orthodontic ally establishing large
curve of Spee.
• Long face pts with open bites may have
acceptable tooth-lip relations but may
need superior repositioning of post.
Portion of maxilla

• Short face : pts with maxillary deficiency
tend to show maxillary teeth with lip
relaxed and may have incisors at a level
superior to upper lip  giving a
edentulous look.
• Treatment : orthodontically extruding the
incisors and surgically positioning maxilla
inferiorly thereby increasing vertical
dimension.

Stms-Stmi Interlabial gap
• To measure the distance between the
upper and lower lip with lips in rest.
• Measure the distance between line drawn
from Stms and Stmi parallel to HP.
• Patients with vertical maxillary excess
have increased interlabial gaps and lip
incompetence.


• Patients with vertical maxillary deficiency
often have no interlabial gaps and lip
redundancy.
• Treatment : raising the level of maxilla to
shorten the height will decrease the large
interlabial gap and help patient to close
the lips without muscle tension.


Zero Meridian
• By dropping a line from the soft tissue (N),
the soft tissue surface directly anterior to
the hard tissue (N) at right angles to the
FH or the constructed HP.
• Ideally passes through the soft tissue
pogonion ( 0 +/- 2 ) to zero meridian and
8mm posterior to Sn.
• Variation indicates Retrusion / Protrusion in
mandible and maxilla separately.

SHORTCOMINGS
• Normal values for the COGS analysis are
best suited for the white adults population
only.
• Most patients presenting for orthognathic
surgery are young adults , due to the
process of facial growth and
development , cephalometric norms for
children can be expected to differ from
those of adults.

• Similarly patients of advanced age may
show changes simply due to aging
process such as loss of vertical dimension
( attrition of teeth / loss of teeth ) .


Cephalometric norms for orthognathic surgery in Black American
Adults.
Thomas R , Riccardo A , Samuel J

Journal of maxillofacial surgery , 1989
•

Purpose of this study was to develop normal values for COGS
analysis in Black American Adults .and compare it with the White
adults and among black males and females.


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Post. Cranial base
Skeletal angle of facial convexity
Maxillary skeletal protrusion
Skeletal lower anterior facial height
Upper post. Face height
Upper ant. Dental height
Lower ant. Dental height
Mandibular body length
Soft tissue thickness in lower lip
Lip length

• Were all significantly greater in Black Adults
• Less nasal depth and projection , bony chin
depth , and smaller nasolabial angle was
observed .


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