Department of orthodontics

Surgical Orthodontic Treatment Planning: Profile Analysis and Mandibular Surgery

FRANK W. WORMS, ROBERT J. ISAACSON and T. MICHAEL SPEIDELThe Angle Orthodontics Jan 1976, Vol. 46, No. 1 (January 1976)

pp. 1-25

• 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)

• 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.

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

• 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

• 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

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

☺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)

• 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

☺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

• ☺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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Dental parametersOP-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

☺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

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

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)

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

SOFT TISSUE ANALYSIS

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

Columella point (Cm)

– The most anterior point on the columella (nasal septum) of the nose

Subnasale (Sn) – The point at which the

columella merges with the upper lip in the midsagittal

plane

Labrale superius

(Ls) - A point indicating the

mucocutaneous border of the

upper lip

Stomion superius (Stms)- The lower most point on the

vermilion border of the upper lip

Stomion inferius (Stm i )- The upper most point on the

vermilion border of the

lower lip

Labrale inferius (Li) - A point

indicating the mucocutaneous

border of the lower lip

Soft tissue Pogonion

(Pog’)- The most

prominent or anterior point on the chin in

midsagittal plane

Soft tissue Menton (Me’) – lowest point on the contour

of the soft tissue chin

Cervical Point (C) – the

innermost point between the submental area and neck

Soft tissue Gnathion (Gn’)- The constructed

midpoint between soft

tissue pogonion and soft tissue

menton

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)

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 mmInference • Describes the amount of maxillary

excess/deficiency in anteroposterior dimension

• +ve=maxillary prognathisum • –ve=maxillary retrognathisum

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 .

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

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

( 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

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

• 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.

• 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

• 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

• Mentolabial Sulcus Depth

• It is perpendicular distance between deepest point on the mentolabial sulcus to Li-Pg’ line

• Standard Value 4 ± 2 mm

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 . • 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

• 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

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

Thank you