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Cephalometrics

Dr.Omar .S.M.J.Ali

Introduction

Origin: ‘Cephalo’ means head and ‘Metric’ is measurement

Discovery of X-rays measurement of the head from shadows of bony and soft tissue landmarks on the image

Definitions

“The scientific measurement of the bones of the cranium and face, utilizing a fixed, reproducible position for lateral radiographic exposure of skull and facial bones” -- Moyers

“ A scientific study of the measurements of the head with relation to specific reference points; used for evaluation of facial growth and development, including soft tissue profile” -- Grabers

Cephalometric Imaging System

X- ray apparatus

An image receptor

Cephalostat

15 cm

Uses of cephalometric
In orthodontic diagnosis & treatment planning
In classification of skeletal & dental abnormalities
In establishing facial types
In evaluation of treatment results
In predicting growth related changes & changes associated with surgical treatment
Valuable aid in research work involving the cranio-dentofacial region


-- Moyers

Principle of Cephalometric analysis

To compare the patient with a normal reference group, so that differences between the patient’s actual dentofacial relationships and those expected for his/her racial or ethnic groups are revealed

-- Jacobson

Goals of Cephalometrics
To evaluate the relationships, both horizontally and vertically, of the five major functional components of the face:
The cranium and the cranial base
The skeletal maxilla
The skeletal mandible
The maxillary dentition and the alveolar process
The mandibular dentition and the alveolar process

-- Jacobson

Types of cephalograms

Lateral cephalometric

Taken with head in a standardized reproducible position at a specific distance from X-ray source

Uses :

Important in orthodontic growth analysis
Diagnosis & Treatment planning
Monitoring of therapy
Evaluation of final treatment outcome

Posteroanterior (p-a) cephalometric radiograph

Image Receptor and Patient Placement:
Image receptor is placed in front of the patient

The patient is placed so that the canthomeatal line is perpendicular to the image receptor

Uses :

Provides information related to skull width

Skull symmetry

Vertical proportions of skull, craniofacial complex & oral structures

For assessing growth abnormalities & trauma

Cephalometric landmarks

A conspicuous point on a cephalogram that serves as a guide for measurement or construction of planes – Jacobson

Requisites for a landmark

Should be easily seen on the x ray film
Be uniform in outline
Easily reproducible
Should permit valid quantitative measurement of lines and angles
Lines and planes should have significant relationship to the vectors of growth


Lateral Cephalometric

• Hard tissue landmarks

Nasion (N)
The frontonasal suture at its most superior point on
the curve at the bridge of the nose.

Anterior Nasal Spine (ANS)

The most anterior point on the maxilla at the level of
the palate.

Superior Prosthion (SPr or PR)

Also termed supradentale. The most anterior inferior
point on the maxillary alveolar process.

Subspinale ("A" Point)

The most posterior point on the curve between ANS
and PR (SPr). "A" point is usually found 2mm anterior
to the apices of the maxillary central incisor root.

Incision Superius (Is)

The incisal tip of the most anterior maxillary central
incisor.

Incision Inferius (Ii)

The incisal tip of the most labial mandibular central
Incisor.

Intradentale (Id)

The most anterosuperior point on the mandibular
alveolar process usually found near the CEJ
of the mandibular central incisor. Also
termed inferior prosthion.

Supramentale (« B » point)

The most posterior point of the bony curvature of the
mandible below infradentale and above Pogonion. "B"
Point is usually found near the apical third of the roots. of the mandibular incisors and may be obscured
during the eruption of these teeth. When the profile
of the chin is not concave, "B" point cannot be
determined.

Pogonion (Pog)

Pogonion is the most anterior point on the contour of
the chin. Pogonion usually is located by a tangent
perpendicular to the mandibular line or a tangent
dropped to the chin from nasion.

Menton (Me)

Menton is the lowest point on the symphyseal outline
of the chin.

Gnathion (Gn)

The most anteroinferior point on the lateral shadow
of the chin. Gnathion may be approximated by the
midpoint between pogonion and menton on the
contour of the chin

Basion (Ba)

The most inferoposterior point in the sagittal plane
on the anterior rim of the foramen magnum-the tip
of the posterior cranial base.

Bolton Point (BO)

The highest point in the upward curvature of the
retrocondylar fossa.

Posterior Nasal Spine (PNS)

The most posterior point on the bony hard plate in
the sagittal plane: usually the meeting point of the
inferior and superior surfaces of the hard plate.

Sella(S)

The center of the hypophyseal fossa (sella turcica). It
is selected by the eye, since that procedure has been
shown to be as reliable as a constructed center.

BILATERAL LANDMARKS

Orbitale (Or)
Orbitale has been defined as the lowest point of the
bony orbit. In the PA cephaJogram, each may be
identified but in the lateral cephalograms. the outlines
of the orbital rims overlap. Usually, the lowest point
on the average outline is used to construct the
Frankfort plane.

Gonion (Go)

Gonion is the most posteroinferior point at the angle
of the mandible. It may be determined by inspection
or by bisecting the angle formed by the junction of the
ramal and mandibular lines, and extending this
bisector through the mandibular border.

Condylion (Co)

Condylion is the most posterosuperior point on the
condyle of the mandible.

Articulare (Ar)

The intersection of the radiographic shadows:
the inferior surface of the cranial base and the posterior
surfaces of the necks of the condyles of the mandible.
Articulare is systematically used for condylion when
the latter is not reliably discernible. Displacement of
the condyle moves the articulare.

Pterygomaxillary Fissure (Ptm)

A bilateral teardrop-shaped area of radiolucency, the
anterior shadow of which is the posterior surfaces of
the tuberosities of the maxilla.

Porion (Po)

The "top" of the external auditory meatus. Sometimes,
because porion is quite unreliable, the "top" of the shadow of the ear rods is used, which is known as
“machine porion".






Soft tissue landmarks

Tracing technique

Tracing supplies & equipments

Lateral ceph, usual dimensions of 8 x 10 inches (patients with facial asymmetry requires antero posterior head film)

Acetate matte tracing paper.

A sharp 3H drawing pencil or a very fine felt-tipped pen

Masking tape

A few sheets of cardboard (preferably black), measuring approximately 6 x 12 inches, and a hollow cardboard tube

A protractor and tooth-symbol tracing template for drawing the teeth (optional)

Dental casts trimmed to maximal intercuspation of the teeth in occlusion

Viewbox (variable rheostat desirable, but not essential)

Pencil sharpener and an eraser

Cephalometric planes

Are derived from at least 2 or 3 landmarks

Used for measurements, separation of anatomic divisions, definition of anatomic structures of relating parts of the face to one another

Classified into horizontal & vertical planes

Horizontal planes
Frankfurt Horizontal plane
Porion-orbitale.





P
O

Sella-Nasion plane

S
N

Basion-Nasion plane:

Palatal plane:

Occlusion plane:

Ba
N
ANS
PNS

Mandibular plane: Different definitions are given in different analysis

1. Tweed- Tangent to lower border of the mandible
2. Downs analysis – extends from Go to Me
3. Steiner’s anlysis – extends from Go to Gn


Go
Gn
Me


Vertical planes
Facial plane
A-Pog line
Facial axis
E. plane (Esthetic plane)


Ptm
Gn
N
Pog
A
E plane

Measurement analysis :

Downs analysis
Steiner analysis
Tweed analysis
Wits appraisal
Rickets analysis
Mc Namara analysis
Holdaway soft tissue analysis


MEASUREMENT ANALYSIS
DOWN’S ANALYSIS
Given by WB Downs, 1925
One of the most frequently used cephalometric analysis after St analysis

Based on findings on 20 caucasian individuals of 12-17 yrs age group belonging to both the sexes

Consists of 10 parameters of which 5 are skeletal & 5 are dental

Skeletal parameters :
Facial angle

Average value is 87.8°, Range 82-95°

Gives an indication of anteroposterior positioning of mandible in relation to upper face

Magnitude increases in skeletal class 3 cases, decreases in skeletal class 2 cases

FH plane

N
Pog


Angle of convexity

Reveals convexity or concavity of skeletal profile

Average value 0°, Range = -8.5 to 10°
Positive angle or increased angle – prominent maxillary denture base relative to mandible
Decreased angle , negative angle.prominent of mand.



N
A
Pog

A-B plane angle

Mean value = -4.6°, Range = -9 to 0°
Indicative of maxillary mandibular relationship in relation to facial plane
Positive angle in class 3 malocclusion




Mandibular plane angle

Mean value = 21.9°, Range = 17 to 28°

Increased mandibular plane angle suggestive of vertical grower with hyperdivergent facial pattern

FHplane

Go
Me

Y- axis (growth axis)

Mean value = 59° , range = 53 to 66°
Angle is larger in class 2 facial patterns than in class 3 patterns
Indicates growth pattern of an individual
Angle greater than normal – vertical growth of mandible
Angle smaller than normal – horizontal growth of mandible



S
Gn
FH plane


Dental parameters
Cant of occlusal plane
occlusal plane to FH
Mean value = 9.3° , Range = 1.5 to 14°
Gives a measure of slope of occlusal plane relative to FH plane

FH plane

Inter- incisal angle
Average reading = 135.4° ,

Angle decreased in class 1 bimaxillary protrusion & class 2 div 1 malocculsion

Increased in class II div II case

Incisor occlusal plane angle

Average value = 14.5°, range = 3.5 to 20°

Increase in the angle is suggestive of increased lower incisor proclination

Incisor mandibular plane angle

Mean angulation is 1.4, range = -8.5 to 7°

Increase in angle is indicative of lower incisor proclination

Upper incisor to A-Pog line

Average distance is 2.7mm (range -1 to 5 mm)

Measurement is more in patients with upper incisor proclination

Limitations of Downs analysis

Too many landmarks
Too many measurements
Time consuming
-- Jacobson

STEINER ANALYSIS

Developed by Steiner CC in 1930 with an idea of providing maximal information with the least no. of measurements

Divided the analysis into 3 parts

Skeletal
Dental
Soft tissue

Skeletal analysis

S.N.A angle
Indicates the relative antero-posterior positioning of maxilla in relation to cranial base
>82° -- prognathic maxilla (Class 2)
< 82°– retrognathic maxilla (class 3)




S
N
A
Mean value -- 82°

S.N.B angle

Indicates antero-posterior positioning of the mandible in relation to cranial base
> 80°-- prognathic mandible
< 80°-- retrusive mandible



S
N
B
Mean value-- 80°

A.N.B angle

Denotes relative position of maxilla & mandible to each other


> 2° –- class 2 skeletal tendency

< 2°–- skeletal class 3 tendency

A
N
B
Mean value = 2°

Mandibular plane angle

Gives an indication of growth pattern of an individual

< 32° -- horizontal growing face

> 32°– vertical growing individual




S
N
Mean value = 32°

Occlusal plane angle

Mean value = 14.5°

Indicates relation of occlusal plane to the cranium & face

Indicates growth pattern of an individual



S
N

Dental analysis

Upper incisor to N-A(angle)

Normal angle = 22°

Angle indicates relative inclination of upper incisors
Increased angle seen in class 2 div 1 malocclusion




N
A

Upper incisor to N-A ( linear)

Helps in asssessing the upper incisor inclination

Normal value is 4 mm

Increase in measurement – proclined upper incisors




N
A

Inter-incisal angle

< 130 to 131° -- class 2 div 1 malocclusion or a class 1 bimax
> 130 to 131° – class 2 div 2 malocclusion

Mean value = 130 to 131°

Lower incisor to N-B (angle)

Indicates inclination of lower central incisors

>25 °-- proclination of lower incisors
< 25 °– retroclined incisors



N
B
Mean value of 25 °

Lower incisor to N-B (linear)

Helps in assessing lower incisor inclination
Increase in measurement indicates proclined lower incisors
Normal value– 4mm




N
B

Soft tissue analysis

S line

TWEED ANALYSIS

Given by Tweed CH, 1950
• Used 3 planes to establish a diagnostic triangle --
• Frankfurt horizontal plane
• Mandibular plane
• Long axis of lower incisor
• Determines position of lower incisor

FMPA = 25 °

IMPA = 90 °

FMIA = 65 °

FH plane
Mand plane

WITS APPRAISAL

It is a measure of the extent to which maxilla & mandible are related to each other in antero-posterior or sagittal plane

Used in cases where ANB angle is considered not so reliable due to factors such as position of nasion & rotation of jaws

In males point BO is ahead of AO by 1mm

In females point AO & BO coincide
In skeletal class 2 tendency BO is usually behind AO( positive reading)
In skeletal class 3 tendency BO is located ahead of AO ( negative reading)

RICKETTS ANALYSIS

Also known as Ricketts’ summary descriptive analysis
Given by RM Ricketts in 1961
The mean measurements given are those of a normal 9 year old child

The growth dependent variables are given a mean change value that is to be expected and adjusted in the analysis.

Dr. RM Ricketts

-- Jacobson

Landmarks

This is a 11 factor summary analysis that employs specific measurements to

Locate the chin in space

Locate the maxilla through the convexity of the face
Locate the denture in the face
Evaluate the profile


This analysis employs somewhat less traditional measurements & reference points
En = nose
DT = soft tissue
Ti = Ti point
Po = Cephalometric
Gn = Gnathion
A6 = upper molar
B6 = Lower molar
Go = gonion
C1 = condyle
DC=articular
CC = Center of cranium
CF = Points from planes at pterygoid

Xi point

A point located at the geometric center of the ramus. Location of Xi is keys of geometrically to Po-Or (FH) and perpendicular through Pt (pterygoid vertical [PtV]; aline perpendicular to FH at the posterior margin of the pterygopalatine fossa) in the following steps:

1. Planes perpendicular to FH and PtV are constructed.

2.The constructed planes are tangent to points R1, R2, R3, and R4 on the borders of the ramus.
3.The constructed planes form rectangular enclosing the ramus.
4. Xi is located in the center of the rectangle at the intersection of the diagonals.

Xi point --

Rl·mand. The deepest point on the curve of the anterior border of the ramus, one half the distance between the inferior and superior curves.

R2- mand. Apoint located on the posterior border of the ramus of the mandible.

R3-mand. Apoint located at the center and most inferior aspect of the sigmoid notch of the ramus of the mandible.

R4-mand. Apoint on the lower border of the mandible, directly inferior to the center of the sigmoid notch of the ramus.

Planes

Frankfurt horizontal -- Extends from porion to orbitale


Facial plane -- Extends from nasion to pogonion

Mandibular plane -- Extends from cephalometric gonion to cephalometric gnathion

Pterygoid vertical -- A vertical line drawn through the distal radiographic outline of the pterygomax fissure & perpendicular to FHP

Ba-Na plane -- Extends from basion to the nasion. Divides the face and cranium.

Occlusal plane -- Represented by line extending through the first molars & the premolars.

A-pog line -- Also known as the dental plane.

E-line -- Extends from soft tissue tip of nose to the soft tissue chin point.

Axis

Facial axis

Ptm
Gn

Condylar axis

Corpus axis

Interpretation

This consists of analyzing:

Chin in space

Convexity at point A
Teeth
Profile

Chin in Space

This is determined by :

Facial axis angle

Facial (depth) angle
Mandibular plane angle

Facial axis angle

• Mean value is 90˚ ± 3˚
• Does not changes with growth
• Indicates growth pattern of the mandible & also whether the chin is upward & forward or downward & backwards

Facial (depth) angle

• Changes with growth
• Mean value is 87˚± 3˚ with an increase of 1˚ every 3 years
• Indicates the horizontal position of the chin & therefore suggests whether cl.II or cl.III pattern is due to the position of the mandible

Facial (depth) angle

Mandibular plane angle
• Mean -- 26˚± 4˚at 9 yrs with 1˚decrease every 3 yrs
• High angle -- open bite – vertically growing mandible
• Low angle – deep bite – horizontally growing mandible
• Also gives an indication about ramus height





Po
O

Convexity at point A

This gives an indication about the skeletal profile

Direct linear measurement from point A to the facial plane

Normal at 9 yrs of age is 2mm & becomes 1mm at 18 yrs of age, since mandible grows more than maxilla

High convexity – Cl II pattern

Negative convexity – Cl III pattern

Teeth

Lower incisor to A-Pog
Referred to as denture plane
Useful reference line to measure position of anterior teeth
Ideally lower incisor should be located 1 mm ahead of A-Pog line
Used to define protrusion of lower arch

Upper molar to PtV

Measurement is the distance between pterygoid vertical to the distal of upper molar
Measurement should equal the age of the patient +3.0mm
Determines whether the malocclusion is due to position of upper or lower molars
Useful in determining whether extractions are necessary

Lower incisor inclinations

Angle between long axis of lower incisors & the A-Pog plane
On average this angle this angle should be 28 degrees
Measurement provides some idea of lower incisor procumbency

Profile

Lower lip to E plane
Distance between lower lip & esthetic plane is an indication of soft tissue balance between lips & profile

Average measurement is -2.0mm at 9 yrs of age

Positive values are those ahead of E- line

Mc NAMARA ANALYSIS

Given By Mc Namara JA, 1984

In an effort to create a clinically useful analysis, the craniofacial skeletal complex is divided into five major sections.
• Maxilla to cranial base
• Maxilla to mandible
• Mandible to cranial base
• Dentition
• Airway

Dr. Mc Namara JA

-- Jacobson

MAXILLA TO CRANIAL BASE

Soft tissue evaluation


Nasolabial angle
Acute nasolabial angle – dentoalveolar protrusion, but can also occur because of orientataion of base of nose

Cant of upper lip

Line is drawn from nasion perpendicular to upper lip

14 degree in females

8 degree in males

Hard tissue evaluation

Anterior position of point A = +ve value

Posterior position of point A = -ve value

In well-balanced faces, this measurement is 0 mm in the mixed dentition and 1 mm in adult






Maxillary skeletal protrusion
Maxillary skeletal retrusion

Maxilla to mandible

Anteroposterior relationship
Linear relationship exists between effective length of midface & that of mandible

a) Lower Anterior Face Height (LAFH)

LAFH is measured from ANS to Me

In well balanced faces it correlates with the effective length of midface

Vertical relationship
Vertical maxillary excess – downward & backward rotation of mandible, increasing lower anterior facial height

Vertical maxillary deficiency – upward & forward rotation of mandible, decreasing lower anterior facial height

b) Mandibular plane angle

On average, the mandibular plane angle is 22 degrees ± 4 degrees

A higher value  excessive lower facial height

lesser angle Lower facial height

c) The facial axis angle

In a balanced face --90 degrees to the basion-nasion line

A negative value  excessive vertical development of the face

Positive values  deficient vertical development of the face

Dentition

a) Maxillary incisor position


The distance from the point A to the facial surface of the maxillary incisors is measured

The ideal distance  4 to 6 mm

b) Mandibular incisor position
In a well-balanced face, this distance should be 1 to 3 mm

AIRWAY ANALYSIS

Upper Pharynx
Width measured from posterior outline of the soft palate to a point closest on the pharyngeal wall

The average nasopharynx is approximately 15 to 20mm in width.

A width of 2mm or less in this region may indicate airway impairment

Lower Pharynx

Width – point of intersection of posterior border of tongue & inferior border of mandible to closest point on posterior pharyngeal wall

The average measurement is 11 to 14 mm, independent of age

Greater than average lower pharyngeal width-- possible anterior positioning of the tongue

THE HOLDAWAY SOFT TISSUE ANALYSIS

Given by Dr. Reed Holdaway, 1984

Dr. Reed Holdaway in series of two articles outlined the parameter of soft tissue outline

Analysis consists of 11 measurement

Dr. Reed Holdaway

-- Jacobson

• Facial Angle (90 degree)

• Ideally the angle should be 90 to 92 degrees
>90 degree: mandible too protrusive


<90 degree: recessive lower jaw
•

2. Upper lip curvature (2.5mm)

Depth of sulcus from a line drawn perpendicular to FH & tangent to tip of upper lip

Lack of upper lip curvature – lip strain

Excessive depths could be caused by jaw overclosure

3. Skeletal convexity at point A (-2to 2mm)

Measured from point A to N’-Pog’ line

Not a soft tissue measurement but a good parameter to assess facial skeletal convexity relating to lip position

Dictates dental relationships needed to produce facial harmony

4. H-Line Angle(7-15 degree)

Formed between H-line & N’-Pog’ line
Measures either degree of upper lip prominence or amount of retrognathism of soft tissue chin
If skeletal convexity & H-line angles donot approximate, facial imbalance may be evident

5. Nose tip to H-line (12mm maximum)

Measurement should not exceed 12mm in individuals 14 yrs of age

6. Upper sulcus depth (5mm)

Short/thin lips -measurement of 3 mm may be adequate
Longer/thicker lips- 7mm may still indicate excellent balance

7.Upper lip thickness (15mm)

Measured horizontally from a point on outer alveolar plate 2mm below point A to outer border of upper lip

8. Upper lip strain

Measured from vermillion border of upper lip to labial surface of maxillary center inc.

Measurement should be approx same as the upper lip thickness (within 1mm)

Measurement less than upper lip thickness – lips are considered to be strained

9. Lower lip to H-line(0mm)

Measured from the most prominent outline of the lower lip
Negative reading – lips are behind the H line
Positive reading – lips are ahead of H line
Range of -1 to +2mm is regarded normal

10. Lower sulcus depth (5mm)

11. Soft tissue-chin thickness (10-12mm)

Measured as distance between bony & soft tissue facial planes

In fleshy chins, lower incisors may be permitted to stay in a more prominent position, allowing for facial harmony