cephalometrics by almuzian ok ok

University of glasgow

Cephalometrics in orthodontics

Dr. Mohammed Al-Muzian

1/1/2013

Cephalometrics in orthodontics

Definition

Literally - measurement of the head. More commonly - means of using

standardised skull radiograph to assess facial, dental and skeletal

relationships as well as airway analysis.

History

Developed in 1930's by Broadbent (USA) and Hofrath (Germany)

Originally postero-anterior and lateral views recommended to allow 3

dimensional assessment Broadbent, 1937

Equipment

Collimated X-ray source - 5 feet from midsagittal plane of patient

Cephalostat - head positioner

Aluminium wedge - increases soft tissue definition

Film - placed 1.5-1.8 foot behind midsagittal plane of patient with rare

earth metal intensifying screen or SSS

Uses

1. Diagnosis and treatment planning

Detection and localization of unerupted teeth or pathology

Assessment of horizontal skeletal relationship

Assessment of vertical skeletal relationship,

assessment of incisor positions (e.g lip trap behind incisors, lower lip line

in Class II D2, lower incisor to upper centroid)

Assessment of incisor inclination

Assessment of soft tissue profile

Assessment of the reliability of functional appliance

Orthognathic surgery planning and vto

Mohammed AlmuzianPage 1

Airway assessment

2. During active treatment (Broadbent, 1937)

Post-functional to assess skeletal and dental relationship

To determine if extraction is required or not

Pre-space closure to check L1 position and anchorage

In orthognathic to determine the goals are met

3. End of treatment

To check arch relationship

To check that target met

Plan retention

Baseline records to monitor changes in postretention phase

4. During retention to assess relapse and unfavourable growth

specially in orthognathic

5. To assess and monitor growth by using series of radiograph or

compare it to norms (Bjork, 1954)

6. Research purposes

Why lateral cephalometric radiograph is more common

Most of the treatable problem in AP and vertical while transverse difficult

to treat

Other views are difficult to measure

Weakness of Radiographical cephalometric in TP

1. Weak validity

2. Reference lines (cranial base) which is not reliable

3. Inheriting error

4. Norms are collected from normal population and cannot applied to

abnormal face or in malocclusion


5. Consider the AP problem and ignoring the vertical and transverse

analysis

A study by Brukes 1999, Whaite 1992 to determine the reliability of

cephalometric in the treatment plan showed that only 4-20 % of

treatment plan can be changed if the cephalometric were taken.

Cephalometric: Nijkamp 2008, that cephalometrics are not required

for orthodontic treatment planning, as they did not influence treatment

decisions for patient with class II malocclusion.

Requirements of Cephalometric measurement

It should be

1. Reliable

2. Stability of point used

3. Not effected by patient size or age

Types of error in cephalometric analysis

1. Systematic error due to different concept of landmark identification

2. Random error which include

A. Projection errors

• Arise due to R/G being a 2 dimensional representation of 3

dimensional objects

• Points on midsagittat plane are unaffected

• Points in the para-mid-sagittal plane are distorted

• Angular measurements become too obtuse

• Linear measurements are shortened

Types of projectional errors

I. Magnification


Although standardised set-ups exists, magnification factor of

approximately 10% should be taken into account; R/G scales are often

included to allow this factor to be accurately calculated.

Shorter focal distance increase projection errors

Longer focal distance decrease projection errors

II. Head position

Should be positioned with Frankfort plane horizontal or in natural

postural position

Teeth in centric occlusion (reproducible position) significant

errors can occur if positions other than centric occlusion used.

To reduce projection errors

Control magnification by correct focal object distance,

Correct head position

B. Errors of Identification

1. Landmark identification

All points have an 'envelope of error' which is dependent on:

• Anatomic characteristics of landmark, points on edges are easier to

locate than points within structures.

• Differing definition of landmark, influenced by understanding and

experience

2. Method of registration – manual or digital

To reduce identification errors

Clear understanding of point definition

Automated computerised R/Gic identification of landmarks

Aluminium wedge for better sharpness

C. Errors within the measuring system


Cephalometric analysis used - different methods available, some more

complicated than others, method chosen should reflect clinical / research

use

Operator - influenced by experience and calibration

Environment — light box used, ambient light conditions, quality of

image,

To reduce the errors within the measuring system

Careful selection of analysis

Increased operator experience by duplicate the measurements and by

error calculation measurement as well as care when interpreting results

Good quality film and standardisation

Soft tissue cephalometric analysis

Profile analysis

1. Soft tissue nasion to FH: (Sandler 2006) Maxilla should be

approximately 2-3 mm in front, and the soft tissue pogonion should lie 2

mm behind this facial plane

2. Facial vertical or Meridian line developed by Gonzales-Ulloa,

from soft tissue nasion, perpendicular to true horizontal line with patient

in natural head position. Subnasale is on this line. Soft tissue pogonion

should be 0 ± 2 mm to this line.

3. Z angle (of Merrifield). A tangent to the chin and vermilion

border of most prominent lips should ideally intersect with FH at 80+9

4. Profile angle is the angle of convexity described by Burstone.

This is the angle formed by the soft tissue glabella, subnasale, and soft

tissue pogonion. It represents a total facial angle range of 165 -175


5. Powell analysis, which is made up of the nasofrontal angle,

nasofacial angle, nasomental angle, and mentocervical angle, has been

developed to give insight into an ideal facial profile.

Lip analysis

a) Anteroposterior lip position

1.Esthetic line (E-line). Joins the nasal tip to soft tissue pogonion. The

upper lip should be 4 mm and the lower lip 2 mm behind this line in

adults. This is very dependent on nasal and chin projection.

2.Steiner line (S-line). Joins soft tissue pogonion to the midpoint between

subnasale and nasal tip. The lips should touch this line.

3.Harmony line: The H line, as introduced by Holdaway. The H-angle is

formed by a line tangent to the chin and upper lip with the NB line.

Holdaway said the ideal face has an H-angle of 7° to 15°, which is

dictated by the patient's skeletal convexity. The ideal position of the

lower lip to the H line is 0 to 0.5 mm anterior.

b) Relationship of upper lip to nose

Naso-labial angle

It is formed between the nasal columella and upper lip.

Average value: 85–120.

It can be divided by true horizontal at subnasale point into two angles

(upper one represent nasal angulation 28 degree and lower angle

represent upper lip angulation 85 degree.

In general it depends on columella, anteroposterior position of maxillary

incisors and anterior maxilla, the morphology of the upper lip, as well as

the vertical position of the nasal tip.

c) Relationship of lower lip to chin

Labiomental angle


It is formed by lower lip anterior, soft tissue point B and menton.

It depends on the lower incisor inclination and anterior lower face height.

Average value: 110–130 degree.

Excessively proclined lower incisor teeth, a prominent chin and a reduced

lower anterior facial height may lead to an acute labiomental angle.

Cephalometric analysis

Reference planes

Natural head position

NHP determined by the internal physiologic mechanism.

Two types

1. Crude : This position is obtained when relaxed individuals look at a

distant object in the horizon

2. Sensory : look into their own eyes in a mirror and incline their

heads up and down in increasingly smaller movements until they feel

comfortably positioned

The natural head position can be reproduced within 1 or 2 degrees.

BUT The inclination of SN to the true horizontal plane (or to the

Frankfort plane if true horizontal plane is not known) should

always be noted, and if the inclination of SN differs significantly

from 8 degrees, any measurements based on SN should be corrected

by this difference

NHP depend on

1. Audio-viusal reflex

2. Skeletal pattern: in cl2 cases the pt tried to lift their face upward


3. Growth pattern: post rotation cause the mandible to flex their

head down

4. Respiratory pattern : cause tilting to increase airway patency

Frankfort plane

Frankfort plane suffers from two difficulties

1.The first is that both its anterior and posterior landmarks (both point are

bilateral), which can be difficult to locate and the use of machine porion

is not accurate. Another way to obtain a Frankfort line is simply to draw

it at a specific inclination to SN, usually 6 degrees. However, although

this increases reliability and reproducibility, it decreases accuracy

2.It represents anatomical not physiological line.

SN plane

Used to

1. relate the jaw to cranial base

2. Inclination of U1

3. Superimposition

It highly reproducible lines since its point’s are easily located and single

points.

Maxillary plane

Used to

1. Inclination of U1 to maxilla

2. Assess the vertical jaw relation (MaxMp, MaxOcc plane, MaxSN

plane)

3. Superimposition


Occlusal plane:

1. Bisecting: A line joins the midpoint of the overlap of the mesio-

buccal cusps of the upper and lower first molars with the point bisecting

the overbite of the incisors. This is used by Downs (1948, 1952) and

Steiner (1953).

2. The functional occlusal plane as defined by the line joining the

midpoint of the overlap of the mesio-buccal cusps of the first molars and

the buccal cusps of the pre-molars or deciduous molars. This is used by

Ricketts (1960, 1961) and in the Wits analysis (Jacobson, 1975).

3. Max OP The line joining the midsection of the molar cusps with

the tip of the upper incisor, used by Bjork (1947, 1954).

Mandibular plane:

Used to

1. Superimposition

2. Assess the vertical jaw relation (MaxMp)

3. Inclination of L1 to mand

Three mandibular planes are used:

1. The tangent to the lowermost border of the mandible, used by

Tweed (1947, 1953, 1954), Wylie (1947, 1954) and Ricketts (1960,

1961).

2. The line joining the gonion with menton, used by Downs (1948,

1952) and in the Eastman analysis (Mills, 1970).

3. The line joining gonion and gnathion, used by Steiner (1953).


Cephalometric landmarks

Artioculare point : intersection of post cranial base and post line of

ascending ramus

Basion: most ant inf point of the magnum

Cephalometric analysis technique

A. Those that solely describe disharmony:

1.Down's

2.Steiner

3.Rickett

4.Harvold

5.McNamara

6.Sassouni — useful for describing face height, Sassouni coined the Opal

— an amalgamation of norms derived from other studies

7.Wits by Johnston

8.Wylie

9.Tweed

B. Those aid in treatment planning:

Ballarad conversion

C. Those analyse change due to growth and treatment

1.Pancherz : measure linear changes from perpendicular drawn from sella

to occlusal line (weakness is that it depend on max structure and OP

which is changeable)

2.Pitchfork analysis by Johnston superimposition of 2 or more lateral

cephalometric registered on a stable reference point

3.Bolton Template Analysis

D. Those used for research purposes

• Bjork


Ballard conversion cephalometric analysis

A. The OJ will be used as indicator for skeletal relationship after mental

normalization of the incisor inclination in relationship to their cranial

base

B. Care should be taken if the FMPA angle is abnormal, in this case the

lower incisor inclination should be reduced by one degree for each

degree increase in the FMPA angle and vice versa.

C. The conversion tracing allows clear visualization of dental base

relationship by ignoring the soft tissue influence and placing the incisors

at the average angulation to the maxillary and mandibular planes for the

particular MM angle in question. This assumes that teeth tip about a

point at the junction of the apical third and coronal two-thirds of the

root, and that the root is in the centre of the alveolus

• The method is as follows.

1. Trace on a separate piece of tracing paper the outline of the maxilla,

the mandibular symphysis, the incisors, and the maxillary and

mandibular planes.

2. Mark the ‘rotation points’ of the incisors one-third of the root length

away from the root apex.

3. By rotating around the point marked, reposition the upper incisor at

an angle of 109° to the maxillary plane. Repeat for the lower incisor.

Weaknesses of this analysis are:

It rely on that incisors have average stable inclination to cranial base

Incisors can tip around centroid.

Both r not true

Interpretation

A. If after adjustment, the lower incisor occlude behind the cingulum but

not behind the upper tooth, it is called mild skeletal II


B. If it occlude behind the cingulum and opposite to the palate it called

sever skeletal II

C. Same for class III., if lower incisor anterior to upper cingulum and

before reverse OJ, it is mild skeletal class III, but if it is in reverse OJ it

is sever skeletal class III.

Pi analysis (Kumar 2012)

The Pi analysis has been introduced as a new method to assess the AP

jaw relationship.

It consists of two variables, the Pi angle and the Pi linear and utilizes the

skeletal landmarks G and M points to represent the mandible and

maxilla, respectively. G and M points were originally introduced by

Nanda and Merrill and later used by Braun and co-workers, being

constructed at the centre of the largest circle placed tangent to the

anterior, superior (represented by nasal floor) and palatal surfaces of the

premaxilla and the internal anterior, inferior and posterior surfaces at the

mandibular symphysis, respectively

These points are not affected by local remodelling secondary to dental

movements, unlike points A and B. The reference plane utilized in

measuring the Pi analysis is the true horizontal, a line perpendicular to

the true vertical obtained in natural head position (NHP). Several

researchers have argued that NHP is the logical reference and

orientation position for the evaluation of craniofacial morphology. The

Pi angle is constructed in the following manner: a perpendicular line is

drawn from G point to intersect with the true horizontal at G’, with a

further line constructed from G’ to M point. Connecting the points G’G

and G’M forms the angle GG’M, or Pi angle. The name is chosen

because the angle resembles the symbol Pi (p) in geometry. A virtual


line is also drawn from M point to intersect perpendicular to the true

horizontal at M’. The Pi linear is the distance between points G’ and M’

The mean value for the Pi angle in skeletal class I were 3.40+2.04

There is another angle to measure the AP relationship called Beta angle

Steiner analysis

The component of his analysis

Skeletal relationship

1. SNA

2. SNB

3. ANB

4. SN-Occ

5. SN-MP

Dental relationship

1. UI-NA 4 mm and angles

22

2. LI-NB 4mm and angle 25


3. LI-MP

4. Upper denture base legnth (U6-NA)

5. Lower denture base legnth (L6-NB)

6. II angle

This is what is called Steiner stick

Downs Analysis

This was one of the earliest comprehensive analyses. Presentation of this

analysis is often accompanied by the wiggle graph

Skeletal component:

1. Facial angle: N-Pog to FH. It represent the position of the chin

2. Facial convexity: N-A-Pog. It measure max protrusion in relation

to total profile

3. Dentoalveolar convexity angle: AB to N-pog. Relate the

dentoalveolar to the total profile.

4. FMPA angle

5. Occp-FH. To orient the cant of occlusion

6. Y axis

Dental component

1. UI to A-pog in mm

2. LI to MP

3. LI-Occ

4. II angle

Ricketts (1960, 1961)

This again is profile orientated.


It includes an aesthetic plane

And the others same like Downs' analysis.

Harvold Analysis

1.The maxillary unit length CD-ANS,

2.the mandibular unit length CD-Pog

3.The difference between these numbers provides an indication of the size

discrepancy between the jaws.

4.Lower face height (ANS-ME).

In analysing the difference between maxillary and mandibular unit

lengths, it must be kept in mind that the shorter the vertical distance

between the maxilla and mandible, the more anteriorly the chin will be

placed for any given unit difference, and vice versa.

McNamara Analysis

The McNamara analysis, originally published in 1983, combines

elements of previous approaches (Ricketts and Harvold)

In this method, both the anatomic Frankfort plane and the basion-nasion

line are used as reference planes.

A. Jaw-cranial base relationship


1. Maxilla to cranial base-

nasion perpendicular," a

vertical line extending

downward from nasion

perpendicular to the Frankfort

plane. The maxilla (point A)

should be on or slightly ahead

of this line.

2. Mandible to cranial base-nasion perpendicular," a vertical line

extending downward from nasion perpendicular to the Frankfort plane.

The mandible (point Pog) should be on or slightly back of this line

B. AP Maxillomandibular relationship

1. The maxillary unit length CD-ANS,

2. the mandibular unit length CD-Pog

3. The difference between these numbers provides an indication of

the size discrepancy between the jaws.

C. Vertical Maxillomandibular relationship

Lower face height (ANS-ME).

D. Dental relationship

1. Upper incisor is related to the maxilla using a line through point A

perpendicular to the Frankfort plane, (4-6mm).

2. The lower incisor is related as in the Ricketts analysis, primarily

using the A-pogonion line

E. Airway space (upper and lower pharyngeal width)

Eastman Analysis, after Mills 1972

A. AP relationship

1. SNA


2. SNB

3. ANB+ Mills correction

B. Vertical relationship

1. SN-MAXP

2. MMPA

3. FMPA

C. Dental relationship

1. SNI

2. UI-MAXP

3. LI-MP

Factors affecting ANB angle

1. Cranial base length

2. Cranial base orientation

3. Also ANB depend on A and B which influenced by teeth position

4. Jaw orientation

5. Facial height

Eastman correction correct the first one only when SN-Max plane 5-11

degree only. If the SNA is more than 82 degree then subtract 0.5 degree

form ANB for each degree increase in the SNA and vise versa. Eastman

correction applied on the SNA but not SNB because N point movement

has a bigger effect on SNA than SNB.

Opal analysis, by BOS

Assessment of AP skeletal

1. SNA 81+3

2. SNB 78+3

3. ANB 3+2


4. WITS (BO should be -1mm from AO in male and at the same line

in female)

5. Ballard conversion

Assessment of vertical skeletal

1. FMPA 27+5

2. MMPA 27+5

3. Facial height.

TAFH: UAFH + LAFH (120mm) but not direct line from nasion to

menton

UAFH: linear measurement from point nasion perpendicularly to

maxillary plane (55mm, 45% of the TAFH)

LAFH: linear measurement from point menton perpendicularly to

maxillary plane to perpendicular (65mm, 55% of the TAFH)

TPFH: UPFH + LPFH (80mm) but not direct line from gonion to

sella

UPFH: linear measurement from point sella perpendicularly to

maxillary plane (45mm, 75% of the TPFH)

LPFH: linear measurement from point gonion perpendicularly to

maxillary plane (35mm, 25% of the TPFH)

Assessing dental relationship

1. Ui to maxillary plane 109+6

2. LI to mandibular plane 93+6

3. II angle 135+10

4. LI to A-Pog is 1-2mm ahead of APog ( This proposed by Downs

for UI and then used by Rickets who mention it as a matter related to

optimum esthetic, then used by William for stability, but Houston

disagreed with it)


5. Li to centroid (0-2mm)

Assessing soft tissue

Using E line

Sassouni Analysis

Use horizontal anatomic planes-the inclination of the anterior

cranial base, Frankfort plane, palatal plane, occlusal plane, and

mandibular plane-tend to converge toward a single point in well-

proportioned faces.

Sassouni evaluated the anteroposterior position of the face and

dentition by noting the relationship of various points to arcs drawn from

the area of intersection of the planes. In a well-proportioned face, the

anterior nasal spine (representing the anterior extent of the maxilla), the

maxillary incisor, and the bony chin should be located along the same

arc.

If the lines intersect posterior to occipital bone it means short face

(skeletal deep bite) and vice versa.

Wits analysis by Jacobson

1. The Wits analysis was conceived primarily as a way to overcome

the limitations of ANB as an indicator of jaw discrepancy.

2. It is based on a projection of points A and B to the functional

occlusal plane, along which the linear difference between these points is

measured.

3. The Wits analysis, in contrast to the McNamara and Harvold

analysis, is influenced by the teeth horizontally because points A and B

are somewhat influenced by the dentition and vertically because the

occlusal plane is determined by the vertical position of the teeth.


4. The functional occlusal plane being used rather than an occlusal

plane influenced by the vertical position of the incisors.

5. Another weakness is that Wits appraisal rely on 4 points which is a

source of an error.

Tweed (1946, 1953, 1954)

1. A set of three angular measurements (which constitute what has

come to be known as the Tweed triangle), introduced by C. H. Tweed in

1946.

2. It establishes the prognosis of treatment on the basis of the Tweed

Triangle, which is formed by the Frankfort, mandibular and lower

incisor axis planes.

3. The Frankfort mandibular planes angle (FMA) is fixed for each

individual.

4. A Frankfort mandibular incisor angle (FMIA) of 65-70° is

considered ideal for good aesthetic outcomes.

5. The lower incisor angle is, therefore, adjusted to achieve the ideal

FMIA and treatment is planned to this end.

6. The analysis has fallen into disrepute in some circles as it has been

wrongly used as a total analysis even though Tweed stressed that it was

intended merely as a treatment aid.

Bjork (1947, 1954)

This analysis is the most complicated involving over 90

measurements.

It is therefore research orientated,

The analysis is based on the polygon N—S—Ar—Go—Gn

Using the three angles: saddle (N—S—Ar), articular (S—Ar—Go)

and gonial (Ar—Go—Gn) and the lengths of the sides of the polygon.


The analysis also assesses the anterior and posterior face height

relationship PFH : AFH ratio

Same like other found in Eatman analysis

Bolton Template Analysis

At present, templates exist in two forms:

The schematic templates show the changing position of selected

landmarks with age on a single template.

The anatomically complete templates , a different one for each

age, are particularly convenient for direct visual comparison of a patient

with the reference group while accounting for age

The first step in template analysis, obviously, is to pick the correct

template from the set of age. So that the length of the anterior cranial is

approximately the same for the patient and the template.

Template analysis in this fashion has two advantages: first, it allows the

easy use of age-related standards and second, it is quick.

Additional information about cephalometric interpretation

The Maxillay incisors to the maxillary Plane angle (UI-Max plane):

relates the axial inclination of the maxillary incisor to the maxillary

plane. It is important to know the U1 inclination for many purposes:

Aesthetic purposes

Stability

PD health

Treatment mechanics as the existing inclination will determine the types

of tooth movement that are required to correct any anomalies in the

incisor relationships.


The Mandibular incisors to the mandibular Plane (LI-Mand Plane)

angle: relates the axial inclination of the mandibular incisor to the

mandibular plane. The range of the average LI-Mand Plane angle cannot

be applied unless the MMPA is within the average limits. The labio-

lingual position of the crown of the lower incisors is influenced by the

balance between the lips and the tongue; thus, when the lower border of

the mandible is inclined steeply relative to the maxillary plane, there

tend to be a compansotory retroclination of the lower incisors.

Therefore, for every degree that the MMPA exceeds 27˚, the expected

value of the lower incisor inclination should be reduced by 1˚ and vice

versa (Houston, 1992).

Interincisor angle (UI –LI): relates the axial inclination of the

maxillary incisor to the axial inclination of the mandibular incisor. The

interincisal angle is associated with the depth of the overbite when there

is an incisor contact; if this angle is wide, then even if incisor contacts

achieved during the eruption of the teeth or as a result of orthodontic

treatment, they will tend to erupt past one another. Thus, the wider the

interincisal angle the deeper the overbite. (Mills 1973)

Lower incisal edge to upper incisor centroid distance: this is

measured as the distance between the perpendicular projections of the

lower incisor edge and the centroid of the upper incisor root on the

maxillary plane (Houston, 1989). The centroid is the midpoint of the

upper incisor roots as defined by Houston and Tulley 1986. This relation

is associated with overbite depth in that the further behind the centroid

the lower edge lies, the deeper the overbite is liable to be, except if the

overbite is incomplete. It focuses attention on the tooth movement that

will be required to obtain a satisfactory incisor relationship and stable

overbite.


The line from A to pogonion (A-Pog): it has been used to assess the

position of the crowns of the lower incisors (Williams, 1969). Williams

suggested that the best aesthetic results were obtained when the lower

incisor edges lay on the A-Pog line; but he also noted that this does not

indicate a position of stability for these teeth (Rickett) but Houston

disagree.


cephalometrics by almuzian ok ok

Health & Medicine

errors of identification

airway assessment

reliability of cephalometric

naiommla demmahompage

types of projectional

treatment decisions

end of treatment

correct head position