INDIAN DENTAL ACADEMY
Leader in continuing dental education
Cephalometrics has given us a different
prespective of interpreting various skeletal
problems in the dentofacial complex.
However, the promise of the cephalometrics as
a diagnostic and prognostic tool is yet to be
Limitations of cephalometry:
Errors of projection:
Errors of identification
Unpredictability of growth
Limitations in suerimpositioning methodswww.indiandentalacademy.com
Errors due to
1.use of intracranial reference planes
2.patient positioning in the cephalostat
Intracranial reference planes:
Indv. variations in
reference lines -
Variations in the reln. bet. reference lines -
different evaluation of facial skeletal
Does not always reflect the clinical
appearance of the individual subject.
First orientation plane to orient cranium
on a horizontal from the middle of EAM
Sella- Nasion Plane :
Antero posterior extent of ant. cranial base.
Steiner – the S & N points move only
minimally when head deviates from the true
profile position & even when head is rotated
in the cephalostat
Inclination of SN plane:
Bjork AO 1951 – earliest to report unreliability
Drawbacks of S-N plane:
Mcnamara AO 1981 – Cephalometric
maxillary retrusion in cl.II cases is due to low
inclination of the skull base
The anterior skull base (S-N) is unstable in
• Nasion - landmark on an actively growing suture,
- moves forward, upward, or downward in
• Sella- its geometric center is unstable since the
pituitary gland enlarges during growth.
• The S-N line may therefore rotate
slightly over time - results in a
considerable back or forward swing of
Sella is totally unrelated to the structures of
the face and therefore cannot be used to
measure facial development
( ELLIS & MC NAMARA)
Frankfort horizontal plane
The plane through left and right porion and left
orbitale , (in 1884 by craniologists), - the best
compromise for orientation of crania.
Drawbacks of FH plane:
Downs(1956) - the discrepancies between
Cephalometric and photographic facial
typing disappear when a correction is made
for those persons in whom the "Frankfurt
plane" is not horizontal.
Drawn thru’ the region of overlapping cusps
of I premolar & I molars (Jacobson Wit’s
• To eliminate the effect of rotation of the
• Variation in the A-P relation of the jaws
with respect to cranium
• Affected by occlusal plane angle & vertical
• Affected by vertical distance between points
A & B
• Any change in occlusal plane during treatment
• Growth related changes cannot be determined
Patient positioning in a
Patient aligned within ear rods of the
cephalostat exerting moderate pressure on
Patient’s FH placed parallel to the floor
canthomeatal line placed 10 degrees to floor
Locking nasal positioner against bridge of
Disadvantage of ear rods:
Greenfield et.al. AJO 1989
Fixed position of cephalostat - cannot be
adjusted forward, backward, sidewise, or
- The subject moves his head to fit the ear
rods, ( altering the angulation of the
head and neck ).
If the transmeatal axis is not perpendicular
to the midsagittal plane- immobilization of
the head with ear rods introduces asymmetry
Moorrees and Kean(1958).
AJO 1994 Moorrees
- A standardized and reproducible
position of the head, in an upright
posture, the eyes focused on a point in the
distance at eye level, which implies that
the visual axis is horizontal.
Advantages of NHP:
It provides the use of an extracranial
reference line (true vertical or horizontal) for
NHP should be the preferred for profile
evaluation as it reflects the everyday true
life appearance of people.
The natural head position is relatively
constant over time.
(MOORREES &KEAN 1958)
Facial photograph and cephalometric
radiograph in NHP - direct correlation bet.
real-life appearance and tracing.
Natural head posture:
Developed by Molhave for studying the
biodynamics of the human body.
Natural head posture is a physiologic
position -"orthoposition" - characteristic for a
person and reproducible, but differs among
defined as a small range of positions
oscillating around the subject's mean NHP.
(Lundstrom EJO 1991)
Head posture is a dynamic concept and
ideally its measuration should be performed
in a dynamic and continuous manner.
Postural control of the head is influenced by
Resistance to gravity
Sight (visual axis)
Vestibular balance mechanism
For Cephalometric analysis, the
standardized NHP is preferable to
natural head posture
―The momentary interim position when
taking the first step forward from a
standing to a moving or walking posture.―
Ortho position is the most reproducible
habitual symmetrical standing position.
Solow and Tallgren
NATURAL HEAD ORIENTATION:
― The head orientation of the subject perceived
by the clinician, based on general
experience, as the NHP in a
standing, relaxed body and head
posture, when the subject is looking at a
distant point at eye level.‖
Lundström and Lundström AJO1995
The NHO related horizontal line
standardized to a line through Sella is the
best reference for clinical cephalometric
analysis when head positions registered at
NHP are unnaturally flexed
Readily registered by instructing the subject
standing or sitting in the cephalostat to look
at a point on the wall in front, exactly at
A small mirror (diameter no more than 10
cm), the midpoint of which also at eye
level, can be used also for head orientation.
•The wire plumb line –
record the true vertical
Plumb line bisects the
reflection of the subject's
face in the mirror and
minimize lateral head
The location of the central
x-ray beam -determined by
a projected light cross
standardized by the
plumb line bisecting the
reflection of the subject's
face in the mirror.
To prevent the swaying , define the feet
position as "a comfortable distance
apart and slightly diverging―
• Patients placed facing a neutral wall (nothing
to distract ).
• Carefully observe the patient's posture before
the actual rehearsal takes place,
• The patient walks from the waiting area to the
Mølhave(1958) -the most reproducible natural
standing position is the orthoposition
Small children - to place heels together and let
the arms hang.
Older and tense patients - "walk on the spot''
& to raise and drop shoulders to ease
HEAD POSTURE. - two methods
The subject's own feeling of a natural
head position ―the self-balance position.‖
Based on visual cues from external
Positioning according to external reference -
carried out only after the head has been
placed in the self-balance position.
In adults the head is kept, on the average, 3
degrees higher in the mirror position than in
the self-balance position.
If the earrods are not
aligned, place the
operator’s foot in front
of or behind the patient's
feet and ask the patient
to move slightly until he
hits the operator's foot
Patient instructed to
''hold your head so that
you can look into your
own eyes in the miror".
carried out with guidance
by the light-beam cross
THE FLUID LEVEL DEVICE
AJO 1983 Showfety et.al
The ends of the air bubble aligned with the
ends of an 0.030 inch diameter wire
The fluid consists of a mixture of radiopaque
liquid, blue dye, and a silicone suspension,
rendering the air bubble visible on the
The ideal location - between the eyebrow and
the hairline behind the prominent temporal
crest of the frontal bone.
The patient instructed to stand in an ''intention
The fluid level is rotated on the pivot until the
bubble is aligned with the ends of the wire.
The patient is placed in the cephalometric head
holder & the patient's head is tilted up or
down until the bubble is aligned with the
A vertical reference chain & wire in the fluid-
level device will be aligned at 90 degrees to
AJO 1991 Murphy et.al.
uses a contactless precision potentiometer to
continuously measure changes in inclination
around a single axis of rotation
the inclinometer was calibrated
Spectacles attach the inclinometer to the
head in a stable manner .
AJO1985 Archer and Vig
Leveling device consisting
of a fluid-filled plastic
ring mounted on a
• Schmidt (1876) made use of a frame that encircled
the skull, a plumb line and a protractor.
• Moorrees and Kean projected the image of a plumb
line of stainless steel ligature wire onto
• Von Baer and Wagner instructed subjects to look
directly at the reflection of their eyes on a a mirror
fixed to a wall.
• Cinefluorography may be used to measure
head posture over a period but exposes
subjects to irradiation for relatively long
periods.(Cleall et.al., AO 1966)
Importance of NHP:
(Solow and Kreiborg 1977)
―Soft tissue stretching hypothesis''
Head extension - stretch of the soft tissues
- increase in the forces of the lips and
other faciocervical muscles .
Extended head posture –
Retroclination of lower incisors
AFH and PFH
A-P craniofacial dimension
Larger inclination of the mandible to SN
Larger cranial base angle
Small nasopharyngeal space
SOLOW & TALLGREN 1976
• Woodside and Linder-Aronson(EJO1976)
- children with nasal obstruction had a more
extended head posture(6°) .
• Extended head posture after induced mouth
breathing - Hellsing et.al.,(EJO1987)
• Oral respiration - produce an altered
mandibular posture and changes in the shape
of the mandible with development of an
anterior open-bite (Harvold et.al.,1973)
Dentoalveolar height and occlusal plane
inclination showed a set of positive
correlations with the craniocervical and sella
-nasion to vertical angulations
(SOLOW &TALLGREN 1977)
Goldstein and associates(1984)
Evaluated the mandibular trajectory of
closure with a mandibular kinesiograph
Four postural attitudes: natural sitting
posture (NP), forward head posture
(FHP), maximal forward head posture
(MFHP), and military posture (MP).
• Alterations of the A-P head and neck posture
have an immediate effect on the trajectory of
• As the head moved anteriorly - the vertical
distance of mandibular closure decreased.
• When the head moved posteriorly - the
anterior excursion of the mandible through
the interocclusal space decreased.www.indiandentalacademy.com
DESCRIPTION OF HEAD AND NECK
POSITION ON THE RADIOGRAPH
NSL/OPT - represent tilting of the head at
OPT/CVT -represent change in cervical
OPT/HOR & CVT/HOR- Cervical
inclination in relation to the true horizontal
NSL/VERT -the total change in head
Large craniocervical angle- an extension of the
head -the height of the posterior arc of the
atlas is reduced
-Also related to adenoid airway obstruction
and a vertical facial development
(Huggare et.al., EJO 1985)
Various analysis using
Reference planes in NHP:
Down’s & Tweed-
Drop perpendicular thru’ Orbitale
Test difference between true horizontal & FH
& include in the analyses
Bjork & Steiner-
Draw horizontal thru’ nasion
S-N made 10 degrees to horizontal
Growth prediction from posture
Solow & Nielson AJO 1992
41 reference points and 4 fiducial points
Points N and S on the first film - fiducial
points in the anterior cranial base- REFcrb.
In the mandible - fiducial points located
arbitrarily in the middle of the symphysis and
one below the first molars- REFml.
A backward inclination of the cervical column
& small craniocervical angle
reduced backward displacement of TMJ
increased growth in maxillary length,
increase in max. and mand. prognathism,
forward true rotation of the mandible .
Upright position of the cervical column &
large craniocervical angle
large backward displacement of TMJ
reduced growth in maxillary length
reduction of max.and mand. Prognathism
less forward true rotation of the mandible
A small craniocervical angle was associated
with a horizontal facial growth pattern
A large craniocervical angle was associated
with a vertical facial development.
Horizontal line Reference-
drawn parallel to the border of the radiograph
constructed at right angles to the registered true
drawn in any vertical position.
BEST -close to the Frankfort plane
Cooke and Wei AJO 1988
Angle 1 - anteroinferior angle bet. Y axis &
Angle 2 - angle bet. upper incisor & true
Angle 3 - NHP equivalent of the facial angle
Angle 4 - angle bet. AB line & true
Angle 5 - angulation of the lower incisor &
"Normal" AB/horizontal values for clinical use
Skeletal Class I 12° to 18°
Skeletal Class II > 18°
Skeletal Class III < 12°
Requires no new sets of "norms" or figures.
Only the reference plane has been changed
to eliminate the errors inherent in analyses.
Conventional methods are subject to errors
in describing true life appearance.
Normal - focus on the profile from the nose
The A-P position of the forehead -not a major
The size of the nose -alter clinician's
impression of the convexity of the profile &
the position of the lips.
A new measurement of profile
esthetics JCO, 1991 VIAZIS
A line drawn through
the middle of the nose
(No), parallel to the true
vertical- the ― V‖ line.
The ― V‖ angle - the
angle between this line
and Steiner's ― S‖ line.
for adults - -12.5°
for adolescents -13.0 °
FCA - -8° indicates
― E‖ line I- retrusive
― V‖ angle - -11° in
clinical impression of
Cephalometric Analysis based on
NHP: JCO 1991 VIAZIS
Defines the A-P & vertical position of the
maxilla and mandible relative to the true
horizontal plane, then relates the position of
the dentition to its skeletal substrate.
Only two soft-tissue measurements.
No linear measurements.
Comprehensive Assessment of
Anteroposterior Jaw Relationships
Describe an assessment of the
anteroposterior position of the jaws based
on measurements that use TH as their
Size of Mand. relative to Ant. Cranial Base (SN-
Maxillomandibular Ratio (PNS-ANS:ArGn)
Linear and Angular Measurements (A, B, Pg to
N^TH; NA, NB, NPg to TH)
Relative A-P Position ( TH Wits & ANB)
Anteroposterior Chin Position (Chin Length and
1. Size of Mandible Relative to Anterior
Cranial Base (SN-GoGn)
1:1 ratio -indicate a
relative to the cranial
base . SN should be 0-
5mm greater than GoGn
before puberty, and
about 0-5mm less than
GoGn after puberty.
2. Maxillomandibular Ratio (PNS-
The length of the
mandible is exactly
double the length of
the maxilla for all age
groups and both sexes
3. Linear and Angular Measurements (A,
B, Pg to N^TH; NA, NB, NPg to TH)
Three linear measurements— from A, B,
and Pg to nasion perpendicular to TH
The angles between NA and NPg and TH -
evaluate the anteroposterior position of the
jaws . NB provides an additional
4. Relative Anteroposterior Position (TH
Wits and ANB) Points A and B
TH, (a and b). The
distance ab - "TH
Wits‖ - provides a
clearer picture of the
relationship of the
Optic plane: SASSOUNI
the supraorbitale plane (a line tangent to
anterior clinoid and the roof of the orbit)
the infraorbital plane (line tangent to the
inferior of sella turcica and the floor of the
bisect the angle formed by their intersection
- the optic plane
Natural head position in
Camera - mounted on a tripod & leveled with
the optical axis of the lens horizontal and the
film plane vertical.
20 × 100 cm mirror mounted at eye level on the
Subject – camera –150 cm 2.55 m.
Mirror- subject – 120cm.
Recording of NHP:
Assume and maintain a "natural and normal"
erect posture of head and shoulders, with
both arms hanging free beside the trunk.
On each photograph, a reference line placed
perpendicular to the ground by using a small
spirit level (true vertical) was drawn.
AJO 1994 Ferrario et.al.,
Developed a photographic technique -
associated with standard radiograph &
a computerized method allowing an easy
and fast superimposition of the two
recordings was introduced
the angle between the N'-Pg' line and the true
vertical was calculated on the photograph &
The difference - compute the position of the
soft and hard tissue Frankfurt planes, and of
the sella-nasion plane in NHP.
These new values were compared with the
values observed in the standard cephalometric
Angle N'-Pg' line/true
vertical was fed to a
computer program -
provided a rotation of all
the landmarks until the
cephalometric N'-Pg' line
coincided with the
Rotation was performed around the
Craniofacial morphometry by
AJO 1993 –Ferrario et.al.
Frontal standing, rest & clenching a Fox plane
Lateral standing, rest &clenching a Fox plane
Lateral sitting, rest
16 points were located by careful inspection &
palpation and traced on the face of each
Face center of gravity (CG) coordinates--- used as
the new origin of coordinate axes - the points
on the frontal image using the areas of eyes ,nose
on the lateral image as center of the polygon N-
In the frontal plot, the N-CG axis -used as a new
reference y-axis - points were rotated.
DISADVANTAGE OF NHP
AJO 1980 Frankel
Functional appliance treatment- changes in
posture ( functional and physiologic)- distorts data
Fu.A. alters muscle form and function. Adjoining
muscle groups experience reciprocal changes and
treatment-related head posture changes could
Did not consider NHP modifications
during treatment, but proposed to refer all
longitudinal radiograms to the first NHP
recording – missed the important
information. Ferrario et.al., AJO 1994
― THE SEARCH FOR AN IDEAL‖
-Cephalometrics is constantly undergoing
refinements in its techniques & analyses to
improve the clinical applications. NHP , a
long proposed modification, yet not fully into
practice, can be an ―ideal‖ reference for us to
improve our cephalometric interpretation……