Natural head position /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


INTRODUCTION:
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

Limitations of cephalometry:
 Errors of projection:
Magnification
Distortion
 Errors of identification
Radiograph quality
Reproducibility
 Unpredictability of growth
 Limitations in suerimpositioning

Errors due to
1.use of intracranial reference
planes
2.patient positioning in the
cephalostat

Intracranial reference planes:
 Indv.
variations in
reference lines different
interpretation
of subjects with
similar profiles.

 Variations in the reln. bet.
reference lines - different evaluation
of facial skeletal pattern
 Does not always reflect the clinical
appearance of the individual
subject.


CAMPER’S LINE:
First orientation plane to orient
cranium on a horizontal from the
middle of EAM to ANS

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 &

Drawbacks of S-N plane:
 Inclination of SN plane:
Bjork AO 1951 – earliest to report
unreliability
Downward- facial
angles decrease
Upward- facial
angles increase

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 growing persons.
• Nasion - landmark on an actively
growing suture, - moves forward,
upward, or downward in growing
children
• Sella- its geometric center is unstable
since the pituitary gland enlarges during

• The S-N line may therefore
rotate slightly over time results in a considerable back or
forward swing of the chin.

 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

 Anatomical location of porion
Machine porion
Anatomic porion
 Individual variation
 Vertical relationships with other
intracranial landmarks – biologic

Occlusal plane:

 Drawn thru’ the region of
overlapping cusps of I premolar & I
molars (Jacobson Wit’s Appraisal)
• To eliminate the effect of rotation
of the jaws
• Variation in the A-P relation of the
jaws with respect to cranium

Disadvantages:
• Affected by occlusal plane angle &
vertical alveolar relationships
• Affected by vertical distance
between points A & B


• Any change in occlusal plane during
treatment allows variation
• Growth related changes cannot be
determined

Patient positioning in a
cephalogram:
 Patient aligned within ear rods of
the cephalostat exerting moderate
pressure on EAM.
 Patient’s FH placed parallel to the
floor canthomeatal line placed 10
degrees to floor

Disadvantage of ear rods:
Greenfield et.al.
AJO 1989
 Fixed position of cephalostat cannot be adjusted forward,
backward, sidewise, or rotated.
- The subject moves his head to fit

 If the transmeatal axis is not
perpendicular to the midsagittal
plane- immobilization of the head
with ear rods introduces asymmetry
Moorrees and Kean(1958).

Definition :

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
cephalometric analysis.
 NHP should be the preferred for
profile evaluation as it reflects the
everyday true life appearance of

 The natural head position is
relatively constant over time .
(MOORREES
&KEAN 1958)
 Facial photograph and
cephalometric radiograph in NHP direct correlation bet. real-life

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

Postural control of the head is
influenced by
 Resistance to gravity
 Respiration
 Deglutition
 Sight (visual axis)
 Vestibular balance mechanism

For Cephalometric
analysis, the standardized
NHP is preferable to
natural head posture

Ortho position:
 “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

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.”

The NHO related horizontal line
standardized to a line through
Sella is the best reference for
clinical cephalometric analysis
when head positions registered at
Lundström and Lundström
NHP are unnaturally flexed
AJO1995

 Readily registered by instructing
the subject standing or sitting in
the cephalostat to look at a point
on the wall in front, exactly at eye
level.
 A small mirror (diameter no more
than 10 cm), the midpoint of which
also at eye level, can be used also

•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 rotation.

The location of the
central x-ray beam
-determined by a
projected light cross
("+").
Magnification
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“

(Cooke 1986)


Solow & Tallgren
Acta Odontol.
Scand. 1971


REHEARSAL PHASE:
• 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 radiographic room.

 BODY POSTURE.
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

HEAD POSTURE . - two methods
(SOLOW 1971)
 The

subject's own feeling of a

natural head position “the selfbalance position.”
 Based

on visual cues from

 Positioning according to external
reference - carried out only after the
head has been placed in the selfbalance position.
 In adults the head is kept, on the
average, 3 degrees higher in the

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

POSITIONING OF
THE
FEET.


BODY-POSITIONING
& HEADPOSITIONING .

Patient instructed
to ''hold your head
so that you can
look into your own
eyes in the miror".
ADJUSTMENT FOR
SYMMETRY.

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

PROCEDURE:
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 position”.

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
wire.
A vertical reference chain & wire in
the fluid-level device will be aligned

Inclinometer
et.al.
et.al

AJO 1991 Murphy

 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

AJO1985 Archer and Vig
Wood 1981
Leveling device
consisting of a fluidfilled plastic ring
mounted on a
protractor.

Other methods:
• 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 cephalometric radiographs
• Von Baer and Wagner instructed subjects
to look directly at the reflection of their

• 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

SOLOW & TALLGREN 1976
Extended head posture –
Facial retrognathism
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

RESPIRATION &NHP
• Woodside and LinderAronson(EJO1976)

-

children with nasal obstruction had
a more extended head posture(6°) .
• Extended head posture after induced
mouth breathing - Hellsing et.al.,

• Oral respiration - produce an altered
mandibular posture and changes in
the shape of the mandible with
development of an anterior openbite (Harvold et.al.,1973)

Nasal obstruction
Craniocervical postural
adaptations
Mandibular postural adaptation
Skeletal growth modification

Dentoalveolar height and occlusal
plane inclination showed a set of
positive correlations with the
craniocervical and sella -nasion to
vertical angulations
(SOLOW

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

• Alterations of the A-P head and
neck posture have an immediate
effect on the trajectory of
mandibular closure.
• As the head moved anteriorly - the
vertical distance of mandibular
closure decreased.
• When the head moved posteriorly www.indiandentalacademy.com

DESCRIPTION OF HEAD AND NECK
POSITION ON THE RADIOGRAPH
SOLOW
&TALLGREN(1976)


 NSL/OPT - represent tilting of the
head at occipitoatloid joint
 OPT/CVT -represent change in
cervical curvature
 OPT/HOR & CVT/HOR- Cervical
inclination in relation to the true
horizontal
 NSL/VERT -the total change in

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


Various analysis using
NHP:


Reference planes in NHP:
Down’s & TweedDrop perpendicular thru’ Orbitale
Test difference between true
horizontal & FH & include in the
analyses

Bjork & SteinerDraw 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

A backward inclination of the
cervical column & small
craniocervical angle


reduced backward displacement of
TMJ



increased growth in maxillary
length,


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


 A small craniocervical angle was
associated with a horizontal facial
growth pattern

 A large craniocervical angle was
associated with a vertical facial

Five-factor cephalometric
summary analysis

Cooke and Wei AJO 19

Horizontal line Reference-

 drawn parallel to the border of the
radiograph constructed at right angles
to the registered true vertical.
 drawn in any vertical position.

 BEST -close to the Frankfort plane

Angle 1 - anteroinferior angle bet. Y
axis & true horizontal.
Angle 2 - angle bet. upper incisor &
true horizontal.
Angle 3 - NHP equivalent of the
facial angle
Angle 4 - angle bet. AB line & true
horizontal.
Angle 5 - angulation of the lower

"Normal" AB/horizontal values for
clinical use


Skeletal Class I 12° to 18°



Skeletal Class II

> 18°



Skeletal Class III

< 12°


Advantages:
 Requires no new sets of "norms" or
figures.
 Only the reference plane has been
changed to eliminate the errors
inherent in analyses.

A new measurement of profile
esthetics
JCO, 1991

 Normal - focus on the profile from
VIAZIS
the nose down
 The A-P position of the forehead
-not a major factor
 The size of the nose -alter clinician's
impression of the convexity of the
profile & the position of the lips.

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.

FCA - + 3°
prognathic
“ E” line -normal
lower lip
V” angle - -1.5°
-supports clinical
impression of

FCA - -8°
indicates
retrognathic
profile.
“ E” line Iretrusive
“ V” angle - -11°
in accordance


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.

Comprehensive Assessment of
Anteroposterior Jaw Relationships
JCO1992
VIAZIS

Describe an assessment of the
anteroposterior position of the
jaws based on measurements that
use TH as their reference line.

 Size of Mand. relative to Ant. Cranial
Base (SN-GoGn)
 Maxillomandibular Ratio (PNSANS:ArGn)
 Linear and Angular Measurements (A,
B, Pg to N^TH; NA, NB, NPg to TH)
 Relative A-P Position ( TH Wits &
ANB)

1. Size of Mandible Relative to Anterior
Cranial Base (SN-GoGn)

 1:1 ratio -indicate
a well-balanced
mandible relative to
the cranial base .
SN should be 0-5mm
greater than GoGn
before puberty, and
about 0-5mm less
than GoGn after


2. Maxillomandibular Ratio (PNSANS:ArGn)

 The length of the
mandible is
exactly double the
length of the
maxilla for all age
groups and both

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

4. Relative Anteroposterior Position (TH
Wits and ANB)
 Points A and B

projected on
perpendiculars to
TH, (a and b). The
distance ab - "TH
Wits” - provides
a clearer picture of
the anteroposterior
relationship of the
jaws


5. Anteroposterior Chin Position
(Chin Length and BNPg)

 The BNPg
angle
assesses the
prominence
of the chin
relative to
the body of

 Projections of B
and Pg to a line
parallel to TH
and tangent to
the mandible at
menton define
the chin length,bp


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 orbit)
 bisect the angle formed by their

Natural head position in
photographs


Recording of NHP:
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 wall
Subject – camera –150 cm 2.55 m.

 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

AJO 1994 Ferrario et.al.,
Developed a photographic
technique - associated with
standard radiograph & a
computerized method allowing
an easy and fast superimposition

 the angle between the N'-Pg' line
and the true vertical was calculated
on the photograph & cephalometric
films
 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

 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
Rotation was performed
the Bolton point
the photographic

around

Craniofacial morphometry by
photographic evaluation
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

 Median

points -soft tissue nasion
,nasal apex ,soft tissue subnasale
,upper lip ,lower lip ,soft tissue
pogonion .

 Lateral

points - supraorbital
foramen , infraorbital foramen ,
soft tissue orbitale , soft tissue

 Face center of gravity (CG)
coordinates--- used as the new origin of
coordinate axes - the points were
translated.
on the frontal image using the areas of
eyes ,nose and mouth
on the lateral image as center of the
polygon N-Pog-Go-Tr
 In the frontal plot, the N-CG axis

A proportional analysis of the soft
tissue facial profile
Lundström et.al, AO
1992


DISADVANTAGE OF NHP
AJO 1980
Frankel
 Functional appliance treatment- changes
in posture ( functional and physiologic)distorts data base
 Fu.A. alters muscle form and function.
Adjoining muscle groups experience
reciprocal changes and treatment-related
head posture changes could result.

Did not consider NHP
modifications during treatment,
but proposed to refer all
longitudinal radiograms to the
first NHP recording –et.al., AJOthe
Ferrario missed 1994

CONCLUSION:
“ 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

Natural head position /certified fixed orthodontic courses by Indian dental academy

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