Natural Head Position / orthodontic courses by Indian dental academy

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INTRODUCTION:INTRODUCTION: Cephalometrics has given us a Cephalometrics has given us a

different prespective of interpreting different prespective of interpreting various skeletal problems in the various skeletal problems in the dentofacial complex. However, the dentofacial complex. However, the promise of the cephalometrics as a promise of the cephalometrics as a diagnostic and prognostic tool is yet diagnostic and prognostic tool is yet to be fulfilled.to be fulfilled.


Limitations of cephalometry:Limitations of cephalometry: Errors of projection:

MagnificationDistortion

Errors of identificationRadiograph quality

Reproducibility Unpredictability of growth Limitations in suerimpositioning

methods www.indiandentalacademy.com

Errors due to1.use of intracranial

reference planes2.patient positioning in

the cephalostatwww.indiandentalacademy.com

Intracranial reference planes: Indv.

variations in reference lines - different interpretation of subjects with similar profiles. www.indiandentalacademy.com

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:CAMPER’S LINE:

First orientation plane to orient cranium on a horizontal from the middle of EAM to ANSwww.indiandentalacademy.com

Sella- Nasion Plane :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:Inclination of SN plane:Bjork AO 1951Bjork AO 1951 – earliest to

report unreliability

Drawbacks of S-N plane:

Downward- Downward- facial angles facial angles decrease decrease Upward- Upward- facial angles facial angles increaseincrease


Mcnamara AO 1981Mcnamara 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 growth.


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


Sella is totally unrelated to the

structures of the face and

therefore cannot be used to

measure facial development( ELLIS & MC NAMARA)( ELLIS & MC NAMARA)


Frankfort horizontal planeFrankfort 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)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.



Anatomical location of porionMachine porionAnatomic porion

Individual variation

Vertical relationships with other intracranial landmarks – biologic variation



Occlusal plane: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: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 Patient positioning in a cephalogram: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

Locking nasal positioner against bridge of nosewww.indiandentalacademy.com


Disadvantage of ear rods:Disadvantage of ear rods: Greenfield et.al. Greenfield et.al.

AJO 1989AJO 1989 Fixed position of cephalostat -

cannot be adjusted forward, backward, sidewise, or rotated.

- The subject moves his head to fit the ear rods, ( altering the angulation of the head and neck ).


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



Definition :AJO 1994 MoorreesAJO 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: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 people. (COOKE 1986)(COOKE 1986)www.indiandentalacademy.com


The natural head position is relatively constant over time..

(MOORREES &KEAN (MOORREES &KEAN 1958)1958)

Facial photograph and Facial photograph and cephalometric radiograph in cephalometric radiograph in NHP - direct correlation bet. NHP - direct correlation bet. real-life appearance and tracing.real-life appearance and tracing.


Natural head posture:Developed by MolhaveMolhave 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 persons.


defined as a small range of positions oscillating around the subject's mean NHP.

(Lundstrom EJO 1991) 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 Respiration Deglutition

Sight (visual axis) Vestibular balance mechanism

Hearingwww.indiandentalacademy.com

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

(MOORREES)(MOORREES)


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 standing position.

Solow and TallgrenSolow and Tallgren www.indiandentalacademy.com

NATURAL HEAD ORIENTATION:

“ “ The head orientation of the The head orientation of the subject perceived by the subject perceived by the clinician, based on general clinician, based on general experience, as the NHP in a experience, as the NHP in a standing, relaxed body and head standing, relaxed body and head posture, when the subject is posture, when the subject is looking at a distant point at eye looking at a distant point at eye level.”level.”


Lundström and Lundström and Lundström AJO1995 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 eye level.

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 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)(Cooke 1986)


Solow & TallgrenSolow & Tallgren Acta Odontol. Scand. 1971


REHEARSAL PHASE: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)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 tension.


HEAD POSTURE. - two methods (SOLOW 1971)(SOLOW 1971) The subject's own feeling of a

natural head position “the self-balance position.”

Based on visual cues from external reference


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

POSITIONING OF THE FEET.


BODY-POSITIONING & BODY-POSITIONING & HEAD-POSITIONINGHEAD-POSITIONING.

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

ADJUSTMENT FOR ADJUSTMENT FOR SYMMETRY. SYMMETRY.

carried out with guidance by the light-beam cross


THE FLUID LEVEL DEVICE AJO 1983 AJO 1983 Showfety et.alShowfety et.alThe 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 cephalometric radiograph.





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 fluid level is rotated on the pivot until the bubble is aligned with the ends of the wire.

PROCEDURE:


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 at 90 degrees to each other



Inclinometer AJO 1991 AJO 1991 Murphy et.alMurphy et.al.uses a contactless precision

potentiometer to continuously measure changes in inclination around a single axis of rotation

the inclinometer was calibratedSpectacles attach the inclinometer

to the head in a stable manner .www.indiandentalacademy.com



AJO1985 Archer and VigAJO1985 Archer and Vig

Wood 1981

Leveling device consisting of a fluid-filled plastic ring mounted on a protractor.


Other methods:• Schmidt (1876)Schmidt (1876) made use of a frame

that encircled the skull, a plumb line and a protractor.

• Moorrees and KeanMoorrees and Kean projected the image of a plumb line of stainless steel ligature wire onto cephalometric radiographs

• Von Baer and WagnerVon 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) .(Cleall et.al., AO 1966)


Importance of NHP: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 – Facial retrognathism Retroclination of lower incisors AFH and PFH A-P craniofacial dimension Larger inclination of the mandible

to SN Larger cranial base angleSmall nasopharyngeal space

SOLOW & TALLGREN 1976SOLOW & TALLGREN 1976


RESPIRATION &NHP• Woodside and Linder-Woodside and Linder-

Aronson(EJO1976)Aronson(EJO1976) - children with nasal obstruction had a more extended head posture(6°) .

• Extended head posture after induced mouth breathing - Hellsing Hellsing et.al.,(EJO1987)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 (Harvold et.al.,1973)et.al.,1973)


Nasal obstruction

Craniocervical postural adaptations

Mandibular postural adaptation

Skeletal growth modification

Dentoalveolar compensation/adaptation


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

(SOLOW &TALLGREN (SOLOW &TALLGREN 1977)1977)


Goldstein and Goldstein and associates(1984)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). www.indiandentalacademy.com

• 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 - the anterior excursion of the mandible through the interocclusal space decreased.


DESCRIPTION OF HEAD AND NECK DESCRIPTION OF HEAD AND NECK POSITION ON THE RADIOGRAPHPOSITION 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 head position


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., (Huggare et.al., EJO 1985)EJO 1985) www.indiandentalacademy.com

Various analysis Various analysis using NHP:using NHP:


Reference planes in NHP:Reference planes in NHP:Down’s & Tweed-Down’s & Tweed-Drop perpendicular thru’ Orbitale Test difference between true

horizontal & FH & include in the analyses

Bjork & Steiner-Bjork & Steiner-Draw horizontal thru’ nasionS-N made 10 degrees to horizontal


Growth prediction from postureGrowth 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 www.indiandentalacademy.com

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

A large craniocervical angle was associated with a vertical facial development.


Five-factor cephalometric Five-factor cephalometric summary analysissummary analysis

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

Cooke and Wei AJO 1988



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 incisor & true horizontal.


"Normal" AB/horizontal values for clinical use

Skeletal Class I 12° to 18°

Skeletal Class II > 18°

Skeletal Class III < 12°www.indiandentalacademy.com

AdvantagesAdvantages::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. www.indiandentalacademy.com

Normal - focus on the profile from 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 new measurement of profile A new measurement of profile estheticsesthetics JCO, 1991 JCO, 1991

VIAZISVIAZIS



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 ° www.indiandentalacademy.com

FCA - + 3° prognathic

“ E” line -normal lower lip

V” angle - -1.5° -supports clinical impression of prognathic profile .


FCA - -8° indicates retrognathic profile.

“ E” line I- retrusive

“ V” angle - -11° in accordance with clinical impression of orthognathic profile.


Cephalometric Analysis based on Cephalometric Analysis based on NHP:NHP: JCO 1991 JCO 1991 VIAZIS 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 Comprehensive Assessment of Anteroposterior Jaw RelationshipsAnteroposterior Jaw Relationships JCO1992 JCO1992 VIAZISVIAZIS

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


Size of Mand. relative to Ant. Cranial Base (SN-GoGn)

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 BNPg)


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 puberty.


2. Maxillomandibular Ratio (PNS-ANS:ArGn)

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 assessmentwww.indiandentalacademy.com


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 the mandible


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: SASSOUNIthe 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 intersection - the optic plane


Natural head position Natural head position in photographsin photographs


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.

Mirror- subject – 120cm.

Recording of NHP: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.,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 & 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 with the values observed in the standard cephalometric orientation.


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 photographic one. Rotation was performed Rotation was performed around the Bolton pointaround the Bolton point


Craniofacial morphometry by Craniofacial morphometry by photographic evaluationphotographic evaluation

AJO 1993 –Ferrario et.al.AJO 1993 –Ferrario et.al.Frontal standing, rest & clenching a Fox plane Lateral standing, rest &clenching a Fox planeLateral sitting, rest16 points were located by careful

inspection & palpation and traced on the face of each subject


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 gonion .www.indiandentalacademy.com


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 -used as a new reference y-axis - points were rotated.




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

AO 1992




DISADVANTAGE OF NHP AJO 1980 AJO 1980 FrankelFrankel

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 Did not consider NHP modifications during modifications during treatment, but proposed to treatment, but proposed to refer all longitudinal refer all longitudinal radiograms to the first NHP radiograms to the first NHP recording – missed the recording – missed the important information. important information.

Ferrario et.al., AJO Ferrario et.al., AJO 19941994www.indiandentalacademy.com

CONCLUSION:CONCLUSION: “ “ THE SEARCH FOR AN IDEAL”THE SEARCH FOR AN IDEAL” -Cephalometrics is constantly

undergoing refinements in its techniques & analyses to improve the clinical applications. NHP NHP , a long proposed modification, yet not fully into practice, can be an “ideal” reference for us to improve our cephalometric interpretation……




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