Functional & ceph analysis for functional appliance /certified fixed orthodontic courses by Indian dental academy

FUNCTIONAL & CEPH ANALYSIS
FOR FUNCTIONAL APPLIANCE

INDIAN DENTAL ACADEMY
Leader in continuing dental education

www.indiandentalacademy.com

Introduction
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Functional examination is of special significance in
treatment of functional appliances because of dynamic
basis of therapy,
An initial functional assessment is imperative
Function is ,indeed, the common denominator that joins
the individual parts of the orofacial system into a
dynamic,integrated and purposive system
Disturbance in one part of the orofacial system do not
remain isolated but affect the equilibrium of the whole
system
This unique quality is of importance in etiological
considerations and when assessing the effectiveness and
various side effects of different orthodontic appliance

Proper treatment plan and prognosis depends on accurate diagnosis.Any
abnormal function which is detected should be corrected for favourable
treatment outcome.

Three most important aspects of orthodontic functional analysis are:
1.Examination of postural rest position and maximum intercuspation
2.Examination of the TMJ
3.Examination of orofacial dysfunction


Examination of the relationship : Postural rest
position – Habitual occlusion
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Determination of the postural rest position
Registration of postural rest position
Evaluation of the relationship: Postural rest position –
Habitual occlusion in 3 planes of space
The rest position should be determined with the patient relaxed
and sitting upright.The head is oriented by having the patient
look straight ahead (habitual position). If this seems too
variable, then the head can be positioned with the frankfurt
horizontal parallel to the floor.


Determination of postural rest position
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Patient’s orofacial musculature must be relaxed
Muscle exercises to relax the musculature – “ TAPPING TEST”
If patient is tensed – mild electric impulses to relax the
musculature

When the mandible is in the postural resting position,it
is usually 2-3mm below and behind the centric
occlusion,recorded in canine area


Methods used to determine the rest position during clinical
examination
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Phonetic method
Command method
Non-command method
Combined method
Phonetic method:
Patient is told to pronounce certain consonants or words repeatedly
(e.g.”M”,”Mississippi”).The mandible returns to the postural resting position
1-2 seconds after the exercise

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Command method:
The patient is “commanded” to perform selected
functions(e.g.Swallowing),after which the mandible spontaneously returns to
the rest position

Non-command method:
The patient is distracted,so as not to percieve which type of
examination is carried out.while being distracted, the patient
relaxes,causing the musculature to relax as well,and the mandible
reverts to the postural rest position
Combined method:
Most suitable for functional analysis in children.the patient is first
observed during swallowing and speaking.Older children –
tapping test ,then non- command method
• Regardless of the clinical method in use, the mandible must be checked
extraorally to ensure that it actually has assumed the rest positionpalpate the submental region :relaxed muscles in this area indicate that
the rest position has been attained.
• The lips are then carefully parted with the thumb and forefinger – to
observe the maxillomandibular relationship

Registration of the rest position
Two most commonly used methods
 Intra oral indirect method (using impression materials)
 Extra oral direct method (using skin reference points)

Extra oral indirect methods are the most reliable
• Roentgenocephalometric registration
• Kinesiographic registration

Roentgenocephalometric registration
Two cephalograms are required, either in lateral or frontal
projection,
 One radiograph in centric(habitual)occlusion
 One with mandible in its rest position
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The rest position and freeway space can be
determined by comparing the radiographs


Kinesiographic registration
Mandibular kinesiograph,according to Jankelson, allows the mandibular
rest position to be registered 3-D.The position of mandible is
recorded electronically by:
 A permanent magnet, which is fixed with rapid setting acrylic to the
lower anterior teeth
 A sensor system of six magnetometers mounted on spectacle
frames
Every movement of the mandible and the attached magnet out of
centric occlusion, alters the strength of the magnetic field.These
changes are recorded by the sensors , processed in the kinesiograph
and displayed on a storage oscilloscope
The Mandibular movements and rest position are recorded twodimensionally on two preselectable levels.The electronic circuitary
also allows the rest position to be recorded as 3-D co-ordinates

Evaluation of the relationship between rest
position and habitual occlusion
The movement of the mandible from the rest position to full
articulation is analysed three dimensionally:sagittal , vertical and
frontal planes
The closing movements of the mandible can be divided into two
phases
 Free phase:mandibular path from the postural rest to the initial
or premature contact position
 Articular phase:mandibular path from the initial contact position
to centric or habitual occlusion.


When closing from the rest position, the mandible may undergo
both rotational and sliding movements.The objective of this
analysis is to determine the amount and direction of movement
as well as the proportions of the rotational and sliding
components.
The following movements of the mandible from the rest position to
habitual occlusion must be differentiated for orthodontic
diagnosis:
 Pure rotational movement (hinge movement)
 Rotational movement with an anterior sliding component
 Rotational movement with a posterior component


Evaluation in the sagittal plane
When evaluating the relationship of the rest position to habitual occlusion in the
sagittal plane,the exceptional features of the class II and class III malocclusions
are analysed
Class II malocclusion
According to different types of movement of the mandible from the rest position
to occlusion, the classII malocclusion can be divided into 3 types
 Rotational movement without a sliding component-the neuromuscular and
morphologic relationships correspond to each other.There is no functional
disturbance (functional true classII)


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Rotational movement with posterior sliding
movement
The mandible slides backwards and is
guided into a posterior occlusal
position.This finding reveals a functional
class II malocclusion and not a true class II
malrelationship

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Rotational movement with anterior sliding
movement starting from the relatively
posterior rest position
The mandible slides forwards into
habitual occlusion.The class II malocclusion
is actually more pronounced than can be
seen in habitual occlusion

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Treatment prognosis for functional appliance therapy is dependent
on the analysis of the relationships and the determination of the
path of closure category
In functional class II malocclusions,the elimination of the
functional retrusion or protrusion leads to an improvement of the
sagittal relationship
In class II malocclusions with a normal path of closure,the
intermaxillary relationship must be altered,but this requires both a
morphological and a functional change to produce the desired
sagittal correction
In case of posterior displacement,combined with a projected
horizontal growth direction,the prognosis for class II treatment is
very good
When there is an anterior displacement and a vertical growth
vector,the prognosis is poor

Class III Malocclusions
The functional relationships of class III cases determine the orthodontic treatment
possibilities and the prognosis of malocclusion.
The closing path of the mandible from the rest position can be divided into
three types
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Rotational movement without sliding action
The anatomic/morphologic relationships correspond to the functional
relationship (non – functional,true class III malocclusion – unfavourable
prognosis)


Rotational movement with anterior sliding action.
During the articular phase, the mandible shifts forwards and into a prognathic,
forced bite(functional , non skeletal malocclusion , so called pseudo class III –
favourable prognosis)

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Rotational movement with posterior sliding action.
In case with pronounced mandibular prognathism,the mandible may slide
posteriorly into the position of maximum intercuspation.This masks the true
sagittal dysplasia


True forced bite – pseudo –forced bite
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In case of mesio occlusion an anterior sliding action is not always
a symptom of a functional class III malocclusion.
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With this functional diagnosis, the “true forced bite”,with its
favourable prognosis, and the “pseudo forced bite”, with its
unfavourable prognosis ,must be differentiated as far as
cephalometrics is concerned.
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The term “pseudo-forced bite” includes those true skeletal
class III malocclusions where, due to partial dentoalveolar
compensation of the skeletal dysplasia in the anterior region,the
mandible occludes at the end of the closing path by means of an
anterior sliding action.If one reconstructs the tipping of the anterior
teeth in a pseudo-forced bite,these cases have a pronounced
negative overjet
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The dentoalveolar compensation of the skeletal dysplasia,which
already exists when treatment is started ,greatly restricts the range
of orthodontic treatment possibilities and unlike a true forced bite,
is indicative of a very unfavourable prognosis

Evaluation of the relationship between rest position and habitual
occlusion in a vertical plane
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The vertical dimension of free way space is
assessed.This analysis is of particular importance
to cases with a deep over bite
The true deep overbites with a large freeway
space,is caused by infraocclusion of molars.the
prognosis for successful therapy with functional
methods is favourable.As the interocclusal
cleerance is large, sufficient freeway space will
remain after extrusion of molars
The pseudo – deep overbite has a small freeway
space.The molars have erupted fully.The deep
overbite is caused by over eruption of the
incisors.The prognosis for elevating the bite
using functional appliances is unfavourable if the
freeway space is small, extrusion of molars
adversely affects the rest position and may create
TMJ problems or cause a relapse of the deep
overbite

Evaluation of the relationship between rest position and habitual
occlusion in the transverse plane
The position of midline of the mandible is observed
while the jaw is moved from the postural rest to
habitual occlusion.This analysis is particularly
relevant for the differential diagnosis of cases with
unilateral cross bite.
Depending on the functional analysis two types of
skeletal mandibular deviation can be differentiated:
laterognathy and laterocclusion
Laterognathy: The centre of the mandible is not
aligned with the facial midline in rest and
occlusion.These dysplasia constitute true
neuromuscular or anatomical assymetry. A lateral
cross bite with laterognathy is termed true cross
bite.The prognosis is unfavourable for causal
therapy
Laterocclusion:The skeletal midline shift of the
mandible can be observed only in occlusal
position;in postural rest both midlines are well
aligned.The deviation is due to tooth
guidance(functional non-true malocclusion)

Examination of the temperomandibular joint
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Through the early elimination of functional disturbances,some
incipient TMJ problems can be prevented or eliminated,this is an
indication for early orthodontic treatment.
During activator therapy the condyle is diclocated to achieve a
remodelling of the TMJ structures and a change in muscle
function.If temperomandibular structures are abnormal at the
start and hypersensitivity is a problem,the possibility of
exacerbating the symptoms exists


Clinical examination
Main objective – assess the severity of the clicking, pain and dysfunction,which are
characteristics of pathologic TMJ symptoms.
 When auscultation is carried out with the stethescope,clicking and crepitus in the
joint may be diagnosed during A-P and eccentric movements of the mandible.
Joint clicking is differentiated as follows: initial,intermediate,terminal and
reciprocal clicking
Initial clicking : retruded condyle in relation to the disc
Intermediate clicking : unevenness of the condylar surfaces and of the articular disc,
which slide over one another during the movements
Terminal clicking : condyle being moved too far anteriorly, in relation to the disc,on
maximum jaw opening
Reciprocal clicking : incoordination between displacement of the condyle and the
disc,during opening and closing


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Palpation of the TMJ during opening maneuvers - possible pain on pressure
of the condylar area
Besides the right and left condyles can thus be checked of synchrony of action.
Palpation of the musculature involved in the mandibular movements is a
considerable part of examination. In cases with functional disturbances during
childhood only LATERAL PTERYGOID causes pain due to pressure.
MASSETER muscle pain is also encountered in children with TMJ
problems.therefore, these muscle attachments should be examined on every
orthodontic patient .
Initial symptom of TMJ disturbance – palpatory tenderness of muscles
Temporalis and masseter muscles are palpated during unconsious swallowing
b’cos this could be different from swallow on command (AO 1987)

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Opening and closing movements of the mandible
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Size and direction of opening and closing are recorded during the clinical
examination
Deviations in speed can only be registered with electronic
device(eg.kinesiograph)
First signs of initial TMJ problems include deviations of the mandibular
opening and closing path in the sagittal and frontal planes.In patients with
malocclusion and malaligned teeth,disturbances in mandibular movements are
the result of an asynchronic pattern of muscle contractions.the characteristic
movement deviations include incongruency of the opening and closing curves
and uncoordinated zigzag movements.the “C” and “S” types of deviation are
typical signs of funcrional disturbances.
Occlusal analysis – in patients with symptoms of TMJ disease


TMJ – Radiographic examination

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PA projections according to Ciementschitsch, Radiographs
according to schuller or Parma,Tomograms – suitable for
examination of the TMJ
Following findings registered :
Position of condyle in relation to fossa
Width of the joint space
Changes in shape and structure of the condylar head /
mandibular fossa


Examination of orofacial dysfunction
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Swallowing
Tongue
Speech
Lips
Respiration


Swallowing
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Normal mature swallowing – without contracting the muscles of
facial expression.Teeth are momentarily in contact and the
tongue remains inside the mouth
Abnormal swallowing – caused by tongue thrust
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Protrusion of the tip of the tongue
No tooth contact of the molars
Contraction of the peri-oral muscles during the deglutition cycle

First few years – infants swallow viscerally, with tongue between
the teeth;As the deciduous dentition is completed , visceral
swallowing is replaced is replaced by somatic swallowing
If visceral swallowing persist after 4 yrs of age – Orofacial
dysfunction


Examination of the tongue
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Tongue function:

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The object of tongue function assessment is to make differential diagnosis possible and
determine tongue’s role in malocclusion
Functional appliance therapy is indicated if the role of the tongue malfunction is a
primary etiological factor
A correction of basal dysplasia of skeletal parts – establishment of normal tongue
function

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Tongue posture:

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Root is flat in mouth breathing and deep overbite caused by a small tongue
In class II div I and deep over bite,dorsum of the tongue – arched and high;tip of the
tongue – retracted

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Cephalometric evaluation of tongue posture
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Lateral cephalogram taken in postural rest and habitual occlusion
Changes in tongue position relate to different types of malocclusionclass II – tip of the tongue is more retruded in rest position
class III – tongue lies forward in rest position


Tongue thrust
Important effect on etiopathogenesis of malocclusions
1.Anterior tongue thrust – dysfunction during development of anterior open bite
2.Lateral tongue thrust – dysfunction during development of lateral open bite
3.Complex tongue thrust – occlusion supported only in the molar region
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The dentoalveolar anterior and posterior open bite problems - attributable to
abnormal tongue posture and function – responds successfully to functional
appliance intervention in mixed dentition
This is also true in cases of deep overbite,in which lateral tongue spread during
posture and function has resulted in infraocclusion of posterior teeth
A second type of over bite – caused by supraocclusion of the incisors – small
free way space,this type of problem is called functional pseudo overbite,in
these cases functional appliance is not indicated
In skeletal open bite problems,there is a genetically determined vertical growth
pattern,often associated with marked antegonial notch – does not offer a
favourable prognosis for orthodontic therapy

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The consequence of tongue posture and
function abnormalities in the
dentoalveolar region also depends on
skeletal pattern
- In horizontal growth pattern , forward
tongue thrust – bimaxillary protrusion
- In vertical growth pattern, the tongue
thrust can open the bite,lower incisors
may be tipped lingually


Palatographic examination of the tongue
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Enables observation of tongue function during swallowing and
speaking ,evaluation of the influence of various functional orthodontic
appliances on the tongue
Direct method – by Oakley,gum arabic and flour mixed and painted on
the tongue,after going through the selected functional exercises,the
contacts on the palate and teeth were transferred onto the casts
Indirect method – by Kingsley,blsck rubber placed on the palate and
tongue covered with mixture of chalk and alcohol
Current direct method – superior surface of tongue covered with
precise impression material;after functional exercises a polaroid print is
made of the palatal region with a surface mirror,the evaluation of the
palatogram is by direct measurements on the picture
Tongue with its inherent flexibility can compensate for atypical
morphological relationship,this compensatory potential as assessed by
palatographic record is an important diagnostic clue to establish a
treatment plan and a probable prognosis for functional appliance
therapy

Configuration of the craniofacial skeleton and
dysfunctions
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Horizontal growth pattern
with tongue thrust –
bimaxillary dental protrusion

Vertical growth pattern with tongue
thrust – lower incisors in lingual
inclination
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Methods of examination
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Electronic recordings
Electromyographic examination
Recording pressure exerted by tongue intraorally
Roentgenocephalometric analysis – assess position and size of
the tongue
Cine radiographic examination
Palatographic examination – records the contact surfaces of the
tongue with palate and teeth
Neurophysiologic examination


Lip dysfunctions
Assessed in relation to configuration and functioning of the lips
Configuration of the lips
• Competent lips : lips in slight contact when musculature is relaxed
• Incompetent lips : Anatomically short lips , do not touch when
musculature is relaxed.lip seal is achieved by active contraction of
the Orbicularis oris and the Mentalis muscles
• Potentially incompetent lips :The protruding upper incisors prevent
the lip closure.otherwise the lips are developed normally
• Everted lips : these are hypertrophied lips with redundant tissue but
weak muscular tonocity
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Various methods are available for evaluating the lip profile
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Schwarz analysis
H line – corresponding to frankfort horizontal
Pn line – perpendicular to the H line at soft tissue nasion
Po line – perpendicular from orbitale to the H line
Between the two construted perpendicular lines is the Gnathic profile field
( GPF)


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Ricketts lip analysis

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Reference line similar to the Schwarz T
line,but is drawn from the tip of the nose to
soft tissue pogonion
Normally,upper lip is 2-3mm and lower lip is
1-2mm behind this line

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Steiner lip analysis

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Upper reference point – center of the Sshaped curve between the tip of the nose and
subnasale,lower terminus – soft tissue
pogonion
If lip lie behind this line – they are too flat ; if
they lie in front – they are too prominent

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Holdaway lip analysis

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Quantitative assessment of lip configuration
H angle – angle between the tangent to the
upper lip from soft tissue pogonion and the NB line
Ideal profile
A-N-B angle - 2 degrees
H angle – 7-8 degrees
Lower lip touching the soft tissue line that
connects pogonion and the upper lip extended
to S-N
Relative proportions of nose and upper lip
balanced
Tip of the nose 9mm anterior to the soft tissue

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Lip habits
Lip-sucking
• Lip-thrust
• Lip insufficiency
Any lip activity during swallowing – apart from closing the lips – is
unphysiologic and a symptom of an orofacial dysfunction.visual
evidence of mentalis muscle activity is also abnormal
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Cheek dysfunctions
In cheek – sucking or cheek – biting the soft tissues are interposed
between the occlusal surfaces of the teeth – formation of lateral open
bite.
• Increased lateral pressure by cheek musculature on the mandible
impedes the transverse development of the jaw
• Common in cases with buccal nonocclusion
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Hyperactivity of Mentalis muscle
•Characteristic feature – deep mentolabial sulcus
•Impedes forward development of the anterior alveolar process
in the mandible

Mouth-Breathing
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Chronically disturbed nasal respiration – restrict development of
the dentition and hinders the orthodontic treatment
Clinical findings:
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High palate
Persisting “tooth germ position” of the upper incisors
Narrowness of the upper arch
Cross bite
Hyperplasia of the gingiva
Extra oral appearance – “adenoid facies”

Pattern of facial morphology
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The configuration of facial skeleton and oral respiration are
correlated
Proliferation of the adenoids , incidence of hypertrophied
tonsils – pronounced in patients with oronasal respiration

NO ADENOIDS

SMALL ADENOIDS

LARGE ADENOIDS

Examination of breathing mode
•The cotton pledget test
•The mirror test
•Observation of the nostrils
The scope of functional therapy in patients with respiratory problems
1.In habitual mouth breathing with small respiratory resistance, a
functional therapy is indicated.exercises can be prescribed,holding a
sheet of cardboard between the lips is a good means of enhancing the
lip seal
2.When there are structural problems,with excessive adenoid tissue ,
allergies,orthodontics can be carried out after successful ENT
treatment
3.If the structural conditions cannot be altered,functional appliance
therapy cannot be instituted,in such cases , only active fixed appliance
mechanotharapy is likely to produce the change desired

The significance of functional analysis in treatment
planning with removable appliances :
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Mandibular over closure and deep overbite with large free way
space – prognosis for treatment with functional appliance is
good
A true skeletal class III malocclusion does not offer a favourable
prognosis for functional appliance
Functional appliance therapy is particularly indicated in pseudo
class III malocclusions with normal tongue posture
Functional appliance therapy is likely to be successful in cases
with primary dysfunction in open bite and an average growth
pattern


CEPHALOMETRIC DIAGNOSIS
FOR FUNCTIONAL
APPLIANCE THERAPY


The following information can be ascertained
from the cephalometric analysis
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Configuration of the facial skeleton
Relationship of the jaw bases
Relationship of the axial inclination of incisors
Assessment of the soft tissue morphology
Growth pattern and direction
Localisation of the malocclusion
Treatment possibilities and limitations

Cephalometric reference points
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Reference points- located in the skeletal,dentoalveolar
and soft tissue regions
Include anatomic , radiographic and constructed points
Constructed point not accurate – methodological error
of individual point localisation accumulates


Cephalometric reference lines


Aims of interpretation of cephalometric
measurements:
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Analysis of skeletal structure and facial type
Assessment of vertical and sagittal relationship between
maxillary and mandibular bases
Differentiation of skeletal and dentoalveolar
malocclusions
Analysis of dental relationships
Analysis of soft tissue regarding etiology and prognosis


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The cephalometric critria can be divided into three groups

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1.Analysis of facial skeleton
2.Analysis of jaw bases
3.Analysis of the dentoalveolar relationship

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1.Analysis of facial skeleton
-Three angular measurements –
saddle angle ,gonial angle and articular angle
-four linear measurements – anterior and posterior
facial height,anterior and posterior cranial base length


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The saddle angle ( N-S-Ar)

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The angle that is formed by joining the points N , S and Ar is an
assessment of the relationship between anterior and posterolateral
cranial bases
Large saddle angle – posterior condylar position ,and mandible that is
posteriorly positioned with respect to the cranial base and the maxilla
A non compensated posterior positioning of the mandible , caused by
a large saddle angle , is very difficult to influence with functional
appliance theraphy
The articular angle (S–Ar-Go)
Constructed angle that lies between the upper and lower parts of the
posterior contours of the facial skeleton.the size of this angle depends
upon the position of the mandible
It is large when mandible is retrognathic and small when mandible is
prognathic
The angle can be influenced during orthopedic theraphy,it increases
with posterior relocation of the mandible , with opening of the bite,and
decreases with anterior positioning of the mandible,with closing the
bite

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The Gonial angle (Ar-Go-Me)
The angle formed by tangents to the body of the mandible and
posterior body of the ramus – expresses the form of the
mandible and information on its growth direction
If this angle is acute or small , the direction of growth is
horizontal.This is a favourable condition for anterior positioning
of the mandible with an activator
In cases with a large angle,activator treatment is contraindicated ,
or appliance must be constructed taking into account the
growth pattern
Facial height
The posterior facial height (S-Go) and the anterior facial height
(N-Me) are measured on the lateral cephalogram with the teeth
in habitual occlusion
To estimate the direction of growth that is so important in
activator treatment, we can compare anterior and posterior facial
height and set up a ratio, according to the recommendations of
Jarabak,
posterior facial height * 100 / anterior facial height
A ratio of less than 62 % expresses a vertical growth pattern,ratio
of more than 65 % - horizontal vector
The growth forecast for early mixed dentition treatment with an
activator should be carried out by comparing angular and linear
measurements and morphological characteristics of the mandible

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Anterior cranial base length (Se – N )

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This measurement is made using the centre of the superior entrance to the sella turcica as a
reference point , instead of sella turcica fossa outline that is usually used for cranial base
establishment
The correlation of this criterion to the length of the jaw bases enables an assessment of the
proportional averages of these bases
Average length of the anterior cranial base – 68.8mm for horizontal growth patterns ,
63.8mm – vertical growth vector

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Posterior cranial base length (S – Ar)

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Short posterior cranial base – vertical growth pattern or a skeletal open bite – poor
prognosis for functional appliance therapy


2.Analysis of the jaw bases
The angles between the vertical reference lines represent the sagittal relationship
(the SNA angle and the SNB angle).The angles between the horizontal lines
assist in evaluating the vertical ralationship of parts (base plane angle and
inclination angle).the linear measurements give an indication of the length of
the maxillary and mandibular bases as well as the length of the ascending ramus
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SNA angle

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Expresses the sagittal relationship of the anterior limit of the maxillary apical
base ( point A ) as related to the anterior cranial base
This angle is large in a prognathic maxilla and is small in a retruded maxilla
When a prognathic maxilla causes class II,division I malocclusions and there is
a larger than normal SNA angle, the use of activator is contraindicated

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SNB angle
Expresses the sagittal relationship of the anterior apical base of
the mandibular arch and the anterior cranial base
Prognathic mandible – angle is large , retrognathic mandible –
angle is small
Functional appliance treatment is indicated if the mandible is
retrognathic with a small SNB angular reading
A posteriorly located mandible can be large or small,if it is small
the prognosis for anterior posturing in the mixed dentition is
good,since a larger growth increment can usually be expected
Together with the favourable growth direction, the greater
growth increments on the mandible in the horizontal pattern
enables successful treatment of these cases by anterior posturing
of the mandible in functional appliance therapy
Basal plane angle ( Pal – MP )
Expresses the angle between the maxillary and mandibular jaw
bases and used to determine the inclination of mandibular plane
itself
In the horizontal growth pattern this angle is small, whereas it is
large in vertical growth group


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Inclination angle

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Gives an assessment of the inclination of the
maxillary base
It is the angle formed by the Pn line and the palatal
plane
A large angle expresses upward and forward
inclination, whereas a small angle indicates a
downward and backward tipping of the anterior end
of the palatal plane or maxillary base

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Rotation of the jaw bases

Basal plane angle and inclination angle are used to evaluate the rotation of the
upper and lower jaw bases
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These rotations are of special interest in treatment with functional appliances
because they show whether such appliances are indicated and provide criteria
for appliance construction
Bjork differentiates the two processes involved in the rotational growth of the
mandible
1.remodelling of the mandible in the symphyseal and Gonial areas – intermatrix
rotation.
Apposition in the gonial area, resorption in the symphyseal area- horizontal
rotation
Apposition in the symphyseal area , resorption in the gonial area – vertical
rotation
2.vertical or horizontal rotation of the mandible in its neuromuscular envelope –
matrix rotation.
rotation observed cephalometrically is called total rotation,it consists of both
intermatrix and matrix rotation
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Functional orthodontic and orthopedic methods alter the function and guide the
growth process,rotation of the mandible may be moderately influenced
therapeutically
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Rotation of the Maxillary base
The Inclination angle records the rotation of the maxillary base to the anterior cranial base
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The angle is not measured directly,but defined as the angle between the Pn-perpendicular
and the palatal plane
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Anteinclination-forward maxillary rotation
retroinclination-backward maxillary rotation
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Maxillary inclination influences the clinical appearance of the anterior tooth position,it can
be changed by dentofacial orthopedic treatment.
NORMALINCLINATION = 85
ANTELNCLINATION > 85
RETROINCLINATION < 85
•

Combinations of maxillary and mandibular rotation

•Convergent rotation of the jaw bases
•Divergent rotation of the jaw bases
•Upward rotation of both jaw bases
•Downward rotation of both jaw bases

Rotation of the jaw bases
Convergent and Divergent rotation
•Combination of the maxillary and
mandibular rotation determines the
degree of the anterior overbite
•When the jaw bases are rotated
equivalently in the same direction,the
vertical dimension during growth
remains constant
•Convergent rotation – deep bite
Rotation in the same direction
• Divergent rotation – open bite


Linear measurement of the jaw bases
•

•

•


•

•

In the determination of indication for functional
appliance therapy,both the position and the length of
the jaw bases must be assessed
The length of the maxillary and mandibular bases and
ascending ramus is measured relative to Se-N
The ideal dimension relative to Se-N is calculated using
the following ratios
N-Se : Man base - 20 : 21
Ascending ramus : Man base – 5: 7
Max base : Man base – 2 : 3

Extent of the mandibular base
Determined by measuring the distance Gonion –
Pogonion
Ideally the mandibular base should be 3mm longer
than Se-N



Extent of the maxillary base

•

Distance between the posterior nasal spine and
point A projected perpendicularly onto the
palatal plane
The evaluation of this dimension has two “ideal”
measurements : one related to N-Se and the
other to the length of the mandibular base

•



Length of the ascending ramus

•

Distance between Gonion and Condylion
Important in determination of posterior facial
height and subsequent relation to the anterior
facial height

•


Evaluation of the length of the jaw base

•

•

•
•

•

Mandibular base
If the length of the mandibular base corresponds to the distance N-Se,it indicates an age
related normal mandibular length and an average growth increment can be expected
If the base is shorter,growth increment is larger;if the base is longer,growth increment is
smaller
A retrognathic mandible may have either short or long base
If base is short the cause of retrognathism is a growth deficiency;if a favourable growth
direction is present ,the prognosis for functional appliance therapy is good
A mandibular base that is both long and retrognathic can result from two possibilities
1.The mandible is in a functionally retruded position because of over closure and occlusal
guidance.in postural rest,it is anterior to habitual occlusion.treatment is simple – elimination
of the forced guidance and up and back path of closure in either the mixed or permanent
dentition
2.The mandible is morphogenetically “built” into the facial skeleton in a posterior position.the
temporal fossa is posterior and superior.This discrepancy is not compensated despite the long
mandibular base.the prognosis for functional appliance therapy in these cases is poor




Maxillary base

•

Assessment of length of maxillary base has 2 ideal values : one related to the distance N-Se,the
other to the length of the mandibular base
A deviation from the mandibular base-related norm --- maxillary base is too long or too short
If the maxillary base corresponds to the mandibular base - related norm,the facial skeleton is
proportionally developed,particularly if the ramal length also corresponds to these values
If the N-Se length does not relate to these three proportionate measurements,the facial
skeleton is proportionate but either too large or too small

•
•

•



Ascending ramus

•

If the ramus is too short in relation to the other proportions,a large amount of growth can be
expected because the growth pattern is not vertical
In vertical growth patterns the ramus remains short

•




Morphology of the mandible

•

Orthognathic type of face – ramus and body of the
mandible are fully developed,width of the ascending
ramus is equal to the height of the body of the
mandible,including the height of the alveolar process
and incisors.the condylar and coronoid processes
almost on the same plane,and the symphysis is well
developed
In the prognathic type the corpus is well developed and
wide in the molar region.The symphysis is wider in the
sagittal plane.the ramus is wide and long ,and gonial
angle is acute or small
Retrognathic facial type the corpus is
narrow,particularly in the molar region.the symphysis is
narrow and short,coronoid process is shorter than the
condylar process,and the gonial angle is obtuse or large
The prognathic type of mandible grows
horizontally.even if an average or slightly vertical
growth direction is evident in the mixed
dentition,shifting of the mandible to a horizontal
growth direction can be expectd in the following years
In a retrognathic mandible,shifting of the growth
pattern in the opposite direction is less likely and
produces much less expressivity

•

•

•

•


•Analysis of dentoalveolar relationship



Axial inclination of incisors
Position of the incisors



Axial inclination of the incisors



Upper incisors

•

The long axis of the maxillary incisors is extended
to intersect the S-N line,and the posterior angle is
measured
Larger angles indicate a procumbency or labial
crown tipping
Incisor protrusion requires lingual tipping,a
therapeutic objective that can be achieved with
removable appliances if adequate space is available

•

•




Lower incisors

•

To assess axial inclination of the teeth – measurement of the posterior angle between
the long axis of the lower incisors and the mandibular plane
Ideal angle – 90 degrees
Smaller angle – lingual tipping of the incisors – advantages for functional appliance
treatment
Classical activators are most effective in the sagittal plane and tend to tip the lower
incisors labially
If lower incisors are already labially tipped , functional appliance treatment is more
difficult;anterior repositioning of the mandible and uprighting of the lower incisors
become necessary,if possible moved in the opposite direction
This requires special appliance design in the lower anterior segment

•
•

•

•

•




Position of the incisors

•

Linear measurements are the best assessors of the
position of the incisors with respect to the profile
Common method – to measure the distance of
the incisal edges to the N-Pog line – Facial line
Average position of the maxillary incisors is 2 to 4
mm anterior to the N-Pog line.the lower incisors
vary from 2mm posterior to 2mm anterior to this
line
The relationship of the lower incisors to the NPog line also helps determine the sagittal
discrepancy
Incisors behind this line can be moved labially
because space is available,incisors anterior to the
facial plane that must be moved lingually require
additional space,which may be obtained only by
extraction procedures
The amount and direction of growth spurt should
be considered in the mixed dentition,while ideal
position of incisors is being planned

•
•

•

•

•

Anteroposterior skeletal assessment
o

The AP position of the jaws is assessed based on measurements that use the true
horizontal (TH) as the reference line



Size of the mandible (Go-Gn) relative to the anterior cranial base (SNa)

•

A ratio of GoGn:SN=1 indicates a well balanced mandibular body relative to the
cranial base.
The importance of this measurement lies in the fact that a very retrognathic profile
may be due to a short mandibular body that affects the anteroposterior plane , which
may require surgical intervention, depending on the deformity and age of the patient

•



Maxillomandibular ratio (PNS-ANS:ArGn)

•

According to Michigan growth atlas, the length of the mandible,defined from
Articulare(Ar) to Gnathion(Gn), is almost exactly double of the maxillary
length,defined from posterior and anterior nasal spine(PNS-ANS)
A ratio of 1:2 indicates the actual lengths of the maxilla and mandible are in good
balance with each other.

•




Assessment of the position of the jaws using Linear
and Angular Measurements

Proffit and White have proposed using a perpendicular from the
nasion with the TH in assessing the maxillary and mandibular
anteroposterior relationship with linear measurements.
•
3 suggested linear measurement from points A,B,and pogonion (Pg)
to nasion perpendicular to TH relate the position of the maxilla,
mandible ,and chin respectively
•
A- point should be 1 mm in front of the Na – perpendicular,
whereas B- point and Pg should be 3mm and 1mm behind the line
respectively
•
Due to the importance of accurate assessment of the anteroposterior
position of both the maxilla and the mandible relative to each other
and the cranial base,angular measurements are also calculated
between the –
-TH and NaA – 90 degrees +/-3degrees
-TH and NaB – 87 degrees
-TH and NaP – 89 degrees +/- 3 degrees
•


Assessment of the relative anteroposterior position of the maxilla and the
mandible – the true horizontal Wits and the ANB angle
•

If A and B are projected on the TH through perpendicular lines points
A and B are defined,respectively

•

The AB distance is defined as the true horizontal Wits versus the
original Wits on the occlusal plane
The TH Wits provides a better and more clear relationship of the
anteroposterior position of the jaws relative to each other than does
the original Wits ,which can sometimes be affected by the inclination
of the occlusal plane or by the inclination of the Frankfort horizontal
The Wits appraisal does not necessarily focus attention on changes
actually occuring in the sagittal relation between the maxilla and the
mandible
Rather,because of changes in the angulation of the occlusal plane,the
true sagittal changes are likely to be disguised
A correlation between angle ANB and Wits would not be expected
because they each involve an exclusive point or plane , which is not
necessarily biologically related.the mean +/- SD for this measurement
is 4 +/-2 mm
In addition to the TH Wits linear measurement, an angular
measurement ,the ANB angle , is also used to assess the
anteroposterior position of the jaws

•

•

•
•

•

The mean+/- SD is 3 degrees +/- 2 degrees


Anteroposterior assessment of the chin – the
chin length and the BNP angle

•A line parallel to the TH is drawn tangent to the
mandible at Menton.projections of the B point and Pg
define the chin length(BP)
•The mean +/- SD for this measurement is 2 +/- 2mm
•An angular measurement , the BNP angle , assesses the
prominence of the chin relative to the body of the
mandible
•The mean +/-SD for the BNP angle is -2 degrees +/- 2
degrees


Vertical skeletal assessment


The following 10 cephalometric measurements may aid the clinician
in appreciating a patient’s facial vertical growth:
Width of the symphysis parallel to the True Horizontal from
Pogonion (P TH)
•
•
•



The greater this measurement is ,the more of forward rotation is to be expected
A narrow symphysis corresponds to a backward growth rotation
The mean +/- SD is 16.5mm +/- 3mm

Angle of the symphysis ( BP – MeTH )
•
•
•
•

This is defined by the line connecting B-point and Pogonion (P) as it crosses a line parallel to the
true horizontal (TH) at Menton (Me)
The mean +/- SD is 75 degrees +/- 5 degrees
If the symphysis is inclined backwards , that is , if the angle of the symphysis is acute , this is an
indication of forward rotational pattern
If it is inclined forward (angle is obtuse),there will be backward rotation




Mandibular plane angle (GoMe–TH)

One of the most widely used cephalometric measurements , this angle may sometimes mask
the true growth tendencies of the mandible due to extensive remodelling changes occuring at
the angle of the mandible and the symphysis
• High values indicate a backward growth rotator,and low ones indicate a horizontal growth
pattern
• The mean +/- SD is 27 degrees +/-5 degrees.the angle will decrease approximately 2 degrees
+/- 2 degrees from childhood to adulthood.
Sum of posterior angles
• The mean value of the sum of the cranial flexure angle SNa – SAr (saddle angle),Articular angl
(SAr – ArGo) and gonial angle (ArGo-GoMe) is 396 degrees +/- 4 degrees
• High values indicate a vertical growth pattern (clockwise,opening or backward
rotation),whereas low ones show a horizontal growth pattern (counter clockwise,closing or
forward growth rotation)
• The mean +/-SD of the individual angles is:
SNa – SAr – 123 +/-5 degrees
SAr - ArGo – 143 degrees +/- 6 degrees
ArGo – GoMe – 130 degrees +/- 7 degrees
Gonial angle (ArGoMe)
• Described by Bjork and Jarabak and Fizell , with a mean of
130 degrees +/-7 degrees , an increased gonial angle
indicates a backward growth rotator, and a decreased
one indicates a forward growth rotator
•






•

Gonial angle ratio
•
•
•

•

Posterior cranial base to Ramus height ratio (SAr :ArGo)
•
•

•

•

A line from Gonion to Nasion divides the gonial angle into upper (ArGoNa) and lower
(NaGoMe).
If the ratio of the upper to the lower angle is more than 75% (high upper angle ) –
indicates increased horizontal growth rotation
The opposite – high lower angle indicates a vertical growth pattern
The length of the posterior cranial base needs to be measured and compared to the mean
for the individual sex and the age group
Providing that the length of Ar is within normal limits , a ratio value of more than 75 %
would indicate a short ramus height,thus contributing to a clockwise rotation skeletal
pattern
A short posterior cranial base is also indicative of a backward growth rotator

Posterior / Anterior face height ratio ( SGo : NaMe )
•

Values higher than 65% - forward growth pattern ,
ratio of less than 65% - backward growth rotator


JOURNAL REVIEW


Eight methods of analysing a cephalogram to establish
the A-P skeletal discrepancy – BJO 1981 vol 8
•
•
•
•
•
•
•
•

Downs analysis
Steiner analysis
Eastman analysis
Bjork analysis
Ricketts analysis
Tweed analysis
Wits analysis
Wylie analysis


Eight methods of analysing a cephalogram to
establish A-P skeletal discrepancy
The 8 analyses use between them three occlusal planes
1.A line joining 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 and Steiner
2.The functional occlusal plane - A line joining the midpoint of the overlap of the
mesio-buccal cusps of the first molars and the buccal cusp of the pre molars
or deciduous molars
3. A line joining the mid section of the molar cusps with the tip of the upper
incisor, used by Bjork
Three mandibular planes are used
1.The tangent to the lower most border of the mandible, used by Tweed and
Ricketts
2.The line joining the Gonion and Menton used by Downs and Eastman analysis
3.The line joining the Gonion and Gnathion,used by Steiner

A new approach of assessing Sagittal
discrepancies : The beta angle
•

•

•

•

A new angle – beta angle – developed as a
diagnostic aid to evaluate sagittal jaw
relationship
3 skeletal landmarks – point A , point B ,
and apparent axis of the condyle
3 lines –
line connecting centre of condyle C with
B
line connecting A and B points
line from point A perpendicular to the CB line
Beta angle – angle between the last
perpendicular to the C-B line

Beta angle
between 27degrees-35 degrees - class I skeletal pattern
less than 27 degrees – class II
greater than 34 degrees – class III
• Beta angle enriches the current cephalometric tools available
to the clinician and enables better diagnosis and treatment
planning for the patients
•


Summary :
-salient points of cephalometric analysis for the use of functional
appliance therapy
• Allows anomalies to be located and differentiations made between
skeletal and dentoalveolar malocclusions
• Helps determine primary and secondary dysplastic structures and
possible autonomous compensatory responses before treatment
begins
• Allows the determination of whether the jaw bases are anteriorly or
posteriorly positioned , short or long
• In the vertical plane the possible rotations of the maxillary and
mandibular bases can be observed and the growth pattern
delineated
• Assessment of the influences of neuromuscular dysfunction on the
dentition – vital for diagnosis and treatment planning with
functional appliance

References :
•
•
•
•
•
•
•
•

Petrovic – Dentofacial orthopedics with functional
appliance
Graber and Neumann – Removable orthodontic
appliances
Rakosi and Jonas – Orthodontic diagnosis
Alexander Jacobson – Radiographic cephalometry
Thomas Rakosi – Cephalometric Radiography
Chong Yol Baik – AJO July 2004
Moira Brown – BJO Vol 8 , 1981
D.Millett and J.F.Gravely – BJO 1991


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