Cephalometrics.19.Mar.2013

Report
CEPHALOMETRICS
• Diagnostic records for orthodontic
purposes may be divided into three major
categories :
1. dental casts and occlusal records
2. photographic records
3. radiographic records
Basic radiographic records used in
orthodontics are lateral cephalometric
radiographs.
They have two purposes :
1. they reveal details of skeletal and
dental relationships that cannot be
observed in other ways and
2. they allow a precise evaluation of
treatment response
• Analysis of lateral skull radiographs allows
a more detailed evaluation of facial structures
than is possible from a visual assesment of
facial appearance.
• However, in many instances an adequate
orthodontic diagnosis can be made without
a cephalometric radiograph, it is practially
impossible to assess accurately a patient´s
response to treatment without being able to
compare cephalometric films before and after
treatment.
For this reason, even in patient whose dental
and skeletal relationships seem perfectly
straightforward, a lateral cephalomeric film is
needed.
CEPHALOMETRICS – X-RAY TECHNIQUE
• The lateral cephalometric
radiograph is taken with the
head held in a specially
designed holder so that
there is a fixed constant
relationship between the
patient´s head, the film and
the anode of the X-ray tube.
• Cephalometric head holder
fix the patient´s head at two
points by the ear rods
fitting into the external
auditory canals.
:
CEPHALOMETRICS – X-RAY TECHNIQUE
:
• The head is in natural relaxed position. Patient gets it by
looking at a distant horizont. At this position the midsagittal
plane of the head is parallel to film
• X-ray beam should run through the external auditory canals and
should be perpendicular to midsagittal plane of the head.
• The teeth should be held lightly together in centric occlusion.
The lips should be relaxed
CEPHALOMETRICS – X-RAY TECHNIQUE
:
• We have to keep these standard conditions to take standard and
comparable cephalometric radiographs.
• The midsagittal plane of the head is at a fixed distance from the film - 10 cm.
• The distance of the X-ray tube from the head should be more than 1.5 m.
This makes the X-rays nearly pararel, not divergent as usual.
CEPHALOMETRICS – X-RAY TECHNIQUE :
CEPHALOMETRIC ANALYSIS – HISTORY
AND AIMS :
Cephalometric analysis was developed initially by
selecting measurements that were most
useful in differentiating patients with the
various Angle classes.
The objective was to produce a reasonably finite
number of measurements that would serve as
guides in evaluating particular relationships.
The original analysis, Down´s, had five skeletal
and five dental criteria, each meant to evaluate
a particular relationship.
CEPHALOMETRIC ANALYSIS – HISTORY
AND AIMS :
At present there are many named cephalometric
analyses, each based on choosing some specific
measurements from the multitude that might be used
to evaluate a single relationship.
There is not and will not be any single analysis
that is ideal for every patient, simply because
certain measurements will be useful in providing
information about certain patient but not useful for
others.
CEPHALOMETRIC ANALYSIS – HISTORY
AND AIMS :
The goal of cephalometric analysis must be
evaluation of the underlying
relationships, not recording of any
particular set of measurements.
The measurements are always a means to
this end.
CEPHALOMETRIC ANALYSIS –
METHODS OF DATA EVALUATION :
Cephalometric analysis may be carried out on the
radiograph itself or on the tracing of the
radiograph.
The tracings have two advantages :
1. they reduce the amount of information on the
film to a manageable level ( so they emphasise
the relationship of selected points )
2. they can be better superimposed to show
changes caused by growth or treatment.
CEPHALOMETRIC ANALYSIS –
METHODS OF DATA EVALUATION :
CEPHALOMETRIC ANALYSIS –
METHODS OF DATA EVALUATION :
The landmarks used in tracing can be represented
as coordinate points on an (x,y) graph, and the
digital coordinates can readily be placed into
computer memory.
An adequate digital model is required, which
means that at least 50 and preferably 100 or
more points should be digitized.
Exellent software programs are available to
calculate angles and distances, and to
superimpose digitized tracing.
CEPHALOMETRIC ANALYSIS –
METHODS OF DATA EVALUATION :
In diagnosis, the patient´s facial and dental
proportions are compared to a reference group,
so that differences between the patient and
normal values can be highlighted.
Normal dental and facial proportions can be
represented in two ways :
1. as tabulated measurements
or
2. as a normal tracing produced by averaging the
coordinates for the reference sample.
CEPHALOMETRIC ANALYSIS –
METHODS OF DATA EVALUATION :
Therefore comparison of a patient to reference
sample can be done in two ways :
1. by comparing selected measurements for
the patient to the same measurements on the
reference sample, which is the typical
cephalometric analysis aproach or
2. by superimposing the normal tracing on the
patient´s tracing and visually comparing the
two. This method is called template analysis.
It is recomended as an initial step in determining
how the patient differs from the norm or in
assessing the patient´s response to treatment .
Cephalometric analysis
First step in cephalometric analysis is to mark certain points.
The following landmarks are used :
• Sella (S) – the centre of sella turcica
Cephalometric analysis
•
•
•
•
Nasion (N) – the most anterior point on frontonasal suture
Menton (Me) – the lowermost point on the mandibular symphysis
Gonion (Go) – it is located on intersection of the tangent to posterior outline of the
mandibular ramus and tangent to mandibular body through menton ( mandibular
plane )
Pogonion (Pg) – the most anterior point of the bony chin
Cephalometric analysis
• Point A (A) – also known as subspinale, this is the deepest point on the
maxillary profile between the anterior nasal spine and the alveolar crest.
• Point B (B) – also known as supramentale, this is the deepest point on the
concavity of the mandibular profile between the point of the chin and the
alveolar crest.
Cephalometric analysis
• Anterior nasal spine (ANS) – the point of the bony nasal spine.
• Posterior nasal spine (PNS) – the tip of the posterior nasal spine can
usually be seen unless unerupted molars obscure it. The outline of the
palate gives a good indication of its vertical level. A line through the most
inferior point on the pterygo-maxillary fissure, perpendicular to the maxillary
plane, indicates the antero-posterior location of PNS.
Cephalometric analysis
• Orbitale (Or) – the most inferior point on the margin of the orbit.
• Porion (Po) – the highest point on the bony external acustic meatus.
• Prostion (Pr) – the lowest point on the alveolar crest labial to the most
prominent upper central incisor.
Cephalometric analysis
•
•
•
•
Infradentale (Id) – the highest point on the alveolar crest labial to the most
prominent lower incisor.
Incision superius (IS) – the tip of the crown of the most prominent maxillary incisor.
Incision inferius (II) – the tip of the crown of the most prominent mandibular incisor.
Gnation (Gn) – the most anterior, inferior point on the bony symphysis of the
mandible.
Cephalometric analysis
• Commonly used reference lines are following :
• Facial line (NPog) – nasion-pogonion. It indicates the general
orientation of the facial profile.
• Frankfort plane (PoOr) – porion-orbitale. This plane is
described as being horizontal when the head is in free postural
position. In fact, there is considerable individual variation.
Cephalometric analysis
• Mandibular plane (Mn) – the line from menton, tangent to the
lower border of the mandible at the angle.
• Maxillary plane (Mx) – this is line through the anterior and
posterior nasal spine. It indicates the orientation of the palate.
• Functional occlusal plane – the line following the occlusion of
the molar and premolar teeth.
RELATION OF MAXILLA AND MANDIBLE
TO CRANIUM :
ASSESSING THE JAW SKELETAL
PATTERN :
ASSESSING THE JAW SKELETAL
PATTERN :
VERTICAL RELATIONSHIPS :
INCLINATION OF THE INCISORS :
POSITION OF THE INCISORS :
MANDIBULAR GROWTH ROTATION
ESTHETIC LINE
PROFILE ANALYSIS
PROFILE ANALYSIS

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