CEPHALOMETRICS Slide 2 Diagnostic records for orthodontic
purposes may be divided into three major categories : 1. dental
casts and occlusal records 2. photographic records 3. radiographic
records Slide 3 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 Slide 4 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 patients 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. Slide 5 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 patients head, the film and the anode of
the X-ray tube. Cephalometric head holder fix the patients head at
two points by the ear rods fitting into the external auditory
canals. Slide 6 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 Slide 7 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. Slide
8 CEPHALOMETRICS X-RAY TECHNIQUE : Slide 9 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, Downs, had five skeletal and five dental criteria, each
meant to evaluate a particular relationship. Slide 10 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. Slide 11 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. Slide 12 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. Slide 13 CEPHALOMETRIC
ANALYSIS METHODS OF DATA EVALUATION : Slide 14 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. Slide
15 Slide 16 CEPHALOMETRIC ANALYSIS METHODS OF DATA EVALUATION : In
diagnosis, the patients 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. Slide 17 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 patients 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 patients response to treatment. Slide 18
Cephalometric analysis First step in cephalometric analysis is to
mark certain points. The following landmarks are used : Sella (S)
the centre of sella turcica Slide 19 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 Slide 20 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. Slide 21 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. Slide 22 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. Slide 23 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. Slide 24 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.
Slide 25 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. Slide 26 RELATION OF MAXILLA AND MANDIBLE
TO CRANIUM : Slide 27 ASSESSING THE JAW SKELETAL PATTERN : Slide 28
Slide 29 VERTICAL RELATIONSHIPS : Slide 30 INCLINATION OF THE
INCISORS : Slide 31 POSITION OF THE INCISORS : Slide 32 MANDIBULAR
GROWTH ROTATION Slide 33 ESTHETIC LINE Slide 34 PROFILE ANALYSIS
Slide 35 Slide 36
