2 extra-oral radiography[1]

03/28/1603/28/16 Ossama El-ShallOssama El-Shall
Extra-oral Radiography
Dr. Ossama EL-ShallDr. Ossama EL-Shall
Professor and Chairman, Oral Medicine,Professor and Chairman, Oral Medicine,
Periodontology, Diagnosis and RadiologyPeriodontology, Diagnosis and Radiology
Dept., Faculty of Dental Medicine Al-AzharDept., Faculty of Dental Medicine Al-Azhar
University , Cairo Egypt.University , Cairo Egypt.
E.mail address: oelshall@hotmail.comE.mail address: oelshall@hotmail.com

Contents
Extra-oral films
Intensifying screenIntensifying screen
Cassettes
Extra-Oral radiographicExtra-Oral radiographic
projections,projections, (Plain radiographs).(Plain radiographs).
Specialized radiography
Examination of salivary
glands
Examination of maxillary
sinus
Examination of TMJ

Extra oral films
Extra-oral films are the films placed extra-
orally during exposure in order to exam the
mandible, the maxilla, the TMJ and all the
facial bones.
Extra-oral films usually supplied in special
light tight boxes in quantities of 50 or 100
films and loaded in a special light protected
holder (cassette) inside the dark room.

Extra-oral films used in dental purposes
supplied in two main sizes:
1- 5X7 and 8X10 inches for
examination of skull and jaws
2- 5X12 or 6X12 inches for panoramic
radiography.

General indications of use of extra-oral
films
1- Patients who cannot open their mouths sufficiently for
insertion of intra-oral films due to any causes such as trauma
of truisms.
2- Unco-operative patient such as mentally retarded and children.
3- Examination of large pathologic involvement, such as large
cyst.
4- Obtaining a large generalized view of jaws, sinuses and bones.
5- Examination of fracture lines and extension of fracture in skull
bone.
6- Localization of foreign bodies.
7- Examination and diagnosis of TMJ disorder.
8- Obtaining of generalized view of unerupted, impacted or
supernumerary teeth.

Types of extra-oral films.Types of extra-oral films.
Screen filmsScreen films
Non screen filmsNon screen films

Screen filmScreen film
Is used in combination with intensifyingIs used in combination with intensifying
screens.screens.
These films are different from other dentalThese films are different from other dental
films in that they are designed to befilms in that they are designed to be
particularly sensitive toparticularly sensitive to visible lightvisible light ratherrather
than to X-radiation.than to X-radiation.
This is because they are used by being placedThis is because they are used by being placed
between two intensifying screens.between two intensifying screens.
The intensifying screens absorb X rays andThe intensifying screens absorb X rays and
emit visible light that exposes the screen film.emit visible light that exposes the screen film.

Non screen filmsNon screen films
Or direct exposure films;Or direct exposure films;
they are more sensitive to x rays than to light.they are more sensitive to x rays than to light.
It requires a longer exposure time as itIt requires a longer exposure time as it
depends on thedepends on the x rays onlyx rays only to affect the filmto affect the film
not on any emitted light.not on any emitted light.
It may be used for thin bones only such asIt may be used for thin bones only such as
long bone and mandible.long bone and mandible.
However its use in dental radiography is notHowever its use in dental radiography is not
recommended.recommended.

Extra-oral film equipmentsExtra-oral film equipments
CassetteCassette

It is a device used to intensifies theIt is a device used to intensifies the
photographic effect of X-rays and thusphotographic effect of X-rays and thus
shortens the exposure time that otherwiseshortens the exposure time that otherwise
would be long to suit the thickness andwould be long to suit the thickness and
density of tissues in case of extra-oraldensity of tissues in case of extra-oral
radiography.radiography.

The use of intensifying screen is based
on three main principles:
X radiation have a biological damaging
effect that should be protected through
decrease the exposure time.
Certain substances can cause
fluorescence if it absorb X radiation.
Photographic film is sensitive to both X
radiation and visible light.

When x-rays strike intensifying screen, they
immediately activate it so it emits light
which is going together with the x-rays to
expose the film.
Thus the light produced by the screen
intensifies the effect of the x-rays on the
film and helps reduction of exposure time.
The intensity of this fluorescence is directly
proportional to the intensity of the exiting
x-ray.

= phosphor crystal
film
Mechanism of action of the screen

Composition of intensifying screen:
Plastic or cardboard base.
Reflecting layer: It is a layer of titanium oxide that covers
the base of the screen and lies beneath the phosphor layer.
Its function is to reflect any light emitted from the
phosphor layer back to the film and thus increase the
effect of the screen.
The phosphor layer: It is the light sensitive crystals layer,
it formed from Calcium tungestate or Barium lead
sulphate (conventional type that emit a blue light) or
formed from a rare earth phosphors as Gadolinium or
Lanthanium (rare earth type that emit green light).
Protective layer: made up of a plastic layer with smooth
surface.

Intensifying Screen Composition
-Base (thick white line) = plastic for support
-Reflecting layer (red line) = reflects light
back
toward film
-Phosphor layer (green line) = rare earth
(10
)
(this side toward film)

Types of intensifying screens:
I- According to the phosphor layers:
Conventional screens: the phosphor layer made of
Calcium tungestate or Barium lead sulphate and it
emit a blue light. For example: Kodak X-Omatic
screens.
Rare earth screens: the phosphor layer made of
rare earth phosphors, Gadolinium or Lanthanium
and it emit a green light. For example: Kodak
Lanex screens.

II- According to speed: (phosphor crystal
size)
Slow: has the smallest crystals and give the
best image details.
Intermediate: Have larger crystals and less
detail.
Fast: The largest crystals and least details.

= phosphor crystal
film
Light Emission from the screen

Loaded Screen film
film

Cassettes
Cassette holder is another equipment
necessary for the extra-oral films.
The extra-oral film is sandwiched between 2
intensifying screens of matching size and
type and secured in a cassette holder.

Cassette and its contents
1. Cassette front: made of plastic, aluminum
or carbon fibers to allows more rays to
pass and thus reducing patient exposure.
2. Two intensifying screens.
3. The screen film
4. Felt padding: to assure intimate and even
contact between film & screens
5. Cassette back: made of lead

Cross section of loaded cassette
Cassette front
Screen
Film
Screen
Felt padding
Cassette back

Cassette/Film

Types of cassettes according to their uses
1. Rigid cassette for skull views.
2. Rigid or flexible cassette for panoramic
films
3. Occlusal cassettes for occlusal films when
they are used extraorally.

Cassettes
Hold intensifying
screens (2) in
tight contact with
film
Rigid (metal) or
soft (vinyl)
Rigid metal cassette
Flexible vinyl cassette

Extra-Oral radiographic projections.Extra-Oral radiographic projections.
(Plain radiographs).(Plain radiographs).
Lateral skull projectionLateral skull projection
Posteroanterior projection:Posteroanterior projection:
(PA).(PA).
Mandibular Lateral obliqueMandibular Lateral oblique
projections.projections.
Water’s view:Water’s view:
(occiptomental projection).(occiptomental projection).
Reverse-Towne projection.Reverse-Towne projection.

Plain radiographs.Plain radiographs.
Frankfort plane:Frankfort plane: It extendedIt extended
from the anterior border of the externalfrom the anterior border of the external
auditory meatus to the infra-orbital rim.auditory meatus to the infra-orbital rim.
The canthomeatal line:The canthomeatal line: It isIt is
the line between the central points of thethe line between the central points of the
external auditory meatus to the outerexternal auditory meatus to the outer
canthus of the eye. It makes 10 degree withcanthus of the eye. It makes 10 degree with
the frankfort plane. (radiographic base line)the frankfort plane. (radiographic base line)

Frankfort planeFrankfort plane
Canthomeatal lineCanthomeatal line

Concerning the nomenclature of theConcerning the nomenclature of the
film projection, thefilm projection, the firstfirst word of theword of the
description isdescription is where the tube is;where the tube is; thethe
secondsecond word isword is where the film iswhere the film is i.e. PAi.e. PA
film has the tube at the back of thefilm has the tube at the back of the
head (P) and the film is placed by thehead (P) and the film is placed by the
face (anterior).face (anterior).

Lateral cephalometric, True lateral, Dead lateralLateral cephalometric, True lateral, Dead lateral
It used to survey the skull and facial bones for
evidence of trauma, disease, or developmental
abnormality.
This view reveals the nasopharyngeal soft
tissues, paranasal sinuses, and hard palate.
Orthodontists use it to assess facial growth,
and in oral surgery and prosthetics it
establishes pretreatment and post-treatment
records.

Film placement: the film is positioned vertically in a
cassette-holding device.
Head position: the head should be positioned with
the side of the face near the cassette, the
interpupillary line perpendicular to the film, and
the midsagittal plane parallel to the plane of the
film.
Projection of the central ray: It directed toward the
external auditory meatus and perpendicular to the
plane of the film and midsagittal plane. Therefore,
superimposition of both sides of the skull, facial
bones and mandible.

Lateral Cephalometric
Identify trauma, abnormalities
Assess facial growth; treatment record
film at set distance from MSP
film horizontal
extraoral x-ray
unit
MSP
floor
MSP

Patient and film position during lateral
projection

Cephalometric MachineCephalometric Machine

Position of the patient in the cephalometric machine
for lateral cephalometric film

Radiographic and photographic projectionsRadiographic and photographic projections
superimposedsuperimposed

Posteroanterior projection: (PA)Posteroanterior projection: (PA)
It is so named because the X-ray beam passes in a
posterior-to-anterior direction through the skull.
It used to examine the skull for disease, trauma or
developmental abnormalities.
It provides a good record to detect progressive
changes in the mediolateral dimensions of the skull.
It also offers a good visualization of facial
structures, including the frontal and ethmoid
sinuses, nasal fossae, and orbits.

PAPA

Film placement: the cassette is
positioned vertically in a hold in
device in front to patient.
Head position: the head is centered
in the front of the cassette with
the canthomeatal line parallel to
the floor and the tip of the nose
and forehad are in contact with
the cassette.
Projection of the central ray: the
central ray is directed
perpendicular to the plane of the
film and coincident with the
midsagittal plane of the head at
the level of the bridge of the
nose.

Patient head position in relation to the
cassette during P.A projection

Posteroanterior (PA) Skull
Identify trauma, pathology, or
developmental abnormalities
FP
floor
MSP
extraoral x-ray unit

Position of the patient for posteroanterior projection
produced by cepalometric machine

Taken with intraoral
x-ray machine. (Note
round collimation).
Not recommended,
but possible.

It is a variant of the postero-anterior view.
It particularly used for evaluation of
maxillary sinuses, in addition to frontal and
ethmoid sinuses, the orbit, nasal cavity and
the coronoid process of the mandible.
Water’s viewWater’s view
(Occiptomental projection)(Occiptomental projection)

Film placement: the cassette is positioned
vertically.
Head position: the sagittal plane of the head is
perpendicular to the plane of the film. The
chin is raised to elevate the canthomeatal line
37 degrees above horizontal plane. A bite block
is used to secure max. jaw opening.
Projection of the central ray: the central ray
should be perpendicular to the film, through
the midsagittal plane, at the level of the
maxillary sinus.

Water’s view
(Occiptomental projection)

Waters
Evaluate the maxillary sinus
MSP
floor
extraoral x-ray
unit
(Sinus view)
tip of nose 1” from
cassette
CR
FP

Position of the patient for Water’s view using
cephalometric machine

Mandibular posterio-anterior viewMandibular posterio-anterior view
(Reverse-Towne projection)(Reverse-Towne projection)
It used to examine a patient with aIt used to examine a patient with a
suspected fracture of the condylarsuspected fracture of the condylar
neck,neck, especially in cases of mediallyespecially in cases of medially
displaced condyle.displaced condyle.

Film placement: the cassette is positioned in a
holding device in front to the patient.
Head position: the head is centered in front of
the cassette with the canthomeatal line
oriented downward 25 degree. The patient
instructed to open his mouth as wide as
possible to help visualize the condyles.
Projection of the central ray: the central ray is
directed to the film in the sagittal plane
through the occipital bone.

CM lineCM line RaysRays

Mandibular posterioanterior view
(Reverse-Towne projection)

Position of the patient for Reverse-TowneReverse-Towne
projectionprojection using cephalometric machine

N.B: Town’s projection is the antero-
posterior one.
It clearly defines all but the most superior
parts of the condylar processes. Thus it
often gives critical diagnostic aid in
determining the presence of unilateral or
bilateral condylar fractures, especially for
the fractures running in the sagittal plane.

Submentovertx projectionSubmentovertx projection
(base view)(base view)
This view used to exam the base of the
skull, condyles, sphenoid sinus, curvature of
the mandible, fractured zygomatic arch,
and foramina of the base of the skull.

Film placement: the cassette is placed vertically
in a holding device.
Head position: patient’s head is fully extended
backward as far as possible with the vertex of
the skull touches the center of the cassette.
Projection of central ray: the central ray is
directed from below the mandible upward
toward the vertex of the skull.

Submentovertx projection: (base view)Submentovertx projection: (base view)

Submentovertx projectionSubmentovertx projection
(base view)(base view)
(Reverse-Towne projection)Occiptomental projection
PA
Water’s view Mandibular
Posterioanterior view

Mandibular Lateral oblique
projections.
They are two lateral oblique projections used to
examine the mandible: one for the body and one
for the ramus.
The film used in these projections usually a 5X7
inch (13X18cm) screen film and the cassette
should be hand held by the patient.
Although these views have been replaced by
panoramic radiographs, dentists still use them
when an image with greater resolution is
needed.

Mandibular body projection
This projection demonstrates the premolar-molar region and
the inferior border of the mandible.
 Head position: the head is tilted toward the side being
examined.
 Film Placement: the cassette is placed against the patient’s
cheek and centered over the first molar, its lower border
parallel with the inferior border of the mandible extending at
least 2cm below it and the patient can hold the cassette.
 Projection of the central ray: The central ray is directed toward
the first molar region from a point 2cm below the angle on the
tube side.

The central ray is directed toward the first molar
region from a point 2cm below the angle on the tube
side.

Mandibular body projection

Mandibular Ramus ProjectionMandibular Ramus Projection
It gives a view of the ramus from the angle
of the mandible to the condyle.
It is useful for examination of the third
molar regions of the maxilla and mandible.

Head position: The head is tilted toward the side of the mandible
being examined until a line between the mandible angle next to
the tube and the condyle away from the tube (condyle of the
side to be examined) is parallel with the floor. The patient
asked to protrude his mandible to avoid superimposition of the
cervical spine.
Film placement: The cassette is placed over the ramus and far
enough posteriorly to include the condyle.
The lower border of the cassette should be parallel to the
inferior border of the mandible and at least 2cm below it.
Projection of the central ray: The central ray is directed
posteriorly towards the center of the ramus of the side of
interest from a point 2cm below the inferior border of the first
molar region of the other side

Mandibular Ramus ProjectionMandibular Ramus Projection

Thank you all for listening
Dr. Ossama El-Shall
Associate professor of Oral Medicine
& Periodontology, Faculty of Dental
Medicine, Al-Azhar University,
Cairo, Egypt.
E-mail address: oelshall@hotmail.com

Specialized radiography

Specialized radiography.Specialized radiography.
Panoramic radiography.
Computed Tomography.
Sialography.
Ultrasonography.
Magnetic resonance image.
Nuclear medicine. (Radio nuclide imaging )
Digital imaging.
Arthrography.
Electronic thermography.
Endoscopy.

Panoramic radiography
rotational radiography, or curved surface
tomography
It is a radiographic technique for
producing a single image of the facial
structures that includes both maxillary and
mandibular arches and their supporting
structures.

PanoramaPanorama
Panoramic radiography is an extraoralPanoramic radiography is an extraoral
radiographic technique that is used toradiographic technique that is used to
examine the upper and lower jaws on a singleexamine the upper and lower jaws on a single
filmfilm ..
The film and the tubehead rotate aroundThe film and the tubehead rotate around
the patient, producing a series of individualthe patient, producing a series of individual
imagesimages ..

As Tomographic principles, the x-ray
tube and film cassette rotate in opposite
directions around the patient’s head to
produce a specific curved image of the
maxilla and mandible on the film.

Panoramic principles are combination
of Scanography and Tomography
principles.
In order to understand the principle of
panoramic radiography, we have to
explain the meaning and principles of
both Tomography and Scanography

Tomography
Conventional film-based tomography is a special
radiographic technique designed to image more
clearly objects lying in a plane of interest.
This is accomplished by focusing on the plane of
interest and blurring the image of structures
lying superficial and deep to this plane.
Word Tome in Greek = Section

Conventional tomography is applied
primarily to high contrast anatomy, such
as encountered in dental implant
diagnostics.
In the other word, we can define the
tomography as a radiographic
presentation of a layer within the body
while body structures above and below
that layer are blurred out of focus.

Tomographic methods are divided into 2
major categories:
I- Conventional tomography.
II- Computerized tomography (C.T).

Scanography
Scanography is a process by which an x-ray
tube and a dental film are linked together
through a mechanical linkage and rotate
around a fixed object (patient’s head).

In panoramic technique, during exposure,
the x-ray source moves in one direction
while the film moves in the opposite
direction
The area of the object in the center of this
movement will appears in focus and very
sharp on the resultant radiograph as its
shadow.
All other structures will appears blurred or
out of focus

Advantage of panoramic radiography
1. Give a complete image for both jaws as well as
cervicofacial bones to exam any abnormality
such as, fractures, tumors, cysts, impaction
anomalous of teeth , etc……..
2. Simple technique, as it requires less co-
operation of the patient especially handicapped,
children, and jaw-fractured patients.
3. Low patient radiation dose; it is about 3 times
less than the amount received via full mouth
Periapical survey (14 films).

4. Quick procedure, the time required to
complete a panoramic radiographic
examination is quite short, usually in the
range of 3-4 minutes; this includes the
time necessary for positioning and the
actual exposure cycle (about22 sec.)
5. Panoramic films are readily accepted by
patients as a visual aid in case
presentation and for patient education.

Disadvantages:
The resultant Image does not resolve the fine
anatomical details that may be seen on intra-oral
Periapical radiographs.
Interproximal caries and changes of lamina dura
can not be diagnosed in most cases due to lack of
fine details and sharpness.
Magnification, geometric distortion and
overlapped images of teeth, especially in the
premolar region.

4. Due to superimposition of the spine, specially in
short-necked patients, there is always lack of
clarity in the central portion of the film (Ghost
shadow appearance of the spine)
5. Soft tissues and air shadows can overlie the
required hard tissue
6. High coast, 2-4 times that of an intra-oral X-ray
machine.

Indications:
1. Overall view of the teeth and facial bones.
2. Evaluations of trauma, extensive disease, tumor
extension, fracture, and gross swelling.
3. It reveals fractures of the mandible from the
midline to the neck of the condyle.
4. Cases of truisms, to locate or exam impaction,
pathology or fracture.
5. It reveals the maxillary sinuses floor of the orbits
and nasal bone.

6. Uncooperative patient, such as children, or
handicapped.
7. Full mouth survey instead of full mouth X-ray, 14
film.
8. Bilateral comparison of any pathology.
9. Orthodontic treatment
10. Evaluation of tooth development (especially in the
mixed dentition), retained teeth or root tips (in
edentulous patients), and developmental
anomalies.

Contra-indications:
Panoramic films are not suitable for
diagnostic examinations requiring high
image resolution, such as detection of early
bone loss, dental caries, periodontal
diseases, or analysis of trabecular bone
changes associated with early Periapical
lesions.

Patient preparation and position for
panoramic radiography
Remove all Radiopaque things such as; hairpins,
earrings, removable partial dentures …..
Set the patient in upright position putting the head
in focal trough guided by Bite block placed between
upper and lower incisal edges.
So this brings the arches in the center of focal
trough leading to correct anteroposterior direction
of image.

Two ear rods to adjust midsagital plane in correct
position to avoid any horizontal distortion of
magnification of one side more than other.
Chin positioning to adjust Frankfort plane
parallel to floor.
Demonstrate the machine movement to the patient
especially to the children.
Instruct the patient to look forward and don’t
follow the tube by his eyes.
Leaded apron

Computerized Tomography
C.T.

C.T.
1. Simply the computed tomographic scanner consists
of a multiple radiographic tubes with narrow
beams that are mounted in a circular gantry
opposite an array of scintillation receptors designed
to accept these beams.
2. The patient is placed in the center of the gantry and
the gantry rotates, allowing the x-ray beams to
irradiate patient from various angles.
3. The receptors record the radiation passing through
each small section of the patient and convert it into
electric impulses, which are sent to a computer for
storage and manipulation.

4. It provides excellent imaging of TMJ, salivary
gland, facial fractures and lesions, and tumor
extension and assists in the positioning of implants.
5. It completely eliminates the superimposition of
images of structures superficial or deep to the area
of interest within the patient.
6. It give a good differentiation between tissues due to
its high contrast resolution
7. The main disadvantages of it that, anything denser
than enamel produces serious artifacts. This causes
some problems when examining the jaws of patients
with metal restorations or implants.

Fracture zygomatic arch Rt. side

Coronal scanning of TMJ

Chronic sinusitis in max.
sinus

Sialography
It is a technique whereby a radio-opaque
contrast medium is injected into the main
parotid or submandibular salivary gland
duct via a cannula, in order to
demonstrate the anatomy of the duct
system.

Indications:
1-1- Chronic inflammatory diseases of salivary glands:Chronic inflammatory diseases of salivary glands:
A-A- Chronic obstructive inflammation : Abnormalitis in the main ductChronic obstructive inflammation : Abnormalitis in the main duct
due to obstructive agent eitherdue to obstructive agent either calculus or non-calcifiedcalculus or non-calcified..
Sialography will aid in planning surgery i.e. deciding whether total orSialography will aid in planning surgery i.e. deciding whether total or
partial excision of gland should be performed.partial excision of gland should be performed.
B-B- Chronic non-obstructive: Sjogran’s syndrome & Recurrent parotitis.Chronic non-obstructive: Sjogran’s syndrome & Recurrent parotitis.
2-2- Detection of tumors.Detection of tumors.
3-3- Detection of residual stones, residual tumor, fistula, orDetection of residual stones, residual tumor, fistula, or
retention cyst following surgical procedure in salivary gland.retention cyst following surgical procedure in salivary gland.
4-4- Detection of congenital defect such as atrophy andDetection of congenital defect such as atrophy and
hyperatrophy.hyperatrophy.

Contraindications:
1- Sensitivity to iodine compounds of the contrast
materials.
2- During acute inflammation of salivary system;
where may be disrupted leading to escape of
contrast material from ducts into parenchyma
inducing severe foreign body reaction and pain.
3- The iodinated contrast medium may interfere
with thyroid function tests; hence they should be
performed prior to sialography.

Complications:
1- Spread of infection, discomfort, and pain.
2- Extravasations of contrast medium may
result in foreign body reaction.

Radio-opaque contrast materials:
It is a diagnostic agent appears Radiopaque in
radiographs. It injected in the salivary glands and
its duct systems to exam them radiographically.
Specifications of contrast media:
1. Sufficient radio-opacity to represent the fine structures.
2. Must have physiologic properties similar to saliva, to
facilitate penetration into the fine ducts.
3. Low viscosity to allow filling of the ductal system.
4. Rapid absorption of the residues by blood and excretion
by the kidney and salivary gland.
5. Non-toxic and easy to detoxicated by the liver.

It may be one of the following:
Water-soluble.
Fat- soluble.
Suspension media.

Water soluble (most preferable), e.g.:
Renografin,
Sinografin,
Hypaque.
They have the following advantages:
1. Low viscosity, so they can fill the ductal system with
little pressure.
2. Rabidly absorbed by blood.
3. Similar to saliva.
4. Little pain and discomfort.
5. Little inflammation.

Fat soluble; e.g.:
Lipiodol,
Pantopaque,
They are:
1. Highly viscous, need more pressure to injection (painful).
2. Give high radio-opacity.
3. Take a long period to eliminate from the gland, so it
gives an enough time to take the radiograph, and in the
same time cause inflammation and discomfort.
4. Unstable; it easily to oxidized in the presence of air.
Suspension contrast media; e.g. Hytrast. It has a
good radio-opacity and high viscosity.

Procedures of Sialography:
1. Primary plain film evaluation. Post. ant.,
Occlusal, and lateral oblique.
2. Injection or filling phase, and radiograph
for Sialography.
3. Evacuation phase: stimulated more by
using lemon juice.

Sialography of submandibular
gland

Sialography of parotid
gland

Stone within the Wharton’s duct of
submandibular gland

Stone in Wharton’s duct.Stone in Wharton’s duct.

Ultrasonography
1. This technique used sound as sonar to image
structures deep within the soft tissues. The sound
used for diagnosis lie above the audible range and
is referred to as ultrasound.
2. As sound passes through any material, it meets a
certain level of resistance.
3. Hence, Ultrasonography could be defined as the
imaging of deep structures by measuring the
reflection or transmission of the ultra-sonic waves.

Mechanism of action:
1. A transducer first produces Sound waves.
Transducer constructed of a piezoelectric materials,
such as lead zirconate titanate, which converts
electrical signals into sound waves, which are
transmitted into the tissues as a series of pulses.
2. The transducer also receives sound waves, which are
reflected from back from the tissues, and converts
them into electrical signals for processing into an
image.

3. As sound travels through the tissues it loses
energy by absorption, but a small proportion of
the sound is reflected back from the boundaries
of tissues. The reflected waves are received by the
transducer and displayed on a monitor and
recorded.
4. Air and bone do not readily transmit ultrasound
wanes hence limiting the usefulness of ultrasound
imaging in the maxillofacial region. It is,
however, of value in the examination of space
occupying lesions in the soft tissues, including for
examination of the paroted gland, cervical lymph
nodes, and oral soft tissues as lips and tongue.

Ultrasound
echoes

Magnetic Resonance Imaging.
(MRI)
Magnetic resonance imaging is a
technique, which uses a combination of
magnetic fields and radio-frequency
waves to generate images of the body.

Able to image soft tissue without
contrast agents
Magnetic Resonance
1. Magnetic field aligns atoms (Hydrogen)
2. Radiowaves alter alignment
3. Atoms realign, releasing energy
4. Computer produces image
NO IONIZING RADIATION

Instead of detecting tissues by the x-ray, magnetic
resonance detects the presence of hydrogen nuclei
through their resonance in a magnetic filed.
Human tissues consist of molecules containing
hydrogen nuclei (protons). Each proton has an axial
spin and, because of its charge, behaves as a small
magnet, have both north and south poles.
Normally the protons are randomly arranged;
however, when the patient is placed in a strong
magnetic field, the direction of the spine of the
protons aligns with that of the filed.

The application of a pulsed resonant radio-
frequency waves, causes the protons to tilt
away from the magnetic filed. Once radio-
frequency waves are turned off, the protons
return to their preferred alignment with the
magnetic filed, and gives off the acquired
radio wave signals.
Magnetic Resonance Imaging is the process
of locating these individual protons radio-
signals in a three dimensional visual image.

To produce a MR image. The patient is placed
inside a large magnet, which induce a relatively
strong static magnetic field. This cause the nuclei
of many atoms in the body, including hydrogen to
align them with the magnetic filed.
Magnetic resonance imaging specifically image the
presence of H2 nuclei, water, lipids and the degree
of H2 are bound with molecules. So the tightly
bound hydrogen atoms as in bone appears black as
that of cortical plate, and loosely bound or mobile
H2 atoms such that of salivary glands and liquids
appears gray.

Magnetic Resonance
radiofrequency
coils
Magnet
(0.5 – 2.0 tesla = 5,000 – 20,000 gauss)
sliding table

Advantages:
Excellent soft tissues imaging especially T.M.J and
salivary glands without radiation exposure or
contrast media injection.
Disadvantages:
1. Long scan time.
2. Some patients can not stay motionless for long
times.
3. Noisy MR scanner
4. Any vascular clips can move due to magnetic filed.
5. High coast.

Radio Nuclide Imaging or Scintiscaning
It involves the injection of radioactive compounds
with special affinity for particular tissues and later
detection of them by means of external detectors
and imaging systems.
It reflects the early biochemical changes occurred
in bone metabolism that may precede architectural
changes. So this technique has the potential to
detect the earliest stages of bone loss.

The radioactive compounds called radio
pharmaceuticals (isotopes). After injection them
intravenously they uptake by the target tissues
and concentrate in them. Then they located in
this target tissues by means of a special detector
such as gamma camera.
For examination of bone metabolism; used a
bone seeking radiopharmaceutical such as
Diphosphonate compound 99M Tc.

Gamma camera

Scintiscaning

Arthrography
It is technique for radiographic examination of a
joint following the introduction of a contrast
medium into the joint spaces to observe
indirectly the non-mineralized components of
T.M.J.
It is indicated to exam the damage of intra-
articular soft tissues of T.M.J., displacement of
the discs, and synovial perforations or adhesions.

Electronic Thermography
Thermography; It is methods of temperature
pattern resduation and analysis.
Its use in diagnosis based on fact that; the disease
processes and/or abnormal conditions may result in
different temperature patterns because of
alterations in blood supply or the presence of
inflammation.
Sensors used to record temperature may be, small
electronic probe called thermisters.
It used to determining T.M.J. changes or pocket
temperature.

Endoscopy
It is a technique used for examination of
the maxillary sinus; by introducing an
endoscope into the sinus to allow
visualization of its interior and the mucous
membrane linings; as it gives information,
which are not shown by any other method.

Examination of salivary glands
1. Plain radiography:
1. Intra-oral Occlusal films.
2. Extra-oral: lateral oblique, Post. ant.;
2. Sialography.
3. Ultrasonography.
4. C.T.
5. MRI.

Examination of maxillary sinus
1. Plain radiography
1. Intra-oral films: periapical and Occlusal.
2. Extra-oral films: Water’s and true lateral
2. Tomography.
3. Endoscopy.

Imaging of the Temporomandibular
joint.
The TMJ is technically one of the mostThe TMJ is technically one of the most
difficult areas of the body to visualize welldifficult areas of the body to visualize well
because of multiple adjacent osseousbecause of multiple adjacent osseous
structures. The common imaging modalitiesstructures. The common imaging modalities
performed to exam the TMJ are:performed to exam the TMJ are:

Tomography.Tomography.
Arthrography.Arthrography.
Transcranial views.Transcranial views.
Transorbital views.Transorbital views.
Skull views: Waters, Submentovertex andSkull views: Waters, Submentovertex and
Reverse-Towne projections.Reverse-Towne projections.
Panoramic views.Panoramic views.
Magnetic resonance imaging.Magnetic resonance imaging.
Computed Tomography.Computed Tomography.

Anatomy of TMJ
Lateral view

Transcranial viewsTranscranial views
It provides a reasonably true projectionIt provides a reasonably true projection
through the long axis of the joint.through the long axis of the joint.
Cassette position:Cassette position: Against the facial skinAgainst the facial skin
surface on the side of interest, parallel tosurface on the side of interest, parallel to
the sagittal plane.the sagittal plane.

Central x-ray:Central x-ray: the tube on the contra lateral sidethe tube on the contra lateral side
of the skull and the central beam directedof the skull and the central beam directed
downward 25 degrees,downward 25 degrees,
anteriorly 20 degrees andanteriorly 20 degrees and
is centered on the TMJ.is centered on the TMJ.
The central ray is orienteddownward25 degree.

The central ray is oriented anteriorly 20 degree s centered on the TMJ of interest.
The central beam downward 25 degrees,The central beam downward 25 degrees,
anteriorly 20 degrees and is centered on theanteriorly 20 degrees and is centered on the
TMJ.TMJ.

The central beam is projected across theThe central beam is projected across the
cranium above the petrous ridge of thecranium above the petrous ridge of the
temporal bone on the film side and exitstemporal bone on the film side and exits
through the long axis of the condyle.through the long axis of the condyle.

The routine Transcranial radiographic seriesThe routine Transcranial radiographic series
includes projections of both left and right joints inincludes projections of both left and right joints in
the closed and wide-open jaw positions.the closed and wide-open jaw positions.

The observer must remember that theThe observer must remember that the
Transcranial view displays only the lateralTranscranial view displays only the lateral
aspects of the condylar head and theaspects of the condylar head and the
articular fossa in profile.articular fossa in profile.
Thus, Transcranial radiography may showThus, Transcranial radiography may show
minute, subtle bony irregularities on theminute, subtle bony irregularities on the
lateral bony surfaces but is far lesslateral bony surfaces but is far less
instructive of similar changes that occur ininstructive of similar changes that occur in
the central and medial joint areas.the central and medial joint areas.

Transorbital viewsTransorbital views
Zimmer projectionZimmer projection
It is the conventional frontal TMJ projectionIt is the conventional frontal TMJ projection
that is most routinely successful in delineatingthat is most routinely successful in delineating
the joint with minimal superimpositions.the joint with minimal superimpositions.
The advantages of this projection areThe advantages of this projection are
1-1- The lack of major superimpositions over mostThe lack of major superimpositions over most
of condylar processof condylar process
2-2- Production of true frontal projection of theProduction of true frontal projection of the
condyle, through directing the central raycondyle, through directing the central ray
perpendicular to the long axis of the condyleperpendicular to the long axis of the condyle
3-3- Simple tech.Simple tech.

Head positionHead position: patient seat upright and tip the head: patient seat upright and tip the head
downward about 10 degrees so the canthomeatal line isdownward about 10 degrees so the canthomeatal line is
horizontal.horizontal.
turn head 20° to the side of interest.turn head 20° to the side of interest.
Cassette positionCassette position: behind the patient‘s head so that the: behind the patient‘s head so that the
central ray is projected to its center and perpendicular oncentral ray is projected to its center and perpendicular on
it.it.
The central raysThe central rays:directed through the ipsilateral orbit and:directed through the ipsilateral orbit and
through the TMJ of interest, exiting from the skull behindthrough the TMJ of interest, exiting from the skull behind
the mastoid process.the mastoid process.
x-ray tube directed +35° , from the front through the floorx-ray tube directed +35° , from the front through the floor
of the left orbit and left TMJof the left orbit and left TMJ
Ask patient to open the mouth as wide as possibleAsk patient to open the mouth as wide as possible

Digital imaging.
It is a conversion of dental radiograph into digital
data in forms of numbers; small points or
subdivisions called pixels or picture elements.
This pixels are posed in rows and columns called
matrix and each pixel is assigned a gray scale value
i.e. a digital value corresponding to the point on the
x-ray.
The quality of any digitized radiograph depends on
the number of pixels and the number of gray levels,
which make up the image.

In conventional intra-oral radiograph film consistsIn conventional intra-oral radiograph film consists
of silver halide grains in a gelatine matrix. When thisof silver halide grains in a gelatine matrix. When this
film is exposed to X-ray photons the silver halidefilm is exposed to X-ray photons the silver halide
crystals are sensitized and are reduced to black duringcrystals are sensitized and are reduced to black during
the developing process. The film acts as both thethe developing process. The film acts as both the
radiation detector and the image display.radiation detector and the image display.
With extra-oral films indirect action receptors areWith extra-oral films indirect action receptors are
used to help record the image. This types of film isused to help record the image. This types of film is
sensitive to light photons which are emitted bysensitive to light photons which are emitted by
adjacent intensifying screens. Although the film isadjacent intensifying screens. Although the film is
constructed of silver halide crystals these are primarilyconstructed of silver halide crystals these are primarily
sensitive to light rather than X-rays.sensitive to light rather than X-rays.
Digital imaging.

In digital radiography, instead of the silver halide grain theIn digital radiography, instead of the silver halide grain the
image is constructed using pixels or small light sensitive elements.image is constructed using pixels or small light sensitive elements.
These pixels can be a range of shades of grey depending on theThese pixels can be a range of shades of grey depending on the
exposure, and are arranged in grids and rows on the sensor, unlikeexposure, and are arranged in grids and rows on the sensor, unlike
the random distribution of the crystals in standard film.the random distribution of the crystals in standard film.
However, unlike film the sensors are only the radiation detectorHowever, unlike film the sensors are only the radiation detector
and the image is displayed on a monitor.and the image is displayed on a monitor.
The signal that is produced by the sensor is anThe signal that is produced by the sensor is an
analogue signal, i.e. a voltage that varies as a functionanalogue signal, i.e. a voltage that varies as a function
of time. The sensor is connected to the computer andof time. The sensor is connected to the computer and
the signal is sampled at regular intervals. The output ofthe signal is sampled at regular intervals. The output of
each pixel is quantified and converted to numbers by aeach pixel is quantified and converted to numbers by a
frame grabber within the computer. The range offrame grabber within the computer. The range of
numbers is normally from 0 to 256 with 0 representingnumbers is normally from 0 to 256 with 0 representing
black, 256 representing white and all others are shadesblack, 256 representing white and all others are shades
of grey.of grey.

Digital radiography may be:
Direct Digital Radiography: (DDR)
It is a film less radiographic imaging system which
involves the electronic generation of high-resolution
computer monitor images or thermal print image
from an intra-oral sensor.
Indirect Digital Radiography: (IDR)
On which dental film will used to give the
information through scanner to the digital computer
system. (Digora system), (Computer assisted
densitometric image analysis system, CADIA),
Subtraction radiography).

Full mouth series. Red rectangle highlights selected film

Magnified image

Adjust brightness, contrast
contrast
brightness

“Flashlight” feature

Measuring curved root

Combining intraoral/radiograhic

Colorization

Digital extra-oral images

Digital Subtraction Radiography
+

Application of digital subtraction radiography
for detection and quantification of periodontal
bone healing in a clinical research setting;
(a), base-line image.
(b), 1-year follow-up image.
(c), subtraction image showing bone gain (arrow).

(a) Original base-line image taken immediately post-surgery,
(b) Follow-up image taken after placement of final restoration,
(c) Subtraction image showing bone loss at alveolar crest and bone
gain at the bone-implant interface.

Thank you all for listening
Dr. Ossama El-Shall
Professor of Oral Medicine & Periodontology,
Faculty of Dental Medicine, Al-Azhar
University, Cairo, Egypt.
E-mail address: oelshall@hotmail.com

•Digital radiographs are one of the newest X-ray techniques
around. Because it is so new and because the machines can be
so expensive, your dentist may not have it yet; but watch for
this process to become standard in the future. With digital
radiographs, film is replaced with a flat electronic pad or
sensor. The X-rays hit the pad the same way they hit the film.
But instead of developing the film in a dark room, the image is
electronically sent directly to a computer where the image
appears on the screen. The image can then be stored on the
computer or printed out. One of the great advantages of this
process is that radiographs can be digitally compared to
previous radiographs in a process called subtraction
radiography. The computer can digitally compare the two
images, subtract out everything that is the same and give a
clear image of anything that is different. This means that tiny
changes that may not be noticeable with the naked eye can be
caught earlier and more clearly with digital-subtraction
radiography. Subtraction radiography requires a specialized
projection technique and additional software.

Arrange the bitewings to form a smile with
the external oblique ridge at the extreme
right and left with premolars toward the
midline and molars away from the midline.

Arrange the horizontal posterior periapicals around
the bitewings, matching the restorations and missing
teeth. Look for maxillary posterior structures like the
zygomatic process and maxillary sinus and mandibular
structures like the external oblique ridge and mental
foramen.

Arrange the horizontal posterior periapicals around the
bitewings, matching the restorations and missing teeth.
Look for maxillary posterior structures like the
zygomatic process and maxillary sinus and mandibular
structures like the external oblique ridge and mental
foramen.

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