Radiograph sem

Radiographic techniques
R.Hemalatha
1st year
Dept. Of Pedodontcs and Preventive Dentistry

Contents…

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Introduction
Parts of X-ray tube
Projection Geometry
Principles of projection geometry
Terms
Focal spot
Magnification
Distortion
Heel effect
Intra oral radiographs
Periapical radiography
1. Paralleling technique
2. Bisecting angle technique
• Bite wing radiography
• Occlusal radiography

Contents…

• Placement of the film in children and its
management
• Full mouth radiography
• Object localisation technique
• Radiographic faults
4. Extraoral techniques
• Lateral cephalometric projections
• Submentovertex projections
• Waters
• Posteroanterior cephalometric
• Reverse-towne projections
5. Digital radiography and advanced imaging
techiques
6.Effects of dental radiographs in oral cavity
7.Radiation protection
8. Conclusion
9.Refrences

Introduction
• Radiograph is a 2D image of a 3D object.
• A good radiograph is required for use as a good
diagnostic aid.
• Principles of projection geometry teach us how to
reach perfection during radiography.
• The intraoral radiograph, when correlated with the
case history and clinical examination, is one of the
most important diagnostic aids to the dental
practitioner.

Parts of X-Ray

An X-ray tube is a vacuum tube that produces X-rays.
They are used in X ray machines. X-rays are part of
the electromagnetic spectrum, an ionizing radiation with
wavelengths shorter than ultraviolet light.

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As with any vacuum tube, there is a cathode, which emits electrons into the
vacuum and an anode to collect the electrons, thus establishing a flow of
electrical current, known as the beam, through the tube.
A high voltage power source is connected across cathode and anode to
accelerate the electrons.
The X-Ray spectrum depends on the anode material and the accelerating
voltage.
Electrons from the cathode collide with the anode material, usually tungsten,
molybdenum or copper, and accelerate other electrons, ions and nuclei within
the anode material.
About 1% of the energy generated is emitted/radiated, perpendicular, rest of
the energy is released as heat.

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tungsten will be deposited from the target onto the interior surface of
the tube, including the glass surface.
The arc will jump from the cathode to the tungsten deposit, and then
to the anode. This arcing causes an effect called "crazing" on the
interior glass of the X-ray window, tube becomes unstable even at
lower voltages, and must be replaced.
The X-ray photon-generating effect is generally called
the Bremsstrahlung effect.
emitted X-ray photons, or dose, are adjusted by controlling the
current flow and exposure time (high voltage controls X-ray
penetration, and thus the contrast of the image and tube current and
exposure time affect the dose and darkness of the image.
Aluminum filters are installed in the path of the X-ray beam to
remove "soft" (non-penetrating) radiation.

• Fundamentals of radiography areCentral beam should pass through the area
to be examined.
The x-ray film should be placed in position
so as to record the image with the least
amount of image distortion

Principles of Projection Geometry…

Object and Film should be in contact or as
close together as possible.

Object and film should be parallel to one
another.

X-ray tube head should be positioned that,
beam meets both the object and film at right
angles.

“Terms and conditions apply”
• Image sharpnessThe ability of a radiograph to reveal the boundary between two
areas of different radiodensity; or to define an edge precisely.
• Image spatial resolutionOPG- 5line
Ability of a radiograph to reveal
pairs/mm.
small objects that are close together.
IOPAR- 20line
Line pairs per mm.
pairs/mm.

• Image size distortionIt is the increase in size of the image on the
radiograph compared with the actual size of the
object.

• Image shape distortionIt is the unequal magnification of different parts of
the same object on a single radiograph.

• Actual focal spot size= 1x3mm.
• Effective focal spot size= 1x1mm.
• Size of the EFS- Angulation of the anode target to
the long axis of the incident electron beam from
the cathode.
• Ideal angle= 10-20o
• Smaller effective focal spot
size, increased image
sharpness and resolution.

Focal spot

• Dec. heat
production
• Inc. X-ray tube
life
• Dec. sharpness
and resolution
• Dec. clarity
• Inc. “geometric
unsharpness”

• Inc. heat production
• Dec. X-ray tube life
• Inc. sharpness and
resolution
• Inc. clarity

Umbra and Penumbra
BLURRING
To have sharp
edge of image:
• Longer “a”
• Reduced
“b”
• Smaller
EFS

Fuzzy edgeGeometric
Unsharpness

Magnification
• Formula= Size of the image = Focal spot to film distance
Size of the object Focal spot to object distance
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When an image is magnified, the shape is maintained because every
dimension of the object is magnified to the same extent, provided the
object is placed parallel to the film.

 Use large
FS to
object
distance
 Use
small
object to
film
distance

Distortion
• Results from unequal magnification of
different parts of the same object.
• When not all the parts of the object are
at the same FS to object distance.
 Position the film
parallel to the
object.
 Orient the
central ray
perpendicular to
the film and the
object.

Foreshortening
Ray perpendicular to the
film but not the object

Elongation
Ray perpendicular to the
object but not the film

Heel effect
• Intensity of x-rays are not
uniform over the area
irradiated.
• Due to the electrons having
to travel more through the
anode, less energy and intensity
beam is seen towards the anode
than towards the cathode ,
photons get absorbed by the target anode
it self..

Biobrain article

Increases with increase in
anode angle steepness

Increases with increase in
roughness of the anode

Heel Effect
Decreases with increase
in focal spot to film
distance

Decreases with decrease
in film size

Periapical
radiographs

INTRA
ORAL
RADIOGR
APHS
Occlusal
radiographs

Bite wing
radiographs

Intra Oral Periapical
Radiography…
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Includes the teeth and the tissues around the apices.
UsesDetection of apical infection/ inflammation.
Assessment of periodontal status
Assessment of an unerupted tooth
Assessment of root morphology
Evaluate position and prognosis of implants

• Ideal positioning requirements• Tooth and film should be as close to each other as
possible.
• Tooth and film should be parallel to each other.
• The film is positioned with its long axis vertical for
anterior teeth and horizontal for posterior teeth.
• Beam must be directed at 90o to both the teeth and the
film.
• Positioning must be reproducible.

Placement of the film…
• The white side of the film always faces the
teeth.
• Anterior films are always placed vertically.
• Posterior films are always placed
horizontally.
• The identification dot on the film is always
made to face the operator and on the
occlusal end of the radiograph.
• The film is always centred over the areas to
be examined.
• Ideally 2mm of the alveolar bone must be
seen periapically.

Landmarks used…

Inner canthus
Pupil

Outer canthus

Occlusal Plane

Paralleling Technique
• C. Edmund Kells in 1896
• developed by Gordon M.
Fitzgerald in 1947.
• Used by Franklin W.
McCormack in practical
dental radiography.
• It was so named because the
object (tooth), receptor (film
packet), and end of the
position indicating device
(PID) are all kept on parallel
planes.

PRINCIPLE
The image sharpness is primarily affected by the distance from the focal
spot within the tube head and the film, object-film distance, motion, and the
effective focal spot size of the x-ray tube.

• Long axis of the tooth is
parallel to long axis of the film
• Central ray at 90o to both.
• Film holder and x-ray tube head
positions can be reproduced.
• Film placed at same distance
away from the tooth.
• Long open ended aiming cylinder
Long con tech
Right Angled tech
Dentomaxillofacial Radiology (2011) 40, 385-389
The British Institute of Rdiology

• Projection method• Maxillary projections, superior border of the
film placed at the height of the palatal vault.
• Mandibular projections, inferior border of the
film placed on the floor of the mouth.
• Vertical angulation- 90o
• Horizontal angulation- 0o
Now more commonly used method

• Film holders• Rinn XCP, Rinn stabe film holders, Precision film
holders, EEZEE grip film holders.
• Most preferred is Rinn XCP film holder
• Parts- Plastic ring and plastic bite block, metal
indicator arms, addable ring
collimators.

-Film placement
in children or
small mouths or
shallow palate is
difficult.
-Discomfort
-Apices of the
teeth may appear
close to the edge
of the film.
-Film holder
needs
autoclaving.

DISADVANTAGES

distortion
-Simplicity
-Duplication is
possible due to
standardisation
-Periodontal bone
levels are well
depicted.
-Angulations and
positions are
reproducible.
-The technique
reduces the risk of
cone cuts.

ADVANTAGES

-Accuracy, minimal

Bisecting Angle Technique
• Developed by Weston Price
in 1904.
PRINCIPLEWhen the rule of isometry is used, the
length of the tooth is equal to the length
of the image on the radiograph.

Multirooted
teeth- Angled
differently for
each root

Ciezynski‟s rule of
isometry

• Projection method• For maxillary projections- Patient‟s head must be
upright, with the sagittal plane vertical and the
occlusal plane horizontal.
• For mandibular projections- Head is tilted back
slightly.

• Size of Intraoral films
• Size 0 (22x35mm) used for bitewing and periapical
radiographs of small children
• Size 1 (24x40mm) used for radiographing anterior teeth
in adults.
• Size 2 (31x41mm) used for anterior occlusal
radiograph,periapical radiograph and bitewing survey in
mixed and permanent dentition.
• Occlusal films have a size of 57x76 mm and are taken for
viewing entire maxillary and mandibular arches

DISADVANTAGES

ADVANTAGES

- Can be used
without a film
holder.
- Decreased
exposure time.
- Positioning of the
film is relatively
more comfortable to
the patient in all
areas of the mouth.

- Image distortion.
- Angulation
problems.
- Unnecessary
exposure.
- Shadow of the
zygomatic bone
is frequently
seen over the
apex of the
maxillary
molars.
- Difficulty in
angulation.
- Not
reproducible.

Comparison of Parelleling
technique and bisecting angle
technique

Bite wing radiographs…
• Also called as the INTERPROXIMAL TECHNIQUE.
• Developed by Howard Riley Raper in 1925.
• Shows crowns of maxillary and mandibular teeth,
interproximal areas, and areas of crestal bone on the same
radiograph.
• Name originated as the patient bites on the wing to
stabilize the film.

• Uses• Checking the
interproximal areas
of teeth
• Checking the
alveolar bone on
the radiograph.
• Caries in
deciduous and
transitional
dentiton phase

AAAPD guideline for prescribing dental radiographs

• Vertical angulation- recommended
angulation of +10o. Used to
compensate for slight bend of the
upper portion of the film and tilt of
maxillary teeth.
• Horizontal angulation- central ray is
directed perpendicular to the curvature of
the arch and through the contact areas.
• Vertical bite wings are used to visualise
the level of the alveolar bone, normally
used as post treatment films after
periodontal treatment.

Occlusal radiograph…
• Occlusal radiography is defined as those intraoral
radiographic techniques taken using a dental X-ray set
where the film packet (5.7 x 7.6 cm) or a small intraoral
cassette is placed in the occlusal plane.

USES
I.
II.

III.

To precisely locate roots, supernumerary, unerupted
& impacted teeth.
To localize foreign bodies in the jaw & stones in the
duct of sublingual & submandibular gland duct.

Another use-- To demonstrate & evaluate the
integrity of anterior, medial & lateral outlines of
maxillary sinus.

To obtain information about location, nature, extent
& displacement of fractures of mandible & maxilla.
v Patients with reduced mouth opening
vi. Cleft palate cases
IV.

Maxillary and Mandibular Occlusal Projections

i. Topographic projections
Shows anterior part of maxilla or mandible and the
anterior teeth.
The cone is placed between the eye brows on the
bridge of the nose.

Mandibular Occlusal Projections

i. Topographic projections
Shows anterior part of maxilla or mandible and the
anterior teeth.

• ii. Vertex projection
Shows the entire teeth present in the arch.

ii. Vertex Mandibular projection
( cross sectional projection)

iii. Posterior Lateral
projection
Shows the posterior part of
the maxilla and the upper
posterior teeth on one side.

iv. Pediatric
projection
Shows the anterior part of the
maxilla, used in children of
5years age or younger.

• iii. Posterior Oblique Mandibular
Occlusal projection

• Positioning the Radiograph
• Positioning the radiograph vertically in the mouth for both
periapical and bitewing radiographs reduces the distal
extension of the radiograph and may result in greater
tolerance by patients, especially those with a mild gag reflex.
• The vertical bitewing radiograph provides greater detail of the
periapical area.

Primary dentition (3 to 6 years)
Maxillary anterior occlusal projection
• Place no. 2 film with its long axis perpendicular to the sagittal
plane and the pebbled surface towards maxillary teeth.
• Direct the central ray at a vertical angulation of +60 degrees
through the tip of the nose towards the center of the film
Mandibular anterior occlusal projection
• Seat the child with the head tipped back so that the occlusal
plane is about 25 degrees above the plane of the floor.
• Place a no. 2 film with the long axis perpendicular to the
sagital plane and the pebbled surface towards the mandibular
teeth.
• Orient the central ray at -30 degrees vertical angulation and
through the tip of the chin towards the film.

Bitewing projection
• Use no. 0 film with paper loop holder.
• Place the film in the child’s mouth as in the adult
premolar bitewing projection.
• The image field should include the distal half ofthe
canine and the deciduous molars.
• Positive vertical angulation of +5 to +10 degrees.
Decidious maxillary molar periapical projection
• Use no. 0 film , Position the film in the midline of the
palate with anterior border extending to the maxillary
primary canine.
• The image field should include the distal half of the
primary canine and both primary molars

• Deciduous mandibular molar projection
Projection a no. 0 film
The exposed radiograph should show the distal half of
the mandibular primary canine and the primary molar
teeth.
• Mixed dentition(7 to 12 years)
Maxillary anterior periapical projection
Center a no.1 film on the embrasure between the central
incisors in the mouth behind the maxillary central and
lateral incisors.Center the film on the midline.

• Mandibular anterior periapcal projection
Position no.1 film behind the mandibular central and
lateral incisors
• Canine periapical projection
Position no. 1 film behind each of the canines.
Decidious and permanent molar periapical projection
Position no.1 or no. 2 film with anterior edge behind
the canine
• Posterior bitewing projection
Use no.1 or no. 2 films as previously described
Expose four bitewings projections when the second
permanent molars have erupted

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Probable Technical Errors
Improper placements of films.
Cone cutting
Incorrect horizontal angulations
Incorrect vertical angulations
Over exposure due to defective devices.
A high exposure of the patient to radiation because of
repetition of taking X-rays due to an uncooperative
child.

Radiation hygiene measures
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Proper registration and maintenance of radiographic units.
Training of personnel who are associated with radiography
Dosage monitoring
Radiation protection of the child patients by using lead apron
with thyroid collar.
Use of long lead-lined cylinder and cone positioning devices
Use of electronically controlled exposure timer
Use of high speed films
Use of automatic processing machines that give good
consistent result
Employing proper technique to avoid the chances of repeating
exposure

• The Snap-A-Ray is also useful for those patients that have a
fear of swallowing the radiograph.
• By biting on the large positioning device and watching in a
mirror they are assured they will not swallow the radiograph

A self sticking sponge tab may also reduce impingement of
the radiograph on the intraoral soft tissue.
For patients frightened of the procedure itself,desensitization
techniques may be necessary to gain the patient cooperation

Desensitization Techniques
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Desensitization is defined as gradually exposing the child to new
stimuli or experiences of increasing intensity.
• An example of this is introducing the patient to x-rays by initially
taking an anterior radiograph which is easier to tolerate than a
posterior radiograph.
“Lollipop Radiograph Technique.”The child is given a lollipop to lick
(preferably sugarless).
• After a few licks, the lollipop is taken from the child and a radiograph
is attached to the lollipop using an orthodontic rubber band.
• The lollipop with the attached film is returned
to the child, who is told to lick the lollipop again.
• After a few licks, the child is told to hold the lollipop in his mouth
while we take a tooth picture.The exposure is made

Procuring Posterior Radiographs
• Procuring posterior radiographs can be made more
pleasant by associating it with a pleasurable
taste….bubble gum.
• Before placing the radiograph in the patient’s mouth
apply bubble gum flavored toothpaste to the film.
• The child will be more accepting of the radiograph

Gag reflex
• Some patients, young and old, have an exaggerated gag
reflex.
• The etiology of an exaggerated gag reflex had been
attributed to psychological and physical factors.
• The easiest is through diversion and positive suggestion.
• The operator suggests to the patient the gag reflex can
be reduced by concentrating on something other than
the procedure.
• The patient’s palate can be sprayed with a topical
anesthetic to reduce the sensation of the radiograph on
the palate and tongue.
• An alternative is the use of nitrous
oxide analgesia

Newman and Friedman
Extraoral Radiographic Technique
• Another alternative is to place the radiograph in such a
manner to not come in contact with the palate or tongue.
• This is accomplished by either extraoral placement of the film
or placing the film between the cheek and the tooth and
exposing the film from the opposite jaw.
• The film side of the packet (the solid color side) is facing the
buccal surface of the tooth
• The x-ray head is placed at the opposing side, and the coneis
positioned under the angle of the ramus on the opposite side.
• As the x-ray beam is traveling a longer distance to the film
than in the typical positioning, it is necessary to double the
exposure time.
• It is imperative that after mounting radiographs are Reversed.
• Incorrect mounting and labeling of the reverse radiograph can
result in misdiagnosis and treatment of the wrong tooth
Newman M, Friedman, S. Extraoral Radiographic Technique: An
Alternative Approach. Journal Of Endodontics 2003;29:419-421

Modified Newman and Friedman Extraoral
Radiographic Technique
•

Eshagali Saberi, Ladan Hafezi, Narges Farhadmolashahi, Manoochehr Mokhtari

The patient sitting
upright and the
Frankfort plane being
horizontal to the floor
and when the head was
tilted 10 degrees toward
the side being
examined.

For the upper posterior
teeth the center of the
image receptor was
placed on the
intersection of the alatragus and a
parasagittal line while
the upper border of
receptor was parallel to
the canthomeatal line.

The cone was positioned
a negative 25 degrees
from the horizontal
plane.

Modified Newman and Friedman Extraoral
Radiographic Technique

The central beam
was directed from
midway between
maxillary and
mandibular
premolars and
molars of the
opposite side..

For the lower
posterior teeth, the
receptor was placed
against the cheek on
the side of interest
and its lower border
was parallel and 2
cm above the inferior
border of the
mandible

The cone was angled
-20 degrees from the
horizontal plane
while the central
beam was directed
towards the
mandibular molarpremolar region.

Saberi1, Hafezi L, Farhadmolashahi1 N, Mokhtari M. Modified
Newman And Friedman Extraoral Radiographic Technique

Type of encounter

Child with primary dentition
(prior erruption of 1st molar)

Child with
Transitional Dentition
(after eruption of first
permanent tooth)

Adolescent with
Permanent Dentition
(prior to eruption of
third molars)

New patient*
being evaluated for dental
diseases and dental
development

Individualized
radiographic exam
consisting of selected
periapical/occlusal
views and/or posterior
bitewings if proximal
surfaces cannot be
visualized or probed.
Patients without
evidence of disease and
with open proximal
contacts may not
require a radiographic
exam at this time.

Individualized
radiographic exam
consisting of posterior
bitewings with
panoramic exam or
posterior bitewings and
selected periapical
images.

Individualized radiographic
exam consisting of

Recall patient* with
clinical caries or at
increased risk for caries**

Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be
examined visually or with a probe.
.

Recall patient* with no
clinical caries and not at
increased risk for caries

Posterior bitewing exam at 12-24 month intervals
if proximal surfaces cannot be examined visually
or with a probe

Recall patient* with
periodontal disease

Clinical judgment as to the need for and type of radiographic images for the evaluation of
periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or
periapical images of areas where periodontal disease (other than nonspecific gingivitis) can
be identified clinically.

posterior bitewings with
panoramic exam or
posterior bitewings and
selected periapical
images.
A full mouth intraoral
radiographic exam is
preferred when the
patient has clinical
evidence of
generalized dental disease
or a history of extensive
dental treatment.

Posterior bitewing
exam at 18-36 month
intervals.

Type of Encounter

Child with Primary
Dentition (prior to
eruption of first
permanent tooth)

Child with
Transitional Dentition
(after eruption of first
permanent tooth

Adolescent with
Permanent
Dentition
(prior to eruption of
third molar

Patient for monitoring of
growth and development

Clinical judgment as to need for and type of
radiographic images for evaluation and/or
monitoring of dentofacial growth and development.

Patient with other
circumstances including,
but not limited to,
proposed or existing
implants, pathology,
restorative/endodontic
needs, treated periodontal
disease and caries

Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring
in these circumstances

Clinical judgment as to
need for and type of
radiographic images
for evaluation and/or
monitoring of
dentofacial growth
and development.
Panoramic or periapical
exam to assess
developing third
molars

• Large or deep restorations Indications for pediatric radiographs
• Malposed or clinically
•Poor oral hygiene
impacted teeth
•Inadequate fluoride exposureft in
• Mobilty of teeth
diet
• Sinus tract/ fistula
•Poor family dental health
• Clinically suspected sinus
•developmentrequentl high sucrose
pathology
content
• Oral involvement in known or
•Prolonged nursing bottle or breast
suspected systemic disease
feeding
• Unxplained bleeding,
•developmental or acquired enamel
sensistivity of tooth,
defects
• Unusual erruption,spacing or
• Developmental or acquired
migration of teeth, tooth
disability
morphology, calcification or
•
Xerostomia
colour, absence of teeth
•
Genetic abnormality of teeth
• Clinical erosion
•
Many multisurface restorations
• High level fo caries experience •
Chemo/radiation therapy
• Eating disorders
• h/o of reccurent caries
• Drug/alcohol abuse
• High titre of cariogenic titre
• Irregular dental care
• Exsisting restoration of poor
quality
AMERICAN ACADEMY OF PEDIATRIC DENTISTRY-2012

Radiographic Surveys
• The three most common series of radiographs taken in
the dental office are
• Bitewing Surveys- consist of a premolar view and a molar
view for each side of the mouth taken in occlusion (2 or
4 films) taken to examine the contact areas of the
premolar and molar regions, and periapicals for the other
teeth and edentulous areas.
• Full Mouth Surveys - series of x-rays that properly
represent every tooth in the patient's mouth (with 3 to 4
millimeters of surrounding bone) and all other tooth
bearing areas of the mouth even if edentulous
• panoramic film.

Full Mouth Radiographs

22 total=18 IOPA + 4 Bite wings

Deciduous Dentition
8 film= 6 IOPA + 2
Bitewings

Object localisation techniques…
•To determine the location of a foreign object or an
impacted tooth in the jaw.
•Two methods are used for localizing the object;
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Perpendicular techniqueUsed to localize an object in or about the maxilla or
mandible in three dimensions.
In clinical practice the position of an object on each
radiograph is noted relative to anatomic landmarks.
The right angle or cross section technique is best in
mandible
An IOPAR and an occlusal radiograph are used.

B. Tube shift technique (SLOB Method)
This method is also known as “buccal object rule” or “Clark‟s
rule”(1910)
Rationale for this technique derives from the manner in which
the relative positions of radiographic images of two
separate objects change when projection angle at which the
images are made is change.
Two radiographs are taken with different horizontal
angulations.

Quality Assessment…
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Depends onX-Ray equipment
Focusing
Image processing
Patient
Operator and radiographic technique.

• If radiograph quality is poor, diagnostic
information is lost.

i. Light radiographs

Underexposure• Insufficient milliamperage
• Insufficient peak
kilovoltage
• Insufficient exposure time
• FS- Film distance to much
• Film packet reversed
Processing errors• Underdevelopment (Low
temp, short time)
• Depleted developer
solution
• Diluted or contaminated
developer
• Excessive fixation

ii. Dark radiographs
Overexposure• Excessive milliamperage
• Excessive peak
kilovoltage
• Excessive exposure time
• FS- Film distance to short
Processing errors• Overdevelopment (high
temp, long time)
• Developer concentration
high
• Inadequate fixation
• Improper safe lighting
• Accidental exposure to
light

iii. Insufficient contrast
• Underdevelopment
• Underexposure
• Excessive peak
kilovoltage
• Excessive film fog

iv. Film Fog
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•

Improper safe lighting
Light leaks
Over development
Contaminated solutions
Deteriorated films

• Light leaks
• Turning on the
overhead white light
too soon
Light fog

Deterio
ration
Radiatio
n fog
of the
film
• Temperature of
• Improper storage
storage area too
• Insufficient
Chemical fog
high
protection
• Too high
• Developer
humidity
temperature too high
• Overdevelopment

v. Dark spots or line
• Finger print contamination
• Black wrapping paper sticking
to the film
• Film in contact with tank or
another film during fixing
• Film contaminated with
developer before developing
• Excessive bending
• Static charge to film before
processing
• Excessive roller pressure or
dirty rollers

vii. Light spots
• Film contaminated
with fixer before
processing
• Film in contact with
tank or another film
during development
• Excessive bending of
the film

viii. Yellow or Brown stains
• Depleted
developer
• Depleted fixer
• Insufficient
washing
• Contaminated
solutions

ix. Herring bone or tire track
appearence
• Placement of the
film backwards,
with the lead
foil facing the xray tube.

x. Blurring

Motion
blurring
Head rest
Short
exposure
time

Image
receptor
blurring
Slow speed
films

Finer grain
size
Close
contact
between
film and
screen

Geometric
blurring

Double
Parallax exposure
Wet film
viewing
avoided
Intensifying
screens

xi. Partial images

• Top of the film
not immersed in
the developing
solution
• Misalignment of
the x-ray tube
head (Cone cut).

x. Emulsion peel

• Abrasion of the film
during processing.
• Excessive time in
wash water.
• Improper handling of
the film.

xi. Typical positioning faults
Incorrect positioning of the x-ray tube Incorrect placement of the film packet
head
Foreshortening

Reverse placement

Elongation

Double exposure

Overlapping
Cone cut

Overlapping crown regions due to faulty
horizontal angulation of the tube head.

Double exposure of
the same film.

• Extraoral radiograph are examination made of the head
and facial region using films located outside the mouth.
• They are taken when large areas of the skull or jaw
must be examined or when patients are unable to open
their mouths for film placement and areas not fully
covered by IOPA.
• Images are not as defined or sharp as intraoral films.

Extraoral radiographs can be used alone or in conjunction
with intra oral radiographs.
Except for the panoramic radiographs, extraoral
radiographs are not frequently used by General
practitioners.
Major users are orthodontistic, prosthodontic and oral
surgeries

Purpose and use of
extraoral radiographs
Examine large areas
of the jaws and
Skull.
Evaluate TMJ
Disorders.

Detect and
evaluate impacted
teeth.

Detect pathological
lesions and
Diseases of the
jaws.

Cervical spine for
diseases

Detect fractures
and evaluate
trauma

Study growth and
development of
bone and teeth

TECHNIQUE
Many film positions and techniques require
…..special equipment's and
…a sound knowledge of the anatomical
structures through which the radiation beam is
directed.
…produced with conventional dental x-ray machines,
certain models
of panoramic machines or higher capacity medical
x-ray units.
Cassette, Films,
Intensifying Screens .
grids

Image receptor
• Cephalometric and skull views - 20x25cm
(8x10 inch) image receptor.
• Lateral oblique projections of the mandible 13x18cm (5x7 inch) image receptor.
• Panoramic views - 12.7x30.5cm (5x12 inch)
or 15x30cm (6x12 inch)image receptor.

 It is critical to correctly and clearly label the right and left
sides of the image.
 It is done by placing a metal marker of R or L on the outside
of the cassette in a corner in which the marker does not
obstruct diagnostic information.
 The proper exposure parameters depend
10
on the patient‟s size, anatomy and
65
mA
head orientation,image receptor
Kvp
speeds,x-ray source to receptor
3 to
distance and the use of grids.
4 sec

The main anatomical
landmark used in
patient positioning is
the
CANTHOMEATAL
LINE.

The canthomeatal
line forms
approximately a 10degree angle with the
FRANKFORT
PLANE.

Lateral cephalometric
projection of the
sagittal or median
plane.

Submentovertex
projection of the
transverse or
horizontal plane.

Water‟s of the coronal
or frontal plane.

Posteroanterior
cephalometric
projection of the
coronal or frontal
plane.

Reverse-Towne
projection of the
coronal or frontal
plane.

Lateral oblique
projection of the
mandibular body and
ramus.

Temperomandibular
joint projections

Newman and
Friedman Technique

Orthopantomography

Cephalometric Radiographs

Cephalometric means measurements of the head.
Either conventional x-ray machines modified for
Cephalometric work or special units are needed

Frontal (Posteroanterior)
Lateral skull projections.

LATERAL SKULL PROJECTION
(LATERAL CEPHALOMETRIC
PROJECTION)

It shows the entire skull
from the side

•Measure and compare changes
in Growth and development of
bone and the teeth through pre &
progress and post treatment
records.
Facial soft tissue profile of the
face

1. The contour of the lips
and the face.
2. The relation ship of the
teeth before removal, this
will helps to construct
prosthetic appliances that
look natural.

•Evaluate trauma.

•To determine the location
and extent of fractures.
•Malignancies.
•injuries to TMJ

LATERAL SKULL PROJECTION
(LATERAL CEPHALOMETRIC PROJECTION)

Image receptor and patient placement
A wedge filter at
the tube head is
positioned over the
The image receptor The site of interest
The patient is
anterior aspect of
is positioned
is placed towards
placed with the left the beam to absorb
parallel to the
the image receptors
side towards the
some of the
patient‟s
to minimize
radiation and to
image receptor
midsagittal plane
distortion
allow visualization
of soft tissues of the
face.

Position of the central x-ray beam
The central beam is perpendicular to the midsagittal plane of the patient and
the plane of the image receptor and is central over the external auditory
meatus

Cephalostats have ear rods that stabilizes the patient‟s head
parallel to the film and at right angle to the direction of the
beam
The Cephalometer allows the exposure to be taken several
times for the same patient in the same head position

Cephalostat

Film
X-ray
source
5 feet
• For cephalometric applications the distance should be 152.4 cm
(60 inches) between the x-ray source and the midcoronal plane.
• This increased distance provides an resultant image with
a broader gray scale of the patient.

Resultant image
Exact
superimposition of
right and left sides is
impossible because

Bilateral structures close to the

structures on the

midsagittal plane demonstrate less

side near the image

discrepancy in size compared with

receptor are

bilateral structures farther away from

magnified less than

the midsagittal plane.

the same structure

on the side far from
the image receptor.

Structures close to the
midsagittal plane (e.g.,
the clinoid processes
and inferior
turbinate's) should be
nearly superimposed.

Posteroanterior (PA)
cephalometric projection
Shows the entire skull in a Posteroanterior plane.

The beam passes through the skull in a posterior to anterior direction.

USES

• Asymmetry
• Trauma
• Developmental
abnormalities
• Fractures of skull
vault
• Investigation of
frontal sinus
• Conditions affecting
cranium( Paget's
disease, multiple
myeloma,
hyperparathyroidism.
)
• Intracranial
calcification

• The image receptor is placed in front of the
patient, perpendicular to the midsagittal plane
and parallel to the coronal plane.

• The patient is positioned so that the
canthomeatal line forms a 10-degree angle with
the horizontal plane and the frankfort plane is
perpendicular to the image receptor.

The central beam is perpendicular to the image
receptor, directed from the posterior to the anterior
(hence the name postero-anterior) parallel to patient‟s
midsagittal plane and is centred at the level of the
bridge of the nose

The midsagittal plane should
divide the skull into two
symmetric halves.

The superior border of the
petrous ridge should lie in
the lower third of the orbit.

Resultant image

Water‟s view projection
Also known as sinus projection.
It‟s similar to the postero-anterior projection except
that the center of interest is focused on the middle
third of the face.
To Evaluate the
maxillary,
frontal and
ethmoid
sinuses..

Detecting the
lefort‟s fractures,
zygomaticcomplex, nasoethmoidal
fractures, orbital
blow out
fractures.

technique
The image receptor is
placed in front of the
patient and
perpendicular to the
midsagittal plane..

The patient‟s head is
tilted upwards so that the
canthomeatal line forms
a 37-degree angle with
the image receptor.

The central beam is
perpendicular to the image
receptor and centered in the
area of the maxillary sinuses.

If the patient‟s mouth is
open, the sphenoid sinus
will be seen
superimposed over the
palate.

The midsagittal plane
should divide the
skull image in to
two symmetrical halves.

The petrous ridge
of the temporal bone
should be projected
below the floor of
the maxillary sinus

Resultant image

Reverse –towne (open mouth) projection
Purpose:

To examine fractures of the condylar neck of
the mandible.
Intracapsular fractures of the TMJ.

Condylar hyperplasia or hypoplasia.

technique
The image receptor is placed
in front of the patient,
midsagittal and parallel to
the coronal plane.

The patient‟s head is tilted
downward so that the
canthomeatal line forms a 25
to 30-degree angle with the
image receptor.

The central beam is
perpendicular to the image
receptor and parallel to
patient‟s midsagittal plane and
it is centered at the level of the
condyles.

To improve the visualization
of the condyles, the patient‟s
mouth is opened so that the
condylar heads are located
inferior to the articular
eminence.

The midsagittal plane (imaginary line extending from the
middle of the foramen magnum and the posterior arch of the
atlas through the middle of the bridge of the nose and the nasal
septum) should divide the skull image into two symmetric
halves.

The petrous ridge of the temporal bone
should be superimposed at the inferior part of
the occipital bone and the condylar heads
should be projected inferior to the
articular eminence.

Resultant image

Submentovertex (base) projection
Purpose: Used to show

the base of
the skull.

The position
and
orientation
of the
condyles
Sphenoid
sinus

Fractures of
the
Zygomatic
arch.

technique
The image receptor is
positioned parallel to patient‟s
transverse plane and
midsagittal and coronal plane.

To achieve this, the patient‟s
neck is extended as far
backward as possible with the
canthomeatal line forming a
10-degree angle with the
image receptor.

The central beam is perpendicular to
the image receptor, directed from
below the mandible towards the
vertex of the skull (hence the name)
and centred about 2cm anterior to a
line connecting the right and left
condyles.

The midsagittal plane should
divide the skull image into
two symmetrical halves.
The buccal and lingual cortical
plates of the mandible should
be projected as
uniform opaque lines.

An underexposed view is required
for the evaluation of the zygomatic
arches because they will be over
exposed or “burned out” on radiography
obtained with normal exposure factors.

Resultant image

Lateral jaw (lateral oblique) projection
It has been largely replacead by panoramic
radiographs but still taken when image details
is needed.
Two types

Mandibular
body
projection.

Mandibular
ramus
projection

To Examine the
posterior region
of the mandible.

Patients who
have fractures
or swelling.

Valuable in
children, or
Senile patients
who can’t
withstand
intraoral films.

It evaluate the
condition of the
bone and to
locate impacted
teeth or large
lesions.

Mandibular body projection –
Film placement and head position
Cassette is positioned
flat against the cheek
and centered in the
molarpremolar area.

The lower border of the
cassette is parallel and at
least 2 cm below the
inferior border of the
mandible

Head position is tilted
about 10 to 20 degree
toward the side to be
examined and the chin is
protruded.

The central ray is directed toward the
molar-premolar region of the mandible
from a point 2cm below the angle of
the opposite side of the mandible

A clear image of the teeth,
the alveolar ridge and the
body of the mandible should be obtained.

If significant distortion is
present, the head was tilted
excessively.

If the contra-lateral side of the
mandible is superimposed over
the area of interest,
the head was not tilted sufficiently.

Resultant image

Mandibular ramus projection
Image receptor is placed
over the ramus and far
enough posteriorly to
include the condyle.

The central beam is
directed the center of the
imaged ramus, from 2cm
below the inferior border
of the opposite side of the
mandible at the area of the
first molar.

The lower border of the
cassette is parallel and at
least 2cm below the
inferior border of the
mandible.

The head is tilted toward the side
being examined so that the condyle
of the area of interest and the
contra-lateral angle of the mandible
form a horizontal line. The
mandible is protruded.

Resultant image
•A clear image of the third molar-retro molar
area, angle of the mandible, ramus and
condylar head should be obtained.
•If significant distortion – head was tilted
excessively
•If contralateral side of the mandible is
superimposed over the area of interest – head
was not tilted sufficiently

Trans cranial
• It provides a sagittal view of the lateral aspects of condyle and
temporal component.
Used for
Identifying gross
osseous changes
on the lateral
aspect of the joint

Range of
motion

Displaced
condylar
fractures

Trans pharyngeal ( Parma) projection
• It provides a sagittal view of the medial pole of the condyle.
• Used for visualizing erosive changes
of the condyle

-5 degree
though the
sigmoid
notch of the
opposite side

Trans orbital
It is similar to trans maxillary projection in that both
provide an anterior view of the TMJ, perpendicular to
trans cranial and trans pharyngeal.
Uses:
To detect condylar neck fractures

Evaluation of the image
• Extra oral images should
first be evaluated for
overall quality
• Interpreting poor quality
images can lead to
diagnostic errors and
subsequent treatment
errors.

A thorough knowledge of normal
radiographic anatomy and the
appearance of normal variants is
critical for the identification of
pathology

Abnormalities cause disruption of
normal anatomy

Detecting the altered anatomy
precedes classifying the type of
change and developing a DD

Extra-oral Near Parallel Technique
This technique is an alternative to the bisecting angle
technique, for the maxillary molars.
It is of particular use in cats, where the zygomatic arch
superimposes over standard intra-oral bisecting angle
views.

The patient is in lateral recumbency
The long axis of the target teeth is as near parallel to the film as
possible and the beam is angled at approximately 70 degrees to
the film and the target.
The mouth is opened, with a prop, to direct the beam onto the
film without superimposing the maxillary teeth on the mandibular
teeth

Accuracy is dependent on the ability to
keep teeth as near parallel to film as possible and
to prevent superimposing the maxillary teeth on the
mandibular teeth.

Orthopantomography
iIt is a technique for producing
single tomographic image of
facial structures that includes
both maxillary and mandibular
dental arches & their supporting
structures.
•

Ortho – correct/straight

•

Panorama-“an unobstructed
view of a region in every
direction”

•

Tomography- “X-ray technique
of making radiographs of layer
of tissue depth, without
interference of tissues above
and below it.”

Historical
milestones for
digital
panoramic
systems :

1985-1991-The first dental
digital panoramic systems
were designed by McDavid
et al.

1995-DXIS, the first dental
digital panoramic x-rays
system available in the
market, was introduced by
Signet of France.

Digipan of trophy radiology
(France) offered a digital
option for the OP 100
panoramic made by
instrumentarium (Finland).

1997-SIDEXIS, of siemens
(currently sirona dental
systems, germany) offered a
digital option for ortophos
plus panoramic unit.

1998-2004- Many panoramic
manufacturers offered their
own digital systems.

2006- SCAN300FP, of „Ajat‟
(Finland) is the latest
innovation offered

Patero working independently,
Numata were the first to describe the
principles of panoramic radiography.

Dr.PAATERO 1934

Dr. NUMATA 1934

Father of Panoramic
Radiography

To interpret OPG competently one must have
a thorough understanding of the following :
1.

Principles of Panoramic image formation.

2.
3.
4.

Techniques for Patient positioning with head alignment
and their rationale.
Radiographic appearance of normal anatomic structures.

Principles of Panoramic image
formation

tube head angled
upward

film

rotation center

ROTATION CENTER
is the pivotal point, or
Split image

axis, around which
the cassette carrier
and x-ray tube head

Moving center
rotation – Ellipso
pantomography

Single-center
rotation

rotate.

* Depending on the

ROTATION CENTER

manufacturer, the
number and location

of the rotational
center differ:

Triple-center
rotation

Double-center
rotation

Parts of the machine
X-ray tube head
Cassette and
carriage assembly

Patient positioning
device

Exposure control

Scanora
multimodality
Panoramic machine.

Orthopantomogra
phy op 100
panoramic
machine.

ProMax (PLANMECA)
Panoramic machine.

Focal Trough, focal corridor
Three-dimensional curved zone or image layer in which
structures are reasonably well defined

Depends upon :
1. Arch path
2. velocity of
receptor and
Tube head
3. Cassette size

The occlusal plane is aligned so
that it is lower anteriorly, angled 20
to 30 degrees below the horizontal
plane.

Dentoalveolar region

Maxillary region

Mandibular region

The four
Diagnosti
c regions
in OPG

TMJ including retro
maxillary
and cervical region

149

Dentoalveolar
region

• Shape and angulation of roots.
• Alveolar bone and periodontium
• Shows gentle curve of occlusal plane
152

Broad coverage of the
facial bones and teeth.

Ability to be used in
patients unable to open
their mouths.

Low patient radiation dose.

Convenience of the
examination for the
patient.

Patient's readily
understand of panoramic
films, making them a
useful visual aid in patient
education and case
presentation.

Short time required - 3 to 4
minutes

Easy to store, compared to
the large set of intra oral xrays which are typically
used

Principle advantages of
panoramic Images:

D
I
S
A
D
V
A
N
T
A
G
E
S

Magnification,
Geometric distortion
and overlapped
images.

Resolution of fine
anatomic details of
peri-apical area and
periodontal structures
is less.

Poor image is
obtained when sharp
inclination of anterior
teeth towards labial
or lingual side.

The spinal cord
superimpose on
anterior region.

Common to have
overlapped teeth
images, particularly in
premolar area.

Artefacts are common
and may easily be
misinterpreted.

Expensive

•

First examination of new patients (patients with multiple deep carious
lesions, with orthodontic and periodontal problems)

U
S
E
S

•

Early diagnosis of dental anomalies (recommended especially at ages of
10, 15 and 20 years), to check dentition and to provide a timely diagnosis
of the odontogenic tumors or cysts

•

Establishing the exact cause of missing teeth

•

Radiographic examination of the teeth with endodontic treatment

•

Odontogenic sinus disease suspicion

•

Disorders of TMJ caused by malocclusion (in such cases, the
Orthopantomogram should be performed with the patient in habitual
occlusion)

•

Facial and maxillary asymmetry

•

Painful or asymptomatic swelling

• Multiple dental extractions, with suspected osteomyelitis
• Examination of non-odontogenic cysts, tumors and tumor-like lesions of
bone tumors
• Suspicion of invasive bone tumors or bone metastases
• Neural tumors
• Unusual sensitivity of teeth, unusual eruption, spacing or migration of

teeth
• Radiographic examination of the oromaxillo-facial area in systemic
diseases and syndromes

• Maxillo-facial fractures and suspected post-traumatic fractures
• Before and after surgery in the oromaxillo-facial surgery.

Ghost image:- A ghost image looks like the real

object except that it appears on the opposite side of
the film.

Shadow of vertebral column, usually from
patient not standing straight

Anterior teeth narrower and blurred

Teeth too posterior

Anterior teeth wider and blurred

Structures smaller on the side to which head is
turned; larger on opposite side.

HEAD TIPPED DOWN

Mandibular incisors shortened, V-shaped mandible

HEAD TIPPED UP

Squared-off mandible, palate superimposed over maxillary teeth

REVERSE OPG:
Reverse panoramic radiography is a radiographic technique to view the
lateral aspect of the condylar head and its neighboring structures more
clearly and with less distortion.

The technique is simple to perform with the patient in the reverse position
in an Orthopantomogram

The chin rest was removed so that the patient can be positioned posteriorly
such that the condylar region is moved closer to the lateral centre of
rotation within a fixed distance between the X ray source and the cassette.

Advances in radiogrpahic
techniques

Digital Radiogrpahy
•Sustantial amount of bone loss is required in
conventional radiograph to be detected in
radiograph.
•Enables use of computerized images, can be
stored, manipulated and corrected.
•Image is constructed using pixels
•These pixels are arranged in grids and rows on
the sensor

Image acquisition
Two systems are there
Direct
Indirect

Direct digiital radiogrpahy
•Uses (CCD) sensor linked with a fiber optic to the computer system
•Real time imaging radiography
Disadvantages
•Limited sensor area depics one or two teeth
•Sensor rigidity

Direct Digital radiography
• nondestructive test (NDT)
• image is produced electronically, rather than on film,
• very little lag time occurs between the item being exposed to
radiation and the resulting image.
• the electronic image that is viewed results from the radiation
passing through the object being inspected and interacting
with a screen of material that fluoresces or gives off light
when the interaction occurs.
• Fluorescent elements of the screen form the image much as
the grains of silver form the image in film radiography.

Indirect Digital radiography
•Commercial digora system
•Uses phosphor luminescence flexible
film like radiation sensor placed
•Intraorally and exposed to x ray tubes
•A laser scanner reads exposed plates
offline and reveals digital image data.

Advantages
•Dose reduction
•Image manipulation
•Measurements
•3-D reconstruction can be done
•Storage
•Environmental friendly
•contrast, density
• magnification of area of interest

• edge enhancement
Disadvantages
• color rendering
•Expensive
•Sensor cannot be sterlized, barriers can be used
but if contamined they have to be discared
•Medicolegal purposes- images can be manipulated,
there are concerns about their use

• The image formed is a "positive image" since brighter areas on
the image indicate where higher levels of transmitted radiation
reached the screen.
• This image is the opposite of the negative image produced in
film radiography.
• The lighter, brighter areas represent thinner sections or less
dense sections of the test object.

Radio-visography
• X rays takes using sensor that transmit images directly
onto computer monitor
• Helps patient understand the doctors explanation more
easily
• Enables the doctor to zoom in on a digitizes specific area
of tooth
• digitizes ionizing radiation
• Provides an instantaneous image on video monitor
• Reduces exposure by 90%
• Equipment has fiber optic intra oral sensor (with
selenium coated plate)

Radio-visiography
Parts
• The radio- hypersenitve intra oral sensor and
conventional X-ray unit.
• The visio-> video moniter and display processing u
• The graphy>high resolution video printer that instantly
provides a hard copy of screen images using same video
signal.

•
•
•
•
•

Advantages
Elimination of xray film
Significant reduction in exposure time
Instantaneous image display
RVG System appears to be promising
for the future of dentistry.

Disadvantages
•Resolution is slightly lower than convenional
films
•Exposure above .15s at 75Kp reults in pixels
saturation that results in shortening in saturation
of the length of the intrument

Digital Substraction
Radiography
• Image enhancement method
• Area under focus being clearly displayed
against a neutral gray black background
or it is superimposed on the radiographic
itself.
• Relies on conversion of serial radiogrpahs
into digital images
• Quantitative changes can be
accompalished by eans of a computer
(Computer Assisted Substraction
Radiography

• Advantages
• reduced radiation up to 80%
• faster imaging without X-ray film and developing images
• digital intraoral sensor is used instead of X-ray film
• immediate imaging on the computer screen
• high quality of the digital image that can be analyzed and
processed
• saving images in the patient's file
• children friendly for reduced radiation, if imaging is necessary
• Evaluation of success of treatment
• Changes in alveolar bone levels
• Progress of an incipient carious lesion to DEJ
Disadvantages or expansion of periapical lesion after RCT
• Assessing healing

•Need to be close to identical porjection alignment
during the exposure of sequential radiographs
•Makes this method very impractical in a clinical
setting.

• Recently , new image substraction
methods DIAGNOSTIC SUBSTRACTION
RADIOGRAPHY (DSR) have been
introduced combining use of a
positioning device during film exposure
with a specialized software.

Computed Tomography
• powerful nondestructive evaluation (NDE) technique for
producing 2-D and 3-D cross-sectional images of an object
from flat X-ray images.
• Characteristics of the internal structure of an object such as
dimensions, shape, internal defects, and density are readily
available from CT images.

• The test component is placed on a turntable stage that is
between a radiation source and an imaging system.
• The turntable and the imaging system are connected to a
computer
• 2-dimensional shadowgraph image of the specimen just like a
film radiograph.
• Specialized computer software produces cross-sectional
images of the test component as if it was being sliced.

Indications
• Investigation of intracranial disease including tumours,
haemorrhage & infarcts.
• Suspected intra cranial, spinal cord damage.
• Fractures-In the orbit, naso- ethmoid complex.
- Cranial base.
-Odontoid peg
- Cervical spine
• Cyst-Site, size & extent.
• Disease within para nasal air sinuses.• Tumor staging- site, size, extent of affecting different regions.
• Tumour and tumour like discreet swellings both intrinsic and
extrinsic to salivary glands.
• Investigation of osteomyelitis.
• Investigation of TMJ.
• Preoperative assessment of maxillary and mandibular alveolar
bone height.

Advantages
 Very small amounts and
differences in x-ray thus
detailed imaging of intra
cranial lesions, imaging of hard
and soft tissues both hard and
soft tissues.
 Axial tomographic sections are
obtainable.
 Reconstructed images can be
obtained from information
obtained I the axial plane.
 Images an be enhanced by the
use of IV contrast media to
delineate blood vessels.

Disadvantages
• Equipment is very expensive.
• Very thin contiguous or
overlapping slices result in
very high dose investigation.
• Metallic objects produce
marked streak or artifacts.
• Inherent risks associated with
IV contrast agents.

CONE BEAM CT
•Also known as digital volume tomography/(CBCT) are a
variation of traditional CTsystems.
•used by dental professionals
•rotate around the patient, capturing data using a coneshaped X-ray beam.
•reconstruct a three-dimensional (3D) image of the
following regions of the patient‟s anatomy: dental (teeth);
oral and maxillofacial region (mouth, jaw, and neck); and
ears, nose, and throat.
•One an is 20-40secs, and in one scan image I cylindrical in
volume described as field of view.
•Field of view of 15cm diameter is used for scanning
maxillofacial skeleton

.
When compared with ortho pantamogram
CT

CBCT

200-300 conventional
radiographs.

2-8 conventional
panoramic radiographs

3D accuitomo images a small cylinder of information
thus enabling high resolution images of specific teeth to
be obtained.
Voxel size is 0.125mm x 0.125 mm x 0.125mm.
Dose of this very low when compared to 3-4 peri apical
radiographs.

Indications
• Investigation of all conditions affecting the mandible or
maxilla including cysts, tumours, giant cells and osseous
dysplasia.
• Cleft palate assesment
• Investigation of maxillary antra
• Investigation of TMJ.
• Implant assessment .
• Orthodontic assessment.
• Localisation of unerupted tooth/ odontomes.
• Assessment of lower 3rd molars .
• Investigation of fractures of mandible or middle 1/3rd of
facial skeleton.
• For multi planar imaging of a single tooth in terms of peri
apical & periodontal tissue with high resolution scanners.

Advantage

Disadvantage

• Multi planar imaging
•
and manipulation.
•
• Low radiation dose
• Very fast scanning time.
• Inexpensive and
affordable.
• Used mainly for implant
and cephalometric
•
planning

Soft tissue detailing is not
possible.
Computer derived
panoramic image I not
comparable with
conventional panoramic
radiographs- particular are
is needed for
interpretation.
Metallic fillings/objects
produce streaks and star
artefacts like CT.

J of canadian dental association 2006

MRI
Principle
Radio frequency signal emitted by excited hydrogen atoms in the body
(present in any tissue containing water molecules) using energy from
an oscillating magnetic field applied at the
appropriate resonant frequency.
The orientation of the image is controlled by varying the main magnetic
field using gradient coils.
coils are rapidly switched on and off they create the characteristic
repetitive noises of an MRI scan.
The contrast between different tissues is determined by rate at which
excited atoms return to the equilibrium state,
Exogenous contrast agents may be given intravenously, orally or
intrarticulary.[
Current science , VOL 67 , No 12, 25 dec 1994

Indications
• three-dimensional hard- and soft-tissue imaging of teeth
without the use of ionizing radiation.
• potential to image minute dental structures within clinically
relevant scanning times.
• Endodontists-potential method to longitudinally evaluate
teeth where pulp and root structures have been
regenerated.
• Distinguish between various soft tissues and localisation of
soft tissue lesions.
• Stray field microscope- modification of MRI – can detect
canals in tooh for endodontic purposes
• Differentiate aglossia from hypoglossia
• TMJ displacements and related problems
J.endod 2011 Jun;37(6):745-52.

contraindications
• Ferromagnestic substance s like
pacemaker,shrpnels,etc could be disloged
causing complications.
• Chromic alloy arch wires, stainless steel crowns.
Banda and bonded metals cause artifacts

Ultra sound

• Non-invasive investigation which use a very
high frequency (7.5-20MHz) pulsed
ultrasound beam rather than ionizing
radiation.
• Produces high resolution images of more
superficial structures.

Oral surg oral med oral pathol oral radiol 203 june

Which is picked up
by the transducer
and converted into
electrical signal then
into real time black ,
white and grey
images

Ultrasound travels
to the skin

Some waves are
reflected back by
tissues to produce
echoes.

• sectional image which represents topographical map of
depth of tissue interfaces.
• thickness is determined by width of ultra sound beam
thus different density in the black /white echo picture is
described as hypo echoic(dark) or hyper echoic(light).
• A change in the frequency of sound reflected from a
moving source allows the detection of arterial and
venous blood flow - Doppler effect.

Oral surg oral med oral pathol oral raiol 203 june

1.
2.
3.
4.
5.
6.
7.
8.
9.

10.
11.
12.
13.
14.

Indications :-

caries detection,
dental fractures
soft tissue and periapical lesions
maxillofacial fractures
periodontal bony defects
gingival and muscle thickness
Temporomandibular disorders
Implant dentistry.
Evaluation of the swellings of the neck ,those involving
thyroid, cervical lymph nodes, major salivary glands thus to
detect solid and cystic soft tissue masses.
Detection of salivary gland and duct calculi.
Determination of vascularity and vascular structures.
Assessment of vascularity of carotids and carotid tumors.
Sialolithotripter –to break salivary calculi into 2mm
fragments thus avoiding major surgery.
Ultra sound guided FNA biopsy.

Advantage
• Non ionizing radiation.
•
• No known harmful effects
•
• Good differentiation
between soft and hard
•
tissues.
•
• Widely available and
relatively in expensive.

Disadvantage
Bone absorbs ultrasound
thus is not detected.
Real time imaging.
Technique sensitive
Difficult to interpret for
inexperienced operator.

Oral surg oral med oral pathol oral raiol 203 june

Contrast studies
Radiopaque
substances alter
the density of
different parts
of patient.

Thus certain
organs ,
structures,
tissues, invisible
by conventional
means be seen.

Alters the
subject contrast.

Different contrast studies
Sialography –Salivary
glands.

Arthrography
Angiography
Lymphography- Lymph
nodes and vessels
Urography
Barium meal, swallow
and enema-GI tract.

Computed tomographygeneral enhancement.

Indications
To show vascular anatomy and feeder vessels
associated with haemangiomas.
To show vascular anatomy of arterio venous
formation

Investigation of suspected sub-arachnoid
haemorrhage resulting from an aneurysm in the
circle of willis.
Investigation of transient ischaemic attacks due to
emboli from atheromatous plaques.

Complications
• Mild. Eg:-Headache, nausea, warmth/pain,
flushing, sneezing, constipation.
• Moderate. Eg :-Vomiting , bronchopasm,
urticaria and hypotension.
• Severe. Eg:-Cardiac arrhythmias, cardiac arrest,
convulsions, anaphylactic shock and pulmonary
edema.
• Fatal.

Patients at risk
1. Very young patients
2. Patients with a history of allergy to contrast
media
3. Diabetes, patients suffering from cardiac failure,
renal failure, severe pulmonary disorders
including asthma
Cause of complications
• Allergy
• Chemotoxicity
• Osmolality
• Anxiety

Hazards of dental x-rays in
oral cavity
• da Silva et al have demonstrated that panoramic
radiography increases the number of nuclear anomalies
(except micronuclei), with significant statistically
differences in exfoliated cells from the lateral border of
the tongue,
• were exposed to a repeat radiograph it induces a
genotoxic effect on epithelial gingival cells that increases
the frequency of chromosomal damage and nuclear
alterations indicative of apoptosis.
• The comparison of nuclear changes before and after
radiation exposure revealed a statistically higher number
of broken eggs, buds, karyorrhexis and binucleate cells
10 days after exposure.

D
. entomaxillofac Radiol. 2012 March; 41(3): 181–184

• X-ray increased other nuclear alterations closely related
to cytotoxicity, such as karyorrhexis, pyknosis and
karyolysis.
• Digital lateral radiography (cephalometric radiography)
obtained on a panoramic radiographic machine showed
similar results when compared with conventional
radiography in oral mucosa cells.
• Yoon et al18 revealed high expression levels of pChk2
and γ-H2AX in oral cells after radiation exposure.indicators of low-dose radiation exposure.

Dentomaxillofac Radiol. 2012 March; 41(3): 181–184

• When the effect of dental X-ray exposure in children was
investigated, no statistically significant differences were
found between micronucleated oral mucosa cells before
and after radiation exposure.
• radiation did lead to other nuclear alterations closely
related to cytotoxicity, including karyorrhexis, pyknosis
and karyolysis: there were significant statistically.
• CBCT in clinical practice evaluated DNA damage
(micronucleus) and cellular death (pyknosis, karyolysis
and karyorrhexis) in exfoliated buccal mucosa cells from
adults. The effective dose was 12 μSv.

Dentomaxillofac Radiol. 2012 March; 41(3): 181–184

RADIATION PROTECTION
• Radiation is energy in the form of
waves or moving subatomic particles.

TYPES OF RADIATION
• NON-IONIZING RADIATION

• IONIZING RADIATION

• capable for producing ions when
interact with matter.
PARTICULATE (alpha, beta,
neutrons)
 ELECTROMAGNETIC (X-Rays,
Gamma Rays)


PATIENT EXPOSURE &
DOSE
• Patient dose from dental radiography is
usually reported as the amount of
radiation received by a target organ.
• Most common measurements is skin or
surface exposure.
• Other target organs - Mean active
bone marrow, thyroid & gonads.

• The International Commission on Radiological
Protection (ICRP) devised a system of dose
limitation.

Based on following general principles:
• No practice shall be adopted unless its
introduction produces a positive net benefit.
• All exposures shall be kept as low as reasonably
achievable (ALARA), taking economic & social
factors in account.
• The dose equivalent to individuals shall not
exceed the limits recommended by the
commission.

What is ALARA
• ALARA is an acronym for As Low As reasonably
Achievable. This is a radiation safety principle for
minimizing radiation doses and releases of
radioactive materials by employing all reasonable
methods.
• regulatory requirement for all radiation safety
programs
• Current radiation safety philosophy is based on
the assumption that radiation dose and its
• biological effects on living tissues are modeled by
a relationship known as the “Linear Hypothesis

Mitigation of External Radiation Exposures
The three (3) major principles to assist with
maintaining doses ALARA are :
1) TIME – minimizing the time of exposure directly
reduces radiation dose.
2) DISTANCE – doubling the distance between your
body and the radiation source will divide the
radiation exposure by a factor of 4.
3) SHIELDING - using absorber materials such as
Plexiglas for beta particles and lead for X-rays and
gamma rays is an effective way to reduce radiation
exposures

Mitigation of Internal Radiation Exposures
1) Good hygiene techniques that prohibit the
consumption of food and drink in the lab and the
control of personal gestures that involve “hand-tomouth” contacts.
2) Frequent swipe surveys and lab area monitoring of work
areas, refrigerators, hoods, sinks, phones and computer
keyboards, etc.
3) Control contamination with absorbent paper and spill trays,
properly labeled waste containers, equipment, etc. and
prompt decontamination of any detected contamination.
4) Use fume hoods for materials which could become airborne
(e.g., vapors, dust, aerosols, etc.) and present an
inhalation hazard to workers.
5) Use proper protective equipment (PPE) such as
disposable gloves, safety glasses, lab coats, etc. to reduce the
possibility of ingestion or absorption of radioactive
materials

Maximum Annual Occupational Dose
Limits
Whole Body …………………… 5000 millirem
Extremities ……………………. 50000 millirem
Lens of the Eye ……………….. 15000 millirem
Fetus ……………………………… 500 millirem*
Individuals in the General Public …100 millirem
* 500 millirem for the fetus is during the
gestation period
The ALARA concept imposes lower operational dose
limits that are even more restrictive than the maximum
legal dose limits in the table above.
If a radiation worker’s dose for any calendar
quarter (3 months) or calendar year (12 month period)
exceeds these values, an investigation is conducted by the
RSO to determine if there are reasonable ways to reduce the dose
levels and discuss
with the worker methods for limiting the potential dose

ICRP divided the population into 3
groups:

•PATIENTS
•RADIATION WORKERS
•GENERAL PUBLIC

PATIENTS
• Examination directly associated with illness.
• Systemic examinations (periodic health
checks)
• Examination for occupational, medico-legal
insurance purposes.
• Medical research.

RADIATION WORKERS
• Exposed to radiation during the course
of their work.
• Divided into 2 subgroups depending on
the level of occupational exposure:
 CLASSIFIED WORKERS
 NON-CLASSIFIED WORKERS

CLASSIFIED WORKERS
• Receive high levels of radiation
exposure to radiation at work (nuclear
power industry)
• Require compulsory personal
monitoring.
• Require compulsory annual health
checks.

NON-CLASSIFIED
WORKERS
• Receive low levels of exposure to
radiation at work.
• The annual dose limits are 3/10 of the
classified worker’s limit.
• Personal monitoring is not compulsory.
• Annual health checks are not required.

GENERAL PUBLIC
• Originally set annual dose limits - 5
mSv.
• Current recommendation - 1 mSv.

•
•
•
•

SOURCES OF RADIATION IN
DENTAL RADIOLOGY

PRIMARY BEAM
SECONDARY RADIATION
STRAY RADIATION
SCATTERED RADIATION

CONDUCT OF
EXAMINATION
•
•
•
•
•

CHOICE OF EQUIPMENT
CHOICE OF TECHNIQUE
OPERATION OF THE EQUIPMENT
PROCESSING OF THE RADIOGRAPH
INTERPRETATION OF THE
RADIOGRAPH

CHOICE OF THE
EQUIPMENT
•
•
•
•
•
•
•

IMAGE RECEPTER
FOCAL SPOT TO FILM DISTANCE
COLLIMATION
FILTERATION
POSITION INDICATING DEVICE
FILM HOLDING DEVICE
LEADED APRONS AND COLLARS

INTRAORAL IMAGE
RECEPTOR
• In 1920, regular dental X-ray film – EASTMAN
KODAK COMPANY.
• Intraoral dental X-ray film – D & E speed.
• Speed of E-speed film – 2 times of D-speed film
& 50 times of regular dental X-ray film.
• E-speed film (Ektaspeed film, Eastman Kodak
Company) - 1981.

• Patient dose reductions :
– 60% compared with E-speed film.
– 77% compared with D-speed film.
• Digital Imaging – 50 to 95% reduction
in patient exposure.

FILMS/INTENSIFYING
SCREENS
• Calcium tungstate – emits blue light.
• Rare earth elements Gadolinium &
Lanthanum – emits green light.
• Rare earth screens -

– 8 times more sensitive to X-rays.
– 55% reduction in patient exposure.

FOCAL SPOT TO FILM DISTANCE
• 2 standard FSFDs:
– 8 inches (20 cm)
– 16 inches (41 cm)
• Federation Regulation – Minimum X-ray
source-skin distance:
– 7 inches (18 cm) X-ray tube operating
above 50 kVp.
– 4 inches (10 cm) X-ray tube operating
below 50 kVp.

• COMPARISION OF 16 INCHES AND 8
INCHES FOCAL SPOT:
– 38% decrease in thyroid dose with 90
kVp X-rays.
– 45% decrease in thyroid dose with 70
kVp X-rays.
• Longer FSFD – 32% reduction in exposed
tissue volume.

COLLIMATION
• Helps to control the size & shape of X-ray
beam.
• Recommended beam size – 23/4 inches.

• Decreases radiation exposure.
• Minimizes scattered radiation
Decreases fogging of film
Sharper image & better contrast

• Collimation is done with lead diaphragm
within the tube head or at the end of leadlined cylinder.
• 2 types : Round & Rectangular.

DENSPLY/RINN RECTANGULAR
COLLIMATOR

• Round collimator – 3
times the area
necessary to expose
the film.
• Rectangular
collimator reduces
patient dose approx
55%.

FILTERATION
• Filteration removes
the low energy X-ray
photons selectively
from the X-ray
beam.
• Filteration is stated
in mm of Al.

TYPES OF FILTERATION
• INHERENT FILTERATION – 0.5 to 1.0 mm
of Al.
• ADDED FILTERATION – 0.5 mm of Al.
• TOTAL FILTERATION – Inherent +
Added filteration

• X-ray beam filtered with 3 mm of Al –
surface exposure reduces by 20%.

• Al + rare earth materials like Samariun,
Erbium, Yttrium, Niobium, Gadolinium, etc
• Selective filteration of low & high energy
photons ( X-ray energies most effective in
producing image: 35 keV to 55 keV)
• Reduces patient exposure by 20% to 80%

POSITION INDICATING
DEVICE (PID)
•
•
•
•

PID - an extension of X-ray tubehead.
Direct the X-ray tube.
Minimize the volume of tissue irradiated.
3 basic types :
– Conical
– Rectangular
– Round

POSITION INDICATING DEVICE (PID)

• PIDs are commonly
available in 3 lengths :
– 8 inches
– 12 inches
– 16 inches
• Long PID is preferred.

FILM HOLDING DEVICE
• Helps to stabilize the film position in the
mouth.

OFFER PROTECTION TO THE PATIENT :
• Reduces frequency of retakes.
• External guide to indicate the film position.
• Possibility of misalignment of the X-ray
tube.
• Collimate the beam to the size of film being
used.
• Reduction in the exposure to patient’s
fingers.

PROTECTIVE BARRIERS
• LEAD APRONS
• THYROID COLLARS

LEAD APRONS
• A flexible shield of lead placed over the
patient chest & lap.
• To protect reproductive organs & bone
marrow.
• Recommended for all intraoral & extraoral
radiography.
• Protective equivalent – 1/4 mm of Pb.

• Attenuate 98% of scatter radiation to the
gonads.
• LEADED TORSO (BODY) aprons

THYROID COLLAR
• Flexible lead shield placed securly around
the patient’s neck.

• Protect thyroid gland.
• Recommended for intraoral radiographs.
• Reduce the thyroid gland exposure by 92%.

CHOICE OF INTRAORAL
TECHNIQUE
• Bisecting angle technique
• Paralleling long cone technique
• Rinn XCP instrument / Precision
instrument.

OPERATION OF THE
EQUIPMENT
• KILOVOLTAGE (kV)
• MILLIAMPERAGE (mA)
• TIME SETTINGS

KILOVOTAGE (kVp)
• X-ray machine : 70 – 90 kVp.
• Produce fewer low-energy X-rays.
• Gibbs etal (1988) reported that effective
dose reduces to 23% - increasing kVp from
70 to 90 kVp.
• Constant potential X-ray machine – reduces
patient exposure by 20%.

• Higher kVp – periodontal diagnosis.
• Low kVp – caries or soft tissue calcification.

MILLLIAMPERE-SCONDS
(mAs)
• X-ray machine : 8-10 mA.
• IMAGE DENSITY – milliamperage &
exposure time.
• Exposure time – most crucial factor
influencing diagnostic quality of radiographs.

TIMER
• Timer on the X-ray machine should be
electronic.
• “dead-end” control.
• Calibrated in 60th of sec.

PROCESSING OF THE
RADIOGRAPHS
• DARKROOM LIGHTING
• FULL DEVELOPMENT PROCESSING
• PROCESSING SOLUTIONS

DARKROOM LIGHTING
•
•
•
•

Kept free from light leaks.
Safelight filter – Kodak GBX-2 (red light)
15 watt bulb.
Safelight lamps – min of 4 ft from working
area.

FULL DEVELOPMENT
PROCESSING
• Time-temperature processing
• Radiation exposure may be decreased by
25%.
TEMPERATURE (in OF)
68
70
72

DEVELOPMENT TIME
(in min)
5
41/2
4

76
80

3
21/2

PROCESSING SOLUTIONS
•
•
•
•

Changed regularly
Stirred thoroughly twice each day
Kept covered to prevent oxidation
Not subjected to excessively high
temperatures.
• Weekly quality control checks.
• Chemicals should be replenished according
to manufacturer’s instructions.

INTERPRETATION OF
RADIOGRAPHS
• Viewed in a dimly lit room with a properly
functioning illuminator (view-box).
• Illuminator with variable intensity.

OPERATOR RADIATION
PROTECTION
3 basic methods to reduce occupational
exposure:
• POSITION
• DISTANCE
• SHIELDING

DISTANCE
RECOMMENDATIONS
• 6 feet away from X-ray tubehead during
exposure.
• When distance is not possible – Protective
lead barrier

POSITION
RECOMMENDATIONS
• 90o to 135o angle to the primary beam.
• Never hold a film in place for a patient
• Never hold or stabilize the tubehead
………during radiation exposure.

Dystrophic nail changes
carcinoma

Squamous cell

POSITION DISTANCE RULE
“The operator should stand at least 6 feet
away from the patient in a safe quadrant
at an angle of 90o to 135o to the central ray

of X-ray beam.”

ROLLING RADIATION
PROTECTION SHIELD

• Offers 0.5 mm lead
protection.
• Measures 24 X 231/2.
• Adjusts 36”-56” above
the floor.

PROTECTION OF THE
ENVIRONMENT
• Surrounding environment must be protected
from radiation to avoid the exposure of
persons in the environment.
• Primary beam should never be directed at any
one other than the patient.
• X-ray beam is aimed at the wall of the room
and not through door.

QUALITY ASSURANCE
“Any systemic action to ensure that a
dental office will produce consistently
high-quality images with minimal exposure
to patients & personnel.”

“Currently some state require dental offices
to establish written guidelines for quality
assurance & maintain written records of
quality assurance test.”

X ray unit
Dark room
maintenanc
e

Ancillary
instrument
maintenan
ce

Leakage
radiation

Quality
assurance

Timer
accuracy

Collimatio
n

Stability
of tube
housing

MONITORING DEVICES
AVAILABLE:

• ELECTRICAL

– Ionization chamber
– Thimble chamber
– Geiger counter

• CHEMICAL
– Film
– Chemical dosimeter

• LIGHT
– Scintillation counter
– Gerenkov counter

• THERMOLUMINESCENCE
– Thermoluminescent dosimeter

• HEAT
– Calorimeter

PERSONAL MONITORING
DEVICES
• POCKET DOSIMETER
• FILM BADGE
• THERMOLUMINESCENT DOSIMETER
(TLD)
• ELECTRONIC DOSIMETER

THERMOLUMINESCENCE
DOSIMETER (TLD)
• Most common personal
monitoring device.
• Used for measurements
of the actual dose
received by the
operator.

ELECTRONIC DOSIMETER
• 5 to 200 times more sensitive than TLD.
• With an audible alarm system.

Unique Considerations for
Radiation Exposure in Children in CT scans
• There are three unique considerations in children.
• Children are considerably more sensitive to radiation than adults,
as demonstrated in epidemiologic studies of exposed
populations.
• longer life expectancy than adults- larger window of opportunity
for expressing radiation damage.
• The risk for developing a radiation-related cancer can be several
times higher for a young child.
• The use of more than one scan further increase the radiation
dose.
• Majority of cases, a single scan should be sufficient during
pediatric CT.
University of Michigan Children hospital site

Radiation reduction
Perform only necessary CT examinations•

When appropriate, other modalities such as ultrasound MRI, which do
not use ionizing radiation, should be considered.

Adjust exposure parameters for pediatric CT based on

•

•

– Child size: guidelines based on individual size / weight parameters
should be used.
– Region scanned: the region of the body scanned should be
limited to the smallest necessary area.
– Organ systems scanned: lower mA and/or kVp settings should be
considered for skeletal, lung imaging, and some CT angiographic
and follow up examinations.
Scan resolution: the highest quality images are not always required to
make diagnoses. many cases, lower-resolution scans are diagnostic.
Providers should be familiar with the multiphase examinations. These
result in a considerable increase in dose and are rarely necessary,
especially in body (chest and abdomen) imaging.
University of Michigan Children hospital site

CONCLUSION
Although these
radiographic techniques are
essential in arriving at a
diagnosis, appropriate
usage of the right technique
in the right time to an apt
condition becomes vital to
the clinician in guiding to
arrive at a conclusion for
diagnosis and there by
treatment planning

“value of a
diagnostic
procedure
depends upon
the amount of
information
that can be
derived from
it”

References
 Principles and Interpretations of Oral Radiology, 5th Edition
By Stuart C.WHITE and MICHAEL J.Pharoah.
 Essentials of Dental Radiography, 3rd Edition by Haring .
 Text Book of dental and maxillofacial Radiology By Frenry
R. Karjodkar..
 Essentials of Dental radiology and radiology,3rd edition,
Eric whites
 Text book of Pedodontics (Mc Donald & Avery)
 Oral radiology- principles and interpretation; Paul W. Goaz,
Stuart C. White
 Web Page – Radiographic techniques for pediatric patients
(steven Schwartz) dentalcare.com
 Intra-Oral Radio Graphs for the Pediatric Dental Patient
Pedo- fourth molar web page

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