1 dental radiology

Warning
This publication is provided solely for the
immediate study needs of students enrolled at the
University of Al-Azhar, Cairo, A.R.E. for the
course directed by

Dr. Ossama El-Shall.
All rights reserved. No part of this publication may
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01/25/13 00:59 Ossama El-Shall

Dental Radiology
Dental Radiology
Dr. Ossama EL-Shall
Professor and Chairman of Oral
Medicine, Periodontology, Diagnosis and
Radiology Department.
Faculty of Dental Medicine for Girls
Al-Azhar University , Cairo Egypt.
01/25/13 00:59
E-mail address: oelshall@hotmail.com
Ossama El-Shall

Dental Radiology course for post
graduate students.
 Physics of Ionizing Radiation.
 X-ray Machine.
 Biological effects of Radiation.
 Safety &Protection in dentistry.
 Dental X ray Film composition, (intra & extra-oral), Types & uses of intra-oral
films.
 X-Ray film processing.
 Intra-oral radiographic techniques .
 Plain Extra-oral film projections .
 Panoramic Imaging.
 Faults affecting dental radiographs.
 Normal Anatomical Landmarks.
 Dental radiographic interpretation.
 Specialized techniques for imaging (Conventional tomography, CT, MRI,
Nuclear medicine, Ultrasonography, Sialography)
 Cone-Beam Computed Tomography

Contents of part I
1- Terminology.
2- Radiation Physics.
3- Properties of X-ray
4- Dental X-ray apparatus.
5- Production of X-rays.
6- Types of radiation.
7- Dental X-ray films, both intra-oral and
extra-oral.
8- X-ray film processing.
9- Intra-oral radiographic techniques.

Terminology
1- Radiology
2- Roentgenology
3- Dental radiology
4- Dental radiography
5- Radiograph
6- Radiation
7- Radiolucent
8- Radiopaque


Radiology

Science that deals with
diagnosis, therapeutic and
researches application of high-
energy radiation.


Roentgenology

Science that deals with application
of X-ray on any field.


Dental radiology

It is the branch of science that
deals with the use of radiation in
diagnosis of dental diseases.


Dental radiography

It is the art of producing an
image or picture for intra- or
extra-oral structures on a dental
film using X-ray.


Radiograph

It is the shadow features (image) received
on a radiation-sensitive film emulsion by
exposure to ionizing radiation directed through
an area or region or substance of interest,
followed by chemical processing of the film.
It is basically dependent on the differential
absorption of radiation directed through
heterogeneous media.


Radiation

It is the process of emission,
propagation and transmission of
energy by atoms in the form of
waves.


Radiolucent
Objects that permitting the passage of
radiant energy with relatively little attenuation
by absorption and appear black on the film, such
as silicate restoration, pulp tissues, gingiva, and
carious lesion.
Another definition; Objects partly or wholly
penetrable by roentgen rays; the image
of such a material on the film ranges from dark
gray to black.
RL

RL


Radiopaque

Objects that absorb X-rays and appear
white on radiograph, such as amalgam
restoration, enamel, and bone.
Another def.:Objects that not freely penetrable
by radiation.
OR Objects highly resistant to penetration by
roentgen rays; the image of such a material appears
on the film within range of gray to white.


Clinical Exam + Radiographs

Diagnosis

Treatment

Radiation physics


Radiation physics
Atomic structure:

1- Atom is the fundamental
unit of any particular
element, i.e. the basic unit
of an element.

2- It is composed of a
central nucleus and outer
orbits which spaced at a
definite distance from the
nucleus and are identified
by letters, K, L, M, N, O,
P, Q.

3-Electrons are negatively charged
particles that orbiting shells.

4-The central nucleus is composed of two
kinds of particles, proton, +ve charged
and neutrons with no charge.

5-Since neutrons have no charge; the
magnitude of the charge of the nucleus
will depend on the number of protons
(Atomic number), which are equal to the
number of electrons.

Atom states
Ground state (stable): It is the normal or ground state
of atom on which the atom is electrically neutral with
equal numbers of protons and electrons.

Excitation state: It occurs when sufficient energy
applied to the atom, results in removing of electron
from its normal shell to a higher energy shell.

Ionization state: It is the process by which an atom
loses its electrical neutrality and become ions by
either addition or removing of electrons. If electron
is added or removed from the atom, the atom will
termed as ion. If the electron is removed, the atom
becomes a +ve ion while the removed electron is
called –ve ion.

Atom (electrically stable)

K-shell
protons
L-shell
neutrons
M-shell
electrons

Atomic Number (Z) = # of protons

ELECTROSTATIC FORCE

Attraction between
protons and electrons


CENTRIFUGAL FORCE

Pulls electrons away
from nucleus


EF CF

Balance between electrostatic
force and centrifugal force keeps
electrons in orbit around nucleus


Nature of radiation

Radiation may be either

Corpuscular radiation

Electromagnetic radiation


A- Corpuscular or particulate radiation

1- It is that type of radiation given off from radium,
radioisotopes, and during splitting of the atom.

2- It is composed of solid subatomic particles having
mass and charge.

3- It travels in straight lines and is not used in
dental diagnostic filed but in therapeutic means.

4- Examples for corpuscular radiation:
Alpha (α) rays.
Beta (β) rays.

B- Electromagnetic radiation

1-It is that type of radiation formed of units
of pure energy, which are propagated in the
form of waves as a combination of electric
and magnetic fields.

2-It is made of pure energy propagate in a
form of waves with no mass or charge.

3-It is generated when the velocity of an
electrically charged particle is altered.

4-They travel in straight lines with the
same speed of light (3x108 meter/sec.)

5-As they propagate in a form of waves,
they have a wavelength (λ) and
frequency (ν(


λ

Wavelength (λ) is the distance between
2 crests or bottoms of 2 successive
waves.

Frequency (ν) is the number of cycles
or waves emitted/sec.

λ

λ

F
Wavelength x Frequency = Speed of wave


According to the wavelengths, radiations
can differ in their properties.

Radiation may be of

Short wavelength
Or
Long wave length


The short wavelength increased
frequency increase the energy
accompanied with it increase
the power of penetration the rays
will termed Hard radiation which
characterized with low power of
absorption into matter and low
ionization.


The long wavelength decreases
frequency decrease the energy
accompanied with it decrease
the power of penetration the
rays are termed Soft radiation which
characterized with high power of
absorption into matter and high
ionization effects.


A
Highest energy
B Shortest wavelength
Highest frequency
C
Highest energy?

Examples of electromagnetic radiation
arranged in an ascending order according to their
wavelength:
1-Cosmic rays.
2-Gamma Ray
3-X.Ray. wavelength = 0.1-1Ao, Ao = 10-10 m
4-Ultraviolet rays.
5-Visible light.
6-Infra-red.
7-Microwaves.
8-Radio, radar, T.V waves.


Electromagnetic Spectrum

radio tv visible x-rays gamma cosmic
light rays rays


History History History

X-ray
X-rays were first discovered in
1895 by Wilhelm Conrad Roentgen,
the professor of physics and
director of the physics institute at
the University of Wurzburg in
Bavaria.

Hence the term ROENTGEN
RAYS, often applied to mechanically
generated x-rays. He won a Noble
prize for his discovery of X-ray.

Roentgen called them X-rays
after the mathematical symbol X
for unknown.


X-ray of Bertha Roentgen's Hand

Roentgen soon found that
photographic plates were sensitive to the
newly discovered rays.
He convinced his wife to participate in
an experiment.
Roentgen placed her hand on a
cassette loaded with a photographic
plate. He then aimed the activated
cathode ray tube at her hand for fifteen
minutes.
When the image was developed, the
bones of her hand and the two rings she
wore were clearly visible.



Within 2 weeks after Roentgen
was made his discovery public, the
first dental radiograph was made
by German dentist Otto Walkoff,
who placed in his own mouth small
glass photographic plates wrapped
in rubber dam and exposed them
for 25 minutes.



Early x-ray machine. Arrow points to
“live” electrical wire.

Definition of X-ray
- It is a type of electromagnetic radiation
characterized by wavelengths between
approximately 1 A and 10-4 A.

- They are invisible, penetrative especially
at higher photon energies, and travel with
the same speed as visible light.

- They are usually produced by bombarding
a target of high atomic number with fast
electrons in a high vacuum

In brief: X rays are a form of pure
energy units belonging to electromagnetic
spectrum characterized by having a very
short wave length and have the ability of
producing shadiness’ or images of the
body tissues.


Properties of X-ray


Properties of X-ray

1- They have a very short wave
length: As the wavelength decrease,
the power of penetration of the x-ray
increased. The power of penetration
depends on several factors in addition
to the wavelength such as: Atomic
number of the object, thickness of the
object, and the density of the object.

2- They have a selective penetration,
absorption power: When the x-ray hit
an object, certain interactions occur,
these interactions may occur in either
of 3 forms or possibilities: a)
Penetrate the object, b) Absorbed by
the object, c) Deflected from certain
objects e.g. heavy metals


3- It affects photographic film’s
emulsion: X-rays upon falling on the
emulsion of a photographic film they
cause physical changes producing what
is termed Latent Image formation,
which cannot be seen except after
chemical application.


4- It causes certain substances to
fluoresce: X-ray can cause certain
fluorescing substances to fluoresce or
emit “violet blue visible light” which is
of a longer wave length than the x-
rays so this was used in dentistry in
the formation of intensifying screen.


5- They cause ionization of atoms: X-
rays have the power of converting
atoms into ions with the formation of
ion pairs which are electrically
charged, unbalanced, non-functioning
cells thus will have a harmful effect
later on the body cells and fluids.


6-They have biological damaging
effects: May be of somatic effects
such as skin burns, erythema or cancer
or genetic effects


7. Travel in straight lines in wave motion with
the same speed of light.3x108 meter/sec.

8. Short waves about 1/10000 of that of light.
(0.1-0.001nm)

9. Invisible, can’t be felt, smelled or heard.

10. Weightless, mass less, and changeless.


11. They cannot be focused or collected by a
lens.

12. They cannot be reflected by a mirror or
by fluids.

13. They cannot be deviated by a magnet.

14. They can deflect on heavy metals by
deviated into a new linear trajectory.


X-Ray Machine


Dental X-ray apparatus
How are X-rays created?

 When fast-moving electrons (minute particles each
consisting of a negative electrical charge) collide
with matter, X-radiation is produced.
 The most efficient means of generating X-rays is an
X-ray tube.
 In it, X-rays are produced by directing a high-
speed stream of electrons against a metal target.
 As they strike the atoms of the target, the
electrons are stopped.
 Most of their energy is transformed into heat, but a
small proportion is transformed into X-rays.

X-ray machine consists of
Tube: Cathode + Anode

Head
Accessories:
Filters + collimators + cones

Automatic
Timer

Manual

X-ray Tubehead

support arms

Tubehead

Timer


Automatic timers

1- Direct or immediate timers: It attached
to a long cord to enable the operator to
go away from the field of radiation.
Operator press on a button just to
activate the exposure while the time is
pre adjusted and the exposure will stop
automatically even if the operator
continuous to press the button.

2- Delayed timers: This type provide about 9
second before the start of exposure, so it
provides the operator a period to get away
from the field of radiation.

Timer

exposure time
adjustment


Manual timers
- Direct type in old x-ray machines

-The exposure is controlled manually
(like the clock alarm) and exposure will
stop only if the operator stop pressing
on the button.

- The main disadvantage of this type
that it adjusted only for 1 second not in
fraction of seconds.

Manual Timer

Head of X-ray machine.

It consists of two main parts

Tube

Accessories.


The Tube
The Tube is an Evacuated glass tube with
two arms or electrodes extending in two
opposite directions, which are the cathode and
anode.

The tube is evacuated for two reasons
1) This will prevent collision of the moving
electrons with the molecules of the air.
2) This evacuation will prevent oxidation and
burn out of the filaments.

Tube head of X-ray machine


Cathode
It is the negative electrode of the
tube, which serves as the source
of electrons. It consists of two
parts

a) Filament.

b) Focusing cup.

Cathode

Filament
(tungsten)

Focusing
cup
(molybdenum)

Filament
It made of tungsten coil, which is 0.2cm in
diameter and 1 cm or less in length.

Tungsten is used because;
1) It has a very high melting point so it can
withstand the high temperature accompanied
with the process of X-ray production.

2) It has a high atomic number, which
denoting a high number of protons resulting in
high number of electrons.

Focusing cup

It is a negatively charged concave
reflector cup made of molybdenum, act as
focusing to the electrons to a narrow beam
to fall on the target.

The high negative charge of the cathode
repels the negatively charged electrons,
thus this cup collects the electrons and
repels them till the anode attracts them.


Electrons Emission
Release of electrons from hot filament when
current flows after depressing exposure switch

hot
filament
filament
electrons

The hotter the filament gets, the greater
the number of electrons that are released.

Anode

It consisting of two main parts

a) Target.

b) Copper head.


Anode

side view front view

Target
Copper head Target


Target

It made up of tungsten due to

1) It has a very high atomic number (i.e.
large number of protons and electrons).

2) It has a high melting point.

3) It has a very poor thermal conductivity.


Copper head

Due to the poor thermal conductivity
of the tungsten target, it is embedded
in a large block of copper, which is a
good thermal conductor so it allows
proper dissipation of heat which
accompanies the process of X-ray
production.


X-ray Production


A simplified diagram of x-ray tube 220 v

Cathode Anode
Step-down Step-up
transformer transformer

Filament 60-90 kvp
E Target
8-12 v
Copper
head

Focusing cup 1ry Ray
Insulating oil

Metal housing
Evacuated Glass tube

Useful beam

Production of X-rays
Terminology:

Volt
Voltage
Ampere
Transformer

Volt: It is the unit of electrical pressure or
electromotive force necessary to produce
a current of 1 ampere through a
resistance of 1 ohm.

OR

It is the unit of measuring the potential
difference of a charge to move from one
electrode to the other


Voltage: It is the potential or
electromotive force of an electric charge,
expressed in volts.

OR

The potential difference between 2
electrical charges, e.g. between cathode
and anode.


Ampere: It is the practical unit of quantity
of electronic current, equal to a flow of 1
coulomb per second or the flow of 6.25 x
1018 electrons per second.


Transformer: It is an electrical device,
which increases or reduces the voltage of
an alternating current by mutual induction
between primary and secondary coils.

 Step-down transformer: A transformer in
which the secondary voltage is less than
primary voltage.

 Step-up transformer: A transformer in
which the secondary voltage is greater than
the primary voltage.

The principles of X-ray production

When an electric current, -which composed of
a steam of negatively charged electrons having
kinetic energy- passes through a filament or
wire, it will be heated so the orbiting electrons
within its atoms will acquire sufficient energy to
escape from their shells. Finally this electron
cloud will be given from the heated wire of
filament.
If these electrons sudden stopped, they will
loose the accompanying kinetic energy and
converted into heat and X radiation.

Application of this principle on dental
X-ray machine
The step-down transformer will decrease the
electric current into 8-12 volts.

This current is sufficient enough to heat the
tungsten filament of the cathode and produce
electrons according to the degree of heating
by thermo ionic emission.

These electrons will form a cloud around the
cathode, which will be collected by the concave
focusing cup but they have no velocity to move.


The step-up transformer will raise the potential
difference between the cathode and the anode
by raising the voltage into 60-70 KV.
This increase in potential difference will
accelerate the electron cloud to move towards
the anode, as there is a force of attraction
between the positive anode and the negative
cathode.
By the action of the focusing cup, the electrons
will hit only the tungsten target of the anode,
loosing their kinetic energy in a form of 99.8%
heat and only 0.2% X-rays.
The produced X-rays (primary beam) are
conducted to get out from the tube housing
through the filters and collimators to be used as
a useful beam.

Tube of x-ray machine


X-ray Machine Components

oil

filament filter

exposure
button


Accessories

Filters

Collimators

Cones


Filters
A thin sheet of pure aluminum placed in the way of
the X-ray beam at the end of the X-ray tube in
order to improve the quality of the beam.

The X-ray beam is heterogeneous in characteristics
i.e. containing a ray of different energies and
wavelength. Because of this, the filter is used in
order to absorb unnecessary x-rays of the longer
wavelengths being both useless in radiography and
dangerous to the patient and the dentist.

The thickness of the filters varies according to the
Kvp of the machine being used, 2mm.Al thickness
with up to 70Kvp and 2.5mm over 70Kvp.

PID

The filter is usually
located in the end of
the PID which
attaches to the
tubehead.
filter

Types of filters

Added filters: They are external filters that
can be removed or added by the clinician.

Inherent filters: These include the glass wall
of the X-ray tube, The insulating oil, and
the metal housing

Total filters = Inherent filters + added
filters.

Total Filtration

Aluminum filter (s)

Added

2.5 mm

Glass window
Total 70 kVp
Oil/Metal barrier 1.5 mm
of x-ray tube
Inherent

01/25/13 00:59

Collimator

It is a device used to limit or restrict
the size of an X-ray beam just to
cover the film to produce the desire
image.


Types of collimators
Diaphragm collimator: A thin sheet of lead with an
opening in the center.

Tubular collimator: A tube of lead with one of its ends
connected or in conjunction to the diaphragm
collimator. This tube will help in decrease diverging
rays and almost increase more parallel rays, which in
turn helps in increase quality of image and more safe
to the patient.

Rectangular collimators: It provides a beam of a
rectangular shape that larger than the size of
Periapical films.

Collimation
front views side view

collimated
collimator beam

target
(x-ray source)

2.75 inches (7 cm) = maximum diameter of circular beam or maximum
length of long side of rectangular beam at end of PID.

Collimator

You are looking up through the PID at the collimator, which is
a circular lead washer with a circular cutout in the middle. This
will produce a round x-ray beam. The light gray area in the
center is an aluminum filter, which is placed on the tubehead
side of the PID.

7 cm If you switch from a
6 cm 7 cm round PID to a 6
cm round PID, the
6 cm round
patient receives 25%
less radiation.

film
(4.5 cm long)

Rectangular collimation
results in 55 % less
entrance radiation when compared
to 7 cm round PID.
entrance
exit
exit


Cones, Position indicating device
(PID)

It is a device used to

1-Fix the target film distance
2-Indicate the point of the entry

3-Determine the direction and distribution of
the X-ray tube.


It may make of plastic, glass or metal. The majority
of cones are made of plastic because it is light. In
case of metal one (lead) it may act as collimator and
cone in the same time, but it is not practical as it
very heavy on the tube itself and will cause decrease
beam intensity as some of it will be absorbed by the
lead.

It may be of opened end or pointed end shape. The
pointed end shape has harmful effects that it acts
as a source of scattered radiation as the rays will
hit its walls.

It may be short one 8” or long one 16”.


16” FFD image
Target
16” from film Target
8” from film 8” FFD image
Film
Increasing the distance from the target of the x-ray tube
(focal spot, focus) to the object (teeth/film) (FFD = focus-film
distance) will result in an increase in sharpness and a decrease in
magnification. This results when a longer PID (cone) is used.

Moving the film closer to the teeth will also increase sharpness
and decrease magnification.

Types of X-ray


Types of X-Radiation
1- Primary radiation.
2- Useful beam
3- Central ray
4- Secondary radiation
5- Scattered radiation
6- Stray radiation
7- Remnant radiation
8- Leakage radiation
9- Soft radiation
10-Hard radiation

Primary radiation: It is the radiation coming
directly out of the target, most of it is
absorbed by the tube housing except for
the useful beam.

Useful beam: It is that part of the primary
radiation, which is not absorbed by the
housing but passes through the apparatus
and affects the film.

Central ray: It is that part occupying the
central portion of the useful beam on
which the rays are relatively parallel to
each other.

Secondary radiation: It is that radiation
generated from the patient’s surrounding
objects due to passage, interaction of the
primary beam with these objects. They are
of a long wavelength and so increased
absorption and are more dangerous to the
patient.

Scattered radiation: It is a form of
secondary radiation which has been
deviated in direction during passage of the
X- rays through objects.

Stray radiation: This radiation occurs when
the primary beam hits a metal heavier
than AL, e.g. metallic eyeglasses.

Remnant radiation: It is that portion of
radiation remaining or emerging from the
object after the passage of the primary
beam through it, to expose the film and
produce the image.

Leakage radiation: The radiation that escapes
through the protective housing of the X-
ray tube.

Soft radiation: Radiation produced by
decreased kilo-voltage, are of longer
wavelength, decreased penetration, increased
absorption so have a more damaging effect.

Hard radiation: Radiation produced by
increased kilo-voltage, are of shorter
wavelength, increased energy, increased
penetration, decreased absorption and are
the ones used to produce the image, i.e. of
diagnostic value.

Factors affecting the quality of an image

Terminology
Image
Contrast
Density
Exposure
Roentgen
Rad
Rem

Image:
The representation or semblance of a
structure or structures produced by
passage of X-radiation,
visible only when transmitted onto a
fluorescent screen or an x-ray film (in the
latter case, visible only after processing
the film).


Contrast:
It is the difference in density appearing
on a radiograph.
OR
Is the differentiation between black,
white and gray shades on the radiograph.


Density:
It is the degree of darkening of exposed
and processed photographic or x-ray film,
expressed as the logarithm of the opacity
of a given area of the film.


Exposure:
A measure of the x radiation to which a
person or object, or a part of either, is
exposed at a certain place, this measure
being based on its ability to produce
ionization.


Roentgen; R:
X-radiation has a property of causing
ionization of the matter that passes
through it.
So, the unit of x-rays is Roentgen, which is
the measurement of ionization.

It is defined as the amount of radiation
that passes in one c.c. air producing two
billion ion pairs (–ve and +ve) under
standard conditions of temperature and
atmospheric pressure

Rad:
It is unit of absorbed dose; it is amount of
ionizing Radiation absorbed dose by one gram
of the tissues.

Rem:
It is the unit of biological damaging effect of
radiation (B.D.E),
it is the amount of ionizing radiation produces
biologic damage effects (B.D.E) in one gram
of tissue.
It is Roentgen equivalent mass, i.e.
measurement unit denoting amount of a
radiation dose that produced biological
damaging effects equal that in a person with
one Roentgen of X-ray.

The factors affecting the quality
of an image
1- Kilo-voltage
2- Milliamp rage
3- Collimation
4- Filtration
5- Distance
6- Atomic number and thickness (density) of the

object


Kilo-voltage
Kilo voltage power of conventional dental X-
ray machine ranges from 65-90 kvp.

X-ray penetration power is controlled with kvp,
i.e. the higher the kvp is, the shorter
wavelength x-ray with high penetration power.

So kvp is the factors, which determine the
quality of the x-ray beam, and when the
thickness of the structure increased we need a
higher kvp.


Kilo-voltage
If the kvp is increased above the normal
range it will affect the contrast of the image.

In this case of very high kvp, the penetration
power of the x-ray will increase resulting in
nearly complete penetration of the objects and
finally blacking the film and the areas which
should have been white (as metal) will appear
gray.
The end result of such image will be image
with black and gray shades with low contrast
image (long gray scale).

Kilo-voltage

If the kvp will decrease than the normal, the
penetration power of the beam will decreased
resulting in image with white color
representing hard objects and few blacking or
gray represent soft tissue objects, which is
called high contrast image or (low gray scale).
Thus an optimum contrast is required which is
achieved by range of kvp between 65-90, any
alterations in this range either increase or
decrease will affect the quality of the image
contrast.

Milliamp rage

The normal range of mA is about 5-15, it
is affecting the quantity of the x-ray.

By controlling mA and time we can
control the quantity of the beam, and
thus control the density of the image.


Milliamp rage

The higher mA (within normal range) will
result in increase the quantity of the current,
increase heating of the coil, increase the
amount of electrons emitted, increase the
number of x-ray photons, increase the amount
of x-ray reaching the film, with final resultant
of increasing the amount of blacking of the
image resulting in an image with good density.


While if the mA is increased above the
normal range this will result in increasing
the darkness of the image (high density),
which may controlled or avoided by
decreasing the time of exposure.


If the mA is low than the normal range
it will result in a very light image with
low density, which is may control by
increasing the exposure time.


Collimation
Collimators exerts three main functions,
the first increase the safety to the patient,
the second, increase the quality of the image
the third is increase the sharpness of the
image.
It helps on reduction the amount of x-ray
reached to the patient and in the same time
increase the image quality by decreasing the
amount of scattered radiation. The image
sharpness will also increased by reduction of
the beam size, leads to reduction the more
diverging rays and increase the more parallel
rays.

Filtration

Proper filtration will provide x-rays with
short wavelength, results in a good
quality image.
Over-filtration will result in decrease the
amount of x- ray photons and in
decreased density image, while under-
filtration will give a long wavelength x-
rays with low penetration power and low
contrast image..

Distance
The distance between the source and the object
may affect the image quality as follow;
if the distance is increased, the intensity of the
beam will decreased leading to decrease of the
quality of the rays and affection to the density,
but in the same time if the distance is increased
it help on production of less diverging rays
leading to increase the quality of the beam and
increase the sharpness.
If the distance is decrease, this will help on
increase the intensity of the beam and increase
the density; while in the same time will increase
the divergent rays leading to decrease the
sharpness.

Atomic number and thickness (density)
of the object
As the atomic number, density and
thickness of the object increase, the
need for more powerful x-radiation will
increase to produce a good image. So the
kvp should increased but within limits in
order not to alter the contrast. So this
may compensate with increase the
exposure time, but also within limits in
order not to affect the density.

Dental X-ray film


Dental X-ray film
It is a thin, transparent sheet of plastic
material coated on both sides with an
emulsion sensitive to radiation and light.

Radiographic films closely resemble the films
used by photographers to produce black and
white negatives.

There are differences in that photographic
films only carry an emulsion on one side of
the film base, whereas both sides of
radiographic films are coated, to double the
response to an X-ray exposure.

The X-ray film basically consists of
four components:
 Film base

 Adhesive layer

 Film emulsion

 Protective layer


Film base

Is a flexible piece of plastic, about 0.008
inches thick to provide the desired degree of
stiffness and flatness for handling.

It is transparent and has a slight blue tint
to make it easier to visualize the image.

Film base serve as a stable support for the
emulsion.


Adhesive layer

It is a thin layer of adhesive
material to act as attachment
between the base and emulsion from
both sides.


Film emulsion
1. This is the most important constituent of
the film.

2. It is a homogeneous mixture of gelatin and
silver halide crystals coated on both sides of
the film base to provide maximum speed to
the film (sensitivity).

3. Gelatin is used to suspend and evenly
disperse the silver halide crystals.

4. Halide crystal is a chemical compound
that is sensitive to radiation or light.

5. The halides used in a dental X-ray film
are silver bromide and to a lesser
extent silver iodide.

6. On exposure to the X-ray this silver
bromide absorb the rays and physical
changes take place in the emulsion.
This change called the latent image.

Protective layer

It is a thin, transparent, clear
layer of gelatin covers the emulsion to
protect it from mechanical damage.


What is the latent image and how it formed?

Silver bromide crystals absorb X-radiation, and
store the energy of the radiation as a certain
pattern to an extent depending on the density of
objects.

This pattern of energy on the exposed film cannot
be seen and is referred to as latent image.

The latent image remains invisible within the
emulsion until the film undergoes chemical processing,
then it become visible.


When the X-ray hit the surface of
emulsion, the silver bromide crystals that
exposed to the rays ionized and separated
to silver and bromide atoms.

However, when the exposed film is
treated with a solution called a developer, a
chemical reaction takes place, and the
exposed grains of silver compound are
transformed to tiny masses of black metallic
silver.

The unexposed grains are essentially
unaffected. It is this silver suspended in
the gelatin that constitutes the visible image
on the radiograph.

Latent Image
Air/soft tissue Bone Amalgam/Metal
Many x-rays Fewer x-rays Few, if any, x-rays
penetrate and ionize penetrate and not as penetrate; silver
many silver halide many silver halide halide crystals not
crystals crystals are exposed exposed


Types of Dental X-ray films

Intra-oral films

Extra-oral films


Films used in dental radiography come in a
variety of sizes and packaging.

Those of the smaller sizes suitable for
Intra-oral use, ranging from 22 to 31 mm
across and from 35 to 54 mm in length,
come individually enclosed in light-tight
envelopes of thin plastic or paper.

Other films of large size are used for
extra-oral exposure in dental radiography.
They positioned outside the oral cavity in a
special light protected holder (cassette)
that is loaded within the selected film inside
the dark room.

I- Intra-oral films

Intra-oral films usually supplied inside special
film packets. The film packet consists of:

1-Outer packet wrapping or envelope

2-Black paper film wrapping

3-The film

4-Lead foil sheet


black paper
surrounds film;
protects emulsion

film
single or double;
raised dot in one corner

lead foil
protects film from backscatter; reduces patient
exposure; strengthens packet; pattern identifies when
film is placed backwards (reversed)

Outer packet wrapping or envelope:

It is a soft plastic wrapper to protect the film
completely from the light and saliva.

It has two sides; white smooth side (tube side),
which has a raised bump on one corner, corresponds
to the identification dot on the film.

The other side (the label side) has a flap used to
open the film packet during processing.
It contains data about the number of films per
packet, and the film speed.
It also contains a circle of concave dot that
represent the identification dot of the film.

Outer film cover
Keeps out light and moisture; protects emulsion

plastic dot paper

# of films
in packet

#2 Tab #2 #1


Black paper film wrapping:

Are two black papers enclose the film
between them and further protect it
from light.


The film:
It is a double emulsion film; the
packet may contain one or two films.

At one of the film corners there is a
small raised dot (identification dot). It
used after film processing to
distinguish between the left and right
side of the patient mouth during
reading of radiograph (interpretation).

This identification dot or bump has a
convex and concave surfaces the convex
surface should face the rays while the
concave side being back to the film during
exposure.

Also it should be always away from any
anatomical landmarks to avoid misdiagnosed
as any pathologic lesion, so it should be
occlusally or incisally during exposure.


Lead foil sheet:

Placed back to the film away from
the smooth side of the film packet
(back side).

Its function is to absorb the back
scattered radiation and thus protects
the film from fogging.


It also adds to the rigidity of the
film packets.

It has a special pattern (herring
bone) stamped on the exposed
finished radiograph if the film is
exposed from the wrong side.(back
side film)


Backscatter
(scattered x-rays that go
“back” toward the film)

Primary x-rays
Scatter (secondary) x-rays

Reversed Films (back side film)


Types of intra-oral films


Intra-oral films
Intra-oral films can be classified mainly
according to their usage into

Periapical films

Bite-wing films

Occlusal films.


Also intra-oral films can classified
according their

* Speed

* Size

* Number of films per packet

* Whether the film packet is lead
backed or not.

Classification of intra-oral films
according to use

Periapical films
Occlusal films

Bite wing films

Periapical Film

Periapical pathology

Apical pathology
Periodontal evaluation internal
resorption
Caries detection
Endodontic treatment

caries

Periapical films
It is the most frequently used intra-oral
view, which shows the entire tooth and
surrounding structure on the film.

There are three basic sizes for Periapical
films,
No. 0 or child film 22x35mm.
No. 1 or narrow adult 27x54mm.
No. 2, or standard adult film 31x41mm.

Periapical films used to exam the following:


I-Enamel:

1-Normally appears as a Radiopaque
structure.

2-Caries of the enamel: which appears as a
radiolucent area.

3-Enamel hypoplasia: appears as a
radiolucent area surrounded with radio-
opaque margin.

4-Amilogenesis imperfecta: all the enamel
appears as radiolucent area.

5-Congenital syphilis: Hutchinson’s incisors;
appears as v-shaped radiolucent area
surrounded by radio-opacity.


II-Dentin:

1-Normally appears as a Radiopaque structure

-2Caries of the dentin; appears as a v-
shaped radiolucent area.

3-Dentinogenesis imperfecta: dentin appears
as a radiolucent area surrounded by faint
radio-opaque margin

4-Dense in dente: appears as a radio-opaque
structure within the tooth surrounded by
radiolucent margin.

5- Internal resorption: radiolucent lines on
the apex or lateral side of the root dentin.


III-Pulp:

1-Normally appears as a
radiolucent area within the
tooth.

2-Calcification of the pulp: appears
as a localized area of radiopacity
= pulp stone. If it generalized it
appears as a generalized
radioopacity of the pulp
chamber.

3-Shell tooth : appears as a wide
pulp chamber.


IV-Cementum:

1-Normally it cannot be differentiated from the
dentin.

2-Hypercementosis: appears as Radiopaque
areas cover the cementum line.

3-Cementoma: appears at the apex of the tooth
as a radiolucent area in its early stages and
converted into a Radiopaque area at its
terminal stages.

V-Periodontal ligament space:

1-Normally appears as a
radiolucent line surround the
root surface

2-Narrowing of it as a result
of an oeteoblastic process
e.g. scleroderma

3-Widening of the space as
results of osteolytic process
e.g. osteolytic osteoma, .

VI-Lamina dura:

-Appears as Radiopaque clear
continues band covers the
alveolar bone ie. lining the
socket and cover the crest
of the crest of alveolar
bone (crestal lamina dura).

-Discontinuities of lamina
dura indicate pathological
changes.

VII-Alveolar bone:

Bone resorption either horizontal or
vertical.


Bite wing films
These films often have a paper tab projecting
from the middle of the film, on which the
patient bites to support the film. This tab is
not visualized and does not interfere with the
diagnostic quality of the image.
It used to record the coronal portions of
maxillary and mandibular teeth in one image.
The apices of the teeth are not shown.
It used for the following:


Bitewing Film

Interproximal Caries
Alveolar Bone Involvement

Overhanging amalgam filling


1. Detection of initial proximal caries.
2. Detection proximal overhanging margins of
fillings and crowns.
3. Approximate estimation of the size of the
pulp chamber and pulp horns.
4. Detection of initial interproximal crestal
alveolar bone resorption indicating
periodontal disease.
5. Determination of the position of permanent
forming teeth in relation to deciduous
ones.
6. Determination of any proximal calculus
formation.

Detection of proximal caries by bite wing
radiographs compare to Periapical
radiograph


Occlusal films

Occlusal films are use to radiographically
clarify the anatomical structures and
the pathological conditions of the
maxilla or mandible in the bucco-lingual
dimension.

Occlusal films may use for the following
purposes:

Occlusal Film
Identify large lesions
Locate bucco-lingually
Developing anterior teeth
Imaging trismus patients


1. Obtaining gross views for the jaws in the
bucco-lingual dimension.
2. Detection location and extent of fractures.
3. Detection of the bucco-lingual direction of
impactions and supernumerary teeth.
4. Detection of bucco-lingual direction of
displaced fracture.
5. Detection of salivary gland or duct stone
especially in the mandible.
6. Localization of foreign bodies such as
broken needle.
7. Determination of the shape of dental
arches.

according to the speed

Film speed (sensitivity) can be
defined as the efficiency by which a
film can respond to an X-ray exposure,

i.e; a fast film requires low exposure
time to produce a standard density
image, while a slow film requires longer
time of exposure to produce the same
standard quality.


or it refers to the amount of
radiation required to produce a
radiograph of standard density.

Intra-oral films vary in speed,
fast films need less X-radiation and
using such films routinely plays a
major role in the field of radiation
protection.

Factors affecting film speed

1-Whether the film is coated only on one side
with the silver halide grains (slow films) or on
both sides (medium and fast films)

2-The size of the silver halide grains, the
larger the size, the more sensitive the film.


• The speed of dental X-ray films is expressed
in a letter form.

• Speed groups are A, B, C, D, E and F

• A being the slowest film and each subsequent
group being approximately twice as fast as
the preceding group to give a final image of
the same object with the same density.

• This mean that; for example: E-speed film
requires one half the exposure time of D-
speed film.

Groups A & B are called slow films (regular).

Group C is called medium speed (radiatized).

Groups D & E are called high speed films (ultra-
speed and ecta-speed respectively).

Groups D-speed films and E-speed films are the
most common intra-oral film in every day’s use.

Kodak introduced E-speed plus film, this film
provides the superior image quality of D-speed film
at a reduced radiation exposure.


according to size:
Periapical and bitewing film comes in three sizes:

0 For small children (about 22 X 35mm)

1 Which is relatively narrow and used for anterior
projections (about 24 X 40mm)

2 The standard film used for adults (about 32 X
41mm(


.according to number of films per packets

Usually intra-oral films supply in packets
containing one film. Some film packets
include 2 films instead of 1.

This may be helpful for record keeping,
research purposes, teaching purposes,
medico-legal aspects or if it is meant to
control the density of each of the 2 films in
a different way during processing.


Film Processing


Processing

It is a chemical treatment, which is
applied to the Exposed film to convert the
invisible latent image to visible image from
which useful diagnostic data can be
obtained


Latent image formation
1. After film exposure, the silver halide molecules in the
emulsion that become exposed will absorb the X-ray and
undergo ionized.

2. As a result of this ionization; minute amounts of metallic
silver are formed on crystal surface & bromide is liberated.

3. The degree of ionization within the crystals depends upon
the amount of exposure received (latent image).

4. The image remains within the emulsion till changed into
silver image by chemical processing.

5. In definition, the processing of the film is the process of
changing of the latent image into a visible image from which
01/25/13 00:59 diagnosis can be obtained.
useful Ossama El-Shall

Chemistry of processing
There are five major steps of chemical
processing:

1- Developing,
2- Rinsing.
3- Fixation.
4- washing.
5- drying.

1-Developing
Developer solution treats the exposed grains (ionized). Developer
solution has affinity to react with bromide part of the crystal
leaving the black reduced silver grains. It consists of five
elements:

1-Reducing agent: It converts the exposed silver crystals into
black metallic silver. It consists of Metol and Hydroquinone.
2-Activator: Sodium Carbonate; it swells and softens the
emulsion gelatin and provide alkalinity for the reducing
agent.
3-Restrainer: K. Bromide; it slow down rate of development of
unexposed crystals, so it restrain the reducing agent from
making the film fogged appears .
4-Preservative agent: Sodium sulphate; it prevent oxidization.
5-Water as dissolving agents.

Developing
Crystal centers converted to black
metallic silver

Air/soft tissue Bone Amalgam/metal


Developing (continued)
Entire crystal converted to
black metallic silver

Air/soft tissue Bone Amalgam/gold


2-Rinsing
With fresh water in order to
1- Neutralize the alkalinity of the developer
solution

2- To stop the developer action

3- Remove the remnants of developer solution
from the film

3-Fixation
It removes the unexposed undeveloped silver bromide
granules and hardens the gelatin. It consists of:
Clearing agent: Aluminum thiosulfate, it clear the
unexposed silver bromides.
Acidifier: Acetic acid, to provide required acidity to
neutralize the developer alkalinity.
Hardener: Aluminum chloride, to shrinks and
hardens the gelatin.
Preservative: Sodium sulphate: it maintains the
chemical balance of fixer chemicals.
Water as a solvent.

Fixing
Unexposed crystals removed
from film

Air/soft tissue Bone Amalgam/metal


4-Washing: with water to remove all the
residual processing chemicals.

5-Drying: with air or dryer to makes the film
finally ready for interpretation and
mounting, and facilitates film handling
with lesser mechanical damage.


Methods of processing.
1. Fixed time and temperature. (Manual)
2. Visual method. (Manual)
3. Automatic processing:
4. Polaroid land radiography.
5. Inject able intra-oral films.
6. Self-processing solutions contained intra-
oral films.
7. Film less dental radiographic tech.

1-Fixed time and temperature.
1- It is a reliable and standardized method
2- The optimal temp. is 20
3- The higher temp. the less time required and vice
versa

4- the fixed times for each step are:
a- 5min developing
b-15-20 sec. for rinsing
c-10min. Fixation
d-20 sec. washing


2-Visual method.

1. Films are immersed in developer and
removed every now and then to be
checked on safe light till image is visible

2. Then rinsed and fixed

3. It is not standardized method as it
depends mainly on human factors

3-Automatic processing

Automatic processor is a special machine, which
can perform all the steps of processing of both
extra-oral and intra-oral films until the dry
radiograph is obtained in about 5 minutes.

The film is opened manually in a light tight
compartment of the machine and then placed in
its place to be automatically carried by the rollers
of the machine from one step to the other.


Advantages of automatic processor:
1-Rapid and easy method
2-Standardization of processing.
3-No need for dark room and its equipments.

Disadvantages of automatic processor:
1-Highly expensive.
2-Need for regular maintenance
3-Need minimum amounts of films per day
4-High temperature of machine tends to produce
chemical fog in the radiograph and rapid
deteriorates the strength of the solutions.

Automatic Processor

Drying
Elements

Film Film
Entry
Exit

Developing Water Fixing
01/25/13 00:59
Solution Rinse El-Shall
Ossama

Solution

dr yer

fi xer

rin se
water

p er
v elo s
de ilm
f
rt
in se

Daylight Loader

4-Polaroid land radiography.
Extra-oral films could be made using an emulsion on
a paper backing instead of the usual film base.

A special cassette and screen are used during film
exposure by conventional dental x-ray machine.

It required more exposure time but processing is a
one step dry method, only 10 sec. carried out in a
special electric small table top unit.

5-Injectable intra-oral films.
In these types of processing, the processing solutions are
respectively injected into the closed film packed which is
supplied with an inject able sits. As processing takes place
inside the packet, such film packets must have no lead foil
or black paper folds.
Advantage of inject able intra-oral films:
1-Easy and rapid method.
2-No need for the dark room.
Disadvantage of this method:
1-Fogged image.
2-Need further fixation to avoid loosing details.


6-Self-processing solutions contained
intra-oral films.

These films contain 2 small packets attached to
the film packet. After exposure, they are
pulled one after one to pour first the developer
and then the fixer into the film packet. This
method has the same advantage and
disadvantage of the injection method.


The Dark Room
 Light tight (against light leakage).
 Both white light and safe light illumination: The white
light is used for cleaning the tanks and preparation of the
solutions. The safe light is used during opining film
packets and processing.
 Safe light specifications.
 Coin on film test.
 Processing tanks.
 Running water source.
 Timer. Either stop watch or florescent.
 Thermometer.
 Dryer.
 Storage space.

Processing tanks


Films holder


Safelight Filters

Morlite GBX-2
D-speed Intraoral, Extraoral
(all films)


Safe lighting


Safelight Test
(Coin on film test)

Problem

Everything OK


Intra-Oral Radiographic
Techniques.


1. Techniques for Periapical radiographs.

2. Techniques for Bite-wing radiographs.

3. Techniques for Occlusal radiographs.


Periapical radiographic techniques.

Typical 14 Periapical film survey for adults


Typical 14 film survey for adults
The central rays is targeted onto the apex; depiction of the
alveolar crest is of only secondary importance.

Periodontal 14-film survey for adults
The central rays is targeted onto the alveolar crest; depiction
of the root apices is only of secondary importance.

Techniques for Periapical
radiography

Paralleling technique

Bisecting angel technique.


Right angle technique
Long cone technique


Head Position

Head position for the
paralleling technique is
not critical, since you
will be aligning the PID
with the ring.


correct incorrect
In the paralleling technique, the film is positioned in the mouth so
that the long axis of the film and the long axis of the tooth are
parallel. We can not see the long axes of the teeth but, in general,
all the teeth incline toward the middle of the head. Thus the
film/instrument will almost always be tipped slightly (up or down,
depending on the arch). In the illustration above right, the film is
placed straight up and down and is not parallel; the patient is
unable to close completely on the biteblock and the apices of the
teeth would not appear on the film.


Rinn XCP Paralleling Instruments

ANTERIOR POSTERIOR


?Why long cone
To prevent the magnification of the
image and the un-sharpness of the film
due to increasing the film object
distance

A parallel non-diverging x-ray beam is
required, this is achieved by increase
target film distance by using a long
cone (16inches)

Sharpness

Measures how well the details
(boundaries) of an object are reproduced
on a radiograph

Increased by:
Source-object distance
Object-film distance
Film crystal size
Motion will decrease sharpness


Magnification

Decreased by:
Source-object distance
Object-film distance


Target-object-film relation.

target Object Film


8" FFD

12" FFD

Most newer x-ray machines have a recessed target
(away from the PID). This helps to increase the
focus-film distance (FFD), resulting in a sharper
image and less magnification without an increase in
the length of the PID (position indicating device). A
longer PID is effective, but it makes positioning the
tubehead more difficult.

Object-film distance small

bisecting
paralleling


Maxillary anterior region

Photograph and radiograph of the region


Maxillary anterior region

Film holder and positioning for maxillary anterior area


Maxillary Incisor

centered on contact between film placed far back in
central and lateral incisors patient’s mouth


Maxillary canine region



Maxillary canine region

Film holder and positioning for maxillary canine area


Maxillary Canine

film placed against the opposite
film centered on canine side of the arch, far away from
the canine


Maxillary premolar region


Maxillary Premolar

film equidistant from lingual
front edge of film anterior to surfaces of teeth (red
middle of canine; approximately arrows); this opens contacts
centered on 2nd premolar between the teeth.

film in center of palate

Maxillary molar region


Maxillary Molar

film centered on
surfaces of teeth (red
second molar
arrows); this opens contacts
between the teeth.

01/25/13 00:59 Ossama El-Shall film in center of palate

Mandibular anterior region



Mandibular anterior region

Film holder and positioning for mandibular anterior
area


Mandibular Incisor

film positioned away from
film centered on midline teeth, pushing tongue
back slightly


Mandibular canine region



Mandibular canine region

Film holder and positioning for mandibular canine area


Mandibular Canine

film positioned away from
film centered on canine teeth, pushing tongue
back slightly


Mandibular premolar region


Mandibular Premolar

front edge of film anterior to surface of teeth (red
middle of canine; approximately arrows); film placed toward
centered on 2nd premolar center of mouth, displacing
tongue


Mandibular molar region


Mandibular Molar

centered on second molar film equidistant from lingual
surface of teeth; in this case the
film will usually contact lingual of
molars


Bisecting angel technique



X-ray beam

X-ray beam perpendicular to bisecting line

The film is positioned with the long axis vertical and the
dot-end of film extending ¼” beyond the incisal edge.
With the all-white side of film facing the teeth, the finger
pressure is applied at the cervical portion of the crown to
avoid film bending.

The film is positioned with the long axis horizontal and
the dot-end of film extending ¼” beyond the occlusal
surface. With the all-white side of film facing the teeth,
the finger pressure is applied at the cervical portion of
the crown to avoid film bending.

Film placement, as indicated above, is the same for maxilla or
mandible. The film is placed vertically for anterior teeth
(canine to canine) and horizontal for posterior teeth.

The film is held in the proper position using the
thumb (maxillary anterior, above left),
Index finger of opposite hand (all other areas,
above right).

Vertical angulations during
bisecting angle technique

Maxilla (+ve) Mandible(-ve)
Incisors: 45-55 25-15
Canines: 45-50 15-20
Premolars: 35-40 5-15
Molars: 25-30 0-5


Horizontal angulations during
bisecting angle technique

Central rays should be parallel to
interproximal surface of the teeth

Central rays should pass through the contact
area of the teeth.


Advantages of Bisecting Angle Technique
•More comfortable: because the film is placed in the
mouth at an angle to the long axis of the teeth, the film
doesn’t impinge on the tissues as much.

•A film holder, although available, is not needed. Patients
can hold the film in position using a finger.

•No anatomical restrictions: the film can be angled to
accommodate different anatomical situations using this
technique

:Anatomical Variations

Anatomical situations which might require
:using the bisecting angle technique are
a shallow palate

a large palatal tours

a shallow or tender floor of the mouth

(a short lingual frenum (tongue-tie

Disadvantages of Bisecting Angle Technique

•More distortion: because the film and teeth are at an
angle to each other (not parallel( the images will be
distorted.

•Difficult to position x-ray beam: because a film holder is
often not used it is difficult to visualize where the x-ray
beam should be directed.

•Film less stable: using finger retention, the film has more
chance of moving during placement

Distortion

In the bisecting technique, the long axis of the tooth
is not parallel with the long axis of the film.
This results in a distortion of the image produced
using this technique.
In the left radiograph below, the buccal roots appear
much shorter than the palatal root, even though in the
actual tooth the lengths are not that much different.
In the other radiograph taken with the paralleling
technique, the lengths are projected in their proper
relationship (minimal distortion(.

Techniques for Bite-wing
radiography


Diagram of correct film position and central rays
targeting in bite-wing film

The paper extension from the film packet must not be
pulled too much. The central ray is targeted through
either the maxillary second premolar or the first
permanent molar.

Bitewing Head Position

The head should be positioned so that the maxillary
arch is parallel to the floor, both side-to-side and
front-to-back, when using bitewing tabs.

Bitewing Film Placement

Front edge anterior to Film centered on second
middle of mandibular molar (if 3rd molars are
canine (approximately erupted; otherwise center
centered on 2 nd on contact between 1st and
01/25/13 00:59 premolar) Ossama El-Shall 2nd molar).

The stick-on bitewing tab is always centered top-to-
bottom with the film oriented horizontally (see picture
above). The tab is placed on the Clinasept cover on
the all-white side of the film. When some teeth are
missing, the tab may be placed more anteriorly or
posteriorly to allow maximum contact with the teeth
that are present.

The film is placed in the mouth between the
teeth and the tongue. Hold on to the tab and
instruct the patient to close slowly and
completely.

10°

positioning guide

The vertical angulation
is always set at +10
degrees (the tubehead
is pointing downward).


correct incorrect
The horizontal angulation is adjusted so that a line
connecting the front and back edge of the PID (yellow line
above) is parallel with a line connecting the buccal surfaces
of the premolars and molars (green line above). Instruct the
patient to open their lips so that you can see the buccal
surface (see next slide). The front edge of the PID should
be ¼” anterior to the front edge of the film.

Patient opening lips (“smiling with teeth
together”) to allow visualization of buccal
surface of posterior teeth.

Techniques for Occlusal
radiography


Maxillary Topographical Occlusal
Mandibular Topographical Occlusal

Maxillary Vertex Occlusal

Mandibular Cross-Sectional Occlusal

Posterior Oblique Maxillary Occlusal

Posterior Oblique Mandibular Occlusal
Modified Oblique Posterior Mandibular Occlusal


Occlusal Film
-Identify large lesions
-Determine bucco-lingual location
-View developing anterior dentition
-Image patients with trismus (if
panorama not available)


Head Position
Maxillary occlusal: Maxilla parallel to floor
Mandibular occlusal: Mandible perpendicular
to floor
Film Position
Centered on area of interest
All-white side facing x-ray tube
Patient bites gently on film

Exposure Settings
Normal Maxillary = PA/ BW
Mandibular = PA/BW
True Maxillary = 4X PA/BW

X-ray Beam Position
Centered on area of interest
Vertical angulations (see below)


Thank you all for listening

Dr. Ossama El-Shall

E-mail address: oelshall@hotmail.com


Believe in yourself,
for if you don’t
believe in yourself,
it will be hard for
others to believe in

1 dental radiology

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