Foundations of Radiography,
Radiographic Equipment,
and Radiologic Safety
Chapter 38
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Chapter 38
Lesson 38.1
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Learning Objectives
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Pronounce, define, and spell the Key Terms.
Describe the uses of dental radiographs.
Describe the discovery of x-radiation.
Name the highlights in the history of dental
radiography.
Explain what happens during ionization.
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Introduction
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
The dental assistant must have a thorough
knowledge and understanding of the
importance and uses of dental radiographs.
The dental assistant must understand the
fundamental concepts of atomic and
molecular structure and have a working
knowledge of ionizing radiation and the
properties of x-rays.
(Cont’d)
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Introduction
(Cont’d)
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Radiation used to produce dental radiographs
has the capacity to cause damage to all types
of living tissues.
Any exposure to radiation, no matter how
small, has the potential to cause biologic
changes to the operator and the patient.
The dental assistant must have a thorough
understanding of the characteristics of
radiation to minimize radiation exposure to
both the dental patient and the operator.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Discovery of Radiation
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Wilhelm Conrad Roentgen (pronounced rentken), a Bavarian physicist, discovered the xray on November 8, 1895.
For many years x-rays were referred to as
roentgen rays, radiology was referred to as
roentgenology, and radiographs were known
as roentgenographs.
During his lifetime, Roentgen was awarded
many honors and distinctions, including the
first Nobel Prize ever awarded in physics, in
1901.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-1 A, Wilhelm Conrad Roentgen (1845–1923), discoverer
of x-rays.
(From Frommer HH, Stabulas-Savage J: Radiology for the dental professional, ed 8, St Louis, 2005, Mosby.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-1 B, Crookes tube, which Roentgen worked with
at the time of the discovery of x-rays in 1895.
(From Frommer HH, Stabulas-Savage J: Radiology for the dental professional, ed 8, St Louis, 2005, Mosby.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Pioneers in Dental Radiography
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Otto Walkoff made the first dental radiograph.
Dr. C. Edmund Kells, a New Orleans dentist,
is credited with the first practical use of
radiographs in dentistry, in 1896.
Dental radiography has progressed from
these early discoveries to the science it is
today.
New technology continues to improve our
diagnostic abilities.
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Radiation Physics
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All things in this world are composed of
energy and matter.
Energy is defined as the capacity to do work.
Matter is anything that occupies space and
has form or shape.
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Energy
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Although energy can neither be created nor
destroyed, it can change form.
Atoms contain energy.
The energy that holds the nucleus together is
called nuclear-binding energy.
The energy holding electrons, negatively
charged particles, in their shells is known as
electron-binding energy.
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Matter
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Matter has many forms, including solids,
liquids, and gases.
Matter is composed of atoms grouped
together in specific arrangements called
molecules.
A molecule is the smallest particle of
substance that retains the property of the
original substance.
The fundamental unit of matter for discussion
in this chapter is the atom.
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Atomic Structure
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The atom consists of two parts:
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Central nucleus
Orbiting electrons
An atom is identified by the composition of its
nucleus and the arrangement of its orbiting
electrons; at present, 105 different atoms are
known to exist.
(Cont’d)
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Atomic Structure
(Cont’d)
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The arrangement within the atom is similar to
that of the solar system.
The atom has a nucleus as its center or sun,
and the electrons revolve (orbit) around it like
planets.
The electrons remain stable in their orbit
unless disturbed or moved. Orbiting electrons
can be disturbed by x-rays.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-3 Diagrammatic representation of an oxygen atom.
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Nucleus
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The nucleus, or dense core, of the atom is
composed of particles known as protons and
neutrons.
Protons carry positive electrical charges;
neutrons carry no electrical charge.
Dental x-rays do not affect the tightly bound
nucleus of the atom and are only changed in
direction or scattered.
Dental x-rays cannot make atoms radioactive;
therefore patients do not give off x-rays after
the x-ray machine stops producing x-rays.
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Electrons
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Electrons are tiny negatively charged
particles with very little mass.
Electrons orbit around the nucleus of an
atom.
The orbit path of an electron is called an
electron shell. Each shell can contain only a
specific number of electrons.
The electrons are maintained in orbit by
electron-binding energy, a force similar to the
force of gravity on earth.
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Ionization
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The electrons remain stable in their orbits
around the nucleus until x-ray photons collide
with them. (A photon is a minute bundle of
pure energy that has no weight or mass.)
X-rays have enough energy to push an
electron out of its orbit, producing an ion (an
atoms that gains or lose an electron and
becomes electrically unbalanced) in a
process called ionization.
(Cont’d)
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Ionization
(Cont’d)
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Ionization is the process by which electrons
are removed from the orbital shells of
electrically stable atoms through collisions
with x-ray photons.
When an electron is removed from the atom,
an ion pair results.
The harmful ionizing effect of x-rays in
human beings can result in a disruption of
cellular metabolism and can cause
permanent damage to living cells and tissues.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-4 A molecule of water (H2O) consists of two atoms
of hydrogen connected to one atom of oxygen.
(From Haring JI, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Chapter 38
Lesson 38.2
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Learning Objectives
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Describe the properties of x-radiation.
Label the parts of the dental x-ray tubehead
and tube.
Explain how radiographs are produced.
Identify the range of kilovoltage and
milliamperage required for dental
radiography.
(Cont’d)
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Learning Objectives
(Cont’d)
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
Describe the effect of the kilovoltage on the
quality of the x-ray beam.
Describe how the milliamperage affects the
quality of the x-ray beam.
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Properties of X-Rays
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The dental assistant must be familiar with the
unique characteristics of x-rays.
X-rays are a form of energy that can
penetrate matter. Like visible light, radar,
radio, and television waves, they belong to a
group called electromagnetic radiation.
Electromagnetic radiation is made up of
photons that travel through space at the
speed of light in a straight line with a wavelike
motion.
(Cont’d)
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Fig. 38-6 Electromagnetic spectrum, showing the various
wavelengths of radiation typically used.
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Properties of X-Rays
(Cont’d)
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The shorter the wavelength, the greater its
energy.
The high energy of short wavelengths means
that they can penetrate matter more easily
than longer wavelengths can.
X-rays have unique properties that make
them especially useful in dentistry.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-7 A, Wavelength is the distance between the crest (peak) of one wave and the crest
of the next. B, The shorter the wavelength, the greater the energy and penetration,
the longer the wavelength, the less energy and less penetration.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
A
B
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Components of the
Dental X-Ray Machine
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Dental x-ray machines may vary somewhat in
size and appearance, but all machines will
have three primary components:
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The tubehead
An extension arm
The control panel
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Fig. 38-8 Dental x-ray machine and arm.
A, Tubehead. B, Position-indicator device (PID).
C, Extension arm.
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The Tubehead

The x-ray tubehead is tightly sealed; heavy
metal housing contains the x-ray tube that
produces dental x-rays.
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Fig. 38-9 Diagram of the dental x-ray tubehead.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-10 X-ray tube.
(Courtesy of Xintek Inc.)
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Components of the Tubehead
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The metal body of the tubehead that houses
the x-ray tube is called the metal housing. It is
filled with insulating oil.
Insulating oil surrounds the x-ray tube and
prevents overheating by absorbing the heat
created in the production of x-rays.
Tubehead seal is made of leaded glass or
aluminum. It seals the oil in the tubehead.
The x-ray tube is the heart of the x-ray–
generating unit.
(Cont’d)
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Components of the Tubehead
(Cont’d)
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The transformer alters the voltage of incoming
electric current.
The aluminum filter is aluminum sheets 0.5 mm thick.
The lead collimator is a metal disc with a small
opening in the center to control the size and shape of
the x-ray beam as it leaves the tubehead.
The PID is the open-ended, lead-lined cylinder that
extends from the opening of the metal housing of the
tubehead. It is used to aim the x-ray beam.
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The X-Ray Tube
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The vacuum environment allows the
electrons to flow with minimum resistance
between the electrodes:
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
Cathode
Anode
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The Cathode
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The cathode consists of a tungsten filament in
a focusing cup made of molybdenum.
The purpose of the cathode is to supply the
electrons necessary to generate x-rays.
Electrons are generated in the x-ray tube at
the cathode.
The hotter the filament becomes, the more
electrons are produced.
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The Anode
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The anode is the target for the electrons.
It is composed of a tungsten target (a small block of
tungsten) that is embedded in the larger copper stem.
The copper around the target conducts heat away
from the target, reducing wear and tear on the target.
The purpose of the tungsten target is to serve as a
focal spot and convert the bombarding electrons into
x-ray photons.
The x-rays at the center of this beam are known as
the central ray.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-16 The production of dental x-rays occurs in the
x-ray tube.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
The PID
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The open end of the lead-lined PID is placed against
the patient’s face during film exposure.
The PID may be cylindrical or rectangular. The
rectangular PID limits the size of the beam to that of
a dental film.
PIDs used in dentistry are usually 8, 12, or 16 inches
long.
The choice of length is determined by the
radiographic technique being used.
The long (12- to 16-inch) PID is more effective in
reducing exposure to the patient than a short (8-inch)
PID because there is less divergence (separation) of
the beam.
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The Extension Arm
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The extension arm encloses the wire between the
tubehead and the control panel.
It also has an important function in positioning
the tubehead.
The extension arm folds up and can be swiveled from
side to side.
If the extension arm is left in an extended position
when the machine is not in use, the weight of the
tubehead can cause it to become loose, and the
tubehead will drift (slip out of position) after it is
positioned for an exposure.
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The Control Panel
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The control panel of an x-ray unit contains:
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The master switch
Indicator light
Exposure button
Indicator light
Control devices (time, milliamperage [mA]
selector, and kilovoltage [kVp] selector)
A single centrally located control panel may
be used to operate several tubeheads located
in separate treatment rooms.
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How X-Rays Are Produced
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The x-ray machine is plugged into the wall outlet, and
when the machine is turned on the electric current
enters the control panel.
The current travels from the control panel to the
tubehead through electrical wires in the extension arm.
The current travels through the step-down transformer
to the filament of the cathode.
The filament circuit uses 3 to 5 V to heat the tungsten
filament in the cathode portion
of the x-ray tube.
The heating of the filament results in thermionic
emission.
(Cont’d)
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How X-Rays Are Produced
(Cont’d)
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When the exposure button is pushed, the highvoltage circuit is activated.
The electrons in the cloud are accelerated across the
x-ray tube to the anode.
The molybdenum cup in the cathode directs the
electrons to the tungsten target in the anode.
The electrons travel from the cathode to the anode.
When the electrons strike the tungsten target, their
energy of motion (kinetic energy) is converted to xray energy and heat.
(Cont’d)
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How X-Rays Are Produced
(Cont’d)
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Less than 1% of the energy is converted to x-rays;
the remaining 99% is lost as heat.
The heat is carried away from the copper stem and
absorbed by the insulating oil in the tubehead.
The x-rays travel through the unleaded glass window,
the tubehead seal, and the aluminum filter.
The aluminum filter removes the longer-wavelength
x-rays.
The x-ray beam travels through the collimator.
The x-ray beam then travels down the lead-lined PID
and exits at the end of the PID.
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Types of Radiation
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Primary radiation is the x-rays that come from
the target of the x-ray tube.
Secondary radiation is x-radiation that is
created when the primary beam interacts with
matter.
Scatter is a form of secondary radiation. It
results when an x-ray beam has been
deflected from its path by interaction with
matter.
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Fig. 38-17 Types of radiation interaction with the patient.
1, Primary. 2, Secondary. 3, Scatter.
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Visual Characteristics
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Three qualities are necessary for a good
radiograph:
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Contrast
Density
Image detail
The dental assistant must understand how
variations in the character of the x-ray beam
influence the quality of the resulting
radiographs.
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Radiolucency and Radiopacity
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Radiolucent structures allow x-rays to pass through
them.
Radiolucent structures appears dark or black on the
radiograph. Air spaces, soft tissues of the body, and
the dental pulp appear as radiolucent images.
Radiopaque structures do not allow x-rays to pass
through them.
Radiopaque structures appear white or light gray on
the radiograph. Metal, enamel, and dense areas of
bone appear as radiopaque images.
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Fig. 38-18 Bite-wing radiograph showing a radiopaque (white, a)
area of amalgam restoration and radiolucent (black, b) area of
air and cheek tissue.
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Contrast
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The ideal contrast of a film clearly shows the
radiopaque white of a metal restoration, the
radiolucent black of air, and the many shades of gray
between.
Higher kilovoltage produces more penetrating x-rays
and lower radiographic contrast.
A 90-kVp setting requires less exposure time and
produces a radiograph that has low contrast (more
shades of gray).
A 70-kVp setting requires a slightly longer exposure
time and produces a radiograph with high contrast
(fewer shades of gray).
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Fig. 38-19 A, A radiograph produced with lower kilovoltage exhibits
high contrast. Many light and dark areas are seen.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
A
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Fig. 38-19 B, A radiograph produced with higher kilovoltage exhibits low
contrast. Many shades of gray are seen instead of black and white.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
B
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Density
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Density is the overall blackness or darkness
of a film.
A radiograph with the correct density enables
the dentist to view black areas (air spaces),
white areas (enamel, dentin, and bone), and
gray areas (soft tissues).
The degree of density is determined by the
milliampere seconds (mAs).
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Other Factors Influencing Density
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The distance from the x-ray tube to the patient: If the
operator lengthens the source-film distance without
changing the exposure settings, the resulting
radiographs will be light or less dense.
The developing time and temperature can affect the
overall density. If the processing time is too long, the
radiograph will appear dark.
The body size of the patient: A patient who is very
small or thin requires less radiation than a husky,
heavy-boned person.
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Geometric Characteristics
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Three geometric characteristics affect the
quality of the radiograph:
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Sharpness
Magnification
Distortion
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Sharpness
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Sharpness refers to how well the radiograph
reproduces the fine details or distinct outlines
of an object.
Sharpness is sometimes referred to as detail,
resolution, or definition.
The sharpness of an image is influenced by
three :
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
Focal-spot size
Film composition
Movement
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Chapter 38
Lesson 38.3
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Learning Objectives
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Discuss the effects of radiation exposure on
the human body.
Identify the critical organs that are sensitive to
radiation.
Discuss the risks and benefits of dental
radiographs.
Describe the methods of protecting the
patient from excess radiation.
Describe the measures used to protect the
operator from excess radiation.
Discuss the ALARA concept.
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Radiation Safety
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All ionizing radiations are harmful and
produce biologic changes in living tissues.
The amount of x-radiation used in dental
radiography is small, but biologic changes do
occur.
The dental assistant must understand how
the harmful effects of radiation occur and how
to discuss the risks of radiation with patients.
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Ionization
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Ionization is the harmful effect of x-rays in
human beings that can result in a disruption
of cellular metabolism and cause permanent
damage to living cells and tissues.
Ionization is the process by which electrons
are removed from electrically stable atoms
through collisions with x-ray photons.
The atoms that lose electrons become
positive ions; as such, they are unstable and
capable of interacting with (and damaging)
other atoms, tissues, or chemicals.
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Biologic Effects of Radiation
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Exposure to radiation can bring about
changes in body chemicals, cells, tissues,
and organs.
The effects of the radiation may not become
evident for many years after the x-rays were
absorbed.
This time lag is called the latent period.
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Cumulative Effects
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Exposure to radiation has a cumulative effect
over a lifetime.
When tissues are exposed to x-rays, some
damage occurs.
Tissues have the capacity to repair some of
the damage; however, they do not return to
their original state.
The cumulative effect of radiation exposure
can be compared with cumulative effect from
repeated exposure over the years to the rays
of the sun.
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Acute and Chronic Radiation
Exposure
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Acute radiation exposure occurs when a large
dose of radiation is absorbed in a short
period, such as in a nuclear accident.
Chronic radiation exposure occurs when
small amounts of radiation are absorbed
repeatedly over a long period. It may be
years after the original exposure before the
effects of chronic radiation exposure are
observed.
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Genetic and Somatic Effects
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X-rays affect both genetic and somatic cells.
Genetic cells are the reproductive cells
(sperm and ova). Damage to genetic cells is
passed on to succeeding generations. These
changes are referred to as genetic mutations.
All other cells in the body belong to the
classification of somatic tissue. (Somatic
means “referring to the body.”) X-rays can
damage somatic tissue, but the damage is
not passed on to future generations.
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Fig. 38-21 Comparison of somatic and genetic effects
of radiation.
(From Haring J, Jansen L: Dental radiography: principles and techniques, ed 2, Philadelphia, 2000, Saunders.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Critical Organs

Certain organs are considered critical:
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Skin
Thyroid gland
Lens of the eye
Bone marrow
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Radiation Measurements
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Radiation can be measured in a manner
similar to that used to measure time,
distance, and weight.
Two sets of systems are used to define the
way in which radiation is measured.
The older system is referred to as the
traditional or standard system.
The newer system is the metric equivalent,
known as the Système Internationale, or SI.
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Traditional Units of
Radiation Measurement
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The roentgen (R)
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The radiation absorbed dose (rad)
The roentgen equivalent [in] man (rem)
SI units
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Coulombs per kilogram (C/kg)
Gray (Gy)
Sievert (Sv)
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Maximum Permissible Dose
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The maximum permissible dose (MPD) of wholebody radiation for those who are occupationally
exposed to radiation is 5000 mrem (5.0 rem) per
year, or 100 mrem per week.
This amount of radiation to the whole body carries
very little chance of injury.
For nonoccupationally exposed persons, the current
MPD is 500 mrem (5 mSv) per year.
Dental personnel should strive for an occupational
dose of 0 by adhering to strict radiation-protection
practices.
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Radiation Risks and Benefits
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Background radiation comes from natural
sources such as radioactive materials in the
ground and cosmic radiation from space.
Exposure from medical or dental sources is
an additional radiation risk.
When dental radiographs are prescribed and
exposed, the benefit of disease detection far
outweighs the risk of biologic damage from
receiving small doses of radiation.
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Responsibilities of the Dentist
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To prescribe radiographs only for diagnostic
purposes.
To ensure that all radiographic equipment is properly
installed and maintained in a safe working condition.
To provide appropriate shielding to protect staff and
patients from the effects of radiation.
To require that anyone exposing radiographs be
properly trained and appropriately supervised while
exposing radiographs.
To obey all state radiographic licensing requirements,
rules, and regulations.
To participate in obtaining informed consent.
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Equipment for Radiation Protection
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The dental tubehead must be equipped with
certain appropriate components:
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Aluminium filters
Lead collimators
PIDs
Equipment should be checked on a regular
basis by state or federal regulating agencies.
Faulty or malfunctioning equipment should be
repaired immediately.
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Aluminum Filter
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The purpose of the aluminum filter is to
remove the low-energy, long-wavelength, and
least penetrating x-rays from the x-ray beam.
These x-rays are harmful to the patient and
are not useful in producing a diagnosticquality radiograph.
X-ray machines operating at 70 kVp or higher
must have aluminum filtration of 2.5 mm. This
is a federal requirement.
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Collimator
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The collimator is used to restrict the size and
shape of the x-ray beam as a means of
reducing patient exposure.
A collimator may have either a round or
rectangular opening.
A rectangular collimator restricts the beam to
an area slightly larger than a size 2 intraoral
film and significantly reduces patient
exposure.
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The PID
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The PID appears as an extension of the x-ray
tubehead.
It is used to direct the x-ray beam. Round and
rectangular PIDs are available in two lengths:
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Short (8-inch)
Long (16-inch)
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Patient Protection
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Lead apron and thyroid collar:
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A lead apron and thyroid collar must be used on
all patients for all exposures.
This rule applies to all patients, regardless
of the patient’s age or sex or the number of films
being exposed.
The lead apron should cover the patient from
the neck to the lap to protect the reproductive
and blood-forming tissues from scatter
radiation.
Many states mandate the use of a lead
apron.
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Fig. 38-23 The lead apron and thyroid collar must be large
enough to cover the seated patient from the neck to above
the knees.
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Fast-Speed Film
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The size of silver bromide crystals is the main
factor in determining the film speed: the
larger the crystals, the faster the film.
A fast film requires less exposure to produce
a quality radiograph.
Fast-speed film is the single most effective
method of reducing a patient’s exposure to
x-radiation.
Fast-speed film is available for both intraoral
and extraoral radiography.
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Film-Holding Devices
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The use of a film-holding instrument keeps
the patient’s hands and fingers from being
exposed
to x-radiation.
The film holder also keeps the film in a stable
position and helps the operator proper
position the film and the PID.
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Fig. 38-24 The patient’s fingers are unnecessarily
exposed to radiation when film holders are not used.
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Exposure Factors
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Using the proper exposure factors also limits
the amount of x-radiation the patient is
exposed to.
Adjusting the kilovoltage peak, milliamperage,
and time settings controls the exposure
factors.
A setting of 70 to 90 kVp keeps patient
exposure to a minimum.
On some dental units, the kilovoltage peak
and milliamperage settings are preset by the
manufacturer and cannot be adjusted.
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Proper Technique
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Proper technique is necessary to ensure the
diagnostic quality of films and reduce the
amount of radiation to which the patient is
exposed.
Films that are nondiagnostic must be retaken;
this results in additional radiation exposure to
the patient.
Retakes are a major cause of unnecessary
radiation exposure in patients and must be
avoided.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
X-Rays During Pregnancy
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The Guidelines for Prescribing Dental Radiographs,
issued by the American Dental Association in
conjunction with the Food and Drug Administration,
state that dental radiographic procedures “do not
need to be altered because of pregnancy.”
When a lead apron is used during dental radiographic
procedures, the amount of radiation received in the
pelvic region is nearly zero.
There is no detectable exposure to the embryo or
fetus with the use of a lead apron.
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Operator Protection
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A dental assistant who fails to follow the rules
of radiation protection may suffer the results
of chronic radiation exposure.
By following these rules, dental personnel
can keep their radiation exposure to zero.
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Rules for Operator Protection
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Never stand in the direct line of the primary
beam.
Always stand behind a lead barrier, if one is
available, or the proper thickness of drywall.
If a lead barrier is not available, stand at right
angles to the beam.
Never stand closer than 6 feet to the x-ray
unit during an exposure unless you are
behind a barrier.
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Fig. 38-25 For the sake of safety, the dental assistant must
stand out of the path of the primary beam.
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Personnel Monitoring
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Three types of monitoring devices are used to
determine the amount of radiation exposure
to personnel:
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Film badge
Pocket dosimeter (pen style)
Thermoluminescent, or TLD
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Fig. 38-26 A film badge is used to monitor the amount
of radiation that reaches the dental radiographer.
(Courtesy of Global Dosimetry Solutions, Irvine, Calif.)
Copyright © 2009, 2006 by Saunders, an imprint of Elsevier Inc. All rights reserved.
Equipment Monitoring
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Dental x-ray machines must be monitored for
radiation leakage.
If a dental x-ray tubehead has a faulty
tubehead seal, leakage results.
Dental x-ray equipment can be monitored
through the use of a film device that can be
obtained from the manufacturer or from the
state health department.
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If the Patient Cannot Cooperate
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If the patient is a child who is unable to
cooperate, he or she is seated on the parent’s
lap in the dental chair. Both the parent and
child are covered with the lead apron, and the
parent holds the film in place.
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Fig. 38-27 Child sitting on parent’s lap for dental x-ray.
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ALARA Concept
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The ALARA concept states that all exposure
to radiation must be kept to a minimum, or “as
low as reasonably achievable.”
Every possible method of reducing exposure
to radiation should be used to minimize risk.
The radiation-protection measures detailed in
this chapter should be used to minimize
patient, operator, and staff exposure, keeping
radiation exposure “as low as reasonably
achievable.”
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Patient Questions
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Patients often have questions and concerns
about radiation.
As a dental assistant. you must be prepared
to answer such questions and educate the
dental patient about the importance of
radiographs.
(Cont’d)
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Patient Questions
(Cont’d)
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Here are some examples of comments you
can make to patients during informal
discussions:
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“The doctor orders x-rays on the basis of your individual
needs.”
“Our office takes every step possible to protect you from
unnecessary radiation.”
“We use a lead apron and thyroid collar to protect your body
from stray radiation.”
“We use a high-speed film that requires only minimal
amounts of radiation.”
“Do you have any questions before we begin?”
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