1. Chapter 38 Radiation Health & Safety Copyright 2003, Elsevier Science (USA). All rights reserved. No part of this product may be reproduced or transmitted in any form or by any means, electronic or mechanical, including input into or storage in any information system, without permission in writing from the publisher. PowerPoint ® presentation slides may be displayed and may be reproduced in print form for instructional purposes only, provided a proper copyright notice appears on the last page of each print-out. Produced in the United States of America ISBN 0-7216-9770-4

2. Copyright 2003, Elsevier Science (USA). All rights reserved. Introduction 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. 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.

3. Copyright 2003, Elsevier Science (USA). All rights reserved. Introduction  cont’d n Radiation used to produce dental radiographs has the ability to cause damage to all types of living tissues. n Any exposure to radiation, no matter how small, has the potential to cause biologic changes to the operator and patient. n 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. n Radiation used to produce dental radiographs has the ability to cause damage to all types of living tissues. n Any exposure to radiation, no matter how small, has the potential to cause biologic changes to the operator and patient. n 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.

4. Copyright 2003, Elsevier Science (USA). All rights reserved. Discovery of Radiation n Wilhelm Conrad Roentgen (pronounced rent- ken), a Bavarian physicist, discovered the x-ray on November 8, 1895. n For many years, x-rays were referred to as roentgen rays, radiology was referred to as roentgenology, and radiographs were known as roentgenographs. n During his lifetime, Roentgen was awarded many honors and distinctions, including the first Nobel Prize ever awarded in physics in 1901. n Wilhelm Conrad Roentgen (pronounced rent- ken), a Bavarian physicist, discovered the x-ray on November 8, 1895. n For many years, x-rays were referred to as roentgen rays, radiology was referred to as roentgenology, and radiographs were known as roentgenographs. n During his lifetime, Roentgen was awarded many honors and distinctions, including the first Nobel Prize ever awarded in physics in 1901.

5. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-1 Roentgen, the father of x-rays, discovered the early potential of an x-ray beam in 1895. Fig. 38-1

6. Copyright 2003, Elsevier Science (USA). All rights reserved. Pioneers in Dental Radiography n Otto Walkoff made the first dental radiograph. n Dr. C. Edmund Kells, a New Orleans dentist, is credited with the first practical use of radiographs in dentistry in 1896. n Dental radiography has progressed from these early discoveries to the science it is today. n New technology continues to improve our diagnostic abilities. n Otto Walkoff made the first dental radiograph. n Dr. C. Edmund Kells, a New Orleans dentist, is credited with the first practical use of radiographs in dentistry in 1896. n Dental radiography has progressed from these early discoveries to the science it is today. n New technology continues to improve our diagnostic abilities.

7. Copyright 2003, Elsevier Science (USA). All rights reserved. Radiation Physics n All things in this world are composed of energy and matter. n Energy is defined as the ability to do work. n Matter is anything that occupies space and has form or shape. n All things in this world are composed of energy and matter. n Energy is defined as the ability to do work. n Matter is anything that occupies space and has form or shape.

8. Copyright 2003, Elsevier Science (USA). All rights reserved. Energy n Although energy can neither be created nor destroyed, it can change form. n Atoms contain energy. n The energy that holds the nucleus together is called nuclear-binding energy. n The energy holding electrons, negatively charged particles, in their shell is known as electron-binding energy. n Although energy can neither be created nor destroyed, it can change form. n Atoms contain energy. n The energy that holds the nucleus together is called nuclear-binding energy. n The energy holding electrons, negatively charged particles, in their shell is known as electron-binding energy.

9. Copyright 2003, Elsevier Science (USA). All rights reserved. Matter n Matter has many forms, including solids, liquids, and gases. n Matter is composed of atoms grouped together in specific arrangements called molecules. n A molecule is the smallest particle of substance that retains the property of the original substance. n The fundamental unit of matter for discussion in this chapter is the atom. n Matter has many forms, including solids, liquids, and gases. n Matter is composed of atoms grouped together in specific arrangements called molecules. n A molecule is the smallest particle of substance that retains the property of the original substance. n The fundamental unit of matter for discussion in this chapter is the atom.

10. Copyright 2003, Elsevier Science (USA). All rights reserved. Atomic Structure n The atom consists of two parts: a central nucleus orbiting electrons n An atom is identified by the composition of its nucleus and the arrangement of its orbiting electrons; at present, 105 different atoms exist. n The atom consists of two parts: a central nucleus orbiting electrons n An atom is identified by the composition of its nucleus and the arrangement of its orbiting electrons; at present, 105 different atoms exist.

11. Copyright 2003, Elsevier Science (USA). All rights reserved. n The arrangement within the atom is similar to that of the solar system. n The atom has a nucleus as its center or sun, and the electrons revolve (orbit) around it like planets. n The electrons remain stable in their orbit unless disturbed or moved. X-rays can disturb the orbiting electrons. n The arrangement within the atom is similar to that of the solar system. n The atom has a nucleus as its center or sun, and the electrons revolve (orbit) around it like planets. n The electrons remain stable in their orbit unless disturbed or moved. X-rays can disturb the orbiting electrons. Atomic Structure  cont’d

12. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-3 Diagrammatic representation of an oxygen atom. Fig 38-3

13. Copyright 2003, Elsevier Science (USA). All rights reserved. Nucleus n The nucleus, or dense core of the atom, is composed of particles known as protons and neutrons. n Protons carry positive electrical charges, whereas neutrons carry no electrical charge. n Dental x-rays do not affect the tightly bound nucleus of the atom and are only changed in direction or scattered. n Dental x-rays cannot make atoms radioactive; thus patients do not give off x-rays after the x-ray machine stops producing x-rays. n The nucleus, or dense core of the atom, is composed of particles known as protons and neutrons. n Protons carry positive electrical charges, whereas neutrons carry no electrical charge. n Dental x-rays do not affect the tightly bound nucleus of the atom and are only changed in direction or scattered. n Dental x-rays cannot make atoms radioactive; thus patients do not give off x-rays after the x-ray machine stops producing x-rays.

14. Copyright 2003, Elsevier Science (USA). All rights reserved. Electrons n Electrons are tiny negatively charged particles that have very little mass. n Electrons orbit around the nucleus of an atom. n The orbit path of an electron is called an electron shell. Each shell can contain only a specific number of electrons. n The electrons are maintained in orbit by electron- binding energy, a force similar to the force of gravity on earth. n Electrons are tiny negatively charged particles that have very little mass. n Electrons orbit around the nucleus of an atom. n The orbit path of an electron is called an electron shell. Each shell can contain only a specific number of electrons. n The electrons are maintained in orbit by electron- binding energy, a force similar to the force of gravity on earth.

15. Copyright 2003, Elsevier Science (USA). All rights reserved. Ionization n The electrons remain stable in their orbit 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.) n X-rays have enough energy to push electrons out of their orbits and produce ions (an atom that gains or loses an electron and becomes electrically unbalanced) in a process called ionization. n The electrons remain stable in their orbit 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.) n X-rays have enough energy to push electrons out of their orbits and produce ions (an atom that gains or loses an electron and becomes electrically unbalanced) in a process called ionization.

16. Copyright 2003, Elsevier Science (USA). All rights reserved. Ionization  cont’d n Ionization is the process by which electrons are removed from the orbital shells of electrically stable atoms through collisions with x-ray photons. n When an electron is removed from the atom, an ion pair results. n The harmful ionizing effect of x-rays in humans can result in a disruption of cellular metabolism and can cause permanent damage to living cells and tissues. n Ionization is the process by which electrons are removed from the orbital shells of electrically stable atoms through collisions with x-ray photons. n When an electron is removed from the atom, an ion pair results. n The harmful ionizing effect of x-rays in humans can result in a disruption of cellular metabolism and can cause permanent damage to living cells and tissues.

17. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-4 A molecule of water (H 2 0) consists of two atoms of hydrogen connected to one atom of oxygen. Fig. 38-4

18. Copyright 2003, Elsevier Science (USA). All rights reserved. Properties of X-Rays n The dental assistant must be familiar with the unique characteristics of x-rays. n 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. n Electromagnetic radiation is made up of photons that travel through space at the speed of light in a straight line with a wavelike motion. n The dental assistant must be familiar with the unique characteristics of x-rays. n 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. n Electromagnetic radiation is made up of photons that travel through space at the speed of light in a straight line with a wavelike motion.

19. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-5 Electromagnetic spectrum, showing the various wavelengths of commonly used radiations. Fig. 38-5

20. Copyright 2003, Elsevier Science (USA). All rights reserved. n The shorter the wavelength, the greater its energy. n Because of the high energy of short wavelengths, they are able to penetrate matter more easily than are longer wavelengths. n X-rays have unique properties that make them especially useful in dentistry. n The shorter the wavelength, the greater its energy. n Because of the high energy of short wavelengths, they are able to penetrate matter more easily than are longer wavelengths. n X-rays have unique properties that make them especially useful in dentistry. Properties of X-Rays  cont’d

21. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-6 A, Wavelength is the distance between the crest 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. Fig. 38-6 A & B

22. Copyright 2003, Elsevier Science (USA). All rights reserved. Components of the Dental X-Ray Machine n Dental x-ray machines may vary slightly in size and appearance, but all machines will have three primary components: The tubehead An extension arm The control panel n Dental x-ray machines may vary slightly in size and appearance, but all machines will have three primary components: The tubehead An extension arm The control panel

23. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-7 X-ray machine and arm. Fig. 38-7

24. Copyright 2003, Elsevier Science (USA). All rights reserved. The Tubehead n The x-ray tubehead is a tightly sealed; heavy metal housing that contains the x-ray tube that produces dental x-rays.

25. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-8 Diagram of the dental x-ray tubehead. Fig. 38-8

26. Copyright 2003, Elsevier Science (USA). All rights reserved. Components of the Tubehead n Metal housing is the metal body of the tubehead that houses the x-ray tube. It is filled with insulating oil. n Insulating oil surrounds the x-ray tube and prevents overheating by absorbing the heat created by the production of x-rays. n Tubehead seal is made of leaded glass or aluminum, it seals the oil in the tubehead. n X-ray tube is the heart of the x-ray-generating unit. n Metal housing is the metal body of the tubehead that houses the x-ray tube. It is filled with insulating oil. n Insulating oil surrounds the x-ray tube and prevents overheating by absorbing the heat created by the production of x-rays. n Tubehead seal is made of leaded glass or aluminum, it seals the oil in the tubehead. n X-ray tube is the heart of the x-ray-generating unit.

27. Copyright 2003, Elsevier Science (USA). All rights reserved. Components of the Tubehead  cont’d n Transformer alters the voltage of incoming electric current. n Aluminum filter is aluminum sheets of 0.5-mm thickness. n 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. n Position-indicating device (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. n Transformer alters the voltage of incoming electric current. n Aluminum filter is aluminum sheets of 0.5-mm thickness. n 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. n Position-indicating device (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.

28. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-10 A, Collimator. B, Filter. Fig. 38-10 A & B

29. Copyright 2003, Elsevier Science (USA). All rights reserved. X-Ray Tube n This vacuum environment allows the electrons to flow with minimum resistance between the electrodes: Cathode Anode n This vacuum environment allows the electrons to flow with minimum resistance between the electrodes: Cathode Anode

30. Copyright 2003, Elsevier Science (USA). All rights reserved. n Consists of a tungsten filament in a focusing cup made of molybdenum. n The purpose of the cathode is to supply the electrons necessary to generate x-rays. n Electrons are generated in the x-ray tube at the cathode. n The hotter the filament becomes, the more electrons are produced. n Consists of a tungsten filament in a focusing cup made of molybdenum. n The purpose of the cathode is to supply the electrons necessary to generate x-rays. n Electrons are generated in the x-ray tube at the cathode. n The hotter the filament becomes, the more electrons are produced. The Cathode

31. Copyright 2003, Elsevier Science (USA). All rights reserved. The Anode n The anode is the target for the electrons. n It is composed of a tungsten target (a small block of tungsten) that is embedded in the larger copper stem. n The copper around the target conducts the heat away from the target, thus reducing the wear and tear on the target. n The purpose of the tungsten target is to serve as a focal spot and convert the bombarding electrons into x-ray photons. n The x-rays at the center of this beam are known as the central ray. n The anode is the target for the electrons. n It is composed of a tungsten target (a small block of tungsten) that is embedded in the larger copper stem. n The copper around the target conducts the heat away from the target, thus reducing the wear and tear on the target. n The purpose of the tungsten target is to serve as a focal spot and convert the bombarding electrons into x-ray photons. n The x-rays at the center of this beam are known as the central ray.

32. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-12 The production of dental x-rays occurs in the x-ray tube. Fig. 38-12

33. Copyright 2003, Elsevier Science (USA). All rights reserved. Position-Indicating Device n The open end of the lead-lined position-indicating device (PID) is placed against the patient’s face during film exposure. n The PID may be cylindrical or rectangular. The rectangular PID limits the size of the beam to that of a dental film. n PIDs used in dentistry are usually 8, 12, or 16 inches long. n The length selected is determined by the radiographic technique being used. n 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. n The open end of the lead-lined position-indicating device (PID) is placed against the patient’s face during film exposure. n The PID may be cylindrical or rectangular. The rectangular PID limits the size of the beam to that of a dental film. n PIDs used in dentistry are usually 8, 12, or 16 inches long. n The length selected is determined by the radiographic technique being used. n 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.

34. Copyright 2003, Elsevier Science (USA). All rights reserved. Extension Arm n The extension arm encloses the wire between the tubehead to the control panel. n It also has an important function in positioning the tubehead. n The extension arm folds up and can be swiveled from side to side. n 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. n The extension arm encloses the wire between the tubehead to the control panel. n It also has an important function in positioning the tubehead. n The extension arm folds up and can be swiveled from side to side. n 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.

35. Copyright 2003, Elsevier Science (USA). All rights reserved. The Control Panel n The control panel of an x-ray unit contains: The master switch Indicator light Exposure button Indicator light Control devices (time, milliamperage [mA] selector, and kilovoltage [kV] selector) n A single centrally located control panel may be used to operate several tubeheads located in separate treatment rooms. n The control panel of an x-ray unit contains: The master switch Indicator light Exposure button Indicator light Control devices (time, milliamperage [mA] selector, and kilovoltage [kV] selector) n A single centrally located control panel may be used to operate several tubeheads located in separate treatment rooms.

36. Copyright 2003, Elsevier Science (USA). All rights reserved. How X-Rays Are Produced n The x-ray machine is plugged into the wall outlet, and when the machine is turned on, the electric current enters the control panel. n The current travels from the control panel to the tubehead through electrical wires in the extension arm. n The current travels through the step-down transformer to the filament of the cathode. n The filament circuit uses 3 to 5 volts to heat the tungsten filament in the cathode portion of the x-ray tube. n The heating of the filament results in thermionic emission. n The x-ray machine is plugged into the wall outlet, and when the machine is turned on, the electric current enters the control panel. n The current travels from the control panel to the tubehead through electrical wires in the extension arm. n The current travels through the step-down transformer to the filament of the cathode. n The filament circuit uses 3 to 5 volts to heat the tungsten filament in the cathode portion of the x-ray tube. n The heating of the filament results in thermionic emission.

37. Copyright 2003, Elsevier Science (USA). All rights reserved. How X-Rays Are Produced  cont’d n When the exposure button is pushed, the high-voltage circuit is activated. n The electrons in the cloud are accelerated across the x-ray tube to the anode. n The molybdenum cup in the cathode directs the electrons to the tungsten target in the anode. n The electrons travel from the cathode to the anode. n When the electrons strike the tungsten target, their energy of motion (kinetic energy) is converted to x-ray energy and heat. n When the exposure button is pushed, the high-voltage circuit is activated. n The electrons in the cloud are accelerated across the x-ray tube to the anode. n The molybdenum cup in the cathode directs the electrons to the tungsten target in the anode. n The electrons travel from the cathode to the anode. n When the electrons strike the tungsten target, their energy of motion (kinetic energy) is converted to x-ray energy and heat.

38. Copyright 2003, Elsevier Science (USA). All rights reserved. How X-Rays Are Produced  cont’d n Less than 1% of the energy is converted to x-rays; the remaining 99% are lost as heat. n The heat is carried away from the copper stem and absorbed by the insulating oil in the tubehead. n The x-rays travel through the unleaded glass window, the tubehead seal, and the aluminum filter. n The aluminum filter removes the longer-wavelength x- rays. n The x-ray beam travels through the collimator. n The x-ray beam then travels down the lead-lined PID and exits at the end of the PID. n Less than 1% of the energy is converted to x-rays; the remaining 99% are lost as heat. n The heat is carried away from the copper stem and absorbed by the insulating oil in the tubehead. n The x-rays travel through the unleaded glass window, the tubehead seal, and the aluminum filter. n The aluminum filter removes the longer-wavelength x- rays. n The x-ray beam travels through the collimator. n The x-ray beam then travels down the lead-lined PID and exits at the end of the PID.

39. Copyright 2003, Elsevier Science (USA). All rights reserved. Types of Radiation n Primary is the x-rays that come from the target of the x-ray tube. n Secondary is x-radiation that is created when the primary beam interacts with matter. n Scatter is a form of secondary radiation. It results when an x-ray beam has been deflected from its path by the interaction with matter. n Primary is the x-rays that come from the target of the x-ray tube. n Secondary is x-radiation that is created when the primary beam interacts with matter. n Scatter is a form of secondary radiation. It results when an x-ray beam has been deflected from its path by the interaction with matter.

40. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-13 Three types of radiation interaction with the patient. Fig. 38-13

41. Copyright 2003, Elsevier Science (USA). All rights reserved. Visual Characteristics n Contrast n Density n Image detail These qualities are necessary for a good radiograph. n The dental assistant must understand how variations in the character of the x-ray beam influence the quality of the resulting radiographs. n Contrast n Density n Image detail These qualities are necessary for a good radiograph. n The dental assistant must understand how variations in the character of the x-ray beam influence the quality of the resulting radiographs.

42. Copyright 2003, Elsevier Science (USA). All rights reserved. Radiolucent and Radiopaque n Radiolucent structures allow x-rays to pass through them. n The image of radiolucent structures appears dark or black on the radiograph. Air spaces, soft tissues of the body, and the dental pulp appear as radiolucent images. n Radiopaque structures do not allow x-rays to pass through them. n The image of radiopaque structures appears white or light gray on the radiograph. Metal, enamel, and dense areas of bone appear as radiopaque images. n Radiolucent structures allow x-rays to pass through them. n The image of radiolucent structures appears dark or black on the radiograph. Air spaces, soft tissues of the body, and the dental pulp appear as radiolucent images. n Radiopaque structures do not allow x-rays to pass through them. n The image of radiopaque structures appears white or light gray on the radiograph. Metal, enamel, and dense areas of bone appear as radiopaque images.

43. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-14 Radiolucent and radiopaque objects in a bitewing radiograph. Fig. 38-14

44. Copyright 2003, Elsevier Science (USA). All rights reserved. Contrast n 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. n Higher kilovoltage produces more penetrating x- rays and lower radiographic contrast. n A 90-kVp setting requires less exposure time and produces a radiograph that has low contrast (more shades of gray). n A 70-kVp setting requires a slightly longer exposure time and produces a radiograph with high contrast (fewer shades of gray). n 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. n Higher kilovoltage produces more penetrating x- rays and lower radiographic contrast. n A 90-kVp setting requires less exposure time and produces a radiograph that has low contrast (more shades of gray). n A 70-kVp setting requires a slightly longer exposure time and produces a radiograph with high contrast (fewer shades of gray).

45. Copyright 2003, Elsevier Science (USA). All rights reserved. Density n Density is the overall blackness or darkness of a film. n 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). n The degree of density is controlled by the mAs (milliampere seconds). n Density is the overall blackness or darkness of a film. n 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). n The degree of density is controlled by the mAs (milliampere seconds).

46. Copyright 2003, Elsevier Science (USA). All rights reserved. Other Factors Influencing Density n 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. n The developing time and temperature can affect the overall density. If the processing time is too long, the radiograph will appear dark. n The body size of the patient: A patient who is very small or thin would require less radiation than a husky, heavy-boned person. n 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. n The developing time and temperature can affect the overall density. If the processing time is too long, the radiograph will appear dark. n The body size of the patient: A patient who is very small or thin would require less radiation than a husky, heavy-boned person.

47. Copyright 2003, Elsevier Science (USA). All rights reserved. Geometric Characteristics n There are three geometric characteristics that affect the quality of the radiograph. These are: Sharpness Magnification Distortion n There are three geometric characteristics that affect the quality of the radiograph. These are: Sharpness Magnification Distortion

48. Copyright 2003, Elsevier Science (USA). All rights reserved. Sharpness n Sharpness refers to how well the radiograph reproduces the fine details or distinct outlines of an object. n Sharpness is sometimes referred to as detail, resolution, or definition. n The sharpness of an image is influenced by the following factors: Focal spot size Film composition Movement n Sharpness refers to how well the radiograph reproduces the fine details or distinct outlines of an object. n Sharpness is sometimes referred to as detail, resolution, or definition. n The sharpness of an image is influenced by the following factors: Focal spot size Film composition Movement

49. Copyright 2003, Elsevier Science (USA). All rights reserved. Radiation Safety n All ionizing radiations are harmful and produce biologic changes in living tissues. n The amount of x-radiation used in dental radiography is small; however, biologic changes do occur. n The dental assistant must understand how the harmful effects of radiation occur and how to discuss the risks of radiation with patients. n All ionizing radiations are harmful and produce biologic changes in living tissues. n The amount of x-radiation used in dental radiography is small; however, biologic changes do occur. n The dental assistant must understand how the harmful effects of radiation occur and how to discuss the risks of radiation with patients.

50. Copyright 2003, Elsevier Science (USA). All rights reserved. Ionization n Ionization is the harmful effect of x-rays in humans that can result in a disruption of cellular metabolism and cause permanent damage to living cells and tissues. n Ionization is the process by which electrons are removed from electrically stable atoms through collisions with x-ray photons. n The atoms that lose electrons become positive ions; as such, they are unstable structures capable of interacting with (and damaging) other atoms, tissues, or chemicals. n Ionization is the harmful effect of x-rays in humans that can result in a disruption of cellular metabolism and cause permanent damage to living cells and tissues. n Ionization is the process by which electrons are removed from electrically stable atoms through collisions with x-ray photons. n The atoms that lose electrons become positive ions; as such, they are unstable structures capable of interacting with (and damaging) other atoms, tissues, or chemicals.

51. Copyright 2003, Elsevier Science (USA). All rights reserved. Introduction to Physiology n Functional organization of the human body. The cell and its function. n Genetic control of protein synthesis. n Functional organization of the human body. The cell and its function. n Genetic control of protein synthesis.

52. Copyright 2003, Elsevier Science (USA). All rights reserved. Biologic Effects of Radiation n Exposure to radiation can bring about changes in body chemicals, cells, tissues, and organs. n The effects of the radiation may not become evident for many years after the time the x-rays were absorbed. n This time lag is called the latent period. n Exposure to radiation can bring about changes in body chemicals, cells, tissues, and organs. n The effects of the radiation may not become evident for many years after the time the x-rays were absorbed. n This time lag is called the latent period.

53. Copyright 2003, Elsevier Science (USA). All rights reserved. Cumulative Effects n Exposure to radiation has a cumulative effect over a lifetime. n When tissues are exposed to x-rays, some damage occurs. n Tissues have the capacity to repair some of the damage; however, the tissues do not return to their original state. n The cumulative effect of radiation exposure can be compared with cumulative effect from repeated exposure over the years to the rays of the sun. n Exposure to radiation has a cumulative effect over a lifetime. n When tissues are exposed to x-rays, some damage occurs. n Tissues have the capacity to repair some of the damage; however, the tissues do not return to their original state. n The cumulative effect of radiation exposure can be compared with cumulative effect from repeated exposure over the years to the rays of the sun.

54. Copyright 2003, Elsevier Science (USA). All rights reserved. Acute and Chronic Radiation Exposure n Acute radiation exposure occurs when a large dose of radiation is absorbed in a short period of time, such as in a nuclear accident. n Chronic radiation exposure occurs when small amounts of radiation are absorbed repeatedly over a long period of time. It may be years after the original exposure that the effects of chronic radiation exposure are observed. n Acute radiation exposure occurs when a large dose of radiation is absorbed in a short period of time, such as in a nuclear accident. n Chronic radiation exposure occurs when small amounts of radiation are absorbed repeatedly over a long period of time. It may be years after the original exposure that the effects of chronic radiation exposure are observed.

55. Copyright 2003, Elsevier Science (USA). All rights reserved. Genetic and Somatic Effects n X-rays effect 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. n All other cells in the body belong to the group 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. n X-rays effect 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. n All other cells in the body belong to the group 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.

56. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-16 Comparison of somatic and genetic effects of radiation. Fig. 38-16

57. Copyright 2003, Elsevier Science (USA). All rights reserved. Critical Organs n The following organs are considered critical organs: Skin Thyroid gland Lens of the eye Bone marrow n The following organs are considered critical organs: Skin Thyroid gland Lens of the eye Bone marrow

58. Copyright 2003, Elsevier Science (USA). All rights reserved. Radiation Measurements n Radiation can be measured in a manner similar to time, distance, and weight. n Two sets of systems are used to define the way in which radiation is measured. n The older system is referred to as the traditional or standard system. n The newer system is the metric equivalent known as the Systeme Internationale or SI. n Radiation can be measured in a manner similar to time, distance, and weight. n Two sets of systems are used to define the way in which radiation is measured. n The older system is referred to as the traditional or standard system. n The newer system is the metric equivalent known as the Systeme Internationale or SI.

59. Copyright 2003, Elsevier Science (USA). All rights reserved. Traditional Units of Radiation Measurement n The roentgen (R) The radiation absorbed dose (rad) The roentgen equivalent [in] man (rem) n The SI units include: Coulombs per kilogram (C/kg) The gray (Gy) The sievert (Sv) n The roentgen (R) The radiation absorbed dose (rad) The roentgen equivalent [in] man (rem) n The SI units include: Coulombs per kilogram (C/kg) The gray (Gy) The sievert (Sv)

60. Copyright 2003, Elsevier Science (USA). All rights reserved. Maximum Permissible Dose n The maximum permissible dose (MPD) of whole body radiation for those who are occupationally exposed to radiation is 5000 mrem (5.0 rem) per year, or 100 mrem per week. n This amount of radiation to the whole body produces very little chance of injury. n For nonoccupationally exposed persons, the current MPD is 500 mrem (5 mSv) per year. n Dental personnel should strive for an occupational dose of 0 by adhering to strict radiation protection practices. n The maximum permissible dose (MPD) of whole body radiation for those who are occupationally exposed to radiation is 5000 mrem (5.0 rem) per year, or 100 mrem per week. n This amount of radiation to the whole body produces very little chance of injury. n For nonoccupationally exposed persons, the current MPD is 500 mrem (5 mSv) per year. n Dental personnel should strive for an occupational dose of 0 by adhering to strict radiation protection practices.

61. Copyright 2003, Elsevier Science (USA). All rights reserved. Radiation Risks and Benefits n Background radiation comes from natural sources such as radioactive materials in the ground and cosmic radiation from space. n Exposure from medical or dental sources is an additional radiation risk. n 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. n Background radiation comes from natural sources such as radioactive materials in the ground and cosmic radiation from space. n Exposure from medical or dental sources is an additional radiation risk. n 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.

62. Copyright 2003, Elsevier Science (USA). All rights reserved. Responsibilities of the Dentist n To prescribe radiographs only for diagnostic purposes. n To ensure that all radiographic equipment is properly installed and maintained in a safe working condition. n To provide appropriate shielding to protect staff and patients from the effects of radiation. n To require that anyone exposing radiographs be properly trained and appropriately supervised while exposing radiographs. n To obey all state radiographic licensing requirements, rules, and regulations. n To participate in obtaining informed consent. n To prescribe radiographs only for diagnostic purposes. n To ensure that all radiographic equipment is properly installed and maintained in a safe working condition. n To provide appropriate shielding to protect staff and patients from the effects of radiation. n To require that anyone exposing radiographs be properly trained and appropriately supervised while exposing radiographs. n To obey all state radiographic licensing requirements, rules, and regulations. n To participate in obtaining informed consent.

63. Copyright 2003, Elsevier Science (USA). All rights reserved. Equipment for Radiation Protection n The dental tubehead must be equipped with appropriate: Aluminium filters Lead collimators Position-indicating devices (PID) n Equipment should be checked on a regular basis by state or federal regulating agencies. n Faulty or malfunctioning equipment should be repaired immediately. n The dental tubehead must be equipped with appropriate: Aluminium filters Lead collimators Position-indicating devices (PID) n Equipment should be checked on a regular basis by state or federal regulating agencies. n Faulty or malfunctioning equipment should be repaired immediately.

64. Copyright 2003, Elsevier Science (USA). All rights reserved. Aluminum Filter n The purpose of the aluminum filter is to remove the low energy, long wavelength, and least penetrating x-rays from the x-ray beam. n These x-rays are harmful to the patient and are not useful in producing a diagnostic-quality radiograph. n X-ray machines operating at 70 kVp or above must have aluminum filtration of 2.5 mm. This is a federal requirement. n The purpose of the aluminum filter is to remove the low energy, long wavelength, and least penetrating x-rays from the x-ray beam. n These x-rays are harmful to the patient and are not useful in producing a diagnostic-quality radiograph. n X-ray machines operating at 70 kVp or above must have aluminum filtration of 2.5 mm. This is a federal requirement.

65. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-17 The purpose of placing aluminum disks in the path of the beam is to filter out the low-energy, long wavelengths that are harmful to the patient. Fig. 38-17

66. Copyright 2003, Elsevier Science (USA). All rights reserved. Collimator n The collimator is used to restrict the size and shape of the x-ray beam in order to reduce patient exposure. n A collimator may have either a round or rectangular opening. n A rectangular collimator restricts the beam to an area slightly larger than a size 2 intraoral film and significantly reduces patient exposure. n The collimator is used to restrict the size and shape of the x-ray beam in order to reduce patient exposure. n A collimator may have either a round or rectangular opening. n A rectangular collimator restricts the beam to an area slightly larger than a size 2 intraoral film and significantly reduces patient exposure.

67. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-18 A, The beam produced by a circular collimator is 2.75 inches in diameter. B, The beam produced by a rectangular collimator is just slightly larger than a size 2 intraoral film. Fig. 38-18 A & B

68. Copyright 2003, Elsevier Science (USA). All rights reserved. Position Indicating Device n The position-indicating device (PID) appears as an extension of the x-ray tubehead. n It is used to direct the x-ray beam. Round and rectangular shaped PIDs are available in two lengths: short (8-inch) long (16-inch) n The position-indicating device (PID) appears as an extension of the x-ray tubehead. n It is used to direct the x-ray beam. Round and rectangular shaped PIDs are available in two lengths: short (8-inch) long (16-inch)

69. Copyright 2003, Elsevier Science (USA). All rights reserved. Patient Protection n Lead apron and thyroid collar A lead apron and a 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. n The lead apron should cover the patient from the neck and extend over the lap area to protect the reproductive and blood-forming tissues from scatter radiation. n Many states mandate the use of a lead apron. n Lead apron and thyroid collar A lead apron and a 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. n The lead apron should cover the patient from the neck and extend over the lap area to protect the reproductive and blood-forming tissues from scatter radiation. n Many states mandate the use of a lead apron.

70. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-19 The lead apron and thyroid collar must be large enough to cover the seated patient. Fig. 38-19

71. Copyright 2003, Elsevier Science (USA). All rights reserved. Fast-Speed Film n The size of the silver bromide crystals is the main factor in determining the film speed: the larger the crystals, the faster the film. n A fast film requires less exposure to produce a quality radiograph. n Fast-speed film is the single most effective method of reducing a patient’s exposure to x-radiation. n Fast-speed film is available for both intraoral and extraoral radiography. n The size of the silver bromide crystals is the main factor in determining the film speed: the larger the crystals, the faster the film. n A fast film requires less exposure to produce a quality radiograph. n Fast-speed film is the single most effective method of reducing a patient’s exposure to x-radiation. n Fast-speed film is available for both intraoral and extraoral radiography.

72. Copyright 2003, Elsevier Science (USA). All rights reserved. Film-Holding Devices n The use of a film-holding instrument keeps the patient’s hands and fingers from being exposed to x-radiation. n Film holders also hold the film in a stable position and aid the operator in properly positioning the film and the PID. n The use of a film-holding instrument keeps the patient’s hands and fingers from being exposed to x-radiation. n Film holders also hold the film in a stable position and aid the operator in properly positioning the film and the PID.

73. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-20 The patient’s fingers are unnecessarily exposed to radiation when film holders are not used. Fig. 38-20

74. Copyright 2003, Elsevier Science (USA). All rights reserved. Exposure Factors n Using the proper exposure factors also limits the amount of x-radiation exposure to the patient. n Adjusting the kilovoltage peak, milliamperage, and time settings controls the exposure factors. n A setting of 70 to 90 kVp keeps patient exposure to a minimum. n On some dental units, the kilovoltage peak and milliamperage settings are preset by the manufacturer and cannot be adjusted. n Using the proper exposure factors also limits the amount of x-radiation exposure to the patient. n Adjusting the kilovoltage peak, milliamperage, and time settings controls the exposure factors. n A setting of 70 to 90 kVp keeps patient exposure to a minimum. n On some dental units, the kilovoltage peak and milliamperage settings are preset by the manufacturer and cannot be adjusted.

75. Copyright 2003, Elsevier Science (USA). All rights reserved. Proper Techniques n Proper techniques are necessary to ensure the diagnostic quality of films and reduce the amount of exposure to a patient. n Films that are nondiagnostic must be retaken; this results in additional radiation exposure to the patient. n Retakes are a major cause of unnecessary radiation to patients and must be avoided. n Proper techniques are necessary to ensure the diagnostic quality of films and reduce the amount of exposure to a patient. n Films that are nondiagnostic must be retaken; this results in additional radiation exposure to the patient. n Retakes are a major cause of unnecessary radiation to patients and must be avoided.

76. Copyright 2003, Elsevier Science (USA). All rights reserved. X-Rays During Pregnancy n 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.” n When a lead apron is used during dental radiographic procedures, the amount of radiation received in the pelvic region is nearly zero. n There is no detectable exposure to the embryo or fetus with the use of a lead apron. n 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.” n When a lead apron is used during dental radiographic procedures, the amount of radiation received in the pelvic region is nearly zero. n There is no detectable exposure to the embryo or fetus with the use of a lead apron.

77. Copyright 2003, Elsevier Science (USA). All rights reserved. Operator Protection n A dental assistant who fails to follow the rules of radiation protection may suffer the results of chronic radiation exposure. n By following these rules, dental personnel can keep their radiation exposure to zero. n A dental assistant who fails to follow the rules of radiation protection may suffer the results of chronic radiation exposure. n By following these rules, dental personnel can keep their radiation exposure to zero.

78. Copyright 2003, Elsevier Science (USA). All rights reserved. Rules for Operator Protection n Never stand in the direct line of the primary beam. n Always stand behind a lead barrier if one is available or a proper thickness of drywall. n If a lead barrier is not available, stand at right angles to the beam. n Never stand closer than 6 feet to the x-ray unit during an exposure unless you are behind a barrier. n Never stand in the direct line of the primary beam. n Always stand behind a lead barrier if one is available or a proper thickness of drywall. n If a lead barrier is not available, stand at right angles to the beam. n Never stand closer than 6 feet to the x-ray unit during an exposure unless you are behind a barrier.

79. Copyright 2003, Elsevier Science (USA). All rights reserved. Personnel Monitoring n There are 3 types of monitoring devices used to determine the amount of radiation exposure to personnel: Film badge Pocket dosimeter (pen style) Thermoluminescent (TLD) n There are 3 types of monitoring devices used to determine the amount of radiation exposure to personnel: Film badge Pocket dosimeter (pen style) Thermoluminescent (TLD)

80. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-22 A film badge is used to monitor the amount of radiation that reaches the dental radiographer. Fig. 38-22

81. Copyright 2003, Elsevier Science (USA). All rights reserved. Equipment Monitoring n Dental x-ray machines must be monitored for leakage radiation. n If a dental x-ray tubehead has a faulty tubehead seal, leakage radiation results. n 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. n Dental x-ray machines must be monitored for leakage radiation. n If a dental x-ray tubehead has a faulty tubehead seal, leakage radiation results. n 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.

82. Copyright 2003, Elsevier Science (USA). All rights reserved. If the Patient Cannot Cooperate n If the patient is a child who is unable to cooperate, the child 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.

83. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-23 Child sitting on parent’s lap for dental x-ray. Fig. 38-23

84. Copyright 2003, Elsevier Science (USA). All rights reserved. ALARA Concept n The ALARA concept states that all exposure to radiation must be kept to a minimum, or “as low as reasonably achievable.” n Every possible method of reducing exposure to radiation should be used to minimize risk. n The radiation protection measures detailed in this chapter should be used to minimize patient, operator, and staff exposure, thus keeping radiation exposure “as low as reasonably achievable.” n The ALARA concept states that all exposure to radiation must be kept to a minimum, or “as low as reasonably achievable.” n Every possible method of reducing exposure to radiation should be used to minimize risk. n The radiation protection measures detailed in this chapter should be used to minimize patient, operator, and staff exposure, thus keeping radiation exposure “as low as reasonably achievable.”

85. Copyright 2003, Elsevier Science (USA). All rights reserved. Patient Questions n Patients often have questions and concerns about radiation. n As a dental assistant you must be prepared to answer their questions and educate the dental patient about the importance of radiographs. n Patients often have questions and concerns about radiation. n As a dental assistant you must be prepared to answer their questions and educate the dental patient about the importance of radiographs.

86. Copyright 2003, Elsevier Science (USA). All rights reserved. Patient Questions  cont’d n Listed below are some examples of comments you can make to patients during informal discussions. “The doctor orders x-rays based on 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?” n Listed below are some examples of comments you can make to patients during informal discussions. “The doctor orders x-rays based on 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?”

87. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-21 Operator protection guidelines suggests that the dental radiographer stand at an angle of 90˚ to 135˚ to the primary beam. Fig. 38-21

88. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-15 A, A film produced with lower kilovoltage exhibits high contrast; many light and dark areas are seen as demonstrated by the use of a stepwedge. Fig. 38-15 A

89. Copyright 2003, Elsevier Science (USA). All rights reserved. Fig. 38-15 B, A film produced with higher kilovoltage exhibits low contrast; many shades of gray are seen instead of black and white. Fig. 38-15 B