Radiology Exam 1

Front 1

Radiographic Interpretation

Back 1

explanation of what is viewed on a dental radiograph

Front 2

Radiographic Diagnisis

Back 2

is the responsibility of the dentist to provide a diagnosis based on a radiograph.

Dental Hygienists can provide a preliminary Radiographic Diagnosis

Front 3

Radiation

Back 3

A form of energy carried by waves/particles

Front 4

X-Radiation

Back 4

A high energy radiation produced when electrons collide with a metal

Front 5

X-Ray

Back 5

A beam of energy capable of penetrating objects and produces image shadows on photographic film

Front 6

Radiology

Back 6

The study of radiation as used in medicine

Front 7

Radiography

Back 7

The art and science of making radiographs by the exposure of film to x-rays

Front 8

Radiograph

Back 8

A picture produced by the passage of x-rays through and object or body

Front 9

Dental Radiograph

Back 9

A photographic image of teeth and the periodontium

Front 10

Dental Radiographer

Back 10

Any person who exposes and processes dental x-ray film

Front 11

What is the importance of dental radiographs?

Back 11

Detect pathology: lesions, diseases, and conditions of the teeth that you cannot see clinically
Confirm and classify disease
Localized foreign objects
Provide necessary information for treatment
Evaluate growth and development
Evaluate changes in disease states

Front 12

Wilhelm Roentgen

Back 12

Discovered x-rays on November 8th, 1895

Front 13

Otto Walkoff D.D.S., M.D
(1896)

Back 13

Exposed the first dental x-ray in germany

Front 14

C.E. Kells
(1896)

Back 14

First in US to expose radiograph on a living person. First person to develop a practical use of radiography in dentistry.

Also developed the paralleling Technique

Front 15

Williams Rollins
(1901)

Back 15

Boston dentist known as "the father of science of radiation protection"

Front 16

William Coolidge
(1918)

Back 16

Developed the first dental x-ray tube that contained tungsten filament

Front 17

Victor CDX
(1923)

Back 17

First dental X-ray machine

Front 18

1987

Back 18

Introduction of the intraoral digital radiography

Front 19

Eastman Kodak Company
(1913)

Back 19

Developed the first pre-wrapped dental film

Front 20

1955

Back 20

Introduction of D-Speed Film

Front 21

1981

Back 21

Introduction of E-speed film

Front 22

Weston Price
(1904)

Back 22

Bisecting Technique (no longer acceptable technique)

Front 23

Howard Raper
(1925)

Back 23

Bitewing Technique

Front 24

1948

Back 24

Panoramic Radiography

Front 25

What are the subatomic particles that make up the atom (and their charges)?

Back 25

Nucleus: Proton (+) Neutron (no charge)

Orbits: Electron (-)

Front 26

How many shells are there surrounding an atom and what are they named?

Back 26

There are 7 shells; K,L,M,N,O,P,Q

Front 27

Which shell surrounding an atom has the highest energy level / binding force?

Back 27

K shell because it is the closest to the nucleus

Front 28

Electrostatic Force

Back 28

Electrons are maintained on their orbits via binding energy which is caused by and attraction between the positive nucleus and negative electrons

Front 29

What determines the binding energy?

Back 29

The distance between the nucleus and the orbiting electrons

Front 30

Removal of Electron from a Shell

Back 30

Great amount of energy is needed and needs to exceed the binding energy

Front 31

Ionization

Back 31

when a neutral atom acquires either a positive or negative charge

Front 32

Ion

Back 32

an atom that is not electrically balanced

Front 33

Ion pair

Back 33

When one atom loses an electron and another gains an electron they become attracted to each other to become balanced

Front 34

Radiation

Back 34

Emission of energy through space in the form of waves or stream of particles

Front 35

Radioactivity

Back 35

atoms or elements undergo spontaneous decay to become more stable

Front 36

Ionizing Radiation

Back 36

ability of an x-ray photon to produce ions from an atom

Front 37

Particulate Radiation

Back 37

Particles have both mass and energy
Travels in straight lines at high speeds from their sources
Some particles have positive, negative, or neutral charges

Front 38

Four types of Particulate Radiation

Back 38

Electrons (Beta Particles / Cathode Rays)
Alpha: Heavy metals
Protons
Neutrons

Front 39

Beta Particles

Back 39

Fast moving electrons emitted from the nucleus of a radioactive atom

Front 40

Cathode Rays

Back 40

Streams of electrons that originate in an x-ray tube

Front 41

Electromagnetic Characteristics

Back 41

- Bundles of energy that do not have mass, weight, or charge
- Travel the speed of light
- Interact with biologic tissue causing changes in the tissue because of ionization. However can be non-ionizing

Travel as both a particle and a wave

Front 42

Electromagnetic Spectrum:

Back 42

- Arranged from the longest wavelength (ac power)
- To the shortest wavelength (x-rays)
- Largest source of daily radiation from the electromagnetic spectrum is from natural sources. It makes up about 56% of radiation exposure
- 41% of radiation exposure comes from artificial radiation

Front 43

Particle Concepts

Back 43

- Photons and quantum: terms used to designate a single unit or bundle of energy
○ No mass
○ No weight
○ Travels in waves
○ Travels at the speed of light
○ Travels in a straight line

Front 44

Three Properties of Wave Concept

Back 44

○ Velocity
○ Wavelength
○ Frequency

Front 45

Velocity

Back 45

Speed

Front 46

Wavelength

Back 46

- distance from one crest of a wave to the next crest (determines the energy and the penetration of radiation)

Front 47

Frequency

Back 47

- number of crests passing a particular point per unit of time (measured in hertz (Hz))

Front 48

Long Wavelengths

Back 48

○ Low frequency
○ Low energy
○ Lower ability to penetrate matter

Front 49

Short Wavelengths

Back 49

○ High frequency
○ High energy
○ Greater ability to penetrate matter

Front 50

Relationship Between Wavelength and Frequency:

Back 50

- Wavelength and frequency are inversely related

Front 51

What are Dental X-rays?

Back 51

- Electromagnetic radiation.
- Weightless packages of energy (photon/quantum) that have no charges that travel in waves.
- Wavelength and frequency will determine the amount of energy it has, thus it's penetrating ability

Front 52

Properties of X-rays:

Back 52

- Invisible, weightless, cannot be heard, smelled, felt, seen, or tasted
- No mass
- No charge
- Travel the speed of light (186,000 miles/second)
- Travel in a straight line
- Can be deflected
- Have a wide range of wavelengths
- Scattered- stray outward over a distance
- Cannot be focused (act like a flashlight)
- Penetrate materials that absorb or reflect light
- Absorb matter differently (produces a negative image on film)
- Cause specific objects to fluoresce
- Cause biologic changes
- Ionize gases

Front 53

The X-ray Machine Component Parts:

Back 53

- Control panel-
○ On-off switch
○ Sets the: time, kilovoltage, and milliamperage
- Extension arm-

Allows movement and positioning of the tubehead

Front 54

Tubehead:

Back 54

tightly sealed component which contains the x-ray tube that produces dental x-rays

Front 55

Metal housing:

Back 55

lead lined metal casing to prevent excessive radiation exposure

Front 56

Insulating oil and copper tube:

Back 56

cooling system

Front 57

Tubehead seal:

Back 57

aluminum or leaded glass. Seal the oil and filters x-ray beam

Front 58

x-ray tube:

Back 58

Vacuum that houses the cathode (-) and anode (+)

Front 59

Transformer:

Back 59

Alters the voltage

Front 60

Aluminum disk:

Back 60

Filters out non-penetrating longer x-rays

Front 61

Lead collimator:

Back 61

Restricts the size of the x-ray beam

Front 62

Position-indication device (PID):

Back 62

Open-ended lead lined cylinder that aims and shapes the x-ray beam

Front 63

X-ray Tube:

Back 63

- Leaded glass housing
- Glass vacuum tube that houses the cathode and anode
○ Cathode (negative charge)
○ Anode (positive charge)
- Lead lined: prevents x-rays from escaping in all directions
- Has a window that permits x-rays to exit

Front 64

Cathode (-)

Back 64

○ Negative electrode
○ Purpose: produces electrons for the generation of x-rays
○ Tungsten filament: coil wire produces electrons
○ Focusing cup (molybdenum cup): focuses the electrons into a narrow beam and directs the beam to the anode

Front 65

Anode (+)

Back 65

○ Positive electrode
○ Purpose: converts electrons into x-rays
○ Tungsten target: has a focal spot that converts electrons to x-rays
○ Copper stem: dissipates heat from the target

Front 66

Anode's Focal Spot:

Back 66

- Focal spot is the area on the tungsten target that the electrons strike to generate x-rays
- The smaller the focal spot, the sharper the image
- The focal spot is placed at an angle of 15-20degrees to improve the image of radiograph

Front 67

X-ray Generating Apparatus:

Back 67

- Electricity and electrical currents
- Circuits
- Transformers

Front 68

Electricity:

Back 68

Electricity is the energy used to make x-rays

Front 69

Direct current (DC):

Back 69

electrons flow in one direction

Front 70

Alternating Current (AC):

Back 70

electrons flow in two opposite directions

Front 71

Refraction

Back 71

conversion of AC to DC
○ Used in dental x-rays
○ Ensure electrons are always moving from cathode to anode
○ Reduces patient exposure by 20%
○ Homogeneous: produces more uniform wavelength

Front 72

Amperage/milliampere (mA):

Back 72

s the measurement of the number/amount of electrons through a conductor
○ Affects the amount of electrons being produced at the cathode
○ The higher the (mA)the greater the amount of electrons are produced
○ Therefore mA controls the quantity of radiation***

Front 73

Voltage/Kilovoltage (kVp):

Back 73

is the measurement of force or speed of electrons as they travel from the cathode to the anode
○ The higher the kVp the faster the electrons move from cathode to anode
○ kVp controls the quality and penetrating ability of the x-ray***

Front 74

Low voltage:

Back 74

Regulates the volts (3-5 volts) to the cathode (produces the numbers of electrons)and is controlled by the mA

Front 75

High Voltage:

Back 75

Provides the energy (65,000-100,000 volts) to accelerate the electrons from the cathode to anode and is regulated by the kVp

Front 76

Transformer:

Back 76

Mechanism used in an electrical circuit to increase or decrease the voltage

Front 77

Step-down transformer (110-220 volts --> 3-5 volts)

Back 77

Heat the tungsten filament--> electrons
Associated with the cathode
Associated with the mA

Front 78

Step-up transformer (110-220 volts --> 65,000-100,000 volts)

Back 78

Provides energy to propel electrons from cathode to anode

Associated with kVp

Front 79

Four conditions needed to produce x-rays:

Back 79

○ Source of electrons
○ Focusing of electrons
○ Motion: high voltage potential to move electrons
○ Target that creates a sudden stop of electrons

Front 80

Production of Dental X-rays STEP 1:

Back 80

Source of electrons
○ Step-down transformer (controlled by the mA) heats the tungsten filament to produce electrons
○ The release of the electrons from the filament is called thermionic emission

Front 81

Production of Dental X-rays STEP 2 &3:

Back 81

Motion
○ Step-up transformer is activated when the exposure button is pushed (controlled by the kVp)
○ This propels the electrons from the cathode to the anode
○ The focusing cup directs the electrons to the tungsten target (anode)

Front 82

Production of Dental X-rays STEP 4:

Back 82

Sudden Stop
○ Electrons strike the tungsten target (anode) and this energy (kinetic) is converted into energy and heat

Front 83

Energy Produced from an X-ray Machine:

Back 83

~1% x-rays (diagnostic levels)
~99% heat
To dissipate the heat, the copper stem and the tubehead is encased with oil

Front 84

How are x-rays produced:

Back 84

Through the unleaded glass window --> tubehead seal --> aluminum disks (filters out longer wavelengths) --> lead collimator (restrict size) --> PID --> through the patient --> radiographic film

Front 85

Conversion of electrons to x-ray photons:

Back 85

- Not all x-rays produced are the same.
- Two mechanisms:
○ General (Bremsstrahlung) radiation
70% of radiation produced
○ Characteristic radiation
30% of radiation produced

Front 86

General Radiation:

Back 86

- Breaking radiation
- Electron comes close (most of the time) and hits the nucleus
- Electron is slowed down --> energy

Energy --> wavelengths of different energies

Front 87

Characteristic Radiation:

Back 87

- Inner electron is dislodged (K shell)
- Rearrangement of electrons --> energy
- Occurs at 70 kVp (with high speed electrons)

Front 88

Primary Radiation (Aka primary beam / useful beam

Back 88

x-ray beam produced at the target of the anode and exits the tubehead

Front 89

Secondary Radiation

Back 89

Primary beam interacts with matter
Less penetrating than primary

Front 90

Scatter Radiation

Back 90

Form of secondary radiation that is deflected from it's path by the interaction with matter
Deflected in all directions: detrimental to the patient and radiographer
May cause film fog

Front 91

Interaction of Radiation with Matter:

Back 91

1) X-rays transmitted to film without interaction
2) X-rays are absorbed completely by photoelectric effects
3) X-rays are scattered by Compton Interaction

Front 92

No Interaction of X-rays Photons:

Back 92

- X-ray photon can pass through an atom, unchanged
- Creates densities on the x-ray film (produces image)

Front 93

Complete Absorption of X-ray Photons:

Back 93

- Creates an ion pair

Front 94

Absorption:

Back 94

total transfer of energy of the x-ray photon to the atom--> PHOTOELECTRIC EFFECT

Front 95

Compton Scatter:

Back 95

- A high energy x-ray photon collides with a loosely bound outer shell electrons --> ejects the electron from it's orbit (ionization)
- The x-ray photon is scattered:
○ At a lower energy level
- Weaker x-ray photon continues to scatter until it give up all it's energy
- Majority of scatter radiation in dental radiography
○ 62% of radiation effect at the molecular level
- Likely to reach the film
○ Can create film fog

Front 96

Coherent Scatter:

Back 96

- Also called unmodified
- When a low-energy x-ray interacts with matter and the x-rays undergo a change in direction without a change in wavelength
- No loss of energy occurs
- No change in the atom
- No ionization occurs
- Not of significance in dental radiography
- 8% of radiation effect at a molecular level

Front 97

Radiation Characteristics Include:

Back 97

• Quality- (kVp)
• Quantity- (mA)
• Intensity- (kVp & mA)

Front 98

X-ray Beam Quality

Back 98

used to describe the mean energy or penetrating ability of the x-ray beam.
• Wavelength-
• Longer- less penetrating- more likely to be absorbed by matter
• Shorter more penetrating ability
• Controlled by kVp

Front 99

Kilovoltage: kVp

Back 99

• Dental radiography-
• Uses 65-100kVp
• <65 kVp- longer wavelength
§ Not adequate penetration
§ Detrimental to patient
• >100 kVp- shorter wavelength
§ Over penetration
• Want to operate at 85-100 kVp
§ Penetrating
§ Shorter wavelengths
§ Greater energy
• Regardless of the kVp setting: Heterogeneous wavelengths
§ Have different energies and wavelengths- polychromatic
• When you increase kVp: increase the penetrating ability of the x-ray beam.

Front 100

kVp =

Back 100

quality of the film

Front 101

Operating Kilovoltage Peak (kVp) Density:

Back 101

• Increase kVp (increase penetrating power) = increase Density of the film (more dark)
• Decrease kVp (decrease penetrating power) = decrease Density of the film (more light)

Front 102

Moderate density

Back 102

produces shades of gray

Front 103

Operating Kilovoltage Peak (kVp): Contrast

Back 103

• Low kVp (60-->70) --> High contrast film
• Many areas of black and white (dental carries)
• High kVp (> or = 90) Low contrast film
• Many shades of gray (periodontal disease)
• Best film is a compromise between high contrast and low contrast

Front 104

Exposure Time:

Back 104

interval of time during which x-rays are produced
• Measured in impulses
• x-rays are created in a series of bursts (not a continuous stream)
• One impulse occurs every 1/60th of a second
• 60 impulses in one second
• To compensate for the penetrating power of the x-ray beam an adjustment in exposure time requires and adjustment in kVp
• Increase exposure time: darker film

Decrease exposure time: lighter film

Front 105

Kilovoltage Peak Rule:

Back 105

• Maximum or peak voltage
• Measured in kilovolts
• Guideline for alternating kVp and exposure time
• Increased kVp by 15- decrease exposure time by 1/2
• Decrease kVp by 15- increase exposure time x2

Front 106

X-ray Beam Quantity:

Back 106

the number of x-rays produced
• Controlled by milliamperage (mA)
• mA:
• Regulates the temperature of the cathode filament
• Increase in temperature results in an increase in the number of electrons produced
• Increase in number of electrons increases the number of x-rays emitted from the tube

Front 107

Milliampere-Seconds (mAs):

Back 107

• Product of milliamperes and exposure time is mAs
• (mA)(exposure time {sec})= mAs
• If milliamperage is increased the exposure time must be decreased and vice versa if the density is to remain the same

Front 108

Exposure Time: mA Example

Back 108

• Inversely related:
• Increase mA --> decrease exposure time
• Decrease mA --> increase exposure time

Front 109

Operating mA: Density

Back 109

• Increase mA (increase amount of electrons) = increase in density (darker film)

Decrease mA (decrease amount of electrons) = decrease in density (lighter film)

Front 110

mA =

Back 110

quantity of x-rays produced

Front 111

X-ray Beam Intensity:

Back 111

• Intensity = quantity and quality of x-ray photons per unit of area per unit of exposure time
• Intensity= (quantity)(quality)/ (unit of area) (unit of time)
• Affected by:
§ Milliamperage
§ Kilovoltage
§ Exposure time
§ Distance

Front 112

Intensity and kVp:

Back 112

Increase kVp: increase energy, shorter wavelength = increase intensity of x-ray beam

Front 113

Intensity and mA:

Back 113

• Increase mA: increase amount of electrons = more energy = increase intensity of x-ray beam

Front 114

Intensity and Exposure Time:

Back 114

• Exposure time affects the number of x-rays produced.
• Longer Exposure time = increased intensity of x-ray beam

Front 115

Intensity and Distance:

Back 115

• Distance traveled will affect the intensity of the beam
• Intensity of the beam is reduced as distance increases

As the beam travels away from the tubehead it diverges to cover a large area (flashlight)

Front 116

Inverse Square Law:

Back 116

• The relationship between intensity and distance
• States: the intensity of radiation is inversely proportional to the square of the distance from the source of radiation

Front 117

Half Value Layer (HVL):

Back 117

• To reduced the intensity of an x-ray beam, aluminum filters are placed in the path of the beam inside the tubehead
• Remove longer, low energy wavelengths; less penetrating x-rays
• The thickness of aluminum (filters) placed in the path of the x-ray beam that decreases the intensity of the beam by 1/2 is the HVL
• HVL: if the thickens of a 4mm of a material is placed in the path of the beam, and the intensity is reduced by one-half, the HVL of the x-ray beam is 4mm
• Measures HVL; determines the penetrating quality of the beam
• Measured in mm
• The higher the HVL the more penetrating the beam

Front 118

Radiation Biology-

Back 118

the study of the effects of ionizing radiation on living tissue to understand the harmful effects of radiation

Front 119

X-radiation Exposures are Studied:

Back 119

• Survivors of the atomic bomb
• Chernobyl survivors

Patients undergoing radiation therapy

Front 120

Radiation Injury Factors:

Back 120

○ Total dose
○ Type of radiation
○ Dose rate
○ Amount of tissue irradiated
○ Cell sensitivity
○ Age

Front 121

Mechanisms of Radiation Injury:

Back 121

Ionization & free radical formation

Front 122

Ionization

Back 122

formation of an ion pair
§ A positive atom and a dislodged negative electron
§ Ionization
§ Excitation
§ Break bonds

Front 123

Free radical formation

Back 123

x-ray interacts with tissue
§ Produces free radicals when photons interact with water
§ Free radicals are formed:
□ Hydrogen radical
□ Oxygen radical
□ Hydroxyl radical
□ Hydroperoxyl radical (HO2) (toxic to cell)
§ Reformation of these molecules can form:
□ Hydrogen peroxide (toxic to cell) H202
□ Water

Front 124

Theories of Radiation Injury:

Back 124

Direct theory & indirect theory

Front 125

The direct theory of radiation injury

Back 125

§ Cell damage results when the ionizing radiation directly hits critical areas within the cell (strike DNA, RNA, etc)
§ Results: critical damage to the cell
§ Rarely happens

Front 126

Indirect Theory of radiation injury

Back 126

§ x-ray photons are absorbed within the cell and cause the formation of toxins (free radicals) which cause injury to the cell.
§ Indirect injuries are great because cells are composed of 70-80% water

Front 127

Dose Response Curve and Radiation Injury:

Back 127

• Used to study populations that have been exposed to large amounts of radiation

Front 128

Linear Curve-

Back 128

Curve indicates that a response is proportional to the dose

Front 129

Threshold Curve-

Back 129

§ Curve indicates that below a certain level (threshold) no response is seen
§ *there is never a point where there is no response

Front 130

Linear Non-threshold Curve-

Back 130

§ Indicates that a response is seen at any dose: no matter how small the amount of radiation received. Some biologic damage always occurs
§ This is the curve seen in dental radiography

Front 131

Stochastic-

Back 131

direct function of dose
• No threshold dose
• Severity of does dose not depend on the magnitude of absorbed dose

Front 132

Non-stochastic-

Back 132

• Somatic effect
• Has a threshold that increases with absorbed dose
• Require longer doses to cause serious impairment

Front 133

Radiation Injury Sequence, Repair and Accumulation

Back 133

Latent period
Period of injury
Period of repair

Front 134

Latent period

Back 134

time that elapses between exposure to radiation and the observable clinical signs

Front 135

Period of injury

Back 135

injuries of the cell include
§ Cell death
§ Changes in cell function
§ Breaking or clumping of chromosomes
§ Cessation of mitotic activity
§ Abnormal mitotic activity

Front 136

Period of repair-

Back 136

§ Not all cellular injuries are permanent
§ Most low-level dosage (i.e. dental x-rays) exposure injuries are followed by repair within the cell

Front 137

Cumulative Effects:

Back 137

• Effects of radiation is additive and damage that remains unrepaired accumulates in the tissues
• Repeated exposure can lead to health problems
○ Cancer
○ Cataracts
○ Etc.

Front 138

Determining Factors for Radiation Injury:

Back 138

Total dose
Dose rate
cell sensitivity
age
amount of tissue irradiated

Front 139

Total dose:

Back 139

total amount of radiation energy absorbed

Front 140

Does rate

Back 140

rate at which exposure to radiation occurs.
§ Increase in dose rates = increased damage
§ Does not allow time for repair

Front 141

Radiation Effects:

Back 141

Short-term and long-term effects
Somatic and genetic effects

Front 142

Short-term effects:

Back 142

following latent period, seen within minutes, days, or weeks
§ Associated with large amount of radiation (nuclear accident)
§ Acute radiation syndrome (ARS): nausea, vomiting, diarrhea, hair loss, and hemorrhage.

Front 143

Long-term effects:

Back 143

associated with low levels of radiation, repeated over a long period of time. Appear after years, decades, generations
§ Cancer, birth abnormalities, and genetic disorders

Front 144

Somatic

Back 144

all cells in the body except reproductive cells
§ Changes in somatic cells that produce poor health
§ The changes are not transmitted to future generations
§ Typical changes seen are: cancer, leukemia, and cataracts.
§ Somatic effects are seen in the person irradiated

Front 145

Genetic cells:

Back 145

reproductive cells
§ Ova and sperm
§ Not seen in the person irradiated but are passed on to future generations.
§ Genetic damage can not be repaired

Front 146

Radiosensitive cell:

Back 146

cell that is sensitive to radiation
§ Small lymphocyte / reproductive are the MOST radiosensitive

Front 147

Radioresistant cell:

Back 147

cell that is resistant to radiation
§ Nervous tissue is the most radio resistant

Front 148

Cellular response to radiation:

Back 148

§ Depends on
□ Mitotic activity: increased rate = increased sensitivity
□ Cell differentiation: immature cells / not highly specialized = increased sensitivity
□ Cell metabolism: increased metabolism = increased sensitivity

Front 149

Critical organs:

Back 149

§ A critical organ is an organ that, if damaged, diminishes the quality of a person's life
§ In dentistry the critical organs are (these are the organs that are exposed when taking dental radiographs):
□ Skin
□ Thyroid gland
□ Lens of the eye
□ Bone marrow

Front 150

Radiation Measurements:

Back 150

• Radiation is measured in the following ways determined by the ICRU
• Units for three quantities of measurement:
○ Exposure
§ The measurement of ionization in air produced by x-rays
○ Absorbed dose
§ Amount of radiation absorbed by tissue
○ Dose equivalent
§ Compares biological effects of different types of radiation by use of a QF (Qualifying Factor).

Front 151

Two systems used to measure radiation:

Back 151

○ Traditional units: used before 1985
○ Systeme Internationale (SI): adopted after 1985

Front 152

Exposure (air)

Back 152

SI: Coulombs/Kilogram (C/kg)
Traditional: Roentgen ( R)

Front 153

Absorbed Dose

Back 153

SI: Gray (Gy)
Traditional: Rad

Front 154

Dose Equivalent

Back 154

SI: Sievert
Tradional: Rem

Front 155

Radiation Measurement Units:

Back 155

• Dentistry uses smaller amount of radiation;
• Uses the prefix milli meaning 1/1000 of the units
○ Sv = mSv
○ Rem = mrem
○ Gy = mGy
○ Rad = mrad

Front 156

average effective does from background radiation

Back 156

4400 mSv per year

Front 157

Thyroid gland:

Back 157

○ Average does for 20 film series is: ~60 mrads
○ ~6,000 mrad is necessary to produce cancer in the thyroid

Front 158

• Bone marrow (maxilla and mandible):

Back 158

○ Average dose for 1 x-ray: 1-3 mrads per film, or ~60 mrads for 20 film series
○ 5,000 mrad or > for induction of leukemia (would have to take 2,000 to 5,000 films)

Front 159

Skin:

Back 159

○ Total of 250 rads in a 14 day period will cause erythemea on the skin
○ To produce this you would need 500 dental films to be exposed in a 14 day period

Front 160

Eyes:

Back 160

○ 200,000 mrad / 2,000 mSv to induce cataract formation
○ Average dose for 20 film series is: 60 mrads
○ Some scientist no longer consider this a critical organ

Front 161

Two types of radiographs:

Back 161

Intraoral radiographic examination
Extraoral radiographic examination

Front 162

ntraoral radiographic examination:

Back 162

§ Used to inspect the teeth and intraoral structures

Film is placed inside the mouth

Front 163

Extraoral radiographic examination:

Back 163

§ Inspect large areas of the skull or jaws
§ Film is placed outside the mouth

Front 164

Periapical Exam:

Back 164

• Purpose: examine the entire tooth
• Film type: periapical film
○ Peri- around
○ Apex- terminal end of the tooth
• Techniques:
○ Paralleling
○ Bisecting

Front 165

Interproximal Examination:

Back 165

• Purpose: examine the crowns (maxillary and mandibular) on a single film
○ Caries
○ Alveolar bone crest
• Periapical film (horizontal position) with the aid of tab or xcp
• Technique: bitewing technique
○ Distal of the most forward canine in premolar shot

Front 166

Occlusal Examination:

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• Purpose: examine large areas of the maxilla & mandible on one film
• Film Type: occlusal film
• Technique: occlusal technique
• Size 4 film

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Complete Mouth Radiographic Series:

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• Known as CMRS, FMS, FMX
• Represents all tooth bearing areas of the maxilla and mandible (all 32 teeth are normally located).
• Can be in combination with bitewings

14 to 20 individual radiographs

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Periapical Radiographs:

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• Two type of techniques:
Paralleling technique
Bisecting technique

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Paralleling Technique:

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• Also known as:
○ Extension cone paralleling technique (XCP)
○ Right angle technique
○ Long-cone technique

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Parallel

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Moving or lying in the same plane, always separated by the same distance and not intersecting

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Intersecting

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To curve across or through

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Perpendicular

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Intersecting at or forming a right angle

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Right angle

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The angle of 90 degrees formed by two lines perpendicular to each other

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Long axis of the tooth

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An imaginary line that divides the tooth longitudinally into two equal halves

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Central ray (CR)

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The central portion of the primary beam of x-radiation

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Vertical Axis of Teeth:

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• True vertical axis of teeth generally varies with the vertical axis of the crown by 5 to 20 degrees

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Location of the Teeth Apices:

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• Maxillary: alatragus line
• Mandibular: 0.5 cm (~0.25 inches) above the lower border of the mandible

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Central Ray (CR):

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point that is centered on the radiographic film

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Vertical Angulation:

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movement of the tubehead (PID or BID) up and down
§ Is measured in degrees
□ Downward angulation- positive (+)
□ Upward angulation- negative (-)

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Horizontal Angulation:

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movement of the tubehead (PID or BID) side to side
§ Central ray should be directed through the contacts of the teeth at an angle of 90 degrees to the film

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Point of Entry:

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• Central x-ray beam should be directed through the center of the region (film) being radiographed
○ If not: cone-cut on exposure

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Principles of Paralleling Technique:

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○ Film is placed in the mouth parallel to the long axis of the tooth
○ The central ray of the beams is directed perpendicular (at a right angle) to the film and long axis of the tooth

Film holder must keep the film parallel with the long axis of the tooth

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Overcome the Anatomy of the Oral Cavity:

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• Maintain parallelism between the film and the tooth:
○ Maxilla- place the film towards the midline of the oral cavity

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Film Holders:

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• Define: instrument that is used to position the film in the mouth
• Sample of these types:
○ Rinn XCP instruments
○ Precision film holders
○ Stabe bite-block
○ EEZEE-Grip film holder "snap-a-ray"
○ Hemostat with bite block

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Rules of Paralleling Technique:

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• Film placement: specific film placement to cover a prescribed area
• Film position: film must be parallel to the long axis of the tooth
• Vertical angulation: central ray must be perpendicular to the film and the long axis of the tooth
• Horizontal angulation: central ray must be directed through the contact areas between the teeth

Film exposure: x-ray beam must be centered on the film to ensure all areas of the film are exposed

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Step by Step Procedures:

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• Patient preparation
• Equipment preparation
• Exposure sequence for film placements
○ Anterior exposure sequence
○ Posterior exposure sequence
• Film placement
• Modifications in technique

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Exposure Sequence for Film Placements:

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• Anterior Exposure Sequence
○ Recommended to always start with anterior film because-
§ Size 1 film smaller and more comfortable
§ Patient less likely to gag
○ Posterior Exposure Film-
§ Take premolar view before molar views

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Maxillary Lateral Incisors:

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• Film centered on the lateral incisor
• Film parallel with long axis of tooth

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Maxillary Molars:

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• Include distal half of 2nd premolar

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Mandibular Premolar:

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Include distal half of the canine

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Premolar Bitewing:

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• Look at the most anterior canine

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Modification in Technique:
• Shallow palate

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○ Very difficult to establish parallelism when a patient has a shallow palate
§ Tilting of the bite block occurs
§ Less than 20 degrees usually acceptable
§ Greater than 20 degrees need to modify
□ Place two cotton rolls

Increase vertical angulation 5-15 degrees

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Modification in Technique:
• Bony growths (tori)

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○ Maxillary torus
§ Film must be placed on the far side of the torus not on the torus and then exposed
○ Mandibular tori (usually present bilaterally)

Film must be placed between the tori and the tongue not on the tori and then exposed

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Modification in Technique:
Mandibular premolar region

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○ On insertion: the film is tipped away from the tongue while the bite-block is placed firmly on the mandibular premolars (A view)

When the patient closes on the bite-block, the film moves into proper position (B view)

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Bitewing Surveys:

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• Carries
• Bone loss
• Overhangs

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Two Film Survey:

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• 2 Premolar bitewings
• When all contacts can be viewed as open on one film
• 1st premolars extracted
• Include distal half of canine

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Four Film Survey:

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• 2 Premolar films
• 2 Molar films

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Vertical Bitewings:

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Horizontal BW's can be useless for bone level interpretation with there is bone loss

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Pedo Bitewings:

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Size 0 or size 1 film

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Full Mouth Series:

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• Four size 2 posteriors
• Five size 1 maxillary anteriors
• Three size 1 mandibular anteriors
• Four size 2 vertical or horizontal bitewings
○ Vertical with clinical evidence of periodontal disease
§ Pocket depth of =/> 5mm

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Pedo Full Mouth Series:

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• When dentition is diseased
• Not taken very often
• Size 2 films for the anteriors
• Size 1 films for the posteriors
• Posteriors include canines in molar films

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Panoramic:

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• General screening
• Growth and development
• Gross pathology
• Supernumerary teeth
• 3rd molars
• Fractures

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Occlusals:

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• Impacted teeth
• Supernumerary teeth
• Localization
• Clark's rule

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Cephalometric:

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• Bony and soft tissue area of facial profile