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3rd Year BDS > Radiography > Flashcards

Radiography Flashcards

1
Q

What is the atomic structure?

A

Proton
Neutron
Electrons

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2
Q

What charge does a proton carry?

A

+1

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3
Q

What charge does a neutron carry?

A

neutral

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4
Q

What charge does an electron carry?

A

-1

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5
Q

What is the binding energy of shell K (s)

A

70 keV

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6
Q

What is the binding energy of shell L (p)

A

12 keV

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7
Q

What is the binding energy of shell M (d)

A

3keV

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8
Q

What is the general rule for protons and electrons?

A

They are the same

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9
Q

How do you calculate atomic mass?

A

Protons + neutrons

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10
Q

What is the definition of ionisation?

A

The loss of an electron requiring energy to be used

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11
Q

What is the definition of radiation?

A

Emission and propagation of energy in the forms of waves or particles

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12
Q

How do ionising radiation produce ions?

A

removing an electron

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13
Q

Which radiation types can ionise atoms?

A

alpha and beta particles

gamma rays

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14
Q

What is the definition of radioactivity?

A

Unstable atoms which decay, an imbalance in protons and neutrons
Nucleus can’t generate enough binding strength

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15
Q

What forms can radioactivity be released as?

A

Alpha: 2 protons and 2 neutrons
Beta: fast moving electrons
gamma ray: high energy electromagnetic radiation

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16
Q

What is the definition of electromagnetic radiation?

A

The propagation of wave like energy through space or matter. Bundles of energy called photons travels as a wave, but in a straight line

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17
Q

Explain how the x-ray tube create x-rays?

A
  1. Filament is heated producing a cloud of electrons
  2. Potential difference across tube accelerates the electrons at high speed towards the anode
  3. Electrons bombard the target, then brought to rest fast, energy transferred to heat and x-rays
  4. heat removed by copper bar and oil
  5. x-rays emitted via small window in the lead casing creates beam
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18
Q

In which direction do electrons travel?

A

From cathode to anode

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19
Q

How to increase the necessary voltage needed to power a x-ray machine?

A

A step-up transformer

number of coils increase the step-up need

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20
Q

What are the 2 forms of heat being produced during ionisation?

A

The incoming electron is deflected by the outer electron shell creating heat
The incoming electron collides with the outer shell of electrons displacing the electron creating heat

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21
Q

What type of spectrum does 1-3 electron give?

A

Continuous
Braking radiation
Needs a filter to remove low energy photons

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22
Q

What type of spectrum does 4 electron give?

A

Characteristic

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23
Q

What is the definition of intensity?

A

Quantity of x-ray photons in the beam - current

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24
Q

WHat is the definition of quality?

A

The energy carried by the x-ray photon - voltage

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25
Q

What factors affect the intensity/quality of the beam?

A 
Tube voltage
Tube current
Distance from target
Time length of exposure
Filtration
Target material
Tube voltage waveform
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26
Q

What rule do x-ray beams obey?

A

Inverse square law

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27
Q

What is the definition of kVp?

A

Changing this laters the force with which the electrons are drawn from the cathode to the anode

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28
Q

What changes if the kVp is reduced?

A

Gives better contract but higher tissue absorption (photoelectric effect predominates)

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29
Q

What changes if the kVp is increased?

A

Reduced attenuation in matter
Decreases contrast
Increases dose but not linearly (compton scatter)

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30
Q

What is the definition of mA?

A

Changing the current alters the number of electrons on the cathode which can be drawn to the anode (beam intensity)

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31
Q

What changes if the mA is increased?

A

Increases beam intensity, this can reduce image noise and improve radiographic contrast but does increase dose proportionally

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32
Q

What is the equation of the inverse square law?

A

Intensity = 1/d2
d = distance from source
e.g. in air, doubling the distance from an x-ray source reduce intensity to 1/4

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33
Q

How can radiation cause damage?

A

Damage DNA directly or indirectly

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34
Q

How does radiation damage DNA directly?

A

Radiation interacts with the atoms of a DNA molecule or another cell component
Gives off 33eV, therefore able to break a C-C bond (4.9eV)

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35
Q

How does radiation damage DNA indirectly?

A

Radiation interacts with water in the cell, producing free radicals which can induce damage

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36
Q

What types of damages can occur to the DNA?

A

Single break
Double break
Chemical change

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37
Q

What factors will change the biological effect caused by the radiation?

A

Type of radiation
Tissue or type of cell
Dose
Dose rate

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38
Q

What tissues are considered highly radiosensitive?

A 
Lymphoid tissue
Bone marrow
GI epithelium
Gonads
Embryonic tissues
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39
Q

What tissues are considered moderatly radiosensitive?

A 
Skin
Vascular endothelium
Lung
Kidney
Liver
Lens
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40
Q

What tissues are considered lowly radiosensitive?

A

Salivary glands
CNS
Muscle
Bones/Cartilage

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41
Q

What is the definition of deterministic radiography effects? and signs?

A

High radiation dose received over a short time

Skin erythema, sterility and tissue necrosis

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42
Q

What is the definition of stochastic radiography effects? and future effects?

A

Low doses received over a prolonged period

Cancer, leukemia and genetic effects

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43
Q

What are the 4 possible fates of x-rays?

A

Absorption
Transmission
Scattering
Attenuation

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44
Q

Why can absorption be bad?

A

Photoelectric effect

Most likely to cause harm to tissues

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45
Q

Explain the photoelectric effect?

A

Low energy photons
Incoming photons interact with bound inner shell electron, which is ejected with high energy called the photoelectron into tissue
The ejected photoelectron behaves like other x-rays, and ejects other photoelectrons, which creates the majority of ionisation interactions, which can cause damage
The vacancy of the inner electron shell is filled by the outer electron shell, forming a low energy radiation
Atomic stability is restored by capture of a free electron

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46
Q

Explain the Compton effect?

A

High energy photons
Incoming x-ray photon interacts with free or loosely bound outer shell electron
Outer shell electron is ejected - Compton recoil electron - with loss of energy, undergoing further ionisation interactions within tissues
Remained of incoming photon is scattered from original path as a scattered photon
The scattered photon may undergo further compton interactions, photoelectric interactions and escape tissues via scatter
Atomic stability is regained after capture of anther free electron

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47
Q

What is essential for the photoelectric effect to occur?

A

The energy of the incoming x-ray photon must be equal to or greater than the binding energy of the inner shell electron

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48
Q

How does tissue density affect number of electron shells?

A

As tissue density increases, the number of electron shells increase, with a corresponding increase in binding energy at the inner shell

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49
Q

How to work out the probability of photoelectric reactions occuring?

A

Proportional to Z (atomic number)3 (cubed)

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50
Q

How is contrast produced between tissues?

A

As they have different radiodensities

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51
Q

What do intensifying screen use to convert x-rays to light? and what is it sued for?

A

Photoelectric effect

Extra-roal work

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52
Q

What is essential for the Compton effect to occur?

A

The energy of the incoming x-ray must be much greater than the binding energy of the outer shell electron

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53
Q

Why does the Compton effect not depend on the atomic number?

A

As it is an outer electron, and so does not contribute to the contrast of the image

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54
Q

What contributes to image degradation?

A

High energy scattered photons produce forward scatter

Low energy scattered photons produce back scatter

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55
Q

What do the Photoelectric and Compton effect result from?

A

Ionisation of tissues

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56
Q

What are the 4 major guidelines for radiographic radiation usage?

A

Radiographic standards in primary dental care
Dental practitioners on the safe use of X-ray equipment
Selection criteria for dental radiographs
Safe use of dental cone beam CT equipment

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57
Q

Explain the linear no-threshold model for radiographic radiation?

A

Increasing the dose with increase the change of side effects
Any dose can give side effects
Effect is directly proportional to dose at all dose levels

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58
Q

What are the side effect risk of causing fatal cancer from an intra-oral x-ray?

A

1:4,000,000

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59
Q

What are the side effect risk of causing fatal cancer from an OPG?

A

1:2,000,000

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60
Q

What are the side effect risk of causing fatal cancer from staff standing 1.5m away?

A

1:67,000,000

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61
Q

What is the definition of a radiation absorbed dose?

A

A measure of the amount of energy absorbed from the radiation beam per unit mass of tissue and can be measured using a dosimeter (not reflect biological damage)
Measured in Gray (Gy)

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62
Q

What is the definition of an equivalent dose?

A

This measures the effects of different types of radiation on tissues e.g. alpa are completely absorbed, x-rays are only partially absorbed
Equivalent dose = absorbed dose * radiation weighting dose factor

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63
Q

What is the radiation weighting factor for an x-ray?

A

1

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64
Q

What is the definition of the effective dose?

A

Takes account of the fact that different tissues show different sensitivities to radiation, and allows comparison of risk of different types of radiation exposure. Tissue weighting factor
Effect dose = Sum (absorbed dose * radiation weighting factor & tissue weighting factor)

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65
Q

What does the effective does allow us to compare? and its measurement?

A

Comparison between whole body irradiation and a radiation dose which is uniformly distributed
Sieverts (Sv)

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66
Q

What is the weighting factor for salivary glands?

A

0.01

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67
Q

What is the value of the natural dose of radiation be received daily?

A

7.5 millisieverts per day

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68
Q

Name the 5 main sources of radiation?

A 
Medical
Radon
Gamma rays from ground and buildings
Internal from food and drink
Cosmic
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69
Q

What % source is radon?

A

50.1%

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70
Q

What are some everyday items that give off radiation?

A

Granite
Bananas
Brazil nuts

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71
Q

How do dental radiographs compare to everyday life radiation exposure/

A

200g brazil nuts
28 hours in Aberdeen
European flight

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72
Q

What is the ratio for 1mSv to give a fatal case of cancer?

A

1:20,000

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73
Q

What is the effective dose for an intraoral x-ray?

A

0.003mSv

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74
Q

What is the effective dose for an OPG?

A

0.010mSv

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75
Q

What dose will a staff member receives standing 1.5 metres away?

A

0.0003mSv

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76
Q

What is the ALARP principle?

A

As Low As Reasonably Practicable

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77
Q

What are the best ways to reduce dental raditation exposure?

A

Technique
IR rules/guidance
Equipment

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78
Q

What are the consentual laws for x-rays?

A

Implied
Explain which tooth and why
Double check the tooth

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79
Q

When is direct action film used?

A

Packet film

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80
Q

When is indirect action film used?

A

Intensifying screen

Cassette

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81
Q

Name 2 types of digital receptors?

A

Solid-state sensors

Phosphor plates*

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82
Q

Explain how direct action film work?

A

Sensitive to x-ray photons

Intra oral work (bitewings and occlusals)

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83
Q

Explain how indirect action film works?

A

Used with intensifying screens in a cassette
Film sensitive to light photons emitted by intensifying screen when they are stimulated by X-rays
Require less exposure to x-rays to produce an image

Panoramic, cephalometric films and sialography

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84
Q

Name the parts of a direct-action film?

A

Film
Protective black paper
Lead foil
Outer wrapper

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85
Q

What is the function of the outer wrapper?

A

Plastic
Sealed to maintain light tightness and prevent saliva ingress
White side must face x-ray beam

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86
Q

What is the function of the lead foil?

A

Absorbs some of the residual radiation, preventing further penetration
Prevents ‘backscatter’
Needs to be placed the correct way up

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87
Q

What is the function of the black paper?

A

On both sides of film

Protecting from light, saliva and damage whilst being unwrapped

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88
Q

What is the structure of radiographic film?

A 
Protective layer
Emulsion
Adhesive
Plastic base
Adhesive
Emulsion
Protective layer
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89
Q

What is the active part of the radiographic film?

A

Emulsion

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90
Q

What is the function of the plastic base?

A

Supports the emulsion bit does not contribute to the image

Transparent cellulose acetate

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91
Q

What is the function of the adhesive?

A

Holds the emulsion on the base

Very thin

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92
Q

How does emulsion work and what is it’s overall function?

A

2 layers on either side of base
Attached by adhesive
A gelatin matrix contains silver halide crystals
These crystals are sensitive to X-ray photons, those that are struck by photons appear as black on the processed image

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93
Q

What is the function of the protective layer?

A

Outermost surface

Protect

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94
Q

How is latent image formation carried out?

A

Crystal exposed to x-ray photon
Displaces an electron
Attracts Ag
Forms black spot

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95
Q

How should you orient the intraoral film?

A

Dot embossed on one corner, with the raised aspect to the front (towards beam)
Dot appears on image raised, and viewed as if operator was facing patient

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96
Q

For periapicals where should the dot be found?

A

Occlusal surface

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97
Q

For bitewings where should the dot be found?

A

Palatally

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98
Q

For occlusal films where should the dot be found?

A

Anteriorly

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99
Q

What is the definition of optical density?

A

Describes the extent of film blackening

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100
Q

What does the characteristic curve show?

A

Variation in optical density with different exposures

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101
Q

What can affect the amount of background fog on a film?

A

Colour of plastic base

Development of some unexposed silver halide crystals

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102
Q

How is film speed determined?

A

Size and number of silver halide crystals

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103
Q

What are the advantages of using faster film?

A

Use less radiation to achieve the same optical density

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104
Q

What is the definition of film latitude?

A

Range of exposures that produce visible difference in optical density

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105
Q

What is the definition of film contrast?

A

The difference in optical density between 2 points on the film that have received different exposures

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106
Q

What is the definition of resolution?

A

A measure of the ability to differentiate between differing structures in close proximity

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107
Q

What is the resolution of direct action film?

A

10 lp per mm

108
Q

What is the resolution of indirect action film?

A

5 lp per mm

109
Q

What affects resolution?

A

Penumbra

Size of silver halide crystals Contrast

110
Q

Name the parts of indirect action film?

A 
Plastic front
Front intensifier
Double-sided film
Rear intensifier
Felt backing
Metal back
111
Q

Explain how do intensifying screens turn x-ray beams into a latent image?

A

Fluorescent phosphors absorb x-rays
Converting it to visible light by the photoelectric effect
The light then forms a latent image on the film emulsion
90% light and 10% x-ray reduces dose

112
Q

How should you select film for intensifying screens?

A

Sensitive to the emissions wavelength of the screen
Speed
Resolution
Latitude

113
Q

What must be taken under consideration when picking a film and screen type?

A

Quality of image

Dose to patient

114
Q

What characteristics must a cassette have to be functional?

A 
Strong but lightweight
Reusable
Radiotranslucent on tube side
Light tight
Rigid
Easy to clean
Cassette orientation tube side to patient
Patient ID attached
115
Q

What must be used when using a cassette?

A

A side marker

116
Q

What are the stages of chemical processing?

A 
Developing
Washing
Fixing
Washing
Drying
117
Q

Explain the process of developing film?

A

Sensitised silver halide crystals in the emulsion are converted to black metallic silver to produce the back and gray parts of the image

Developer is alkaline

118
Q

Explain the process of washing, after developing?

A

Film is washed in water to remove residual developer solution

119
Q

Explain the process of fixing?

A

Desensitised silver halide crystals in the emulsion are removed to reveal the transparent or white parts of the image and the emulsion is hardened

Fixer is acidic

120
Q

Explain the process of washing, after fixing?

A

Film is washed to remove residual dixer solution

121
Q

Explain the process of drying?

A

Radiograph is dried

122
Q

Explain how an automatic film processing device works?

A

Film is loaded in the darkroom, or a daylight process where darkroom facilities are still required for loading and maintenance. As with wet developing statis of chemical solutions must be well maintained

123
Q

Explain how self-developing films work?

A

Are in a sachet containing developer and fixer. Once exposed frst the developer, then the fixer are introduced. The filam can be viewed after a minute but must be rinsed for at least 10 mins soon after to remove chemicals
Poor image quality and deteriorates rapidly

124
Q

What are the requirements for a darkroom?

A 
Must be light tight
Safe light (red)
Light tight film hopper
Ventilation
Well maintained
Processor maintenance
125
Q

Where to store film?

A

Cool and dry

Away from chemical and radiation

126
Q

How to care for screens?

A

Reg cleaning
Avoid scratches
Check for any loss of film

127
Q

Name 2 types of Solid state sensors?

A

Charge coupled device

Complementary metal oxide semiconductor

128
Q

Describe the solid state drive sensor?

A 
Film packet size but 5-7mm thick
Cabled to transfer data to PC
Can be wireless but bulkier
Can't be autoclaved (barrier envelope)
Consists of silicon chip based pixels and electronics encased in plastic holding
129
Q

Explain the process of how a charge-coupled device converts x-rays to a latent image?

A

Individual pixels consists of P- and N-type silicon
Arranged in rows and columns
Scintillation layer above array
X-ray hit the scin layer and converted to light
Light interacts with silicon (photoelectric effect) to create a charge packed for each pixel
Light is concentrated by electrodes
Image is read by transferring each row of pixel charges
Transferred to amplifier and transmitted to PC

130
Q

Each sensor has how many pixels in a CCD?

A

1.5-2.5 mil

131
Q

WHat is the size of 1 pixel?

A

20-70um

132
Q

Explain the process of how a complementary metal oxide detector converts x-rays to a latent image?

A

Similar construction to CCD
Consists of an array of pixels
Each pixel is isolated from it neighbour and directly connected to a translator
THe charge from each pixel is transferred t the transistor as a voltage enabling the individual pixel to be assessed

133
Q

Describe what an extra-oral sensor is, what it’ll replace and an example?

A

A long narrow pixel array is aligned with a thin slit shaped x-ray beam which scans across the patient
Replace indirect, intensifying and cassette films
OPGs and cephalometry

134
Q

How to use a photostimulable phosphor storage plate (PSP)?

A 
No direct connections to computer
Can be reused
Placed in narrier envelope
Dot is flat
Blue side is active and must face x-ray tube
135
Q

Name the parts of a PSP?

A 
Protective layer
Phosphor layer
Reflective layer
Conductive layer
Support
Backing layer
136
Q

What is the phosphor layer function?

A

Absorbs and stores x-ray energy not attenuated by patient

137
Q

What is the difference between CCD/CMOS and PSPs?

A

CCD and CMOS signal straight to a computer

PSPs require the plates to be placed into a reader

138
Q

Explain how do phosphor plate reader work?

A

Read using laser beam
Stored x-ray energy in the phosphor layer is released as light which is detected by the multiplier tube and converted into a voltage which is input to the analogue to digital converted of the connected computer and displaced as a digital image

139
Q

What does the plate reader laser do, other than read the image?

A

Resets the electrons, and so wipes the plate

140
Q

Explain how the computer processes the phosphor plate reader data?

A

Analogue voltage from each pixel is changed by the analogue to digital converted into a discrete numerical digital signal
Each pixel has a x and y coordinate and is allocated a number between 0-255 grayscale
0 - no attenuation
255 - total attenuation
Computer allocates an appropriate colour from grayscale to create the visual image on the monitor

141
Q

0 Grey scale?

A

Black

142
Q

255 Grey scale?

A

White

143
Q

What determines the information, size, detail and resolution of the image?

A

Number and size of pixels along with the number of shades of grey available

144
Q

Manipulating the image and increasing the contrast can?

A

Remove the middle part of the greyscale

145
Q

Manipulating the image and increasing the brightness can?

A

Increase or decrease the pixel number (darker or lighter)

146
Q

Manipulating the image inversion can?

A

Make a positive image of the existing negative image

147
Q

Manipulating the image and embossing it can?

A

Appear to enhance the edges of structures

148
Q

Manipulating the image and increasing the magnifcaiton can?

A

Will lose some detail depending on pixel size and resolution

149
Q

Manipulating the image and pseudo colouring aspects can?

A

Draw eye to certain areas due to colour use

150
Q

Where to store film and hard copies?

A

Patient’s record

151
Q

Where to store digital copies?

A

r4

152
Q

Why is repetition of the same x-ray illegal?

A

Not justified under the IR(ME)R regulations

153
Q

Name the 5 principles of shadow casting

A 
Focus to object distance large
Object to film distance small
Object and film parallel
X-ray beam perpendicular to object and film
Radiation source as small as possible
154
Q

What is the effect of focus to object distance?

A

Greater focus to object distance reduces magnification

155
Q

What is the effect of change in object to film distance?

A

Larger object film distance increases magnification

156
Q

What is the effect of object/film/beam angulation?

A

Film - image elongated
object - image foreshortened
x-ray - image distorted

157
Q

What is the definition of sharpness?

A

How well the detail of an object are defined

158
Q

What is the effect of focus size?

A

Smaller focus size produces a sharper image

159
Q

Name the 5 factors that affect sharpness?

A 
Focal spot size
Focal spot to object distance
Object to film distance
Image receptor
Movement
160
Q

What is the definition of penumbra?

A

Zone of unsharpness along the edges of images in a radiograph

Partial shadow (between complete shadow and complete illumination)

161
Q

What is the effect of focus to object distance (penumbra)?

A

Greater focus to object distance reduces magnification and penumbra

162
Q

What problems does a radiograph give rise to?

A

2D image of 3D
Shape determination
Superimposition
Distortion

163
Q

Explain how to create the perfect intraoral image?

A

Image receptor should be flat
Image receptor should be parallel to long axis of the tooth
IR should be as close as tooth as possible
Central ray should be perpendicular to object and image receptor
Distance between focus and tooth should be large

164
Q

WHat is the selection criteria to think about when choosing radiograph type?

A 
Detection of caries
Detection of apical infection/inflamm
Perio status
Trauma
Presence and position of unerupted teeth
Assessment of root morphology
During endodontics
Pre Op and Post OP apical surgery
Detailed evaluation of apical cysts and other lesions
evaluation of implants
165
Q

Explain the paralleling technique theory?

A

Film placed in holder and positioned parallel to the long axis of the tooth
X-ray beam aimed at right angles to tooth and film
Use of holder allows the image to be reproducible

166
Q

Explain the bisecting angle technique theory?

A

Film is placed as close to tooth as possible
Angle between long axis of tooth and film is assessed and mentally bisected
Beam is aimed at right angles to the bisected line
Give accurate image

167
Q

What are the advantages and disadvantages of the paralleling compared to the bisecting angle technique?

A 
Adv:
- sharper less distorted image
- correct centring of image on film
- less guesswork
- reproducible
- head position not critical
Dis:
- difficult or impossible if palate low or FoM shallow
Can be difficult if using rubber dam clamps
- strong gag reflex
168
Q

Selection criteria for a horizontal bitewing?

A 
Caries in posterior
Deficient/leaky restorations
Poorly contoured restorations
Calculus
Early perio bone loss
169
Q

Advantages of using a horizontal bitewing holder?

A

Improves centering
Reduces overlapping
Serial radiographs comparable

170
Q

Explain the horizontal bitewing placement technique

A

Beam is aimed at right angles to the film and thog the interproximal space to prevent overlap

171
Q

Selection criteria for a vertical bitewing?

A

Useful for demonstrating mild to moderate alveolar bone loss (BPE4)

172
Q

Explain the vertical bitewing technique?

A

Same but different film holder

173
Q

Selection criteria for an upper standard occlusal radiograph?

A

Periapical assessment of upper anterior teeth
Presence of unerupted canines or supernumeraries
For parallax in conjunction with OPG
Size of cysts/tumours
Assessment of alveolar fractures

174
Q

Selection criteria for an upper oblique occlusal radiograph?

A

Similar to standard occlusal but shows premolar and molar regions
Cleft palate

175
Q

Selection criteria for a upper vertex occlusal

A

Similar to standard occlusal but gives plan view of palate (will show buccolingual position of unerupted canines
No longer recommended

176
Q

Selection criteria for Lower 90 true occlusal?

A

Detection of submandibular calculi
Assessment of buccolingual position of unerupted mandibular teeth
Evaluation of buccolingual cortical expansion
Assessment of mandibular width prior to implant placement

177
Q

Selection criteria for Lower 45 standard occlusal?

A

Similar to a true occlusal but also as a periapical view of the lower anteriors

178
Q

How to x-ray soft tissue?

A

Use film holder

Reduce exposure

179
Q

How to quality assure the x-ray machine?

A

Check:

  • machine outputs
  • Image processing equipment
  • Image quality
180
Q

What is the basis of a Grade 1 radiograph?

A

Excellent

No error of patient prep, exposure, positioning, processing or film handling

181
Q

What is the basis of a Grade 2 radiograph?

A

Diagnostically
Some errors of patient prep, exposure, acceptable positioning, processing or film handling, but which do not detract from the diagnostic utility of the radigraph

182
Q

What is the basis of a Grade 3 radiograph?

A

Unacceptable
Errors of patient prep, exposure, positioning, processing or film handling, which render the radiograph diagnostically acceptable

183
Q

Grade targets for minimum radiographic quality?

A

1 - no less than 70%
2 - no greater than 20%
3 - no greater than 10%

184
Q

Grade targets for interim radiographic quality? (training or new equipment)

A

1 - no less than 50%
2 - no greater than 40%
3 - no greater than 10%

185
Q

How does the x-ray tube move?

A

Passes behind the patient, the image receptor crosses in front of their face

186
Q

Name the 5 parts of a tomograph?

A 
Tube
Connecting bar
Pivot
Cassette
Stationary table top
187
Q

Name the 2 parts of an OPG machine?

A

Detector

X-ray tube

188
Q

Selection criteria for an OPG?

A 
Bony lesions or unerupted teeth that can't be demonstrated on an ntraoal film
Grossly neglected mouth
Assessment of periodontal disease
Assessment of 3rd molars
Unable to tolerate intraoral views
Ortho assessment
Assessment prior to GA
Mandibular fracture
TMJ disease
Antral disease
Pre-implant planning
189
Q

What are the positioning problems for an OPG?

A 
Too high
Too low
Too close
Too far
Rotation
Lateral inclination 
Artefact (earrings)
Shoulders (large)
Movement
190
Q

What causes ghosting?

A

Bone’s density

191
Q

What are the advantages of using an OPG?

A

Large area is imaged, all anatomy within the focal trough will be visualised
Positioning is simple
Overall view for rapid assessment of underlying disease
Overall evaluation of periodontal disease or ortho assessment
Both condylar heads shown
Antral floor is visualised
very useful for fractures - see both sides of mandible
Radiation dose is likely to be lower than a full set of periapicals

192
Q

What are the disadvantages of using an OPG?

A

Structures outwith the focal trough will be missed
Soft tissues, air shadow, ghost shadow and artefact can obscure structures
Magnification of image
Resolution is lower than intraoral
Require patient to remain still for 20+ seconds
Patient’s maxilla/mandible must be same shape as focal trough
Operator must be skilled

193
Q

What are the ideal quality criteria for a successful OPG?

A

All upper and lower teeth and supporting bone should be clearly demonstrated
Whole mandible included
Right and left molar teeth should be equal in their mesiodistal dimension
Uniform density across the image, no air shadow above tongue
Hard palate should be above apices of maxillary teeth
No artefacts
Image must be annotated with side marker and name/ID

194
Q

What equipment is needed for a cephalometric radiograph?

A

Apart of OPG Unit
Have a fixed FFD > 1m, usually 1.5-.7m (to minimise magnification effect)
X-ray output and film.image receptor parallel (beam perpendicular to image receptor)
Uses positioning aids to ensure standard position of patient and reproducibility of projection
Includes a radiopaque marker to calculate magnification factors
Requires collimation device to restrict radiation to cranial abs and thyroid
employs filters to ensure the soft tissues structures of the face are visualised

195
Q

Name the 2 types of cephalometric projections?

A

True cephalometric lateral skull

Cephalometric posteroanterior of the j aws

196
Q

What are the main indications for cepahlomerric radiographs?

A 
Orthodontics:
- initial diagnosis
- treatment planning
- monitoring treatment progress
- appraisal of result
Orthognathic surgery:
- pre-OP eval
- treatment planning
- post OP appraisal 
- long term follow up
197
Q

Explain how to position a patient for a cephalometric radiograph?

A

Sagittal plane parallel to image receptor
X-ray beam perpendicular to image receptor
Frankfort plane horizontal
Patient’s head is immobilised using ear prongs in EAM
Magnification measure applied to nasion
Check approp filtres are correctly positioned
Teeth should be in ICP
Tongue to roof of mouth with lips closed

198
Q

What is essential in quality criteria for a successful cephalometric radiograph?

A 
Patient facing to the right
True lateral
Marker on nasion
Teeth in ICP
Use of collimation
Lower border of mandible visualised
199
Q

What is the definition of parallax?

A

Trying to identify whether a structure is behind or infront of another structure

200
Q

Explain the process of suing parallax to identify position of the structure?

A

If objects moves in the same direction as viewer shift, then it is positioned posteriorly
If object moves in opposite direction to viewer shift then it is position anteriorly

201
Q

What is SLOB acronym?

A

Same lingual

Opposite buccal

202
Q

A variably-sized radiolucent strip between the superior surface of the tongue and the palate can be seen, this may obscure the roots of the anterior teeth due to overexposure, how can you minimise this?

A

Patient place tongue flat against palate during imaging

203
Q

Space created between the upper and lower lips can be seen as a kiss-shaped radiolucency over the crowns of the maxillary and mandibular incisors, how can you minimise this?

A

Patient to close lips around the bite-stick can prevent overexposure of this area

204
Q

A ghost of the cervical spine is formed when the anterior teeth are imaged because of the x-ray beaming from behind, this may obscure the anterior region of the jaw, how can you minimise this?

A

Patient to stand as tall as possible with their cervical spine extended maximally helps minimise the superimposition

205
Q

What may have occurred if the 3 thin radiopaque lines which run parallel to the posterior wall of the maxillary sinus are not present?

A

Destructive disease

206
Q

Explain how to fully assess the alveolar processes and teeth for an OPG?

A

Assess the crestal bone position of the alveolar processes to identify any periodontal bone loss
Examine the periodontal ligament space and lamina duras around each tooth for signs of inflammatory disease
Examine the follicles and papillae of developing teeth to identify any abnormalities
Evaluate teeth for presence/absence/eruptive or positional abnormalities, caries, poor restos, calculus or developmental or acquired abnormalities

207
Q

Name the 7 steps to interpret an OPG?

A

Assess the periphery and corners of the image
Examine the outer cortices of the mandible
Examine the cortices of the maxilla
Examine the zygomatic bones and arches
Assess the internal density of the maxillary sinuses
Assess the structures of the nasal cavity and the palates
Examine bone the pattern of the maxilla and mandible

208
Q

What to assess when assessing the periphery and corners of the image

A 
Orbits
Articular processes of the temporal bones
Cervical spine
Styloid processes
Pharynx
Hyoid bone
209
Q

What to assess when assessing the outer cortices of the mandible?

A

Anterior and posterior rami
Coronoid process
Condyles and condylar necks
Inferior border

Evenness

210
Q

What to assess when assessing the cortices of the maxilla?

A

Zygomatic process of maxilla

Pterygomaxillary fissure

211
Q

What to assess when assessing the internal density of the maxillary sinuses?

A

Compare left to right

Opacification common sign of inflammation or worse

212
Q

What to assess when assessing the structures of the nasal cavity and the palates?

A

Hard palate and the conchae extending along both sides
Nasal septum in midline
Soft palate extending from posterior hard palate into oropharynx

213
Q

What to assess when assessing the bone the pattern of the maxilla and mandible?

A

Density and pattern of the trabeculae

Mandible examine size, pstion, cortication and symmetry of the IAN canals, mandibular foramen and mental foramina

214
Q

Name the 6 relevant points in the history that relate to CVD?

A 
Chest pain
Angina
MI
HT
Medication
SOB
215
Q

When treating an emergency patient which has unstable angina, what is necessary to avoid and what can save their life?

A 
Adrenaline
GTN spray (under tongue)
216
Q

What should be deferred for an uncontrolled cardiac failure?

A

Any form of anaesthesia until medication and symptoms are stabilised
Placing this sort of patient in a supine position could exacerbate dyspnoea, and should be avoided

217
Q

How can you assess the severity of a patient’s cardiovascular health?

A

Waking up in the night with breathlessness or has orthopnoea

218
Q

Name the 8 procedures which need antibiotic prophylaxis?

A

Dental extractions
Any procedure involving the raising of a mucosal/ mucoperiosteal flap
Biopsies
Any subgingival procedure eg placement of orthodontic bands (not brackets), scaling of teeth, irrigation of periodontal pockets
Intraligamentary injections
Reimplantation of avulsed teeth
Incision and drainage of an abscess Placement of dental implants
During diagnostic phase of root canal therapy if it is thought likely that an instrument may pass through the tooth apex

219
Q

What is the main bacteria which causes infective endocarditis?

A

Viridans Streptococci

220
Q

What instrument must be avoided with a patient with a pacemaker?

A

Ultrasonic scaler

221
Q

Name the 6 post-transplant treatment complications can occur?

A

Immunosuppression
Steroid therapy
Risk of infective endocarditis (in the first 6 months)
Gingival overgrowth as a result of post-transplant drug therapy Supersensitivity of the transplanted heart to circulating catecholamines which may include epinephrine in dental local anaesthetics
Hepatitis, HIV Infection (rarely)

222
Q

What to advice to a patient with lymphatic/venous disorder?

A

Patient should be treated with legs elevated to minimise dependent oedema, but the practitioner should beware of orthopnoea.

223
Q

What to identify on the first observation of the patient?

A 
Patient’s general demeanour
Colour
Whether short of breath at rest (SOBAR), or on minimal exertion, eg walking into the surgery
Finger clubbing
Cyanosis
Swollen ankles
224
Q

When does finger clubbing occur?

A

IE
Cyanotic congenital heart disease
Thyrotoxicosis

225
Q

What limit should be put on LA + ADR for patients taking beta blockers/

A

2 cartridges max
Sides:
- dry mouth
- lichenoid reaction

226
Q

What limit should be put on LA + ADR for patients taking non-K sparing diuretics?

A

1/2 cartridges max

227
Q

What to avoid for patients which have just undergone cardiac transplatation?

A

Can super react to ADR so avoid LA

228
Q

How long should elective dental surgery be avoided for recent MI?

A

At least 3 months but ideally a year

Under emergency situation, carried out with medical consultation

229
Q

Name the 14 relevant points in the history that relate to respiratory disease?

A 
Smoking history
Cough
Sputum (colour)
Acute problem or chronic disorder? Infection —URTI/LRTI
Sinusitis
Pneumonia - primary, secondary, atypical
Asthma
COAD
TB
Bronchiectasis
Cystic Fibrosis
Haemoptysis
Lung Cancer
230
Q

What should be avoided for a patient suffering with COAD?

A

Treatment should be avoided during an exacerbation and always carried out with LA

231
Q

If patient has Tb what necessary precautions should be taken by the dentist?

A

Aerosols should be reduced
Rubber dam
Masks and spectacles are mandatory

232
Q

What are the oral symptoms of sarcoidosis?

A

Gingival swelling found to be due to sarcoid

233
Q

Name 4 oral manifestations for respiratory disease?

A

Gingival swelling (sarcoid)
Ulceration (TB)
Hyperpigmentation (lung cancer) Drug induced xerostomia

234
Q

What to look out for if suspicious of respiratory disease?

A 
Colour 
Central cyanosis
Dyspnoea
Tachypnoea, (use of accessory muscles)
Finger clubbing
Cervical lymphadenopathy (URTI, TB)
Bounding pulse
Oral hyperpigmentation
Flapping tremor
235
Q

What are the oral side effects for corticosteroids?

A

As a result of this oro-pharyngeal candida infection may occur. In order to avoid this complication patients should be advised to rinse and gargle with water after use of their inhaler

236
Q

What are the oral side effects for beta adrenergic agonist bronchodilators?

A

Dry mouth, taste alteration and discolouration of the teeth.
Dry mouth may increase caries incidence and thus a preventive regimen is important.
If the dry mouth is severe artificial saliva may be indicated.

237
Q

What to be wary about when a patient is taking cough suppressants?

A

There is a theoretical possibility that the adrenergic effects of epinephrine in dental local anaesthetics will be enhanced by ephedrine so dose reduction should be considered.

238
Q

What to do for anaphylactic shock?

A

ADR IM dose of 0.5ml increments of 1:1000 and IV hydrocortisone (200-500mg)

239
Q

What are the signs and symptoms for bleeding disorders?

A
  • Pale
  • Jaundice
  • Bruising
  • Bleeding gingiva
  • Glossitis
  • Opportunistic infections
  • Gingiva enlargement
240
Q

What is the current advice for surgical operations with a patient taking Warfarin?

A

INR less than 3.0 without alteration of the Warfarin dosage

241
Q

What should NEVER be used with Warfarin?

A

Antifungals

MICONAZOLE

242
Q

Which sedation should be avoided for a patient suffering from pernicious anaemia?

A

NO sedation

243
Q

Which LA block is contraindicated for patient with bleeding disorders?

A

IAN

244
Q

What are the optimal viewing conditions for a digital radiograph?

A

Reduce surrounding light
Use magnification
Look directly at image

245
Q

What are the optimal viewing conditions for a film radiograph?

A

Good light box or back lit screen
Low ambient light
Allow time for eyes to adjust
Use a magnifier

246
Q

What are the disadvantages of radiographs?

A

2D representation of a 3D image
Grayscale
Artefacts
Guessing game

247
Q

Describe the attenuation of x-rays from decreasing attenuation to increasing attenuation?

A 
Mental
Enamel
Dentine
Cementum/bone
Soft tissues
Fluid 
Air
248
Q

Cervical burnout?

A

Shadowing interproximally can be deceiving

249
Q

What other shadows may be seen on a radiograph?

A

Lip shadow

Tori

250
Q

How to structure a radiographic report?

A 
Patient ID
Age
Name the views (horizontal/vertical)
Grade
Teeth present
Caries
Restorations
Prosthetics
Perio
Bone levels
Other (lesions, PDL widening and tooth wear)
Incidental findings
Summarise
251
Q

What are the 2 legislations for radiography?

A

IRR17

IR(ME)R 2017

252
Q

What is the size of the controlled area?

A

Area may be defined within the primary X-ray
beam until it has been sufficiently attenuated by distance or shielding and within 1.5m of the X-ray
tube and the patient

253
Q

What minimum unintended dose is necessary to investigate?

A

1mSv

254
Q

When should IR equipment receive maintenance and routine testing?

A

Annual

At least 3 yearly intervals

255
Q

What is the kV range for new intraoral sets?

A

60-70

256
Q

What can you wear for x-ray protection?

A

Lead apron

Thyroid collar

257
Q

What is the basic framework pathway to be followed during the course of exposure to ionising radiation?

A 
Referral
Procedure justification
PAtient identified
Exposure
Report
258
Q

What does ALARP stand for?

A

As low as reasonably practicable

259
Q

What can be used to reduce dose?

A

Holder and beam aiming device

260
Q

What information must a referrer supply?

A

Accurate, unique identification of the patient
Accurate clinical information sufficient to allow justification to take place
Where relevant – information on pregnancy (not usually required in dentistry)
The unique identification of the referrer (should be legible)

261
Q

What information must the operator possess to be entitled to carry out practical IR exposure?

A 
Patient ID
Making the radiographic exposure
Reporting radiographs
Processing radiographs
Calibrating equipment
262
Q

What roles in IR does a dentist have?

A

Practitioner - justify
Referrer - request
Operator - operating and reporting

263
Q

What should you do in times of accidental or unintended exposures?

A

An unintended dose is one when an examination should not have taken place. e.g. the
wrong patient is imaged. This is normally externally reportable
A dose ‘significantly greater than that generally considered to be proportionate in the
circumstances’ e.g. if a view is repeated or if the wrong exposure factors are selected or if
the wrong procedure is carried out (e.g. wrong side)
Reporting depends on the additional dose:
For intraoral and extraoral dental films – if unintended dose is x 20 (this may be
reduced in the near future when the updated IPEM guide is published).
For CBCT – if unintended dose is x 3.
If reportable this will be to the IR(ME)R enforcer.
ALL INCIDENTS MUST BE REPORTED ON DATIX, THIS INCLUDES NEAR MISSES

264
Q

Explain duty of candour in respect to IR?

A

In the event of an accidental or unintended exposure, you have a duty of candour. This requires the referrer, practitioner and the individual (patient) being informed of the occurrence of a clinically
significant unintended or accidental exposure.

265
Q

Explain other ways for dose limitation of IR?

A

Ascertain if there is any previous imaging that may affect the current prescription/request.
Check records and ask the patient. This can be tricky in dentistry as not all records are held centrally, and some patients may be confused as to the exact type and timing of any imaging.
Consider if the prescribed/requested imaging is the most suitable for the patient at this time
– it might be advantageous to use ultrasound, CBCT or MRI.
Limit the field that is irradiated

3rd Year BDS (21 decks)

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