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Complete Dentures 1 > Radiology > Flashcards

Radiology Flashcards

1
Q

What is the focal trough?

A

Image layer –> the cross section of the tomograph that’s in focus (mandible and maxilla)

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2
Q

Indications for panoramic radiograph

A
  • Evaluation of third molars
  • Evaluation of trauma
  • Evaluation of large lesions
  • Inability to visualize the entire lesion on smaller film
  • Generalized disease (diseases affecting jaw bone)
  • Intolerance to intraoral films
  • Assessment for surgical procedures (implants, TMJ disorders, craniofacial anomalies)
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3
Q

Advantages of panoramic radiographs

A
  • Well tolerated by patients
  • Minimal time of exposure when compared to FMS
  • Easy technique
  • Broad anatomical coverage
  • Relatively low patient dose
  • Useful for patient education (secondary to diagnostic purpose)
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4
Q

Disadvantages of panoramic radiographs

A
  • Lower resolution than intraoral film (decreased detail)
  • Only objects in the focal trough can be clearly seen
  • Distortion
    a) overlapping teeth
    b) magnification and minification (we can’t use it to get accurate measurements of structures)
    c) objects outside of the focal trough will appear blurred
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5
Q

How panoramic radiographs work?

A

Utilizes principles of scanography:
- slit-shaped collimator is used to produce a thin moving beam of x-rays that scan different parts of an object onto a moving film/receptor

Utilizes principles of tomography:

  • imaging of a layer or section of the body by intentionally blurring images of structures in other planes
  • during exposure, the x-ray source and film move in synchronized movement parallel to each other in opposite directions
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6
Q

Position of panoramic x-ray tubehead

A

Negative angle (approximately - 10”) to allow beam to pass under the occipital bone

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7
Q

of collimators for panoramic x-ray

A

2 collimators:

- 1st at the source
- 2nd between the image receptor and object
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8
Q

Type of collimators used in intraoral x-ray units

A
  • Round or rectangular x-ray collimator

- Projected beam slightly larger than the receptor

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9
Q

Thickness of focal trough

A
  • Anterior teeth is thin, while posterior is thick.

- Key: thicker focal trough, more tolerant of slight changes in positioning (better for posteriors than anteriors)

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10
Q

Center of rotation principle as used by Panorex machine

A

COR would create two arcs, halfway through the process the patient would shift over

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11
Q

of COR

A

Divides the arch into 3 segments:

  • Condyle to 1st premolar
  • Canine to canine
  • Contralateral condyle to 1st premolar
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12
Q

Appearance of structures outside focal trough

A

Blurred

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13
Q

Appearance of structures within focal trough

A

Clear

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14
Q

Position of the patient during panoramic radiograph

A
  • Patient needs to be relatively still to minimize distortion
  • Bite block is there to position dental arches in correct spot when machine takes radiograph (central incisors bite on this)
    - special chin rest for edentulous patient
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15
Q

How will structures appear when placed closer to film during panoramic radiograph?

A

Smaller and more clear

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16
Q

How structures appear when placed farther from the film during panoramic radiograph?

A

Projected image gets magnified

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17
Q

Correct way to position the aprons during a panoramic radiograph

A

High in front, low in back

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18
Q

Position of tongue while panoramic radiograph is being taken

A

Tongue has to be kept against the hard palate to reduce the glossopharyngeal airspace.

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19
Q

Proper appearance of occlusal plane on a panoramic radiograph.

A

Should look like a smile line.

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20
Q

What happened during panoramic x-ray: anterior teeth look big and wide?

A

Patient was positioned too far back.

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21
Q

What happened during panoramic x-ray: anterior teeth look small and narrow?

A

Patient was positioned too far forward.

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22
Q

Position of anterior midline/midsagital plane in panoramic radiograph…

A

Centered and perpendicular to the floor

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23
Q

Position of posterior midline in panoramic radiograph…

A

Combination of the two ends of the radiograph.

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24
Q

What are real/true images?

A
  • Single images
  • Double images

Formed when the object is radiographed between the COR and the film.

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25
Q

Common double images

A

hyoid, hard palate, epiglottis

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26
Q

What is a double image?

A
  • 1 structure scanned twice
  • between COR and receptor
  • not extremely blurred
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27
Q

What are ghost images?

A

Reflected images of a structure located between the x-ray source and the COR.

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28
Q

Common ghost images

A
  • L and R markers form machine
  • Mandibular rami
  • Earrings
  • Cervical vertebrae
  • Hyoid bone
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29
Q

Characteristics of ghost images

A

1) Appears on opposite side of real image.
2) Appears superior to or above real image.
3) Appears magnified.
4) Appears fuzzy or distorted.
5) Vertical dimension appears larger/blurred out, horizontal component may or may not be magnified.

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30
Q

Source of horizontal component of panoramic radiograph magnification…

A

COR

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31
Q

Source of vertical component of magnification for panoramic radiograph…

A

tubehead –> distance is constant –> less vertical magnification

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32
Q

Position of Frankfort horizontal plane during panoramic radiograph…

A

Parallel to the floor (auriculo-orbitale)

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33
Q

Position of spinal column during panoramic radiograph…

A

Straightened, especially cervical portion

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34
Q

Observed when patient is too far forward while taking panoramic radiograph…

A
  • blurred and narrow anterior teeth

- double image of cervical spine, superimposed over rami (different from gazebo effect)

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35
Q

Observed when patient is too far back while taking panoramic radiograph…

A
  • blurring and widening of anterior teeth

- ghosting of rami and spine

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36
Q

Observed when chin is too far down while taking panoramic radiograph…

A
  • accentuated smile line
  • “V” mandible
  • double image of spine, “gazebo effect”
  • blurred mandibular anterior roots
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37
Q

Observed when chin is too far up while taking panoramic radiograph…

A
  • flat/inverted occlusal plane
  • blurred maxillary anterior roots
  • hard palate superimposed on roots
  • broad and flat mandible
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38
Q

Observed when head twisted while taking panoramic radiograph…

A

Midline asymmetry:

  • Uneven width of rami
  • Uneven magnification of teeth
  • Uneven blurring

(BMW)

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39
Q

Observed when head tipped sideways during panoramic radiograph…

A
  • Unequal condylar height

- Distorted nasal structures

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40
Q

Observed when un-straightened neck while taking panoramic radiograph…

A
  • Accentuated cervical spine ghosting
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41
Q

Observed when tongue not against palate while taking panoramic radiograph…

A

(palato-glossal or glossopharyngeal airspace)

Airspace shadow over maxillary roots and rami

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42
Q

Observed when patient moved while taking panoramic radiograph…

A
  • Blurred areas

- Large step defects in inferior border of mandible

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43
Q

Suggested order of interpreting panoramic radiographs…

A

Cortical borders of bone –> medullary bone –> internal structures (foramina and canals) –> airspaces –> shadows –> teeth

Generally speaking: bone –> airspace –> soft tissue –> teeth

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44
Q

Difference between fracture and movement artifacts on a panoramic radiograph…

A

Radiolucent lines indicate (mandibular) fracture

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45
Q

What is ectodermal dysplasia?

A

Group of syndromes deriving form abnormalities of the ectodermal structures: hair, nails, skin, sweat glands, etc.

Dental anomalies:

  • Peg-shaped or pointed teeth
  • Congenitally absent teeth
  • Defective enamel
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46
Q

What is cherubism?

A
  • genetic disorder
  • prominent inferior 1/3 of face
  • loss of mandibular bone replaced by fibrous tissue
  • premature loss of primary teeth and uneruption of permanent
  • Large radiolucent areas within the ramus, body, angle, coronoid process, and maxilla
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47
Q

What is dentin dysplasia I?

A
  • Genetic disorder
  • Enamel is normal, but dentin is atypical
  • Abnormal pulpal morphology
  • Type 1 (coronal) and type II (radicular)
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48
Q

What is Gardner’s syndrome?

A
  • AKA familial colorectal polyposis

- Oral manifestation is multiple unerupted supernumerary teeth, odontomas, and osteomas.

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49
Q

What is florid cemento-osseous dysplasia?

A
  • Benign condition of the jaw
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50
Q

What is a large ameloblastoma?

A
  • Benign, slow-growing aggressive tumor of the odontogenic epithelium
  • More common in mandible
  • Rarely malignant or metastatic
  • Invades adjacent structures
  • May cause severe facial asymmetry
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51
Q

Biological interactions of ionizing radiation:

A
  • Direct

- Indirect

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52
Q

What is direct action of radiation?

A
  • When energy of a photon or secondary electron ionizes biologic macromolecules (radiation affects macromolecule directly) –> produces free radical
  • Accounts for 1/3 of the radio-chemical effects
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53
Q

What is indirect action of radiation?

A
  • Radiation (photon) absorbed by water which then causes radiolysis of water (ionizes water) –> produces a free radical
  • Free radical can then go on to affect other molecules
  • Accounts for 2/3 of the radio-chemical effects
    • makes sense since most of the body is comprised of water
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54
Q

What is the principle radiation interaction with the body?

A

Indirect (about 2/3)

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55
Q

What are free radicals?

A
  • uncharged molecule containing a single unpaired electron in the outer shell
  • highly reactive and unstable
  • capable of diffusion through the cell and interaction at a distant site
  • excess energy can be transferred to other molecules to disrupt bonds and produce point lesions
56
Q

What can OH radicals form?

A

Hydrogen peroxide, which is poisonous to the cell and therefore acts as a toxic agent.

57
Q

What can H free radicals form?

A

Can react with O2 to form hydroperoxyl.

58
Q

Principle damaging products following radiolysis of water?

A
  • Hydroperoxyl

- Hydrogen peroxide

59
Q

What can hydroperoxyl free radicals form?

A

Hydrogen peroxide

60
Q

Trickle down effect of radiation injury:

A

Radiation affects the body on an atomic level –> ionizes atoms into free radicals –> affects the function of molecules –> affects function of cell –> affects function of tissue –> affects organ –> ultimately affects the body as a whole of the individual

61
Q

Define deterministic effect of radiation

A

Radiation injury that results in killing of large number of cells.

62
Q

Define stochastic effect of radiation.

A

Sublethal damage to individual cells that result in cancer formation or heritable mutations

63
Q

Characteristics of stochastic effect of radiation injury.

A
  • Risk is proportional to dose
  • Implies no threshold
  • Severity of the effect is independent of the dose
64
Q

Characteristics of deterministic effects of radiation injury

A
  • Severity is proportional to the dose
  • There is a threshold
  • Do not occur as a result of normal dental radiologic examinations
  • EX: harmful tissue effects, in-utero birth defects, cataracts, radiation burns on skin
65
Q

Radiation is especially damaging on what type of cells…

A
  • Rapidly dividing cells
  • Irradiation of such cells cause reduction in size of tissue, mitotic delay, reproductive death, or loss of capacity for mitotic division
66
Q

Effects on cell replication (deterministic effect)

A
  • DNA Damage: chromosome abberations
  • Apoptosis: programmed cell death
  • By-stander effect: un-radiated cells exhibit irradiated effects as a result of signals received from irradiated cells
67
Q

Types of DNA damage (deterministic effect)

A
  • Single stranded DNA break: of little consequence, can be repaired using intact strand
  • Double stranded DNA break: disrupt H-bonds between strands, cause unwanted cross-linking within helix, and change or loss of base
    - cause majority of the damage
68
Q

Mild mitotic delay induced by….

A

low dose of radiation

69
Q

G2 block in cell cycle and some cellular death caused by…

A

moderate dose of radiation

70
Q

Effect of radiation on oral mucous membranes

A
  • Mucositis: inflammation of mucous membranes
  • Can result in pseudo membrane formation: loosely adherent necrotic epithelium
  • Pain and discomfort may be present
  • Changes in oral flora –> candida infection
  • Fibrotic reparative reaction
71
Q

Effects of radiation on teeth

A
  • Growth retardation
  • Destroys tooth buds if irradiation proceeds calcification
  • Agenesis of teeth/retarded root development
  • Adults less prone to direct effects
72
Q

What are radiation caries?

A

Type 1. widespread and superficial caries
Type 2. caries of the cementum and dentin at cervical region
Type 3. dark pigmentation of entire crown

** may exist in combinations

73
Q

Effects of radiation on taste buds:

A
  • extensive degeneration of taste acuity, decreases by a factor of 1K - 10K
  • higher than normal concentrations needed to elicit taste response after being subjected to three weeks of radiotherapy
74
Q

Effects of radiation on salivary glands

A
  • Parenchyma becomes more sensitive
  • Parotid glands > submandibular and sublingual
  • Decreases salivary flow or completely inhibit it due to loss of acini –> increase in strep mutans and lactobacillus –> increase in caries
  • Can return to normal in 6-12 months
75
Q

Indications for hyperbaric oxygen

A
  • Carbon monoxide poisoning
  • Decompression sickness (for divers)
  • Air or gas embolism (HB Oxygen reduces size of air)
  • Adjunctive therapy for radiation tissue damage –> soft tissue osteoradionecrosis
  • Clostridial myonecrosis (bacterial infection gas in tissues gangrene or necrosis)
76
Q

Purpose of hyperbaric oxygen

A

Helps restore O2

77
Q

What is osteoradionecrosis?

A
  • Soft tissue and bone necrosis due radiation making the area hypocellular, hypovascular, and hypoxic
  • Mandible more susceptible
  • Can become infected
  • Appears similar to osteomyelitis
78
Q

Radiation effects on skin…

A

Redness, dryness, itchy, peeliing, or blistering

79
Q

What is radiation dermatitis?

A
  • Radiation induced dermatitis
  • Generally manifests itself within a few days to weeks after the start of radiotherapy
  • Onset depends on radiation dose intensity, sensitivity of individual to radiation
80
Q

4 modifying factors…

A

1) dose: damage increases with dose; there is a minimum dosage required to see deterministic effects
2) dose rate: rate of the exposure; high dose rate causes more damage
3) oxygen content: damage goes up with oxygen content because of indirect radiation through free radicals
4) linear energy transfer: how much energy the particle releases per distance

81
Q

______ linear energy transfer (LET) is bad

A

high

82
Q

X-rays are considered _______ linear energy transfer (LET)

A

Low

83
Q

Relative biologic effectiveness (RBE)

A
  • quantification of the ability to produce biologic damage
  • As LET increases, RBE increases
  • Maximum level of RBE can be reached due to overkill
84
Q

Oxygen enhancement ratio (OER)

A
  • Inverse relationship with LET: OER is high for low LET, decreases as LET increases
  • Tissue is more sensitive to radiation the more O2 it has
85
Q

Sensitivity to radiation vs age

A
  • highest while still developing (most sensitive before birth)
  • lowest as adults
  • in old age, sensitivity increases again
86
Q

What is doubling dose?

A
  • A way to measure the risk from genetic mutations from exposures
  • the amount of radiation a population requires to produce in the next generation as many additional mutations that may arise spontaneously
87
Q

Type of radiation matters…

A
  • If applying same dose of alpha and beta particles, alpha particles will do more damage.
  • If applying the “dose equivalent” of each, same damage will be done.
88
Q

Dose equivalent

A
  • standard of comparison based on the amount of damage that type of radiation does
  • a scaling unit multiplied by the absorbed dosage to compare the RBE of two different means of radiation
89
Q

Damage factors

A
  • Part of the body that’s exposed: extremities can handle more radiation
  • Age of the individual
  • Biological differences: sensitivity of individual to radiation
90
Q

Types of radiation

A
  • Particulate: alpha and beta particles

- Electromagnetic: combination of electric and magnetic waves, photons, gamma radiation

91
Q

What are alpha particles?

A
  • Helium nucleu

- High LET

92
Q

What are beta particles?

A
  • high energy electrons

- Low LET

93
Q

Penetration abilities of alpha particles

A
  • travel an inch in air
  • stopped by a sheet of paper
  • not an external hazard, but can cause tissue damage if they get into the body
  • more damaging than beta particles
94
Q

Penetration abilities of beta particles

A
  • travels anywhere from inches to many feet in the air
  • stopped by a layer of clothing or less than an inch of a substance
  • can cause skin injury, but alpha particles are much more dangerous
95
Q

Penetration abilities of gamma particles

A
  • Travels many feet in the air, many inches in human tissue
  • Stopped by inches to feet of concrete or less than an inch of lead
  • Damaging to tissues externally and internally
  • Most damaging
  • Emitted from nucleus of some unstable radioactive atoms
96
Q

_________ radiation = high LET

A

Particulate, high

  • direct action
  • damages DNA directly by breaking bonds
97
Q

_________ radiation = low LET

A

Electromagnetic

  • indirect action (2/3 of the time)
  • damages DNA indirectly via radicals and reactive molecules
98
Q

What’s radiosensitivity?

A
  • Relative susceptibility of cells, tissues, organs, organisms, or other substances to injury via radiation.
  • Directly proportional to rate of cell division, and inversely proportional to the degree of cell differentiation
  • Actively dividing cells, or those not fully mature are most at risk
99
Q

The following are more radiosensitive…

A
  • high division rate
  • high metabolic rate
  • non-specialized (undeveloped)
  • cells that are well nourished
100
Q

Effective dose

A
  • allows the risk from exposure from one body region to be compared to risk to another region
  • estimates the risk in humans; measures equivalent whole body dose
101
Q

How to reduce patient exposure…

A
  • use rectangular collimators
  • use a 16” position indicating device (PID)
  • film selection
  • ALARA: as low as reasonably achieved
102
Q

Radiation projection goals

A
  • Prevent deterministic effects

- Minimize stochastic effects

103
Q

Caries formation requires…

A
  • bio-film (plaque)
  • fermentable carbohydrates
  • tooth surface
104
Q

Bacteria believed to be responsible for the majority of cavities in teeth.

A

Streptococcus mutans

105
Q

Stephan Curve

A

When fermentable carbohydrates are present - lead to the dissolution or demineralization of hard tissues and lactic acid is produced by bacteria and diet. pH is lowered to 5.5

106
Q

Disease indicators for caries progression

A

The following lead to low pH -> caries progression:

  • white spots
  • restorations < 3 years
  • enamel lesions
  • cavities/dentin
107
Q

Risk factors for caries

A
  • bad bacteria
  • absence of saliva
  • dietary habits (poor)
108
Q

Protective factors against caries

A

The following contribute to health pH -> no caries:

  • saliva & sealants
  • antibacterials
  • fluoride
  • effective diet
109
Q

Prevalence

A

the total number of cases at point in time divided by the population at

110
Q

Incidence

A

number of new cases of a disease or condition in a specified time period usually a year divided by the persons at risk

111
Q

Steps to caries progression:

A
  1. Precavitated lesion (white spot) - demineralization (may be seen radiographically)
  2. Cavitation of enamel
  3. Decay reaches DEJ
  4. As decay progresses through dentin, we see a “double arrow” radiolucency
  5. Decay reaches pulp
  6. Decay progresses apically
112
Q

Radiology of dental caries

A

Caries –> demineralization –> less attenuation of x-ray beam –> more photons hit the film –> dark area on film

113
Q

Frequency of bitewing examination depends on:

A
  • Age
  • Medical condition
  • Medications
  • Diet
  • Oral hygiene
  • Prior caries history (most common predictor of current caries
114
Q

Optimal viewing conditions for (bitewing) radiographs:

A
  • Masking borders with a dark mount
  • Bright, even illumination
  • Dim, indirect room light
  • Bitewings should have proper contrast and clear non-overlapped interproximal contacts
115
Q

Timeline of caries progression

A
  • Microscopic –> no radiographic evidence
    18 months (+/-6)
  • “White spot” –> may be seen radiographically
    ~ 24 months
  • Cavitation –> clearly evident
116
Q

White spot lesions can progress in one of two ways:

A

1) undergo partial remineralization (will appear less white and smoother)
2) in-tact surface can break and become a cavity

117
Q

A minimum of __% demineralization must occur before the lesion can be seen on a film-based radiograph. Digital radiographs are in the __-__% range.

A

60, 50-55

118
Q

Carious lesions usually form a ______ shape.

A

Triangular/cone

Note: tip does not show up that well; radiographs underestimate lesions; triangular shape with the broad base at the tooth surface
Technical note: geometry of the lesion changes the signal to noise ratio across the mesio-distal dimention of the lesion

119
Q

Which radiographs are best for caries detection?
Bitewings = ???
Periapicals = ???
Panoramic = ???

A

Bitewings –> proximal and occlusal caries in the posterior teeth
Periapicals –> proximal caries of anterior teeth
Panoramics –> occlusal caries

120
Q

Define:

  • True positive
  • True negative
  • False positive
  • False negative
A 
True positive (TP): diagnosed as having disease, and the patient does indeed have the disease
True negative (TN): diagnosed as not having disease, and the patient indeed does not have disease
False positive (FP): diagnosed as having disease, when patient does not have disease
False negative (FN): diagnosed as not having disease, when patient does have disease
121
Q

Sensitivity

A

Percentage of people who are correctly diagnosed with the disease with respect to the total number of people who actually have the disease in the population

TP/(TP+FN)

122
Q

Specificity

A

Percentage of people who were correctly diagnosed as NOT having the disease with respect to all individuals without disease

TN/(FP+TN)

123
Q

Purpose of receiver-operating characteristic (ROC) curves

A
  • help decide where to draw the line between “disease” and “no disease”
  • Graph:
    - overlap indicates where test cannot distinguish normal from disease
    - below cutoff we consider test to be normal
    - above cutoff we consider test to be abnormal
124
Q

Film speed is controlled by…

A
  • Size of the silver halide crystals
    - bigger crystals = faster speed

Note: F speed film is fastest since larger halide 1/2 exposure needed
Note: PSP or digital intraoral receptors require less radiation than film; current PSP allows for 50% dose reduction in comparison to F speed film

125
Q

Progression of caries into dentin

A
  • At DEJ, lesion broadens along junction
  • Apex points toward the pulp
  • Lesion progresses toward the pulp along dentinal tubules

Zone of necrosis decomposed dentin –> zone of bacterial invasion –> zone of dimineralized dentin –> hypermineralized sclerotic dentin –> tertiary dentin inside original pulp space

126
Q

Occlusal caries

A
  • common in children and adolescents
  • starts in pits and fissures
  • enamel portion of occlusal lesion may not be seen on a radiograph
  • dentinal portion usually below a fissue
  • buccal pit or buccal pit caries may be superimposed and be mistaken for occlusal caries <– clinical exam will help to differentiate
127
Q

Root caries

A
  • Occurs on exposed root surface –> associated with gingival recession
  • Can be confused with cervical burnout
    - Cervical burnout extends from height of bone to CEJ
    - Caries will efface the proximal surface of the root and have more diffuse inner borders
  • Can be very difficult to treat
128
Q

Proximal lesions

A
  • located between contact area and gingival margin

- important to distingish between caries and cervical burnout

129
Q

Cervical burnout & Mach Band effect

A
  • Extends from height of bone to CEJ
  • Mach band effect: optical illusion –> area appears more radiolucent because there’s a sharp contrast between enamel and dentin
    • Can contribute to a false positive reading and unnecessary restoration of sound tooth structure
130
Q

Caries detector devices

A
  • Logicon: computer aided radiology
  • Transillumination & Kavo Diagnocam: enhanced visual examination
  • Diagnodent: Ultrasound surface analysis
  • Spectra caries detector
131
Q

What does the logicon caries detector do?

A
  • Takes a picture –> analyzes contours of the tooth –> extracts density and spatial information to produce a tracing of radiolucent sites
132
Q

What does the DIAGNOdent laser do?

A
  • laser light excites fluorescence in bacterial pigments such as porphyrins
  • specifically designed for occlusal caries
  • does not read demineralization itself
133
Q

What types of caries can be detected clinically?

A

Buccal, lingual, occlusal

134
Q

Only __% of lesions actually progress beyond the enamel.

A

50

135
Q

What are spectra-air techniques?

A
  • Takes picture of occlusal surface
  • Enables precise localization of caries using a numerical and color scale
  • Uses PC to display and analyze images
136
Q

What is KavoCam?

A

Produces image that is generated without x-ray.

Shows coronal tooth structures above gingiva in detail.

Complete Dentures 1 (6 decks)

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