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radio paper Flashcards

1
Q

what does a PA capture

A

shows the indiv teeth and tissue around the pices (at least 3mm)

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2
Q

what do PAs help to assess

A
  • apical status
  • severity of careis
  • perio status
  • presence and posn of unerupted teeth
  • posn of 8s
  • root morpho
  • endo tx
  • post op review
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3
Q

2 techniques of taking PAs

A

bisecting angle technique - beam is angulated at bisecting angle of tooth axis & receptor
parallel technique - place receptor parallel to tooth axis, aim beam parallel to receptor

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4
Q

what does a BW capture

A

crowns, interprox, ocl surface, EDJ, alveolar crest bone lvl

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5
Q

what are BW used for

A

detection & monitoring caries
assess resto
assess perio status

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6
Q

what collimator do ocl xrays need

A

round collimators

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7
Q

what are OPGs used for

A 
overall eval of dentition
demonstrate extensive caries / perio
eval posn of 8s
dvlpt disturbances of mxfacial skeleton 
trauma 
intraosseous patho 
tmj
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8
Q

what to take note for taking OPGs

A 
remove jewellery, hair pins, glasses, RPs 
no preggo
explain procedure to pt
put on lead apron 
correct exposure setting
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9
Q

what is tomography

A

xray source and receptor rotate simultaneously in opposite direction around a fixed centre of rotation

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10
Q

for OPG, where does xray source come from

A

comes from the back, angulated slightly upwards by 8deg

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11
Q

OPG magnification is due to…

A

pt positioning too far back

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12
Q

OPG minification is due to…

A

pt positioning too far forward

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13
Q

OPG chin tilt too up/down leads to…

A

v shaped / broad and flat

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14
Q

layers of xray film structure

A

overcoat (protection)
emulsion (Ag halide crystals)
base (support)

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15
Q

how are latent images formed on xray film

A

Ag halide suspended in gelatin matrix that contain sensi specks.
Ag halide is ionised, forms Ag+ and e-, diff areas experience diff degree of ionising.
sensi specks traps Ag+ and e- to form latent image.

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16
Q

how are latent image processed?

A

dvlp soln - reduce Ag+ into black Ag

fixer soln - remove unexposed Ag halide

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17
Q

what do intensifying screens do

A

active phosphor layer emits light when exposed to xray beam, amplifies incoming xray beam while reducing pt dose. but comes at a cost of lower resolution of film

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18
Q

process of digital imaging

A

xray photon reach receptor to form latent image
image go through electronic detector to translate qty of xray photons into voltage signal
voltage signal is sampled and quantified
computer display image/shade of grey based on value assigned

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19
Q

how image formed on psp plate

A

xray cause e- to move from valence band (resting state) to conduction band (excited state)
e- trapped in F centres = latent image
laser in scanners release e-, e- return to valence band and releases light while doing so
light converted into voltage
digitalised & displayed

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20
Q

properties of xray

A
  • electrically neutral
  • travels in straight lines
  • polyenergetic / heterogenic
  • absorbed / scattered by tissues
21
Q

which component of xray unit produces the xrays

A

tungsten anode head

22
Q

ft of xray unit to minimise excessive xray exposure

A
  • tube is made of metal, lined w lead
  • plastic port cover for xray to exit from one side only
  • appropriate exposure time
  • filtration to filter out low energy photons that don’t contribute to image formation
  • long collimator used to reduce dose, reduce scatter, restrict width of xray beam until just slightly bigger than film
23
Q

what are bremsstrahlung radiation

A
  • polyenergetic (forms the curve)

incident e- knock into atomic e-, path of incident e- is deflected bc it loses KE. KE lost = xray

24
Q

what are characteristic radiation

A
  • heterogenous energy lvl
    incident e- knock out k shell e- (inner), outer shell (L/M/N) e- drops to fill the space, excess energy = characteristic xray
25
Q

describe xray energy curve

A 
y axis - no. of photons (aka mAs)
x axis - photon energy (keV) 
kVp setting = max energy 
peak = average energy of photon beam 
spikes = characteristic radiation
26
Q

effect of increasing exposure time

A

more time = more photons hit film = increase density of image (image becomes more gao)

27
Q

effect of increasing filtration

A

filtration = remove useless low e photons
curve shift down (qty overall decrease)
curve shift right (ave e increase)
hence lower contrast & density

28
Q

what is attenuation

A

when xray interacts with matter

29
Q

what are the 3 ways xray interact w matter

A
  1. coherent scattering - photons hit atoms causing atoms to vibrate and emit energy in a different direction. least harmful, least fx on film
  2. photoelectric absorption - all of incident photon energy absorbed by inner shell e- and is ejected. outer shell e- fills the vacancy and excess energy is emitted as characteristic photon. potential for bio damage bc of ionisation. more likely to occur in matter w high atomic no. (e.g. bones>lungs) hence leading to differential absorption
  3. compton scattering (MAJORITY) - incident photon knock out e-, excess energy exit atom as a photon. caused by high kVp and results in low contrast. potential for bio damage & scatter radiation that projects onto film as radiation fog
30
Q

a round collimator PA equivalent to how much bg radiation?

A

2.5 days of bg radiation in sg.

pano dose = lat ceph dose x3

31
Q

what is the law of Bergonie & Tribondeau

A

The radiosensitivity of a tissue is directly proportional to mitotic activity and inversely proportional to degree of differentiation of its cells
–> aka young ppl are more sensitive to radiation risks

32
Q

stochastic vs deterministic bio fx of radiation?

A

stochastic: risk is proportional to dose, severity is independent of dose (no threshold). more xrays exposed = higher chance of developing something.
deterministic: severity is proportional to dose. above a certain threshold you will get it.

33
Q

explain LNT

A
  1. x axis = level of radiation dose y axis = addition health risk due to radiation exposure
  2. black dots represent specific epidemiological data (mostly high radiation doses)
  3. no data present at low risk, so assume straight line to be extrapolated to 0
  4. this theory explains higher dose higher risk, no threshold bc risk is present at any exposure level
34
Q

what efforts done to ensure ALARA

A
  • lead apron, thyroid collar
  • filtering, collimator
  • high speed film
  • long xray tube
  • holders for accuracy ( no need retake )
  • appropriate exposure time for each xray
35
Q

what are the 3 principles of radiation protection

A
  1. principle of justification (benefit > risk)
  2. principle of optimisation (alara)
  3. dose limitation (reach max cap?)
36
Q

what is pt selection criteria

A

Selection criteria = a framework used to decide whether xray should be taken. This framework ensures benefit > risk, and is individualized to each person

  • Minimize xray exposure
  • decrease probability of stochastic fx
  • Prevent deterministic fx
37
Q

layers of carious lesion

A 
DIDSR
zone of destruction 
bacterial invasion 
zone of demin
zone of sclerosis 
reactionary dentin
38
Q

classification for interprox caries

A 
r0= no radiolucency 
r1= outer half of enamel
r2= to inner half of enamel, not cross into dentin
r3= cross into outer half of dentin 
r4= into inner half of dentin
39
Q

3 types of AI and their defining ft

A

hypoplastic - rough pitted appearance. thinner enamel.
hypomaturation - brown sensi soft teeth. enamel thickness normal. dentin enamel same density
hypocalcified - chalky appearance, enamel thickness normal but softer (bc less mineral content). enamel lower density than dentin

40
Q

defining ft of DI

A

gray blue / yellow brown teeth
short worn down crown, low contrast btwn layers

DI 1 - occurs in ppl w OI
DI 2 - no OI. short worn down bulbous crowns

41
Q

2 types of dentin dysplasia and their defining ft

A

normal enamel abnormal dentin, abnormal pulp (pulpal obliteration)
extreme tooth mobility
1 - roots dont dvlp properly
2 - hypertrophic dentin (rare)

42
Q

turners hypoplasia

A

EH only on 1 tooth, due to trauma on pri tooth

43
Q

what to consider for pt selection criteria

A
  • Dvlpt of dentition
  • Caries risk
  • Type of pt (new/recall/other indications upon clinical exam)
  • Consider both dental and general health needs
  • Must xray be done now?
  • What type of xray most beneficial
44
Q

compare AI
hypoplastic
hypomatured
hypocalcified

A

hypoplastic - rough pitted appearance
hypomatured - brown
hypocalcified - chalky

45
Q

attrition

A

tooth against tooth

46
Q

abrasion

A

tooth against non tooth (e.g. toothbrush)

47
Q

how many PAs required for full mouth?

A

10

48
Q

3 biological factors that affect radiosensitivity of cells

A
  1. cell metabolic rate
  2. cell mitotic rate
  3. cell differentiation/specialisation

radio (1 decks)

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