lectures combined Flashcards
(223 cards)
1
Q
what is a radiograph?
A
an image produced by X-rays passing through an object and interacting with the photographic emulsion on a film /affect sensor or phosphor plate.
2
Q
why are radiographs useful in dentistry?
A
allow you to look inside the body and diagnose caries/perio
3
Q
what is an atom composed of?
A
protons with a positive charge and electrons with a negative charge which orbit the nucleus in different energy shells (K,l,M,N,O)
4
Q
how do electrons move?
A
in predetermined shells with different energy levels (k:2, L:8, M:18, N:32, O:50) can move from shell to shell but cant exist between them (forbidden zone). energy is required to remove electrons from atom and overcome binding energy which keeps it in its shell.
5
Q
atomic number
A
Z protons
6
Q
neutron number
A
N neutrons
7
Q
atomic mass number
A
A=N+Z
8
Q
isotopes
A
atoms with same atomic number but different neutron number
9
Q
radioisotopes
A
isotopes with unstable nuclei which undergo radioactive disintegration
10
Q
ion
A
charged atom molecule electron number isnt the as the proton number. anion- negative charge with more electrons cation- positive charge with more protons
11
Q
alpha particles
A
2 protons and 2 neutrons large positive slow penetrate 1-2mm in tissue energy- 4-8MeV damage potential: extensive ionisation
12
Q
Beta particles
A
fast electrons small negative penetrate 1-2cm energy 100KeV-6MeV damage potential: ionisation
13
Q
gamma rays
A
electromagnetic radiation no size/charge very fast can pass through tissue energy: 1,24KeV-12.4MeV damage potential- ionisation
14
Q
x-rays used in dentistry
A
dont occur naturally not involved in radioactive decay identical to gamma rays- not such high energy not particulate no charge very fast cause ionisation
15
Q
ionisation
A
process by which atoms or molecules acquire a negative or positive charge by gaining or losing an electron from ions.
16
Q
domestic electricity
A
220/240 volts 50hertz 13amp current fused at 3,5 or 13amps cookers- 30amp
17
Q
voltage
A
si unit is volt potential difference/electrical force 1 volt= potential difference between 2 points on a conducting wire carrying a consistent current of 1amp when the power between the point is 1 watt
18
Q
basic circuit
A
current passed along wire by vibration of electrons passes from -ve to +ve
19
Q
lucent
A
dark/black as xray passes through
20
Q
opaque
A
light/black
21
Q
when is ionisation a problem?
A
it occurs in living cells can cause damage to tissues i.e cateracts can cause damage to dna directly or produce chemicals that do damage
22
Q
what is the electromagnetic spectrum?
A
stream of photons that have no mass and travel at the speed of light
23
Q
what happens when electricity flows through coils of elements?
A
electrons within the wire coils vibrate, electricity passes through the whole length of the coils vibrating electrons produce heat,wire becomes hot giving off light radiant heat causes the movement of air molecules. heat is proportional to current.
24
Q
3 intra oral xray types
A
periapical, bitewing, occlusal
25
6 types of extra oral xrays
dental panoramic tomogram lateral cephalogram postero-anterior mandible reverse lateral oblique mandible occipto mental
26
why would you take a radiograph?
- detect apical inflammation/ infection to include cystic changes - assess periodontal problems - trauma, fractures to tooth and bone - tooth morphology pre extraction - presence/position of unerupted teeth - endodontics -pre/post apical surgery - evaluation of implants
27
describe the paralleling technique
- holder - receptor parallel to tooth - accurate/reproducible image - X-ray beam perpendicular to tooth/receptor - minimises magnification
28
what is the holder made up of?
bite block- retains receptor an indicator arm/rod- fits into bite block aiming ring- aligns collimator and receptor anterior (blue) posterior(yellow)
29
what does the receptor consist of?
film parallel to long xis of the tooth (vertical) or parallel to arch (horizontal)
30
how should the vertical plane of the film be positioned?
parallel to the long axis of the tooth/teeth.
31
how should the horizontal plane of the film be positioned?
parallel to the dental arch under examination
32
how should the x-ray tube be positioned?
x-ray beam at right angles to tooth/receptor
33
what affects image size?
xray source (focal spot) to receptor distance anf object (tooth) to receptor distance
34
how can magnification be reduced?
- move x-ray tube away - move receptor closer
35
what are barriers to good positioning?
mouth size gag reflex film size digital sensor size and shape
36
indications for film size
bitewing: adult- 2 only child- 10+ 2 under 10 0/1 periapical: child- 0 adult- anterior 0/1/2 posterior 2 only
37
how can film be orientated
dot: periapical- towards crown bitewing- towards palate
38
describe bisected angle technique
no holder, operator dependent
39
what are the main components of the xray tube?
tubehead collimator positioning arms control panel circulating oil
40
what are the main components of the tubehead?
glass xray tube: filament, copper block, target step up transformer (high kV across xray tube) step down transformer (low filament mA) glass lead shield oil aluminium filler collimator beam indicating device or spacer cone
41
how are xrays produced?
- small electric current passed through filament 8-10mA - needs to have passed through a step down transformer - filament heated by current current due to excitation of electrons within wire - electrons lost from outer shell - free electrons surrounding the filament = electron cloud - large potential difference applied between cathode and anode - step up transformer changes 240v to 50.9kV -focusing cup points electrons towards target/focal spot of anode - -ve charged electrons attracted to +ve charged anode - pulled across by high kV between cathode and anode - 99% heat 1% xray - heat absorbed by copper - xrays radiate in all directions - most absorbed by leaded glass - target directs xray towards unleaded window.
42
what are the 2 types pf x-ray spectra?
1. Continuous spectrum - Bremsstrahlung or breaking radiation - Wide range of photon energies 2. Characteristic spectrum - Depends on material used in anode - Emitted by loss of electrons from K & L shells
43
what are properties of X-rays?
- travel in straight lines in free space - x-ray photons from a divergent beam - can travel through a vacum - penetrate matter - can be absorbed - can be scattered - not detected by human senses - produce latent image on film emulsion - cause ionisation - can cause biological damage - causes certain salts to florece and emit light.
44
scattering
random change in direction after hitting something
45
absorption
deposition og energy in issues
46
intensity
number of x-ray photons in a defined area of the beam
47
attenuation
reduction in intensity of beam due to scattering and absorption
48
ionisation
removal of electron from neutral atom to give -ve (electron) and +ve (atoms) ions.
49
what are possible interaction X-ray beam?
- completely scattered with no loss of energy - absorbed with total loss of energy - scattered with some absorption and loss of energy - transmitted unchanged
50
describe interactions of xrays at an atomic level?
- rayleigh (unmodified) scattering- pure scatter - photoelectric effect- pure absorption - compton effect- absorption and scatter - pair production - pure absorption
51
what is the photoelectric effect?
incoming electrons with K electron ejected with much energy . photoelectron undergoes further interactions x-ray photon has lost all energy and disappears inner shell vacancy filled from outer shell excess energy emitted as light or low energy xray free electron captured atomic stability and neutral state.
52
what is the compton effect?
incoming xray photon interacts with loosely bound outer shell electron. electron ejected with some energy from X-ray compton recall electron. compton electron can cause ionisation. remaining photon energy scattered may undergo further compton reactions or photoelectric reactions can escape tissues into clinical environment
53
what film types are used intra and extra orally?
intra: direct film, xrays can act directly on silver haldide crystals in film emulsion extra: indirect film, light from intensifying screens act on silver halide crystals in film emulsion.
54
what type of digital sensors are there?
solid state CCD or CMOS photostimulable phosphor
55
what are photostimulable phosphor plates?
PSP: phosphor coating on plates absorbs xrays scanned to release energy as light converted to image used with holder tolerated well
56
what are disadvantages of PSP
easily damaged expensive sensitive to background radiation
57
how does PSP work?
phosphor layer exposed to xray photons xray energy stored in the electrons of phosphor signals- latent image plate inserted into scanner phosphor layer scanned by red laser stored energy released as blue light light detected by photodetector and signal sent to digital-analogue to digital convertor ADC converts light to a digital signal- numerical value assigned to each pixel according to intensity of light detected - shades of grey plate has residual trapped energy in phosphor electrons after scanning image on plate erased by exposing phosphor to bright light.
58
describe CCD
xray hit scintillator layer that gives off light hits the photosensitive cells within silicon layer making up the pixels of the image. electrons are released within each cell and form a charge converted to a voltage giving an electrical signal to the computer that can be converted to an image
59
describe CMOS
similar to CCD photo cells are electrically isolated therefor charge to voltage signal is from each individual cell (pixel)and not lines of cells (pixels)
60
whats the difference between CCD and CMOS?
CCD possible better image quality - low noise and more pixels CMOS is cheaper to manufacture CCD more reliable CMOS uses less power CMOS- phone camera CCD-hig quality digital camera
61
digital advantages
no chemicals easy archiving easy image transfer image manipulation dose reduction
62
digital disadvantages
expensive damaged easily reduction in resolution due to pixel size security of image transfer image manipulation dose reduction
63
how are radiographs stored?
local server backup- CD, DVD, hard drive PACS: picture archiving and communication system scottish local and national PACS images stored within NHS tayside national archive- livingston
64
absorbed dose
measurement of the amount of energy deposited in a medium per unit mass Gray (Gy), /joules/kg
65
equivalent dose
H take into account the different rasio-biological effectiveness of different types of radiation sivert (Sv)
66
what does absorbed dose as weighting factor equal to
1
67
effective dose
absorbed dose x weighting factor (WR) converts dose to an equivalent whole body dose
68
radon
gas from uranium yearly 300mSV
69
gamma rays
emitted by natural radioactivity in earth/building materials yearly 350mSV
70
cosmic rays
dose increased with latitude and altitude average at ground 200microSV
71
What doseage is received from: a. Panoramic b. Periapical c. Chest X-ray d. CT head e. CT abdomen
a, 4-30 microSV b. 1-8.3 microSV c. 0.02msv d. 2 msv e. 8msv
72
Describe somatic deterministic effect of radiation
will occur above threshold dose acute: radiation sickness/ death chronic: hair loss, cataracts, sterility, obliterative endocarditis unborn: susceptive when organs developing 2-9 wks- malformation/death.
73
1. Describe non-deterministic somatic effects of radiation
may or may not occur- no threshold
74
effect of offspring of those irradiated (stochastic)
may damage DNA in sperm/egg may result in congenital abnormality
75
define radio sensitivity
cells with high mitotic rate, primitive differentiation lymphocytes/oocytes - highly differential and non dividing
76
describe direct effects of radiation
interacts with macromolecules i.e DNA, RNA, proteins and enzymes causing ionisation and damage.
77
describe indirect effects of radiation
damage to water hydrogen and hydroxyl free radical production by action of radiation to water free radicals can form toxic substances i.e hydrogen peroxide.
78
what changes in biological molecules is caused by radiation?
DNA damage to DNA primary mechanism for cell death, mutation and carcinogenesis: break strands loss/change of base disrupt bonds between stands repair occurs but if both strands broken close to each other there can be misrepair
79
Cancer risk for: a. Chest x-rays b. Head CT c. Inraoral d. Panoramic
a. 1 in 1000 000 b. 1 in 10 000 c. 0.06-0.7 in 1000 000 d. 0.29-1.9 in 1000 000
80
whats the difference in cancer risk for children?
young patient with dividing cells more radiosensitive with larger life span over which effects can develop
81
3 principles of radiation protection?
justufication: benefit from examination must outweigh the determinent from exposure optimisation: for each exposure the operators ensure that the dosese arising from the exposure are kept as low as resonably practicable and consistent with the inteded diagnostic purpose dose limitation: as low as reasonably practicable as low as easily achievable
82
describe inverse square law
intensity changes in inverse proportion to the square of the distance from the source
83
what are the indications of the controlled area?
protection within primary beam until it has been sufficiently attenuate by distance or shielding 1.5m of tube and patient size depends on kV of machine 1.5m for under 70kV
84
what warnings are put in place when taking radiographs?
visible light and noise when xray produced prevent access to controlled area control outwith controlled area
85
how is radiation monitored?
high workload \> 100 1:0 \> 50 panoramic per week
86
indications of lead protection
no justification for routine use of lead aprons for P.t in dentistry . thyroid collar worn in cases it may be in the primary beam. lead aprons dont protect against radiation scattered internally within the body.
87
when would you avoid radiographing a pregnant woman?
foetus most susceptible during organogenesis, enquire if pelvic area radiated.
88
what are the 4 components of the film packet?
outer plastic wrappings: protection from saliva/light, orientation- white side to tube black paper: protect from light leakage stiffens and supports film lead foil: lead and aluminiu, absorbs xrays, protects back scatter film
89
explain the film composition
direct action base- plastic (polyester) blue antiglare tint adhesive layer double emulsion protective layer of emulsion
90
describe emulsion
silver halide crystals suspended in gelatin silver bromide, iodine or combo gelatine allows the even distribution, absorbs liquid. adhesive layer sticks emulsion to base
91
describe image formation
direct action: xray photon hits silver halide crystals within emulsion and it becomes sensitised.
92
what is the latent image?
pattern produced within the emulsion by sensitising of the silver bromide/iodine crystals. not visible to naked eye seen by reducing crystals to black metallic silver.
93
what affects film speed?
dependent on size of crystals in emulsion larger the crystals faster the speed faster the speed lower the amount of xrays
94
how do indirect films work?
sensitised primarily to light light produced by intensifying screens inside cassette. light produced is in direct proportion to the xrays that hit the screens. reduces exposure required to produce image and therfore the dose received
95
what is the composition of an intensifying screen?
base- polyester reflective layer phosphor layer- fluorescent phosphors emit light when excited by xrays supercoat- protects phosphor layer
96
how is an indirect radiographic image formed?
xray photon hits phosphor crystal in intensifying screen. gives off light. light hits silver halide crystals within film emulsion. silver halide crystal becomes sensitised latent image.
97
how do you store and handle image receptors?
pressure sensitisesthe silber halide crystals handle film with care hold by corners/sides wet/dry emulsion is easily scratched. storage: cool/dry and away from radiation.
98
name 3 systems for film processing
automatic anual instant
99
describe automatic processing
consistent less operator dependent temperature controlled less chance to damage film
100
describe manual processing
very operator dependent temperature must be monitored time needs to be accurate
101
describe instant processing
chemicals in pouch attached to film very quick no large amount of chemicals to be disposed of convenient films don't archive well
102
describe the stages of processing
develop- make latent image available wash fix- make image permanent wash- remove residual fixer dry
103
describe developing
sensitised silver halide crystals are acted on by developing agents chemical reduction of silver bromide to silver and bromide black metallic silver
104
name the developing agent
phenidone and hydroquinone
105
name the activator
calcium carbonate (controls the activating of developing agents)
106
name the restrainer
potassium bromide (stops developer working on unexposed crystals)
107
name the preservative
sodium sulphate (slows down oxidation)
108
name the solvent
water
109
what are 3 important things in film processing
time: too long- dark too short- light temperature: too hot- dark too cold- light concentration: too strong- dark too weak- light
110
describe fixer
fixing agent charge unexposed halide to soluble compound so they can be washed away acid maintains the pH and neutralises the developer
111
name the cleaning agent
ammonium thiosulphate
112
name the acidifier
acetic acid (maintains pH)
113
name the hardener
aluminum chloride
114
name the preservative
sodium sulphate
115
name the solvent
water
116
what results from insufficient washing
film will feel tacky green/silvered appearance wont archive well
117
what does drying do?
ensures the film is dry before being handled reduces possibikuty of damage to emulsion
118
what are health and safety risks with developer
harmful limited evidence of a carcinogenic effect risk of irreversible effect may cause sensitisation by skin contact
119
define COSHH
COSHH- control of substances hazardous to health
120
what are health and safety risks with fixer
not hazardous corrosive can release sulphur dioxide or ammonia on contact with strong acid or alkali
121
why take bitewings?
detect caries monitor caries progression assess periodontal status assess existing restorations
122
what is seen in a horizontal bitewing?
distal of 4 to mesial of 8 pocketing less 6mm
123
what is seen in a vertical bitewing?
premolars and molars pocketing more than 6mm
124
outline the technique for taking bitewings
film and object parallel film to tooth distance as low as possible xray beam perpendicular to object and film dot to palate
125
describe the rigid plastic holder
holds film accurately assists xray tube positioning reproducible can be uncomfortable
126
describe paper tab holder
comfortable xray tube positioned by eye- not reproducible inaccurate chance of swallowing
127
film sizes
adult- 2 only child- over 10 : 2 under 10: 0/1
128
describe horizontal overlap
difficult to avoid, crowding/tilting of teeth acceptable if less than half enamel superimposed will miss early carious lesions must show ADJ
129
angulation
vertical angulation will distort caries position cusps separated- hint of angulation
130
what is the legal size of collimation?
90cm
131
when to take bitewings?
caries risk: high- 6mnths moderate- 12mnths low- 2yrs
132
what is quality assurance?
organised effort by staff to ensure that the diagnostic images produced are of sufficiently high quality to consistently provide adequate diagnostic information at the lowest possible cost and at the possible exposure to the patient.
133
how can human error be reduced?
introduction of simple systems improve working environment encourage reporting without blame.
134
what is quality assurance programme?
named person puts in writing: details of procedures involved frequency of procedures carried out frequency records will be audited
135
how is image quality rated?
all images produced are assessed and graded 1-3 collate results and analyse monthly, quarterly or 6 monthly results fed back to staff
136
describe an image rating of 1
excellent, no errors of p.t preparation, exposure , positioning, processing or film handling.
137
describe an image rating of 2
diagnostically acceptable some errors which do not detract from the diagnostic utility of the radiograph
138
describe an image rating of 3
unacceptable errors which render the radiograph diagnostically unacceptable
139
what are image quality targets defined as?
1\>70% 2\<20% 3\<10%
140
describe film reject analysis
collect all rating 3 films assess at the end of each month categorise faults act repeat monthly and compare results
141
how is xray equipment assessed?
equipment inventory must be kept tested regularly (min 3yrs) checks must include representative p.t doses routine maintenance anually
142
how are digital PSP stored?
cool and not too humid avoid direct sunlight and UV preferably in light protection/cross infection barrier envelope erased every 24hrs
143
describe sensitometry
daily check compress film processed with fresh chemistry with image produced as developer gets exhausted.
144
describe step wedge
stepwedge: radiographic phantom made from differing thicknesses of metal, place on film packet and expose
145
step wedge vs pre exposed
step wedge: cheap, operator variable and viewer dependent pre exposed: expensive easy to use no discrepancies in production not viewer dependent
146
what are common problems during film processing
damage due to: poor handling- bend/crimp insufficient training- overlapped light fogging- light entering daylight loading system/dark room safe light- filter unsuitable for film or too close
147
explain the coin test
♣ Open an intra-oral x-ray packet and remove film – while hands are inside glove box or in darkroom under safelight conditions ♣ Place a coin on the film ♣ Leave coin on film for a specified amount of time (five minutes or average working time) ♣ Remove coin and process film ♣ Check the processed film for light fogging ♣ Repeat test for every different type and speed of film used in the practice ♣ Act on your findings
148
how would you assess digital receptors?
computer monitors- check settings, resolution solid state sensors- visual check for physical damage and radiographic monitoring PSP- visual/radiographic
149
explain working procedures
IR(ME)R 200 employer must provide written procedures local rules written procedures for action that indirectly affect radiation safety or diagnostic quality e.g correct prep and use of chemicals
150
what is an audit?
systematic review/assessment
151
what does ALARP stand for?
as low as reasonably possible
152
how would you diagnose caries using radiographs?
\> Carious lesions can only be detected radiographically when there has been sufficient demineralisation \> must be distinguishable from enamel and dentine \> film must be well exposed and well processed \> optimum viewing conditions \> Correct view/projection must be requested \> knowledge of normal variants \> cannot tell whether lesion is active or arrested \> superimposition - a 2D image \> sensitivity of technique and observer skills \> Importance of clinical examination
153
what could be mistaken for caries?
cervical burnout/translucency- neck of tooth, enamel,root. visual perception- problems of contrast below metallic restoration air/lip shadow in premolar region dentine surrounding radio opaque zone under amalagam radiolucent restorations
154
what are limitations to caries diagnosis?
overlap technique anatomy exposure factors
155
technique for bitewings/periapicals
film parallel to long axis of tooth xray beam at 90 degres to film and tooth long cone used no more than half enamel superimposed to allow view of ADJ
156
describe paralleling techniques
geometry similar to bitewing accurate images positioning devices determine the angulations reproducible on different visits by different operators buccal palatal cusps as superimposed as possible
157
bitewings and caries diagnosis
interproximal and occlusal caries risk assessment
158
what is the trabecula pattern of the mandible and maxilla?
mandible- thick, close together, horizontally aligned maxilla- finer more widely space, no obvious alignment
159
what are the 3 most important features of the peri-radicular region?
1. radiolucent line- PDL space 2. radiopaque line- lamina dura 3. trabecula bone pattern and density surrounding bone
160
what is the radiographic appearance of initial acute inflammation
no apparent changes or possible widening of periodontal ligament space inflammatory exudate- swelling pushing the tooth upwards out the socket 0.5-1mm tooth non vital, spread into periapical region.
161
what is the radiographic appearance of the initial spread of inflammation?
loss of lamina dura at apex
162
what is the radiographic appearance of further inflammatory spread?
periapical bone loss-can be diffuse
163
what is the radiographic appearance of initial chronic inflammation?
no bone destruction seen or dense sclerotic bone periapically (sclerosing osteitis)
164
why take periapicals?
detect apical inflammation/infection to include cystic changes assess periodontal problems trauma tooth morphology pre extraction
165
why take periapicals?
detect apical inflammation/infection to include cystic changes assess periodontal problems trauma tooth morphology pre extraction presence/position of unerupted teeth endodontics pre/post apical surgery implant evaluation
166
Whats the difference between paralleling and bisected angle technique?
paralleling- holders used to facilitate positioning, film parallel to tooth, accurate/reproducible image bisected angle- can be done without a holder, operator dependent, not reproducible
167
why use bisected angle?
change position p.t cant tolerate holders access is difficult
168
describe bisected angle technique
•Film is placed as close to the tooth as possible •Operator observes the angulation of the film relative to the tooth •Operator bisects angle made between tooth and film and angles x-ray tube so that the beam will be at 90o to the bisector angle the tube and position the cone in the vertical and horizontal plane so its aligned with the film.
169
function of bisected angle holder
avoid irradiating finger aid visualising angulations reduce film bending stabilise film
170
paralleling technique
accurate reproducible good for caries detection/bone level easy technique uncomfortable perfect position difficult to achieve
171
bisected angle
inaccurate operator dependent irradiates finger more comfortable useful for special needs or gag reflex
172
why take occlusal radiographs?
show larger areas than periapicals show unerupted teeth, supernumerary teeth, cysts
173
technique for taking occlusal radiographs
•Modified bisected angle technique •Using set angulation •Film placed in mouth, head positioned occlusal plane horizontal •Insert film as far as patient can tolerate •White side of film towards area to be imaged •X-ray beam angled to appropriate angulation for area being imaged
174
occlusal radiograph angulations
•Anterior oblique occlusal maxilla – 65o •Lateral oblique occlusal maxilla - 60o -70o •Anterior oblique occlusal mandible – 45o •Lateral oblique occlusal mandible – 45o •True occlusal mandible - 90o
175
Indications for radiographic localisation
•Assessing buccal-palatal relationship of unerupted teeth to the dental arch •position of foreign bodies •expansion/destruction of bone •position of salivary calculi •separating the multiple roots of teeth for RCT •assessing the displacement of fractures
176
What are 2 systems for localisations
2 views at 90 degrees to each other parallax shift
177
Describe parallax views and parallax shift
•2 views/radiographs taken of same object with a change in angulation of beam •relative movement of object being localised to fixed point •horizontal or vertical plain •usually taken to determine buccal/palatal position of non-visible object •separate superimposed objects
178
Describe the parallax for U/E canines
palatally placed: will move in same direction as the tube head- with the tube bucally placed: moves in opposite direction to tube head.
179
How can parallax shift localisation be employed?
2 views with a small change in angulation or movement of the tube: e.g. •2 oblique occlusal views: anterior & more lateral •Paralleling periapical & oblique occlusal •Can be difficult to work out relative change in position.
180
What do radiographs show?
•Radiographs provide retrospective evidence of dental disease •Overall assessment of periodontal disease is based on both clinical & radiographic examination •Radiographs show amount of bone remaining in relation to length of tooth
181
What film is best to show periodontal disease and why?
bitewings, periapicals and DPT
182
Why do we get cervical burnout?
radiolucent area on interproximal surfaces of the root apical to ADJ created by decreased xray attenuation of the cementum
183
Describe the selection criteria for radiographs
systematically developed statements designed to assist the clinician and patient in making decisions about appropriate healthcare for certain specific circumstances.
184
recommended radiographs for pockets \<6m
horizontal bitewings
185
recommended radiographs for pockets \>6mm
vertical bitewings supplemented with parallel periapical views if perio-endo lesions suspected
186
recommended radiographs for irregular pockets
bitewing and periapicals
187
recommended radiographs for anterior teeth?
periapicals
188
How often should you take radiographs for periodontal reasons?
no clear evidence to support any recommendations regarding how often radiographs should be taken for periodontal reasons should be reproducible
189
What are some radiographic challenges?
mobile teeth missing teeth doseage
190
what are images relating to the mandible?
postero-anterior mandible lateral oblique DPT
191
what are images relating to the maxilla and cranium?
lateral cephalogram occipito-mental views (0,10 and 30 degrees)
192
What are the positioning landmarks for an extra oral radiograph?
•Radiographic base line - line from outer canthus of eye to EAM(external auditory meatus) - represents base of skull •Frankfort plane – IOB(inferior orbital border) to upper border EAM - represents anthropological base line •Maxillary occlusal plane - ala of nose to tragus of ear
193
Describe scatter radiation
when xrays pass through tissues some are scattered- Compton adds to background fog greyer film- lacking contrast
194
What is the purpose of an anti scatter grid?
•To stop photons scattered in patient reaching the film. •Avoids degrading image & reducing contrast. •Narrow strips of lead alternating with plastic. •Fixed/stationary or moving/oscillating can increase exposure and dose
195
Outline the technique for taking extra oral radiographs
•Position of patient relative to film. •Position of x-ray beam relative to patient. •Angle of x-ray beam relative to film.
196
why take lateral oblique jaw radiographs?
•Fracture of body, ramus and condyle. •Pathology e.g cysts. •Assessment of wisdom teeth. •Dental assessment in special needs patients. •Caries in children(those who can not tolerate bitewings)
197
Why would you take a PA of the mandible?
•Fractures - show medio-lateral displacement •Cysts and malignancy causing medio-lateral expansion or bone destruction. •Good visualisation of posterior body & ramus. •Limited visualisation of head/neck of condyle. •Midline can be obscured by spine. •Reduced magnification of facial structures. •Reduced dose to eyes.
198
describe a PA mandible
•Patient faces film •Nose and forehead touching film holder •Radiographic baseline – horizontal •Aim centre of beam to mid line of patient at the height of mid ramus.
199
How do you find the midline of a patient?
external occipital protuberance in the middle of the head middle fingers on the backs of ears and thumbs meet in the middle
200
Describe the technique for taking a lateral oblique radiograph
1. isocentric positioning using a skull unit p.t supine rotate machine into horizontal plane angle 25degrees towards head tilt top og p.t head towards film 2. dental tube with vertical angulation p.t holds cassette against and parallel to the area under examination tubehead beneath lower border of the body of the mandible not under examination tube aimed towards investigating teeth. 3. dental tube with horizontal angulation tubehead aims along occlusal plane just below the ear through radiographic keyhole
201
Outline the anatomical features seen in a lateral oblique of the mandible
coranoid process condylar head condylar neck cervical spine ramus angle of mandible hyoid body of mandible mental foramen
202
Why would you take a lateral ceph?
•Orthodontic assessment. •Pre Orthognathic surgery. •Can only be done using Cephalostat. •Patient positioned with ear rods to give standarised positioning. •Image must be reproducible. •Must have means of calculating amount of magnification. •Must be able to visualise soft and hard tissue. •Must have means of either calculating magnification or callibrating digital image
203
Technique for taking a lateral ceph
mid sagittal plane parallel to film/receptor Frankfurt plane horizontal centre of xray beam aimed at EAM teeth in occlusion
204
How do you reduce magnification with a lateral ceph?
long focus to p.t patient distance and short patient to film distance magnification rod 1.5-2m distance from xray tube
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What is the purpose of an aluminium filter?
over anterior part of face attenuates the beam in the anterior facial region visualisation of the bone and soft tissue on 1 film
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Outline whats seen on a PA ceph
frontsl sinuses nassion marker orbit sella turcica maxillary sinus anterior nasal spine soft palate molars in occlusion cervical spine hyoid bone
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Why would you take an occipito –mental radiograph?
•Facial bone fractures – zygoma, Le Fort and orbital blowout. •Pathology – limited use in sinus disease. Used only very occasionally.
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How would you position a patient for an occipito –mental radiograph?
Patient faces film holder •Nose and chin touching the holder •Radiographic baseline 450 to film •Aim centre of x-ray beam to midline of patient through base of nose. •Angle beam 10 or 30degrees to feet
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What is the effect of increasing angulation?
Projects dense bones of skull base down away from facial structures •Improves view of zygomatic arch •Gives different perspective – may be useful for evaluation of bony displacement
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Outline whats seen on a an occipito –mental radiograph
orbit nasal septum intra-orbital foramen zygomatic arch coronoid process
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What governs the use of ionising energy in dentistry?
IRR99 and IR(ME)R2000
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What is IRR99
equipment and protection of staff and general public
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What is IRR99
equipment and protection of staff and general public
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What is IR(ME)2000
protection of patients
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What are the proposed changes in legislation?
IRR17 IR(ME)R18 3 tier approach- notification, registration and regulations registered machines online process
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What is an RPA?
radiation protection advisor medical physicist or specialist company consult when planning new surgery/radiation overdose establish controlled area name and contact details in radiation protection file
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Describe the controlled area
only the patient in controlled area during exposure size depends on kV of machine 1.5m for under 70kV DDH 2m or behind appropriate shielding
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what is an RPS?
•Every practice must have one •Usually dentist or senior member of staff •Must be adequately trained •To ensure compliance with IRR 99 (2017) and Local Rules •Closely involved in radiography •Have authority to carry out their duties
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Describe the legislation behind local rules
All practices must have written local rules •Apply to all employees •Relate to radiation protection •Name of RPS •Name of person with legal responsibility for compliance •Identification & description of controlled area •Contingency arrangements if malfunction •Details & results of dose investigation levels •Name & contact details of RPA •Personal dosimetry arrangements •Arrangements for pregnant staff •Reminder of IRR99 (2017) obligations •“Displayed” where x-ray equipment
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What is being implemented in IR(ME)R18
dentists will have to formally appoint a medical physics expert- advanced role advising on IR(ME)R18 compliance, need to be in development and review of all dental procedures
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What are the 4 roles in radiography?
employer referrer practitioner operator
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describe entitlement
entitled by employer to undertake role must be within remit/scope of practice
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