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31 Cards in this Set
- Front
- Back
5 Reasons to take a bitewing?
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1. Detect caries
2. Monitor caries progression 3. Assess restorations 4. Monitor bone levels 5. Other pathology ie impacted teeth |
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12 Properties of X-rays?
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1. Invisible, longitudinal waves of the EMS that travel as photons
2. Ionising 3. No charge 4. Travel at speed of light 5. Travel in straight lines 6. Damage/kill/mutate cells 7. Effect silver halides 8. Produces photofluorescence in some materials 9. Produced by electrons impacting on matter 10. Shorter wavelength than visible light 11. Emitted at a continuous spectrum - Shortest wavelength determined by tube voltage 12. Differentially absorbed |
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What does BERT stand for? Give an example of it's use.
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Background Equivilant Radiation Time
1 transatlantic flight = 5 days BERT 1 Chest X-ray = 4 days BERT PA with E speed film: Round Collimator: 8 hours BERT Square Collimator: 4 hours BERT |
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What are the occupational limits on radiation dose?
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20mSv/year over 5 years with no more that 50mSv in any one year
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What is the ALARA principle?
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As Low As Reasonably Achievable
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How can ALARA be achieved?
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Lead aprons
Minimsing errors and retakes Fast speed film (F) Collimator (square best) Aluminium filter Safe distance/Barrier to next worker Low use of rooms surrounding X-ray room Timer |
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What does the collimator do?
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Remove peripheral x-rays therefore minimsing dose to patient. Square is best
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What does the Aluminium filter do?
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Remove low wavelength x-rays that would only be absorbed by the patient (increase mean wavelength). This reduces dose.
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What are the pros of the Parallel technique?
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Less likely to cone cut
Maxilla and Zygomatic arch doesn't get in the way No size distortion |
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What are the cons of the Parallel technique?
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Can't do it everywhere - upper molars, palate in way
More uncomfortable for patient Apices near edge of film Film further from tooth therefore poorer image definition |
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What are the pros of the Bitewing technique?
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Easier
More comfortable for the patient Adequete for diagnosis, if not ideal |
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What are the cons of the Bitewing technique?
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Not reproducible
Bone levels poorly shown Image distortion of the root/crown. Makes caries diagnosis difficult |
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What is SLOB?
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Same Lingual Opposite Buccal
These are the directions that the said teeth will move in relation to the X-ray TUBE when it is moved. |
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What is the Buccal Object rule?
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The buccally located object will move in the same direction as the X-ray BEAM
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What is the 90/Different Planes of Ref method?
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Taking 2/3 radiographs from different angles to localise an object
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What film sizes are used for bitewings?
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Size 0 = children
Size 1 = mixed dentition Size 2 = adults |
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What film sizes are used for periapicals?
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Size 0/1 = Vertically placed for anteriors
Size 2 = Horizontally placed for posteriors |
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What can/should be seen on a bitewing?
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Occlusal plane should be in the middle
Equal amounts of Max/Man crown and roots Target teeth shown completely 1/3 of Alveolar bone crest Surrounding tissue |
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How should an image appear?
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Good sharpness, clarity and contrast
No staples etc covering diagnostic areas No fingerprints Minimum distortion Faults/artifacts no in diagnostic ares No conecut No overlap in critical areas |
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Why should you take periapicals? (10)
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1. Assess periodontal status
2. See root morphology pre-extraction 3. Trauma cases 4. Pre/post op assesment for endodontic treatment 5. Bone assesment for implants 6. Position/prognosis of implant 7. Assessment of apical lesion 8. Assessment of impacted teeth 9. Assessment of lesions on Aveolar bone 10. Assess apical changes due to infection/inflammation |
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What can/should be seen in a periapical?
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Crown and root of target teeth
3-4mm Apically of tooth Surrounding tissue |
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What interaction produce X-rays?
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Braumstralung: X-rays produced via electron/nucleus interaction
Electron to Electron |
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What are the steps in image processing?
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Developing - Converts exposed silver halide crystals (which contain silver ions) to metallic silver, softens gel emulsion. 4.5 minutes at 20 degrees
Rinsing - 15/20 seconds Fixing - Halt development, remove undeveloped silver halide, harden gel emulsion Washing - remove thiosulphates that would otherwise turn the film brown, 10 minutes Drying |
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Constituants of developer? (SHEPS)
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DEVELOPER
Reducing agents that donate electrons to silver ions Elon - Brings out shades of grey quickly. Temp independant Hydroquinone - Gives contrast slowly. Temperature sensitive ACTIVATOR Sodium Carbonate - softens gelatin and maintains alkaline conditions RESTRAINER Potassium Bromide - Delays developer effect, reduces fog PRESERVATIVE Sodium sulphite - Prevents oxidation of Developer Developer must be completely changed every 3-4 weeks |
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Constituants of fixer? (SAPS)
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FIXER
Sodium Thiosulphate - interacts with silver halide making it water soluble and therefore removable ACIDIFIER Acetic Acid - Neutralisers residual alkali therefore stoping development. Provides necessary acidic environmnet for hardener HARDENER Al Potassium Sulphate - hardens gel emulsion PRESERVATIVE Sodium Sulphite - prevents oxidation of residual Developer |
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What is the dental film made of?
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Base - hard gelatin, tinted slightly blue
Emulsion - gelatin matrix embedded with silver bromide crystals and some silver iodide crystals and sulphur. |
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Voltage from Cathode to Anode effects what? What is the usual voltage?
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Wavelength/energy of rays. Higher voltage gives higher energy/ shorter wavelength waves
50 to 90 kV |
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Current in the tungsten coil effects what?
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High current give high number of electrons in wire, therefore x-ray number.
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Give some errors that cause faulty radiographs?
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Cone cutting - incorrect beam/film allignment
Insuffient exposure time Light leakage (film fog) Too light - underdeveloped Too dark - overdeveloped Patient movement Processing errors: temperature, time, depleted/diluted developer or fixer |
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What is mSv?
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milli Sievert
Sievert = unit of dose equivalent to 1 J/Kg |
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What are the milliSeivet values for the usual radiographs taken?
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PA & Bitewings: 1-2 mSv (square vs round collimator)
OPG: 3.4 mSv Chest film: 30 mSv |