Radiographic Techniques 1 - PA Flashcards
What is the basic principle for all radiographs?
- x-ray source
- object
- receptor
Relationship of each other is key to quality of image
What are the types of intra-oral radiographs?
Intra-oral - receptor inside mouth
- peri-apical
- bitewing - horizontal or vertical
- occlusal - mandible/maxilla
What are the types of extra-oral radiographs?
Extra-oral - receptor alongside patient
- dental panormaic tomogram (DPT)
- lateral cephalogram
- postero-anterior mandible
- lateral oblique mandible
- occipito-mental views of facial views
What should a peri-apical radiograph show?
Horizontal BW?
Vertical BW?
Maxillary occlusal?
Lower submandibular occlusal?
Periapical - crown to apices of root and clearly between teeth
Horizontal BW - distal edge of 4 to mesial of 8, need to see bone levels but do not need to visualise roots
Vertical BW - more of bone but still not entire root
Maxillary occlusal - anterior part of maxilla and anterior teeth
Lower submandibular occlusal - plan view of the tooth bearing portion of mandible and FOM
Briefly describe how DPTs are taken:
What is a lateral cephalogram commonly used for?
What can be displayed on a postero-anterior (PA) mandible radiograph?
DPT - x-ray tube rotates around pts head with a constant long exposure of 14 secs forming a panoramic image of pts teeth and supporting structures
Lateral Cephalogram - used in ortho to assess relationship of teeth to jaws and mandible to rest of facial skeleton, can also see soft tissue pattern of nose and lips which is useful for surgical planning
PA mandible - showing a fractured mandible, should be requested in conjunction with a DPT
When is a lateral oblique mandible most commoonly used?
Occipito-mental?
What gives an image the most detail?
Lateral oblique mandible - common alternative for children who cannot tolerate BWs, also done for adults with mandibular fractures if DPT not available
Occipito-mental - pts reporting to A and E following facial trauma, shows fractures of orbits, maxilla and zygomatic arches, 2 views taken (10 and 30 degrees)
The closer the object is to the receptor, the more detail the image will capture.
What are the main clinical indications of periapicals?
Periapicals:
- detection of apical inflammation/infection
- detailed evaluation of apical cysts and other lesions within bone
- assessment of periodontal status
- after trauma to teeth and associated bone
- assess rot morphology pre-extraction
- presnce and position of UE teeth
- during endodontics
- pre-post op appraisal of apical surgery
- evaluation of implants post-op
What is the parallelling technique?
Bisected angle technique?
Parallelling: technique of choice
- uses holders to facilitate posiitoning
- receptor parallel to tooth
- accurate reproducible image
Bisected angle:
- can be done without a holder
- operator dependant, finger can be exposed to radiation, not reproducible
What is the blue holder for?
Red?
Green?
Yellow?
What is the holder made up from?
Blue = anterior teeth
Red = BW
Green = endodontics
Yellow = posterior teeth
Bite block - retains receptor
Indicator arm/rod - fits into bite block
Aiming ring - slides onto the arm to establish alignment of the collimator with receptor
What are some ground rules when positioning the holder/collimator for an x-ray?
- Receptor - tooth relationship: vertical plane of film should be positioned so it is parallel to the long axis of the tooth, horizontal plane should be positioned parallel to dental arch
- X-ray tube position - x-ray beam should be at 90 degrees to the tooth and receptor
- Magnification - how much larger the size of the object under investigation will appear on the final image compared to its actual size
What are the two factors which affect image size?
How much distance should be between the tooth and receptor/ x-ray source to get a good quality image?
- X-ray source (focal spot) to receptor distance
- Object (tooth) to receptor distance
Short distance between tootha nd receptor, long distance between x-ray source and object
What are some common barriers to good positioning?
- mouth size
- gag reflex
- film size
- digital sensor size and shape
Which film size should be used for taking periapicals on an adult?
Bitewings on an adult?
Periapicals:
- anterior - 0 or 1, (2 if bisecting angle)
- posterior - 2
BWs:
- adult - size 2
Which film size should be used for children when taking periapicals?
Bitewings?
Periapicals:
- anterior - 0
- posterior - deciduous 0, permanent 2
Bitewings:
- under 10 - 0 or 1
- over 10 - 2
