Bitewing and Paralleling Periapical Flashcards
What are benefits of intra-oral?
- High resolution
- Minimal superimposition
- Fast exposure
- Low radiation
What are the downsides of intra-oral?
- Limited to small area
- Invasive for patient
- Difficult technique
What sizes are used for each radiograph?
0 = anterior periapicals, child (in some circumstances)
2 = bitewings, posterior periapicals
4 = occlusals
What is projection geometry?
Relates to the positioning ( angulation and relative distances) of all of the components involved in taking a radiograph
What is the ideal geometry?
non divergent x-ray bean
tooth immediately next to receptor
x ray bean exactly perpendicular to both tooth and receptor
What is the realistic geometry?
X-ray is divergent (tooth looks bigger)
tooth quite close to receptor (tooth appears larger)
tooth is not perpendicular to x-ray beam (tooth appears shorter)
receptor is not perpendicular to x-ray beam (tooth appears stretched)
How is magnification reduced?
bring subject closer to receptor
x-ray beam is always divergent
What is constant with the x-ray beam?
it is always divergent
How is the best possible projection geometry achieved?
- Maintain a sufficient focus-to-skin distance
• A larger distance will result in a less divergent beam - Position receptor as close to tooth as reasonably possible
• Intra-oral anatomy might dictate how close you can get without bending receptor (e.g. hard palate, curvature of dental arch, etc.) - Ensure receptor is as stable as possible in the mouth
• Complicated by missing teeth, mobile teeth, pain, gagging, etc. - Use image receptor holders with a beam aiming device
• Aid correct angulation of receptor & X-ray beam - Keep patient still!
What will a longer focus to skin distance (FSD) do?
A longer fsd will reduce magnification of the image
• UK guidance recommends at least 200mm for intra-oral X-ray units
How is the FSD maintained?
Distance is maintained by using a spacer cone
• Fixed or detachable
Where is the FSD measured from?
Measured from the X-ray source
• Marked on the X-ray unit
What is strongly recommended to aid positioning?
Receptor holders
What do bitewing radiographs aim to show?
Aim to show:
• Premolars & molars
• Maxillary & mandibular teeth at the same time
• Inter-dental bone
• Minimal (if any) overlap of adjacent teeth
Used only for posterior teeth
What are the indications for bitewings?
Indications
• Detection/monitoring of caries
• Assessment of dental restorations
• Detection/monitoring of periodontal bone loss
• (unless severe)
