how many meters should the controlled area be?
1.5-2m
what is the controlled area?
the required distance between the operator and the X-ray beam
Why do periapical radiographs?
- assess periodontal problems
- endodontics
- trauma/fractures
- tooth morphology (pre-extraction)
- evaluation of implants
- detect apical inflammation/infection (incl cysts)
- presence/position of un-erupted teeth
what two techniques can you use for a periapical radiograph?
- paralleling technique
2. bisected angle technique
what is the paralleling technique?
the tooth is parallel to the film and the X-ray beam at right angles to the film/tooth using a holder.
what are the 3 benefits of the paralleling technique ?
- reproducible image given
- accurate geometry
- minimises magnification
the negative point of using the paralleling technique is..
the holder may not be tolerated by the patient as relatively bulky.
when would you carry out the bisected angle technique?
if your patient isn’t co-operating and you want to reduce the number of repeat images = reducing the exposure.
benefit of the bisected angle technique?
more comfortable for the patient
3 disadvantages of bisected angle technique?
- operator dependant
- not reproducible
- easily distorted (foreshortening and elongating)
what are the 3 components of the holder?
- bite block
- indicator arm/rod
- aiming ring
for paralleling technique, the horizontal positioning is..
horizontal plane of the film must be parallel to the occulsal plane of the teeth being examined.
for paralleling technique, the vertical positioning is..
the vertical plane of the film must be parallel to the long axis of the tooth
if the horizontal plane is incorrect then..
crossover
if the vertical plane is incorrect then..
elongation or foreshortening of the teeth
if the X-ray beam is not at right angles to the teeth/film then you will get…
elongation or foreshortening or crossover of the teeth
name the two things affecting image size.
- the X-ray source (focal spot) to film distance
2. the tooth to film distance
if the tooth to film distance increases then…
the magnification will increase.
if the X-ray source (focal spot) to film distance increases then…
the magnification will decrease
the 2 things you need to reduce magnification are…
- a long X-ray source (focal spot) to film distance
2. a short tooth to film distance
Why would you use a bitewing radiograph? 4 points
- detect caries
- monitor caries progression
- assess periodontal status
- asses existing restorations
give 4 points about vertical bitewings
- long axis of the tooth and film vertical to one another
- pre-molars and molars
- usually need two on each side
- will show more of the roots (incl bone levels)
give 4 points about horizontal bitewings
- long axis of the film and tooth horizontal
- shows distal of the 4 to medial of the 8
- usually only need 1 each side
- will demonstrate crowns and 1/3 of root
which technique do you need for bitewings?
the paralleling technique (must always se a holder)
