radiographic localisation Flashcards
need for radiographic localisation
to determine location of a structure or pathological lesion in relation to other structures
- only needed where clinical examination insufficient to provide answer
- clinical examination must always occur prior to radiographic examination
5 clinical situations for radiographic localisation
position of unerupted teeth
- normal but impacted (cannot meet normal occlusal plane position)/ectopic
- supernumerary (common in upper anterior)
- proximity to important structures (inferior alveolar canal, maxillary sinus, nasal cavity)
location of roots/root canals
- endodontics
- surgery
relationship of pathological lesions
trauma
- dental
- bone fractures
soft tissue swellings - ? tissue/source (could be tooth)
3 stages of using radiograph as information
- Observation - look and see
- Interpretation - listen and think
- Management - patient’s needs, what is there primary concern
use sequentially
how to spot and correct faults or diagnostic puzzles
(3 steps)
- perception
- recognition
- resolution
influenced by knowledge base
what can you observe from this radiograph?
technical acceptabilitly?
abnormalities?
need for more X-rays?
- technical acceptability
- Why was it being taken?
- Abnormalities
- Mesial apex radiolucency on 6 – non vital?
- Distal root on 6 – shorter – why? Chronic inflammatory changes causing it to resorb?
- 8 – mesial root is curved – dilaceration – sharp bend
- 8 distoangluar rotated compared to 7
- Supernumerary distal to 3 molar – position transverse to arch
- need for further radiography
- only need to know if the supernumerary needs extract – clinical Q
observe this radiograoh
No apices – poor quality radiograpgh
8 is transverse?
how to decide if tooth transverse
2D – lacking knowledge
- Need to view from right angles
- use both together
The “right angle” view
- from lateral and from underneath
crown is lingual of 8
no full length of roots – need more radiographs if extractions
options for radiographic viewing at right angles
(3)
- panoramic and lower true occlusal (may need to use PA film as unacceptable for pt for occlusal film distal)
- paralleling periapical and lower true occlusal
- CBCT (cone beam CT) – each of the MPRs is at right angles to the others
methods of radiographic localisation
normally two views required
- views at right angles in their projection geometry
- views with any different projection, provided the difference is known
with the aid of opaque objects (e.g. gutta percha point – sinus involvement, GP in and able to see what apex is causing the problem )
anatomical knowledge crucial
radiographic localisation if views not at right angles
- known projection geometry
- must both include item to be localised and stable reference point (ideally intra oral)
- multiple combinations possible
- utilise horizontal or vertical “tube shift” to aid interpretation
parallax
apparent change in the position of an object caused by a real change in the position of the observer
the objects appear to change their relationship – to each other and to you
- gradation
horizontal and vertical tube shift and the observer
Consider the position of the X-ray tube when each view is taken
- Imagine that you are looking at the patient from that position
Your viewing point is interchangeable with the X-ray tube head position
- BUT for a panoramic radiograph we consider looking from in front of the patient, as if back along the X-ray beam
viewing and beam location
Radiographs normally viewed from the buccal aspect of the patient, therefore:
- beam “passing” from buccal to lingual
- buccal is closest to observer
- lingual/palatal is furthest from observer
parallax mneonic for comparing positon of one structure to another
S same
L lingual
O opposite
B buccal
my PAL comes with me - palatal
sequence of steps in radiographic localisation (4)
- identify direction of tube movement
- ? what do we need to know the location of
- choose a reference
- observe movement of ? in correct direction
is this arrangement of radiographs correct?
1 has 4, 5, 6 and part of 7, minimal overlap, central ray between 5 and 6
2 has 6, 7 and part of 8, minimal overlap, central ray between 6 and 7
- Tube has moved back
- Arranged wrong on viewing box
how to arrange films on viewing box
in direction of movement once determiind
how to determine where object want to localise is
e.g. tooth below - supernumerary
Lingual to roots of 6 and 5
Take recognisable part of crown anatomy - mesial curve
- First lines with pulp canal of 5
- Second lines with periodontal ligament space of 5
x ray tube has been moved forward – same direction crown moved – so LINGUAL
endodontic application of parallax
issue here
how to resolve
- the mesio-buccal root is superimposed on the palatal
which way should we move the tube?
- decide where we want the root to move to in relation to palatal root – mesial or distal
- mesially, therefore move tube backwards
tube moved distally - arrange films to reflect relationship correctly
- more anterior positioning includes canine
- more posterior film no canine showing
describe annomaly here
16 yo impacted 23
- horizontal
- superimposed roots 21 and 22
- also resorbed as these – as cannot see image of roots of the incisors – need to check on CBCT
- see clear resorption
- also resorbed as these – as cannot see image of roots of the incisors – need to check on CBCT
why may the 11 be malaigned?
Male 12
supernumerary - mesiodens - orientation – horizontal, crown tip lower than apices of incisors
all permanent teeth developing
mesiodens: (tube from level to occlusal plane to up to bridge of nose)
- crown tip palatal – higher than apices of centrals
- moved up with tube = PALATAL
- apex buccal – down near crown root junction
- tube up, apex down = BUCCAL
need to uncover crown to extract – wider diameter
canines buccal to arch (23 less than 13) (moved down)
