2. • To obtain three-dimensional information of location of
an object such as:
• Foreign bodies
• Impacted, unerupted teeth
• Supernumerary teeth
• Broken needles
• Retained roots
• Fractures of maxillofacial structures
• Soft tissue calcifications
• Intra-osseous tumors
• Calculi in gland/duct of gland
• Filling materials in alveolar process
Object Localization
7. A PA. film identify the location of an object vertically and in a
horizontal (mesiodistal) direction, since it is a 2D. Therefore we
need another method for locating objects in a buccolingual
direction. The two primary methods of determining the
buccolingual location of objects are:
Right-Angle Technique (Miller’s Technique) (Occlusal
projection)
Primarily identifies buccolingual location, but may
also confirm mesiodistal location seen on periapical
Tube-shift Technique (SLOB rule, Clark’s rule)
Utilizes two films with different horizontal or vertical
angulations
Object Localization
10. LOCALIZES in 3 Dimensions
DISADVANTAGES
Can be used in mandible but not that useful
like in maxilla due to superimpositions
11. (
Tube shift technique (Clark’s rule
PRINCIPLE
Relative positions of radiographic images of
two separate objects changes ,when projection angle
at which images were made, is changed.
12. The image of Tooth that is farther away from X-ray
tube(lingual) moves in same direction as tube and
Image of Tooth closer to X-ray tube (Buccal) moves
in opposite direction.
SLOB
Same Lingual Opposite Buccal
17. For the SLOB rule to work, there must be a
change in the horizontal or vertical angulation of
the x-ray beam as the tube head is moved. This
change in angulation will alter the relationship
between the object of interest and the reference
object, allowing you to determine the buccal or
lingual location.
18. In the diagram at right, the tube head is
moved, but there is no change in
direction of the x-ray beam, which
results in no change in location of the
object of interest in relation to
reference object (see below). Moving
the tube head without changing the
beam direction would often result in a
cone cut , depending on how far the
tube head is moved (see below right).
19. When using the SLOB rule, the direction of the beam must be
opposite to the way the tubehead is moved.
Horizontal Tube Shift: When the tubehead is moved mesially,
the beam must be directed more distally (from the mesial). If
the tubehead is moved distally, the direction of the beam must
be more towards the mesial (from the distal).
Vertical Tube Shift: The SLOB rule also works for movement
of the tubehead in a vertical direction. Downward movement
of the tubehead requires that the beam be directed upward
and when the tubehead is moved upward, the beam must be
directed downward.
20. Moving the tube head mesially or distally and changing the
direction of the x-ray beam (as described in the previous slide)
will result in the movement of the object of interest on the film
in relation to the reference object. In the diagram below, the
tube head is moved distally with the x-ray beam directed more
mesially (from the distal). The object of interest, located
lingual to the first molar, moves distally, in the same direction
as the tube head movement.
21. incisors
canine
premolar
molar
Horizontal movement of the tubehead and x-ray beam
In moving from the incisor film to the canine film, the canine film
to the premolar film and the premolar film to the molar film, the
tube head moves distally and the beam is directed more mesially.
There is not much change in angulation from the premolar to the
molar film; the normal situation would be that the beam is directed
slightly more from the distal (or to the mesial) as the tube head is
moved distally for the molar projection.
22. In the diagram at left, the buccal
(yellow) and lingual (red)
objects of interest are
superimposed on each other
because the beam is directed
perpendicular to both of them
and they are in the same relative
position mesiodistally and
vertically. Both images are
located above the second molar.
mesial
distal
mesial
distal
Horizontal movement
23. In the diagram at left, the tube
head is moved distally and the
beam is directed mesially. On the
radiograph, the buccal object of
interest (yellow) moves mesially
(opposite to tube head movement)
in relation to the second molar
and the lingual object of interest
(red) moves distally (same
direction as tube head) in relation
to the second molar.
mesial
distal
mesial
distal
Horizontal movement
24. In the diagram at right, the tube
head is moved mesially and the
beam is directed distally. On the
radiograph, the buccal object of
interest (yellow) moves distally
(opposite to tube head movement)
in relation to the second molar and
the lingual object of interest (red)
moves mesially (same direction as
tube head) in relation to the second
molar.
mesial
distal
mesial
distal
Horizontal movement
25. Maxillary PA
BW
Mandibular PA
Vertical movement of the tubehead and x-ray beam
In moving from the maxillary periapical to the bitewing and from
the bitewing to the mandibular periapical, the tube head moves
down and the beam is redirected upward (opposite direction;
decreased vertical angulation).
26. In the diagram at left, the buccal
(yellow) and lingual (red) objects of
interest are superimposed on each
other because the beam is directed
perpendicular to both of them and
they are in the same relative position
mesiodistally and vertically. Both
images are superimposed over the
mandibular second premolar.
Vertical movement
27. In the diagram at left, the tube head
is moved upward and the beam is
directed downward. On the
radiograph, the buccal object of
interest (yellow) moves down
(opposite to tube head movement)
in relation to the second premolar
and the lingual object of interest
(red) moves up (same direction as
tube head) in relation to the second
premolar.
Vertical movement
28. In the diagram at left, the tube head
is moved downward and the beam is
directed upward. On the radiograph,
the buccal object of interest
(yellow) moves up (opposite to tube
head movement) in relation to the
second premolar and the lingual
object of interest (red) moves down
(same direction as tube head) in
relation to the second premolar.
Vertical movement
30. Is the composite restoration on tooth # 8 (arrows) located on the
buccal or lingual?
canine film incisor film
1
The restoration is located on the buccal. The tube head moves
mesially from the canine film to the incisor film (x-ray beam
projected more distally) and the composite moves distally,
which is the opposite direction.
31. canine film
premolar film
The arrow in the canine film is pointing to the gutta percha in
which canal of the maxillary first premolar?
2
The arrow identifies the lingual canal. The tube head moves
mesially from the premolar film to the canine film (beam directed
more distally) and the gutta percha indicated by the arrow also
moves mesially. (See following slide).
32. PID
lingual
buccal
When the tube head is moved mesially, with the beam directed
distally, the two canals, which are initially superimposed (premolar
periapical above) will separate. The lingual canal (red arrow) will
follow the tube head movement and the buccal canal (blue arrow)
will move in the opposite direction, as seen on the canine film.
33. The red arrow is pointing to the gutta percha in which
canal of this maxillary left first premolar?
This is the buccal canal. The tubehead goes distally
from the canine film to the premolar film and the gutta
percha moves mesially to be positioned over the lingual
canal which has the threaded post.
The pink arrow points to a threaded post. In which canal
of this maxillary left second premolar is the post located?
The post is located in the lingual canal. As the tube
head moves distally from the canine film to the
premolar film, the post also moves distally to cover
the canal that has all gutta percha.
3
34. Is the maxillary second
premolar (arrows)
displaced to the buccal or
the lingual?
premolar film molar film
premolar bitewing
4
The tube head moves distally from the
premolar film to the molar film. The
second premolar also moves distally,
overlapping the first molar more in the
molar film. In moving from the premolar
periapical to the bitewing, the tube head
moves down and the premolar also
moves down. The displacement is to the
lingual.
35. incisor film canine film
Is the displaced incisor (arrows) located on the buccal or the
lingual?
5
The lateral incisor is displaced to the lingual. The tube head
moves distally from the incisor film to the canine film. The lateral
incisor also moves distally, covering half the canine on the canine
film.
36. canine film
premolar film
Is the radiopaque object identified by the arrows located on the
buccal or the lingual?
6
Lingual. The tube head moves mesially from the premolar film to the
canine film. The object also moves mesially, starting out distal to the
first molar on the premolar film and ending up mesial to the first molar
on the canine film. This object represents the tip of the palatal root of
the second molar and is located distal to the first molar and in a lingual
relationship
37. film placement for canine film
film placement for premolar film
root tip
