口腔学英文课件：SLOB-tube shift.ppt

Tube-Shift Localization (Clark) SLOB Rule Same Lingual Opposite Buccal The SLOB rule is used to identify the buccal or lingual location of objects (impacted teeth, root canals, etc.) in relation to a reference object (usually a tooth). If the image of an object moves mesially when the tubehead is moved mesially (same direction), the object is located on the lingual. If the image of the object moves distally when the tubehead moves mesially (opposite direction), the object is located on the buccal.,For the SLOB rule to work, there must be a change in the horizontal or vertical angulation of the x-ray beam as the tubehead 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.,The closer the object to be localized is to the reference object, the less the amount of movement of the image of the object in relation to the reference object.,In the diagram at right, the tubehead 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 tubehead without changing the beam direction would often result in a cone cut , depending on how far the tubehead is moved (see below right).,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.,Moving the tubehead 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 at right, the tubehead 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 tubehead movement. (Objects closer to the film move less distance than objects farther from the film; in the example shown below, both the tooth and object move forward on the film, but the lingual object moves less and “appears” to move distally in relation to the tooth).,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 tubehead 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 tubehead is moved distally for the molar projection.,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,In the diagram at left, the tubehead is moved distally and the beam is directed mesially. On the radiograph, the buccal object of interest (yellow) moves mesially (opposite to tubehead movement) in relation to the second molar and the lingual object of interest (red) moves distally (same direction as tubehead) in relation to the second molar.,mesial,distal,mesial,distal,Horizontal movement,In the diagram at right, the tubehead is moved mesially and the beam is directed distally. On the radiograph, the buccal object of interest (yellow) moves distally (opposite to tubehead movement) in relation to the second molar and the lingual object of interest (red) moves mesially (same direction as tubehead) in relation to the second molar.,mesial,distal,mesial,distal,Horizontal movement,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 tubehead moves down and the beam is redirected upward (opposite direction; decreased vertical angulation).,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,In the diagram at left, the tubehead is moved upward and the beam is directed dow。