ion techniques
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PRESENTED BY
DR.RUNUK SINGHIPG STUDENT (ORAL MEDICINEAND RADIOLOGY)
LOCALISATIONLOCALISATION
TECHNIQUETECHNIQUE
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Why Do We NeedRadiographs ?
Dental radiograph is a two dimensionalpicture of a three dimensional object.
IOPA - depicts the object in the superior-inferior and anterior-posterior relationship.However does not depict buccolingualrelationship or depth of the object.
Occlusal - depicts the object in anterior-posterior and buccolingual relationship.However does not depict superior-inferiorrelationship.
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IndicationsForeign bodies
Impacted teethUnerupted teeth
Retained roots
Salivary stonesOrientation of fracture lines
Broken needles and instruments
Root positions
Filling materialsCysts, or neoplasms
Position of vital structures eg. Floor of
sinus, Mandibular canal
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Especially useful in...
Endodontics
Orthodontics
Implantology
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Methods used to localiseobjects
Definition Evaluation
Buccal Object Rule (Tube Shift Technique Or
Clarks Rule)Right Angle Technique
Stereoradiography
CT and MRI
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Definition EvaluationStructures that lie closer to the X-ray film
have better radiographic definition thanthose that are farther than the film.
Because the intraoral film is positioned lingually,the superimposed structure that is more sharplydefined is positioned more lingually in relation toother structures.
Advantage- requires no further X-ray exposuresof the patient.
Disadvantage- least reliable and notrecommended.
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Tube Shift Technique
...if we wish to ascertain [where] a buried canine
is lying, three radiographs are taken: the firstdirectly over the suspected tooth, and which wewillcall the centralposition, and anothermesialto this position, while the third istaken distalof the first or central position.
Each of the three radiographs must be markedimmediately [after] they are taken, or confusionwill arise. With the three radiographs placed intheir relative position[s], we carefully note theposition of each tooth shown in the centralradiograph, and by comparing it with the othertwo the position of the buried tooth, whether it ison the palate or whether it is situated labially,can be ascertained readily with a little practice.
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Tube Shift Technique
It was described by Clark in 1910.The rationale for this procedure derives from the
manner in which the relative positions of
radiographic images of 2 separate objectschange when the position angle at which theimages were made is changed
It uses the principle of parallax which isdefined as the apparent displacement of
an object because of different positions ofthe observer
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Given two objects in a perfectly straightline with the observer the more distantobject will be hidden from sight due toother.
If the observer moves to the right, the
more distant object will apparently move tothe right
Similarly, if the distant object seems tohave moved to the left, it means the
observer moved to the left.So as the more distant object seems to
move towards the direction taken bythe observer, the nearer the object it
seems to move in opposite direction
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Method
Two radiographs of the object are taken.
First using the proper technique & angulationsand the second radiograph is taken keeping all
other parameters constant and equivalent tothose of the first radiograph, only changing thedirection of the central ray either with adifferent horizontal or vertical angulation.
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InterpretationWhen the dental structure or object seen in
the second radiograph appears to havemoved in the same direction as the shift ofthe position indicating device (PID), the
structure or the object in question is said tobe positioned lingually.
But if the object appears to have moved ina direction opposite to the shift of the PID,
then the object in question is said to bepositioned buccally
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SLOB Rule
Same sideLingual
Opposite sideBuccal
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HorizontalTube Shift: When the tubehead ismoved mesially, the beam must be directedmore distally (from the mesial). If the tubeheadis moved distally, the direction of the beammust be more towards the mesial (from thedistal).
Vertical Tube Shift: The SLOB rule also worksfor movement of the tubehead in a verticaldirection. Downward movement of the tubehead
requires that the beam be directed upward andwhen the tubehead is moved upward, the beammust be directed downward.
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In the diagram at left, thebuccal (yellow) and lingual(red) objects of interest aresuperimposed on each
other because the beam isdirected perpendicular toboth of them and they arein the same relativeposition mesiodistally andvertically. Both images arelocated above the secondmolar.
mesial
distal
mesialdistal
Horizontal
movement
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In the diagram at left, thetubehead is moveddistally and the beam isdirected mesially. On the
radiograph, the buccal objectof interest (yellow) movesmesially (opposite totubehead movement) in
relation to the second molarand the lingual object ofinterest (red) moves distally(same direction as tubehead)in relation to the secondmolar.
mesialdistal
mesial
distal
Horizontal movement
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In the diagram at right, thetubehead is movedmesially and the beam is
directed distally. On theradiograph, the buccal objectof interest (yellow) movesdistally (opposite totubehead movement) in
relation to the second molarand the lingual object ofinterest (red) moves mesially(same direction as tubehead)
in relation to the second
mesial
distal
mesialdistal
Horizontal
movement
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In the diagram at left, thebuccal (yellow) and lingual(red) objects of interest aresuperimposed on eachother because the beam isdirected perpendicular toboth of them and they are
in the same relativeposition mesiodistally andvertically. Both images aresuperimposed over the
mandibular second premolar.
Vertical movement
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In the diagram at left, thetubehead is movedupward and the beam isdirected downward. On the
radiograph, the buccal objectof interest (yellow) movesdown (opposite to tubeheadmovement) in relation to the
second premolar and thelingual object of interest(red) moves up (samedirection as tubehead) inrelation to the secondpremolar.
Vertical movemen
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In the diagram at left, thetubehead is moveddownward and the beam isdirected upward. On the
radiograph, the buccal objectof interest (yellow) moves up(opposite to tubeheadmovement) in relation to the
second premolar and thelingual object of interest (red)moves down (same directionas tubehead) in relation to thesecond premolar.
Vertical movement
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BUILD Rule
If in vertical tube shift method, the tubehead is as a rule moved down with thecentral ray pointing upwards, we can putthe BUILD Rule in use.
B uccal
U p
IL ingual
D own
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RIGHT ANGLE TECHNIQUE
This technique was suggested by DrFred Miller and later popularized byWinter.
Here two projections are taken at rightangles to each other which helps tolocalize an object in the maxilla ormandible.
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MethodA periapical radiograph is taken to show
the position of the object supero-inferiorlyand antero-posteriorly.
Next, an occlusal radiograph is taken which
will show the objects buccolingual andanteroposterior relationship.
Two radiographs when studiedtogether help to localise the object inall three dimensions.
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Various Combinations
Lateral and postero-anterior (PA)cephalometric radiographs.
Lateral, PA, and submentovertex(SMV) skullor facial view.
Panoramic, or paralleling periapical, andtrue mandibular occlusal views.
Panoramic, or paralleling periapical, andvertex occlusal.
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Stereoradiography
J.Mackenzie Davidson introduced it in 1898only 3 years after Roentgens discovery ofx-rays.
Over the next 30 to 40 years the techniquegrew in popularity among radiologist because ofits educational value ;understanding normal
anatomy is simplified with stereoscopic images
St di h f ll f f f
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Stereoradiography fell from favour forseveral reasons among which were theintroduction of more sophisticated and
less time consuming imaging technique& a greater awareness of the adverse effectof x-ray as the stereoscopy imagingdelivers twice the amount of radiation
to the patient
Stereoradiography requires the exposure of
two films, one for each eye, and thusdelivers twice the amount of radiation to thepatient. Between exposures the patient ismaintained in position, the film is changed,
and the tube shifted from the right eye to
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TechniqueIn this technique the tube is first centered over the
part to be taken and then shifted 11/4 inches tothe right; it is then tilted in such a manner thatthe direct rays will pass through the samepoint of entry they would pass through if thetube was centered then the exposure is made.
The tube is then moved back to the centre thenshifted 11/4 inches to the left ,where a similarprocedure is followed to that taken on the rightside.
Thus a total of 21/2 inches movement of thetube through the center is brought about which iscorresponding to the distance between thepupil of the normal eyes.
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Stereoradiographcurrently enjoys a renewed
interest for evaluation of
bony pockets in patients with periodontaldisease
morphology of the TMJ area
determination ofroot configuration ofteeth that require endodontic therapy
assessment of the relationship of themandibular canal to the roots of
unerupted mandibular third molarsand assessment ofbone shape when
placement of dental implants is considered.
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CT AND MRI
Tomography is a generic term formedfrom the Greek words tomos i.e. slice or
section and graphia i.e. picture.
MRI has proved superior to CT fordepicting soft tissues
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The axial ,coronal and sagittal sectiongives a 3-dimentional picture of anobject/tooth/structure and thus helps inlocalization
The axial sections give the antero-posterior location.The coronal section gives the superio-
inferior view
The sagittal section gives the locationfrom the midline
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Assessment Of ThePosition Of The Canine
Using the Clark's rule if two views of anunerupted canine are taken with the x-ray tubein two different positions the resultantradiographs will show a difference in the
position of the unerupted canine relative to theincisors as follows:
If the canine is palatally positioned it will appearto have moved in the same direction as the x-ray tubehead, where as if it is labiallypositioned, it will appear to have moved in theopposite direction.
If the unerupted canine is in the same plane asthe incisors i.e in the line of the arch,it will
appear not to have moved at all
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Assessment of mandibularthird molar
The main features to examine include
Angulation
The crownThe root
The relationship of the apices with theinferior dental canal
The depth of the tooth in the alveolar boneThe buccal or lingual obliquity
Radiographic views
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Radiographic viewsused :
Periapicals
OPGOblique laterals
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Assessment Of TheRoot Canals
Assessment of the root canals can bedone using the Clarks technique
At least two radiographs are taken usingdifferent horizontal x-ray tubeheadposition
Using SLOB rule the position of differentcanals can be located
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The SLOB procedure applies during accessIf a single canal is discovered initially on
access preparation, an instrument is placedin the canal
Then a radiograph is made either mesial ordistal
If the instrument is skewed considerably offcenter another canal must be presentThe location of the missed canal is
determined by applying SLOB rule
Identification ofundiscovered canal
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Localization Of ForiegnObject
The recommended radiographic techniqueare:
Maxillary area
1.Incisor zoneStereoscopicLateral profileOcclusal
2.Cuspid zoneStereoscopicLateral profileOcclusal
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3.Bicuspid and molar zone Periapical Occulusal
Mandibular area1. Incisor zone Periapical Lateral profile Occlusal2.Posterior zone Periapical Occulusal
3.Third molar zone Periapical Lateral oblique Occlusal
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Foreign Body Localization
In Maxillary SinusRecommended technique include
Orthopantomogram
Waters view
Lateral skull
Computed tomography
MRI
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