Radiography Bisecting Angle

8/6/2019 Radiography Bisecting Angle

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Periapical radiographPeriapical radiograph

Two tech:Two tech:

Parallel tech.Parallel tech. Bisecting angle tech.Bisecting angle tech.


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Bisecting the angle techniqueBisecting the angle technique

Principle:Principle:

Based on the age old theorem, CiezynskisBased on the age old theorem, Ciezynskisrule of isometry which states that torule of isometry which states that totriangles are equal when they share atriangles are equal when they share acommon side and have 2 equal angles.common side and have 2 equal angles.

Applied by placing the film as close asApplied by placing the film as close aspossible to the lingual surfaces of the teeth,possible to the lingual surfaces of the teeth,resting on palate or floor of the mouth.resting on palate or floor of the mouth.


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The planes ofThe film and the longThe planes ofThe film and the longaccess of the teeth form an angle, whenaccess of the teeth form an angle, when

this angle is bisected by imaginary line 2this angle is bisected by imaginary line 2equal angles are formed and a commonequal angles are formed and a commonside, the third line of the both trianglesside, the third line of the both trianglesare formed by the central rays which passare formed by the central rays which pass

perpendicular to the imaginary bisectingperpendicular to the imaginary bisectingline.line.


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So that the principle applied to the intraSo that the principle applied to the intra--

oral radiographic film is that:oral radiographic film is that:

the central ray must pass through thethe central ray must pass through the

apex of the tooth, perpendicular to theapex of the tooth, perpendicular to theimaginary line bisecting the angle formedimaginary line bisecting the angle formedby the mean plane of the film and theby the mean plane of the film and the

long axis of the toothlong axis of the tooth


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Thumb or forefinger are used to support the filmThumb or forefinger are used to support the filmfrom the lingual surface. This have severalfrom the lingual surface. This have severaldrawbacks:drawbacks:

Unnecessary radiation to patients finger.Unnecessary radiation to patients finger.

Bending of film by using excessive force.Bending of film by using excessive force.

Slipping of he film withoutoperators knowSlipping of he film withoutoperators know

kedge.kedge.


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Note:Note:

artery forceps are better in use instead ofartery forceps are better in use instead ofthe thumb or forefingers in the situationsthe thumb or forefingers in the situationswhere there is no device to hold the filmwhere there is no device to hold the filmin the position.in the position.


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ProcedureProcedure

PreparationPreparation

Patient positionPatient position

Film placementFilm placement Tube head angulationTube head angulation

Central rayCentral ray

Exposure factorsExposure factors


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Patients PositionPatients Position

Head should be upright, midsagittal plane shouldHead should be upright, midsagittal plane shouldbe perpendicular to the floor and occlusal planebe perpendicular to the floor and occlusal planeparallel to the floor.parallel to the floor.

AlaAla--tragus (corpus) line should be parallel to thetragus (corpus) line should be parallel to thefloor when the maxillary projection is taken.floor when the maxillary projection is taken.

Mandibular occlusal plane should be parallel toMandibular occlusal plane should be parallel to

the floor when the mandibular projection isthe floor when the mandibular projection istaken.taken.


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Film PlacementFilm Placement

The stippled side toward the tube.The stippled side toward the tube.

The incisal or occlusal edge of the filmThe incisal or occlusal edge of the filmshould be positioned against the teethshould be positioned against the teethwith the edge of the film extending justwith the edge of the film extending justbeyond the teeth.beyond the teeth.


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Following chart can be used for generalFollowing chart can be used for general

guide:guide:

ProjectionProjection maxillarymaxillary mandiblemandibleIncisorsIncisors +60+60 --1515

CanineCanine +45+45 --2020

PremolarPremolar +30+30 --1010MolarMolar +20+20 --55


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Central RaysCentral Rays

XX--ray beam is directed through the centreray beam is directed through the centreof the area to be radiographed. The apicesof the area to be radiographed. The apicesare used as a guide to the pointof enetry.are used as a guide to the pointof enetry.

In the maxilla the apices areIn the maxilla the apices areapproximately at the level of the corpusapproximately at the level of the corpus

line, and in the mandible above the lowerline, and in the mandible above the lowerborder by 15mm.border by 15mm.


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Exposure factorsExposure factors

6565-- 70 kVp70 kVp 10 mA10 mA

Time according to different teeth.Time according to different teeth.


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ERRORS of Bisecting Angle Tech????ERRORS of Bisecting Angle Tech????

Presentation.Presentation.


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THANK YOUTHANK YOU

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Radiography Bisecting Angle