Intra Oral Radiography

  1. Assessment of Periodontal Status:
  2. Used for assessment of periodontal status for following significant features:
    1. Receding bone height related to C.E.J.
    2. Loss of bone at inter-proximal space or at furcation.
    3. Widening of periodontal space.
    4. Loss of integrity of lamina Dura.
  3. Exodontia:-
    1. For diagnosis and planning of treatment of fractured teeth.
    2. To distinguish between complicated crown fracture (pulpaly exposed) and uncomplicated crown fracture (not pulpaly exposed).
    3. Pre extraction planning for the developmental anomalies.
    4. Assessment of root morphology, resorptive lesion and ankylosis.
    5. Post extraction radiographs for root fragments and other co-lateral damages.
  4. Conservative/Operative Procedures:-
    1. Detection of the dental caries.
    2. Intra operative or post operative radiographs for the demonstration of file, position of gutta percha point in canal, and adequate filling of pulp canal.
    3. Internal resorption, detection of developmental anomalies.
    4. Detection of missing teeth and teeth with developmental
    5. Anomalies E.g.:- dilacerations, supernumerary teeth, fusion etc.
    6. Evaluation of implant postoperatively.
  • X-rays should be emitted from the smallest source of radiation as possible.
  • The X-ray source-to-object distance should be as long as possible.
  • The object-to-receptor distance should be as short as possible.
  • The receptor and long axis of the tooth should be parallel to each other.
  • The X-ray Beam should be directed perpendicular to the tooth and receptor.
  • Bisecting angle technique.
  • Paralleling technique.
  • Paralleling technique.

Paralleling technique is the most accurate intraoral radiographic technique, meeting four of the five principles of accurate image projection, while only three of accurate image projection is met by using bisecting angle technique.

  • Also known as “right angle technique” or “long cone technique”.
  • Used for both periapical and bitewing radiographs.
  • In this technique the film receptor should be placed parallel to the crown and root of the teeth being imaged and the central ray of the x-ray beam is directed at the right angle to the teeth and film.
  • Patient is positioned with head support with occlusal plane horizontal.
  • The orientation of the film, teeth and the central ray minimized the geometric distortion.
  • Yellow colour coded posterior holder (RINN XCP).
  • Blue colour coded anterior holder (RINN XCP).
  • Red colour coded superbite posterior holder (for bitewing).
  • A mechanism for holding the film packet parallel to the teeth that prevents the bending of the film.
  • A bite block or platform.
  • Beam Aiming Device:-This may or may not prevent the collimation of the beam.
  1. Less magnification so geometrically accurate image can be produced.
  2. The shadow of zygomatic process appears above apices of the molar teeth.
  3. Good representation of periodontal bone level.
  4. Minimal foreshortening or elongation gives accurate information about the periapical region of image of teeth.
  5. Detection of a proximal caries because of well demonstration of crown of the teeth.
  6. Automatically determine vertical and horizontal angulations by positioning device if placed correctly.
  7. No coning of or cone cutting as the x-ray beam is aimed accurately ay the centre of the film.
  8. Reproducible radiographs are possible as relative postures of film & teeth and x ray been is always maintained irrespective of patient’s position.
  1. Positioning of the film can be uncomfortable for the posterior teeth.
  2. Inexperienced operator can face difficulty in placing the holders in the mouth.
  3. Cannot be performed satisfactory using short focal spot to skin distance.
  4. Difficulty in placing the holder in lower third molar regions.
  5. Holders used to be autoclaved or disposable.
  6. Cannot be done in cases of shallow flat palate.
  7. Sometimes apical region of the teeth may appear near the edge of the film. 

  IMAGE FIELD

POINT OF ENTRY OF CENTRAL RAY

  Maxillary central Incisor

High on lip, in midline just below the septum of nostril.

  Maxillary lateral Incisor

High on lip, about 1 cm from midline.

  Maxillary canine

Through the canine eminence, at about the intersection of distal and inferior borders of ala of the nose.

  Maxillary premolar

Through the centre of 2nd premolar root, this point is usually below the pupil of the eye.

  Maxillary molar

Below the outer cantus of the eye and the zygoma at the position of maxillary 2nd molar.

  Maxillary distal oblique molar projection

At maxillary 3rd molar region below the middle of zygomatic arch, distal to lateral cantus of eye.

  Mandibular centrolateral incisor projection

Below the lower lip about 1 cm lateral to the midline.

  Mandibular Canine

Nearly perpendicular to the ala of the nose, over the position of canine and approx 3 cm above inferior border of mandible.

  Mandibular Premolar

Below the outer canthus of eye approx 3 cm above inferior border of mandible.

  Mandibular Molar

Below lateral canthus of eye approx 3 cm above inferior border of mandible.

  Mandibular distal oblique molar projection

About 3 cm above antigonal notch or inferior border of mandible in line with anterior border of ramus.

  • Also k/a short cone technique.
  • The bisecting angle technique is based on geometric principle that states that two triangles are equal if they have two equal angles and a common side,it is called “Cieszynski’s Rule of Isometry”.
  • In the bisecting-angle technique the central ray is directed at a right angle to the imaginary plane that bisects the angle formed by the film and the central axis of the object. This method results in an image that is the same length as the object.

“SNAP-A-RAY” or “Bisecting Technique Instrument”.

  • The occlusal plane of teeth to be radiographed should be parallel to the floor.
  • Saggital plane should be perpendicular to the floor for maxillary Projection, here ala-tragus line is parallel to the floor.
  • In Mandibular projection, mandibular occlusal plane changes when mouth is opened. So patient’s head should be tilted slightly backward so that occlusal plane of the mandible should parallel to the floor when mouth open. Here lip commissural – tragus line should be parallel to the floor.
  • Horizontal angulation is the side-to-side movement of the tube head or x-ray beam
  • Correct horizontal angulation is when the central ray is perpendicular to the facial surfaces of the teeth and parallel to the mesial and distal surfaces.
  • In the horizontal plane the central beam should be aimed through the inter proximal contact areas.
  • Horizontal angulation is determined by shape of arch and position of tooth.

Horizontal alignment errors cause:

  • Image to shift anteriorly or posteriorly.
  • Overlapping of the inter-proximal surfaces.
  • Vertical angulation is the up-and-down movement of the tube head.
  • The angle formed by continuing the line of the central ray until meets the occlusal plane determines the vertical angulation of x-ray beam to the occlusal plane.

  Projection

Maxilla

Mandible

  Incisors

 

+40

-15

  Canines

 

+45

-20

  Premolars

 

+30

-10

  Molars

+20

-5

When occlusal plane is oriented parallel with floor:

  • With positive (+) angulation, the aiming tube is positioned downward.
  • With negative (-) angulation, the aiming tube is positioned upward.
  • Increase vertical angulation – Foreshortening or shortening of the teeth and surrounding structures.
  • Decrease vertical angulation – Elongation or lengthening of the teeth and surrounding structures.
  • Placement of the film is simple and quick.
  • Positioning of the film is comfortable in all areas of the mouth.
  • The image will be of the same length as tooth itself and should be adequate for diagnostic purpose if all angulations are used correctly.
  • Periodontal bone levels are shown poorly.
  • Non reproducible.
  • The shadow of zygomatic process overlies the root of maxillary molars.
  • Horizontal & vertical angles has to be assessed for every patient.
  • The technique required experienced operator.
  • An incorrect horizontal angulation causes overlapping of crown and root.
  • Incorrect vertical angulations will cause foreshortening or elongation of image.
  • Buccal roots of maxillary premolar and molar get foreshortened.
  • Crown of teeth are often distorted thus preventing detection of proximal caries.
  • If central ray is not aimed at the centre of the film coning off or cone cut may result.

  IMAGE FIELD

POINT OF ENTRY OF CENTRAL RAY

  Maxillary central Incisor

In midline, through tip of the nose

  Maxillary lateral Incisor

Through ala of the nose, about 1 cm from midline

  Maxillary canine

Through the canine eminence, through the ala of the nose

Maxillary premolar

Below the pupil of the eye, close to level of ala tragus line

  Maxillary molar

On the cheek in line with outer canthus of eye, below the zygoma and on anteroposterior level with 2nd molar.

  Mandibular centrolateral incisor projection

Below the vermillion border of the lip about 1 cm from the midline.

  Mandibular Canine

Through the canine approx 3 cm from midline

  Mandibular Premolar

Below the pupil of the eye approx 3 cm above inferior border of mandible

  Mandibular Molar

Below lateral canthus of eye approx 3 cm above inferior border of mandible

  • Intraoral periapical radiography.
  • Bitewing radiography.
  • Occlucal radiography.
  • Intraoral periapical radiography.
  • Bitewing radiography.
  • Occlucal radiography.
  • Cone-cuts appear as a clear zone on traditional radiographs after processing, due to the lack of x-ray exposure in the area of the cut.
  • Using digital imaging, the cone cut appears as an opaque or white area.
  • Shape of the cone-cut depends on the type of collimator used when exposing the receptor.
  • If a round collimator is used, a curved cone-cut will appear.
  • Square cone-cuts occur when using a rectangular collimator.

Bitewing radiographs take their name from the original technique which required the patient to bite on a small wing attached to an intraoral film packet.

  • Depicts a clear image of the inter-proximal surfaces of the teeth
  • Detection of inter-proximal caries.
  • Evaluation of maxillary and mandibular alveolar crests.
  • Assessment of periodontal status.
  • Monitoring progression of caries.
  • Assessment of existing restoration
  • Tab or bite platform should be positioned on the middle of film and parallel to the upper and lower edges of film packet.
  • Film packet should be positioned with its long axis horizontally (for horizontal bitewing) or vertically (for vertical bitewing).
  • Posterior teeth and film packet should be as close as possible and should be parallel to each other.
  • In the horizontal plane x ray beam should meet the teeth and film packet at right angle and passes through the all contact areas directly.
  • In vertical plane tube head should be aimed downwards (approx. 50 to 80) to compensate for the upwardly rising curve of monson.
  • The positioning should be reproducible.

Two techniques:

  • Using a tab attached to film packet and aligning the x-ray tube head by eye.
  • Using a film packet holder with beam aiming device to facilitate the positioning and alignment of x-ray tube head.
  • Size 0 (22x35mm) – for small children.
  • Size 1 (24x40mm) – for children.
  • Size 2 (31x41mm) – for adults.
  • Size3 (54x27mm) also available but used occasionally for adults. All posterior teeth can be seen in film.

Technique using tab attached to film packet:

  • Position the patient with occlusal plane parallel to floor.
  • Assess the shape of dental arch.
  • Hold the tab between thumb and forefinger and insert the film in the lingual sulcus opposite the posterior teeth.
  • The anterior edge of film should be positioned to the distal aspect of lower canine, in this position the posterior edge of film extends beyond the mesial aspect of lower third molar.
  • The tab is placed on the occlusal surfaces of lower teeth and patient is asked to close the teeth firmly together on tab.
  • The x-ray beam is aimed directly through the contact areas at right angle to the teeth and film with approx. 50 to 80 downward (+) vertical angulation.
  • Make the exposure.

Technique using simple film packet holder:

Name of film packet holder-

  • Hawe-Neos Kwikbite with simple beam indicating rod.
  • Hawe-Neos Kwikbite with circular beam aiming device.
  • RINN bitewing holder.

Film packet holder has 3 basic components:

  • Mechanism for holdings the film packet parallel to teeth.
  • Bite –platform that replaces the wings.
  • X-ray beam aiming device.
  • Position of x-ray tube head determined by the holder ensuring that x-ray beam is always at right angles to film packet.

Advantages:

  • Simple
  • Inexpensive.
  • Can be used in children.
  • Tabs are disposable.

Disadvantages:

  • Arbitrary, operator-dependent assessment of horizontal and vertical angulations of x-ray tube head.
  • Radiographs are not accurately reproducible so not useful for monitoring the progression of caries.
  • Cone cutting of anterior part of film is common.
  • Tongue can easily displace the film.

Advantages:

  • Simple.
  • Film cannot be displaced by tongue.
  • Technique is less operator-dependent.
  • No cone cut.
  • Holders are autoclavable or disposable.

Disadvantages:

  • Positioning of film holder can be uncomfortable for patient.
  • Holders are expensive.
  • Position of holder in mouth is operator-dependent, therefore not 100% reproducible so still not ideal for monitoring progression of caries.

For Evaluation of:

  • Anterior maxilla and its dentition.
  • Anterior floor of nasal fossa.
  • Teeth from canine to canine.

Patient placement:

  • Sagittal plane of the patient should be perpendicular to the floor.
  • Occlusal plane should be parellel to the floor.

Film placement:

Place the film in mouth with exposure side towards maxilla, posterior border touching the rami and long dimension of film should be perpendicular to sagittal plane.

Projection of central beam:

Project the central ray through tip of the nose toward the middle of the film with approx. +45 degree vertical angulation and 0 degree horizontal angulation.

For Evaluation of

  • Palate.
  • Zygomatic processes of the maxilla.
  • Antero-inferior aspects of each antrum.
  • Nasolacrimal canals.
  • Teeth from second molar to second molar.
  • Nasal septum.

Patient placement:

  • Sagittal plane should be perpendicular to the floor.
  • Occlusal plane horizontal.

Film placement:

  • Place the film, with its long dimension perpendicular to the sagittal plane, crosswise in the mouth.
  • Gently push the film in backward until it contacts the anterior border of the mandibular rami.
  • Stabilize the film by gently closing the mouth.

Projection of central ray:

Direct the central ray at a vertical angulation of +65 degrees and a horizontal angulation of 0 degrees, to the bridge of the nose just below the nasion, toward the middle of the film.

Evaluation of:

  • Quadrant of the alveolar ridge of the maxilla.
  • Inferolateral aspect of the antrum.
  • Tuberosity.
  • Teeth from the lateral incisor to the contralateral third molar.
  • Zygomatic process of the maxilla superimposes over the roots of the molar teeth.

Patient placement:

  • Sagittal plane should be perpendicular to the floor.
  • Occlusal plane horizontal.

Film placement:

  • Place the film with its long axis parallel with the sagittal plane and on the side of interest, with the tube side toward the side of the maxilla in question.
  • Push the film posteriorly until it touches the ramus.
  • Lateral border parallel with the buccal surfaces of the posterior teeth, extending laterally approximately 1 cm past the buccal cusps.
  • Close mouth gently to hold the film in position.

Projection of central ray:

Orient the central ray with a vertical angulation of +60 degrees, to a point 2 cm below the lateral canthus of the eye, directed toward the center of the film.

Evaluation of:

  • Anterior portion of the mandible.
  • Dentition from canine to canine.
  • Inferior cortical border of the mandible.

Patient placement:

Seat the patient tilted back so that the occlusal plane is 45 degrees above horizontal.

Film Placement:

  • Place the film in the mouth with the long axis perpendicular to the sagittal plane and push it posteriorly until it touches the rami.
  • Center the film with the pebbled side (tube side) down.
  • Ask the patient to bite lightly to hold the film in position.

Projection of central ray:

Orient the central ray with -10 degrees angulation through the point of the chin toward the middle of the film; this gives the ray -55 degrees of angulation to the plane of the film.

Evaluation of:

  • Soft tissues of floor of the mouth.
  • Lingual and buccal plates of mandible.
  • Sialolith (exposure time should be reduced one half the time than normal exposure).

Patient placement:

  • Seat the patient in semi reclining position with head tilted back so that ala tragus line perpendicular to floor.

Film placement:

  • Place film in the mouth with its long axis perpendicular to the sagittal plane and with its long axis perpendicular to the sagittal plane and with tube side towards mandible.
  • Anterior border of the film should be approx. 1 cm beyond mandibular incisors.
  • Ask the patient to bite gently on the film to hold it in position.

Projection of central ray:

Direct the central ray at midline through the floor of mouth approx. 3 cm below the chin, at right angles to the centre of film.

  • Soft tissue of half the floor of the mouth.
  • Buccal and lingual cortical plates of half of the mandible.
  • Teeth from lateral incisor to the contralateral third molar. 

Patient placement:

Seat the patient in a semi reclining position with the head tilted back so that the ala-tragus line is perpendicular to the floor.

Film placement:

  • Place the film in the mouth with its long axis initially parallel with the sagittal plane and with the pebbled side down toward the mandible.
  • Place the film as far posterior as possible, then shift the long axis buccally (right or left) so that the lateral border of the film is parallel with the buccal surfaces of the posterior teeth and extends laterally approximately 1 cm.

Projection of central ray:

Direct the central ray perpendicular to the center of the film through a point beneath the chin, approximately 3 cm posterior to the point of the chin and 3 cm lateral to the midline.

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