L2 Intraoral Radiography

Intraoral Radiography¹

Dr Dayea Oh OMF Radiologist

Learning Objectives²

• By the end of the lecture, the student should be able to:
  • Understand Intraoral Radiography techniques:
    • Bitewing radiographs
    • Periapical radiographs
      • Paralleling
      • Bisecting Angle
    • Occlusal radiographs
  • Understand localisation of an object using intra-oral radiographs
    • SLOB rule
  • Know technical errors in taking intraoral radiographs

Basic Radiographic Terminology³⁴

Radiopaque vs Radiolucent

Fig. 1.1 A typical dental radiograph. The image shows the various black, grey and white radiographic shadows. The metallic amalgam fillings have totally stopped the X-ray beam so they appear white or radiopaque.

Right Posterior Bitewing Radiograph

Conventional Radiograph = 2D picture made up of a variety of black, white and grey superimposed shadows

• The white or radiopaque shadows on a film represent the various dense structures within the object which have totally stopped the X-ray beam.
• The black or radiolucent shadows represent areas where the X-ray beam has passed through the object and has not been stopped at all.

Overview of Intraoral Radiography⁵

‘Intra’ = inside ‘oral’ = mouth

Radiography – the techniques involved in producing the various radiographic images Radiology – the interpretation of radiographic images (radiographs)

Types of Intraoral Radiographs⁶⁷⁸

THREE (3) Types

1. Bite-wing Radiographs (BW)
2. Periapical Radiographs (PA)
3. Occlusal Radiographs / Occlusographs

Upper (or Maxillary) Left Posterior Periapical (PA)

Anterior Maxilla Occlusograph

Analogue Film Sizes⁹

Analogue radiography → images are chemically processed

FIVE (5) Sizes

1. Size 0
   • Used in children for both PA and BW
2. Size 1
   • Used for adult anterior PA (using paralleling technique)
3. Size 2
   • Used for adult posterior PA & BW
   • Used for adult anterior PA (using bisecting-angle technique)
   • Used for occlusographs in children
   • Most commonly used
4. Size 3
   • Extra-long BW (not commonly used)
5. Size 4
   • Used for occlusographs in adults

On the right side, displayed in a graphic form:

• 0: CHILD PA, BW
• 1: ADULT ANTERIOR PA
• 2: ADULT PA, BW
• 4: ADULT OCCLUSAL FILM

Bitewing Radiography

Indications and Coverage¹⁰¹¹¹²

Bitewing (BW) Radiographs Indications Film holder vs Bite tab

A B C A B C

BW Coverage¹³

ADULT

• size 2 film
• Distal canines
• Premolars
• Molars

CHILD

• size 0 film
• Canine
• All primary molars
• Crown of first permanent molar (if erupted)

BW Coverage

“LEFT POSTERIOR BITEWING” Radiograph

Patient and Beam Positioning

Patient Position¹⁴

• Remove all dentures, glasses and other metallic objects (e.g., piercings in line of primary beam)
• Patient’s head is supported by head-rest (of dental chair)
• Patient bites on to the holder/tab
• Ideally, the occlusal plane is parallel to the floor (sit-up position)

Beam / X-ray Cone Position

• Parallel to, and directed through, the occlusal plane

FILM IS PARALLEL TO THE CROWNS X-RAY BEAM DIRECTED THROUGH THE OCCLUSAL PLANE AND CONTACT POINTS PATIENT BITES ON PLASTIC ARM TO STABILIZE HOLDER

Bitewing Technique Using Film Holders¹⁵

Film Holder¹⁶

Use the holder at all times, if possible

VERTICAL AND HORIZONTAL ANGULATIONS ESTABLISHED BY THE HOLDER

LESS TECHNIQUE SENSITIVE

Receptor Placement. Place the receptor between the tongue and the teeth, far enough from the lingual surface of the teeth to prevent interference by the palate on closing and parallel to the long axes of the teeth. The anterior border of the receptor should extend beyond the contact area between the mandibular canine and the first premolar. Hold the receptor in place until the patient’s mouth is completely closed. Holding the receptor while closing prevents it from being displaced distally.

Note: the film / receptor is sitting far away from the teeth when used with holder (thus, not creating any angulation)

Bitewing Technique Using Adhesive Tabs

Paper / Adhesive Tab¹⁷

• Horizontal and vertical angulations of primary beam must be manually adjusted by operator
• No guidance unlike that provided by a film holder
• Very technique sensitive
• Unrepeatable

Horizontal Alignment of the Cone¹⁸

no film holder

WHY?

• Ensures the beam will clear the contact points so we can detect interproximal caries
• Ensure we cover all the film with the cone

HOW?

• Ensure that the film covers all the teeth
• Try to keep the film as close to the lingual surfaces of the teeth as possible
• Avoid bending the film
• Align the cone so that it is parallel to the arch

wrong horizontal alignment ❎ - overlapping of teeth

FIG. 9-4

Horizontal overlapping of crowns is the result of misdirection of the central ray.

Vertical Alignment of the Cone

no film holder

• 20º

• 0º

• +8 to +10

• AIM FOR PRIMARY BEAM TO PASS +8 to +10 FROM THE OCCLUSAL PLANE

• WE ONLY ADJUST THE VERTICAL WHEN USING TABS NOT FILM HOLDERS!!

The film / receptor sits right next to the teeth, creating slanting

Clinical Problems and Solutions

Clinical Problems¹⁹

• Mandibular Tori
  • Bone overgrowth on the lingual surface of the mandible
  • Difficult to place film
  • How to correct: Use the thinnest film (e.g., analogue film or digital PSP plate) and place it lingual to the torus
• Missing Teeth
  • Difficult to stabilise / hold film
  • How to correct: Place cotton rolls in the edentulous space to prevent film rotation

If you examine the patient first you will avoid the majority of mistakes & retakes

Periapical Radiography

Indications²⁰

Paralleling Technique Vs Bisecting Angle Technique

Indications and Coverage Requirements²¹²²

Periapical = around the apex

The intention is to visualize the crown, root and periapical tissues

Indications²³

• Periapical inflammation / pathology
• Root resorption
• Root fractures
• Endodontic therapy (pre, peri & post)
• Localisation of impacted, missing, supernumerary teeth and foreign bodies
• Implant status

Techniques

1. Paralleling (long cone)
2. Bisecting Angle

A

• Long axis of the film packet vertical
• Anterior teeth
• 2–3 mm beyond the incisal edge

B

• Long axis of the film packet horizontal

• Posterior teeth

• 2–3 mm beyond the occlusal plane

• Cover 2-3 mm beyond the crowns

• Demonstrate all roots

• Demonstrate the apical tissues

‘occlusal dot’ marked on film

Ideal PA²⁴

Sufficient film to record the apical tissues

Parallel X-ray beam meeting both the tooth and film at right angles

Film and tooth parallel and in contact

Ideal Tooth/Film relationship not possible to achieve because of anatomic limitations Techniques used in periapical imaging are therefore a compromise from this ideal

• Same size

• Same shape

• Good contrast

• Good detail

• Film parallel to the long axis of the tooth

• Primary beam perpendicular to the film

The Paralleling Technique²⁵²⁶

The longer the cone, the more parallel the beam

A Short spacer cone Diverging X-ray beam Extensive magnification of the image

B Long spacer cone Near-parallel X-ray beam Minimal magnification of the image

Fig. 8.3 Diagrams showing the magnification of the image that results from using A a short cone and a diverging X-ray beam and B a long cone and a near-parallel X-ray beam.

Examples of Film Holders²⁷

With PID guidance rings

Paralleling technique always requires film holders.

• Optimally achieved using film holders with PID guidance rings
• ++ Accuracy
• Less technique sensitive - horizontal and vertical angulations determined by film holder
• Recommended for:
  • Endodontic therapy = accurate measurement of length is critical
  • Long term evaluation of crestal bone height around implants

Advantages and Disadvantages²⁸

• Dimensionally accurate
• Accurate determination of bone height
• Accurate assessment of dental caries
• Reduced superimposition of the zygoma
• Reduced skin exposure due to greater kVp and parallel beam

Disadvantages

• More difficult to place film
• More uncomfortable for the patient
• Higher kVp machine required
• Long cone and film holders required

The Bisecting Angle Technique²⁹³⁰

CENTRAL RAY OF X-RAY BEAM AIMED THROUGH APEX

BISECTING LINE

FILM

• X-ray beam is directed perpendicular to the bisecting line
• Vertical angulation must be determined manually
• Receptor is placed as close to tooth as possible

Central axis of tooth

Imaginary bisector

Collimated beam

Central ray

Receptor

In any 90-degree arc, there is one angle (bisecting angle) that will allow an x-ray beam to cast an accurate shadow of the tooth on the film.

[Image showing close-up of dental film holder in patient’s mouth]

Snap-A-Ray / “Alligator”

Note: no beam aiming device

https://dooclip.me/video/bzreH0NM4fk?id=bzreH0NM4fk

Horizontal and Vertical Angulation³¹

Central ray of the X-ray beam aimed through the tooth apex

Long axis of the tooth

Bisecting line

Long axis of the film

2-3 mm of film visible beyond the incisal edge

Vertical angulation

Horizontal Angulation

• Horizontal angulation must be corrected manually
• PID → Same as the bite tab technique in bitewing (BW)

Vertical angulation faults

Modified Techniques for Anterior Teeth³²

Modified bisecting angle technique – upper anterior

CONE A c film D X° B

“Sao Biscuit” technique for kids

Modified bisecting angle technique – lower anterior

C b Y° A CONE film

Occlusal Radiography³³³⁴

Occlusal Radiographs / Occlusographs

• Largest intraoral film
• Will visualize hard palate, floor of mouth, dentition

Demonstrates:

• Trauma / pathology
  • Eg. Alveolar bone fracture, Salivary stones, etc.
• Localization unerupted/impacted teeth
• Localization supernumerary teeth
• View developing anterior dentition

Maxillary Occlusal Projections³⁵

Maxillary Anterior Occlusal³⁶

Above the nose bridge

Primary beam +65° from film

This projection shows the palate, zygomatic processes of the maxilla, anteroinferior aspects of each antrum, nasolacrimal canals, teeth from second molar to second molar, and nasal septum.

Vertex Occlusal³⁷

Above the head → more anatomic structures exposed 😞

Very rarely used - no longer recommended

Dosage +++ Proximity to retinal tissues

Mandibular Occlusal Projections³⁸

Mandibular True Occlusal³⁹

Primary beam perpendicular to film

This projection reveals the lingual and buccal plates of the mandible from second molar to second molar. When this view is made to examine the floor of the mouth (e.g., for sialoliths), the exposure time should be reduced to half the time used to create an image of the mandible.

Localization Techniques⁴⁰⁴¹⁴²

Localisation of Objects Using Intra-oral Film

TO DETERMINE:

• Bucco-lingual location of impacted teeth such as unerupted ectopic canines
• Location of a foreign body in the bucco-lingual dimension

Handy if you don’t have access to 3D imaging e.g. Cone Beam CT

Techniques for Localisation

• Two Techniques
  1. Tube Shift Technique / Parallex Technique / Clark’s Rule
     • Horizontal Shift
     • Vertical Shift
  2. Right Angle Technique / Miller’s Technique

The Tube Shift Technique⁴³⁴⁴

#1 - The Tube Shift Technique

• Two PA images taken
• Film #1 = centered over area of interest and taken
• Film #2 - tube is shifted EITHER HORIZONTALLY OR VERTICALLY 30-40º and second image is taken
• Tube may be shifted in either the HORIZONTAL or VERTICAL directions
• The direction of motion of the impacted tooth/foreign body relative to the tube movement shows its location

Same Lingual, Opposite Buccal (SLOB rule or Clark’s Rule)

Horizontal Tube Shift^45464748

(Normal Position)

MESIAL
Lingual
DISTAL

MESIAL

DISTAL <—> MESIAL

Right upper / maxillary periapical (paralleling technique)

DISTAL SHIFT**

MESIAL SHIFT**

MESIAL DISTAL DISTAL MESIAL Lingual Buccal

Vertical Tube Shift^4950515253

VERTICAL TUBE SHIFT TECHNIQUE

Right lower / mandibular periapical (paralleling technique)

Increasing vertical angulation (Ascending)

Lingual Buccal

DECREASE VERTICAL ANGULATION (Descending)

Lingual Buccal

Vertical Tube Shift Technique using Occlusograph & Extra-oral Panoramic Radiograph

QUIZ

• What types of I/O radiographs are these?

  1. Right Posterior BW + Right Upper Posterior PA
  2. Left Posterior BW + Left Lower Posterior PA
  3. Right Posterior BW + Right Lower Anterior PA
  4. Right Posterior BW + Right Lower Posterior PA
  5. Left Posterior BW + Left Upper Posterior PA

• Which technique was used to locate the ‘radiopacity’?

  1. Horizontal Tube Shift
  2. Right Angle Technique
  3. Vertical Tube Shift

• Where is the radiopacity (arrow point)?

  1. Lingual
  2. Buccal

The Right Angle Technique⁵⁴⁵⁵

TECHNIQUES FOR LOCALIZATION

#2 - The right angle technique (Miller’s Technique)

Two radiographs are taken. The second is taken at right angles to the first.

E.g. periapical + true occlusal film

• The occlusal film will determine the bucco-lingual position of the object (Not commonly practiced)

Radiographic Errors and Film Faults

Film Faults⁵⁶

• Errors in the surgery
• Errors in the darkroom (not covered in this lecture)
• Errors in film processing (not covered in this lecture)

Common Technical Errors in Surgery⁵⁷

Errors in the Surgery⁵⁸

• Overexposure – dark image
• Underexposure – light image
• Patient motion – blurred image
• Film exposed to white light before processing
  • Analogue film or digital Photostimulable Phosphor (PSP) plate
• Not removing foreign objects such as ear-rings, spectacles, body jewellery (including tongue studs), hair clips, hearing aids, neck chains
• Poor patient positioning and incorrect technique – distorted images
  • Cone-cutting
  • Elongation
  • Foreshortening
• Damaged Film
• Double Exposed Film

A B A B A B C D A

For your own learning… Identify Errors

Identification of Processing and Positioning Faults⁵⁹

• Partial immersion in developer
• Over developed
• Fixer splashed on film before processing
• Cone cutting
• Elongation
• Not washing adequately post development or developer on film before processing
• Foreshortening

1. Not exposed
2. Left in wash over-night
3. Put into fixer before developer

• Film positioned backwards

Footnotes

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