Quartz 4

L16 Endo Diagnostic radio_formatted_text

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Endodontic Diagnostic Radiography1

Outline

  • Principles of Radiography
  • Positioning Devices
  • Radiographic Interpretation
  • Tube Shift Techniques
  • Endodontic “Working” Radiography
  • Specific Techniques for Each Tooth

Uses of Radiography in Endodontics2

  • Diagnosis

  • Pre-operative assessment of root canal anatomy

  • “Working” films

  • To establish the working length of the root canal.

    • To check the fit of the master gutta-percha point.

  • Technical assessment of treatment

  • Review healing and tissue responses -

    • After endodontic treatment
    • After surgery
    • After trauma

Radiography Techniques3

Info

The geometry of the X-ray beam, the object (tooth), and the sensor/film position dramatically affects the resulting image. An incorrect setup can lead to significant distortion.

  • Elongation: A shallow vertical angle can make the tooth appear much longer than its actual length (e.g., a 13mm tooth appearing as 19mm).
  • Foreshortening: A steep vertical angle (from a more apical direction) can make the tooth appear much shorter (e.g., a 13mm tooth appearing as 9mm).
  • Parallel technique
  • Bisecting angle technique

Parallel Technique4

Note

In the parallel technique, the film or sensor is placed parallel to the long axis of the tooth being radiographed. The central X-ray beam is then directed perpendicularly (at 90 degrees) to both the tooth and the sensor.

  • Ideal Image Characteristics (Upper Posterior):
    • The buccal roots of premolars and molars appear slightly shorter than the palatal roots.
    • The palatal root of a molar is ideally positioned between the two buccal roots.

Bisecting Angle Technique

Note

This technique is used when the sensor cannot be placed parallel to the tooth. The sensor is placed at an angle to the tooth’s long axis. The operator must then visualize an imaginary line that bisects the angle formed by the tooth and the sensor. The central X-ray beam is directed perpendicularly to this imaginary bisecting line.

  • Image Characteristics (Upper Posterior):
    • The buccal roots of premolars and molars appear significantly shorter than the palatal roots.
    • The zygoma is often superimposed over the apex of the palatal root of the maxillary first molar.

Parallel vs. Bisecting Angle5

Info

Changing the radiographic technique results in a different visual representation of the same anatomical structures. The parallel technique generally provides a more geometrically accurate image compared to the bisecting angle technique.

Effect of radiographic technique upon prediction of tooth length in intraoral radiography

Bhakdinaronk A, Manson-Hing LR. OS:OM:OP 1981; 51: 100-107.

Study: Radiographic technique and prediction of tooth length (Bhakdinaronk & Manson-Hing 1981)67

  • Methodology:

    • Used four different film holders:
      • Rinn XCP
      • Styrofoam bite block
      • Haemostat with bite block
      • Patient’s finger
    • Compared Parallel and Bisecting Angle techniques
    • Compared radiographic tooth length to the actual tooth length measured after extraction

  • Results:

    • Most accurate to least accurate:
      Rinn XCP+ Parallel Technique
      Styrofoam bite block
      Haemostat with bite block
      Patient’s finger
    • Patient’s finger technique had the greatest amount of film bending

  • Conclusions:

  • ==The parallel technique consistently produced more accurate images than the bisecting angle technique across all holder types.==

    • Parallel technique with the RINN XCP film holder was the most accurate technique
    • Beam guiding film holders were more accurate than techniques without guidance
    • Film holders with backing were more reliable than holders with no support for the film

  • Magnification:

    • All techniques and all tooth types had some magnification of the image
    • Magnification range: 6.4% - 16.2%
    • Average: 10% with the parallel technique

Parallel Technique Details891011

  • Parallel technique is more accurate than the bisecting angle technique
  • BUT still have approx. 10% magnification

Cause of Magnification

X-rays are generated from a point source within the machine head and diverge as they travel towards the sensor. They do not travel in perfectly parallel lines. This divergence causes the image projected onto the sensor to be larger than the actual object.

Clinical Implication

Relying on this magnified measurement for working length can lead to instrumentation beyond the apical foramen, causing damage to periapical tissues.

  • Since the x-rays come from a “point source”
  • Can minimise with rectangular collimation and long cones

Effect of Magnification12

  • A tooth that is 21.0 mm long would appear to be about 23.0 mm on the radiograph
    • Since 10% of 21.0 mm is 2.1 mm

Modified Parallel Technique1314

  • To overcome the 10% magnification that occurs with the parallel technique

  • Method:

    • Increase the vertical angle of the central beam by ~ 15°

  • Rationale

  • The increased vertical angulation intentionally foreshortens the image by about 10%, compensating for the magnification effect and producing a more dimensionally accurate representation of the tooth's true length.

    • Foreshortens the image slightly

Positioning Devices151617

Rinn XCP Kit

Note

The Rinn XCP (Extension Cone Paralleling) kit is a highly recommended positioning device for diagnostic radiography. It consists of a bite block to hold the sensor, a metal aiming arm, and a plastic aiming ring to guide the X-ray cone.

  • Modern kits are color-coded (e.g., blue for anterior, yellow for posterior) to simplify assembly. Older versions were all white plastic.
  • The device is assembled differently for anterior (vertical sensor orientation) and posterior (horizontal sensor orientation) teeth.

Principles for All Radiographic Techniques

  • Must be simple to use
  • Use a positioning device with beam alignment
  • Must give an accurate image
  • No film distortion, bending, etc
  • Stable position with “no hands” needed
  • Reproducible image over time

Rinn XCP Kit Adherence to Principles1819

  • ✔️ Must be simple to use
  • ✔️ Use a positioning device with beam alignment
  • ✔️ Must give an accurate image (+ modified parallel tech)
  • ✔️ No film distortion, bending, etc

Success

The rigid backing plate on the bite block prevents the sensor from bending against oral structures like the palate. This avoids the ‘stretched’ appearance common with bent films, which can create misleading artifacts that mimic pathology.

  • ✔️ Stable position with “no hands” needed

  • ✔️ Reproducible image over time

  • Use a positioning device with beam alignment

Rinn XCP Kit image with arrows demonstrating components.

  • Must give an accurate image

    • Study: Radiographic technique and prediction of tooth length (Bhakdinaronk & Manson-Hing 1981)
      • Most accurate to least accurate:
        • Rinn XCP
        • Styrofoam bite block
        • Haemostat with bite block
        • Patient’s finger
      • Patient’s finger technique had the greatest amount of film bending
      • + Parallel Technique

  • Must give an accurate image

    • Study: Standardized techniques for monitoring healing (Andreasen et al Eur J Orthod 1990)
      • RINN with the Parallel Technique
      • Average deviation was only:
        • Tooth length: 0.5 mm
        • Crown width: 0.2 mm

  • No film distortion, bending, etc

  • Reproducible image over time
    • Study: Standardized techniques for monitoring healing (Andreasen et al Eur J Orthod 1990)
      • RINN with the Parallel Technique
      • Average deviation was only:
        • Tooth length: 0.5 mm
        • Crown width: 0.2 mm

Applications of the Rinn XCP Kit2021222324

  • ✔️ Use for ALL diagnostic radiographs (NOT just Endo!)
  • ✔️ Use for all post-RCF and follow-up radiographs
  • ✔️ Use for trauma reviews
  • ✔️ Use whenever Rubber Dam is not in place

Using the Rinn Holder25

Anterior Teeth

  • ==Setup: Use the anterior (blue) bite block, which orients the sensor vertically.==
  • ==Correct Cotton Roll Placement: The manufacturer’s diagram often incorrectly shows placing a cotton roll between the bite block and the opposing teeth. This can cause the sensor to tilt, leading to elongation.==
    • ==Correct Method: Place the cotton roll between the tooth being radiographed and the bite block. This ensures the sensor remains parallel to the tooth.==

Upper Anterior Teeth

Tip

The sensor must be placed far back in the mouth (often in the first molar region) to achieve parallelism due to the curvature of the palate. This increases the object-to-film distance, reinforcing the need for the modified parallel technique to combat magnification.

Posterior Teeth2627

  • ==Setup: Use the posterior (yellow) bite block, which orients the sensor horizontally.==

  • ==Important Note: The aiming ring is offset for posterior shots. The device must be assembled correctly for the specific quadrant (e.g., upper left/lower right vs. upper right/lower left) to avoid a large cone-cut error.==

  • UL / LR

  • UR / LL

Upper Posterior Teeth

Tip

To achieve parallelism, the sensor is often placed near the midline of the palate, which is its highest point. A cotton roll is placed between the teeth being radiographed and the bite block to stabilize the device and maintain a parallel orientation.

Lower Posterior Teeth28

Tip

A cotton roll is usually not necessary because the floor of the mouth relaxes when the patient closes, providing ample space for the sensor. Occasionally, a cotton roll may be placed on the opposing arch to stabilize the bite if there isn’t firm contact between the upper teeth and the bite block.

Radiographic Interpretation29

The Importance of Accurate Radiographs30

  • ✓ Correct Diagnosis

Examples of Misdiagnosis from Poor Radiographs

  • Example 1: A poorly angulated and underexposed radiograph suggested a distal periodontal pocket on a molar. A subsequent, well-angulated radiograph taken with a Rinn holder revealed no pocket, but rather an open mesial crown margin that was the true cause of the patient’s pulpitis.
  • Example 2: A radiograph of an anterior tooth taken with a horizontally-oriented and bent film created the false appearance of a developmental root defect. A correctly taken radiograph with a vertically-oriented film showed normal anatomy.
  • Example 3: A series of non-standardized radiographs taken to monitor traumatized teeth showed huge variations in apparent tooth length. This made estimating the working length for subsequent root canal treatment impossible, leading to initial instrumentation far beyond the apex.
  • Size 0 - 22 x 35 mm - 770 mm²

Warning

The use of Size 0 film is very limited as it captures a small area, providing minimal diagnostic information.

  • Size 1 - 24 x 40 mm - 960 mm²

  • Size 2 - 31 x 41 mm - 1271 mm²

  • Size 2 - standard film used for PA’s

  • Should be used whenever possible for posterior teeth (horizontally) and upper anteriors (vertically).

  • Size 1 - narrow arches, anterior teeth

  • ==Often preferable for the lower anterior region where the arch is narrow. It has the same length as a size 2 but is narrower.==

  • Size 4 - occlusal views

The Importance of Accurate Radiographs30

  • Endodontics
    • Root Canal Length Estimation

Factors Affecting Interpretation Accuracy3435

  • Film type & exposure time

  • Technique & angulations used

  • Standard of developing

  • Endodontic file size used

  • Superimposition of other structures

  • The mental foramen or incisive foramen can be superimposed over a root apex, mimicking a periapical lesion.

    • Bone processes, roots, canals, etc

  • Foramen position with respect to root apex

    • Mesial / Distal or Buccal / Lingual

  • Density of bone

    • Trabeculae, cortical plate

  • Amount of bone that has been resorbed

    • ? How much is required

Bone Loss Required for Radiographic Detection36

  • How much bone loss is required before a radiolucency can be reliably detected on a PA radiograph ??
    • Cortical plate involved
      • Bender & Seltzer 1961(a)
    • Junctional trabeculae involved
      • Bender & Seltzer 1961(b)

Info

The actual amount likely varies between patients depending on their individual bone anatomy.

  • Cancellous bone involved
    • Shoha et al 1974, Pitt Ford 1984
  • Lamina dura destroyed
    • Lee & Messer 1986, Barbat & Messer 1998

Correlation with Histological and Surgical Findings37

  • Poor correlation between radiographic interpretation and the histological findings
    • Bender & Seltzer 1964, Pitt Ford 1984
  • Lesion always larger histologically than on radiograph
    • Bender & Seltzer 1964

Balloon Analogy

Think of a balloon. The radiograph primarily shows the densest part of the lesion (the middle of the balloon), while the less-demineralized peripheral areas are obscured by the surrounding bone.

  • Lesion always larger surgically than on radiograph
    • Farman et al 1998, Scarfe et al 1999

Tube Shift Techniques38

Note

Tube shift techniques involve changing the angle of the X-ray beam to gain a quasi-three-dimensional perspective and separate superimposed structures.

  • Vertical Shift
    • Increased angle
    • Decreased angle
  • Horizontal shift
    • Mesial
    • Distal

Vertical Shift39404142

  • Increased angle

  • Decreased angle

  • Decreased angle

    • elongates the image
    • NO diagnostic value
    • NO practical value

Danger

This is never done intentionally.

  • Increased angle
    • 15º vertical shift
      • Modified parallel technique
      • Provides more apical detail and definition
    • Occlusal views
      • Esp. useful for trauma diagnosis
        • Root Fractures & Lateral Luxation

Root Fractures43

Lateral Luxation44

Section from Occlusal film

Horizontal shifts

The SLOB Rule

The SLOB rule (Same Lingual, Opposite Buccal) is used for interpretation. When the tube head is shifted, the object that is positioned more Lingually will appear to move in the Same direction as the tube head shift. The object that is more Buccally will appear to move in the Opposite direction.

  • Mesial

  • Distal

  • Used to separate objects that are otherwise superimposed over each other

  • Can help to indicate the “3rd dimension”

Applications of Horizontal Shifts45

  • ==Separating Canals: On a straight-on view of a lower incisor or the mesial root of a mandibular molar, two canals (buccal and lingual) will be superimposed. A mesial or distal shift will separate them on the image, allowing for their identification.==
  • ==Separating Roots: A straight-on view of a maxillary molar places the palatal root between the two buccal roots. A mesial shift will move the palatal (lingual) root mesially, while a distal shift will move it distally.==
  • ==Differentiating Anatomy from Pathology: A tube shift can move an anatomical structure (like the incisive foramen) off of a root apex, confirming that a suspected radiolucency is not endodontic pathology but rather a superimposed normal feature.==
  • ==Identifying Missed Anatomy or Problems: A tube shift can reveal previously unseen features, such as a third canal in a premolar or a mid-root perforation that is hidden on a straight-on view.==

Straight View4647

MesialDistal

Mesial Distal

Endodontic Diagnostic Radiography1

W/Prof. Paul V. Abbott AO48

Mesial Distal

Radiographic Reporting

Todo

The process of radiographic interpretation is not complete until a formal report is written and included in the patient’s clinical records. It is not enough to simply look at the image and make a decision; the observations must be documented.

Outline

  • Principles of Radiography
  • Positioning Devices
  • Radiographic Interpretation
  • Tube Shift Techniques
  • Endodontic “Working” Radiography
  • Specific Techniques for Each Tooth

Note

This lecture explores the principles and techniques of diagnostic radiography in endodontics. While some concepts apply to working radiographs taken during treatment (which have been discussed previously), the focus here is on the diagnostic phase.

Footnotes

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Graph View

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