Intraoral Radiographic Techniques Short Essays

Intraoral Radiographic Techniques Short Essays

Question 1. Paralleling technique/Long cone technique.
Answer.

Paralleling technique

  • In this technique the X-ray film is placed parallel to the long axis of the tooth and the central ray of the X-ray beam is directed at right angles to the tooth and film
  • The film must be placed away from the tooth and towards the middle of the oral cavity
  • The object film distance must be increased
  • It is also referred to as long cone technique

Long Cone Technique Target Film Distance:

  • Target film distance is large
  • This results in less image magnification and better definition

Long Cone Technique  Film Holders:

  • This technique requires film holders

Long Cone Technique  Film:

  • Ideally the size of the film used will depend upon the teeth being radiographed
    • Size 1: used for anteriors
    • Size 2: used for posteriors

Long Cone Technique  Film Placement:

  • The white side of the film always faces the teeth
  • For anteriors the film is placed vertically
  • For posteriors the film is placed horizontally
  • The identification dot on the film is always placed towards the occlusal surface
  • Always place the film away from the teeth and towards the middle of the oral cavity
  • The film must be positioned to cover the prescribed area of the teeth to be examined

Long Cone Technique  Patient Position:

  • Explain the procedure to the patient
  • Position the patient comfortably of the chair
  • Adjust the patient’s head such that the occlusal place of upper arch is parallel to the floor
  • Mid sagittal plane is perpendicular to the floor
  • Secure lead apron and thyroid collar
  • Remove all objects from the mouth that may interfere with the film exposure

Long Cone Technique  Basic Rules:

  • Film placement film must cover the prescribed area of the teeth to be examined
  • Film position the film must be placed parallel to the long axis of the tooth
  • The holder is rotated so that the teeth to be examined are touching the block
  • The correct focal spot to film distance is determined
    • Vertical angulation the central ray of the X-ray beam is directed perpendicular to the film and the long axis of the tooth
    • Horizontal angulation the central ray of the X-ray beam is directed through the contact areas of the film are exposed
    • Film exposure the X-ray beam must be centered on the film to ensure that all areas of the film are exposed
  • Exposure is made

Oral Radiology Intraoral Radiographic Techniques Positions of the film tooth and the central ray of the x ray beam

Oral Radiology Intraoral Radiographic Techniques The film is placed closed to the tooth and is not parallel to the long axis of the tooth

Read And Learn More: Oral Radiology Question and Answers

Oral Radiology Intraoral Radiographic Techniques Increased object film distance the film is placed

Oral Radiology Intraoral Radiographic Techniques In this diagram the x rays pass through the contact areas

Long Cone Technique  Advantages:

  • This technique produces an image that has dimensional accuracy
  • It is simple and easy to learn and use
  • It is easy to standardize and can be accurately duplicated or repeated
  • Facial screens can be used
  • There is decreased secondary radiation
  • The shadow of the Zygomatic bone appears above the apices of the molar teeth
  • The periodontal levels are well represented
  • There is minimal foreshortening or elongation
  • Good detection of interproximal caries
  • Useful in handicapped and compromised patient as the relative position of the film packet, teeth and X-ray beam are always maintained

Long Cone Technique  Disadvantages:

  • The film holding device is difficult to place in children and in patient with shallow palate
  • The film holding device causes discomfort to the patient
  • Object film distance is increased
  • There is increase in the exposure time
  • It is more space consuming
  • Sometimes the apices of the teeth are very close to the edge of the film and so not well appreciated
  • The holders need to be autoclaved

Question 2. Principles of projection geometry.
Answer.

Principles of projection geometry

  • The basic principles of projection geometry are as follows:
    • The focal spot should be as small as possible
    • The focal spot object distance should be as long as possible
    • The object film distance should be as small as possible
    • The long axis of the object and the film planes should be paralleling
    • The X-ray beam should strike the object and the film planes at tight angles
    • There should be no movement of the tube, film or patient during exposure

Oral Radiology Intraoral Radiographic Techniques The smaller the focal spot area

Oral Radiology Intraoral Radiographic Techniques A longer PID and target film

Oral Radiology Intraoral Radiographic Techniques To limit distortion the central ray

Oral Radiology Intraoral Radiographic Techniques Illustrating the influence of motion

Question 3. Bitewing radiograph
Answer.

Bitewing radiograph

  • It is also called Short Cone Technique
  • It is based on the principle known as “ciesenzky’s rule of isometry”
  • It states that the two triangles at equal if they have two equal angles and share a common side
  • The X-ray beam should bisect the imaginary bisector that bisects the angle formed by the film and the long axis of the tooth
  • When the rule is strictly followed, the resultant image obtained is accurate

Oral Radiology Intraoral Radiographic Techniques Angle A is bisected by line AC

Oral Radiology Intraoral Radiographic Techniques The image on the film is equal to the length of the tooth

Bitewing Radiograph Guidelines:

  • White side of the film always faces the teeth
  • Anterior films always placed vertically
  • Posteriors films always placed horizontally
  • The incisal or occlusal edge of the film must extend approximately 1/8th inch beyond the incisal or occlusal surface of the tooth
  • Always center the film over the area to be examined
  • If patient’s finger is used for stabilization, instruct the patient to gently push the film against the lingual/palatal surface of the tooth

Bitewing Radiograph Basic Rules:

  • Film placement film must cover the prescribed area of the teeth to be examined
  • Film position the film must be placed parallel to the long axis of the tooth
  • Vertical angulation the central ray of the X-ray beam is directed perpendicular to the film and the long axis of the tooth
  • Horizontal angulation the central ray of the X-ray beam is directed through the contact areas of the film are exposed
  • Film exposure the X-ray beam must be centered on the film to ensure that all areas of the film are exposed

Bitewing Radiograph Advantages:

  • It can be used in patients with shallow palate, bony growth
  • It is quick and comfortable
  • Decreased exposure time required
  • Short PID is used
  • If angulations are correct, image obtained is of the same size
  • No sterilization of holders required as they are not used

Bitewing Radiograph Disadvantages:

  • Image distortion may occur due to use of short PID
  • By using film holder it becomes difficult to visualize the imaginary bisector
  • Incorrect horizontal angulation results in overlapping
  • Incorrect vertical angulation leads to elongation or foreshortening
  • If patient’s finger is used for stabilization, patient may shift the film before or during exposure
  • The patient’s hand is exposed unnecessarily
  • The periodontal tissues are poorly represented
  • Overlapping of shadows of Zygomatic bone occurs
  • The Buccal roots of premolars and molars are foreshortened
  • The crowns of the teeth are often distorted

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