Intraoral Radiographic Techniques Question and Answers

Intraoral Radiographic Techniques

Question  Write short note on long-cone technique in Intraoral Radiographic

Answer. Long-cone technique is also known as Paralleling or right angle technique.

Intraoral Radiographic Long-Cone Technique

• The X-ray film is supported parallel to the long axis of the teeth and the central ray of the X-ray beam is directed at right angles to the teeth and film.
• To achieve parallelism between the film and the tooth, the film must be placed away from the tooth, towards the middle of the oral cavity.
• Because the film is placed away from the tooth, image magnification and loss of definition results. To compensate for image magnification, the target film distance must also be increased to ensure that only the most parallel ray will be directed at the tooth and the film. So this technique is also called as long cone technique.
• In this technique a long cone of 12 inches is used and kVp used is 85 to 90 kVp.
• Here X-rays are directed perpendicular to the film so there is less geometric distortion, less magnification and more definition.

Read And Learn More: Oral Radiology Question And Answers

Intraoral Radiographic Long-Cone Advantages

• Accuracy:
  • Image is dimensionally accurate.
  • Radiographic image is free of distortion and exhibit maximum detail and definition.
  • There is no overlap of related structures.
• Simplicity: The technique is simple and easy to learn and use.
• Duplication: This technique is easy to standardize and can be accurately duplicated or repeated.
• Facial screen can be used.
• There is decreased secondary radiation.
• The relative position of the film, teeth and X-ray beam are always maintained so useful for handicapped and compromised patient.
• The periodontal bone level is well represented.
• The periapical tissues are accurately shown with minimum foreshortening or elongation.

Intraoral Radiographic Long-Cone Disadvantages

• Film placement with film-holding device is difficult in child patient.
• Patient discomfort: The holding device may impinge oral soft tissues and causes discomfort and gagging.
• Object film distance is increased so more chances of image magnification.
• The long cone is more spacious.
• Positioning of film is difficult in third molar region.

Question.  Write Short Note On Difference Between Long-Cone And Short-Cone Technique.
or
compare and contrast bisecting angle technique and paralleling technique
Answer. Comparison between short-cone and long-cone techniques.

For advantages and disadvantages refer to Ans 1 of same chapter.

 

Question. Describe The Technique Of Taking Bitewing Radiography Of Posterior Teeth.

Answer. The bitewing radiography is an intraoral radiographic technique.

Bitewing Radiography of Posterior Teeth Principles

• The film is placed in the mouth parallel to the crown of both the upper and lower teeth.
• The film is stabilized when patient bites on the bitewing tab or bitewing film holder.
• Central ray of the X-ray beam is directed through the contact area of teeth, using a + 10° vertical angulations.

 

Film holder and Bitewing tab

A film holder is used to stabilize the film. Those used for bite wing radiography are:

• Rinn XCP bite wing instruments: Which have a plastic bite blocks, plastic aiming rings and metal indicator arms. A snap ring collimator may be added to reduce the exposure to the patient. These holders are reusable.
• Bitewing tab: It is an alternative to a film-holding device. A film can be fitted with a bite tab or bite loop. This is a heavy paper board tab or loop with adhesive which may be attached to the white side (tube side) of the periapical film. Readymade bitewing films with attached tabs are also available.

Position of Patient

• Briefly explain the procedure to patient.
• Ask the patient is seated upright and the chair adjusted to a comfortable working position.
• Adjust the head rest to support and position the patient’s head so that the upper arch is parallel to the floor and the mid sagittal (middle) plane is perpendicular to the floor.
• Secure the lead apron and thyroid collar.
• Remove all foreign objects from the face and mouth.

Five Basic Rules to follow in the Bite Wing technique

• Film placement: The film must be placed to cover the prescribed area.
• Film position: The film must be positioned parallel to the crowns of both the upper and lower teeth and stabilized by biting on the film holder or tab.
• Vertical angulation: The central ray must be directed at +10°.
• Horizontal angulation: The central ray must be directed through the contact areas between the teeth.
• Film exposure: The X-ray beam must be centered on the film to ensure that all the areas of the film are exposed and thus partial image or cone cut is avoided.

Question. Write short note on occlusal radiography.
or
Write short note on occlusal radiographic technique.
or
Write short note on occlusal X-ray.
or
Discuss occlusal radiographs in detail.
or
Write short note on indications of occlusal radiography.
or
Write short answer on indications of occlusal radiography.
or
Write short answer on occlusal radiograph.
Answer. It is an intraoral radiographic technique.

• This technique is used to examine large areas of the upper and lower jaw.
• The palate and floor of mouth may also be examined.
• This is a supplementary radiographic technique that is used in conjunction with periapical or bitewing radiography.

Occlusal Radiograph Indications

• In locating, the retained roots of extracted teeth.
• In locating, the supernumerary, unerupted or impacted teeth (especially impacted canine and third molars).
• In locating, the foreign bodies in the maxilla or mandible.
• In locating, the salivary stones in the duct of the submandibular gland.
• In locating and evaluating the extent of lesions (e.g. cysts, tumors, malignancies) in the maxilla or mandible. It is especially indicated to determine the mesial and lateral extent of the lesion and its extent on the palate.
• In evaluating, the boundaries of the maxillary sinus (anterior, mesial and lateral outline).
• In evaluating, fractures of the maxilla and mandible. (location, extent and displacement).
• To aid in the examination of patient’s who cannot open their mouths more than a few millimeters or in adults and children who are unable to tolerate periapical films.
• To examine area of cleft palate.
• To measure changes in the size and shape of the maxilla and mandible.
• As a midline view, when using the parallel method for determining the buccal/palatal position of unerupted canines.

Occlusal Radiograph Classification

• Classification
  • Maxillary
    • Cross sectional
    • Topographic
      • Anterior
      • Posterior or lateral
    • Pediatric
  • Mandibular
    • Cross sectional
    • Topographic
      • Anterior
      • Posterior or lateral
    • Pediatric

Occlusal Radiograph Basic Principles

• Film is positioned with white side facing the arch that is being exposed.
• Film is placed in mouth between occlusal surfaces of maxillary and mandibular teeth.
• Film is stabilized when the patient gently bites on the film surfaces.
• For maxilla: Upper arch is parallel to the floor and midsagittal plane is perpendicular to the floor.
• Formandible: The occlusal plane is perpendicular to the floor.

Occlusal Radiograph Film

• Occlusal films are bigger
• Ultraspeed films
• The films are coated on both sides
• Screen type is used in cassette and non-screened films are used in pocket
• For maxilla: Patient is asked to hold the cassette or packet with both the thumbs

Various occlusal Radiographic Views and their techniques

 

 

Maxillary Pediatric Occlusal Projection

• Here, patient should be positioned upright with maxillary arch parallel to the floor, so that sagittal plane is perpendicular to floor and occlusal plane is horizontal.
• Place a size – 2 film with white part facing the maxilla and long edge over side to side direction.
• Film should be inserted in the child’s mouth, place the film as far as posteriorly the patient’s anatomy permits and till it contact the anterior border of ramus of mandible.
• Child should be asked to bite down gently on film, retaining the position of film in end to end bite.
• Position indicating device (PID) is positioned so that the central ray is directed via the midline of arch towards the centre of film at vertical angulation of +600. Top edge of position indicating device is placed between the eyebrows on bridge of the nose. In general, central ray enters the face of patient via bridge of nose.

Question. Write short note on Bisecting Angle Technique.
Answer.

Principle of angle-Bisecting technique

• Angle bisecting technique is based on the simple geometrical principle known as “Cieszynski’s law of isometry” which states that two triangles are said to be equal when they share one complete side and have two equal angles.
• In dental radiography, the above given law is applied as:
  • Film should be positioned close to the lingual surface of teeth, resting on palate or on the floor of mouth.
  • Plane of the film along with the long axis of tooth form an angle with its apex at a point where film is in the contact with the teeth.
  • When the angle is bisected via the imaginary line two congruent angles with a common side are formed.
  • A line which represent the central ray of an X-ray beam complete the third side of two triangles when it is bisected perpendicular to bisecting line.
  • This involves in taking the radiographs in the manner that the long axis of rays is perpendicular to bisector between the long axis of tooth and the long axis of film.
  • Here an 8 inch cone is used with 55 to 65 kVp.

Bisecting Angle Technique Advantages

• Primary advantage is that it can be used without film holder when the anatomy of patient not allowed use of holder (like in shallow palate bony growth).
• Positioning is reasonably comfortable, simple and quick.
• Decreased exposure time, as a short (8 inch) PID is used.
• Positioning of film packet is comfortable to the patient.
• In the technique, if angulations are assessed properly,there be no changes in the dimension seen of the tooth which is imaged.
• If angulations are discussed properly, there will be no changes in demission of tooth which is in aged.

Bisecting Angle Technique Disadvantages

• Image distortion: Due to short PID, there is increase in the divergence of X-rays which causes image magnification.
• Angulation problem: It is difficult for the dental radiologist to visualize the imaginary bisector and determine vertical angulation without the use of film holder and aiming the ring. So if there is any error in the vertical angulation, this causes image distortion.
• Unnecessary exposure:As patient stabilizes the film by their finger, the patient’s hand is unnecessarily exposed to the primary beam of X-ray radiation.
• Incorrect horizontal angulation: This leads to overlapping of the images, while incorrect vertical angulation leads to foreshortening or elongation of the image.
• Periodontal bone levels are poorly represented.
• Shadow of zygomatic bone frequently overlaps the periapical area of maxillary molars.
• Crown of the teeth are often get distorted so detection of proximal caries is difficult.

Question. Enumerate intraoral radiographic techniques. Discuss principle, advantages, disadvantages of bisecting angle technique.
or
Enumerate various intraoral periapical techniques and discuss bisecting angle technique in detail.
or
Discuss bisecting angle technique of IOPA radiograph in detail.
Answer.

Intraoral Radiographic Techniques

• Bitewing radiography
• Periapical radiography
  • Bisecting angle technique/short cone technique.
  • Paralleling technique/long-cone technique/rightangle technique.
• Occlusal radiography
  • Maxillary occlusal view
  • Mandibular occlusal view
  • Maxillary and mandibular occlusal views are subdivided into:
    • Cross-sectional occlusal view
    • Topographic occlusal view—anterior/posterior
    • Pediatric occlusal view

Intraoral Localization Radiographic techniques

• Stereoscopy
• Buccal object rule
• Contrast radiography
• Tube shift technique/Clark’s rule
• Right angle technique/Miller’s technique

For principle, advantages, disadvantages of bisecting angle technique refer to Ans 6 of same chapter.

Question. Write short note on ‘y’ line of Ennis.
Answer. It is also known as Line of Ennis or Inverted Y of Ennis.

• Intersection of maxillary sinus and the nasal cavity seen on the radiographs is called as ‘Y’ line of Ennis.
• It was reported by a researcher in oral radiology named Dr Ennis.
• In periapical region of maxillary canine, IOPA the lateral wall of nasal fossa and anterior border of maxillary sinus forms an inverted Y which is termed as “ Inverted Y of Ennis”.
• On radiograph, it appears as a radiopaque upside down ‘Y’ formed by the lateral wall of the nasal fossa and the anterior border of maxillary sinus.
• Inverted Y is located above the maxillary canine.

Question 9. Write short note on Clarke’s technique of object localization.
or
Write short note on clarke’s technique.
Answer. Clark’s technique is an intraoral localization technique.

It is also known as buccal object rule or tube shift technique or Clarke’s rule.

Clarke’s Technique Principle

• Relative position of radiographic images of two separate objects changes when the projection angle at which the projection was made is changed.
• A different horizontal angle is used when trying to locate vertically aligned images, e.g. root canals.
• Adifferent vertical angulation is used when trying to locate a horizontally aligned image, e.g. mandibular canal.

Clarke’s Technique Method

• Two radiographs of the object are taken.
• First radiograph is taken using the proper technique and angulations as prescribed.
• Second radiograph is taken keeping all parameters constant and equivalent to those of a first radiograph. Only the direction of central ray is changed whether with a different horizontal or vertical angulation is used.

Clarke’s Technique Interpretation

• When the dental structure or object is seen in the second radiograph, it appears to have moved in the same direction as the shift of the position-indicating device (PID), the structure or the object in question is said to be positioned lingually.
• But if object appears to move in direction opposite to the shift of PID, then object in question is said to be positioned buccally.
• It follows SLOB rule, i.e. Same side lingual and opposite side buccal.

Question 10. name various techniques of localization. how will you localize an impacted maxillary canine in right maxillary region?
Answer. Following are the techniques of localization

• Stereoscopy
• Buccal object rule
• Contrast radiography
• Tube shift technique/Clark’s rule
• Right angle technique/Miller’s technique

Localization of Maxillary Impacted Canine

Radiographic techniques for localizing maxillary impacted canine are:

1. Stereoscopy

2. Occlusal

3. Lateral profile

• Stereoscopy
  • Localization of maxillary impacted canine is done by stereoscopy
  • Stereoscopic imaging requires the exposure of two films, one for each eye and thus delivers twice the amount of radiation to the patient. Between exposures the patient is maintained in position, the film is changed and the tube is shifted from right eye to left eye. Although the magnitude of the tube shift is empiric, it is sufficient to form slightly different images. After processing, films are viewed with a stereoscope that uses either mirror or prism to coordinate the accommodation and convergence of the viewer’s eyes so that the brain can fuse the two images.
• Occlusal radiography

Maxillary Cross-Sectional View

• Image field: This projection shows the palate, the zygomatic process of the maxilla, the anterior-inferior aspects of each antrum, nasolacrimal canals, teeth from the right second molar to the left second molar and the nasal septum.
• Film placement: The film is placed crosswise into the mouth and gently pushed back until it contacts the anterior border of the rami.
• Projection of the central ray: The central ray is directed at a vertical angulation of +65° and a horizontal angulation of +65° towards the middle of the film. In general, the central ray enters the patient’s face through the bridge of the nose.

Maxillary Topographic View—Anterior

• Image field: The primary field of this projection includes the anterior maxilla and its dentition. It also includes the anterior floor of the nasal fossa and the teeth from canine to canine.
• Film placement: The film is placed with the exposure side towards the maxilla and the long dimension crosswise in the mouth.
• Projection of the central ray: The central ray is directed towards the middle of the film, the vertical angulation is l5° and horizontal angulation is 0°.
• In general, the central ray enters the patient’s face approximately through the tip of nose.

Maxillary Topographic View—Labial

• Image field: This projection shows half of the alveolar ridge of the maxilla, inferolateral aspect of the antrum, the tuberosity and the teeth from the lateral incisor to the third molar. It may also show the zygomatic process of the maxilla superimposed with the roots of the molar teeth.
• Film placement: Film is placed with its long axis parallel to the sagittal plane and on the side of interest, with the pebbled side towards the maxilla in question. The lateral border should be positioned parallel to the buccal surfaces of the posterior teeth and extending laterally approximately 1/ 4th inch past the buccal cusps.
• Projection of the central ray: The central ray is projected to a point 2 cm below the lateral canthus of the eye and directed towards the center of the film, with a vertical angulation of +60°.

Question 11. Write short note on technique for maxillary cross sectional occlusal radiograph. 
Answer.

Technique for Maxillary Cross-Sectional Occlusal Radiograph

• Image field: This projection shows the palate, the zygomatic process of the maxilla, the anterior-inferior aspects of each antrum, nasolacrimal canals, teeth from the right second molar to the left second molar and the nasal septum.
• Film placement: The film is placed crosswise into the mouth and gently pushed back until it contacts the anterior border of the rami.
• Projection of the central ray: The central ray is directed at a vertical angulation of +65° and a horizontal angulation of +65° towards the middle of the film. In general, the central ray enters the patient’s face through the Bridge of the nose.

 

Question 12. Write short note on Paralleling Technique for taking 26.
Answer. Following is the paralleling technique for taking 26

• Film placement: Film is positioned to cover the 26.
• Film position: The film packet is placed in the midline of the palate, again to accommodate its height in the vault of palate.
• The holder is rotated so that 26 touches the block. A cotton wool roll is placed on the reverse side of the bite block, to help keep the tooth and the film packet parallel, and the film holder more comfortable for the patient. The patient is requested to gently bite together, to stabilize holder in position.
• The lower locator ring is moved down the indicator rod until it is in contact with the patient’s face. Correct focal spot to film distance is determined as long cone is aligned with the locator ring. This automatically sets the vertical and horizontal angles and centers X-ray beam on film packet.

 

 

• Vertical angulation: Central ray of the X-ray beam must be directed perpendicular to the film and the long axis of 26.
• Horizontal angulation: Central ray of X-ray beam must be directed through the contact areas between the teeth.
• Projection of central ray: It is directed on the cheek below outer canthus of eye and the zygoma at the position of 27, perpendicular to the plane of film.
• The exposure is made.

Question 13. What is intraoral radiography? discuss in detail about bisecting angle technique. Give two differences between paralleling and bisecting angle technique.
Answer. Intraoral radiography is of three types, i.e.

• Periapical: It shows complete tooth as well as surrounding bone.
• Bitewing: It shows crowns of all maxillary and mandibular teeth as well as adjacent alveolar crest.
• Occlusal: It display images of incisal edges of anterior teeth and occlusal surfaces of posterior teeth as well as cross section of dental arches.

For angle bisecting technique refer to Ans 6 of same chapter.

For two differences refer to Ans 3 of same chapter.

Question 14. Write short note on principles of projection geometry.
Answer. Projection geometry is also known as shadow casting.

Following are the principles of projection geometry:

• Principle 1: Focal spot, i.e. source of radiation should be as small as possible.
• Principle 2: Focal spot-object distance should be as long as possible.
• Principle 3: Object-film distance should be as small as possible.
• Principle 4: Long-axis of the object and film planes should be parallel.
• Principle 5: X-ray beam should strike the object and the film planes at right angle.
• Principle 6: There should be no movement of the tube,

 

 

 

 

 

Question 15. Write in detail about intraoral radiographic techniques.
Answer. Following are the intraoral radiographic techniques:

• Periapical radiography
  • Paralleling or right-angle or long-cone technique
  • Bisecting angle or short cone technique
• Bitewing radiography technique
• Occlusal radiography techniques

For paralleling technique and bisecting angle technique in detail refer to Ans 1 of the same chapter.

Bitewing Radiography technique

Following is the bitewing radiography technique:

• Bite platform is positioned over the center of film packet. Bite platform should lie parallel to upper and lower edges of film packet.
• Head of the patient is positioned by adjusting the head rest. Positioning of head is such that the upper arch lies parallel to the floor and mid-sagittal plane lies perpendicular to the floor.
• Secure the lead apron and thyroid collar.
• Film should be placed over the prescribed area.
• Film should be positioned parallel to the crowns of both maxillary and mandibular teeth. Film should be stabilized by biting on the film holder.
• Vertical angulation of the central ray is directed at +10°.
• Horizontal angulation of the central ray is directed through contact areas between the teeth.
• X-ray beam should be centered on the film to ensure that all the areas of film are exposed and partial image or cone cut is avoided.

For Technique of bitewing radiography in detail refer to Ans 4 of same chapter.

Occlusal Radiography Techniques

Following are the basic steps for all occlusal radiography techniques:

• White side of the film should faces towards the arch.
• Placement of film in the mouth is between the occlusal surfaces of mandibular and maxillary teeth.
• Stabilization of the film occurs when patient gently bites on the surface of film.
• For maxillary occlusal films patient’s head is positioned such that upper arch is parallel to the floor and the mid sagittal plane should be perpendicular to the floor.
• For mandibular occlusal films patient’s head should be reclined and is positioned such that the occlusal plane is perpendicular to the floor.

For different views of occlusal radiography techniques in detail refer to table in Ans 5 of same chapter.

Question 16. Write short note on Focal Length.
Answer. Focal length of an X-ray system is a measure of how strongly the system converges or diverges X-rays.

• For an X-ray system in air, it is the distance over which initially collimated rays are brought to a focus.
• An X-ray system with a shorter focal length has greater optical power than one with a long focal length; i.e., it bends the X-rays more strongly, bringing them to a focus in a shorter distance.

Question 17. Write short note on maxillary Topographic Occlusal Radiograph.
Answer. Maxillary topographic occlusal radiograph is used to examine the palate and anterior teeth of the maxilla.

Maxillary topographic occlusal view is divided into two types i.e. anterior and posterior or lateral.

Maxillary Topographic View—Anterior

• Here, patient should be positioned upright with maxillary arch parallel to the floor, so that sagittal plane is perpendicular to floor and occlusal plane is horizontal.
• Place a size – 4 film with white part facing the maxilla and long edge over side to side direction.
• Film should be inserted in the patient’s mouth, place the film as far as posteriorly the patient’s anatomy permits and till it contact the anterior border of ramus of mandible.
• Patient should be asked to bite down gently on film, retaining the position of film in end to end bite.
• Position indicating device (PID) is positioned so that the central ray is directed via the midline of arch towards the centre of film at vertical angulation of +65° and horizontal angle of 0° towards midline of the film. Top edge of position indicating device is placed between the eyebrows on bridge of the nose. In general, central ray enters the face of patient via bridge of nose.

Maxillary Topographic View—Posterior or Lateral

• Here, patient should be positioned upright with maxillary arch parallel to the floor, so that sagittal plane is perpendicular to floor and occlusal plane is horizontal.
• Place a size—4 film with white part facing the maxilla and long edge over front to back direction.
• Film should be inserted in the patient’s mouth, place the film as far as posteriorly the patient’s anatomy permits and till it contact the anterior border of ramus of mandible.
• Shift the film to the side of interest i.e. either right or left. Long edge of the film should extend approximately ¼ inch beyond the buccal surfaces of posterior teeth.
• Patient should be asked to bite down gently on film, retaining the position of film in end to end bite.
• Position indicating device is positioned in manner so that the central ray is directed at +60° towards centre of the film. Top edge of position indicating device should be placed above the corner of eyebrow.

Question 18. describe the production of X-ray. discuss in detail the principle and method of paralleling technique of intraoral periapical radiology.
Answer. For production of X-ray refer to Ans 2 of chapter PRODUCTION OF X-RAY.

Principle of Paralleling technique of intraoral Periapical Radiology

Central principle of paralleling technique is that the X-ray receptor is supported parallel to the long axis of teeth and central ray of the X-ray beam is directed at right angles to the teeth and receptor. This orientation of the receptor, teeth and central ray minimizes geometric distortion and presents the teeth and supporting bone in their true anatomic relationship.