Intra-Oral Radiography Flashcards
What is a conventional radiograph?
2D picture made up of a variety of black, white and grey superimposed shadows
Which structures does a standard BW capture?
What is radiopaque?
The white or radiopaque shadows on a film represent the various dense structures within the object which have totally stopped the X-ray beam
What is radiolucent?
The black or radiolucent shadows represent areas where the X-ray beam has passed through the object and has not been stopped at all
What are the different film sizes and what are they used for?
Size 0
- Used in children for both PA and BW
Size 1
- Used for adult anterior PA (using paralleling technique)
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
Size 3
- Extra-long BW (not commonly used)
Size 4
- Used for occlusographs in adults
Where should the receptor be placed?
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.
What causes horizontal overlapping of the crowns on an xray?
Horizontal overlapping of crowns is the result of misdirection of the central ray.
What is the point of entry?
The central ray should enter the cheek below the lateral canthus of the eye at the level of the occlusal plane.
How do you place the film if there is a prominent mandibular tori?
Use the thinnest film eg. Analogue film or digital PSP plate (photostimulable phosphor plate) and place it lingual to the torus
How do you place the film if there are missing teeth?
Place cotton rolls in the edentulous (missing teeth) space to prevent film rotation.
What are the indications for a BW radiograph?
- Caries
- Status of restorations
- Crestal bone height
- Periodontal bone loss
What are the indications for a periapical radiograph?
- Periapical inflammation / pathology
- Root resorption
- Root fractures
- Endodontic therapy (pre, peri & post)
- Localisation of impacted, missing, supernumerary teeth and foreign bodies
- Implant status
What is the ideal PA coverage?
- Cover 2-3 mm beyond the crowns
- Demonstrate all roots
- Demonstrate the apical tissues
Ideal Tooth/Film relationship not possible to achieve because of anatomic limitations
Techniques used in periapical imaging are therefore a compromise from this ideal
Explain the paralleling technique
Point of Entry: The point of entry of the central ray should be on the cheek below the outer canthus of the eye and the zygoma at the position of the maxillary second molar.
The longer the cone, the more parallel the beam
- 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
What are the advantages of the paralleling tehnique?
- 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
What is the bisecting angle technique?
In any 90-degree arc, there is one angle (bisecting angle) that will allow an xray beam to cast an accurate shadow of the tooth on the film
What causes foreshortening?
Vertical overangulation
What causes elongation?
Vertical Underangulation
What can you see on a Maxillary Anterior Occlusal?
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
Which technique is this?
Mandibular Anterior Occlusal
Which technique is this?
Mandibular True Occlusal
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
What is the Tube Shift Technique?
(also called Parallex Technique / Clark’s Rule)
= Two PA images taken
Film #1 = centred over area of interest and taken - normal standard PA
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)
Which direction will a horizontal shift move in?
Mesial and Distal
Which direction will a vertical shift move in?
Lingual - Buccal
Which technique was used to locate the ‘radiopacity’?
And where is the radiopacity (arrow point)?
Object has been been moved to the right and up – cone has been moved up = vertical tube shift
Radiopacity is placed bucally
What is the right angle technique (Miller’s Technique)?
- Two radiographs are taken
- The second is taken at right angles to the first
- Eg. periapical + true occlusal film
- The occlusal film will determine the bucco-lingual position of the object (Not commonly practiced)
Identify this error
Took an xray and they left another film over the already exposed film for too long + by the time they developed it there was a different contrast
Part of it was exposed to white light
Identify this error
Elongation – happens when the angle of the PA was too acute – misses the periapical region of the tooth
Identify this error
Double exposure – molar from a previous xray
Identify this error
Damaged film
Identify this error
Exposed twice – can see 2 sets of teeth
