Chapter 5: Intraoral radiographic imaging Flashcards
Radiographic imaging consists of
- Ionising radiation
- Electromagnetic radiation: X-ray
- X-ray machine: tube, cathode, anode
- Factors controlling the radiographic imaging: ET, mA, kVp, distance tube-film. collimation, filtration
- Projection geometry
- X-ray machines in dentistry
- Safety and protections
What are the 3 categories of intraoral radiographic imaging?
- Periapical projection: all of the tooth and surrounding bone
- Bitewing projection: crowns of teeth and adjacent alveolar crest
- Occlusal projection: area of the teeth and bone are seen larger than in periapical
What are the criteria of quality?
- Record the complete areas of interest
- Reduce the amount of distortion
- Optimal density and contrast
General steps of periapical projection
- Prepare the unit: barriers for infection control
- Seat the patient: in an upright position, remove glasses and removable appliances, drape the patient lead apron
- Adjust the X-ray unit settings: kVp, mA, ET
- Examine the oral cavity: estimate axial inclination (of the palate), tori, obstruction
- Position: the tube head
- Position the receptor: holding the device (film holder or patient holding it themselves)
- Position of the X-ray tube: Align the aiming cylinder
- Make the exposure
What do we expect to get from the periapical X-ray?
- Teeth
- Periodontal areas
- Surrounding bone
- Bone
The primary goal of the periapical projection is to obtain as much field as possible. True or False
True
Why do we use the periapical X-ray for?
- Assessment of the teeth and bone alterations
- Study and location of bone areas
- Implant assessment
What do we do to avoid overlapping?
We change the angulation
Should we try to direct the X-ray parallel or perpendicular to the film?
Perpendicular
What are the 2 common techniques of the periapical X-ray?
- Paralleling technique (other names: Mc-Cormack, right-angle, long-cone)
- Bisecting angle technique (other names: Dieck, Cieszynski, short-cone)
How does the paralleling technique work?
- The film is parallel to the long axis of the tooth and the X-ray beam is perpendicular to both of them
- The X-ray receptor is supported parallel to the long axis of the tooth and the central ray of the X-ray beam is directed at right angles to the teeth and receptor
Receptor holding instruments
Various brands: digital or film
External guiding rings: align the X-ray aiming cylinder
Paralleling technique procedure
- Patient’s head: relaxed and leaning against the chair
- Film: parallel to the long axis of the teeth (holding instruments)
Principle of the paralleling technique
Long distance X-ray source-object in order to minimise the image magnification
Advantages of the paralleling technique
- Less distortion
- Higher resolution
- Higher accuracy
Principle of the bisecting angle technique
2 triangles are equal when they share one complete side and have 2 equal angles (Cieszynski’s rule of isometry)
What periapical technique requires a lot of anatomy knowledge?
Bisecting angle technique
What is more common the bisecting angle or the paralleling technique?
Bisecting angle technique
How does the bisecting angle technique work?
- The receptor is positioned on the lingual surface of the teeth resting in the palate or the floor of the mouth
- The plane of the receptor and the long axis of the teeth form an angle
- The X-ray beam is projected at a right angle to the bisecting line
- An object and its image are the same length when the X-ray beam is perpendicular to the bisecting angle that forms between the film and the tooth axis
What periapical technique is more simple?
The bisecting angle technique
Does the angle in the bisecting technique depend on the patient?
Yes
What periapical technique has a lower deformation?
The paralleling technique
Position of the patient’s head in the bisecting technique
- Comfortable, stable and leaning against the chair
- For maxillary images: titles back slightly to compensate for the change of the occlusal plane when the mouth opens
- For mandibular images: titled back slightly to compensate for the change of the occlusal plane when the mouth is open
How is the receptor placed in the bisecting technique?
- Behind the area of interest
- The apical end against the mucosa on the lingual or palatal surface
- Do not bend the film excessively (to avoid distortion)
- Do not exceed the crown limits
