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
How can the film be supported? (periapical projection)
- The patient holds the film with the opposite hand to the X-ray beam
- With receptor holding instruments
How should the patient hold the film for maxillary images?
With the thumb
How should the patient hold the film for mandibular images?
With the index finger
How should the angulation of the tube head be in the bisecting angle technique?
Perpendicular to the imaginary bisector formed between the tooth and the film axes
Advantages of periapical projection
- Non-complex technique
- Low cost
- Sharpness
Disadvantages of periapical projection
- Limited area
- Bidimensional image
- Overlapping
- Ineffective in edentulism
Why is the periapical technique ineffective in edentulous patients?
Because they cannot hold the film
What can we see in the bitewing projection?
- Inter-proximal area
- Crowns and the alveolar crest
- The inter-proximal caries
Indications of the bitewing technique:
- Occlusal and inter-proximal caries detection
- Recurrent caries
- Pulpal problems
- Overflowing restorations
- Fixed prosthesis adjustment
- Enamel cementum junction (CEJ)
- Alveolar crest
- Inter-proximal calculus deposit
How is the patient’s head positioned in the bitewing projection?
Occlusal plane parallel to the floor
How is the receptor placed in the bitewing technique?
- Do not bend it
- Comfortable position lingual to the teeth to be examined
- Bitewing between the occlusal surfaces
- The posterior edge distal to the 2nd molar
How are the vertical and horizontal angulations in the bisecting technique?
Vertical angulation: 5-10 degrees (palatal anatomy)
Horizontal angulation: perpendicular to the dental arch
What intraoral technique has the largest receptor?
The occlusal projection technique: film or storage phosphor plates (7.7cm x 5.8cm)
Where is the film supported in the occlusal projection?
Between the dental arches
What intraoral projection is useful to avoid using more culex imaging techniques?
The occlusal projection
Occlusal projection indications
- Dental trauma in the anterior teeth
- Mandible fracture
- Foreign bodies
- Impacted teeth
- Cortical bone enlargement
- Calculus on the Warthon’s duct
- Assessment of the buccal or lingual position of the impacted teeth
How should the X-ray beam be in the orthogonal projection?
Perpendicular to the film
What are the 3 types of anatomy?
- Descriptive
- Topographical/surgical
- Radio-graphical anatomy
In what cases can we not do intraoral radiography?
- Endutulous patients
- Pregnant patient
- Patients with gag reflex
- Patients with mental and physical disabilities
- Patients with infection and trauma (ex: trismus)
