Podcast
Questions and Answers
What is the primary purpose of using extraoral radiographs?
What is the primary purpose of using extraoral radiographs?
Which extraoral radiographic projection is NOT associated with the frontal or coronal plane?
Which extraoral radiographic projection is NOT associated with the frontal or coronal plane?
What is a key indication for utilizing the posteroanterior (PA) cephalometric projection?
What is a key indication for utilizing the posteroanterior (PA) cephalometric projection?
In extraoral radiography, where is the X-ray source typically positioned?
In extraoral radiography, where is the X-ray source typically positioned?
Signup and view all the answers
Which imaging equipment is specifically used for conventional extraoral projections?
Which imaging equipment is specifically used for conventional extraoral projections?
Signup and view all the answers
What is a critical positioning step for obtaining a successful posteroanterior (PA) cephalometric projection?
What is a critical positioning step for obtaining a successful posteroanterior (PA) cephalometric projection?
Signup and view all the answers
Which condition is commonly evaluated through a lateral cephalometric projection?
Which condition is commonly evaluated through a lateral cephalometric projection?
Signup and view all the answers
What is the primary advantage of using a radiographic grid in extraoral radiography?
What is the primary advantage of using a radiographic grid in extraoral radiography?
Signup and view all the answers
What is a key indication for performing a submentovertex projection?
What is a key indication for performing a submentovertex projection?
Signup and view all the answers
Which positioning technique is essential for a waters projection?
Which positioning technique is essential for a waters projection?
Signup and view all the answers
Which of the following conditions is contraindicated when performing certain imaging techniques?
Which of the following conditions is contraindicated when performing certain imaging techniques?
Signup and view all the answers
What central ray direction is utilized during the submentovertex projection?
What central ray direction is utilized during the submentovertex projection?
Signup and view all the answers
Which projection is specifically used to assess the thickness of the posterior mandible?
Which projection is specifically used to assess the thickness of the posterior mandible?
Signup and view all the answers
Which middle third facial fracture is NOT typically assessed using a waters projection?
Which middle third facial fracture is NOT typically assessed using a waters projection?
Signup and view all the answers
What X-ray tubehead angle is recommended for investigating the skull base?
What X-ray tubehead angle is recommended for investigating the skull base?
Signup and view all the answers
Which of the following is a purpose of investigating the frontal, sphenoidal, and maxillary sinuses?
Which of the following is a purpose of investigating the frontal, sphenoidal, and maxillary sinuses?
Signup and view all the answers
What is the purpose of positioning the patient with the head tipped back in the reverse Towne projection?
What is the purpose of positioning the patient with the head tipped back in the reverse Towne projection?
Signup and view all the answers
Which angle is used to position the X-ray tube head in the reverse Towne projection?
Which angle is used to position the X-ray tube head in the reverse Towne projection?
Signup and view all the answers
In the oblique laterals projection, what is one key indication for its use?
In the oblique laterals projection, what is one key indication for its use?
Signup and view all the answers
What technique is typically used for imaging the central and medial surfaces of the condyle?
What technique is typically used for imaging the central and medial surfaces of the condyle?
Signup and view all the answers
Why might the oblique laterals projection be preferred over intraoral views?
Why might the oblique laterals projection be preferred over intraoral views?
Signup and view all the answers
What is the central ray angle when performing the reverse Towne projection?
What is the central ray angle when performing the reverse Towne projection?
Signup and view all the answers
Which projection provides a gross view of the condyle and is also referred to by multiple names including the MacQueen projection?
Which projection provides a gross view of the condyle and is also referred to by multiple names including the MacQueen projection?
Signup and view all the answers
What type of fractures is the reverse Towne projection specifically indicated for?
What type of fractures is the reverse Towne projection specifically indicated for?
Signup and view all the answers
Study Notes
Extraoral Radiography
- Techniques used to visualize the cranium, face (including maxilla and mandible), cervical spine, and areas not fully covered by intraoral radiographs.
- Includes lateral cephalometric, submentovertex (SMV), Waters, posteroanterior (PA) cephalometric, and reverse-Towne projections.
- X-ray source and receptor are outside the oral cavity.
Uses
- Evaluate larger areas of the maxillofacial/craniofacial region.
- Evaluate growth and development.
- Evaluate impacted teeth.
- Evaluate traumatic injuries to the skull.
- Evaluate TMJ.
- Assess airway and paranasal sinuses.
- Pre and post-treatment evaluation.
Equipment
- Skull X-ray unit: Conventional extraoral projections.
- Panoramic X-ray machine with cephalostat.
- Conventional film or digital sensors.
- Extraoral films come in various sizes: 5x7, 8x10.
- Radiographic grid: Reduces scattered radiation, improves contrast and resolution, but results in higher patient exposure. Made of thin lead strips embedded in plastic material. Placed between the patient's head and film. Cephalometry does not require grids.
PA Skull (Posterio-anterior Cephalometric Projection)
-
Indications:
- Investigating frontal sinuses.
- Evaluating facial asymmetry.
- Conditions affecting the cranium:
- Paget's disease of bone.
- Multiple myeloma.
- Hyperparathyroidism.
- Intracranial calcification.
-
Technique and positioning:
- Patient faces image receptor with the forehead and tip of the nose touching the image receptor (forehead-nose position).
- X-ray tubehead is positioned with the central ray horizontal (0°) centered through the occiput.
Lateral Skull (Lateral Cephalogram Projection)
-
Indications:
- Orthodontics: Initial diagnosis and evaluation of skeletal and soft tissue abnormalities. Treatment planning.
- Fractures of the cranium and cranial base.
- Middle third facial fractures.
- Investigation of frontal, sphenoidal, and maxillary sinuses.
- Tumor of the pituitary gland.
- Conditions affecting the skull vault:
- Paget's disease of bone.
- Multiple myeloma.
- Hyperparathyroidism.
-
Technique and positioning:
- Patient positioned with the head turned 90° so the side of the face touches the image receptor. Sagittal plane of the head parallel to the image receptor.
- X-ray tubehead positioned with the central ray horizontal (0°) and perpendicular to the sagittal plane and image receptor, centered through the external auditory meatus.
Submentovertex Projection
-
Indications:
- Investigation of the sphenoidal sinus.
- Assessment of the thickness (mediolateral) of the posterior part of the mandible before osteotomy.
- Fracture of the zygomatic arches (taken with reduced exposure factors).
- Investigating the skull base.
-
Technique and positioning:
- Patient faces away from the image receptor. Head tipped backwards as far as possible, vertex of the skull touching the image receptor.
- X-ray tubehead aimed upwards from below the chin, with the central ray at 5° to the horizontal, centered on an imaginary line joining the lower first molars.
-
Contraindicated in patients with suspected neck injuries.
Waters Projection
-
Indications:
- Detecting middle third facial fractures:
- Le Fort I, Le Fort II, Le Fort III.
- Zygomatic complex.
- Naso-ethmoidal complex.
- Orbital blow-out.
- Coronoid process fractures.
- Investigating sinuses: Maxillary, frontal, and ethmoidal sinuses.
- Investigating the sphenoidal sinus (taken with the patient's mouth open).
- Detecting middle third facial fractures:
-
Technique and positioning:
- Patient faces the image receptor with the head tipped back, radiographic baseline at 45° to the image receptor (nose-chin position). This positions drops the dense bones of the base of the skull downwards and raises the facial bones.
- X-ray tube head positioned with the central ray horizontal (0°) centered through the occiput.
Reverse Towne Projection
-
Indications:
- High fractures of the condylar necks.
- Intracapsular fractures of the temporomandibular joint.
- Investigation of the quality of the articular surfaces of the condylar heads in temporomandibular joint disorders.
- Condylar hypoplasia or hyperplasia.
-
Technique and positioning:
- Patient in PA position (head tipped forwards in the forehead-nose position) with the mouth open.
- X-ray tube head aimed upwards from below the occiput, with the central ray at 30° to the horizontal, centered through the condyle.
Oblique Laterals
- Indications:
- Assessment of the presence and/or position of unerupted teeth.
- Detection of fractures of the mandible.
- Evaluation of lesions affecting the jaws (cysts, tumors, giant cell lesions, other bone lesions).
- Alternative when intraoral views are unobtainable (gagging, inability to open mouth, general anesthesia).
- Specific views of the salivary glands or temporomandibular joints.
Other Extra Oral Projections for TMJ
- Transcranial Projection (Lindblom Technique): Useful for central and medial surfaces of the condyle.
- Transpharyngeal Projection (Parma/MacQueen - Dell/infracranial projection): Gross view of the condyle.
- Trans-orbital Projection (Zimmer/transmaxillary projection):
Maxillofacial Region of Interest and Corresponding Extra Oral Projections
- The text includes a table showing the maxillofacial region of interest, relevant structures, and corresponding extraoral projections.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers various techniques used in extraoral radiography, which includes methods for visualizing the cranium, face, and cervical spine. It highlights the specific projections utilized in the evaluation of maxillofacial regions, growth, injuries, and the TMJ. Understand the equipment required for different projections and their applications in clinical settings.
