Zygomatic Arches, Mandible, TMJs Flashcards
Why must we use a short SID for the SMV of the zygomatic arch?
To allow divergence of the beam to superimpose the narrower mandible with the wider skull
How far back does the Zygomatic arch go?
Zygomatic arch goes to about the EAM
What makes up the zygomatic arch?
Temporal process of the zygoma, and the zygomatic process of the temporal bone
What effect would tilting the bucky have on the SMV projection of the zygomatic arches?
It would elongate the image
What projection is being shown of the zygoma?
The SMV
What should be seen in an SMV for the zygomatic arches?
- Zygomatic arches free from overlying structures
- Symmetric and without foreshortening
- No rotation or tilt of head
Which way is the mandible tilted?
Mandible tilted to the right
How much does the mandible need to be tilted and rotated for an oblique axial tangential position?
15 degrees
Test answer
What projection is this and what is it demonstrating?
Oblique axial tangential position demonstrating the left zygomatic arch
What positioning techniques would correct this image?
-Mandible tilted more towards the left
-Neck more extended
Which way should the nose be positioned to correct this image?
Nose rotated to the right
What should be seen on an AP axial modified towne method for the zygomatic arches?
- Symmetric projection of both zygomatic arches
- No overlap by mandible
- Zygomatic Arches are projected lateral to mandibular rami
What projection is being shown here?
AP axial modified towne method for the zygomatic arches
What is circled in green?
Lateral superior border of the orbits
Is a single mandibular fracture possible?
Yes
Where is the mandible ussually fractured?
- Body
- Ramus
T/F
Fractures through body or ramus are readily apparent
True
T/F
Fractures through condyle of the mandible may be difficult to see
True
What is the best way to find mandibular condyle fractures?
By doing an axiolateral TMJ projection
What is Contrecoup fracture?
A fracture of the ramus and the body of the mandible
Where is the mandible ussually wired to when there is a mandibular fracture?
The mandible is wired to the maxilla typically when there are fractures of the mandible.
How far does the condyle of the mandible go up?
Superior to the EAM
What side is demonstrated in a lateral mandible projection?
The side closest to the IR
What should be seen on a lateral mandibular projection?
- Collimate to include TMJ, symphysis menti, and anterior occlusals
- Extended neck to get the ramus off the spine
What projection is being shown here?
Lateral mandible projection
Why do we perform an axiolateral oblique of the mandible?
So that we can project one side above the other to demonstrate the body, the ramus, the symphysis or general survey
How do you best demonstrate the ramus on an axiolateral oblique?
Keep head in a true lateral
How do you best demonstrate the body of the mandible on an axiolateral oblique?
Rotate head 30° toward IR or until the body of the mandible is parallel to the IR
How do you best demonstrate the symphysis of the mandible on an axiolateral oblique?
Rotate head 45° toward IR
How do you best demonstrate the general survey on an axiolateral of the mandible?
Rotate head 15°-20° toward IR
What area of the mandible is the general survey demonstrating?
Halfway between the ramus and the body
How do you position for the axiolateral oblique for the ramus of the mandible when erect?
Tilt vertex 15° towards IR and angle CR 10° cephalad if we cannot angle 25 degrees cephalad
Why is a 25 degree tilt of the head for the axiolateral ramus while erect not reccomended?
When tilt is used, the ramus becomes foreshortened.
What projection of the mandible is this?
General survey
What part of the mandible is this projection for?
For the ramus
What could be done to demonstrate the ramus better?
-Needed more tilt or more of a cephalad angle (remote side is covering the dependant side)
What part of the mandible is being demonstrated here?
The body
What part of the mandible is being demonstrated here?
The symphisis
What part of the mandible is being demonstrated here?
A general survey
What projection of the mandible is this?
PA mandibular rami
What should be demonstrated on a PA Axial of the mandible?
- Demonstrates body and ramus
- Condyles demonstrated
What is the best position to demonstrate medial or lateral displacement of fractures of the mandible?
PA axial mandible
What projection is this?
PA axial mandible
What should be seen on an AP axial modified towne method for the mandible?
- Include TMJ and symphysis menti
- Good visualization of the condyles
What would an increased angle cause for an AP axial modified townes?
Increased elongation
What is the best projection to assess medial or lateral displacement of the mandible?
The AP Axial – Modified Towne or PA axial mandible
What additional views are used for demonstration of the mandible?
SMV – Basal view
Panorex – panoramic tomography
What are the two methods of obtaining images of the mandible through panoramic tomography?
- – tube and IR rotate (in the same direction) around stationary patient
- – patient and IR rotate (in opposite directions) around a stationary x-ray tube
How long is the rotation time for a panoramic tomogram of the mandible?
10 to 20 seconds
T/F
Panoramic tomography is digital
True
What is being shown here?
A panoramic tomogram
Read through what a panoramic tomogram demonstrates:
- Curved structures
- Mandible, TMJs
- Nasal fossae, maxillary sinuses
- Upper and lower dental arches
- Fractures or infectious processes
What is being shown here?
A panoramic tomogram
How does the occlusal plane descend in a panoramic tomogram?
Occlusal plane declines 10° from posterior to anterior
How should you position a patient for a panoramic tomogram?
- Chin rests on chin rest, and bite down on bite block
- Position patient straight – do not allow head and neck to stretch forward
What line should be paralell to the floor for a panoramic tomogram?
IOML is parallel with the floor
How should the MSP be positioned for a panoramic tomogram?
Align MSP with vertical center line of the chin rest
What modality is being shown here?
Panoramic tomogram
What is the fracture in the mandible caused by?
Some infection at the bottom of the teeth (Tumor, mass)
Where is the TM joint located in relation to the EAM?
TMJ is just ANTERIOR to the EAM
What is the TM joint formed by?
Formed by condyle of mandible fitting into mandibular fossa of the zygomatic process of the temporal bone
What are the imaging indications for the TM joints?
- Arthiritus
- Myofacial Pain Dysfunction Syndrom
- TMJ Syndrome
What are these symptoms of in relation to mandible?
Clicking, pain, tinnitus, headaches, vertigo
TMJ
When the mouth opens, where does the condyle move?
When mouth opens, condyle moves forward to the anterior margin of fossa
When the mouth closes, where does the condyle move?
When mouth closes, condyle lies within mandibular fossa
What is being shown here?
Dislocated TM joint
What projection of the TMJ is this?
AP axial modified towne
Why do we get the patient to extend the chin in an axiolateral method for the TMJ?
Easier to open the mouth
What is being shown here?
Dislocation of the TMJ
What joint is being demonstrated here?
The superior TMJ
