Mandible and TMJ

Question 1

What is the Largest & strongest facial bone?

Answer 1

Mandible

Question 2

What does the largest and strongest facial bone consist of?

Answer 2

Body
Rami
Symphysis menti
Angle of mandible

Question 3

What is the symphysis menti?

Answer 3

The area of the symphysis menti where the 2 halves of the mandible fuse in infancy

Question 4

What are the clinical indications for doing xrays for the mandible?

Answer 4

Fracture
Neoplastic processes
Inflammatory processes

Question 5

What are the contraindications for doing mandible xrays?

Answer 5

Pregnancy

Where an OPG may be used, this is a preferred method.

Question 6

Routine mandible xrays

Answer 6

Mandible Routine Images

PA 0o
PA 25o

Slit Townes Mandible

Both Axiolateral (Lateral Obliques)

A STOP

Question 7

Axiolateral critique

Answer 7

Place patient in the lateral skull position
Raise head & support
Lift chin superiorly slightly
Do both sides in turn
(side closest is side shown)
CR – 15-25o cephalic
CP – to angle mandible (gonion) of raised side

Body, horizontal ramus, right horizontal ramus, madibular angle, ascending ramus, neck and coronoid process

Question 8

PA o degrees Mandible

Answer 8

Place patient in the true PA skull position
OMBL perpendicular to IR/film
MSP perpendicular
CR – VCR/HCR
CP:thru base of skull to lips in midline

Mandibular rami and lateral portion of body.
Exposure criteria Contrast and density are sufficient to visualise mandibular body and rami
Sharp bony margins to indicate no motion

Question 9

Slit townes mandible

Answer 9

Patient position
Tuck chin OMBL perpendicular to IR
CR – 300 caudal
CP – MSP between & passing through the angles of mandible

EITHER USE VCR (if supine or HCR ERECT Patient
OR PA …20-25 degree cephalic exit at the acanthion

Shows condyloid processes of mandible and temporo-mandibular fossae
CR passes through mandible mid-ramus

Question 10

What are supplementary views for mandible xrays?

Answer 10

OPG and SMV

Question 11

What does the SMV show?

Answer 11

Base of skull, petrous pyramids, mastoids, sphenoid sinuses, head of mandible, ramus, foramen magnum, zygomas

Question 12

What are routine views for TMJs?

Answer 12

Axiolateral view (open & closed)
Slit Townes (low centred)
Slit PA

Question 13

What are special views for TMJ?

Answer 13

SMV (midway between line joining the TMJs
Demonstrates: alignment of both joints), OPG (shows joints. Thin narrow beam because it decreases penumbra blurring, its used for curvy body parts)

Question 14

What are the clinical indication for TMJ?

Answer 14

Trauma
fracture
dislocation

Pathology
arthritis

Question 15

How do you prepare a patient for TMJ

Answer 15

LEAVE IN DENTURES

to get TRUE bite

Question 16

Schuller’s 25 Axiolateral Projection

Answer 16

Patient: semi-prone or seated oblique position with head in a true lateral position
MSP parallel to IR plane
IPL at 90o to IRplane
CR - 25o caudad
CP - to exit through the TMJ closest to IR (1 cm anterior to & 1 cm inferior to EAM to center of IR)Adjust head so MSP is parallel and the IPL is Perpendicular to IR plane Small field collimation
2 images per 18x24
mouth open & closed for each side
Both sides for comparison

For closed mouth position the condylar process of mandible should be seen within temporomandibular fossa.

For open mouth position, the condylar process should be seen anterior & inferior to the fossa.

Question 17

Slit Townes for TMJs

Answer 17

Position as for Townes skull
Positioning
Patient supine or erect facing tube
Chin tucked in so
OMBL = 90 to IR plane
MSP = 90 to IR plane
CR: is 30 caudal to pass through TMJs
Cassette:18 x 24cm placed horizontally
CP:CR passes through imaginary line joining both EAM to centre cassette

CP:CR passes through imaginary line joining both EAM to centre of cassette
Demonstrates:
petrous portion of temporal bones, IAM, Mastoid antra & air cells, mandibular condyles within TMJ, occipital bone and dorsum sellae lies within the foramen magnum

Question 18

Slit PA for TMJ

Answer 18

Position as for PA mandible
CR: VCR to horizontal cassette/table
CP: midway between line joining TMJs
Demonstrates: both joints simultaneously (condylar processes), heads and necks

Question 19

Supplementary techniques for TMJ

Answer 19

OPG
Tomography
CT
Fluoroscopy/DSA (Arthrography)