Mandible and TMJ Flashcards
What is the Largest & strongest facial bone?
Mandible
What does the largest and strongest facial bone consist of?
Body
Rami
Symphysis menti
Angle of mandible
What is the symphysis menti?
The area of the symphysis menti where the 2 halves of the mandible fuse in infancy
What are the clinical indications for doing xrays for the mandible?
Fracture
Neoplastic processes
Inflammatory processes
What are the contraindications for doing mandible xrays?
Pregnancy
Where an OPG may be used, this is a preferred method.
Routine mandible xrays
Mandible Routine Images
PA 0o
PA 25o
Slit Townes Mandible
Both Axiolateral (Lateral Obliques)
A STOP
Axiolateral critique
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
PA o degrees Mandible
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
Slit townes mandible
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
What are supplementary views for mandible xrays?
OPG and SMV
What does the SMV show?
Base of skull, petrous pyramids, mastoids, sphenoid sinuses, head of mandible, ramus, foramen magnum, zygomas
What are routine views for TMJs?
Axiolateral view (open & closed) Slit Townes (low centred) Slit PA
What are special views for TMJ?
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)
What are the clinical indication for TMJ?
Trauma
fracture
dislocation
Pathology
arthritis
How do you prepare a patient for TMJ
LEAVE IN DENTURES
to get TRUE bite
Schuller’s 25 Axiolateral Projection
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.
Slit Townes for TMJs
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
Slit PA for TMJ
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
Supplementary techniques for TMJ
OPG
Tomography
CT
Fluoroscopy/DSA (Arthrography)
