January 20- Extra Oral Techniques

Question 1

What are some ways Panorramic Images are used in a Clinical Setting

Answer 1

• Fractures, wisdom tooth assessment, lesions, eruption and development, retained teeth/root tips, TMJ, developmental anomalies

Question 2

What are the different types of Panoramic image receptors?

Answer 2

• Film and rare-earth intensifying screens cassettes
• PSP plate cassettes
• Solid state sensor cassettes designed to fit into

existing equipment

• Specially designed solid state sensors

Question 3

How does a Panoramic X-ray machine work (Very Simply)

Answer 3

The X-ray Tube and receptor rotate around the persons head at the same rate in a counterclockwise motion. As the X-ray passes through the structures they are projected onto the the screen/receptor producing a panoramic image.

Question 4

What is the Focal Trough?

Answer 4

• This is a 3D curved zone where the structures lying within the zone are well defined on the final pan image.
• Roughly a parabolic shape designed to conform to the shape of the dental arches in the majority of the population
• Laser lights aid the operator in aligning the patients dentition optimally in the focal trough
• Objects outside the focal trough are blurred, magnified and distorted

Question 5

Where should the dental arches be located in regards to the focal trough?

Answer 5

• The key to taking a good pan, is

to get the patients dental

arches as close to the middle

part of the focal trough

(darkest part) as possible.

• If structures are not in the

middle of the layer they appear

distorted.

Question 6

What happens when structures are outside the focal trough?

Answer 6

The edge of the layer (focal trough) is like a “cliff” where structures “fall off-out” and disappear from the image.

Question 7

How do you correctly position a patient to ensure their dental arch lies within the Focal Trough?

Answer 7

Orient the patient so that their mandibular incisors are within the notch in the Pan machines “alignment stick”

Question 8

What happens when a patients dental archs are aligned
A. at inner part of the focal trough

B. at the outer part of the focal trough

Answer 8

Question 9

What is the common Vertical Angulation of the X-ray in Pan X-ray machines. And what effect does this angulation have on the images produced.

Answer 9

the common vertical angulation is 8 degrees to the horizonal, This angulation causes structures IN FRONT of the rotational center to appear HIGHER and structures BEHIND to appear Lower

Question 10

What effect does Verticle Angulation have on resultant Pan radiographs?

Answer 10

Verticle angulation can cause misrepresentation of the distances between structures
ie: the distance between the apex of the root and the mandubular canal

Question 11

In a Pan radiograph what is a Single Real Image? And when are they formed?

Answer 11

• single real images result when a structure is located in front of the centre of rotation (i.e. between the image receptor and the rotation centre) and is intercepted only once by the x-ray beam
• The majority of the images seen on a panoramic image

are this type e.g. maxillary sinus, floor of orbit, soft tissue

of nose etc

Question 12

In Panoramic radiographs what is a Double Real Image? And when are they formed?

Answer 12

Double Real Images are produced if a structure is located in front of the centre of rotation and is intercepted twice by the x-ray beam.

• These images are produced by structures in the posterior midline such as the hard and soft palate, hyoid bone, epiglottis and the cervical spine that fall into a diamond shaped zone produced by the the movement pattern of the x-ray beam.
• One image is the exact mirror image of the other

Question 13

in Panoramic Radiographs what is a Ghost Image and how are they formed?

Answer 13

• Ghost images are formed when the anatomical structure is located behind the rotation centre of the x-ray beam. i.e. they are between the x-ray source and the rotation centre.
• Ghost images are not mirror images, appear on the opposite side, are more blurred, larger and superior than the real counterpart.
• These usually result from external objects such as earrings and necklaces, but can also occur with dense anatomical structures that are in the midline such as the angle of the mandible, the hard palate and the cervical vertebrae.

Question 14

What is this an example of?

Answer 14

This is an example of an artifact (earrings) GHOST IMAGE.
Note how the earrings are distorted and where they are projected.

Question 15

what has caused this misrepresentation in the panoramic image?

Answer 15

Verticle Angulation of the X-ray beam

Question 16

Who made the best deck of flashcards?

A. Ben “the Hulk” Hughes

B. Logan “The horror” Orr

C. Justin “the Master” McMurray

D. Trent “the Terrific” Orth

E. Dallin “Okay” Kay

Answer 16

E. Yup, thats right….ME, now get back to work!

Question 17

What are 8 steps of how to take a pano image?

Answer 17

1. Adjust machine settings to patient build and height
2. Lead apron (and thyroid collar at some clinics)
3. Ear-rings and dentures/appliances out
4. Patient stands upright, holding handles, biting into groove in biteblock with chin on chin rest
5. Immobilize head with temple supports
6. Use the light beam markers to check mid-sagittal plane is vertical and the Frankfort plane is horizontal.
7. Have pt put tongue on roof of mouth, close lips, be very still.
8. Expose and watch patient

Question 18

IF the patient moves durng the exposure, what should you do?

Answer 18

Stop the exposure

Question 19

Getting the patients teeth in the _____ _____ is crucial to accurate patient positioning for a clear image.

Answer 19

Focal trough

Question 20

This patient positioning error in a pano image makes the anterior teeth appear narrow.

Answer 20

Patient too for forward. In front of focal trough.

Question 21

This patient positioning error in a pano image makes the anterior teeth appear widened, magnified, and out of focus.

Answer 21

Patient too far back. Behind focal trough.

Question 22

This patient positioning error makes the right jaw minimized and the left jaw magnified.

Answer 22

Head rotated to the right.

Question 23

This patient positioning error causes a prominent ghost image of the spine.

Answer 23

Patient slumped and/or patient unable to straighten neck due to arthritis.

Question 24

In this patieint positioning error the frankfort plane is not horizontal, the mandibular symphsis is missing, the lower anterior teeth are distorted, excessive ghosting of contralateral mandibles and cervical spine occurs, the lower incisors out of focus, and the occlusal plane makes a “smiley face”

Answer 24

Chin tipped too low

Question 25

In this patient positioning error, the hard palate is superimposed over roots of the maxillary teeth and overlapping contacts of many teeth are seen. The occlusal plane makes a “grumpy face”

Answer 25

Chin tipped too high

Question 26

Lateral cephalograms can be used to assess what 4 things?

Answer 26

1. Orthodontic/orthognathic surgery planning;
2. Soft tissue profile of the face (filter – tissue)
3. Bone of the face and skull
4. Trauma and disease

Question 27

Cephalometric imaging aids othrodontics in these three ways?

Answer 27

1. Orthodontic records
2. Craniofacial growth
3. Orthodontic follow ups

Question 28

Posterioanterior projections (PA projections) are used for what three things?

Answer 28

1. Evaluate facial growth
2. Trauma and disease
3. Developmental abnormalities … orbits, sinuses and nasal cavity

Question 29

The submentovertex projection technique is used to identify these four things?

Answer 29

Identify position of the:

1. Condyles
2. Base of the skull
3. Zygomatic arch fracture
4. Lateral wall of the sinus

Question 30

The ______ _____ projection helps to identify the

1. Maxillary sinus area
2. Frontal and ethmoid sinuses
3. The orbits contour
4. The nasal cavity

Answer 30

Waters view

Question 31

The Reverse Towne projection is used to detect what?

Answer 31

Fractures in the Condylar neck and Ramus area

Question 32

What are the names of the following projections shown in the attached table, from left to right (far left #1, farthest right #5)

Answer 32

1. Lateral Cephalometric
2. Submentovertex (SMV)
3. Waters view
4. Posterioanterior (PA)
5. Reverse Towne