Script5-Part2-Without the Last 10 Min

7/30/2019 Script5-Part2-Without the Last 10 Min

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Part 1

Extra-Oral Radiographs

Today our lecture is about panoramic radiography and extra oral radiography.

Panoramic radiograph is an extra-oral radiograph. Its also called

(Orthopantomograms).

that is used to examine the upper and lower jaws on a single film.

When taking a panoramic radiograph the patient may stand up or sit down

depending on the type of machine. The head, chin & the occlusal plane

must be in correct position.

The source of radiation always moves behind the patient and the film in

front of the patient.

Panoramic radiograph is called 2D modality however it is highly used it

shows the mandible, maxillary sinuses &TMJ all in 1 radiograph.

Nowadays we have other 3D modalities (like cone beam CT) & we use these

modalities to generate panoramic radiograph. (We can also generatepanoramic radiograph from 3D images.) We also have normal panoramic

radiographs. (search for the differences)

I am sure many of you took a panoramic radiograph when u went to ur dentist to

check your dental status, old teeth, sinuses. It is also the 1st

step to see

abnormalities in TMJ & is commonly used to see the status & position of 3rd

molars.

Radiation dose is equal to 4-5 times more than intra-oral films which is not

a lot.

Around 50 landmarks can be seen in the radiograph. Doctor said we

should search about them.

Panoramic radiograph can also show us pathology, but its resolution is not as

good as intra-oral radiograph so we cant depend on panorama to show us caries

or periodontal problems.


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Most common anatomy landmarks are in this pic.


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& lastly

We are expected to memorize all of them.

Why? To differentiate the normal from abnormal anatomy.


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Now we are going to talk about soft tissues that can be seen on the panoramic

radiograph

1-tongue

2-soft palate

3-ear lobe

soft tissues appear radiopaque in comparison with air.

We have 3 air spaces:

1- Between the tongue and palate. Its calledpalatoglossus / glossopalatine

air space

2- Between the nose and pharynx. Its callednasopharygeal air space

3 Between the oral cavity and pharynx. Its calledglossopharyngeal /

oropharyngeal air space.

Comparison between tomography and scanography:

Tomography means sections, panoramic will not be taken as a single shot the

machine rotates at least 180 degrees & then forms the image. Tomography is a

radiographic technique that allows the imaging of one layer or section of the body

while blurring images from structures in other planes.

Scanography is the rotation of x-ray tube on x focal axis so that another x-raybeam scans the y axis.

ROTATION CENTERS

In panoramic radiograph the film or cassette carrier and X-ray tube head are

connected and rotate simultaneously around a patient during exposure. The

pivotal point or axis around which the cassette carrier and X-ray tube head rotate

is termed a rotation center.

Some machines have 2 or 3 rotational points depending on themanufacturer. Their function is to facilitate getting the real dimension of the jaws

and to get a clear final image.

Double-center rotation Triple-center rotation Moving center rotation

FOCAL TROUGH


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We have another term called focal trough or image layer which is the

differentiation of focal trough: its a three dimensional curved zone in which the

structures are clearly demonstrated on panoramic radiograph. Structures out of

the focal trough will not appear clear on the radio graph, this is imaginary, some

machines will allow you to choose the shape of the focal trough, so by choosing a

narrow focal through that suits the patients jaw this is going to give you a clear

radiograph. If I increase the width of the focal trough the final panoramic

radiograph will not be clear.

EQUIPMENT:The doctor started to view images about the machine that we use in our clinic we

have ways to make u see the lines. We have 2 lines & there are buttons to adjust

the lines like the mid-sagittal line which has to be perpendicular to the floor. And

Frankfurt line, which is coming from the upper border of the external auditory

meatus to the lower border or the orbital rim, parallel to the floor.

I will summarize what u have to do when u have a patient in your clinic and

u want to do a panoramic radiograph:

1. The patient comes to you, you must make him stand straight as tall as

possible.2. The patient should not slump or bend since this will result in a shadow

in the middle of the radiograph.

3. The patient bites on the bite block and make sure the teeth are edge to

egde & tongue is on the palate.

4. If tongue must on the palate, by asking the patient to put his tongue on

the palate or ask him to swallow. If it is not on the palate this will

obscure the clearance of the maxillary teeth. The plastic side of the

cassette must be facing the tubehead.

What is the difference between panoramic radiograph machine & intra-oral

radiograph machine?

1. Its the collimator, the collimator in panoramic machine is a vertical narrow

slit it's not rectangular or round like normal machines, the collimator is in

the tube head and there is also vertical slits in the cassette.


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2. The vertical angulation of the tube head in not varied. The tube head is

fixed in position so that the x-ray beam is directed slightly upward.

Panoramic radiograph is a kind of tomography which deals with section.

You are building sections until the cycle is finished. Sometimes if the patient

is huge the tube head will stop suddenly from rotating (which prevent some

sections to appear in your final image) & other times it will continue.

Number of tomography images taken depends on the machine & its type.

HEAD POSITION

the head position consists of a chin rest for the patients chin. Notched Bite blockis there for the patient to bite on, forehead rest and lateral head support.

Sometimes the shadow of the head support may appear on the radiograph. If you

put frankfurt line parallel with the floor and the patients forehead on the

forehead rest, then you can notice that the occlusal plane is slightly downward

inclined and the beam is slightly come downward.

You can choose the side you want to capture, with the controllers of the

machine which control time, voltage and mille ampere to make the radiograph.

However, the machine usually comes with a fixed time.

The extra oral film must be inside of the cassette. We have several types of

cassettes: green light cassette and blue lights cassettes and it depends on the

type of phosphor used and the screen spectrum must match the phosphor

spectrum. There are different types of cassettes such as rigid, flexible, curved and

straight depending on the panoramic x-ray unit.

PURPOSE & USE

1. We use it to see all the teeth in the both jaws in the same image.

2. To evaluate impacted teeth

3. To evaluate eruption patterns, growth, and Development.

4. assessing wisdom teeth this is a very important although as I told you

nowadays due to cone-beam computed tomography (CBCT) 3D imaging is

considered the golden standard in assessing the relationship between the

third molar and the canal. Using Panormic radiography you can sometimes


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see a shadow of the canal superimposed in the third molars (due to loss of

bone, loss of cortical bone at that area) but this doesnt happen with CBCT.

5. To examine fractures of the mandible.

6. To Detect Diseases (periodontal diseases there is loss of bone and vertical

healing), lesions, and conditions of the jaws.

Its inadequate to use panorama to detect lesions much better than intra-

oral radiograph.

7. Assessment of locations of the objects in the jaw and permanent teeth

impacted by using panorama. Usually lingually impacted looks high and

magnified

8. To Examine the extent of Large lesions

9. To Evaluate Trauma. & fractures of the mandible and the

bilateral/contralateral condyle fracture

10.Examination of the sinuses nasal cavity orbit

11.Examination of the sinuses nasal cavity orbit

12.Before and after implants: usually when the patient comes to you and he

wants to do an implant you can start by taking a panoramic radiograph or

peri apical radiograph. However, panorama is not enough becausepanorama tells you if there is bone but you have to do another test by cone

beam CT to make sure. If panorama shows you that there is no bone then

you have to stop and ask the patient to go home.

Advantages:

1) Comfortable for the patient because there is no film inside the mouth

2) Easy to use for the incooperative patient like edentulous patients, children, old

people.

3) Less exposure if you want to compare it with CMS (complete mouth survey)

4) Wide coverage for mandible and maxilla

5) Reduce superimposition in anatomical structures

Disadvantages

1) Equipment cost. Initial cost of the machine is relatively high.

2) Image quality. The images of the radiograph are not sharp compared to intra-

oral images, the resolution of the panoramic image is 4 lines per millimeter but


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the intra oral is 5 times sharper than panorama.

3) Objects outside the focal trough may not be evident.

4) Age limitation. Not suitable for children under 5 years of age because of the

relatively long exposure time.

5) Dark room processing (like students in the center because there is no safe light

they have to change the film in the dark each time).

6) Changing of the bite block because of hygienic purposes. It has to be sterilized

and covered.

7) Minimal bone changes cannot be detected in the panoramic radiograph due to

super imposition.

Patient preparation

1. Explain the radiographic procedures to be performed.

2. Place lead apron, without thyroid collar not to block the the x-ray beam and

also double sided lead apron is recommended ( one that protect the

patient from the front and the back.

3. Remove all objects from the head and neck area. earrings , necklaces,

napkin chain eyeglasses. And complete and partial dentures

4. instruct the patient to Stand or sit (as tall as possible) with straight back,the vertebral column must be straight to prevent white shadow to appear

over the middle of the radiograph.

5. Patient must bite a plastic bite block, the front teeth should be placed in

end to end position in the notch found on the bite block, and this groove

will align the teeth and the jaw in the focal trough area.


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COMMON ERRORS

>> Ghost image:is a radiopaque artifact seen

on panoramic film that is produced when a

radiodense object penetrated twice by the X-ray

beam. This object is between the source and the

rotational center appears on the radiograph as an

object indistinct, higher and magnified the object is

located behind the rotational center. usually are the

projected image of a real bony structure to the

opposite side of the image. And a metal earrings glasses and it will appear radioopaque.

Ghost Images

1. Image from other side of patients jaw that is seen as a blurred shadow

2. Results from radiodense objects left on patient during exposure

3. Resembles its real counterpart

4. Found on opposite side of film as blurred, enlarged and higher than actual

object

2) Wearing thyroid collar blocks the x-ray beam

3) If the patient is not in supine position.


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Patient positioning errors

2) Exaggerated smile line of the mandible due to chin tilted down so the incisor

will appear larger. This happens due to downward Frankfurt plane, students

usually lose marks with this preoperative radiograph.

3) Reverse smile/flat mandible line: Occurs when the chin is tilted upwards & the

head backwards. This will result in superimposition of the teeth, palate and they

will also appear magnified.

4) Inward position of the teeth related to the focal trough. If teeth are anterior to

the focal trough it will be smaller because its near the film but if the teeth are

behind the focal trough it will appear magnified and large because its far away

from the film.

5) Teeth are not edge to edge even if it is in the focal trough.

7) If the patient moves during the procedure there will be magnification on one

side and magnification on the other side. Ex. if the patient moves to the right; the

right side will be magnified because its far away from the film and the other side

will be minified because its closer.

PLZ CHECK THE PDF FILE FOR THEERRORS

This link may be helpful too http://www.docstoc.com/docs/98403205/Panoramic-

Radiography

End of part 1

Done By:Jad el Benni

Stephanie Nawas


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Part2 :

Other types of extra-oral radiographs:

Panoramic radiograph which is the most common type of extra-oral radiograph.

Other types will be discussed ex. Lateral cephalometric radiograph is highly useful

for orthodontic assessment. Putting the film laterally and the same convert

machine is used. Here you just need to change the orientation of the tube to the

other side (not the side of the panorama). The patient must be standing upright

with a mid-sagittal plane perpendicular to the floor. And the ala-tragus (beam)

line must be parallel to floor. So the chin is lifted up. Patient standing at a specific

distance of the machine & this process is during cephalometric analysis.

Other extra-oral radiographs:

Lateral oblique radiograph= No specific distance from beam. This type of

radiograph shows the skull vault & facial skeleton from the lateral aspect.

By changing the film, patient head or beam position u can get different extra-oral

radiographs.

Lateral cephalometric radiograph as well which we discussed above.

Submental vertex canthomeatal line is a line parallel to the film.

what is the cantho-meatul line? A line that extends from

cantho= canthus of the eye

meatal= external auditory meatus.

The head is extended and the chin is raised so that the cantho-meatal line forms a

37 degree angle with the horizontal and central ray. The beam is coming from thelateral side from the floor of the mouth.

Frankfurt line: plane formed by drawing a straight horizontal line from the top of

the ear canal to the bottom border of the eye.


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You must know what kind of extraoral radiograph that we have.

(The doctor is showing several types of extraoral radiograph)

Posterior-anterior radiograph;

beam is coming from

posterior of the patient, and

the film anterior to him.

Lateral skull (I think the doctor is

referring to lateral cephalometric

radiograph); patient will stand not at

specific area (no specific distance) *Icant get what the doctor is saying, sorry

Reverse Towne; film anterior

to patient, patient touching the

film with his forehead withhis mouth open.

Waters; film anterior to

patient, patient touching the

film with his chin.


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This table is required

We can get different extraoral radiograph by changing the position of the film,

patient and the beam.

Canthomeatal line: An imaginary

line from the canthus of the eye

to the external auditor meatus.

Frankfort line: An imaginary

line from the infraorbital to

the external auditory meatus.

Frankfort line is

10 to

canthomeatal line.


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(The scientist had discovered all kinds of extraoral radiograph that it is least likely

someone would discover another)

(The doctor omitted TMJ radiography and Cone-Beam technology from the

extraoral radiograph)

Waters.

Canthomeatal line at 37 with film.

The beam is perpendicular to the film, coming from behind the patient(FOM).

Posterior-anterior Cephalometry (PA ceph).

Canthomeatal line at 10 with film.

The beam is perpendicular to the film, coming from behind the patient.

Reverse Towne.

The patient is touching the film with his forehead and opens his mouth

(THIS IS THE ONLY RADIOGRAPH WITH MOUTH OPEN).

elongated image

Canthomeatal line at -30 with the film.

The beam is perpendicular to the film, coming from behind the patient.

In the exam, the doctor will bring radiograph images and the student is required toidentify which type of extraoral radiograph that resultant image is representing.

So students are supposed to be able to:

Differentiate between the types of extraoral radiograph.

Familiarize with the radiographic appearances in each resultant image.


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Oblique lateral.

Body of mandible: film in contact with cheek at molar areas. (Resultantimage will show the molars)

Ramus of mandible: film in contact with cheek at ramus area. (Resultant

image will show the ramus)

Because we dont want to see the molar and here we want to see the ramus.

Look here, in case of the body of mandible the patient is touching the film androtating his head. So, to make sure that there is configure to the molars, the

beam from contralateral side is directed to the molars but in case of ramus the

beam and the ramus of the lateral. And look here we can see the ramus. And

here we can see the body and the molar. so there is 7 extraoral radiograph that u

must know and differentiate between them. This table finishing all the chapter.


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EXTRAORAL PROJECTION TECHNIQUE

Indication : if patient cant open their mouth sufficiently for intraoral radiograph

during large area of pathological involvement , injured to the wall , tissue, thebase , the skull, the sinuses.

Occipito-mental radiograph is best to show maxillary sinus and zygomatic

bone. Obtaining growth and unerupted inverted teeth during fracture no

longer exclude for TMJ because now we have cone beam 3d dimension used

for TMJ.

Extraoral radiograph such as the panoramic radiograph and PA Ceph (2D)

can show us fractured in one side.U know we have in anatomy, u can divide into 3d plane axial, horizontal ,

sagittal and coronol. The cassette will be parallel to the mid sagittal plane and

beam I directed perpendicular vertical to the plane.. incase posterioranterior

view the cassette rise vertically to midsagittal plane and the beam is directed

parallel to mid sagittal plane.

# We have a near point and we have far point. near point is the point xray

beamis directed, the far point is far from radiograph. So in case the pulp of

lateral oblique for example your aim is to see the opposite side of the mandible.

Your beam will come from right for example your final image will be at the

left. Near point and far point (lateral views)

( doctor explaining about lateral view) refer page:329-330

You will do lateral cephalometry in the clinic.

In case of cephalometry: the ala tragus line must be parallel to the floor (long axis

of horizontal). The film is perpendicular to the floor and parallel to mid sagittal

plane. Beam is perpendicular to film.

Lateral oblique view- can state molar region and ramus, mandibular body.

another technique that help us to locate 3rd molar. Has far and near point.

-Body of mandible

Near point: 2cm below the angle of mandible. near to the source (beam)

Far point: point of film (1stmolar), on the opposite site.(center of pharynx)

-The ramus, condyle angle, and coronoid process.


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Near point: 2cm beyond the mandible and 1st molar region

Far point: center of pharynx

Your beam center ray in the center of ramus.

Indication: inverted 3rd molar, when we cant use intra oral film, fracture of the

body, ramus, mandible and coronoid. Syalography (esp. submandibular gland )

Lateral oblique radiograph useful in sjogren syndrome.

End of Part 2

Done by

Jad el Benni, Nabiha mokhtar, Arina Nasri, Heba Radaideh, Razan Tannous

THANKS FOR YOUR COOPERATION

Good luck in your exams

Script5-Part2-Without the Last 10 Min

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