Lec9_Intra Oral Radiographic Techniques

7/28/2019 Lec9_Intra Oral Radiographic Techniques

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Intra oral radiographic techniques

The doctor started the lecture by asking what we mean by intra oral technique.

We need to have small film if it is in the oral and that fits but this is not 100% true and

not necessarily because sometimes we can use small films in extra oral, so extra oral

and intraoral means that if the film is inside the mouth during radiograph this is intra

oral and if it is outside it is extra oral it does not depend on size.

The Dr said that we have to pay attention cause this what we are going to take the next year in the

clinics.

Our reference is lannucci book third edition is okay and fourth edition is the best .Chapters 16-17-18

which covers this topic.

Intraoral radiographs will show us the teeth and adjacent structures, extra oral

radiograph it can show us teeth and surrounding structure but there are differences,

what is the difference for example between periapical radiograph and panorama

radiograph?

For example if I want to see caries which one is better? Periapical is

better...why? Because periapical will achieve one advantage of ideal film placement

which is the close relationship between the film and the tooth, it is very close so the

image will be clear, essential resolution is high, around 20 lines per millimeter for the

periapical but when the film outside the mouth "panorama" the film is far from the

tooth, there is magnification, the film is not clear, spatial resolution is only 4 lines per

millimeter. So if we have a patient with caries we dont ask him to take panoramic

radiograph to see caries; we ask for intraoral radiographs instead.

But for example impacted third molar is difficult to be seen in intraoral radiograph so I

go for panoramic" extra oral radiograph.

So why intraoral radiograph? We will have the permission to see the deep

surrounding structure which cannot be seen by visual inspection. If I can see the caries

by my eyes I dont take radiograph, unless I want to see something else and suspect

that caries reaches the pulp and there is a periapical lesion; in that case I will take

periapical radiograph. But if it is simple case of pulpitis, reversible pulpitis I will go to

the treatment without X-RAY. So it will improve the quality and the diagnosis and the

treatment because if there is a diagnosis this is will be false negative or false positive

and finally it will be so long treatment, extraction for example.


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Types if IntraoralRADIOGRAPHS:

1-PERIAPICAL RADIOGRAPH:

Next year in the clinic you will get orders from ITU, in the order they will choose thetype of radiograph it can periapical, bitewing, occlusal panoramic, and if is periapical it

means the dr wants to see periapical area, we expect to see at least 2mm beyond the

apex, so if we took a periapical radiograph without 2 mm beyond the apex we will lose

mark. The dr pointed at a periapical radiograph in the slide and he says that I can see

periapical area and we can see 2mm at least beyond occlusal surface, so periapical will

show me:1-crown 2-root 3-peri-apex

2-bitewing:

From it is name it means the maxilla and the mandible, it shows me the crowns

for upper and lower and part of the roots (1/3-2/3 roots and adjacent bone).

So if the student showed me crowns of lower teeth without the roots it means

incorrect film placement and he will lose marks, in this type of radiograph we expect

to see both of the upper and lower teeth equally. So the occlusal plane must divide the

film into two halves.

The dr pointed at a dot appears in a radiograph in the slides, he said it is not important

if the dot appears on the mandible or the maxillary but if appears in periapical

radiograph the dot must be on acclusal plane and must not be at area on the apex. So

we have to remember when we put the film in the holder to put the dot in the slot.

3-occlusal radiograph:

The size of acclusal radiograph films four times bigger than other films, we use it to see

large number of teeth and large segment of dental arch. We have six types for occlusalradiographs "maxilla: 3 types, mandible: 3 types" later on we will talk about it.

Now the Dr talks about an occlusal radiograph for the maxilla in the slides and asks:

from the anatomy what are these two foramens? He answered that this is two canals

and two foramens some of the students answered it is nasopalatine and he said it is

correct. No one knew the right answer for the other foramen. (I think its the greater

palatine foramen)


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When I take a radiograph I should ask myself: Will I get benefit from it? Is the benefit

more than the risk? If yes we go for the radiograph.

The frequency depends if the patient is high caries, and there is indication for high

frequency of caries then you must see him/her at short periods.

Now the dr started to talk about the something called 20 CMS (complete mouth

series):

It is name is twenty CMS, why? Because it is 20 films for each patient, actually in some

schools they ask the student to make 20 CMS, it shows me the condition of all teeth

and the surrounding bone, and to see areas of different angulation to get the general

condition of the jaw, bone. However CMS it is not used in some universities, in our

university here we dont prefer to do CMS and we usually take one or two radiographs,

if we need full coverage we go for panoramic radiograph.

CMS: complete mouth Series, it is twenty films, 5 of them periapical films of upper

anterior, 3periapical films for lower anterior, 4 periapical films for maxilla and 4

periapical for mandibular posterior teeth and we have 4 films bitewing films, so they

become 16 periapical films and 4 bitewing films. Bitewings where teeth have

interproximal contact, film size depend on your technique, ideally we use size one for

anterior teeth and we use size two for posterior teeth and we can change the size

according to the patient jaw size.

Summary for CMS:

It is a series of IO radiographs that shows the entire tooth bearing area In U/Ljaws (dentulous and edentulous).

20 films. BW only in areas with interproximal contact. Film size indicated by technique and size of arch.

Periapical radiograph: main indications:

1- Detection of caries and periapical infection.Actually it is more for periapical infection because caries is better to be seen bybitewing.


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2- Assessment of periodontal status: Like widening of PDL space and loss of bone,calculus.

3- After trauma of tooth and supporting structures (bone).4- Assessment of presence of impacted or unerrupted tooth: like in third molars

but sometimes we need panoramic radiograph especially for patients with

limited mouth opening and gagging reflex which usually initiated when the film

touches the dorsum of the tongue or the soft palate.

5- Assessment of morphology before extraction: in the surgery we will learn thatwe need x-ray before extraction, for example to know there are no ankylosis

and no dilacerations before the extraction problem exists which may lead to

fracture of the jaw.

6- During endodontic treatment: to see the working length. And nowadays we usecone beam radiograph in endo but not during the treatment "not to check the

working length "but when we have problems, like fracture, to detect a cystic

lesion which cannot be seen in intraoral radiograph we need the third

dimension we will think about cone beam CT.

7- Assessment of position and associated implants: for example osteo integrationcan be seen in periapical radiograph.

Ideal positioning requirement:

If we want to make radiograph we have to remember five points:

1- Correct patient position.2- Correct film position.3- Correct vertical angulation.4- Correct horizontal angulation.5- Centering the beam.

We will start talking about each point:

1-patient position:

The mid sagittal plane must be Perpendicular to the floor and the occlusal plane must

be parallel to the floor, if the patient opens his mouth during x-ray, the mandible will

go down so you have to tilt the plane (head)?slightly backward to make sure that the


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mandible, the jaw being imaged, is parallel to the floor.

And you have to raise the chair or lower it according to the jaw.

The dr talked about film tooth relationship he said that in ideal positioning we need:

1- Minimal tooth film distance (to be in contact)2- We need parallel tooth film placement. But we cannot achieve this because the

teeth are tilted, and when the film is in contact to the tooth the film will not be

parallel.

3- X-ray perpendicular to both.4- In parallel technique the source of radiation should be as far as possible from

the tooth.

Then I want to make parallel technique and I want the film to be on contact to the

tooth at the same time and if it is then it won't be parallel, so what to do?

We move the film to the mid of palate or the mid surface of the tongue, to have

parallelism. But when we put the film far we will make problem, the problem of

magnification, like panorama has problem magnification because it is far from the

tooth, now when you put the film in the mid of the palate you will get magnification,

so how we overcome the magnification? Simply by using long cone technique. So if we

took a radiograph by parallel technique using short cone our radiograph will be wrong,it must be long cone"61 inch","40 cm".

Paralleling technique ( long cone technique, or right angle technique) and thiscan be achieved by putting the film far toward the mid of the palate, short cone

will end up with magnification, long cone will end up with minimum

magnification.

2-film position:

Film holder:

We will not use the patient finger in parallel technique to stabilize the film; we use

holders, but what kind of holders? The most important one is Rinn XCP and it is the

one which we use in the clinic, if it is yellow holder we use it for posterior teeth, blue

for anterior, red for bitewing, and green one we use it for endodontic.

After we use holders we have to sterilize them, because they are semicritical devices,

never ever use the same film holders for two patients.


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Film holder devices:

1- Precision attachment.2- Stable (Styrofoam bite blocks): disposable film holder made from plastic and we

get rid of it after each use.3- snap A-RAY-film holder: we use it with patients with gagging reflex, patients

with shallow palates because the patient will hold this holder with his hand and

it not bulk so he can move it as far as possible, we use it also in third molars but

if we dont have this one we use our minds and we can use: hemostat instead of

it, it will help us to catch distal located third molars.

Film size and placement:

Anterior region:

Long axis of film packet should be vertical. Size 1 films "ideally".

In our clinics the technicians prefer to use size 2 in order to cover many teeth, because

usually the patient comes and need a radiograph for his central, lateral incisors and

canine so we use film size 2 to save films as much as we can. And that means we have

to adapt our techniques according to the clinic.

Posterior region:

Size 2 films. Long axis of film packet should be horizontal.

The area of interest must be in the middle of the film, if we want to take an image for

canine we make sure that the canine is in the middle of our film for example.

Note:1/8 inch must be beyond the incisal edges must be beyond the incisal edges

from occlusal plate and at least 2 mm periapically.

3-correct vertical angulation:

What do we mean by vertical angulation? We have positive vertical angulation and

negative vertical angulation. If I want to make an image for maxillary teeth the vertical

angulation will be positive because it will be above occlusal plane "horizontal plane,


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axial plane "so the vertical angulation is the angle between the x-ray beam and the

axial plane in case of maxillary it will be positive and in case of mandible it will be

negative. At the horizontal plane the angulation will be zero above it positive and

below it negative. In parallel technique by using holders no need to memorize vertical

angulation because you will follow your holder angulation.

4- horizontal angulation:It is the angle between the x-ray beam and the mid sagittal plane. If I want to image

central incisor the cone must be toward the central incisor, the beam should be

passing between central incisors, I will not ask you to make a radiograph for central

and put your cone here "at the canine" because it means incorrect horizontal

angulation and will result in overlapping.

If I want to make image for premolars the central beam if we imagine it as coming out

from the cone must pass through contacts and by this we will have correct horizontal

angulation .incorrect horizontal angulation it will be overlapping.

Note: the more posterior the radiograph the more the horizontal angulation.

Let us go back to the vertical angulation: the central beam should be perpendicular to

the long axis of the tooth, and this is done automatically by using holders, usually the

true vertical of the tooth varies from vertical axis of the crown by 5-20 degrees.

The correct horizontal angulation should be through the contact areas of the teeth (i.e.

perpendicular to the outer surface

of the tooth) and again if it is

incorrect it is will be overlapping.

We have problem in the maxillary

canine: usually when the students

make an image for the canine there

will be overlapping between canine

and first premolar? How to solve

this problem? By making the cone

a little bit distally and change the

horizontal angulation inorder to


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over the contact and this is called distal shift, so if we bring the beam through the

canine it will be overlapping.

5- Centering the beam:Imagine the beam at the central ray, the central ray must be directed to the tooth and

the film through a point that allows complete coverage of both ,otherwise it will be

cone cut(partial image) and it is the

most common mistake made by the

students.

Cone cut: area will not be covered bybeam; your cone is not following the

ring of the holder.

Sometimes the student will put the

cone on the central of the ring but

because of movements made by the

patient it will change.

Previously the Dr talked about something called 20 CMS :and it is ideally when we take

one for upper centrals two for laterals and two for canines, in the lower: all the

incisors(central and lateral) will be taken by one film and one for each canine.

However we will not do this at the clinic.

Ideally 8 periapical radiographs,2 for maxillary posterior, 2 for mandibular posterior

teeth one for premolars and one for molars and one for upper premolars and one formolars(for right and for left).

If I want to make image for premolars it means I must see the first premolar and the

second premolar in the middle of the film, it means I have to start from the distal half

of canine and for molars we start from the distal half of second premolar.


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General guide lines:

1. White surface of the film always faces the beam2. Anterior films are always vertical, posterior films are horizontal.3. The dot in the slot.4. Place the film away from the teeth (in the mid of the palate)5. Use film holders and centering the beam.6. Ask the patient to close slightly to stabilize the film.7. The patient must close his lips on the holder. Exposure sequence:

We usually follow the sequence in CMS to avoid repeating and minimize movement;we usually start with anterior teeth, why? because:

* Film smaller easier to tolerate by the patient.

* Less likely to cause gagging.

The posterior teeth:

We start with premolar then molars same as reasons as above (1,2,3,4,5,6,7,8,)like a

clock,

For anterior teeth begin with upper right canine all the way to the upper left canine

then lower left canine all the way to the lower right canine to left canine.

But for posterior teeth begin with

1. maxillary right quadrant expose premolar film then expose molar film2. mandibular left quadrant expose premolar film then expose molar film3. maxillary left quadrant expose premolar film then expose molar film4. Mandibular right quadrant expose premolar film then expose molar film

We usually do bitewings before parallel technique.

Look this is parallel technique and this bisecting technique, bisecting technique the

cone will come high and the shadow will be on the film over the roots so this is notgood, but in case of parallel technique the shadow will be above the roots.


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Advantages of parallel technique:

(Simple, accurate, the shadow will be over the tooth, duplication)

American academy of oral radiology advises using parallel technique not bisecting

technique because it is geometrically better. (Dimensional accuracy and high details)

Reproducible which means we can use the technique again and again for the same

patient.

Shadow of zygmotics bone will be above root.

Simple.

Disadvantages of parallel technique: (film placement & discomfort)

Film position can be uncomfortable "arch anatomy sometimes makes it impossible"

Holders in lower third molars are very difficult.

However of its disadvantages this is what we do in our school.

Difficulties in positioning may be because of:

Shallow palate Tori Third molar

Gagging Endodontic

Children Handicapped

patient.

Shallow palate:

if we have shallow we can increase dimensions by putting cotton rolls above and

below the holder, we can increase the vertical angulation by 15-20 degrees.

In case of lower premolars the shallow floor of the mouth the patient also will feel

pain what we have to do is to put the holder like this "under the tongue "and then

push the tongue with the holder, we can gently bend the corner of the film but

sometimes this will result in artifacts.

Tori:

If the patient has Tori it is better to put the film on the far side of the torus, if it is in

the mandible we put it between the torus and the tongue.


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Mandibular third molars:

Film cannot reach the distal surface of third molar, and the solution for this we direct

the beam from distal surface.

Another technique we can use hemostat; draw a vertical line dropped from the outer

corner of the eye and put another point 1cm above the lower mandibular border and

this will be your point of entery,the central ray directed to this and this another

solution for impacted third molars.

If both techniques failed then go to panorama.

Gagging: Gagging is common in clinic:

We ask the patient to concentrate on breathing from the nose during procedureor we ask him to count number, anything to destruct his thinking.

We use bisecting angle technique inorder not to touch the palate. In severe cases may spray palate with local anesthetic before film positioning. Another solution for gagging dont put the film at the surface of the tongue, we

put the film horizontally and made it with bisecting angle technique. This

solution can also be applied for kids.

Endodontic:

Difficulties of placing films are because of rubber dam and clamps.

Solutions: using a special film holder (its color is green) which has a small basket in the

bite platform to accommodate for the handles of endo instruments.

Another solution if these holders are not available we can use hemostat or snap-A-ray.

The third solution: I cannot depend on the radiograph to take measurements becauseof magnification problems, and in endo I need to know the real length of the tooth. So

we need to put the file inside the tooth to know the real dimension and I know exactly

the length of the file that I inserted (for example I measured it by a ruler 10mm), when

I took a radiograph, on the film the file appear as 15 mm. So I know that the tooth is

1.5 magnified. And I know that the dimension of the tooth on the radiograph by that

relation.


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Actual tooth length=

(Radiograph tooth length*actual instrument length)/radiograph instrument length

Children and handicapped patients:

Usually children are not cooperative, we need the help of parents, we need them to

hold their kids or we need the parents to stabilize the film holder with fingers, the dr

and the technician must not assist, only the parents.

If there is a problem with the holders we can put the film horizontally and we can do

modification to our technique.

Anatomical difficulties:

Large tongue, neck problem, narrows dental arch, shallow palate, and tight oral

muscles.

Edentulous alveolar ridge:

Areas with missing teeth, we put cotton rolls because we cannot stabilize the film

holders instead of teeth and in case of edentulous alveolar ridge we can do bisectingdimensions by putting cotton rolls above and below the holder

The end

Done by: Jumana Al-shawabke

Checked by: Sawsan Jwaied

Documents

Lec9_Intra Oral Radiographic Techniques