oral diagnosis radiation rotation manual

1

THE DISCOVERY OF X-RAYS ........................................................................... 4

ATOMIC STRUCTURE........................................................................................... 5

ORBITAL ELECTRONS: .............................................................................................. 5

ELECTROMAGNETIC RADIATION ............................................................... 6

PROPERTIES OF X-RAYS: .................................................................................................. 7

RADIATION BIOLOGY.......................................................................................... 8

RADIATION PROTECTION................................................................................. 9

MAXIMUM PERMISSIBLE DOSE: ..................................................................................... 10

DENTAL X-RAY MACHINE............................................................................... 12

X-RAY TUBE .................................................................................................................. 12 Separation of electrons ............................................................................................. 13 High voltage to impart speed to these electrons....................................................... 14 Focusing the electrons to a small area in the anode ................................................ 14 Sudden stoppage of electron stream by the anode.................................................... 14

FILTRATION: .................................................................................................................. 15 COLLIMATION:............................................................................................................... 16

FACTORS AFFECTING FILM QUALITY ................................................... 16

kVp: ........................................................................................................................... 16 Milliamperage (mA): ................................................................................................ 16 Time: ......................................................................................................................... 17 Filtration:.................................................................................................................. 17 Collimation: .............................................................................................................. 17 Distance: ................................................................................................................... 17

DENTAL X-RAY FILM.......................................................................................... 19

FILM COMPOSITION: ...................................................................................................... 20 Emulsion ................................................................................................................... 20 Base........................................................................................................................... 20

TYPES OF FILMS:............................................................................................................ 21 Periapical radiograph: ............................................................................................. 21 Bitewing radiograph:................................................................................................ 21 Occlusal radiograph:................................................................................................ 21

FILM PLACEMENT AND EXPOSURE.......................................................... 22

PARALLELING TECHNIQUE:............................................................................................ 22 BISECTING ANGLE TECHNIQUE:...................................................................................... 22 FILM HOLDING DEVICES:............................................................................................... 23

Anterior and posterior plastic biteblocks. ................................................................ 23 Indicator rod. ........................................................................................................... 23 Aiming ring. .............................................................................................................. 24

2

FILM PLACEMENT TECHNIQUE.................................................................. 25

PERIAPICALS ............................................................................................................. 25 Maxillary Central Incisor Periapical ....................................................................... 25 Maxillary Lateral Incisor Periapical........................................................................ 26 Maxillary Canine Periapical ................................................................................... 27 Maxillary Premolar Periapical................................................................................. 28 Maxillary Molar Periapical:..................................................................................... 29 Mandibular Incisors Perapical................................................................................. 30 Mandibular Canine Perapical:................................................................................. 31 Mandibular Premolar Periapical:............................................................................ 32 Mandibular Molar Periapical: ................................................................................. 33

BITEWINGS: ................................................................................................................... 34 Premolar Bitewing:................................................................................................... 34 Molar bitewing: ........................................................................................................ 35

RADIOGRAPHS FOR THE EDENTULOUS PATIENT............................................................. 36 UNIT OPERATION: .......................................................................................................... 36

PATIENT COMFORT DURING RADIOGRAPHIC PROCEDURES 37

FILM PROCESSING............................................................................................... 38

DARKROOM ................................................................................................................... 38 DEVELOPER: .................................................................................................................. 39 FIXER:............................................................................................................................ 39

MOUNTING PERIAPICALS AND BITEWINGS ....................................... 42

TECHNICAL ERRORS IN RADIORAPHIC PROCEDURES............... 44

PATIENT PREPARATION .................................................................................................. 44 FILM HANDLING ............................................................................................................. 44 FILM PLACEMENT........................................................................................................... 44 VERTICAL AND HORIZONTAL ANGULATION ................................................................... 44 EXPOSURE...................................................................................................................... 45 PROCESSING................................................................................................................... 45

DUPLICATING OF FILMS.................................................................................. 46

STEPS IN DUPLICATING .......................................................................................... 46 Adjusting time ........................................................................................................... 47 Labeling duplicates................................................................................................... 47

OCCLUSAL RADIOGRAPHS ............................................................................ 48

MAXILLARY OBLIQUE (TOPOGRAPHIC) OCCLUSAL: ...................................................... 48 MANDIBULAR OBLIQUE (TOPOGRAPHIC) OCCLUSAL:.................................................... 48 MANDIBULAR TRUE CROSS-SECTIONAL OCCLUSAL: ..................................................... 50

EXTRAORAL RADIOGRAPHS......................................................................... 51

DENTAL PANORAMIC RADIOGRAPHY.............................................................................. 51

3

LATERAL OBLIQUE OF MANDIBLE................................................................................... 51 LATERAL CEPHALOMETRIC PROJECTION ........................................................................ 52 POSTEROANTERIOR PROJECTION .................................................................................... 52

DEFINITION OF TERMS..................................................................................... 57

REFERENCES: ................................................................................................................. 59

4

THE DISCOVERY OF X-RAYS

Wilhelm Conrad Roentgen, a German physicist, discovered X-Rays on November 8, 1895.

Roentgen was studying the properties of cathode rays or electric current. Roentgen had placed a

cathode ray tube in a box in a dark room. The cathode tube was enclosed with heavy black paper

to block light from leaking. But to his amazement the a sheet of paper coated with a barium

platinocyanide, four feet away, glowed when the tube was switched on in the closed box. He

realized that an unknown kind of ray was being emitted from the tube and caused the paper to

glow. He called them x-rays (x for unknown). He tried to stop the rays by using different

substances and cast shadows of solid objects. When he held his hand between the tube and a

barium platinocyanide screen, he saw the bones of his hand. Wilhelm Roentgen received the first

Nobel Prize in physics in 1901.

X Rays transformed medicine because we were able to see the inside of a body without

performing surgery. Soon, x-rays became an important diagnostic tool for doctors and dentists

all over the world.

5

ATOMIC STRUCTURE

An atom is the fundamental unit of elements. Atoms are very minute and made up of

electrons, protons and neutrons. The atom has a nucleus in the center and electrons

revolve around the nucleus. The nucleus is made of neutrons and protons.

Electrons:

Electrons are negatively charged and have very little mass.

Neutrons:

Neutrons are neutral but weigh approx. 1840 times an electron.

Protons:

Protons are positively charged and weigh approx 1840 times an electron.

ORBITAL ELECTRONS:

Electrons are arranged in definite orbits, known as electron

shell, around the nucleus.

The innermost shell is the K shell, the next the l SHELL and

so on.

Only K and L shell are important in the production of x-rays

in dentistry.

The number of electrons is limited in each shell. K shell can have 2 electrons;

L shell can have a maximum of 8 electrons

and so forth. The outermost shell can not have more than 8 electrons.

In a neutral atom the number of electrons and protons are equal and so the net charge is

zero.

6

ELECTROMAGNETIC RADIATION

Radiation is a form of energy. Heat, light, sound and electricity are all forms of energy.

Electromagnetic radiation is a form of radiation energy, which has no mass and is

electrically neutral.

All electromagnetic radiation travel in waves at the speed of light. The basic difference

between types of electromagnetic radiation is their wavelengths and frequencies.

Wavelength is the distance from one crest of the wave to crest of the next wave.

Frequency is the number of oscillations per second.

Each form of electromagnetic radiation has a specific wavelength and frequency.

Electromagnetic radiations with longer wavelength have lower frequency and lower

energy. Radiations with shorter wavelength have higher frequency and higher energy.

Wavelengths are measured in Angstrom units (Å). Wavelengths used in dentistry are

about 0.1- 0.5 Å.

7

Properties of X-rays:

1. X-rays are weightless package of pure energy

2. They have no electrical charge

3. They travel at the speed of light

4. They travel in straight line but diverge from a central focus

5. They have enough energy to ionize and cause biological damage

6. They can cause certain substances to fluoresce and affect photographic film.

8

RADIATION BIOLOGY

X-rays are energy in transit. They can be considered as small packets of energy. X-rays

have enough energy to ionize an atom or molecule. Thus, it is know as ionizing

radiation. The deposition of energy may not cause ionization in all cases, but may only

excite the molecules. The most abundant molecule in our body is water. X-rays may

ionize or excite the water molecules and can block their normal function. These could

result in cell death or abnormal growth for these cells. The abnormal growth could lead

to tumor formation. The risks of such changes from diagnostic procedures in dental

radiology are very small. With proper shielding and adequate exposure principles the

harmful effects of x-rays can be minimized.

We are exposed to radiation constantly. Natural or background radiation is by far the

largest contributor (83%) to the radiation exposure of people living in the United States

Some of these are from outside the earth (extra-terrestrial) and are referred to as cosmic

radiation. There are also naturally occurring sources of radiation on earth referred to as

radioactive elements. They are present everywhere in small amounts, but also contribute

a lot to our background exposure.

Not every cell in our body responds the same to radiation. Cells which are dividing like

lymphocytes, gonadal cells are more prone to radiation-induced damage. Nerve cells are

more resistant to radiation-induced damage. Exposure to radiation has a cumulative effect

9

over a lifetime. Each time tissues are exposed to x-rays, some damage occurs. Tissues

have the capacity to repair some of the damage; however, the tissues do not return to their

original state.

RADIATION PROTECTION

Radiographs are needed for proper diagnosis. The principles of ALARA (as low as

reasonably achievable) should be followed to minimize radiation dose to both staff and

patients. The following steps will help keep the radiation dose to a minimum:

1. A radiograph should only be exposed on request from the dentist.

2. Use a fast film with minimum exposure

i. Proper collimation: The federal government requires that the x-ray beam

should be collimated so that the field of radiation at the patient's skin

surface is within in a circle having a diameter of no more than 2¾ inches

when the x-ray tube is operated above 50 kVp. Using a rectangular

collimation decreases patient skin exposure by 60% when compared with a

round collimation.

ii. Proper equipment:

The American Dental Association recommends that proper collimation,

filtration and extended source-patient distance (focal spot-to-film

distance) will reduce the amount of radiation to the patient.

Two standard focal spot-to-film distances are used years for use in dental

radiography:

a. 8 inches

b. 16 inches

X-ray tubes operating above 50 kVp, x-ray source-skin distance must not be less than 7

inches.

3. Adequate protection for both patient and staff

a. The patient must be protected. Lead aprons and thyroid collars must be

used regularly with every patient.

10

b. The staff must be standing behind a barrier when making an exposure.

c. If no barrier is available the operator can stand 6 feet from the patient, at

an angle of 90 to 135 degrees to the central ray of the x-ray beam when the

exposure is made.

d. The operator must never hold a film for the patient.

4. Proper exposure and processing should be used to minimize retakes

Maximum Permissible Dose:

There are four classes of people related to radiation exposure:

1. Occupationally exposed individual.

•Works with (or around) radiation.

•Has some knowledge of radiation hazard.

•Accepts the risk associated with it.

•2. The public.

•Exposed occasionally.

•Usually no knowledge of danger of radiation and risk.

3. Trainees under 18 years.

4. Embryo and fetus.

All the above groups have different recommendation by the ICRP

11

Type of exposure Dose

Occupational

Per calendar quarter 12.5 mSv

Per year 50 mSv

Non-occupational (Public)

Per year 5 mSv

Minors 1 mSv

Embryo/fetus 0.5 mSv per month

ALWAYS REMEMBER: Reducing the area of exposure reduces harm

Radiation dose from a dental examination is much less than background sources

Potential hazards exist with low doses of radiation in dentistry

Benefits to the patient from diagnosis far outweigh risk of cancer or mutation

Prudent and careful use of x-ray is needed for the safety of the patient and the

health-care provider.

ALWAYS FOLLOW THE PRINCIPLES OF ALARA

As Low As

Reasonably Achievable

12

DENTAL X-RAY MACHINE

The X-ray machine has two basic parts, the tubehead and the control panel.

• Tube Head: Contains the x-ray tube and the position-indicating device. The

tubehead is suspended from a flexible extension arm. The extension arm is

hollow to enable the wires to pass through. The arm also folds and allows

mobility and accessibility of the tubehead.

• Control Panel: Maybe a panel mounted on wall or a portable control box. This

is where the operator turns on the machine and can adjust the settings, kilovoltage

(kVp), milliamperage (mA) and time of exposure (seconds). The electric current

enters the control panel and continues to and through the extension arm to the

tubehead. Transformers are used to modify the voltage reaching the different parts

of the x-ray tube.

X-Ray tube

An x-ray tube is a glass bulb with vacuum inside it. The negative terminal of the

tube is the cathode and the positive part is the anode. The cathode is made of tungsten

filament and is heated to produce electrons. When a high voltage is applied between the

anode and the cathode the electrons move towards the anode. The anode is made of

13

copper with tungsten target, where the electrons hit the anode. The electrons are focused

on the tungsten target by means of a focusing cup, which is made of molybdenum.

The tube has metal housing and is surrounded with oil. The oil helps to insulate and

prevent sparking within the various electrical components

X-rays are produced when fast moving stream of electrons collide with the

tungsten anode. X-rays are produced when electrons moving at very high speed collide

with any matter (tungsten target). The kinetic energy of the electron is converted into x-

rays and heat. X-ray production is a rather inefficient process. More than 99% of electron

energy is converted into heat. Less than 1% of electron’s kinetic energy is converted into

x-rays..

Four conditions must exist for the production of x-rays.

Separation of electrons

a. The cathode is the source for electrons. It is made of tungsten

filament. The filament is heated at a low voltage (8-12 v) and

electrons are separated from the filament and form an electron cloud

around the filament.

14

High voltage to impart speed to these electrons

b. The cathode and the anode are connected with high voltage to move

electrons at a very high speed. The voltage is about 1000 times more

than what comes out from a 110-volt wall outlet. It may be 65,000 to

90,000 volts, or 65 to 90 kilovolts. 65 kilovolts is written as 65 kV or

kVp (kilovoltage peak)

Focusing the electrons to a small area in the anode

c. The electrons should strike a small region in the anode. The

molybdenum-focusing cup focuses the electrons to a small region in

the anode.

Sudden stoppage of electron stream by the anode

d. The anode is made of tungsten. Tungsten has a high atomic number

and a high melting point, but is not a good conductor of heat. More

than 99% of the electrons’ energy is transformed as heat, less than 1%

is converted into x-rays. We need a good thermal conductor to

dissipate the heat. So the tungsten target is embedded in copper stem.

The x-ray tube is a glass bulb with vacuum inside it. A metal housing surrounds the tube

and protects the tube from accidental damage and prevents overheating of the tube by

providing a space filled with oil.

15

Filtration:

The beam of x-rays exiting the tube has different wavelengths with different

energies. The x-ray beam can be thought of as being similar to a beam of white light,

which is made up of a mixture of different colors of light, each of which has a different

wavelength and energy level. Indeed, we even speak of both white light and x-ray beams

as being polychromatic (multicolored), meaning that they are mixtures of different

wavelength photons.

This mixture means that there are some photons that have considerably less energy than

others. The ones with less energy (and thus a longer wavelength) are less penetrating.

This means that they could not pass through the patient's cheek to get to the teeth, bones

and film. They only increase patient’s exposure to x-rays without contributing to the

production of a radiograph. To prevent this, we filter these low energy x rays out of the

beam, using a pure aluminum (Al) disk in the path of the beam as a filter.

So, we add a Aluminum disk, known as filter, to absorb this low energy x-rays.

The low energy x-rays cannot pass through the filter, but the higher energy one pass

through the filter and contribute in the formation of the radiograph.

The glass covering and oil in the tube contribute to stopping the low energy x rays and

are known as Inherent filtration

Total filtration is the thickness of Aluminum with the inherent filtration.

16

The law states that filters must be used to reduce patients dose..

At 50-70 kVp: at least 1.5 mm total filtration ( inherent + Al) must be used.

Above 70 kVp: at least 2.5 mm total filtration is required.

Collimation:

State law requires that collimator should restrict the beam diameter to no more than 7 cm

(2.75 inches) at the skin surface of the patient when making an intraoral dental

radiograph.

FACTORS AFFECTING FILM QUALITY kVp: The highest voltage of the current in the x-ray tube is called the kilovoltage peak (kVp).

Thus, if an x-ray machine is set at 70, 000 volts, the maximum x-ray energy that can be

produced during this exposure is 70 kVp. Depending on the model, the operator may be

able to adjust kVp setting. For every 15-kVp change the time of exposure must be

reduced by half or doubled accordingly to maintain film density. For example if you

change from 75 kVp to 90 kVp, the exposure time must be decreased by half. If you plan

to decrease the kVp by 15, you have to double the exposure time. At low kVp you get a

higher contrast. Some models have fixed kVp.

Milliamperage (mA): The ampere is the current in the x-ray tube. The higher the mA, the more the electrons in

the x-ray tube. The majority of dental x-ray machines operate in ranges of 7-15 mA.

Some x-ray machines have fixed mA. Other factors remaining the same, the more the

mA, the darker the film. If mA is doubled and other variables are not altered, the amount

of x rays produced will also double.

17

Time: All units should have a timer control that allows the operator to adjust the duration of

time that the x-rays are produced. These timer dials are either calibrated in seconds or

impulses. The electricity supplied to the dental offices in USA is alternating current

(AC) This means the current changes its direction of flow 60 times a second. X-rays are

only produced 60 times in an second. Each of these 60 times when x-rays are produce

corresponds to an impulse. So there are 60 impulses in 1 second, or 1 impulse is 1/60

second.

Just like mA, if time of exposure is doubled when all other factors remain the same, the

quantity of x-rays produced also doubles.

The milliamperage required for a given exposure time is inversely proportional to the

exposure time. The higher the mA, the shorter the exposure time .If a unit has a setting of

10 mA and 2 seconds and you need to change the mA you will have to change the time to

1 sec. The product of mA multiplied by time in seconds (mAs0 should remain constant

for a particular exposure.

10mA x 2 s = 20 mAs

20 mA x 1 s = 20 mAs

Filtration: As mentioned earlier filtration absorbs the low energy x-rays and reduced patient’s skin

dose.

Collimation: Restricts the beam size, so only useful part of the beam is directed on the patient.

Distance: If the distance from the x-ray tube increases the intensity of the x-ray beam decreases. X-ray beams are divergent and when they spread, their intensity per square distance decreases. The relationship between distance and intensity of radiation is called the

18

inverse square law because the intensity of radiation varies inversely as the square of the source-film distance.

19

DENTAL X-RAY FILM

Intra-oral x-ray film comes in different sizes and speeds. The currently available speeds

of x-ray films are D, E and F speed. E speed is twice as faster and thus needs half the

exposure to produce the same density. F speed is 25% more fasted than E-speed film and

requires further less exposure. The different sizes used are #0, # 1, #2, #3, and #4. Size 0

is the smallest, used in children. Size 1 is used for anterior teeth in adults. Size two films

are used for posterior bitewings and periapicals. Size three film is a special bitewing film

which is longer than size two. Size four is the largest used for occlusal radiograph. Film

size are chosen to fit the need of the particular area.

Each film has a white side, which is the tube side and faces the source of radiation. Some

packets contain double films. The film is surrounded by black paper and the, there is a

sheet of lead foil on the back side. The lead foil protects the film from backscatter

radiation.

Outer Cover: Protects the film from light and saliva from the patient’s mouth. The front

or white side should face the tube. The back side usually has an embossed dot in one

corner.

Paper Sleeve: The film is inside the paper sleeve. It protects the film from light.

20

Lead Foil: It protects the film from back-scatter radiation. If the film is placed backwards

you will get a lighter radiograph and sometimes you may be able to see the pattern of the

foil on the film.

Film Composition:

Film has a green color. The film has emulsion on both sides. There are two principal

components:

Emulsion Sensitive to X-rays and visible light and records radiographic image

The emulsion is made up of Silver halide grains mainly Silver bromide and Silver iodide

with trace amounts of sulfur-containing compd. and/or gold

Base Plastic supporting material on which the emulsion is coated with an adhesive. The base

is about 0.2 mm thick and is uniformly translucent. The base may have a slight blue tint

and must be able to withstand processing without getting distorted.

The outer layer is the protective coating that prevents the emulsion from being scratched

and damaged.

21

Types of Films:The various standard radiographs used in dental offices are:

Periapical radiograph: A periapical radiograph is used mainly to see the periapical region of the teeth. A good

periapical radiograph should reveal the entire root as well as at least 2 mm of bone apical

to the roots. This type of radiograph is used for:

To see the roots size, shape and number

Number and shape of root canals

Condition of periodontal membrane and bone

Lesions within bone

See impacted teeth

Bitewing radiograph: Bitewing radiographs are interproximal radiographs. These films reveal the crowns of

both maxillary and mandibular teeth in one radiograph. A good bitewing radiograph

should not have interproximal contacts. These films are used to reveal:

Interproximal caries

Caries around restorations

Bone height

Overhanging restorations

Crown fit

Occlusal radiograph: Occlusal radiographs are the largest intraoral films. The patient normally holds the film in

position by biting on them. They are used for:

To see a lesion, fractures, impacted teeth

Salivary duct stones

Rapid survey of edentulous jaws

In children, where periapicals cannot be taken, these occlusals are frequently

exposed with size 2 films.

22

Storage of Film: Films must be stored in a cool dry place as suggested by the

manufacturer. Be sure the check the expiry date.

FILM PLACEMENT AND EXPOSURE

There are two main procedures for exposing intra-oral periapicals:

Paralleling Technique: The paralleling technique is the most commonly used technique. This techniques requires

the film to be parallel to the long axis of the teeth to be radiographed. Sometimes this

requires the film to be placed deeper into the mouth away from the teeth. By, inverse

square law, this procedure requires greater exposure time than compared to bisecting

angle technique. The film is placed parallel to the teeth and the central ray is directed

perpendicular to the film and the teeth.

The film holders for this technique enable the film to be parallel to the teeth and the

central ray (PID) to be directed perpendicular to the film.

Bisecting angle technique: The film is placed at an angle to the long axis of the tooth. The central ray is directed 900

to an imaginary line that bisects the angle of the tooth and the film. This technique

usually does not require film holders. This technique results in some distortion of the

radiograph if the angle is not correct.

23

Film Holding Devices: Film-holding instruments such as the Dentsply/Rinn XCP instruments provide an external

guide for positioning of the tubehead vertically and horizontally as well as automatically

establishing the point of entry of the x-ray beam. Other devices such as Snap-a-ray or

Stabe disposable film holder have also been used.

The Dentsply/Rinn XCP instrument consists of three parts:

Anterior and posterior plastic biteblocks.

These are designed to retain the film

packet when the film is inserted.

Indicator rod.

These are made of stainless steel and are used to align the x-ray

cone or BID with the film. There is an anterior offset rod and a

posterior right angle rod designed to insert into the receptacle

24

holes of their respective biteblocks for the periapical projections.

Aiming ring.

Aiming rings are made for sliding onto the rods to establish

alignment of the cone with the film. This prevents cone cutting.

25

FILM PLACEMENT TECHNIQUE

PERIAPICALS

Maxillary Central Incisor Periapical

Film Selection: Size 0 or Size 1 Film.

Assemble the anterior instrument and insert the film vertically into the anterior biteblock

with the plain side of the film facing out (white towards the light) and embossed dot in

the slot

Film Placement: Center the film to the maxillary midline and parallel to the long axes of

the central incisors. The entire length of the biteblock should be used to position the film

back in the palate. The biteblock should be against the central incisors. Slide the aiming

ring down the indicator rod close to the patient.

Tubehead Placement: Align the tube with the indicator rod and aiming ring in both the

vertical and horizontal planes. Central ray directed between the central incisors.

Radiographic appearance: right and left central incisors with part of right and left

lateral incisors.

26

Maxillary Lateral Incisor Periapical




the slot

Film Placement: Center the lateral incisor on the biteblock and position the film parallel

to the long axis of the lateral incisor . Position the film away from the teeth. The

biteblock should be against the lateral incisors. Slide the aiming ring down the indicator

rod close to the patient.


vertical and horizontal planes. Central ray directed at the center of the lateral incisor. (the

central-lateral contact should be open).

Radiographic appearance: Lateral incisor should be centered on the film.

27

Maxillary Canine Periapical




the slot

Film Placement: Film centered behind the lateral incisor and canine interproximal space.

Slide the aiming ring down the indicator rod close to the patient.


vertical and horizontal planes. Central ray directed through the lateral incisor and canine

interproximal space. (The lateral incisor-canine contact should be open). The overlapped

canine-premolar contact will be opened in the premolar periapical. Alternatively of the

film is centered behind the canine and first premolar, the canine-premolar contact will be

open.

Radiographic appearance: Canine should be centered on the film.

28

Maxillary Premolar Periapical

Film Selection: Size 2 film

Assemble the posterior periapical instrument and insert the film horizontally into the

posterior biteblock with the plain side facing out ( white towards the light) and the dot in

the slot..

Film Placement: Position the film-holder in the mouth with the second premolar

centered on the film. The distal of the canine must be seen on this projection. Parallel the

film horizontally with the upper edge of film at or across the midline of the palate.

Tubehead Placement: Slide the aiming ring or locator ring down the indicator rod to

approximate the skin surface. Align the tube with both the indicator rod and aiming ring

in both the horizontal and vertical planes. Central ray is directed parallel to the second

premolar-1st molar interproximal space.

Radiographic appearance: Distal half of canine, first premolar, second premolar, first

molar and part of second molar.

29

Maxillary Molar Periapical:



posterior biteblock with the plain side facing out (white towards the light) and the dot in

the slot.

Film Placement: Position the film-holder in the mouth with the anterior edge of the film

at the middle of the second premolar. If necessary, move the film posteriorly to cover the

maxillary third molar even if the third molar is not visible. Parallel the film horizontally

with the upper edge of film at or across the midline of the palate.



in both the horizontal and vertical planes. Central ray is directed parallel to the 1st molar-

2nd molar interproximal space.

Radiographic appearance: Half of 2nd premolar, entire 1st, 2nd and 3rd molars. The

interproximal space between the 1st and 2nd molar should be open.

30

Mandibular Incisors Perapical




the slot

Film Placement: Center the film directly behind the two central incisors. Slide the

aiming ring down the indicator rod close to the patient.


vertical and horizontal planes. Central ray directed between the central incisors.

Radiographic appearance: Right and left central incisors and right and left lateral

incisors.

In some cases one may need to take separate lateral incisor periapicals with the film

centered on the lateral incisors.

31

Mandibular Canine Perapical:




the slot

Film Placement: Center the film directly behind the mandibular canine. Slide the aiming

ring down the indicator rod close to the patient.


vertical and horizontal planes. Central ray directed perpendicular to the canine.

Radiographic appearance: Lateral Incisor, canine and 1st premolar. Both mesial and

distal contacts to the canine should be open.

32

Mandibular Premolar Periapical:




the slot.

Film Placement: Position the film-holder in the mouth with the second premolar

centered on the film. The distal of the canine must be seen on this projection. Parallel the

film horizontally to the lingual surface of mandibular teeth.



in both the horizontal and vertical planes. Central ray is directed parallel to the second

premolar-1st molar interproximal space.


molar and part of second molar. The 2nd premolar –1st molar interproximal space should

be open.

33

Mandibular Molar Periapical:




the slot.

Film Placement: Position the film-holder in the mouth with the anterior edge of the film

at the middle of the second premolar. If necessary, move the film posteriorly to cover the

mandibular third molar region even if the third molar is not visible. Position the film

parallel to the lingual surface of mandibular teeth.



in both the horizontal and vertical planes. Central ray is directed parallel to the 1st molar-

2nd molar interproximal space.

Radiographic appearance: Half of 2nd premolar, entire 1st, 2nd and 3rd molars. The

interproximal space between the 1st and 2nd molar should be open.

34

Bitewings:

Premolar Bitewing:

Film selection: Size 2 film. Position the film horizontally (for horizontal bitewings) or

vertical (for vertical bitewings). The white surface of the film should face the tube.

Film Placement: Place the film against the occlusal surface of mandibular teeth and

should include the distal half of mandibular canine. (Imagine a line drawn on the occlusal

surface from the mesial side of the cuspid to the mesial side of the first molar. The film

should be parallel to this imaginary line).

Tubehead Placement: Slide the aiming ring down the indicator rod to approximate the

skin surface. Align the tube with the indicator rod and aiming ring in both the horizontal

and vertical planes. Central ray is directed perpendicular to 2nd premola-1st molar

interproximal space.


molar and part of second molar.

35

Molar bitewing:

Film selection: Size 2 films. Position the film horizontally (for horizontal bitewings) or

vertical (for vertical bitewings). The white surface of the film should face the tube.

Film Placement: Place the film behind the mandibular molars so that the posterior edge

includes the distal surface of the last erupted molar in either arch. Position the film

perpendicular to the proximal spaces of the molars. (Imagine a line drawn from the

occlusal surface from the mesial side of the first molar to the distal side of the last

erupted molar. The film should be parallel to that line).

Tubehead Placement: Slide the aiming ring down the indicator rod to approximate the

skin surface. Align the tube with the indicator rod and aiming ring in both the horizontal

and vertical planes. Central ray is directed perpendicular to 1st molar-2nd molar

interproximal space.

Radiographic appearance: Equal portions on both arches. The last erupted teeth should

be included in this radiograph.

36

Radiographs for the Edentulous Patient

Radiographs are necessary in edentulous patients. The edentulous areas may contain

roots, impacted teeth, or other pathology. A panoramic film will reveal the maxillary and

mandibular bone. If panoramic machine is not available, an examination consisting of 14

intraoral films will provide the necessary information. Placement of intraoral films is

difficult in edentulous regions. To overcome this problem, cotton rolls are placed

between the ridge and the film holder.

Unit operation:

1. Turn the unit on. When the unit is ready a light will come on in most units.

2. Check and adjust the exposure factors: kVp, mA and time.

3. Prepare the patient. Remove any eyeglasses, removable dentures and place lead

apron and thyroid collar.

4. Place the film in the patient’s mouth and place the PID in the proper position.

5. Depress the exposure button and hold until the audible tone stops.

6. Remove the film from the patient’s mouth.

7. Turn off the machine between uses, if machines are in an unattended area.

8. The film is now ready to be processed.

37

PATIENT COMFORT DURING RADIOGRAPHIC PROCEDURES

For many patients exposing radiographs is uncomfortable. Certain steps must be taken to

minimize patient discomfort and maximize patient co-operation.

• Always set the timer before film placement so the patient does not have to wait

with the film in his/her mouth while you adjust the exposure time.

• First start with the anterior films. These films are the least likely to induce gag

reflex in the patient. This also helps the patient to get used to the technique and

increases patient co-operation.

• Use cotton rolls and edge-ease to increase comfort during radiographic

procedures.

• Skillful placement of the film reduces patient gagging. However, if it is a problem

ask the patient to take deep breaths through his/her nose while you place the film.

Any kind of distraction, like talking, asking patient to count their breaths, will

reduce the gag reflux.

38

FILM PROCESSING

After the film is exposed, the film is ready to be processed. Film processing produces a

visible image. Processing, consists of: developing, fixing, washing, and drying.

Processing is performed in a darkroom, unless an automatic processor with a daylight

loader is used.

Darkroom

The darkroom should be proper, well-ventilated and clean. It is necessary to keep

safelight illumination (wattage of bulb) and film handling times under the safelights at a

minimum time and should not exceed 8 minutes. The Kodak Safelight filter GBX-2 (red)

filter can be used in darkrooms in for both intraoral and extraoral films. ML-2 (light

orange) filters should be used only for intraoral dental film and never for panoramic film.

The safelight should be at least 4 feet above the processor.

The darkroom must not have any light leaks. To check this, close the door and turn off all

lights including the safelight and allow 5-7 min for your eyes to adapt to the dark. Then,

check for any light leak. If there is any doubt, do the following test. Remove a film from

its packet and place it on the workbench in the darkroom. Put a coin (penny) on top of

the film. Keep it for 5 min and then process the film. If you can see the image of the coin

in the film you have a problem with light leak or the filter.

39

Developer:

The developing solution consists of

1. Phenidone or Metol: fast developing agent. Quickly builds up contrast. It

reduces exposed silver bromide to metallic silver.

2. Hydoquinone: Slow developing agent.

3. Sodium sulfite: Preservative. It prevents oxidation of the developer.

4. Sodium carbonate: Activator. Removes the bromide from the solution and

speeds up the developing process. It also maintains the pH of the developing

solution alkali. It also softens the emulsion to allow the chemicals to penetrate

the film.

5. Potassium bromide: Restrainer. Acts to balance the action of sodium

carbonate.

6. Water: Dissolves the above components and acts as a solvent.

Wash:

In automatic processors, there is no wash because the rollers squeeze the developer out.

In manual processing, wash is recommended for 30 secs to stop the developer action and

to remover the developer.

Fixer:

1. Sodium thiosulfite: Also known as hypo, removes all silver bromide left on the

film. If the unreduced silver bromide were not removed, the film would be

cloudy.

2. Acetic acid or sulphuric acid Neutralizes any developer that might have been

carries over and maintains an acidic pH.

3. Alum hardens and shrinks the gelatin of the emulsion.

4. Sodium sulfite: Preservative (as in developer)

5. Water: Dissolves the above chemicals.

40

Wash:

After fixing, the film is washed in running water to remove all the fixer. If the fixer

remains on the film, there will be discoloration of the film over time.

For manual processing, hang the film in the hangers. Label the hangers. The lead foil

from the film packet should be saved for recycling. In solutions the film must be agitated

by moving it up and down to remove any bubbles. The temperature of all solutions

should be around 680F. The ideal time for the film to be processed is:

Developing: 5 min

Wash: 30 sec

Fixing: 10 min (usually twice the developing time)

Wash: 20 min

Dry the film until it is completely dry.

After the films are dry, they can be mounted.

41

An unexposed film has silver halide crystals. After exposure the crystal where the x-rays

or light hit the film have precipitation of silver. This is the formation of the latent image.

Developing the film amplifies the precipitation of silver from silver halide crystals

leading to the formation of visible image. Fixer removes the unexposed silver halide

crystals from the film.

Automatic processing: Manufacturer’s directions must be followed to ensure proper

film development. Proper maintenance of the processor is important and includes

cleaning and replenishing of solutions.

42

MOUNTING PERIAPICALS AND BITEWINGS

In order to view radiographs in a systematic way, we need to mount the radiographs after

processing. They are placed in special holders known as mounts. The mount should

always be labeled with the patient's name and the date the radiographs were exposed.

Errors in mounting can lead to errors in diagnosis and dental treatment of the patient.

The American Dental Association recommends that films be positioned in the mount in a

way that it appears as if you were looking at the patient. The following guidelines must

be followed while mounting:

A. The raised portion of the embossed dot on the film must face the viewer.

B. The teeth should appear in proper order.

The first step in organizing the radiographs, be they of a complete mouth survey, a set of

bitewings, or any other combination of radiographs, is to have a view box on which to

sort them. Handle the radiographs only on the edges.

1. Turn all the radiographs so that the convex (bump) side of the embossed dot is up.

Place all the films onto the view box, placing the dimple facing upwards.

2. Separate the size two films from the size zero films. Set aside the size zero films.

3. Now separate the bitewings from the periapicals in the size 2 films.

4. If you were consistent in placing the bump towards a particular arch when

exposing the bitewings, this is when it comes in handy. Place the bitewings so

that the premolar bitewings are mesial, the molar bitewings are distal. When the

bitewings are correctly exposed and mounted, you should see a slight “smile” in

43

the small radiolucent area between the maxillary and mandibular arches. This

would coincide with the upward curve of the mandible.

5. Remember!! Mounting radiographs is putting a puzzle back together. Know

your anatomy!! Place teeth that are mesial towards the middle of the view

box/mount, teeth that are distal towards the outside edges of the view box/mount.

6. Once you have correctly arranged the bitewings, you should have a view of all the

posterior teeth. Again, knowing your anatomy, separate the maxillary from

mandibular films, remembering that mandibular molars have two very distinct

(mesial and distal) roots. You will see the maxillary sinus areas. Place the films

on the correct side of the view box, keeping the premolars mesial and the molars

distal.

The premolar radiograph should show the distal half of the canine on the mesial

edge of the film. The molar radiograph should have the second molar centered on

the film.

7. Take the size zero films and separate maxillary from mandibular films.

Remember that the maxillary teeth are larger and usually have longer roots. The

maxillary central radiograph should show the two max centrals with the midline

on the center of the film, with only with a little of the mesial portion of each

lateral on the outside edges of the film. The lateral radiograph should show the

lateral in the center, the distal of the central on the mesial edge of the films and

the mesial of the canine on the distal edge of the film. The canine radiograph

should show the canine on the center with the distal of the lateral on the mesial

edge of the film and the mesial of the 1st premolar on the distal edge of the film.

8. Mandibular anterior teeth are smaller. On the central radiograph, you should see

all 4 incisors, with the very edge of the mesial aspect of the canines on the outside

edges of the film. The lateral radiograph should have the lateral on the center

with the centrals on the mesial edge and the canine on the distal edge of the film.

The canine radiograph should have the canine on the center, with the lateral on

the mesial edge and the 1st premolar on the distal edge.

9. The films can now be inserted into the mount.

44

Make sure you legibly write the patient’s name, chart number and date of

exposure on the mount.

TECHNICAL ERRORS IN RADIORAPHIC PROCEDURES

Patient preparation

a. Failure to remove eyeglasses: White shadow on the film

b. Failure to remove removable dentures: White image on the film

c. Other radiopaque objects between source and film (hair-pins and

necklaces for panoramic films): White image on the film

Film handling

d. Excessive bending, folding of film: Dark lines on the edge of the film.

e. Exposure to light or scatter radiation: Film gets darker. Always place the

film outside the room while taking radiographs.

Film placement

f. Film placed backwards: Films will be light. The pattern of the lead foil

(Tire track) will be visible on the film.

g. Film placed too apically or occlusally: Crowns of the teeth will not be

visible when films are placed apically. If films are placed too far

occlusally (when the patients do not bite down enough) the apices of the

teeth will not be visible on the radiograph.

h. Film movement during exposure: The film will appear blurry

Vertical and Horizontal angulation

i. Incorrect vertical angulation: Image foreshortened or elongated

j. Incorrect horizontal angulation: Overlapping of teeth

45

Exposure

k. Overexposure : Dark films

l. Underexposure: Light films

m. Double exposure: Dark films with two images overlapping.

n. Patient movement during exposure: Films will be blurry

Processing

o. Paper stuck to film: That region will not be processed and appear dark.

p. Finger prints: Always wear powder free gloves while processing

radiographs.

q. Static electricity: Lighting like streaks on the film. Usually seen in

winters when the heat is on. A humidifier in the processing room will

minimize this problem.

r. Film exposed too long to safelight: Dark film

s. Overlapping of two films while processing: Dark region where the films

have overlapped and thus that region was unable to be processed. In an

automatic processor feed the film slowly, making sure that they do not

overlap.

t. Overdevelopment: Dark film

u. Underdevelopment: Light film

v. Inadequate washing: Fixer will remain on the film. This film will turn

brown over time.

46

DUPLICATING OF FILMS

Sometimes it is necessary to duplicate a film. Duplicating films are different from x-ray

films since they have emulsion only on one side. The dark side of the duplicating film is

usually the side with no emulsion and the gray or lavender side has the emulsion.

Duplicating films are sensitive to light and so duplication must be turn in the darkroom

with the red safelight.

STEPS IN DUPLICATING

1. Place original radiograph on the glass of the duplicating machine.

2. Place duplicating film on top. The dark side should be on top and the gray side

touching the original radiograph.

3. Close and lock the cover after placing duplicating film. Lift the locks over the cover

and then press them down tightly

4. Turn timer to desired time (suggested time is 10 seconds for FMS and 5 seconds for a

panoramic radiograph). If red light in the duplicating machine is on, turn it off.

Otherwise machine will not duplicate. Then, press the white bottom on the timer for

duplicating to begin.

5. Wait for duplicating to finish. When this happens, you will hear a click.

6. When done, open duplicating machine and put film through processing machine.

47

Adjusting time

• Duplicating film is the opposite of radiographic film. Therefore, if original film is

light, decrease the time of duplication. If the original film is dark increase time.

• It is suggested to time FMS at 10 seconds and Panoramic at 5 seconds. However, this

may have to be adjusted depending on the quality of the original radiograph.

Labeling duplicates

• Be sure to place label on the correct side of the duplicate. Compare the duplicate to

original. Include the patient’s name, the original exposure date, and the record

number in the label.

48

OCCLUSAL RADIOGRAPHS

Maxillary Oblique (Topographic) Occlusal:

Patient Position: Occlusal surface parallel to floor

Central ray directed at 65o through the bridge of the nose

Provides broad area of coverage as well as a right angle view to periapical projections.

Mandibular Oblique (Topographic) Occlusal:

49

Patient positioned with occlusal plane 45o above floor.

Central ray directed at –55o to the film

Can be substituted for periapicals in children.

50

Mandibular True Cross-sectional Occlusal:

Patient positioned with occlusal plane perpendicular to film

Central ray directed 90o to film

Provides true right angled view to periapical projection

51

EXTRAORAL RADIOGRAPHS

Dental panoramic radiography

A panoramic radiograph shows both the maxilla and the mandible on a single film. The

X-ray tube and the film rotate around the patient's head. The advantages of panoramic

images are

(1) Broad coverage of the facial bones and teeth.

(2) Low patient radiation dose.

(3) Easy for the patient

(4) Can be used inpatients who cannot open their mouth

(5) Can be taken in a short time.

Lateral oblique of mandible

This projection demonstrates one side of the body and ramus of the mandible, together

with part of the maxilla. The film is positioned against the upper and lower jaws, on the

side to be examined, the head being turned to bring the area of interest parallel to the

film. The X-ray tube is centered just below and posterior to the angle of the mandible of

the opposite side and the central ray passes between the ramus of the mandible and the

cervical spine to the appropriate part of the mandible on the opposite side.

52

Lateral cephalometric projection

These films are used for the assessment of facial growth, and the planning of orthodontic

treatment. The patient's head is located in a specially designed holder. The film holder

and the X-ray tube are placed at a fixed distance. A wedge filter is placed over the

anterior side of the beam at the tube head so that the soft tissues of the facial profile may

also be seen

Posteroanterior projection

In this projection the x-ray beam passes in a posterior-to-anterior direction through the

head. The patient is positioned in the specially designed holder and the central ray is

directed perpendicular to the plane of the film at the level of the bridge of the nose.

57

DEFINITION OF TERMS

Absorbed dose: The amount of energy imparted by ionizing radiation per

unit mass of irradiated matter

ALARA: (acronym for As Low As Reasonably Achievable) making

every reasonable effort to maintain exposures to radiation

to a minimum.

Anode: The positive electrode of an X-ray tube. In an X-ray tube,

the anode carries the target

Atom: smallest particle of an element that is capable of entering

into a chemical reaction.

Bitewing: a radiograph made specifically to show the crowns of teeth

and crest of alveolar processes in both the maxilla and

mandible.

Cassette: A rigid or flexible light-tight container for holding

radiographic film with or without intensifying screens,

during exposure.

Cathode: The negative electrode of an X-ray tube.

Collimator: a lead restricting device that limits the size of the x-ray

beam, to an area on the skin to a diameter of 2.75 inch or

less.

Contrast: the difference between the white and the black of a film

Cumulative: an accumulating or building up effect.

Definition: the sharpness or delineation of the edges of the images on

the radiograph.

Density: the overall blackness of a radiograph.

Film processing: The operations necessary to transform the latent image on

the film into a permanent, visible image, consisting

normally of developing, fixing, washing and drying a film.

58

Film speed: the sensitivity of a film to radiation

Fixing: the chemical removal of silver halides after development.

Focal spot: The X-ray emitting area on the anode of the X-ray tube

gray (Gy): the new international system (SI) unit for measuring

absorbed dose. The old unit was the rad. 1 Gy = 100 rads

Inherent filtration: The reduction of low energy of a radiation beam by the

parts of the X-ray tube.

Intensifying screen: A material used in radiographic production to converts a

part of the ionizing radiation into light and reduces the

exposure time required to produce a radiograph.

Inverse Square Law the intensity of radiation at any distance from a point

source varies inversely as the square of that distance.

Ionization: the production of ion pairs by the removal of electrons

from atoms, giving negative (electrons) and positive (the

nucleus and remaining electrons) products.

Ionizing radiation: those forms of radiation, such as x or gamma rays, and

alpha or beta particles, that interact with matter by

producing ions.

Irradiation: the exposure of matter to radiation.

Lead apron: a protective drape that can absorb radiation.

Leakage radiation: radiation that originates from the X-ray tube assembly

other than via the useful beam.

MPD: maximum permissible dose.

Member of the Public: an individual in a controlled or unrestricted area (who is

not a radiation worker). However, an individual is not a

member of the public during any period in which the

individual receives an occupational dose.

Minor: an individual less than 18 years of age, as pertains to

radiation exposure limits, works with radioactive materials

(not a member of the general public).

Mutation: any heritable alteration in the genes of an organism.

59

Occlusal: the biting surfaces a tooth or series of teeth.

Occlusal radiograph: A type of radiograph that is made with the film lying on the

occlusal surfaces of the teeth of one arch.

Occupational Dose: the dose received by an individual in the course of

employment in which the individual's assigned duties

involves exposure to radiation.

Periapical: the area around the apex of the teeth

Periapical radiograph: a radiograph made specifically to show the area around the

apex of teeth.

Primary radiation: Radiation that travels along a straight line, without scatter,

from the source to the detector.

Rad: a unit of absorbed x-ray dose. Radiation absorbed dose.

This unit has been officially replaced in the international

system by the gray (Gy). 100 rads = 1 Gy .

Radiograph: A visible image after processing produced by a beam of

penetrating radiation on a radiographic film

Scattered radiation: radiation that has undergone a change in direction during

its passage through matter.

Source: the focal spot or target of the x-ray tube

Source-to-film distance (sfd): The distance between the source of radiation and the film

along the path of the beam of radiation.

Tubehead: the part of the x-ray unit that contains the x-ray tube, the

radiation-producing element of the unit.

References: American dental association, US Food and Drug Administration: The Selection of

Patients for Dental Radiographic Examinations (2004)

60

American Dental Association. Recommendations in radiographic practices, 1988. JADA

118:7115-117, 1984.

Langland Olaf E, Langlais Robert P., Preece John W, Principles of Dental Imaging 2nd

edition.

White Stuart C, Pharoah Michael J.; Oral Radiology Principles and Interpretation 4th

edition.

From : Langland: Principles of Dental Imaging: Olaf E. Langland, Robert P. Langlais,

John W. Preece; 2nd edition: Fig 9.21, table 10-1 and 10-2 .

oral diagnosis radiation rotation manual

Documents