Radiographic Techniques in Pediatric Dentistry - Part Two.......

Radiographic Techniques
in Pediatric Dentistry
Presented by Dr Simran Vangani 1

EXTRAORAL RADIOGRAPHIC TECHNIQUES
 These techniques imply that the film is placed outside the oral cavity, against the side of the face to be
radiographed and the X-ray beam is directed towards it
INDICATIONS-
 When it is not possible to place the film intraorally as during trismus
 To examine the extent of large lesions, especially when the area of pathology is greater than which can be covered by an intraoral
periapical film
 When jaws or other facial bones have to be examined for evidence of disease lesions and other pathological conditions
 To evaluate skeletal growth and development
 To evaluate the status of impacted teeth
 To evaluate trauma
 To evaluate temporomandibular joint area
2

DRAWBACKS
 Magnification occurs due to the greater object to film distance used
 Details are not well-defined due to the use of cassettes and intensifying screens.
 Contrast is reduced as the secondary radiation produced by the soft tissues is more.
 An important aspect of the extraoral radiography techniques is the immobilization of the
patient’s head. This is achieved by the use of various devices like, compression bands,
head clamps, craniostat.
3

1. Glabellomeatal line
2. Orbitomeatal line
3. Inframeatal line
4. Acanthomeatal line
4

Most of the techniques for skull radiography
use a film focus distance of approximately
three feet (90 cm), in cephalometry a
distance of five to six feet (150–180 cm) is
used.
5

 Structures Shown-This angulation will cause the petrous ridges to
be superimposed on the maxillary sinuses, thus allowing more
accurate examination of the orbits and ethmoidal air cells.
 Film Placement-The cassette is placed perpendicular to the floor
in a cassette holding device. The long-axis of the cassette is
positioned vertically.
 Position of Patient-The midsagittal plane is vertical and
perpendicular to the cassette. Only the forehead and nose touch
the cassette, so that the canthomeatal line is perpendicular to the
cassette. On the resultant radiograph the superior border of the
petrous ridge is projected in the lower third of the orbit.
 Central Ray-Is directed 23° to the canthomeatal line, entering the
skull about 3 cm above the external occipital protuberance and
exiting at the glabella.
 Exposure Parameters-
Using extraoral machine
• kVp—70–80
• mA—60–50,
seconds—1.6 (Bucky grid) 6

 Structures Shown-This projection is primarily used to demonstrate the maxillary
sinus, frontal and ethmoidal sinuses. The sphenoidal sinuses can be seen if the
patient is asked to open his mouth, whereby the sphenoidal sinuses are projected
on the palate
 Film Placement-The cassette is placed perpendicular to the floor in a cassette
holding device. The long-axis of the cassette is positioned vertically
 Position of Patient-The midsagittal plane should be vertical and perpendicular to
the plane of the film. The patient’s head is extended so that only the chin touches
the cassette. The cassette is centered around the acanthion (anterior nasal spine).
The canthomeatal line should be at 37° to the plane of the film and the line from
the external auditory meatus to the mental protuberance should be perpendicular
to the film. In this position the aim is to extend the patient’s head just enough so as
to place the dense shadows of the petrosae immediately below the antral floors.
 An easy visual method is that a line extending from the external auditory meatus to
the mental protuberance of the chin should be perpendicular to the cassette.
 Central ray -is directed perpendicular and to the mid point of the film. It enters
from the vertex and exists from the acanthion 7

 A posteroanterior (PA) projection of the
mandibular body and the ramus. The symphysis
region is not well seen because of the
superimposition of the spine. It is used to study
fractures of the posterior third of the body of
the mandible, angles, rami and lower condylar
necks, mediolateral expansion of the posterior
third of the body or the rami in case of tumors
or cystic lesions, maxillofacial deformities and
mandibular hypoplasia or hyperplasia.
 The cassette is placed perpendicular to the floor
in a cassette holding device. The long-axis of the
cassette is positioned vertically.
 The sagittal plane should be vertical and
perpendicular to the film. The head is tipped
downwards so that the forehead and nose touch
the film. The radiographic base line is horizontal
and perpendicular to the film. The film is
adjusted so that the lips are centered to the
film.
 Central Ray Is directed at right angles to the film
through the midsagittal plane through the
cervical spine, at the level of the angles of the
mandible. 8

 This projection is used to show the tissues of
one side of the face and used to investigate
the parotid gland and the ramus of the
mandible.
 Film Placement -The cassette is placed
perpendicular to the floor in a cassette
holding device. The long-axis of the cassette is
positioned vertically.
 The patient is positioned facing the film, with
the occlusal plane horizontal and the tip of
the nose touching the film. The head is
rotated 10° to the side of interest. This rotates
the bones of the back of the skull away from
the side of the face under investigation.
 Central Ray -It is directed at right angles to the
film, aimed down the side of the face which is
of interest.
9

 Structures Shown -Anterior body of the mandible, position of the teeth in the
same area. Helps to evaluate impacted teeth, fractures and lesions located in
the anterior portion of the mandible.
 The cassette is placed flat against the patient’s cheek and is centered over the
body of the mandible, overlying the canine teeth. The patient must hold the
cassette in position with the thumb placed under the edge of the cassette
and the palm against the outer surface of the cassette.
 Position of Patient –
The patient’s head is so adjusted, that the ala tragus line is parallel to the floor.
The mandible is protruded slightly to separate it from the vertebral column. The
cassette is placed over the patient’s cheek and centered over the area of
interest. The inferior border of the cassette should be parallel to the lower
border of the mandible and below it. The sagittal plane is tilted so that it is 5° to
the vertical, and rotated 30° from the true lateral position. For the bicuspid and
incisor region, the patient’s head should be turned slightly away from the tube
so that the nose and chin approximate the cassette.
 Central Ray- Is directed from 2 cm below the angle of the mandible opposite
to the side of interest. The beam is directed upward (–10° to –15°) and
centered on the anterior body of the mandible. The beam must be directed
perpendicular to the horizontal plane of the film
Exposure Parameters
10

 Structures Shown- Body of the mandible, position of the teeth in the same area, ramus of the
mandible, angle of the mandible. Helps to evaluate impacted teeth, fractures and lesions located in
the posterior border of the mandible.
 Film Placement- The cassette is placed flat against the patient’s cheek and is centered over the body
of the mandible. The cassette also should be positioned parallel to the body of the mandible. The
patient must hold the cassette in position with the thumb placed under the edge of the cassette and
the palm against the outer surface of the cassette.
 Position of Patient
 The patient’s head is so adjusted, that the ala tragus line is parallel to the floor. The mandible is
protruded slightly to separate it from the vertebral column. The cassette is placed over the patient’s
cheek and centered over the area of interest. The inferior border of the cassette should be parallel
to the lower border of the mandible and below it. The sagittal plane is tilted so that it is 5° to the
vertical andtheheadis rotated10°to 15°fromthe true lateralposition. For the molar and ramus region,
the head should not be turned away from the tube as this will place the ramus behind the vertebral
column.
 Central Ray- Is directed from 2 cm below the angle of the mandible opposite to the side of interest.
The beam is directed upward (–10° to –15°) and centered on the body of the mandible. The beam
must be directed perpendicular to the horizontal plane of the film.
 Using intraoral X-ray machine
 kVp—65–70
 mA—7–10, seconds—0.8
 Using extraoral X-ray machine
 kVp—40
 mA—40, seconds—1.
12

 Structures Shown- The purpose of this view is to evaluate impacted third molars, large
lesions, fractures that extend into the ramus of the mandible. This projection
demonstrates a view of the ramus from the angle of the mandible to the condyles.
 Film Placement The cassette is placed flat against the patient’s cheek and is centered
over the ramus of the mandible. The cassette also should be positioned parallel to the
ramus of the mandible.
 Position of Patient- The patient’s head is so adjusted, that the ala tragus line is parallel to
the floor. The mandible is protruded slightly to separate it from the vertebral column.
The cassette is placed over the patient’s cheek and centered over the area of interest.
The inferior border of the cassette should be parallel to the lower border of the mandible
and below it. The sagittal plane is tilted so that it is 10° to the vertical and the head is
rotated 5° from the true lateral position
 Central Ray- Is directed from 2 cm below the angle of the mandible opposite to the side
of interest, to a point posterior to the third molar region on the side opposite the
cassette. The beam is directed upward (–10° to –15°) and centered on the ramus of the
mandible. The beam must be directed perpendicular to the horizontal plane of the film.
14

 A full axial view of the base of the cranium showing a
symmetrical projection of the petrosa, the mastoid process,
foramen ovale, spinosum canals, carotid canals, sphenoidal
sinuses, mandible, maxillary sinus, nasal septum, odontoid
process of the atlas and the entire atlas, axial inclination of the
mandibular condyles. Helps to study destructive/expansile lesions
affecting the palate, pterygoid region or base of the skull,
sphenoidal sinus.
 Film Placement -The cassette is placed perpendicular to the floor
placed vertically
 Position of Patient -The head is centered on the cassette, with
the patient’s head and neck tipped back as far as possible, the
vertex (top) of the skull touches the cassette. Both the
midsagittal plane should be perpendicular to the plane of the film
and the radiographic base line should be parallel to the film.
 Central Ray- Is directed perpendicular to the film and through the
midsagittal plane, between the angles of the mandible,
perpendicular to an imaginary line joining the mandibular 1st
molars (approximately 1 inch from the chin).
15

 Structures Shown A symmetrical axial view of the zygomatic
arches.
 Film Position Same as that in submentovertex.
 Position of Patient Same as that in submentovertex
 Central Ray- The cone is brought as close as possible to the
patient (which leads to magnification of the structures at the
base of the skull).
 Exposure Parameters
The exposure time for the zygomatic arch is reduced to
approximately one-third the normal exposure time for a
submentovertex projection
17

 This technique is most useful in detecting arthritic changes on the articular surface.
It helps to evaluate the joint’s bony relationship. Changes on the central and medial
surfaces are not seen
 Film Position-The cassette is placed flat against the patient’s ear and centered over
the TM joint of interest, against the facial skin parallel to the sagittal plane
 Position of Patient- The patient’s head is adjusted so that the sagittal plane is
vertical. The ala tragus line is parallel to the floor
18

 Transcranial view mouth closed position
21

 Transcranial view mouth open position
22

 This view is a lateral projection showing medial surface of the condylar head and neck,
usually taken in the mouth open position, so that the joint is projected into the shadow of air
containing spaces of the nasopharynx, which helps to increase the contrast of the various
parts of the joint.
 Film Placement- The cassette is placed flat against the patient’s ear and is centered to a
point ½˝ anterior to the external auditory meatus, over the TM joint of interest, against the
facial skin parallel to the sagittal plane.
 Position of Patient –
The patient is positioned so that the sagittal plane is vertical and parallel to the film, with the
TM joint of interest adjacent to the film. The film is centered to a point ½˝ anterior to the
external auditory meatus. The occlusal plane should be parallel to the transverse axis of the
film so that the soft parts of the nasopharynx are in one line with the TM joint.
 The patient is instructed to slowly inhale through the nose during exposure, so as to ensure
filling of the nasopharynx with air during the exposure. The patient should open his mouth so
that the condyles move away from the base of the skull and the mandibular notch of the
opposite side is enlarged.
 Central Ray- It is directed from the opposite side cranially, at an angle of –5° to –10°
posteriorly
 Transpharyngeal projection. The central ray is oriented superiorly 5° to 10° and posteriorly
approximately 10°, centered over the TMJ of interest. The mandible is positioned at maximal
opening
23

 Transpharyngeal projection, showing positioning
from above, showing the X-ray beam aimed
slightly posteriorly across the pharynx
24

 This is the conventional frontal TM joint projection which is most successful in
delineating the joint with minimal super impositions, leading to the production of a
relatively true ‘enface’ projection.
 Structures Shown- The anterior view ofthe temporomandibularjoint and medial
displacement of fractured condyle and fracture of neck of condyle are clearly seen
in this view.
 Film Position- The film is positioned behind the patient’s head at an angle of 45° to
the sagittal plane.
 Position of Patient- The patient is positioned so that the sagittal plane is vertical.
The canthomeatal line should be 10° to the horizontal, with the head tipped
downwards. The mouth should be wide open.
25

 Central Ray- The tube head is placed in front of the patient’s face. The central ray is
directed to the joint of interest, at an angle of +20°, to strike the cassette at right
angles.
 The point of entry may be taken at:
• Pupil of the same eye, asking the patient to look straight ahead
• Medial canthus of the same eye
• Medial canthus of the opposite eye
26

 Structures Shown- This view is primarily meant for viewing
the condylar neck and head. High fractures of the condylar
necks, intracapsular fractures of the TMJ, quality of articular
surfaces, condylar hypoplasia or hypertrophy.
 Film Position-The cassette is placed perpendicular to the floor
placed vertically
 Position of Patient- The position of the patient is the same as
that in PA mandible, that is:
28

 Central Ray- Central ray is directed through the midsagittal plane at the level of the
mandible, and is perpendicular to the film
29

 Structures shown-
This view is used to evaluate facial growth and development, trauma,
disease and developmental anomalies. This projection demonstrates the
bones of the face, skull as well as the soft tissue profile of the face. The soft
tissue outline of the face is more readily seen on the resulting radiograph
when a filter is used. A filter is placed at the X-ray source, or between the
patient and the film, and serves to remove some of the X-rays that pass
through the soft tissue of the face, thus enhancing the image of the soft
tissue profile. In oral surgery and prosthetics it is used to establish
pretreatment and post-treatment records
 Film Position- The cassette is placed perpendicular to the floor with the
long axis of the cassette placed vertically. (FFD is the largest, 5 feet)
 Position of Patient- The right side of the patient’s head is positioned
against the cassette. The mid sagittal plane is perpendicular to the floor
and parallel to the film/cassette. The patient’s head is stabilized with the
help of the ear rods, nasion positioner and the orbital rod. The patient is
asked to keep the teeth in occlusion
 Central Ray- The central ray is directed perpendicular to the cassette
through the porion. The distance between the X-ray source and the
midsagittal plane of the patient is 60 inches.
30

 Structures Shown- It is used to survey the skull and facial
bones for evidence of trauma, disease or developmental
abnormality
 Film Position- The film is held vertically against the
patient’s cheek and centered so that the entire skull along
with the facial skeleton, is seen on the resultant
radiograph.
 Position of Patient-
The sagittal plane should be vertical and parallel to the film.
The film is adjusted so that the upper circumference of the
skull is ½ inch below the upper border of the cassette. The
patient here is asked to keep his/her teeth in occlusion, and
the occlusal plane should be parallel to the floor.
 Central Ray -The central ray is directed perpendicular to
the cassette and the midsagittal plane and towards the
external auditory meatus. The distance between the X-ray
source and the midcoronal plane of the patient is 36 to 40
inches
32

 It is used for the assessment of facial asymmetries and
for preoperative and postoperative comparisons in
orthognathic surgeries involving the mandible.
 The cassette is placed perpendicular to the floor in a
cassette holding device.
 Position of Patient -The sagittal plane should be
vertical and perpendicular to the film. The head is
tipped downwards so that only the nose touches the
film. The radiographic base line is at 10° with the film.
The film is adjusted so that the lips are centered to the
film.
 Central Ray -Central ray is directed at right angles to
the film through the midsagittal plane, centered at the
level of the bridge of the nose
34

 Structure is used to survey the skull vault and primarily the facial bones for evidence of trauma,
disease or developmental abnormality.
 Film Position- The cassette is placed perpendicular to the floor in a cassette holding device. The
long-axis of the cassette is positioned vertically
 Position of Patient- The sagittal plane should be vertical and perpendicular to the film. The
head is tipped downwards so that the forehead and nose touch the film. The radiographic base
line is horizontal and perpendicular to the film. The film is adjusted so that the lips are centered
to the film.
 Central Ray -The central ray is directed at right angles to the film through the midsagittal plane
through the occiput
35

 Structures Shown It is primarily used to
observe the occipital area of the skull.
The necks of the condyloid process can
also be viewed.
 The cassette is placed perpendicular to
the floor in a cassette holding device.
 Position of Patient -This is an
anteroposterior view, with the back of
the patient’s head touching the film. The
canthomeatal line is perpendicular to
the film.
 Central Ray -It is directed at 30° to the
canthomeatal line and passes through it
at a point between the external auditory
canals
36

 According to Speed of Film
37

 Different sizes of films used in intraoral radiography
38

39
Wrapper: It is made up of non-absorbent paper or plastic
or soft vinyl which is waterproof and is sealed to prevent
the ingress of saliva and light
The corners of the plastic packets are rounded to avoid
discomfort to patient while placing the packet in the
mouth. Black paper is used to protect the film from
light, damage by fingers while being unwrapped and
contamination from saliva which may leak into the film
packet
Lead foil is placed behind the film to prevent
the amount of residual radiation that has passed through
the film to continue into the patient’s tissues. It is also
used to prevent scattered radiation from reaching the
film which is formed due to interaction of X-ray photons
with the soft tissues beyond the film which cause film
fog leading to degradation of film (this small exposure of
the film results in radiograph that is more in density and
relatively dark).

40
BASE- It is the transparent supporting material upon which
the emulsion is coated. It is made of clear transparent
cellulose triacetate or thin polyester plastic (polyethylene
terephthalate), which acts as a support for the emulsion
but does not contribute to the final image. Cellulose
triacetate was introduced by George Eastman in 1924.
Emulsion-. It consists of silver halide (usually silver
bromide) crystals embedded in a gelatin matrix. Emulsion
is sensitive to X-rays, static electricity and visible light and
should be having wide latitude. The sensitivity of emulsion
depends on the size and thickness of the emulsion.
Thickness is 10 mm. Silver halide crystals are chemical
compounds that are sensitive to radiation or light. These
crystals are arranged parallel to the surface. These
comprise active ingredients. Ninety to ninety-five per cent
of silver halide is silver bromide and approximately 1–10%
is silver iodide. Silver halide crystals absorb radiation
during exposure and store energy from the radiation
Gelatin super coat: It acts as a
protective layer and shields
the emulsion from rough handling before
exposure,
scratching pressure and contamination
during
processing (Fig. 9.12). It also protects
emulsion from
pressure of roller while automatic
processing. It is
transparent so that light can pass through

 A radiographic image is produced by the interaction of X-rays with photographic
emulsion on a film after passing through an object. The formation of an image on
the film depends on the number of X-rays reaching the film, which in turn depends
on the density of the object.
 Latent image-: When a beam of X-ray passes through an object, some of the X-rays
are absorbed by the object, and some are penetrated through the object. The X-
rays which penetrate the object can expose the photosensitive crystals present in
the film emulsion. Collectively, the crystals with the silver specks form an image of
the object that cannot be seen visually. So, it is called the latent (invisible) image.
Hence, the latent image is defined as an invisible image that is produced in film
emulsion by light or X-ray, and is converted into a visible image by processing.
41

 Final image: A latent image is converted into a
visible record by series of chemical reactions which
is known as ‘processing’. The amount of deposited
black metallic silver seen on the radiograph
depends on the density of the structure being
radiographed. The white area occurs after removal
of unexposed silver halide crystals.
 Formation of latent image. Sensitivity site (A),
interaction of photon with silver halide crystal (B),
formation of negatively charged photoelectron
trapped at sensitivity site (C) and attraction of
positively charged silver ion towards the negatively
charged sensitivity site with formation of metallic
silver resulting in formation of latent image (D)
42

 Developer and
fixer are two
special
chemical
solutions that
are necessary
for film
processing.
 Developer
composition-
44

 Panoramic radiographic technique (also known as rotational
panoramic radiography) produces a wide single image that shows
maxillofacial region including maxilla, mandible and the adjacent
structures on a single film.
 It is a form of ‘tomography’, which is imaging by sectioning the
body structures. The panoramic technique utilises extraoral
radiation source and the film is also positioned outside the
patient’s mouth in a flexible or rigid cassette.
 The radiation source and the cassette rotate around a centre of
rotation resulting in an image that includes the entire dentition,
the surrounding alveolar bone, maxilla and mandible, the
sinuses, and the right and left temporomandibular joints. The
object of interest/patient is positioned in an area called ‘zone of
sharpness’. Structures within the zone of sharpness produce
relatively well-defined image, whereas objects outside the zone
of sharpness are blurred out
46

47
X-ray tube head-Produces the x-ray beam. The beam is aimed
slightly upwards, towards the slot in the cassette holder.
Diaphragm- The x-ray beam is collimated by the diaphragm to
form a vertical slit-shaped beam. The x-ray beam width should
be no greater than 5 mm.
Cassette holder-Has a metal sheet at the front that prevents
scattered x-ray photons reaching the cassette, which would
otherwise degrade the image. There is a narrow vertical slot in
the holder directly opposite the x-ray source. This ensures that
only a small amount of the film is exposed at one time.
Cassette carriage- Moves the cassette behind the cassette holder
during the exposure.
Bite block- Used to locate both upper and lower incisor teeth in
an edge-to-edge relationship in the focal layer. It also separates
the upper and lower teeth to prevent overlap.
Light-beam markers-Used to position the patient correctly, to
ensure that the teeth fall in the focal layer.
Head-holding apparatus- Allows the patient’s head to be
immobilised once accurately positioned.
Handles- Minimise movement of the patient.

 There is greater ease and less time taken to produce a panoramic radiograph as
compared to full mouth intraoral periapical radiographs, and the additional
advantage is that there is visualization of areas of the body of the mandible, ramus,
TM joint, and the maxillary sinus
 Panoramic radiographs are obtained using two methods:
1. Intraoral source of radiation: Status -X
2. Extraoral source of radiation: OPG
48

 In panoramic radiography, the film and X-ray tube head move around the patient. The X-
ray tube moves around the patient’s head in one direction while the film rotates in the
opposite direction. The patient may be seated or standing in a stationary position. The
movement of the tube head and the film produces an image through the process known as
tomography. (This is a curvilinear variant of conventional tomography, and is also based on
the principle of the reciprocal movement of an X-ray source and an image receptor around
a central point or plane, called the image layer). In panoramic radiography the image
confirms to the shape of the dental arches
 PRINCIPLE- If the film moves at a speed that follows the moving projection
of a certain point, this point will always be projected on the same spot on
the film and will not appear unsharp
49

 In panoramic radiography the film is attached to a rotating system and moves in the
opposite direction to the beam. The film is given the correct speed by apposing this
movement with a contrary movement relative to the beam.
 FOCAL TROUGH OR IMAGE LAYER-
It is defined as that zone which contains those object points which are depicted with
optimum resolution in other words it is a three-dimensional curved zone in which
structures lying within are clearly demonstrated on a panoramic radiograph
50
Focal trough-The closer to the center of the trough (dark
zone) an anatomic structure is positioned, the more
clearly it is imaged on the resulting radiograph

ROTATION CENTER
 In panoramic radiography, the film or cassette carrier and the 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 rotational
center
51

53
Types of panoramic X-ray machines:
(A) Double
center of rotation, machines have two rotational centers, one
for the
right and one for the left side of the jaws;
(B) Triple center rotation
machines have three centers of rotation and create an
uninterrupted
radiographic image of the jaws;
(C) Moving center rotation machines
rotate around a continuously moving center that is similar to
the
arches, creating an uninterrupted image of the jaws

 Nuclear medicine
Radioisotope imaging uses radioactive compounds that have an
affinity for particular tissues so called target tissues. These
radioactive compounds are injected into the patient, concentrated
in the target tissue and their radiation emissions are then
detected and imaged, usually using gamma camera. This
investigation allows the function and/or the structure of the target
tissue to be examined under both static and dynamic conditions
The various radionuclide-label tracers which are used are:
• Technetium pertechnetate (99m Tc-pertechnetate)— salivary gland,
thyroid, bone, blood, liver, lung and heart
• Iodine (131 I)—thyroid
• Gallium (67 Ga)—tumors and inflammation
• Selenium (74 Se)
• Krypton (81 Kr)—lung
54

 Principle-
As sound passes through any material, it encounters a
certain level of impedance referred to as an ‘acoustic
impedance’. As sound passes from tissues of one sound
acoustic impedance to another, some of it is reflected,
some of it continues to penetrate and some energy is
transferred to the particles of the medium as vibrational
energy. The greater the difference in acoustic
impedance of the tissue, the greater is the sound
reflected. This reflected sound (or echo) is picked up by
the transducer and converted into electric impulses and
finally displayed on the screen.
55

 This method is based on an electrostatic process similar to that used for xeroxing.
Conventional X-ray source is used in the production of xeroradiographs.
 The film is replaced by a selenium coated photoreceptor (Xerox Plate), which has an
uniformly distributed electrostatic charge. The charge is applied by a conditioner that
also inserts the charged plate into a lighttight cassette.
 During an exposure, X-rays that penetrate a body part or object are absorbed by the
surface of the selenium plate causing selective discharging. The distribution and the
amount of discharge is related to the distribution and amount of radiation striking the
xerox plate and, therefore, the information in the transmitted X-ray beam is left as a
charged pattern on the plate. The pattern of electric charge, the latent image, is
analogous to the latent image produced by the reduction of silver bromide molecules
to free silver atoms in the sensitivity specks of a photographic emulsion.
 The latent image is developed into a visible image. During development a cloud of
charged powder particles of toner is exposed to the plate, and the powder particles
are attracted to the charged pattern on the surface. The association between the
toner and the plate is related to the distribution of charge. When the development is
complete, the visible image is transferred to paper in a machine referred to as a
developer.
 Xeroradiograph can be viewed in reflected or transmitted light. When the latent
image is transferred from plate to paper, the original image is reversed 180° and is
seen as a mirror image. 56

 Tomography is a generic term formed from the Greek words tomos
meaning ‘slice’ or ‘section’ and graphia meaning ‘picture’ or
‘describing’
 Conventional Tomography-
Body section radiography is a special X-ray technique that enables
visualization of a section of the patient’s anatomy by blurring regions of
the patient’s anatomy above and below the section of interest. This is
achieved by a synchronized movement of the film and the tube in
opposite directions, about a fulcrum (i.e. the plane of interest in the
patient’s body).
Objects closest to the film are seen most sharply and objects farthest
away are completely blurred.
57

58
The tube and the film are rotated
around the fulcrum(C) during an
exposure.
When the exposure is initiated, the
objects at the top of the body being
examined (T) are on the right side of
the film while objects in the center of
the body (C) lie in the center of the film
and objects at the bottom of the body
(B) lie at the left side of the film.
During exposure, the positions of B and
T reverse while the position of C
remains constant

 Computed Tomography (CT) imaging is also known as ‘CAT scanning’
(Computed Axial Tomography).
 CT utilizes a narrow fan-shaped X-ray beam and multiple exposures
around an object to assess its anatomical structures enabling the
clinician to observe the morphologic features and pathology in three-
dimensions so that it can also measure the bucco-lingual extent of the
lesions overcoming the drawback of 2-D imaging.
 CT scanner system is containing a radiographic tube connected to a
series of scintillation detectors or ionization chambers. The patient is
moved inside the circular aperture in the centre of the gantry. The
tube head and reciprocal detectors within the gantry either rotate
synchronously around the patient, or the detectors may form a
continuous ring around the patient and the X-ray tube may move in a
circle within the detector ring.
59

 In spiral CT, the patient is moved continuously through the rotating gantry and image data are obtained as
a “spiral” or “helix” rather than in the form of a series of slices. When comparing to CT scanners, spiral
scanners result in better multiplanar image reconstructions, decreased exposure time (12 s vs 5 min), and a
diminished radiation dose (up to 75%)
 Current CT scanners are called multi-slice CT scanners as they contain linear array of multiple detectors (up
to 64 rows) that simultaneously acquires tomographic data at different slice locations. The benefits of it
include decreased scan time, reduced artifacts, and improved resolution (up to 0.4 mm isotropic voxel).
 CT results in high contrast resolution and has ability to differentiate the tissues with < 1% physical density
difference compared to 10% required for conventional radiography .
 CT images have less noise (i.e., they are less grainy), which results from superior collimation of the
emerging beam in CT machines. CT has been proven as gold standard imaging technique for interpretation
of the maxillofacial skeleton structures. It helps in diagnosing the complex facial fractures, like those
involving the frontal sinus, naso-ethmoidal region , and the orbits . It also detects undisplaced fractures of
the mandible and the condyle, which are not generally seen on panoramic radiographs. CT scan has also
been proved helpful in determining vertical root fracture or split teeth which cannot be very obvious on
periapical radiographs, since CT has not been found sensitive to beam orientation unlike conventional x-ray
methods .
 CT is also able to detect multiple extra root canals and chronic apical periodontitis at early and established
stages that can be observed as periodontal space widening with small osteolytic reaction around the root
apices. Spiral CT may help in interpretation of the close relationship between maxillary sinus disease and
adjacent periodontal defects and their treatment . Also, CT scan can accurately differentiate between
intrinsic and extrinsic salivary tumors and is used for tumor’s staging
60

 LIMITATIONS OF CT-
The disadvantages of CT imaging include high radiation exposure, high costs of the scans and scatter because of
metallic objects. It has poor resolution compared to conventional radiographs.
Tuned Aperture Computed Tomography (TACT)-
TACT is comparatively a simple, faster method for reconstructing tomographic images, introduced by Webber and
colleagues.
It utilizes the mechanism of tomosynthesis and optical-aperture theory. TACT needs 2-D periapical radiographs
obtained from different projection angles as base images and allows retrospective creation of longitudinal
tomographic slices (TACT-S) lining up in the Z axis of the concerned area. It generally results true 3-D data from any
number of arbitrarily oriented 2-D projections. The overall radiation dose of TACT is usually within double to that of a
conventional periapical X-ray and the resolution has been found similar with 2-D radiographs.
Also, it does not produce artifacts like starburst patterns as seen with metallic restorations in case of CT. TACT
produces more accurate imaging for assessing non- destructive osseous changes within the healing bony lesions. It
has also been proved that TACT can be a better option for analyzing trauma induced radicular fractures and
mandibular fractures . TACT can also be alternative to CT for pre-surgical implant assessment. However, TACT is still at
trial phase but thought to be a effective imaging technique for the future dentisty
61

 This technique uses a cone-shaped X-ray beam centered on a
2-D detector. It performs 360˚ rotation around the object and
generates a series of 2-D images which are reconstructed in 3-
D using a modification of the original cone-beam algorithm.
Radiation dose of one CBCT scan equals 3-20% that of a
conventional CT scan, depending on the equipment used and
the area scanned.
 X-ray tubes of CBCT cost very less when compared to
conventional CT. Images results in isotropic voxels that can be
as small as 0.125 mm. CBCT provides a high spatial resolution
of bone and teeth which permits definite understanding of the
relationship of the adjacent structures. CBCT has wide
applications in dentistry. High resolution of CBCT imaging
determines variety of cysts, tumors, infections, developmental
anomalies and traumatic injuries involving the maxillo-facial
tissues plus evaluating dental and osseous disease in the jaws
and temporo-mandibular joints and treatment planning for
dental implants. CBCT is categorized into large, medium, and
limited volume units based on the size of their field of view
(FOV).
62

 Smaller scan volumes have higher resolution
images and low effective radiation dose. Size of
the concerned area exposed to radiation is the
principal demerit of large FOV imaging . Large
FOV units are very helpful in analyzing the
maxillofacial trauma, orthodontic diagnosis and
treatment planning, temporomandibular joint
(TMJ) and pathologies of the jaws.
 Medium FOV is used for assessing the
mandibulomaxillary imaging and for pre-implant
planning and pathological conditions while Small
FOV units (limited FOVs) are suitable for dento-
alveolar imaging and are most beneficial for
endodontic implementations
63

 CBCT has the problem of scattering and beam hardening artifacts caused by high
density structure which diminishes the contrast and limits the imaging of soft
tissues. Therefore, CBCT is primarily indicated for imaging hard tissues .
 Also, CBCT cannot be helpful in detecting bone density because of distortion of
Hounsfield Units.
 CBCT has lengthy scan times (15-20 sec) and they need the person to stay
completely firmed.
65

 MRI scan is a specialized imaging technique without ionizing radiation.
 Most MRI machines are graded on the strength of the magnet, measured in Tesla units, which is the equivalent of 20000
times the magnetic field strength of Earth. MRI units contain the range of 1.5 to 3 Tesla units for in vivo utilization. MRI
principle is based on behavior of hydrogen atoms (consisting of one proton and one electron) within a strong magnetic field
which is used to generate the MR image. This forces the nuclei of many atoms in the body to align themselves with the
magnetic field. The machine implies a radiofrequency pulse to depolarize the atoms and the energy that is emerging from the
body is utilized and used to generate the MR image by a computer.
 The MRI has high contrast sensitivity to soft tissue differences as hydrogen is found in abundance in soft tissue, but is lacking
in most hard tissues and this is the main reason behind MRI replacing the CT for soft tissues imaging. MRI provides the best
resolution of tissues with low inherent contrast. Some cases of squamous cell carcinoma of the tongue can only be detected
with MRI. The main use of MRI in dentistry is for investigation of soft-tissue lesions in salivary glands, TMJ and tumor staging.
Also, it seems to be ideal for assessment of internal derangement of TMJ. MRI can also detect joint effusions, synovitis,
erosions and associated bone marrow edema.
 Odontogenic cysts and tumors can be differentiated better on MRI than on CT. It also helps in detecting the soft tissue
diseases like neoplasia, involving tongue, cheek, salivary glands, neck and lymph nodes. MRI can also precisely differentiate
between solid and cystic lesions on the basis of signal characteristics and enhancement patterns. It also permits accurate
differentiation between the keratocystic odontogenic tumor (KCOT) and other odontogenic lesion.
 A recent introduction in MRI technology is called SWeep Imaging with Fourier Transform to assess the dental structures. It
can simultaneously image both hard and soft dental tissues with high resolution with less scan time. It can also detect the
extent of carious lesions and simultaneously find the pulpal tissue condition, whether reversible and irreversible pulpitis,
which can influence the treatment planning
66

Limitations of MRI:
 MRI is usually not supposed to be used in patients with cardiac pacemakers,
implantable defibrillators, some artificial heart valves, cerebral aneurysm clips, or
ferrous foreign bodies in the eye.
 Metallic dental restorations can generate artifacts producing a major diagnostic
problem in CT examinations of malignant tumors in the maxillofacial region.
 Claustrophobic patients should not be positioned in the close confines of an MRI
machine.
 Other drawback of MRI includes long scanning time and much expensive compared
to other conventional radiographic methods.
68

Digital Radiography
 The term digital radiography refers to a method of capturing a radiographic image
using a sensor, breaking it into electronic pieces and presenting and storing the
image using a computer. This system is not limited to intraoral images; panoramic
and cephalometric images may also be obtained.
 RADIATION EXPOSURE-Digital imaging requires less X-radiation than conventional
radiography, because the sensor is more sensitive to X-rays than a conventional film.
Exposure time for digital radiography is 50–80 percent less than that required for
conventional radiography using E-speed film, and thus the absorbed dose to the
patient is much lower
69

 METHODS TO OBTAIN AN INTRAORAL DIGITAL IMAGE
Direct digital imaging: Here a sensor is placed in the patient’s mouth and exposed to
radiation. The sensor captures the radiographic image and then transmits the image to
a computer monitor, and within seconds the image appears on the computer screen
Indirect digital imaging: In this method an existing X-ray film is digitized using a CCD
camera, which scans the image, digitizes or converts the image and then displays it on
the computer monitor.
Storage phosphor imaging: It is a wireless digital radiography system. A reusable
imaging plate coated with phosphors is used. These plates are flexible and fit into the
mouth. The storage phosphor imaging records diagnostic data on the plates following
exposure to the X-ray source and uses a high-speed scanner to convert the information
to electronic files which can be displayed on the computer screen
70

 PSP based radiography: It is applied to CR
(Computed Radiography) system and has been
used for extraoral projections and image analysis
including dental panaromic radiography
 CCD systems: Using solid state linear array of
photoiodides (DR system).
 Scheme of direct digital image acquisition using
two types of CCD-based systems
 Extraoral digital imaging is available using both
systems. However the larger CCD sensors are
extremely expensive and usually requires the
purchase of new X-ray generators, although a
‘retro-fit’ system has been developed. These
constrictions effectively mean that the PSP
method is the most commonly used.
71

 The essential components of a direct imaging system include:
• X-radiation source
• Sensor
• Digital image display
72

 X-RADIATION SOURCE-Most digital radiography systems use a conventional X-ray unit
as the radiation source. The X-ray unit timer has to be adapted to allow exposures
in a time frame of 1/100th of a second. A standard X-ray unit that is adapted for
digital radiography can still be functional for conventional radiography
 SENSOR-
Extraoral: PSP plates
Intraoral: Intraoral sensor is used instead of the intraoral film. It is a small detector
that is placed in the mouth of the patient and used to capture the radiographic image
73

 Superior gray scale resolution
 Easy reproducibility
 Reduced exposure to radiation
 Increased speed of image viewing
 Lower equipment and film cost
 Increased efficiency
 Enhancement of diagnostic image
 Excellent quality image with no loss of quality commonly associated with
conventional chemical processing
 Image processing, enlargement and reconstruction for specific diagnostic purpose is
possible
79

 Initial set-up is costly
 Image quality is still a source of debate
 Sensor size is thicker than intraoral films and therefore not patient compliant
 Infection control, the sensor has to be covered adequately in a disposable plastic
wrapper
 Legal issues, because the original digital image can be manipulated, it is debatable
whether digital radiographs can be used as evidence in lawsuits
80

 The reference radiograph is digitized and converted into its positive image by the computer. The
subsequent radiograph is then displayed on the same server and aligned to the reference image and
then digitized. Subtraction of the gray levels between the two images is then performed. Any
change that has occurred between the original radiograph and the subsequent radiograph shows up
as light or dark areas. Loss of bone is seen as dark areas and gain of bone as light areas.
 Use of digital subtraction radiography for detection of periodontal bone healing: (A) Image before
surgery; (B) Image after 6 months; (C) Subtraction image showing the bone formation
81

 Film badges are the most common form of personal monitoring device. They consist
of blue plastic frame containing a variety of different metal filters and a small
radiographic film which reacts to radiation. Size of radiographic film used is about 4
× 3 cm. The film badges can be provided with different types of filter, i.e.
aluminium, copper, cadmium, plastic and lead. They are usually in wedge fashion.
All the filters are 1 mm thick except thin copper which is 0.15 mm thick. The filter
assesses the penetrating power of the radiation and thus permits the energy to be
estimated. Film badges are worn outside the clothes usually at the level of the
reproductive organs, for 1–3 months before being processed. They are usually worn
in metallic batches. The film should be loaded in the film holder so that the flap
side of the film pack is always facing the body.
82

 There are three types of film badges: chest holder, wrist holder and head holder .
The film is processed and measures the degree of darkening. It must be compared
with films exposed to known radiation. All the films must be of same emulsion and
developed under the same standard conditions.
 The regular reporting of the results to the person concerned contributes to more
careful attention to the radiation protection rules.
 The minimum dose that film badges can detect is about 0.2 mSv. If the person has
received more than 10 mSv dose in 1 month, it is considered as overexposure and
same should be reported promptly to the institution and the individual
83

 Thermoluminescent dosimeters: These are used for personal monitoring of the
whole body and the extremities as well as measuring the skin dose from particular
investigation. They contain material, such as LiF which absorbs radiation.
• Ionisation chamber: Ionisation chamber is used for personal monitoring by physicist
to measure radiation exposure.
• Rate meter: It is also called roentgen ray rate meter. It has an ion collection
chamber that is continuously being charged by battery
84

 Radiation exposure limits were introduced
by the International Commission on
Radiological Protection (ICRP), which was
founded in 1928. In India Atomic Energy
Regulatory Board (AERB) is the competent
authority. It implements safety provision by
Atomic Energy Act, 1962
 GUIDELINES FOR RADIATION SAFETY
85

 Clinical cases of radiation damage from dental X-ray have not been reported, but it
is not proved that there is no possibility of occurrence of this. So, it leads to the
concept of ALARA. All exposure radiation must be kept ‘as low as reasonably
achievable’ (ALARA). So, ALARA means all possible measures which should be taken
to ensure that occupationally and non-occupationally exposed persons will receive
the smallest amount of radiation. Radiation hygiene must be practised in dental
office to minimise the use of X-ray and maximise the diagnostic information
obtained from radiograph
86

PRINCIPLE OF RADIATION PROTECTION
 Justification of practice: There should be justification of practice and limitation of individual dose
and risk.
 Protection as near as possible to the tube: The major portion of radiation protection should be as
near as possible to the tube. It saves total volume of barrier material.
 Leakage radiation: X-ray equipment should be appropriate and X-ray tube housing should provide
minimum radiation leakage.
 Direction of useful beam: The X-ray beam should be collimated strictly to the region of clinical
interest.
 Highest kVp: The highest kVp compatible with image quality requirement should be selected.
 Fast film: The fastest film screen combination compatible with the image quality should be used.
 Focal spot to film distance: The longest focus to film distance within the limitation of the X-ray
equipment should be used.
 Filtration: Additional filtration should be used.
 Walls and ceiling: The walls, floor and ceiling of X-ray room should have protective covering.
87

 Control room: It must be provided with appropriate shielding, direct viewing and
communication facilities between operator and patient.
 Tube shielding: The casing should be done for housing and supporting the tube and oil,
making the tube shock free and protecting the patient and staff from unwanted
radiation.
 Entrance: Suitable electrical interlocks between doors and equipment must be provided.
Suitable warning signal in the form of display lamps and placards must be provided near
the entrance of the door.
 Viewing window: Viewing window often needs the radiological installation. Usually this is
made by adding lead salt to the silicates used in manufacture of glass. It is acceptably
transparent and, being denser, it is a better protective material than ordinary glass.
 Waiting room: Waiting areas for the patients with toilet facility must be provided outside
the room
88

 Optimising the radiographic process is the best way to ensure maximum patient benefit
with minimum of patient and operator exposure.
Before Exposure—
 Patient selection- Patient should be asked about previous radiograph taken if any.
Previous radiograph can provide relevant information required, thus preventing
unnecessary exposure of the patient
 High yield or referral criteria: Radiographic selection criteria are also known as high
yield or referral criteria. These are clinical or histological findings that identify patients
with high probability in which radiographic examination can provide information that
would affect their treatment or prognosis. Radiograph should be taken only if clinically
necessary. The number, frequency and type of radiograph taken should be judged by the
clinician. No patient should be irradiated unnecessarily if relevant information can be
gathered by previous radiograph. Recall radiograph should not be taken for all patients
as a routine. It should be taken only for those patients who really need it.
89

 Administrative radiographs : Radiograph
should not be taken for administration
purpose and in case if it is necessary
radiograph should be duplicated or should be
taken in double film packet.
 Focal spot to skin distance-Increased source
to patient distance reduces the amount of
radiation to patient. The reduction is due to
the fact that when tube–patient distance is
short, the X-ray beam diverges more in the
patient Normally two standard distances are
used, 100 and 400 mm. A minimum focal spot
is 100 mm below 60 kV, and 200 mm above 60
kV. Use of longer distance has resulted in 31%
decrease in surface exposure at 70 kV and 36%
decrease in 90 kV.
90

 Collimation: : The tissue area exposed to primary X-ray beam should not exceed the
minimum coverage consistent with meeting diagnostic requirements and clinical feasibility.
Patient exposure can be significantly reduced by limiting the size of X-ray beam by using
collimator (always use the smallest possible film size; ). Limiting the size of X-ray beam to
the size of periapical film is accomplished by rectangular position indicating device (PID;).
Use of rectangular collimation reduces the absorbed dose by 60–70%. It has exit orifice of
3.5 × 4.4 cm which will reduce patient’s surface exposure by 60% over that of round (7 cm)
PID. Film holders with rectangular collimator may be used with round PID
92
Effect of collimator on exposure. (A) The beam produced by a
circular collimator is 2.75 in. in diameter; (B) the beam
produced by a rectangular collimator is just slightly larger than
a size 2 intraoral film

93
Collimator effects.
(A) More area is irradiated without collimator;
(B) Less area is irradiated with collimator

 Filtration-The purpose of conventional filtration is to
selectively remove low-energy X-ray photons from the X-ray
beam which will result in decreased patient exposure with no
loss of radiographic information. When an X-ray beam is
filtered with 3 mm of aluminium, the surface exposure is
reduced to about 20% than without filtration. Nowadays
filtration can remove both low- and high-energy X-ray photons
from the beam leaving the mild-range-energy photons to
expose the film
Effect of filtration as seen by less number of X-rays
(only penetrating rays) passing through the patient
94

 PID-Long PID is preferred because of less divergence of the X-ray beam. Out of three
types (cone, rectangular and round types) of PID, the rectangular type of PID is the
most effective in reducing the patient exposure. Point-ended PID should not be used
because scattered radiation is more due to interaction of primary beam with close
end of the cone.
 Head leakage: Dental X-ray machine must be monitored for leakage radiation, i.e.
any radiation except primary radiation which is emitted from the dental tube head
should be checked. The only radiation that should escape is primary radiation. It is
very uncommon and never occurs if X-ray machine is not moved and not abused.
 Tube head drift: Tube head drift is a common problem that can be easily corrected.
The tube head of dental X-ray machine should not move or drift in any direction
after the positioning of the patient.
95

 Kilovoltage: Surface exposure delivered during exposure of film to diagnostic density
varies, irreversibly with energy of X-ray beam. Patient skin exposure is decreased as
the kilovoltage peak (kVp) increases, but dose to deeper tissue and scatter radiation
increases. kVp best suitable for diagnostic purposes should be used, i.e. in the range
of 65–90.
 Milliampere seconds: Film should not be overexposed or underexposed which can
result in needless patient exposure. Usually exposure time should be less by
increasing the milliamperes of the machine
96

During Exposure
Film selection:
It should be having maximum sensitivity and consistency with image quality required for diagnostic task. Intraoral film is
available in two speed groups, D and E. Film E is twice faster than D film and exposure is 0.2500, so film E is used in
routine intraoral radiographic examination without sacrificing diagnostic information. The use of double film packet is also
useful in reducing patient exposure by 50%. Xeroradiography also reduces the patient exposure. Intensifying screen should
be used for all extraoral views. Green emitting intensifying screens are eight times more sensitive to X-ray than blue
emitting. Fastest film screen combination should be used. Nowadays, RVG is used to reduce exposure to the patient
Film-holding device:
It is also effective in reducing a patient exposure to X-radiation. A film-holding device is used to stabilise the film position
in the mouth and reduces the chances of movement. It also relieves patient’s finger to hold the film, and thus, it is not
exposed to unnecessary radiation.
Lead apron: Leaded apron should be used to minimise unnecessary radiation . It is a flexible shield that is placed over
the patient’s chest and lap to protect the reproductive and blood-forming tissue from scatter radiation. Aprons available
are usually the equivalent of 0.25 mm of lead and relatively flexible. The gonad dose from one dental periapical film is
0.77 × 10−7 C/ kg, and by using lead aprons it is reduced to 0.46 × 10−8 C/kg. Use of lead apron is recommended for all
intraoral and extraoral radiographic procedures. Routine use is justified to allay perceived patient’s anxiety. But use of
lead aprons during panoramic radiography should be discouraged as it may interfere with the machine. Lead apron
should not be folded but rather hung up or draped over the rounded surface when not in use. 97

 Thyroid collars: They are used when
thyroid gland is in the primary beam
. It can reduce the dose to thyroid
gland by 94%. It is a flexible lead
shield that is placed securely around
the patient’s neck to protect the
thyroid gland from scattered
radiation. It may exist as a separate
shield or as a part of lead apron . It
prevents radiation from reaching the
gland and protects highly
radiosensitive tissue of the thyroid.
Use of thyroid collar is recommended
for all intraoral films, and it is not
recommended for extraoral films
98

 Lead glass goggles: The use of lead glass goggles
has been recommended for the protection of eyes
 Gonadal shield and ovarian shield: This can be used
to avoid exposure to gonadal and ovarian glands
 Intraoral technique- Proper radiographic technique
should be practiced to produce good-quality
radiograph to avoid repeat radiograph and curtail
further exposure. Parallel line angle technique is
more efficient as compared to bisecting angle
technique. Parallel results in lower dose to thyroid
gland and lens of the eyes. Long-cone technique is
more efficient than short-cone technique. All
radiographs should be as accurate as possible, thus
avoiding the need for repeat exposure. The more
efficient the technique, the fewer repetition of
radiograph will be required and less would be the
patient exposure. Every retake causes an
unnecessary doubling of radiation exposure to the
patient. The technique that employs overexposure
with underdevelopment subjects patient to
unnecessary radiation. If exposed films are too
dark, temperature of processing, the exposure
time or the kVp should be reduced and developing
time should be kept constant. Film holder
incorporating beam-aiming devices should be used
in intraoral radiography whenever possible. 99

After Exposure
 Film processing: From the beginning of exposure of film till its processing, careful
handling of the film should be done. Improper film handling may lead to artefacts
and, in turn, result in non-diagnostic film. Nondiagnostic film has to be retaken, and
results in more radiation exposure to the patient. Processing should be reliable,
consistent and monitored regularly. The darkroom should be kept free from light
leaks to avoid film fog. Time–temperature method instead of manual processing
should be applied as it is the only way for proper image development. Processing
solution should be changed regularly, stirred thoroughly and kept covered to prevent
oxidation.
 Viewing: To obtain maximum detail radiograph should be viewed in a dimly lighted
room with properly functioning illuminator
 Storage of film: Films may get displaced or lost due to carelessness, so to avoid
repetition of radiographs proper storage of film should be done.
100

 Department should lay down requirements of radiation
protection to walls, floor, ceiling and doors to shield persons
in adjacent rooms. There should be adequate protection
around the X-ray tube. Appropriate lead screen/barriers
should be used.
 Time: The total dose received by the workers is directly
proportional to the total time spent in handling the source.
It is best to minimise the time spent in any radiation area. It
is done by quickly finishing the work or sharing the work
with more persons
 Distance: Reduction of exposure due to increase in distance
is governed by the inverse square law . As the distance from
a radiation source increases the radiation exposure
decreases rapidly. Installation should be such that the
operator can stand at least 6 ft. from patient during
exposure. Operator should stand 6 ft. from the patient at an
angle from 90 to 135° to the central ray beam . The areas of
maximum scatter are at the back of tube head and behind
the patient
101

 Avoid primary beam: Operator should not be in
line of the primary beam. He or she should not
hold the film in oral cavity
 Shielding: Protective barrier that absorbs the
primary beam can be incorporated into the
office design, thus protecting the operator from
primary and scattered radiation. Operator should
stand behind a suitable barrier during exposure
of film . The barrier should have window or other
means for monitoring the patient during
exposure. Most dental offices incorporate
adequate shielding in walls through the use of
more thickness of common construction material
such as dry wall
102

 Equipment: All safety procedures recommended for
reducing the dose to the patients are applied for
operator protection also. Always use the smallest
possible X-ray beam which minimises radiation to the
radiographer. Every X-ray machine should be
equipped with either 6 ft. retractable exposure cord
or remote switch that permits such operator
positioning
 Radiographic technique: Radiograph should be taken
by trained staff only. Film should never be held by
operator. No member of staff should ever hold the
tube head during an exposure . If a child or unsteady
patient needs support, it should be done by
accompanying parent or person not concerned with
the radiology department. He or she should be
provided protective clothing . Good processing
technique should be used. One should not stay in X-
ray room unnecessarily during exposure
103

 Personal monitoring: Monitoring is recommended for the period of 3–6 months after
new radiographic equipment is installed to ensure that dose limits are not being
exceeded. The maximum annual dose limit is 15 mSv. Film badges should be worn at
waist level whenever dental radiographer is exposing X-ray films
104

 The foundation of an accurate diagnosis and treatment plan is based on a
comprehensive medical and dental history, a thorough clinical examination, and
diagnostic radiographs. Of the three, obtaining diagnostic radiographs in the
pediatric dental patient is probably the most difficult to accomplish from a
technical standpoint and because of parental fears and misconceptions
 With the news media reporting on a daily basis the environmental insults
experienced by the human body, parents may be preoccupied with the effects of
diagnostic and treatment procedures on their child’s health. Reducing the possible
deleterious effects of preventive and restorative materials, sterilization protocols,
and diagnostic techniques should be a concern of parents and dentists.
105

 During the first appointment, a dental professional reduces a parent’s resistance to
the use of radiographs by informing the parents of the diagnostic need for
radiographs and educating them about current radiation hygiene practices and
radiographic techniques. An explanation should include the concept that without
radiographs, an examination only detects the tip of the iceberg. It should be
emphasized that visual examination reveals only three of the five surfaces of the
teeth because if the child’s teeth are close together the dentist cannot see between
them. Furthermore, the dentist cannot see the insides of the teeth, their roots, nor
the permanent teeth developing in the jaws. Radiographs enable the dentist to
detect the start of visually undetectable cavities between teeth, infections of the
teeth, gums and bones, the shape and presence of unerupted permanent teeth,
potential orthodontic problems, and a host of other pathological conditions.
106

 Although excessive radiation exposure can result in cancer, birth defects. and
genetic defects, the amount of radiation needed to expose the newer X-ray film has
significantly reduced the amount of radiation to which patients are exposed. As
digital radiography gains wider use in the dental practice, dental professionals who
use this new technology should mention that it further reduces the amount of X-
radiation exposure to a minimum.
107

 X-rays should not be taken routinely. A dentist should first examine a child’s teeth and
medical status before ordering radiographs. The guidelines suggest the number and
types of radiographs necessary depends on the age of the child, the presence and
amount of visual decay, the child’s and family’s history of dental treatment, and spaces
between teeth.
 If possible, obtain copies of prior radiographs (from other office, if available).
 The patient should be protected with a lead apron and thyroid collar to reduce body
exposure to radiation.
 The highest film speed and largest film that the child can tolerate should be used so as
to reduce the number of radiographs needed.
 Use the manufacturer’s recommended time and temperature for processing. Parents
have the right to ask that the dentist refrain from taking radiographs. However, the
dentist has the responsibility to refuse treatment if not taking the radiograph
compromises the patient’s treatment. Parents cannot relinquish the right to competent
care by a dentist.
109

 In the rare occasion when a very young dental patient under three
years of age needs a radiograph, the dental office should be prepared
with techniques to reduce any psychological trauma.
 The first step in desensitizing a child to the dental experience is to
explain what you plan to do in words that are easily comprehended.
Using a tell, show, do technique, the clinician explains to the child
that a tooth camera will be used to take a picture of their tooth. The
child is allowed to touch and examine the radiographic film and
camera. To gain maximum cooperation in the child under three years
of age, it may be necessary for the child to sit in the parent’s lap
while exposing the radiograph. This position may reduce the child’s
anxiety to such a degree that minimal restraint may be needed to
successfully take the radiograph. The child is seated in the parent’s
lap with the parent’s arms around the child’s upper body and the legs
wrapped around the child’s lower body. Not only does this provide the
child additional emotional security thus increased cooperation, but
also enables the parent to adequately restrain the child should there
be any unexpected sudden movements.
110

 Obtaining the least difficult radiograph first
(such as an anterior occlusal) desensitizes the
child to the procedure. Since many children have
difficulty keeping the film in their mouth for
extended periods of time, be certain the correct
settings are made on the apparatus and the X-ray
head is properly positioned before placing the
film in the child’s mouth. A positioning device
such as a Snap-A-Ray instrument can be used to
aid the parent in positioning and securing the
film. Be sure to adequately protect the parent
and child with lead aprons to reduce radiation
exposure
 If the child is uncooperative, then additional
restraint by a second adult may be necessary to
successfully obtain the radiograph. With the first
adult restraining the child as described
previously, a second adult stabilizes the child’s
head with one hand while the other hand
positions the Snap-A-Ray instrument in the
patient’s mouth. Under no circumstances should
staff be asked to perform this task.
111

 Taking a radiograph may be the child’s first dental experience. So it
has to be made as pleasant as possible. Euphemisms should be used
with TSD technique. (By bringing the X-ray tube near the parents face
or a doll’s face first, helps to dispel any fear the child may have).
Modelling behavior management technique will also help reduce fear.
Parents or siblings can play the role of a model. Children are also
more willing or cooperative if they know that they are required to
hold the film in the mouth for a limited period of time
112

 The Journal of Contemporary Dental Practice, Volume 1, No. 4, Fall Issue, 2000
 : American Academy of Pediatric Dentistry. Prescribing dental radiographs for
infants, children, adolescents, and individuals with special health care needs. The
Reference Manual of Pediatric Dentistry. Chicago, Ill.: American Academy of
Pediatric Dentistry; 2023:308-11.
 Textbook of Oral Radiology - by Anil Govindrao Ghom
 White, S.C. and Pharoah, M.J. Oral Radiology: Principles and
Interpretation, 7th Edition, Elsevier, Health Sciences Division, Amsterdam,
41-63
115

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