Radiographic techniques and effects of xray beams.

1. RADIOLOGY IN
PEDIATRIC
DENTISTRY
Presented by:
Khushboo Sinhmar
MDS 2nd Year
Department of Pedodontics and
Preventive Dentistry

2. CONTENTS
• Introduction
• History of X-ray in dentistry
• Xray machine
• Types of Radiographs
• Intraoral radiograph
• Clinical situations for which radiographs are indicated
• Guidelines for prescribing radiographs in children
• Radiographic Examination

3. • Radiographic techniques
• Modification for infants
• Management techniques
• Extraoral radiographs
• Newer digital radiographic techniques
• Radiation hazards and protection
• Technical errors
• References

4. • Plays a vital role in the diagnosis and treatment planning of
both children and adults.
• Plays a significant role in the assessment of growth and
development.
• At the simplest level, help in the detection of dental caries and
at the most complex level, in the diagnosis of cysts, tumors or
any other major craniofacial disorders.
INTRODUCTION

5. History
Wilhelm Conrad
Roentgen
1845 - 1923
The first radiograph – Mrs. Roentgen’s
hand

6. Dental X-Ray Machine

7. Types of Radiographs
1) Intraoral films
2)Extraoral films
INTRAORAL: Intraoral films are meant for
positioning inside the mouth. 3 types of intraoral
radiographic projections:
1) IOPA radiographs
2) Bitewing radiographs
3) Occlusal radiographs

9. Intraoral Periapical Radiograph
Indications:
• To evaluate the development of the root end and to study the
periapical tissue
• To detect alterations in the integrity of the periodontal
membrane
• To evaluate the prognosis of the pulp treatment by observing
the health of the periapical tissues
• To identify the stage of development of unerupted teeth
• To detect developmental abnormalities like supernumerary,
missing or malformed teeth

10. Techniques
• Paralleling Technique
• Bisecting Angle Technique

11. Parallelling Technique
• Also called as Long cone
technique/Right angle
technique/MC Coarmack’s
technique/Fitzgerald
technique
• Principle: The central concept
of the paralleling is that “the x-
ray receptor is supported
parallel to the long axis of the
teeth and the central ray of the
x-ray beam is directed at right
angles to the teeth and
receptor”.

12. Advantages
•Accurate image
•Interdental bone level clearly represented
•Minimum foreshortening and elongation
•X-ray beam aimed at centre of film and prevents cone cut
Disadvantages
• Uncomfortable
• Positioning of holder is difficult
• Anatomy of mouth sometimes make the technique difficult

13. Bisecting angle Technique

14. • Millers Right angle technique, short cone technique,
Isometric triangulation technique
• The bisecting-angle technique is based on a simple
geometric theorem, Cieszynski’s rule of isometry,
which states that two triangles are equal when they
share one complete side and have two equal angles.

15. • Advantages
- Position of the film is reasonably comfortable for the
patient in all areas of the mouth
- positioning simple and quick
- if all angulations are assessed correctly. The image of
the tooth will be the same length as the tooth itself
- decreased exposure time

16. Disadvantages
- many variable invoved in tech often result in the
image being badly distorted
- incorrect verticlal angulation result in foreshortening
or elongation
- periodontal bone levels are poorly shown
- Shadow of zygomatic buttress frequently overlies the
roots of upper molar
- Horizontal and vertical angulation have to be assessed
for every patient and considerable skill is required
- not possible to obtain reproducible views

17. Component of IOPA film packet
Components of IOPA film packet: A. Outer plastic
wrapper; B. Black paper; C. Film; D. Lead foil

18. Bitewing Radiograph

19. Indications :
• Early detection of incipient interproximal caries
• To understand the configuration of the pulp chamber
• Record the width of spaces created by premature loss of
deciduous teeth
• Determine the presence or absence of premolar teeth
• To determine the relation of a tooth to the occlusal plane for
possibility of tooth Ankylosis
• Detect levels of periodontal bone at the interdental area
• Detect secondary caries

20. Occlusal Radiograph
• Occlusal radiographs are useful for demonstrating larger areas
of the mandible or maxilla than are normally demonstrated on
a periapical radiograph. They are useful when trauma has
occured to the anterior teeth.
• Two basic types of occlusal radiographs:
• 1)- Cross Section occlusal radiograph
• 2)- Topographic occlusal radiograph

21. CROSS SECTION RADIOGRAPH

22. • These radiograph are typically taken of the mandibular arch. A
film is placed between the occlusal plane of maxilla and
mandible emulsion side down.
• The patient closes softly and the head is tipped back as far as is
comfortable..
• Central beam is directed perpendicular to the film through the
floor of mouth.
• Faciolingula location of impacted teeth and foreign bodies
may be observed.
• Exposed time is about 0.3 second longer than for a molar
periapical radiograph.
• These radiographs are not recommended for maxillary arch

23. Topographic occlusal radiograph

24. • These radiographs are accomplished simply by using the
bisecting angle principle
• Large size no.4 film is used
• For young children of primary and mixed dentition ages no.2
film is more appropriate.
• When the size 2 film are used the procedure is sometimes
called “cracker bite” or cookie occlusal.
• Technique is ideal for young children

25. Localization Technique
• Is a method to locate the position of a tooth or object in the jaws.
• Purpose: to depict the B-L relationship or depth of an object.
• Two methods
1. Buccal object rule
2. Right angle technique

26. Buccal object rule
• Described by Clark in 1910 and refined and amplified by Richards in
1952 and 1980.
• According to this rule, when a radiograph is performed at a certain angle,
the object closer to the radiographic source – the buccal object – is
displaced in the radiograph in the same direction as the x-ray beam
• Stated more simply as INGLES RULE(MBD)- always shoot from mesial
and buccal root will be to the distal.

27. • With an orthoradial projection (A)
the two objects appear
superimposed.
• With an oblique projection (B,C)
the two objects cease to be
superimposed and easily become
recognizable when the angulation of
the X-ray machine is known
• The buccal object(the one closest to
the radiographic source) is displaced
in the same direction as the x-ray
source

29. • Given by Miller
• The periapical radiograph
shows impacted canine lying
apical to roots of lateral incisor and first premolar
• The vertex occlusal view shows that the canine lies palatal to
the roots of the lateral incisor an premlar
Right angle technique

30. Clinical situation for which
radiographs are indicated
 Positive Historical Findings
a. History of pain
b. history of trauma
c. Familial history of dental anomalies
d. Postoperative evaluation of healing
e. Previous periodontal or endodontic treatment
f. Unexplained tooth mobility

31. • Evidence of foreign objects
• Pain and/or dysfunction of the temporomandibular
joint
• Facial asymmetry
• Abutment teeth for fixed or removable partial
prosthesis
• Unexplained bleeding
• Unexplained sensitivity of teeth
• Unusual eruption, spacing or migration of teeth
• Unusual tooth morphology, calcification or color
• Unexplained absence of teeth
• Clinical erosion

32.  Positive Clinical Signs/Symptoms
• Deep carious lesions
• Swelling
• Evidence of dental/facial trauma
• Mobility of teeth
• Sinus tract (“fistula”)
• Clinically suspected sinus pathology
• Growth abnormalities
• Oral involvement in known or suspected systemic disease
• Clinical evidence of periodontal disease
• Large or deep restorations

33. GUIDELINES FOR
PRESCRIBING RADIOGRAPH

34. Age Consideration Radiograph
3-5 No apparent abnormalities (open contacts)
No apparent abnormalities (closed contacts)
Extensive caries
Deep caries
None
2 posterior bite wings, size
0 film
4-film survey
Selected periapical
radiographs in addition to
4-film survey

35. Age Consideration Radiograph
6-7 No apparent abnormalities
Extensive or deep caries
8-film survey (available by
7 years of age)
Selected periapical
radiographs in addition to
8-film survey
8-9
10-12
No apparent abnormalities or extensive or deep
caries
No apparent abnormalities or extensive or deep
caries
12-film survey
12 or 16 film survey
depending upon size

36. Four film survey:
Eight film survey:
Radiographic examinations

37. Twelve film survey:

38. Sixteen film survey:

39. Radiographic examinations
Four film
survey:
series consists of
a maxillary and
mandibular
occlusal
radiographs and
two posterior
bitewing
radiographs.
Eight film survey:
• This survey includes a
maxillary and
mandibular anterior
occlusal radiographs.
• Four molar periapical
radiographs.
• Two posterior
bitewings
Twelve film survey:
• This survey include
maxillary and
mandibular permanent
incisor periapical
radiographs.
• Four primary canine
periapical
radiographs.
• Four molar periapical
radiographs.
• Two posterior
bitewing radiographs
Sixteen film survey: This examination consists of the twelve-film
survey and the addition of four permanent molar radiographs.

40. • MODIFICATIONS FOR INFANTS
• Under 3 yrs age mother should hold both the child and film
• Child’s head cradled against parent shoulder
• Parent’s left arm should restrain the child’s body and right arm should
position and hold the film
• Type 0 film used

41. Management Techniques
• desensitize the child
• Using a "tell, show, do" technique.
• The child is positioned to gain maximum cooperation
• Make child to sit in the parent’s lap while the radiograph is exposed that reduces
child's anxiety.
• parent resting their arms around the child's upper body and their legs wrapped
around the child's lower body.

42. • Obtaining the least difficult radiograph first
• A positioning device such as a Snap-A-Ray
can be used to aid the parent in positioning
and securing the film
• If the child is uncooperative, then additional
restraint by a second adult may be
necessary. first adult restraining the child, a
second adult stabilizes the child's head with
one hand while the other hand positions the
x-ray holder in the patient's mouth.

43. • If a second adult is not available, it may be
necessary to place the child in a mechanical
restraining device (Papoose Board)
• If the child is still too uncooperative, it may
be necessary to manage the child
pharmacologically with inhalation, oral, or
parental sedatives.

44. • The Snap-A-Ray is also useful for those patients that
have a fear of swallowing the radiograph. By biting
on the large positioning device and watching in a
mirror they are assured they will not swallow the
radiograph.

45. Desensitization Techniques
• Desensitization is defined as gradually exposing the child to new stimuli or
experiences of increasing intensity
• Initially taking an anterior radiograph which is easier to tolerate than a
posterior radiograph.
• “Lollipop Radiograph Technique.”

46. • Procuring Posterior Radiographs
• Procuring posterior radiographs can be made more pleasant by associating
it with a pleasurable taste….bubble gum
• apply bubble gum flavored toothpaste to the film.
• Exaggerated gag reflex can be controlled by diversion and positive
suggestion
• Concentrating on something other than the procedure

47. • The patient can hum a song, raise a leg, or look at themselves in a mirror
• The patient's palate can be sprayed with a topical anesthetic
• use of nitrous oxide analgesia
• Another alternative method is placing the film between the cheek and the
tooth and exposing the film from the opposite jaw.

48. EXTRAORAL
RADIOGRAPHS

49. A technique for producing a single tomographic image of the facial structures
that includes both the maxillary and mandibular dental arches and their
supporting structures.
Panoramic Radiographs
This is a curvilinear variant of conventional tomography.
It requires a total of 15 to 22 seconds to record.
Although it is considered as a supplement it cannot substitute intraoral
radiographs in the diagnosis of caries or for viewing the periapical region.
This view can be useful in handicapped children and for viewing a wide
area of the TMJ and associated region.

50. Panoramic Radiographs

51. Panoramic x-ray unit 3. Intensifying screens

52. CASSETTE

53. BONY LANDMARKS IN MANDIBLE
53
1
1. Condylar head 2. Sigmoid notch 3. Coronoid process 4. External oblique ridge
5. Mandibular canal
2
3
4
5
6. Post. Border of Ramus 8. Lower border7. Gonial Angle
6
7
9. Mental ridge 11. Mental foramen10. Genial tubercle
13. Lingula
12. External Oblique Ridge
14. Hyoid bone
8
9
10
11
12
13

54. BONY LANDMARKS IN MAXILLA
54
15
15. Glenoid fossa
19. Floor of Max.Sinus
17. Zygomatic Arch16. Articular eminence 18.Post. wall max. sinus
20. Zygomatic process of max. forming innominate line
21. Hard palate 22. Floor of the orbit 23. Nasal septum 24. Incisive foramen
25. Inferior choncha 26. Meatus 27. Frontal process of Z.bone
16
17
18
19
20
21
22
23
29
25
24
26
28.Pterygo max. fissure
30. Maxillary tuberosity29.Spine of the sphenoid bone 31. Lateral pterygoid plate
31
30
28
27

55. OTHER STRUCTURES
55
32
32. External acoustic meatus 34. Shadow of ear lobe33. Styloid process
35. nose 36. Shadow of Cervical spine
33
34
35
36 37
37. Cervical vertebrae
38
38. Nasopharyngeal space 39. Shadow of uvula
40
39
40 Submandibular fossa

56. Indications
1.Determine the presence, shape and position of supernumerary teeth
2.Determine impaction of canines
3.Assess the extent of trauma to teeth and anterior segments of the arches
4.In case of trismus and trauma, where the patient cannot open the mouth
completely
5.Determine the medial and lateral extent of cysts and tumors.
6. To localize foreign bodies in jaws and stones in ducts of salivary glands.
7. To obtain information about the location, nature extent and displacement
of fractures of maxilla and mandible

57. • X- ray apparatus
• An image receptor
• Cephalostat
Cephalometric imaging system

58. • In orthodontic diagnosis & treatment planning
• In classification of skeletal & dental abnormalities
• In establishing facial types
• In evaluation of treatment results
• In predicting growth related changes & changes associated with
surgical treatment
• Valuable aid in research work involving the cranio-dentofacial
region
Uses of cephalogram

59. Goals of Cephalometrics
To evaluate the relationships, both horizontally and vertically, of the
five major functional components of the face:
• The cranium and the cranial base
• The skeletal maxilla
• The skeletal mandible
• The maxillary dentition and the alveolar process
• The mandibular dentition and the alveolar process

60. • Lateral cephalogram
 Also referred to as
lateral “cephs”
 Taken with head in a
standardized
reproducible position
at a specific distance
from X-ray source

61. Uses :
 Important in orthodontic growth analysis
 Diagnosis & Treatment planning
 Monitoring of therapy
 Evaluation of final treatment outcome

62. • Posteroanterior (p-a) cephalometric
radiograph
 Image Receptor and Patient Placement:
 Image receptor is placed in front of the
patient, perpendicular to the midsagittal
plane and parallel to the coronal plane
 The patient is placed so that the
canthomeatal line forms 10degree angle
with horizontal plane

63. • Position of The Central X-Ray Beam:
 Central beam is perpendicular to the image receptor,
directed from the posterior to anterior parallel to the
patient’s midsagittal plane and is centered at the level
of bridge of the nose.
• Resultant Image: the midsagittal plane should divide
the image into two symmetric halves. Superior border
of petrous ridge should lie in lower third of orbit.

64.  Uses :
 Provides information related to
skull width
 Skull symmetry
 Vertical proportions of skull,
craniofacial complex & oral
structures
 For assessing growth
abnormalities & trauma

65. Lateral Cephalogram
Hard tissue landmarks Soft tissue landmarks

66. Lateral oblique/bimolar radiograph
• Radiograph of molars and premolars using film/sensor positioned
beside the face
• Useful in
– difficult and uncooperative patient
– small children, mentally/physically disable patient
– Can tolerate with extraoral radiograph better than intraoral radiographs
• Beneficial in having a short exposure time
• Limitation – distortion of teeth
• Indication :
1. To Examine the posterior region of the mandible.
2. Patients who have fractures or swelling.
3. It evaluate the condition of the bone and to locate impacted teeth
or large lesions.

67. LATERAL OBLIQUE
• Cassette positioned against cheek and centered over the mandibular first molar
area.
• The patient presses the tube side of the cassette firmly against the cheek with
the palm of one hand and the thumb is placed under the lower edge of the
cassette.
• Head position tilted 10 to 20 degree towards the side to be examined and the
chin is protruded.
• The central ray directed toward the first molar region of the mandible from a
point slight underneath the opposite side of the mandible and directed as
perpendicular to the horizontal plane as possible

68. Postero – anterior view
-useful to evaluate the skull for any pathology, trauma or
developmental anomalies
-X ray beam directed from behind and through the skull.
Paranasal sinus view
-PNS View or Water’s projection
-Indicated in the visualization of paranasal sinuses, orbits &
-zygomatico- frontonasal sutures
Reverse-town projection
-used in case of condylar neck fractures
-Taken in open mouth position

69. Digital radiography

70. • Xeroradiography
• RadioVisiography
• Subtraction radiography
• Computed tomography
• Cone beam computed tomography
• Tuned aperture computed tomography
• Magnetic resonance imaging
• Ultrasound imaging

71. DIGITAL RADIOGRAPHY
• It is a method of capturing a radiographic image using sensor, breaking it
into electronic pieces and presenting and storing the image using a sensor.
• DIRECT DIGITAL IMAGING- a digital sensor used
CCD
CMOS
• INDIRECT DIGITAL IMAGING-Uses film like photo phsphor plates that
are activated using X-rays, then scanned in special devices that read the
images from the plate.

72. Advantages of digital radiography
over conventional radiography
• Working time reduced.
• Chemical processing is avoided.
• Exposure to radiation is reduced.
• Cephalometric meaurements and analyses can be more easily
performed with the aid of task dependent software.
• Storage and communication are electronic

73. Xeroradiography
• Records images without film
• Consist of images receptor plates- selenium particles
• Latent image is converted to a positive image- process called
develpment in processing unit.
Advantages
• Reduced radiation dose
• Image can be produced in 20 seconds
• Edge enhancement effect.
• Ability to have both positive and negative prints

74. • Improves visualization of files and canals.
• Two times more sensitive than conventional D-speed films.
Disadvantage
• Exposure time varies according to the thickness of plate

75. Radiovisiography
• Introduced by Mouyen et al in 1989.
• Radio part sensor- Exchangeable
scintillation
screens
- A fibre optic
miniature CCD
device
• Visio part- stores and converts point by
point into one of 256 gray scales.
• Graphy Part

76. • This system is capable of rapidly displaying a digital
radiographic image on a monitor with a 80% radiation dose
reduction when compared with conventional radiography
• The major components of the RVG system include an X-ray
head with an advanced timer, a radiographic sensor connected
to a charged coupling device (CCD), a monitor for image
display, and a computer with the appropriate software for
image storage and manipulation. One of the software’s
features allows the operator to vary the contrast.

77. Merits
• The image processing time is very short being about 5
seconds.
• Sensors can be easily moved from operatory to operatory ,
allowing the operators to work with a minimum number of
sensor and within a computer network enviornment.
• The problems that can be caused through processing faults
are eliminated.
• It gives opportunity to enhance the images for more precise
viewing.

78. Demerits
• They are thicker than films and cables running off the
sensor which some patients don’t tolerate well.
• The high cost of sensor
• Difficulty in placing sensor due to its rigidity.

79. Computed tomography
• CT has evolved into an
indispensable imaging method
in clinical routine.
• Non –invasively acquires
images
• Not biased by superimposition
of anatomical structures
• CT yields images of much
higher contrast compared with
conventional.

81. Tomographic views used to examine various facial structures:
• Tomography of sinuses:
- more precise evaluation of sinus
pathologies
-sphenoidal and ethmoidal sinuses are
more clearly visualized
• Tomography of facial bones, to study facial fractures, extent of orbital
blow out fracture
• Tomography of mandible
• Tomography of temporomandibular joint

82. Cone –Beam Computed Tomography
• CBCT is an X-ray imaging approach that provides high
resolution 3-dimensional images of the jaws and teeth
• CBCT shoots out a cone shaped X-ray beam and captures a
large volume of area requiring minimal amounts of generated
x-rays.
• Within 10 seconds, the machine rotates around the head and
captures 288 static images.

83. Advantages
• Precise identification and detection of periapical lesions
• Detection of mandibular canal
• Complete 3-D reconstruction and display from any angle.
• Patient radiation dose 5 times lower than normal CT
• Excellent resolution
• Require only a single scan to capture the entire object with reduced
exposure time.
• Less expensive than CT

84. Magnetic resonance imaging
• non-invasive technique in which high strength static magnetic field pulse
radio waves are used
• used to image the head, neck & the musculoskeletal system
• also used in the neoplasm of maxilla & mandible & evaluation of lymph
nodes

85. Radiation Hazards and Protection

86. X- ray Dose Measurements
X- ray Dose Units

87. Radiation Absorbed Dose
• This is a measure of the amount of energy absorbed
from the radiation beam per unit mass of tissue
• Unit of measurement:
• SI unit : Gray, (Gy) measured in joules/kg
• original unit : rad, measured in ergs/gm
• 1 Gray = 100 rads

88. Equivalent Dose
• equivalent dose = radiation absorbed dose (Gy)×
Q
• Since Q for x -ray = 1, then
equivalent dose = radiation absorbed dose
(Sv) = (Gy)

89. Effective Dose
• Each body tissue is affected differently by
radiation
• Effective dose: This is a measure that allows doses
from different investigations of different parts of
the body to be compared , by converting all doses
to an equivalent whole body dose

90. Weighing Factor (W)
• Measures the radiosensitivity, i.e.the risk of the
tissue being damaged by radiation.
• The higher the damage, the higher is W

91. Weighing factors for different body tissues
Tissue Weighing factor
Testes and ovaries 0.20
Red bone marrow, colon, lung,
stomach
0.12
Breast, bladder, liver, thyroid 0.05
Bone surfaces , skin 0.01
Remainder 0.01

92. Effective Dose
• Effective dose = equivalent dose × weighing factor
= radiation absorbed dose(Gy)×Q ×W
• SI unit : Sievert (Sv)
• subunit : millisievert (mSv)
• Effective dose (whole body) = sum of W

93. Biological Effects of X-ray

94. Radiobiology
The response of living systems to ionizing radiation
-X-Rays interact with living tissues and can cause
biological changes.
-These changes are mediated directly by excitation or
ionization of atoms or indirectly as a result of chemical
changes occurring near the cells.
-Affected cells may be damaged or killed.
Biological Effects of X-ray

95. Biological Effects of X-ray (cont’d)
• Genetic effects involve chromosomal damage or mutation in the
reproductive cells and will affect future generations.
• Somatic effects involve damage to other tissues and result in
changes within the individual’s lifetime (e.g. radiation burns,
leukemia).
• Radiation is a particular hazard because its effects are painless,
latent and cumulative

96. Ionization
The process of removing an electron from an electrically neutral
atom to produce an ion. An ion is an atom or subatomic particle with
a positive or negative charge.
Reduction of x-ray beam intensity (that reaches film) by interaction
with matter.
1. Coherent scattering
2. Compton scattering
3. Photoelectric absorption
Attenuation

97. Coherent Scattering
Low-energy x-ray interacts with outer-shell electron and
causes it to vibrate briefly. Scattered x-ray of same energy
as primary x-ray is then emitted, going in a different
direction than primary x-ray. Electron not ejected from
atom. (No ionization).

98. Compton Scattering
Outer shell electron ejected
Scatter radiation result
Occurs majority of the time
30% of scatter exits head

99. Photoelectric Absorption
Inner-shell electron ejected
(Ionization)
Complete absorption

100. threshold
linear
non-linear
non-threshold
Response
Dose
Linear: the response is directly related to
the dose.
Non-linear: the response is not
proportionate to the dose.
Threshold: the dose at which effects are
produced; below this dose, there are no
obvious effects.
Non-threshold: any dose produces a
response.
Dose-Response Curves

101. Biologic Effects Of Ionizing Radiation
Stochastic
• The probability of occurrence of
the change, rather than its
severity, is dose dependant
• All or none, the person either has
the condition, or not
• No threshold
e.g.
• Radiation induced cancer, greater
exposure of population to
radiation increases cancer
probability, but not its severity
Deterministic
• The severity of response is
proportional to the dose
• Occur in all people when the dose
is large enough
• There is a dose threshold below
which the response is not seen
e.g.
• Oral effects after radiation therapy
• Radiation sickness after whole
body radiation

102. Radiation Hazards
Nuclerar boms
nueclear reactors leaks
Whole body
radiation
Medical
(diagnostic & theraputic)
Dental
X- rays
Specific area
radiation
Radiation exposure

103. Radiation Hazards
Indirect Direct
Somatic
Affects individual
No effect on offspring
Genetic
Do not affect individuial
Offspring is affected
Radiation damage

104. Radiation Hazards
Direct Damage
RH +Radiation R
+
+ H
+
+ e
-
R
+
Dissociation
R
+
X + Y
Cross-linking
R
+
+ S RS

105. Radiation Hazards
Direct Damage
Radiation
• DNA /RNA molecule nuclear acid
breakdown
• Nuclear acid breakdown
Somatic cells radiation induced
malignancy
Genetic cells radiation induced
congenital abnormality

107. Radiation Hazards (indirect damage)
Water Hydrolysis
• H 2 O H
+
+ OH
-
• H
+
+ H
+
H2
• OH
-
+ OH
-
H 2 O 2
Radiation

108. • H2O2 + DNA Molecular
breakdown
• H2O2 + Proteins
• Molecular breakdown Cell damage
Radiation Hazards (indirect damage)
Water Hydrolysis

109. Factors Affecting Radiosensitvity
• Dose: the amount of radiation
received. The higher the dose,
the greater is the effect
(consider the threshold)
• Dose rate: the rate of exposure.
e.g. a total dose of 5Gy can be
given as
- 5Gy/min (single dose) is more
destructive
- 5mGy/min(fractionized), less
destructive, injured cells can
recover
• Oxygen: the higher the O2
level in irradiated cells, the
greater is the damage. (H2O2
formation)
• Linear Energy Transfer
(LET): the rate of loss of
energy from a particle as it
moves in its track through
matter (tissue)
e.g. alpha particles vs. X-ray

110. Protection for the operator
• Effort must be made so that operator can leave the room or
can take a suitable position behind a barrier
• If there is no barrier operator should use lead aprons
• The film should never be held by the operator . Ideally film
holding devices should be used . If correct retention or
placement is still not possible a parent must hold the film
in the position.
• There should be no use of fluroscent mirrors in the oral
cavity

111. Operator Location
The operator of the dental unit must stand at
least six feet from the useful beam or behind
a protective barrier. [Stand at an angle of from 90 to 135
degrees from the central ray. Do NOT stand in the
path of the primary x-ray beam.]
If a protective barrier is used, it must have a
viewing window to allow the operator to see
the patient.

113. Personnel Radiation Badges
Use of film badge/ TLD badge / pocket dosimeter , for personnel
radiation monitoring to avoid accumulate over exposure.

114. Protection of others
No one but the patient should be in the exam room
during x-ray exposures. If a person’s presence is
necessary for the performance of the examination,
that person must be behind a shield or wearing a lead apron.
He/she must not be in line with the primary
beam, and should stand at least six feet from the
x-ray tube if feasible. He/she must also be at least
18 years of age and not be pregnant.

115. Protection for the Patient

116. Required Distances
If the dental unit can operate above 50 kVp, the source to skin
distance must be at least 18 cm [7 inches].
Use of long source to film distance of 40 cm (16 inches), rather
than short distance of 20 cm, decreases exposure by 10 to 25
percent, distances between 20 cm to 40 cm are appropriate, but
the longer distance are optimal.

117. Filtration Requirements
The amount of filtration required varies with the
operating range of the x-ray unit. For example:
For 51 to 70 kVp units* 1.5 mm Al [HVL]
Units above 70 kVp 2.1 or more Al
*Note: Settings below 65 kVp are not recommended
because of higher patient exposure.

118. Collimators
Collimators limit the size and shape of the
useful beam which reaches the patient.
The x-ray field must be limited to a circle
having a diameter of no more than 7 cm [~3 in].
Rectangular collimators are recommended for
periapical radiographs as their use significantly
reduces the area of the patient’s body that
is exposed to radiation

119. Cones
The ADA discourages the use of short, closed,
pointed cones because of the increased
scatter radiation close to the face and adjacent
areas of the patient’s body.

120. Thyroid
The thyroid gland, especially in children, is
among the most radiosensitive organs.
Even with optimum techniques, the primary
dental beam may pass near or occasionally
through the gland. A thyroid shield may
reduce the dose to the gland without
interfering with obtaining a diagnostic image.

121. Lead aprons and shields
- Even though the dose from digital
radiography is less than convention
radiography, patients should be
shielded with lead aprons and
thyroid shields.
-These shields should have at least
0.5 mm of lead equivalent.
-Do not fold or bend aprons. Hang
aprons to prevent damage and loss
of protective qualities.

122. • The dentist should use every means to reduce unnecessary
exposure to their patients and themselves. This philosophy of
radiation exposure is often referred to as principle ALARA-
As Low As Reasonably Achievable
• The exposure to ionizing radiation should be kept as low as
reasonable achievable by considering all economic and social
factors

123. • Improper placements of films.
• Cone cutting
• Incorrect horizontal angulations
• Incorrect vertical angulations
• Over exposure due to defective devices.
• A high exposure of the patient to radiation because of
repetition of taking X-rays due to an uncooperative child.
Probable Technical Errors

124. References
1)-McDonald RE, Avery DR, Dean JA. Dentistry for th child and
adolescent, 8th edn. Mosby, 2004 :117-28
2)-Tandon S. Textbook of pedodontics, 1st edn. Paras Publishing, 2001
:19-28
3)-Damle SG. Textbook of pediatric dentistry, 1st edn. Arya Publishing
House, 2000 : 167-71
4)-Oral Radiology- Principles and Interpretataion
- White and Pharoah
5)-Textbook of Dental and Maxillofacial Radiology
- Freny R Karjodkar
6)-Essentials of Dental Radiography and Radiology
- Eric Whaites

125. THANK YOU