basics of radiology in pediatric practice including digital radiography and radiation safety & protection

1. ““RADIOGRAPHY IN
PEDIATRIC DENTAL
PATIENT””

2. CONTENTS
 Introduction
 History of X-ray in dentistry
 Guidelines for prescribing radiographs
in children
 Behavioural consideration and
management techniques
 Radiographic techniques
 Newer digital radiographic techniques
 Radiation safety and protection
 Technical errors
 References

3. Introduction
 Definition- radiology
 Plays a vital role in the diagnosis and treatment planning .
 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.

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

5. Dr. Edmund Kells of New Orleans,
Louisiana.

6. Dr Kells used impression
compound to stabilized the film
during exposure

7. 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

8.  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

9. • 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

10. Radiographic Examination
 Four film series: This series consists of a
maxillary and mandibular occlusal radiographs and
two posterior bitewing radiographs.

11. Eight film survey:
This survey includes a maxillary and mandibular anterior
occlusal radiographs. Four molar periapical radiographs.
Two posterior bitewings

12. 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

14.  Sixteen film survey: This examination consists of
the twelve-film survey and the addition of four
permanent molar radiographs.

15. GUIDELINES FOR
PRESCRIBING
RADIOGRAPH
Guidelines for prescribing dental radiograhs for infants,
children and adolescents and persons with special health
care needs ; Ad Hoc committee on pedodontic radiology

16. 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

17. 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

18. Dental X-Ray Machine

19.  Factors controlling X-Ray beam
1. Tube Current (mA)
2. Tube Voltage (kVp)
3. Exposure time

20. Operating
kilovoltage
Milliampere - Seconds
D E
low High Mean Low High Mean
70 6.7 10.9 8.8 3.6 4.8 4.2
90 3.1 10.9 4.6 1.7 2.6 2.2

21. Exposure time in pediatric patients
Tooth Time in
Miliseconds(mS)
Maxillary 2nd
molar 520
1st
molar 440
Canine 370
Incisor 280
Mandibular 2nd
molar 440
1st
molar 380
Canine 310
Incisor 280

22. X-Ray Films

24. SPECIAL
CONSIDERATIONS IN
YOUNG CHILD
 Introduce him to the “camera”
 Tell-show-do
 Careful words to describe the procedure
 Easiest region first
 Topical L.A. in case of exaggerated gag reflex
 Patience for repeated attempts
 Voice control, firmness & TLC
 Special handling for alternatively abled children

25.  If the child, less than three years of age it may be
necessary for the child to sit in the parent’s lap while the
radiograph is exposed.

26.  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.

27.  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.
 If a second adult is not available, it may be necessary to
place the child in a mechanical restraining device (Papoose
Board) to adequately restrain the child.
 If the child is still too uncooperative, it may be necessary to
manage the child pharmacologically with inhalation, oral, or
parental sedatives.

28.  Older children may also be uncooperative for a variety of reasons.
 These can range from the jaw being too small to adequately
accommodate the radiograph, fear of swallowing the radiograph,
fear of the procedure itself, or the patient exhibits a severe gag
reflex.
 For the child with the small mouth, use the smallest size film
available (size 0 film). Roll the film (do not place sharp bends) to
allow the film to accommodate the shape of the jaw and not impinge
on the soft tissues.

29. Positioning the Radiograph
 vertical radiograph
 By biting on the large positioning device and watching in
a mirror they are assured they will not swallow the
radiograph

30.  A self sticking sponge tab may also reduce
impingement of the radiograph on the intraoral
soft tissue.

31.  Desensitization Techniques
Desensitization is defined as gradually exposing
the child to new stimuli or experiences of
increasing intensity.

32.  Another example of desensitization is the “Lollipop Radiograph
Technique.” The child is given a lollipop to lick (preferably
sugarless).
 After a few licks, the lollipop is taken from the child and a
radiograph is attached to the lollipop using an orthodontic
rubber band. The lollipop with the attached film is returned
to the child, who is told to lick the lollipop again.
 After a few licks, the child is told to hold the lollipop in his
mouth while we take a tooth picture. The exposure is made.

33. Procuring Posterior Radiographs
 Procuring posterior radiographs can be made more pleasant
by associating it with a pleasurable taste….bubble gum.
 Before placing the radiograph in the patient’s mouth apply
bubble gum flavored toothpaste to the film. The child will be
more accepting of the radiograph.

34. Managing gag patients
 The easiest is through diversion and positive suggestion.
 The operator suggests to the patient the gag reflex can be
reduced by concentrating on something other than the
procedure.
 The patient’s palate can be sprayed with a topical anesthetic
to reduce the sensation of the radiograph on the palate and
tongue.
 An alternative is the use of nitrous oxide analgesia.

35. Bent film radiographic
technique
 Used in young children who can not tolerate placement
of film inside their mouth
 Pt bite on the film that has a sharp right angle bend at
the top, bent part serves as a self contained bite tab
to hold the film in the place.
 Instruct the child to softly bite down to avoid cusp
marks and distortion on the film
 Stick on foam tabs are also available for use
 1 to 2 size films are used
 Straighten the film for processing

36.  Another alternative is to place the radiograph in such a
manner to not come in contact with the palate or tongue.
 This is accomplished by either extraoral placement of the
film or placing the film between the cheek and the tooth and
exposing the film from the opposite jaw.
 The film side of the packet (the solid color side) is facing the
buccal surface of the tooth.

37.  The x-ray head is placed at the opposing side, and the cone is
positioned under the angle of the ramus on the opposite side.
 As the x-ray beam is traveling a longer distance to the film
than in the typical positioning, it is necessary to double the
exposure time.
 It is imperative that after mounting radiographs are
reversed.
 Incorrect mounting and labeling of the reverse radiograph
can result in misdiagnosis and treatment of the wrong tooth.

38.  It is difficult to take intraoral radiographs in patients who are
intolerable to place films in their mouth. For these patients ,
Newman and Friedman recommended a new technique of
extraoral film placement.
Extraoral periapical radiography : an alternative approach to
intraoral periapical radiography: Rahul Kumar, Neha Khambete;
Imaging Science in Dentistry; 2011;41 :161-5

39. Techniques
 Paralleling Technique
 Bisecting Angle Technique

40. Parallelling Technique

41. Bisecting angle Technique

42. Difference
Bisecting angle technique Parallel technique
Image shape distortion Slight image size distortion
Superimposition of zygomatic
process
Control of shadow of zygomatic
process
Anatomical relationship altered Correct anatomical relationship
Crown- root ratio is not preserved Crown-root ratio is preserved
Poor image standardization and
reproducibiliy
High image standardization and
reproducibility

43.  Paralleling technique has geometric advantage over
the bisecting angle technique It has comparatively
less distortion. Errors are more likely to occur in
bisecting angle technique and leads to more
patient exposure due to frequent retakes.
However , bisecting angle technique is more
appropriate when it comes to patients comfort and
more recommended in pediatric population
Comparison of paralleling and bisecting angle technique in
endodontic working length radiography;M Fahim Ibrahim,Malik
Salman Azif; Pakistan oral & dental Journal;2013; vol 33 ;160-164

44. 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

45. 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..

46.  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

48. Right angle technique
 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
A labially positioned mesiodens: A case report ; Robert J Henry,
A Charles Post; Pediatric Dentistry ;March 1989- vol 11:59-62

49. Radiographic
techniques
commonly used in
children
Intraoral
 Intra oral periapical
 Bite wing
 Occlusal

50. 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

51. Posterior maxillary
+30 degree
Posterior mandibular
- 10 degree
Anterior maxillary
+45 degree
Anterior mandibular
-15 degree

52. Bitewing Radiograph
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

54.  Horizontal or vertical

55. The baseline examinations and intervals to the next
bitewing examination in children.
Baseline bitewing
examination
Interval to next bitewing examination
At age: Low caries risk High caries risk
5 years 3 years 1 year
8 or 9 years 3-4 years 1 year
12 to 16 years 2 years 1 year
16 years 3 years 1 year

56. Occlusal radiograph
 The occlusal technique is used to examine large
areas of the upper or lower jaw.
 In the occlusal technique, size-4 intraoral film is
used. The film is so named because the patient
bites, or “occludes,” on the entire film.
 In adults, size-4 film is used in the occlusal
examination.
 In children, size-2 film can be used.

57. 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

58. Extraoral technique
RADIOGRAPHY OF PARANASAL SINUSES
1. Standard Occipitomental Projection
2. Modified method (30 degree OM)
3. Bregma Menton
4. PA Water’s
RADIOGRAPHY OF MANDIBLE
1. PA Mandible
2. Rotated PA Mandible
3. Oblique lateral radiography
I. True laterals
II. Oblique laterals
III. Bimolars (two oblique laterals on one film).

59. RADIOGRAPHY OF BASE OF SKULL
Submento-vertex projection
RADIOGRAPHY OF ZYGOMATIC ARCHES
Jughandle view (A modification of submentovertex view)
RADIOGRAPHY OF TEMPOROMANDIBULAR JOINT
1. Transcranial Projection
2. Transpharyngeal projection
3. Transorbital projection

60. RADIOGRAPHY OF THE SKULL
1.Lateral Cephalogram
2.True lateral (Lateral Skull)
3.PA Cephalogram
4.PA Skull
5.Towne’s projection
6.Reverse Towne’s projection

61. Panaromic Radiograph
 Most common.
 It is a technique for producing a single tomographic
image of facial structures that includes both
maxillary and mandibular arches and their supporting
structures.
This is curvilinear variant of conventional tomography
and is also used 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 which the object of interest is located

62. Indications
 Diagnose missing and supernumerary teeth,
 Detect gross pathoses,
 Asses development of the dentition,
 Estimate the dental age of the patient,
 Detect bone fractures, traumatic cysts,
 Detect anomalies,
 In some patients with disabilities (if the patient can sit in a
chair and hold head in position).

64.  Periapical radiograph allowed the assessment of
periapical status of 87% of teeth whereas only
57.6% and 34% of teeth could be appraised using
digital panaromic images displayed on monitor and
glossy paper respectively.
 Teeth are best viewed on periapical radiographs
except maxillary second and third molar which are
better viewed on OPG
Radiological assessment of periapical status using the periapical index:
Comparison of periapical radiography and digital radiography; william
et. Al,International Endodontic journal 2007;Vol 40; 6: 433-440.

65. Interpretation
 Raised dot toward your eye
(identification dot on tube side)
 Imagine the x-ray in your mouth by
keeping the identification dot
bucally and decide the side.
 First mention the area of oral cavity
visible on radiograph.
 Followed by area of interest .
 Identify normal anatomic landmarks
 Knowledge of normal v/s abnormal
 Attention to all regions on the film
systematically
 One anatomic structure at a time

66.  Teeth present
-Stage of development
-Position
 Condition of crowns
-caries
- restorations
 Condition of root
-length
-resorption
-crown:root ratio
 The apical tissue
- integrity of lamina dura
-any radiolucency or radiopacity associated with apical area
 Periodontal tissue
- width
-level of quality of crestal bone
-vertical and horizontal bone loss
-furcation involvement
 Bone – density, trabecular pattern

67.  Describing the lesion
1. size
2. shape
3. location
4. density
5.internal architechture
6.effect on adjacent structure

68.  Measurements were carried out at 52 X-ray units for all types of
intraoral examinations performed in clinical routine. Not all X-ray units
have pre-set child exposure settings with reduced exposure time or in
some cases lower tube voltage. Child examinations are carried out using
adult exposure settings at these units, which increases the exposure
values by up to 50%. For example, values for periapical examination
ranges from 14.4 to 40.9 mGy cm2
for child settings and 20.6 to 48.8
mGy cm2
when the adult settings are included..
Radiation exposure to children in intraoral dental radiology
H. K. Looe,A. Pfaffenberger,N. Chofor ; Radiation protection
Dosimetry, vol 121, issue 4,461-465

69.  All the three methods of working length determination used
in this study were found to be reliable and accurate for use
in deciduous molars.
 Overall the three techniques show a greater reliability in
mandibular molars. Since all techniques are comparable it
may be concluded that weighing the advantages and
disadvantages of each technique and based on operator’s
preference any of the methods can be used for determining
the working length in deciduous molars..
Comparison of Root ZX, RVG and Conventional Radiography to
determine working length in roots of primary molars : Archana A
Thomas, Dr Shobha Tandon

70.  Total of 320 premolars were examined. Of these, 218
(68%) were maxillary premolars and 102 teeth (32%) were
mandibular premolars. All the premolars in the sample had no
obvious caries, occlusal malformations, or any restorations.
 1.Diagnodent gave similar sensitivity values but lower specificity
compared to visual-tactile examination in diagnosing occult dentinal
caries.
 2. There were no significant differences between conventional or
digital radiography in diagnosis of occult dentin caries.
 3. Although the diagnosis of occult dentinal caries may be further
enhanced by the Diagnodent, a combination of visual-tactile
examination and either conventional or digital radiography should
suffice in most cases.
Visual-tactile Examination Compared With Conventional Radiography,
Digital Radiography, and Diagnodent in the Diagnosis of OcclusalOccult
Caries in Extracted Premolars. Michael J. Chong, BDSc, MDSc, W. Kim
Seow, BDSc, MDSc,pediatric dentistry 2003, 25-29

71. Part 2
Digital radiography and
radiation protection

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

73. 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.

74. 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

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.  The periapical areas of 16 teeth from 6 human mandibular jaw
specimens were randomly examined by 3 observers using
conventional radiography with Kodak E-speed film and
radiovisiography (with variable contrast and with fixed contrast).
 results showed that conventional radiography and
radiovisiography (variable contrast) have opposite strengths.
Conventional radiography tended to be more accurate in the no
lesion condition, whereas radiovisiography using variable contrast
was somewhat more accurate in the smallest lesion condition. The
accuracy of radiovisiography with fixed contrast was not
significantly different from the other two methods..
RadioVisiography in the Detection of Periapical Lesions ,John E.
Sullivan, Jr., DDS, MS, Peter M. Di Fiore, Journal of
endodontics,2000 , vol 26:65-69

80. 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

81.  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
Xeroradiography and its application to dentistry
Thomas Katsanulas, 'Theodor Lambrianidis
Department of Dental Pathology and Therapeutics, Greece:March 22, 1989.

82. Digital subtaraction
radiography
 This is a method by which structured noise is
reduced in order to increase the detectability in
the radiographic pattern.
 “Image – enhancement method” – area under focus
displayed aaginst a neutral background

83.  Standard radiographs are produced with identical
exposure geometry.
 Reference/baseline images
 Follow up image for comparison.
 If there is change in the radiographic attenuation
between the baseline and follow up examination, this
change shows up as a brighter- if there is gain
And as a darker area , when change represents Loss
 The strength of digital substraction radiograph is
that it cancels out the complex anatomical
background against which this change occurs.

85. Application
 Useful in detecting progress of remineralization
and demineralization, pattern of dentinal caries,
diagnostic of incipient caries.
 Assess success of root canal treatment detecting
periapical lesion.
 90% accurate in detecting as little as 5% mineral
loss as compared to conventional radiograph (30-
60% loss)

86. 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.

88. 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

89. Advatages
 Eliminates the super-imposition of images of
structures outside the area of interest.
 Because of the inherent high-contrast resolution
of CT differences between tissues that differ in
physical density by less than 1% can be
distinguished.
 Very small amount difference in the X-ray
absorption can be detected

90.  Excellent differentiation between different types
of tissues both normal and diseased
 Images can be manipulated
 Changes in the linear and volumetric measures can
be determined by sequential scans
 Images can be enhanced by the use of IV contrast
media providing additional information

91. Disadvantages
 Since the pixels that form the image represents discrete
subdivisions of space, the effect of blurring is much greater
than in conventional radiographs
 Tissue non-specificity i.e. Have ability to highlight any
particular organ/tissue.
 Cost concerns..
 Metallic objects , such as restoration may produce streak or
star artefacts across the CT image.
 Need for contrast media for enhanced soft tissue contrast.
 Inherent risks associated with IV contrast agents

92. 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.

93. 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

94.  Phantom, armed with lithium fluoride thermoluminescent
dosemeters (TLDs) was exposed using a set of four
conventional radiographs (orbital view, modified Waters
view, orthopantomography, skull posterior–anterior), two
different cone beam computed tomography (CBCT) , and
multislice computed tomography (CT) modalities
 Results: Multislice CT showed the highest exposure values.
Exposure levels of the CBCT systems lay between CT and
conventional radiography. Dose measurement for the 16-slice
CT revealed nearly the same radiation exposure as the 4-
slice system when adapted examination protocols were used..
Radiation exposure during midfacial imaging using 4- and 16-slice
computed tomography, cone beam computed tomography systems and
conventional radiography; D Schulze, M Heiland, H Thurmann,
Dentomaxillofacial Radiology (2004) 33, 83–86

95. Tuned Aperture Computed
Tomography (TACT)
 Improve accuracy in caries diagnosis because of
its 3-D or pseudo 3-D capabilities.
Principle of TACT
 TACT slices can be produced from an arbitary
number of X-ray projections, each exposed from a
different angle.
 Using TACT , it is possible to use one X-ray source
and move it through several points in space or use
several fixed sources to collect multiple X-ray
projections which in turn can be processed to
produce TACT slices

96. Generalized TACT
projection applied to a
simple cylinrical object

97. TACT useful in
 Detection of caries and recurrent caries
 Periodontal bone loss
 Periapical lesion localization
 TMJbone change

98. Magnetic Resonance
Imaging
Principles
 Magnetism is a dynamic
invisible phenomenon
consisting of discrete fields
of forces.
 Magnetic fields are caused
by moving electrical charges
or rotating electric charges.
 Images are generated from
protons of the hydrogen
nuclei.
 Essentially imaging of the
water in the tissue

99.  When images are displayed ; intense signals show
as white and weak ones as black nd intermediate
shades of gray.
 Cortical bone and teeth with low presence of
hydrogen are poorly imaged and appear black.
Role of Magnetic Resonance Imaging in dentistry : C
D nayak, S S Pagare, scientific Journal 2009 vol3 :67-
69

100. Application
 Inflammatory and neoplastic lesion of the
nasopharynx, salivary glands, paranasal sinuses.
 Diagnosis of internal derangement of TMJ due to
its ability to define cartilaginous disk.
 Can differentiate between solid and cystic lesions
 Perineural spread of a tumour by branches of
trigeminal and facial nerve.

101. Advatages
 It offers the best resolution of tissues of low
inherent contrast.
 No ionizing radiation is involved with MRI.
 Direct multiplanar image is possible without
reorienting the patient.
Disadvantages
 Long imaging time
 Potential hazards imposed by the presence of
ferromagnetic metals in the vicinity of the imaging
magnet.

102. Ultra Sound Scanning
 Ultra high frequency sound waves are used.
 The reflected sound waves are converted to an
electrical signal that is amplified , processed and
ultimately displayed on a monitor.
 US waves are generated by a quartz or synthetic
ceramic crystal when it is exposed to an altering
current of 3-10 Mhz as a result of the
piezoelectric effect, the crystals distributes US
waves oscillating at the same frequency

103.  US image produced – automatic movement of the
crystals over the tissue of interest.
 As each movement gives one images of this tissue
(depending on its plane) and there is a frequency
of 30-50 images per seconds, they appear in a
screen as moving images.
 Useful adjunct to conventional radiography in the
management of extensive periapical lesions , as it
provides specific information on the size of the
lesion

104. Any exposure, however
small it may be , can produce
harmful effects

105. Radiation safety
and Protection
Primary biologic effects of radiation:
 Deterministic effects
 Stochastic effects

106. Source of the radiation in
dental radiology department
 Primary beam- radiation originating from focal
spot
 Secondary radiation-originating from irradiated
tissue of patient.
 Leakage or stray radiation-radiation from X-ray
tube hea positioning
 Scattered radiation – from filters and cones,
coming from objects other than patient such as
walls and furnitures that the primary beam may
strike

107.  Means of protection can be divided into:
1. Protection for operator
2. Protection for patient

108. 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

109. 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.

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

112. 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.

113. Protection for the Patient

114. 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.

115. 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.

116. 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 radiationis exposed to radiation

117. 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.

118. System Speed
Faster image receptor
systems result in
decreased radiation
exposure to the
patient

119. 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.

120. 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..

121.  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- AAss LLowow
AAss RReasonablyeasonably AAchievablechievable
 The exposure to ionizing radiation should be kept
as low as reasonable achievable by considering all
economic and social factors

122. ReferencesReferences
McDonald RE, Avery DR, Dean JA. Dentistry for th child
and adolescent, 8th
edn. Mosby, 2004 :117-28
Tandon S. Textbook of pedodontics, 1st
edn. Paras
Publishing, 2001 :19-28
Koch G. Pediatric dentistry, 1st
edn. Munksgaard, 2001 :
99-11
Mathewson RJ, Primosch RE. Fundamentals of pediatric
dentistry 3rd edn. Quintessence Publishing Co. Inc
1995: 35-55
Damle SG. Textbook of pediatric dentistry, 1st
edn. Arya
Publishing House, 2000 : 167-71

123.  Oral Radiology- Principles and Interpretataion
- White and Pharoah
 Textbook of Dental and Maxillofacial Radiology
- Freny R Karjodkar
 Essentials of Dental Radiography and Radiology
- Eric Whaites
 Bramanet CM, Berbert A. A critical evaluation of some
methods of determining tooth length. Oral Surg 1974; 37:
463.
 Forsberg J. Radiographic reproduction of endodontic
“working length” comparing the paralleling and the bisecting-
angle techniques.Oral Surg Oral Med Oral Pathol 1987; 64(3):
353-60.

124. • Langland OF, Langlais RP, Preece JW. Principles of dental
imaging. In: Langland OF, Langlais RP, Preece JW.
Intraoral radiographic techniques. 2nd ed. Philadelphia:
Lippincott Williams & Wilkins, 2002: 91-97.
•
•Jhon PR. Essentials of Dental Radiology. In: Jhon PR.
Intraoral radiographic techniques and indications of
intraoral radiographs.1st ed. New Delhi: Jaypee Brothers,
1999: 75-81.

125. Thank you.!