benefits of using radiology in pediatric dentistry outweigh the risks. Radiographs are a valuable diagnostic tool that can help to improve the oral health of children.
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 (detection of
dental caries cysts, tumors or any other major
craniofacial disorders) , treatment planning
and also aids in the assessment of growth and
development.
4. Indications of radiographs in children
• Positive Findings
– History of pain
– History of trauma
– Familial history of dental anomalies
– Postoperative evaluation of healing
– Previous periodontal or endodontic treatment
– Unexplained tooth mobility
5. 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
6. • 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
7. Radiographic Examination
• Four film series:
– This series consists of a maxillary and mandibular
occlusal radiographs and two posterior bitewing
radiographs.
8. • Eight film survey:
– This survey includes a
• maxillary and mandibular anterior occlusal radiographs
• Four molar periapical radiographs
• Two posterior bitewings
9. • 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
10. • Sixteen film survey:
– This examination consists of the twelve-film
survey and the addition of four permanent molar
radiographs.
11. 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 revised in
2009
12. Age Consideration Radiograph
3-5 No apparent abnormalities (open contacts) None
No apparent abnormalities (closed contacts) 2 posterior bite wings, size 0 film
Extensive caries 4-film survey
Deep caries Selected periapical radiographs in
addition to 4-film
13. Age Consideration Radiograph
6-7 No apparent abnormalities 8-film survey (available by 7 years of
age)
Extensive or deep caries Selected periapical radiographs in
addition to 8-film survey
8-9 No apparent abnormalities or extensive or
deep caries
12-film survey
10-12 No apparent abnormalities or extensive or
deep caries
12 or 16 film survey depending upon
size
16. 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
17. 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
18. • 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.
19. • 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.
20. •
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
21. • 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 O 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.
22. 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.
23. • A self sticking sponge tab may also reduce
impingement of the radiograph on the
intraoral soft tissue.
25. • 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.
26. • 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.
•
27. 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.
28. Bent film radiographic
• Used in young children who can not tolerate placement
of film inside their mouth
• Patient 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
29. • 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 extra oral 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
30. • 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.
31. • 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
33. 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
34. • 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
•
35. 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
36. 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.
37. • 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
38. 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 premolar
• A labially positioned mesiodens: A case report; Robert J
Henry, A Charles Post; Pediatric Dentistry March 1989-
vol 11:59-62
40. 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
41. 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
42. • 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
43. 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
44. Indications
• Determine the presence, shape and position of supernumerary
teeth
• Determine impaction of canines
• Assess the extent of trauma to teeth and anterior
• segments of the arches
• In case of trismus and trauma, where the patient cannot open the
mouth completely
• Determine the medial and lateral extent of cysts and tumors.
• To localize foreign bodies in jaws and stones in ducts of
• salivary glands.
• To obtain information about the location, nature extent and
displacement of fractures of maxilla and mandible
45. Extraoral technique
• RADIOGRAPHY OF PARANASAL SINUSES
– Standard Occipitomental Projection
– Modified method (30 degree OM)
– Bregma Menton
– PA Water's
•
RADIOGRAPHY OF MANDIBLE
– PA Mandible
– Rotated PA Mandible
– Oblique lateral radiography
• True laterals
• Oblique laterals
• Bimolars (two oblique laterals on one film)
46. • RADIOGRAPHY OF BASE OF SKULL
– Submento-vertex projection
• RADIOGRAPHY OF ZYGOMATIC ARCHES
– Jughandle view (A modification of submentovertex
view)
• RADIOGRAPHY OF TEMPOROMANDIBULAR JOINT
– Transcranial Projection
– Transpharyngeal projection
– Transorbital projection
47. RADIOGRAPHY OF THE SKULL
• Lateral Cephalogram
• True lateral (Lateral Skull)
• PA Cephalogram
• PA Skull
• Towne's projection
• Reverse Towne's projection
48. 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
49. •
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).
50. • 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.
51. 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
52. • Teeth present
– Stage of development
– Position
• Condition of crowns
– Caries
– restorations
• Condition of root
– Length
– Resorption
– crown root ratio
53. • 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
54. • Describing the lesion
– size
– shape
– location
– density
– internal architechture
– effect on adjacent structure
55. • 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
56. • 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
57. • 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. MDS pediatric dentistry
2003, 25-29
59. DIGITAL RADIOGRAPH
• 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.
60. 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
61. Radiovisiography
• Introduced by Mouyen et al in 1989.
• Radio partonsor-
– 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
62. • 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.
63. 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 environment.
– The problems that can be caused through processing faults are
eliminated.
– It gives opportunity to enhance the images for more precise
viewing.
64. • 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
65. • 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.
• Radio Visiography in the Detection of Periapical Lesions John E.
Sullivan, Jr., DDS, MS, Peter M. Di Fiore, Journal of endodontics,
2000, vol 26:65-69
66. 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
– Improves visualization of files and canals.
– Two times more sensitive than conventional D speed films.
67. 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
68. Digital subtraction 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
69. • 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.
70. • 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)
71. 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.
72. • 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
73. Advantages
– 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
74. • 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
75. 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
76. 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.
77. 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
78. • 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
79. 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
80. • TACT useful in
– Detection of caries and recurrent caries
– Periodontal bone loss
– Periapical lesion localization
– TMJbone change
81. 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
82. • 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
83. • 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.
84. Advantages
– 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.
85. 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
86. • 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
88. Radiation safety and Protection
• Primary biologic effects of radiation:
– Deterministic effects
– Stochastic effects
89. Source of the radiation 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
90. • Means of protection can be divided into:
1. Protection for operator
2. Protection for patient
91. 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 fluorescent mirrors in the oral
cavity
92. 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
93. Personnel Radiation Badge
• Use of film badge/ TLD badge / pocket
dosimeter, for personnel radiation monitoring
to avoid accumulate over exposure.
94. Protection of other
• 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.
96. Required Distances
• If the dental unit can operate above 50 kVp. the
source to skin distance must be at least 18 cm
[7inches].
• 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.
97. Filtration Requirement
•
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] 2.1
Units above 70 kVp Al or more
• Note: Settings below 65 kVp are not
recommended because of higher patient exposure
98. 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
99. 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.
100. System Speed
• Faster image receptor systems result in
decreased radiation exposure to the patient
101. 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.
102. 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.
103. • 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
104. References
• McDonald RE, Avery DR, Dean JA. Dentistry for th child and
adolescent, 8 edn. Mosby, 2004:117-28
• Tandon S. Textbook of pedodontics, 1# Publishing, 2001
:19-28 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, 1º edn. Arya
Publishing House, 2000: 167-71
105. • 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.
106. • 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.
