• Many of the early pioneers in dental radiography suffered
from the adverse effects of radiation.
• Some pioneers lost fingers, limbs, and ultimately their lives to
excessive doses of radiation.
• Hazards of radiation are well documented, and radiation
protection measures can be used to minimize radiation
exposure to both the dental patient and the dental radiologist.
• X-radiation causes biologic changes in living cells and
adversely affects all living tissue.
• Use of proper patient protection techniques, the amount of x-
radiation received by a dental patient can be minimized.
• Patient protection techniques - Before,
After x-ray exposure.
Patient protection measures
• Before Exposure
• Patient protection measures can be used before any x-
• Proper prescribing of dental radiographs and the use of
equipment can minimize the amount of x-radiation that a
dental patient receives.
• PRESCRIBING DENTAL RADIOGRAPHS
• First important step in limiting the amount of x-radiation
received by a dental patient - proper prescribing, or
ordering, of dental radiographs
• Dentists (should) exercise professional judgment when
prescribing diagnostic radiographs for dental patients.
• Diagnostic radiography should be used only after clinical
examination, consideration of the patient's history and
consideration of both the dental and the general health
needs of the patient.
• PROPER EQUIPMENT
• Another important step in limiting the amount of x-
• Dental x-ray tube head must be equipped with appropriate
aluminum filters, lead collimator, and position-indicating
Purpose of filtration is to remove low-
energy x-ray photons resulting in
decreased patient exposure with no
loss of radiologic information
Two types of filtration
1.Inherent filtration and
• Inherent Filtration : takes place when the primary beam
passes through the glass window of the x-ray tube, the
insulating oil, and the tube head seal.
• Approximately 0.5 to 1.0 millimeter (mm) of aluminum.
• Added Filtration : refers to the
placement of aluminum disks in the path
of x-ray beam between the collimator
and the tube head seal.
• Aluminum disks added to the tube head
in 0.5-mm increments.
• Total Filtration - Inherent Filtration + Added Filtration
• Dental X ray machines - at or below 70 (kVp) require a
minimum total of 1.5 mm aluminum filtration.
• Above 70 kVp require a minimum total of 2.5 mm
• Filtration of the x-ray beam results in higher energy and
more penetrating useful beam.
• Disadvantage of using filters - 1. Increase exposure time
2.Decrease in the contrast
• Restrict the size and shape of the
x-ray beam and reduce patient
• Collimator, or lead plate with a
hole in the middle, is fitted
directly over the opening of the
machine housing where the x-
ray beam exits the tube head .
• Collimator may have either a round or
rectangular opening .
• Rectangular collimator restricts the size of
the x ray beam to an area slightly larger than
size 2 intraoral film and significantly reduces
• Circular collimator produces a cone-shaped
beam - 2.75 inches in diameter, considerably
larger than a size 2 intraoral film.
• when the x-ray tube is operated above 50kVp -
x-ray beam should be collimated so that the field of
radiation is"contained in a circle having a diameter of no
more than 7 cm (2 3/4 inches)”.
• Coliimation decreases
Risk of radiation,
Minimises scattered radiation and
Decreases the fog, with a sharper image and better contrast
• POSITION-INDICATING DEVICE OR CONE
• Extension of the x ray tube head used to direct the x-ray
• Help to minimize the volume of tissue irradiated
• Increase the target film distance by using longer position
indicating devices to direct the X ray beam.
• Three basic types of PIDs:
• Conical PID appears as a closed,
pointed plastic cone.
• x-rays exit from the pointed cone,
penetrate the plastic and produce
scatter radiation- no longer used in
• Open-ended and lead-lined rectangular
or round PIDs are used -do not produce
• Available in two lengths: short (8 inch)
long (16 inch).
• long PID is preferred
because less divergence of
the x-ray beam occurs .
• Rectangular type is most
effective in reducing patient
• During Exposure
limit the amount of radiation received by the patient.
• Exposure factors and good technique - further protect the
patient from excess exposure to x-radiation.
• THYROID COLLAR
• Flexible lead shield placed securely around
the patient's neck to protect thyroid gland -
• Separate shield or part of lead apron -
thickness of 0.2 mm.
• Recommended for all intraoral films as thyroid gland is
exposed to x-radiation because of its location.
• Not recommended with extra oral films - obscures
information on the film resulting in non diagnostic
• Lead apron
• Flexible shield placed over the patient's
chest and lap to protect the reproductive
and blood-forming tissues from scatter
• Recommended for all intraoral and extra
oral films with protective equivalent of
l/4th mm of lead.
• Act as secondary measure to protect the patient
• Should not be substituted for use of fast films, lead
collimation and aluminum filtration which are primary
means of reducing exposure to the patient.
If holding a patient is required…
• Use shielding
Apron, gloves, thyroid shield, glasses
• Avoid exposing assisting person to the primary beam.
• Gloves, aprons ,eyewear
Protect from scatter or transmitted
• Eye Protection
Glasses 0.75mm Pb (0.9% @ 90kV)
• Hand protection
• 0.5mm Pb (1.2% @ 90kV)
• 1.4 kg each
• Person assisting the patient must wear a lead apron and
lead gloves if their hands will be in the beam.
• Fast film
• Most effective method of reducing patients exposure to x-
• Avaliable for both intraoral and extra oral radiography.
• Intraoral dental x-ray film - available in three speed
groups-D, E, and F.
• Clinically, film speed of group E is almost twice as fast
(sensitive) as film of group D , about 50 times as fast as
regular dental x-ray film.
• F-speed film requires about 75% exposure of E-speed film
and only about 40% that of D-speed.
• F-speed film has same density range, latitude, contrast,
image quality as D- and E-speed films without sacrifice of
• Current digital sensors offer equal or greater dose saving
than F speed film and comparable diagnostic utility.
• Used in extra oral radiography - use the rare earth elements
gadolinium and lanthanum.
• Emit green light on interaction with x rays.
• Decrease patient exposure by about 55% in panoramic and
cephalometric radiography compared with older calcium
• Focal spot film distance
• X-rays are less divergent at a longer
distace , leading decrease in the
volume of the patient exposed .
• Use of long source to skin distance of
40 cm, rather than short distance of 20
cm decreases exposure by 10 to 25 %
• Equipment operating below 50 kVp should have a
minimum distance af 10 cm (4") from the end of the PID to
the focal spot.
• Above 50 kVp should have a minimum distance of 18 cm
(7”) from the end of the PID to the focal spot.
• Film-holding devices
• Helps to stabilize the film position in
the mouth and reduces the chances of
• Eliminates the need for the patient to
hold the film in place.
• Patient's finger is not exposed to
• Possibility of misaligning the X-
ray tube and partially missing
the film (cone cut), is also
• Exposure factors selection
• Dental radiologist can control the exposure factors by
on the control panel of the dental x-ray machine.
• limiting the amount x ray radiation exposure to patient.
• Setting of 70 to 90 kVp keeps patient exposure to a
• PROPER TECHNIQUE
• Ensure diagnostic quality of films and reduces the amount
of exposure patient receives.
• To produce diagnostic films, radiologist/ radiographer
must have thorough knowledge of the techniques most
often used in dental radiography.
• AFTER EXPOSURE
• After the films have been exposed, they must be handled
• Meticulous film handling and proper film-processing
techniques are critical for the production of high-quality
• OPERATOR PROTECTION MEASURES
• Dental radiologist must use proper protection measures to
avoid occupational exposure to x-radiation (e.g., primary
radiation, leakage radiation, scatter radiation).
• Minimize the amount of radiation that a dental radiologist
• And includes 1. Protection guidelines
2. Radiation-monitoring devices.
• Protection guidelines
• Include recommendations on
• Distance and position -
• If no barrier is available, the operator
should stand at least 6 feet from the
• At an angle of 90 to 135 degrees to the
central ray of the x-ray beam when the
exposure is made.
• Proper operator position also includes the following:
• Never hold a film in place for a patient during x-ray
• Never hold the tube head during x-ray exposure.
• Shielding recommendations
• Dental radiologist should stand behind a protective
barrier such as a wall during x-ray exposure
• Constructed of gypsum wall board.
• Radiation Monitoring
• Used to identify excess occupational exposure and to
protect the dental radiologist.
• Includes monitoring of both equipment and personnel.
• Equipment monitoring
• Dental x-ray machines must be monitored for leakage
radiation through the use of a film device.
• Obtained through the state health department or from
manufacturers of dental x-ray equipment.
• Personnel monitoring
• Amount of x-radiation that reaches the body of the dental
radiologist can be measured through the use of a personal-
monitoring device known as a film badge.
• Consists of a piece of radiographic film in a
• Radiologist - have his or her own film badge
• Worn at waist level whenever exposing x-ray
• Should never be worn when the radiologist is
undergoing x-ray exposure.
• Film badges not worn, stored in radiation-safe
• After the dental radiologist has worn the film badge for a
specified interval (eg., 1 week, 1 month), the badge is
returned to the service company.
• Company processes and evaluates the film for exposure
• Provides the dental office with an exposure report for each
• HARING & HOWERTON Dental Radiography 3rd edition
• Easy to handle and process
• Reasonably accurate
• Can not be reused
• Sensitive to heat and humidity
• Must be changed monthly
• Measurement range 0. 1 µSv
to 5 Sv
• TLD has several Advantages over film badges.
• Not sensitive to heat or humidity
• More sensitive and accurate.
• Can be changed quarterly instead of monthly
• Cost but changing badges less frequently than
monthly eliminates cost problem.
• ENVIORNMENT PROTECTION MEASURES
• Surrounding environment must be protected from radiation to
avoid exposure to persons in the environment
• Primary beam - never be directed at any one other than patient.
• Patient should be positioned such that the X-ray beam aimed at
the wall of the room and not through the door or other opening
where people may be located,
• Walls made of 3" of concrete, or 1 mm of lead will suffice
to protect adjacent rooms, even if the work load in the
radiology department is high.
• An alternative to lead is Barium due to it's
High atomic number,
High density and
High linear coefficient of attenuation.
• Used in the form of Barium Plaster or Barium Concrete.
• If it is not possible to incorporate
lead or barium into the walls, they
can be lined with lead plywood, 0.25
mm of lead sandwiched between
layers of wood.
• Primary barrier should be incorporated
in any part of the floor or ceiling of the
room at which the beam is fired.
• Secondary barrier in the walls, provide
protection against scattered or leakage
radiation and as exposure rates are
small they are 1/2 the thickness of the
• As the patient is being irradiated,
window is provided so that the
operator can see.
• Situated, where the primary beam is
not directed on it
• Lead glass should be used
• Doors - radiology room should
function as secondary barriers having
lead incorporated in them.
• Switches may be incorporated so that
the beam is cut off as soon as the
door is opened and not allow the
beam to be switched on till the door
is closed completely.
• Warning Light and Placard
• Warning signal (red light ) should be placed at an
conspicuous place outside the X-ray room which should go
on when the exposure button is pressed, or
• Placard should be placed to signal that the process of X-ray
taking is in progress.
• Quality assurance
• Defined as any planned activity to ensure that a dental
office will consistently produce high quality images with
minimum exposure to patients and personnel.
• Regular radiation surveys
• Should be performed at regular intervals as the amount of
exposure is dependent on many factors, such as :
• Machine's kilo voltage
• Work load of the X-ray machine
• X-ray absorbing ability of the walls
• Amount of time the adjacent areas are occupied by people.
• RADIATION EXPOSURE GUIDELINES
• Protect the patient and operator from excess radiation
• Guidelines include 1.Radiation safety legislation
for the general public and for persons who are
occupationally exposed to radiation.
• Radiation Safety Legislation
• Established at both the state and the federal level to protect
the patient, operator, and general public from radiation
• At federal level - Radiation Control for Health and Safety
Act was enacted in 1968 to standardize the performance of
x-ray equipment .
• Federal Consumer-Patient Radiation Health and Safety Act
was enacted in 1981 to address the issues of the education
and certification of persons using radiographic equipment.
• Radiation legislation varies greatly from state to state.
• Dental radiologist must be familiar with the laws that apply
to his or her workplace.
• Exposure limits
• Maximum Permissible Dose:
• Defined by the NCRP as the maximum dose equivalent
that a body is permitted to receive in a specific period of
• MPD - dose of radiation that the body can endure with
little or no injury.
• Maximum Accumulated Dose
• When occupationally exposed workers must not exceed an
accumulated lifetime radiation dose.
• Determined by formula based on the worker's age.
• N refers to the person's age in years.
• 18 refers to the minimum required age of a person who
works with radiation.)
• ALAR A CONCEPT
• states that all exposure to radiation must be
kept to a minimum, or "as low as
• To provide protection for both patients and
• Every possible method of reducing
exposure to radiation should be employed
to minimize risk.
• RADIATION PROTECTION AND
• Education and orientation of all radiation personnel to
the ill effects of radiation is mandatory.
• Continuing education programs keep them alert to the
possible risk and orient them to new equipment.
• Dental radiologist must be prepared to explain exactly how
patients are protected before, during, and after x-ray
• Printed handouts or pamphlets outlining the steps used to
protect patients from excess radiation can be provided to
• Placed in reception area or room where dental radiographs
• Recommendations of NCRP
• Dentists Role in Radiation Protection
• Establish a radiation protection program
• Prescribe all radiographic examinations
• Shall conduct a clinical history and physical exam and
determine health benefit to patient from the radiographic
• Shall obtain guidance from a qualified expert - facility
design & radiation protection
• Dentists Role in Patient Protection
• Shall make an effort to obtain recent radiographs from
patient's previous dentist
• Take radiographs only if indicated after an evaluation of
clinical history, physical exam or laboratory findings
• Shall limit radiographic examinations of symptomatic
patients to those required for diagnosis and treatment of
• Shall not expose radiographs for administrative purposes
• Oral radiology Principles and Interpretation,
White and Pharoah – Fifth edition
• Textbook of Dental and maxillofacial Radiology,
Freny. R. Karjodkar – 2 edition
• Essentials of Dental Radiography and Radiology,
Eric Whaites – Fourth edition
• J. Anthony Seibert, “X-Ray Imaging Physics for Nuclear
Medicine Technologists. Part 1: Basic Principles of X-Ray
J Nucl Med Technol 2004; 32:139–147