Dental Radiography Safety
By Aggie Barlow, CHP, MS, MBA
Goal
The goal of dental radiography is to obtain
useful diagnostic information while keeping
radiation exposure to the patient and dental
staff to a minimum.
Digital Radiography in Dentistry
Digital radiography was introduced in
Dentistry in 1987. The technology has been
gaining in acceptance, and in 2005 more than
22% of dentists were using digital
radiography. 1
Radiation Source
A conventional x-ray tube is the source of
X-radiation in most digital systems.
Digital radiography requires 50-80% less
radiation exposure in order to achieve an
image compared to film systems.2
Other Advantages
No film, no darkroom and no chemicals are needed.
No lead foil waste is generated.
Digital radiography has superior gray scale
resolution compared to conventional film.
Digital images can be magnified.
With the direct method, images appear immediately
on the computer monitor.
There is ease of information transfer to other dentists
or insurance companies.
MA Radiation Control Program
Safety Regulations
MA Regulations prohibit the deliberate
exposure of an individual for training,
demonstration or other non-healing arts
purposes.
Ordering Dental Radiographs
Examinations must only be performed on direct
prescription of a dentist, physician or other
legally authorized provider. Dental radiographs
must only be performed by Dentists or other
legally qualified and credentialed personnel.
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.
Personnel Radiation Badges
MA Regulations state that individuals who
operate only dental radiographic systems
are exempt from the radiation badge
requirements.
X-ray Tube Housing
The tube housing must not drift from its set position during an
exposure. The tube housing must not be hand-held during an
exposure by the operator or the patient due to leakage radiation
through the tube housing.
If you note problems with the tube housing, immediately
report this to your supervisor so that any instability of the
suspension arm can be corrected.
Required Distances
If the dental unit can operate above 50 kVp,
the source to skin distance must be at least
18 cm [7 inches].
The x-ray field must be limited to a circle
having a diameter of no more than 7 cm [~3 in].
An open-ended beam indicating device must be used.
Panoramic Units
The beam must be limited to the imaging slit in
the transverse axis and shall not exceed a total
of 0.5 inches larger than the imaging slit in the
vertical axis.
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*
Units above 70 kVp …..
….. 1.5 mm Al [HVL]
2.1 or more Al
*Note: Settings below 65 kVp are not recommended
because of higher patient exposure.
Technique Charts
Written operating procedures and techniques
must be available to all operators of dental
units.
Update each unit’s technique chart regularly.
Exposure Indicators
Units must have “dead man” type exposure
switches and indications of when an exposure
is being made.
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.
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.
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.
Collimators
Collimators limit the size and shape of the
useful beam which reaches the patient.
Rectangular collimators are recommended for
periapical radiographs as their use significantly
reduces the area of the patient’s body that
is exposed to radiation.
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.
System Speed
Faster image receptor systems result in
decreased radiation exposure to the patient.
Notes
1.
Dental Products Report (DPR) Radiography: A
DPR Survey report. Dental Products Report 2005,
May Accessed at:
www.dentalproducts.net/xml/display.asp?file=2976
2.
Haring, J., Howarten, L., Dental Radiography
Principles and Techniques, 3rd Edition.
Philadelphia, Elsevier, 2006, 351-2
Acknowledgement
The image of the preferred 90 to 135 degree
operator location was from:
Radiation Safety in Dental Radiography
Eastman Kodak Company, 2004
Rochester, NY, Health Imaging Division
Additional Suggested Reading
Radiation Protection in Dentistry
NCRP Report #145, Oct. 2004, Bethesda
For More Information
Contact:
Agnes Barlow at 617-636-3450
or
Tufts EH&S at 617-636-3615.