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 atleast six feet from the useful beam or behinda protective barrier. [Stand at an angle of from 90 to135 degrees from the central ray. Do NOT stand inthe path of the primary x-ray beam.]

If a protective barrier is used, it must have a viewingwindow 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 anexposure. The tube housing must not be hand-held during anexposure by the operator or the patient due to leakage radiationthrough the tube housing.

If you note problems with the tube housing, immediatelyreport this to your supervisor so that any instability of thesuspension 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 theoperating 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.

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.