PRACTICE PERSPECTIVES


To Shield or Not to Shield? F


by STEPHANIE PATRICK, BS,RT(R)(M)(QM)


or decades, patients have been comforted with a traditional thick lead apron blanketed over them as their dental x-rays were performed. Knowing that harmful ionizing radiation was being blocked from their body gave them a sense of protection. But is it still necessary? New recommendations from the American Academy of Oral and Maxillofacial Radiology (AAOMR) have changed the way dental pro- fessionals can think about shielding.


RADIATION INTERACTIONS


When x-rays are emitted from the dental x-ray tube, there are a number of interac- tions that will occur. Some x-rays will be absorbed by the tube housing, which is lead-lined. Additionally, there are x-rays that will be absorbed in the patient’s body part being imaged contributing to their radiation dose, which is necessary for anatomy to be visualized. X-rays will also pass through the body and reach the image receptor (sen- sor). Finally, some x-rays change direction inside the body after interacting with tissue and may leave the body or interact again with other atoms. These x-ray photons that have changed direction are called scattered radiation and do not contribute to the useful image.


The cone on the dental unit limits the beam size where x-rays photons are being emitted from the tube. Using rectangular collimators in addition to the cone will further reduce patient dose, improve image quality, and reduce scattered radiation. Filtration is also built into the system to absorb lower energy beams that do not produce useful diagnostic information and will reduce radiation dose to the patient.


NEW RECOMMENDATIONS


Research has now shown that due to the very small area allowed by the dental imaging


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not required to shield pediatric or pregnant patients for dental imaging.¹ The American Dental Association supports this recommen- dation and will be publishing an article in early 2024.


At the time of this writing, the National Council on Radiation Protection and Measurements (NCRP) has not officially updated its stance and is in the stages of preparing a commentary about the recent AAOMR recommendations. The most recent NCRP publication on radiation safety during dental imaging, NCRP Report No. 177, states that aprons are to be discontinued, but thy- roid shields are to be utilized. The Missouri Radiation Control Program (MRCP) adheres to the recommendations of the NCRP.


equipment for primary radiation to enter the maxilla or mandibular areas, x-rays emitted from the tube do not reach the thyroid or gonadal areas at any significance;¹ these areas are more radiosensitive compared to other parts of the body. The AAOMR has found the risk to thyroid carcinoma is negligible. Decades of studying radiation exposure show that radiation does not produce heritable effects.¹,


SCATTERED RADIATION & DENTAL PERSONNEL


Scattered radiation is a concern for the operator of the x-ray equipment as it travels in all directions from the patient. Having the exposure switch outside the operatory or the use of a coiled switch allows dental personnel to maintain distance safely.


⁵ Modern x-ray dental equipment and


sensors allow for significantly lower radiation doses along with increased beam filtration.


Scattered radiation from the patient will also travel in all directions inside the patient’s body, and external lead placed on the patient in dental imaging does not assist in protect- ing the patient from their internal radiation dose received or reduce the amount of scat- ter produced in the body.¹,


²


It is now recommended by the AAOMR that no lead shielding is required for patient imaging, which includes lead aprons and thyroid shields. This new recommendation is applicable to all dental imaging including intraoral radiographs, panoramic, cephalo- metric and cone beam CT imaging. It is also


Regarding handheld units, the NCRP does not mandate that operators of these devices wear a lead apron. Backscatter shields are installed on the units to protect the operator of these devices. The MRCP and handheld manufacturers do recommend the use of a lead apron for the operator, but this practice is not widely utilized.³ It is also recommend- ed that all pregnant dental workers wear a lead apron when using handheld x-ray units.


RADIATION DOSIMETRY BADGES


Most dental practices in Missouri do not utilize a radiation dosimetry program where the dental staff is provided with badges to monitor the radiation dose received since it is usually minimal.⁶ The NCRP recommends dental personnel utilize monitoring in the following circumstances:


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