_______________________________ DCA05DR Dental Radiation Health, Safety, and Protection, 3rd Edition
filtration (Wilczek, 2025). Through the use of aluminum filters low-energy and nondiagnostic X-rays are removed from the primary beam or radiation (Hariry et al., 2024). Collimation The lead collimator restricts the size and shape of the x-ray beam as it exits the tubehead and therefore aids in reducing the radiation dose for the patient. Collimators can be circular or rectangular and can be placed within the tubehead or at the end of the lead-lined cylinder. Rectangular collimation is preferred over circular collimation because it decreases the area of exposure by 60% (Benavides et al., 2023). Circular collimators can be converted to a rectangular-shaped opening with commercially available devices. The use of rectangular collimators coupled with the appropriate film-holding appa- ratus has been shown to reduce alignment errors and vertical distortion for dental x-rays (Senior et al, 2020). Patient Shields Lead aprons and thyroid collars have been used to provide shielding to reduce radiation exposure to the gonads and thyroid gland, respectively for decades. The amount of scatter radiation to the abdominal area during dental radiographic examinations is negligible (Tufts University, 2025). The use of routine shielding may not be necessary as the benefits may be minimal given the decreased dose of radiation in today’s medical and dental x-rays (Jaklevic & Chris, 2020). Several organizations have advocated the discontinuation of routine shielding during routine dental x-rays. In 2019 the American Association of Physicists urged the discontinuation of lead shielding as this was ineffective in the reduction of internal scat- ter radiation (Hatfield, 2023). The American Academy of Oral and Maxillofacial Radiology recommended the discontinua- tion of shielding of the gonads, pelvic structures, and fetuses during dentomaxillofacial imaging and the discontinuation of thyroid shielding during intraoral, panoramic, cephalometric, and cone-beam computed tomography (CBCT) (Benavides et al., 2023; Kiser et al., 2024). However, clinicians must adhere to laws promulgated by their states about shielding during x-rays. Patients who have been shielded in the past may be reluctant to undergo dental x-rays without a lead apron and a thyroid collar. Additionally, the thyroid gland in children is especially sensitive to radiation exposure, and the risk of thyroid cancer induction is 3-fold higher in children and adolescents of ages 10-19 and 10-fold higher in children younger than 10 years of age, so their parents may refuse dental x-rays unless a thyroid collar and traditional shielding are utilized (Benavides et al., 2023). Thyroid collars protect the sensitive thyroid tissue from scatter radiation. Rectangular collimation also significantly reduces radiation exposure to the thyroid gland compared with circular collimation (Johnson & Ludlow, 2020). It should be noted that many states mandate the use of a lead apron and thyroid collar on all patients, and unless they are changed to conform with the most recent recommendations for shield- ing, these must be observed by dental clinicians (Benavides et al., 2023).
PATIENT PROTECTION Protecting patients from excessive radiation exposure is vital. Every effort should be made to keep the radiation dose to all individuals as low as possible; all unnecessary radiation should be avoided. The ALARA principle recognizes that no matter how small the dose, some biologic effect may occur. Methods to reduce radiation exposure to the patient and adhere to the ALARA principle include the use of established guidelines for prescribing radiographs, filtration, collimation, lead aprons and thyroid collars, fast image receptors, beam alignment devices, and quality assurance practices to minimize retakes, as well as periodic inspection of equipment. Selection Criteria Radiographs should be prescribed only when a high prob- ability exists that the radiographic examination will provide information that will affect the treatment or prognosis of the patient. In other words, rather than routinely exposing every patient on an annual basis, clinicians should determine the frequency and type of radiographic examination based on the oral condition of the patient and the dentist’s estimate of the patient’s disease susceptibility. Joint recommendations for prescribing dental radiographs have been initially established by the American Dental Association (ADA), the U.S. Food and Drug Administration and the U.S. Public Health Service in 2012 and updated in 2019 (American Dental Association, 2024; Demarco, 2022; Johnson et al., 2021). The dentist is responsible for justifying the radiographic exami- nation to ensure that the benefit of the radiographs outweighs the risk. This process includes a review of the patient’s health history, completion of a clinical examination, application of the recommendations for prescribing dental radiographs, and adherence to the ALARA principle to minimize patient exposure (Benavides et al., 2024). The recommendations are subject to clinical judgment and may not apply to every patient. Indicators that the dentist may use to determine the need for radiographs include the presence of caries, periodontal disease, pain or trauma, previous restorations, eruption discrepancies, or missing teeth. The recommendations are organized by the type of patient encounter, patient age, and developmental stage. Table 6 summarizes the updated primary recommenda- tions provided in the ADA document. Filtration The x-ray beam exiting the tubehead contains both high-energy and low-energy photons. Filters remove the low-energy, long- wavelength x-rays from the beam. The low-energy x-rays are detrimental because they are absorbed by the patient without contributing to the diagnostic information on the radiograph. Filtration involves placing aluminum disks in the path of the x-ray beam; federal law regulates the thickness of the aluminum. A dental x-ray machine operating below 70 kVp should have at least 1.5 mm aluminum filtration, while a machine operating at 70 kVp or higher should have at least 2.5 mm aluminum
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