Article by Spring Hatfield, RDH, BSPH – September 18, 2023
Radiographs in dentistry are an important aspect of providing comprehensive patient care. Though many patients balk at the idea of getting radiographs, it’s imperative to acquire them in order to diagnose diseases such as periodontal disease, dental caries, abscesses, and certain lesions of the jaw.
One could argue radiographs are one of the most important diagnostic tools we use in dentistry. We now have multiple imaging types to assist in disease diagnosis, including intraoral, panoramic, cephalometric, and cone-beam computed tomography (CBCT) imaging. Nonetheless, it’s crucial to use certain principles to determine the need for radiographs and what kind of radiographs to acquire.
An article in the Journal of the American Dental Association reminds dental professionals to ask these questions when deciding on the need and what type of image to capture include:1
- What image is needed to answer any diagnostic questions?
- What technique will use the least amount of radiation to answer the diagnostic question?
- What are the benefits of acquiring the image?
- What are the risks of acquiring the image?
These questions are necessary to reduce the amount of radiation patients are exposed to during their dental appointments.
ALARA
The aim of ALARA (as low as reasonably achievable) is to reduce radiation exposure as much as possible while still allowing for proper diagnosis of dental diseases. Multiple approaches can reduce a patient’s radiation dose; it isn’t simply reducing the number of radiographs taken.
Using digital radiography alone reduces the radiation exposure by 90% compared to the radiation dose using E-speed films while also improving diagnostic accuracy with filtering and enhancement tools.2 The first digital X-ray sensor became available in the mid-1980s, developed by Francis Moyen. These sensors were limited in their abilities. They did not allow for image storage, and the image had to be printed.
As any clinician knows, digital systems have improved exponentially through the years. It is safe to say that radiation dose reduction is one of the biggest benefits of this technology that is utilized in most dental practices today.3
The reduced radiation exposure from digital radiography allows for better adherence to the ALARA concept. However, other methods can reduce the dose as well. Rectangular collimation restrictions further lower the dose by 60%, though the risk of needing to retake images increases.2
Of course, lead shielding has been a staple in dental practices for many years. However, recent research has indicated it isn’t as helpful as it is perceived to be when other measures are implemented to reduce radiation dose.2 In 2019, the American Association of Physicists in Medicine published a position paper urging the discontinuation of lead shielding. Among other things, the position paper indicates that lead shielding is ineffective in reducing internal scatter radiation, rendering it useless in reducing radiation dose.4
In addition to the 2019 position paper, the American Academy of Oral and Maxillofacial Radiology recently published clinical practice guidelines specific to dental radiography that further support the stance of the American Association of Physicists in Medicine’s position paper.1
Gonadal Shielding
Gonadal shielding is mandated in some U.S. states, and it is done to “reduce the risk of radiation-caused hereditary effects.”1 However, this idea has been challenged due to a lack of scientific rationale to support the practice. The thought behind gonadal shielding is that it could lead to heritable effects. However, despite the public’s (and some dental professionals’) beliefs, heritable effects from radiation have not been observed in humans.1,5
The recommendation made by the American Academy of Oral and Maxillofacial Radiology regarding gonadal shielding states that gonadal shielding “during diagnostic intraoral, panoramic, cephalometric, and CBCT imaging should be discontinued as routine practice.”1
Thyroid Shielding
The thyroid gland is exposed to radiation during dental radiographs via the primary beam and internal scatter. Nonetheless, dental radiographs’ anticipated dose to the thyroid is minimal when compared to other medical imaging (see Figure 1). As a matter of fact, doses with bitewing radiographs and periapical radiographs are below detectable levels.1
Panoramic imaging uses a collimated narrow beam, which produces little scatter. Studies show the thyroid gland absorbed doses are less than 0.1 mGy without shielding. Further shielding could cause artifacts, requiring retaking the image and exposing the patient to more radiation than is necessary. There is no difference in the amount of radiation exposure with or without lead shielding when acquiring a panoramic image.1,6
Cephalometric images are much the same as panoramic images. Many cephalometric units have a collimated beam, which decreases scatter. Even in the absence of this feature, the radiation dose to the thyroid gland from cephalometric images is less than 0.1 mGy.1
Radiation doses from CBCT imaging vary depending on the area being imaged. As you can imagine, a CBCT of the maxilla has a lower dose to the thyroid than a CBCT image of the mandible. Nonetheless, thyroid dose from CBCT imaging is very similar to intraoral imaging, with no difference in dose with or without shielding.1,7
| Procedure | Unshielded Dose (mGy) | Shielded Dose (mGy) |
| Intraoral radiography:FMX, round collimation, F-speed film, or phosphor plates | 0.8 | 0.5 |
| Intraoral radiography:FMX, rectangular collimation, F-speed film, or phosphor plates | 0.4 | 0.3 |
| Intraoral radiography:FMX, rectangular collimation, sensor | 0.2 | 0.1 |
| Intraoral radiography: Bitewing radiographs | 0 | NA |
| Panoramic radiograph | < 0.1 | < 0.1 |
| Cephalometric radiography | < 0.1 | < 0.1 |
| Cone beam CT | 0.3 | 0.1 |
| Head and craniofacial CT | 0.6-8.7 | NA |
| Mammography | 0.4-0.8 | NA |
| Chest CT, mean (SD) | 18 (8) | NA |
Figure 1 Thyroid-absorbed radiation doses Adapted from Benavides, E. et al.1
The final recommendation by the American Academy of Oral and Maxillofacial Radiology is, “Patient thyroid shielding during diagnostic intraoral, panoramic, cephalometric, and CBCT im- imaging should be discontinued as routine practice.”1
Breast Shielding
Though lead shielding was originally done to protect the gonads, it also protected the breasts. Breast tissue is a sensitive tissue that could be affected by radiation doses leading to radiation-induced breast cancer. Breast tissue is more sensitive to radiation in patients under the age of 30.1,5
Breast doses from intraoral, panoramic, and cephalometric radiography and CBCT imaging are less than 0.1 mGy. This dose is negligible, as is the risk of breast cancer due to dental radiographs (see Figure 2). Consider the dose absorbed from annual or biannual mammograms is between 1.4 to 3.1 mGy. This led to the determination that there is no evidence to require breast shielding for dental radiographs.1,8
| Procedure | Unshielded Dose (mGy) | Shielded Dose (mGy) |
| Intraoral radiography | < 0.1 | < 0.1 |
| Panoramic radiography | < 0.1 | < 0.1 |
| Cephalometric radiography | < 0.1 | < 0.1 |
| Cone beam CT | < 0.1 | < 0.1 |
| Mammography range | 1.4-3.1 | NA |
| Head CT | 0.3 | NA |
| Chest CT, lung cancer screening (SD) | 15 (0.5) | NA |
Figure 2 Breast-absorbed radiation doses Adapted from Benavides, E. et al.1
Shielding During Pregnancy
In all dental radiography, the fetus is well outside the field of imaging, and radiation doses are below 0.1 mGy. The threshold for complications associated with radiation exposure is set at 100 mGy, indicating there is essentially zero risk to the fetus (see Figure 3).1
Pregnant patients may voice their concerns regarding the lack of lead shielding. It is the responsibility of the clinician to communicate the absence of risk and lack of benefits with lead shielding. This is best presented with confidence; if you don’t have confidence in the evidence, the patient won’t either.1
| Effect | Threshold Dose (mGy) | Sensitive Gestation Period | Risk from Oral and Maxillofacial Imaging |
| Prenatal death | 100 | < 10 days | None; fetal dose approximately 10,000-fold lower than threshold |
| Microcephaly | 100 | 2-15 weeks | None; fetal dose approximately 10,000-fold lower than threshold |
| Growth impairment | 100 | 2-15 weeks | None; fetal dose approximately 10,000-fold lower than threshold |
| Intellectual disabilities | 300 | 8-15 weeks | None; fetal dose approximately 30,000-fold lower than threshold |
| Radiation-induced cancer | None | Throughout pregnancy | Negligible, approximately 1 in 1.7 million |
Figure 3 Effects of prenatal radiation exposure Adapted from Benavides, E. et al.1
Shielding in Children
Parents may be concerned about the lack of lead shielding in pediatric patients. It is helpful to explain to the parent that the main risk of exposure is from internal scatter radiation, which is not reduced with the use of a lead shield. Lead shields can be heavy and uncomfortable, causing the child to move and fidget, which could cause poor-quality images that require retakes, exposing the child to even more radiation.1
The best way to reduce radiation exposure in children and all populations is through risk assessment and patient selection for radiographic imaging (see Figure 4).9 Patient selection, collimation, and digital technology are the recommended methods for reduced radiation exposure in a dental setting. Lead shielding is no longer necessary or recommended as a method to reduce radiation exposure when capturing dental radiographs.1
| Type of Encounter | Child with Primary Dentition | Child with Transitional Dentition | Adolescent with Permanent Dentition | Adult: Dentate or Partially Edentulous | Edentulous Adult |
| New patient being evaluated for oral disease | Individualized radiographic exam consisting of selected periapical/occlusal views and/or posterior bitewings if proximal surfaces cannot be visualized or probed. Patients without evidence of disease and with open proximal contacts may not require a radiographic exam at this time. | Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. | Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. A full mouth intraoral radiographic exam is preferred when the patient has clinical evidence of generalized oral disease or a history of extensive dental treatment. | Individualized radiographic exam consisting of posterior bitewings with panoramic exam or posterior bitewings and selected periapical images. A full mouth intraoral radiographic exam is preferred when the patient has clinical evidence of generalized oral disease or a history of extensive dental treatment. | Individualized radiographic exam based on clinical signs and symptoms. |
| Recall patient with clinical caries or at increased risk of caries | Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be examined visually or with a probe. | Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be examined visually or with a probe. | Posterior bitewing exam at 6-12 month intervals if proximal surfaces cannot be examined visually or with a probe. | Posterior bitewing exam at 6-18 month intervals. | Not applicable |
| Recall patient with no clinical caries and no increased risk of caries | Posterior bitewing exam at 12-24 month intervals if proximal surfaces cannot be examined visually or with a probe. | Posterior bitewing exam at 12-24 month intervals if proximal surfaces cannot be examined visually or with a probe. | Posterior bitewing exam at 18-36 month intervals. | Posterior bitewing exam at 24-36 month intervals. | Not applicable |
| Recall patient with periodontal disease | Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically. | Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically. | Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically. | Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of, but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease (other than nonspecific gingivitis) can be demonstrated clinically. | Not applicable |
| New and recall patients for monitoring of dentofacial growth and development, and/or assessment of dental/skeletal relationships | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development or assessment of dental and skeletal relationships. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development or assessment of dental and skeletal relationships. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of dentofacial growth and development, or assessment of dental and skeletal relationships. Panoramic or periapical exam to assess developing third molars. | Usually not indicated for monitoring of growth and development. Clinical judgment as to the need for and type of radiographic image for evaluation of dental and skeletal relationships. | Usually not indicated for monitoring of growth and development. Clinical judgment as to the need for and type of radiographic image for evaluation of dental and skeletal relationships. |
| Patient with other circumstances including, but not limited to, proposed or existing implants, other dental and craniofacial pathoses, restorative/endodontic needs, treated periodontal disease, and caries remineralization | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions. | Clinical judgment as to need for and type of radiographic images for evaluation and/or monitoring of these conditions. |
Figure 4 Patient selection guidelines for dental radiographs Adapted from The Selection of Patients for Dental Radiograph Examination9
Conclusion
Lead shielding was implemented in the 1950s as a way to protect gonadal tissue and reduce the risk of heritable effects in humans. Since this time, we have discovered there is no risk of heritable effects in humans due to radiation exposure of the gonadal tissues.
Concerns also arose regarding thyroid exposure, breast tissue exposure, exposure to pregnant women, and children. However, new research has evaluated the absorbed dose in these organs and individuals and found lead shielding provides very little if any, level of protection. Further, we have advanced technology that reduces radiation exposure by 90%.
The American Academy of Oral and Maxillofacial Radiology published a paper in the Journal of the American Dental Association recommending against lead shielding for all dental radiographs. The paper has recommended that “Federal, state, and local dental regulations and guidance should be revised to remove any actual or implied requirement for routine lead shielding for intraoral, panoramic, cephalometric, and CBCT imaging.”1
I’m certain a subset of dental professionals will want to err on the side of caution and claim lead shielding can’t hurt, but I would argue that it can indeed. Continuing to use lead shielding will propagate a fear-based mindset associated with dental radiographs. This mindset is ingrained in our society, and if we continue to feed this belief, we will be in a constant fight to acquire the radiographs we need to properly diagnose and treat our patients.
Therefore, I encourage all dental professionals to embrace the new recommendations and take the initiative to explain why lead shielding is no longer recommended or necessary for dental radiographs. If you live in a state that requires lead shielding, please continue to do so until regulations in your state change. However, be aware there are likely going to be changes made to your state’s dental practice act to reflect these newer recommendations.
Dentistry has very few agreed-upon guidelines. However, when clear clinical practice guidelines are provided, we should adhere to these guidelines for multiple reasons. One reason is for the calibration of care for our patients while also providing the most up-to-date treatment protocols backed by evidence.
This change may be difficult for some dental professionals, but we can’t practice dentistry based on opinions. We need evidence. The evidence regarding lead shielding for dental radiographs is clear. Lead shielding does not provide any benefits to patients when acquiring dental radiographs.
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References
- Benavides, E., Bhula, A., Gohel, A., et al. Patient Shielding during Dentomaxillofacial Radiography: Recommendations from the American Academy of Oral and Maxillofacial Radiology.Journal of the American Dental Association. 2023; 154(9): 826-835.e2. https://doi.org/10.1016/j.adaj.2023.06.015
- Jayachandran, S. Digital Imaging in Dentistry: A Review.Contemporary Clinical Dentistry. 2017; 8(2): 193-194. https://doi.org/10.4103/ccd.ccd_535_17
- van der Stelt, P.F. Filmless Imaging: The Uses of Digital Radiography in Dental Practice.Journal of the American Dental Association. 2005; 136(10): 1379-1387. https://doi.org/10.14219/jada.archive.2005.0051
- AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding [PP 32-A]. (2019, April 2). American Association of Physicists in Medicine. https://www.aapm.org/org/policies/details.asp?id=468&type=PP
- Hiles, P., Gilligan, P., Damilakis, J., et al. European Consensus on Patient Contact Shielding.Insights into Imaging. 2021; 12(1). https://doi.org/10.1186/s13244-021-01085-4
- Rottke, D., Grossekettler, L., Sawada, K., et al. Influence of Lead Apron Shielding on Absorbed Doses from Panoramic Radiography.Dentomaxillofacial Radiology. 2013; 42(10): 20130302. https://doi.org/10.1259/dmfr.20130302
- Rottke, D., Andersson, J., Ejima, K.I., et al. Influence of Lead Apron Shielding on Absorbed Doses from Cone-beam Computed Tomography.Radiation Protection Dosimetry. 2017; 175(1): 110-117. https://doi.org/10.1093/rpd/ncw275
- Hruska, C.B., O’Connor, M.K. Curies, and Grays, and Sieverts, Oh My: A Guide for Discussing Radiation Dose and Risk of Molecular Breast Imaging.Journal of the American College of Radiology. 2015; 12(10): 1103-1105. https://doi.org/10.1016/j.jacr.2015.07.001
- The Selection of Patients for Dental Radiographic Examinations. (2019, June 20). U.S. Food and Drug Administration. https://www.fda.gov/radiation-emitting-products/medical-x-ray-imaging/selection-patients-dental-radiographic-examinations
Article by Spring Hatfield, RDH, BSPH – September 18, 2023