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Dental X-rays -- Do they increase the risk of Cancer ?

Recently a family member refused a dental X-ray, which was offered during the course of a teeth-cleaning appointment. There was an impression by this family member that the dental office was motivated to do this X-ray more for financial reasons than for reasons having to do with caring for her teeth. This page is an attempt to assess the risk of dental X-rays, from the literature. In particular, the question is much should we be worried about dental X-rays ? The areas being radiated are the jaw, head, the parotid and other salivary glands glands, and perhaps to some extent the thyroid.

As an overview, radiation increases the risk of cancer in the head/neck. X-rays are iionizing radiation, which damages tissue and DNA. So the real puzzle is how much do they increase cancer ? Most studies report roughly a 1.5 fold increased risk (odds ratio).

Review of literature (in 2021).

Benn and Vig(2021) wrote on "Estimation of x-ray radiation related cancers in US dental offices: Is it worth the risk ?" They concluded that oral cancers could be reduced. Quoting from their work, "Most cancers arise from intraoral and cone beam computed tomography examinations, with 135 orthodontic cancers over 21 months (average treatment time). Collimation and selection criteria could reduce this to 68. Only 1% of offices use collimators or informed consent for radiography. The website and consent information were of poor quality." This paper does not answer the question, but it does make some clear suggestions how dentist could do a better of protecting their customers.

Memon et al (2019) asked about the risk of thyroid cancer. They concluded "Based on a meta-analysis of retrospective case/control studies, these findings provide some support to the hypothesis that multiple (or repeated) exposures to dental X-rays may be associated with an increased risk of thyroid cancer and meningioma." Furthermore, "multiple (or repeated) exposures to dental X-rays were significantly associated with an increased risk of thyroid cancer (pooled RR = 1.87 [95% confidence interval, CI 1.11-3.15]) and meningioma (pooled RR = 1.53 [CI 1.26-1.85]). "

Mullarapa et al (2019) found differently than almost all other authors that "In this study, no association was found between dental x-ray exposure and the development of meningioma.". This study is an outlier.

Yeh and Chen (2018), estimated risk from cone beam. They observed that the salivary glands (such as parotids) have the highest dose of ratidation.

Xiu et al (2015) concluded that " Neither exposure to dental X-rays nor performance of full-mouth panorex X-rays was associated with an increased risk of development of meningioma (overall: OR, 0.97; 95% CI, 0.70-1.32; dental X-rays: OR, 1.05; 95% CI, 0.89-1.25; panorex X-rays: OR, 1.01; 95% CI, 0.76-1.34). However, exposure to bitewing X-rays was associated with a slightly increased risk of development of meningioma (OR, 1.73; 95% CI, 1.28-2.34). " We find this puzzling as we thought that bitewing X-rays was a type of dental X-ray, and it could not be both not associated and associated with meningioma.

Wu et al (2015) attempted to estimate LAR (or lifetime attributable risk). They commented that "The organ-specific cancer risks for thyroid cancer, other cancers, leukemia, and lung cancer account for 99% of the LAR." We are not sure we understand this.

Lin et al (2013) asked about the risk of brain tumors. They evaluated a large population. They concluded "Multivariable unconditional logistic regression analysis showed that the risk of BBT increases as the frequency of received dental diagnostic X-ray increases. The BBT odds ratio increased from 1.33 [95% confidence interval (CI) 1.22-1.44] for those with annual mean X-ray examination of less than one to 1.65 (95% CI 1.37-1.98) for those with three or more X-ray examinations, after controlling for comorbidities. " (BBT means benign brain tumor, such as a meningioma). As one would think, X-rays increases the risk of brain tumors to a small extent.

Han et al (2012) looked at the frequency of acoustic neuromas, a tumor of the inner ear. These are rare. They reported 'the authors identified only a single factor that was associated with a higher risk of VS: individuals exposed to dental x-rays once a year (aOR = 2.27, 95% CI = 1.01-5.09) or once every 2-5 years (aOR = 2.65, 95% CI = 1.20-5.85), compared with those exposed less than once every 5 years."

Longstreth et al (2004) noted "Dental X-rays involving full-mouth series performed 15-40 years ago, when radiation exposure from full-mouth series was much greater than it is now, were associated with an increased risk of meningioma. The authors did not observe an increased risk with bitewings, lateral cephalometric, and panoramic radiographs. " (odds ratio of about 2). We think this paper is just out of date.

 

Conclusion:

Of course radiation to the head/neck increases the risk of cancer in the head/neck. From the literature, the risk appears to roughly double -- so a rare thing (head/neck cancer) roughly doubles in likelihood in persons with regular dental X-rays.

We agree with the most recent paper of Benn and Vit (2021), that there is likely an immense amount of improvement possible in dental office practices. Regulations to require use of collimators (devices to prevent X-rays from spreading beyond the area being viewed), and also to allow patients to opt out of dental X-rays would seem to us to be highly desirable.

References:

© Copyright April 5, 2021 , Timothy C. Hain, M.D. All rights reserved.
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