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Oral Radiology

What is the impact of emerging radiographic technologies on cumulative patient ionizing radiation exposure?

(Content under development)

The following question was submitted by a practising dentist: I have seen an exponential growth in the marketing of CBCT to dentists (shouldn’t we ALL have one?), and have seen an emerging trend of dentists using them to reverse engineer pans etc. Most recently, an advert came across my desk where bitewings engineered from a pan are the answer. What is the impact of emerging radiographic technologies on cumulative patient ionizing radiation exposure?

JCDA Editorial Consultants Drs Ernie Lam of the University of Toronto, Garnet Packota of the University of Saskatchewan and Elaine Orpe of Vancouver provided these initial responses for consideration:

On the impact of CBCT on overall radiation levels, Dr. Lam commented: We have no data for such an increase in ionizing radiation levels in dentistry.  In medicine, however, between 1990 and 2006, the per capita effective dose to the population from medical imaging studies has increased from 0.53 mSv to 3.0 mSv; almost 6 times, according to a recent article.  This is an amazing increase that I think can be attributed substantially to the increased availability of medical spiral CT systems since 1990.  I can only think that with the budding growth of cone beam CT systems, that the per capita dose from oral and maxillofacial radiological procedures will see similar increases.

Dr. Packota also commented on this issue: The ICRP (International Commission on Radiological Protection) has data which show that the contribution of “dental” radiography to the population dose from for diagnostic procedures is very small and insignificant compared to the contribution from “medical” imaging.  It will be interesting to see if the increased use of CBCT increases the “dental” share when ICRP prepares its next report.

On the issue of “reverse engineering” of radiographs, Dr. Orpe commented: It may indeed be possible to create a panoramic-like image from CBCT data, but this will result in an effective patient dose many times higher than that with current conventional panoramic techniques using either  film/rare earth screen or digital technology.  It is therefore never acceptable to replace a conventional panoramic image with a reconstructed CBCT image from a radiation hygiene or ALARA perspective.

Some panoramic units provide the capacity to provide images similar to intraoral bite-wing radiographs.  The effective dose to the patient may be comparable to conventional bite-wing radiographs but intraoral bite-wing radiographs are superior for proximal caries detection for premolar and molar teeth (Kamburoglu et al 2012).  As interproximal caries detection is the most common justification for taking bite-wing radiographs, substitution with panoramic-derived bite-wings is inappropriate unless it was impossible to obtain the conventional bite-wing radiographs.

Follow-up: Readers are invited to comment on this initial response and provide further insights by posting in the comment box which you will find by clicking on “Leave a reply“ below. Comments come directly to me for approval prior to posting. You are welcome to remain anonymous. We will never post your email address in any response. John


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