Three-dimensional imaging in paediatric dentistry: a must-have or you’re not up-to-date?

Radiation protection guidelines are very simple and straightforward and are simply common sense. First of all the exposure should be justified, secondly the exposure should be as low as reasonably achievable, and finally the exposure should result in the best diagnostic image possible. These are the three basic principles of radiation protection and they hold for every exposure to ionising radiation, whether twoor three-dimensional. Nonetheless, numerous publications mention the use of three dimensional (3D) imaging in dentistry as a diagnostic aid without assessing the potential health risk for a patient. There is no doubt that a 3D procedure will provide a better-looking image than a traditional two-dimensional (2D) one. However, the basic principles of radiation protection should still be followed carefully at all times. This is even more important with regard to the use of ionising radiation in children. Children’s tissues are much more susceptible than that of adults to any biological effects of ionising radiation. In dentistry so-called stochastic or probabilistic effects are those we should take into account. The assumption that these effects may take place are derived from the so-called linear no-threshold model, which is based on effects occurring from high exposures, such as those encountered in nuclear plants or nuclear accidents. The fact that the effects from lower energy radiation are unpredictable necessitates the paramount consideration for any dental care provider to keep radiation to a minimum and not to use too many radiographs. As mentioned before, the three basic principles of radiation protection are paramount. Digital radiography was supposed to decrease the radiation burden to a patient, but time and experience has shown that the opposite is true. The proportion of medical exposures within the total of all exposures to ionising radiation has increased dramatically over the past 10 years. The actual reduction in radiation dose that could be achieved when switching from D-speed analogue film to phosphor storage plates (PSPP) or solid-state sensors [charged coupled devices (CCD) or complementary metal oxide semiconductors (CMOS)] has been lost because more radiographs are taken. Dentists using E-/F-speed analogue film use the same exposure parameters as those who have switched to digital, but the former do not take as many radiographs. The increase in the number of radiographs is because solid-state sensors do not always cover the whole area of interest (there is a substantial discrepancy or dead zone between the exterior surface dimensions of the sensor and the real interior sensor surface), so multiple radiographs of the same area are needed. Another reason is that practitioners erroneously assume that the reduction in radiation dose compensates for two or three digital radiographs (CCD/CMOS or PSPP). A third reason is that it is very tempting to push the button once more as it is hoped that just a bit better image may be achieved than the one that occured on the monitor initially. This is a false feeling of safety or security. Digital imaging is therefore not always as safe as assumed. That same false feeling of ‘‘it is okay’’, is clearly a misconception and also occurs with cone-beam computed tomography (CBCT), which is promoted commercially as a technique with a low radiation dose. The latter is true only when compared to medical CT, definitely not when compared with intra-oral peri-apical imaging. As ever in life, comparisons are relative. J. K. M. Aps (&) The Center for Pediatric Dentistry, University of Washington, 6222 NE 74th Street, Seattle, WA 98115, USA e-mail: johan.apsdmfr@hotmail.com