Radiation can be a frightening topic to our patients and healthcare professionals because it is not well understood.

This short article will aim to enlighten you on the reality of radiation in dental imaging.

The harm of radiation is measured in an unit called Sievert. You will see this figure quoted in radiation dose of all CBCT machinery. Most CBCT has a radiation dose of 30 to 300uSV depending on FOV, exposure time, voltage settings. Below is a chart showing common reference levels for radiation.

The reality is the harm of radiation at doses we deal with in everyday life is so small that it is entirely theoretical. Our understanding of radiation harm is extrapolated from events such as Hiroshima and Chernobyl. For example, if we observed 1 in 100 patients during the Chernobyl fall out developed denovo cancer in 5 years, at exposure level of 350mSV, it is then extrapolated and assumed at 3.5mSV (100 times less dose) it would be 1 in 100000 developing cancer in 5 years.

While a highly difficult task, an attempt has been made to observed the population effect of radiation through a very large epidemiology study conducted by University of Melbourne. Mattias et al, showed an excess of 9 cases of cancer per 100,000 patient who had a medical CT compared to those who didn’t with radiation exposure of 5mSV. CBCT is 10 to 100x less radiation dose than this! Extrapolated that’s 9 cancers in 1,000,000 people. The chance of getting cancer from CBCT is comparable to winning lotto.

Given these information, we should be comforted in that we would be causing very little harm to our patients by referring them for CBCT study. But as medical prescribers of radiation, we should remain vigilante and always weigh up the benefits of performing dental imaging to its harm. If the imaging study is unlikely to alter management plans or treatment outcome, we should still try to avoid exposing our patient, especially children and woman, to unnecessary radiation.

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