Modern Dentist Magazine Edition 5
Are there any areas where public perception may be improved in the profession?
Are you sure I should be having this x-ray – radiation is dangerous isn’t it? This (or some similar comment) is a question we are often told still comes from patients when we visit a practice or are doing our radiation protection training courses. So what is the truth?

Well what we do certainly know is that ionising radiation (of which x-rays are of course an example) can be carcinogenic – the so-called ‘Stochastic’ effect of radiation. This is a ‘chance’ effect in that it may or may not happen, but as the dose increases the more likely it is to happen. Indeed in 2016 researchers from the Wellcome Trust Sanger Institute announced that they had been able to identify in human cancers two characteristic patterns of DNA damage caused by ionising radiation – and these ‘fingerprints’ may well make it possible for doctors to identify which tumours have been caused by that radiation.

High doses of radiation can also cause effects such as reddening of the skin (erythema), cataracts and radiation burns – these are ‘Deterministic’ effects that will happen but only after you get above a certain (threshold) level of dose. As these threshold doses are so high – generally in the region of Sieverts worth of dose – no one in a dental practice will ever get one of these effects unless there is some kind of an accident and one of your x-ray units kept on exposing for a long period of time without anyone being aware of this happening.

So the paramount concern in dental practice (whether staff member or patient) is the possibility of the induction of a cancer – that is an effect that is related to the level of dose. The current International Commission for Radiological Protection (ICRP) calculation from all the current data indicates that 5 people out of 100 subjected to 1 Sievert of dose would be expected to develop a cancer (5% per Sievert).

So what does that make the chance of cancer induction in a dental imaging situation? Extremely low is the simple answer because typical dental doses are of the order of Microsieverts (that is millionths of a Sievert). Public Health England put the chance in dental imaging somewhere between one in a million to one in ten million and with the more recent continuing reduction in doses (due in particular to the institution of digital image production/processing systems) the risk is being lowered still further. Cone beam CT unit systems are now also being produced with ‘ultra-low dose’ settings which are enabling the dose to the patient for 3D imaging to be reduced to the equivalent of one or 2 typical panoramic images.

Yes dental imaging is still a high frequency, low dose technique, but the law quite clearly requires doses to be kept as low as reasonably practicable (the ALARP principle under the IRR17) and to the minimum consistent with the diagnostic purpose (essentially the same principal under the IRMER17 regulations) – and the Dental Professions should be proud of themselves with their contribution to this. When I first started advising in this area we used to describe the dose from a set of bitewings to be equivalent to the dose from cosmic radiation from a flight to Madrid in Spain – it’s now more like the dose from cosmic radiation from half that distance (London to Frankfurt).

So however you explain it, the public and patient perception of the general/medical risk from ionising radiation needs to be changed – and in parallel to this the dental professions reduction of doses to staff and the general public and the optimisation of doses to patients needs to be lauded and applauded.

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