Communication of radiation risk to a patient is part of the process of
informed consent. In order to achieve this there are some fundamental
goals to achieve – the amount of radiation, the risk in terms of fatal
cancer and comparing those risks to everyday activities a patient
chooses to perform.

Risk versus benefit is the keystone to understanding when it is appropriate to expose a patient. This can be demonstrated by the case of when is it appropriate to expose a
pregnant woman? If a pregnant woman presents for dental examination and has no clinical signs or symptoms of disease then radiation exposure should be delayed until after the baby is born.

However, if a woman who is 10 weeks pregnant presents is complaining of a vague pain on the right side of the face and no clinical cause for the pain can be found, then is quite appropriate to take a panoramic radiograph to see if an unerupted third molar  is present. If  one is present and further palpation reveals a tender area from pericoronitis then prescribing an antibiotic, referral to an Oral Surgeon for a removal under local anesthetic when the acute infection has subsided, is the
management of choice.

Failure to diagnose the pericoronitis through avoiding an appropriate radiographic examination could have led to a delay in treating the acute infection  which could have become severe with fever, swelling, abscess formation and its drainage under a
general anesthetic (GA). GAs are potentially  more hazardous with a
risk of death 7 in 1,000,000 (1) to a woman and her fetus than a
panoramic radiograph with a 1 in 1,000,000 of causing fatal cancer
(2). In this situation there is a clear benefit to risk ratio for a
radiographic examination.

How much risk of fatal cancer is associated with dental radiographic
Full mouth series (20 exposures) digital sensors or F speed film with
a rectangular collimator is 2 in 1,000,000. A collimator is a tube
that reduces the spread of x-rays reducing risk. A rectangular
collimator is better than a round one.
Full mouth series (20 exposures) digital sensors or F speed film with
a round collimator is 9 in 1,000,000.
* Full mouth series (20 exposures) D speed film with a round
collimator is 21 in 1,000,000.
Digital panoramic radiograph is  1 in 1,000,000.
Digital cephalometric radiograph 0.3 in 1,000,000.

These are all risks associated with a single examination and if you
have repeated examinations the odds increase proportionally.

How does this compare with a common activity such as driving? In your
lifetime there is a 1 in 113 chance you will die in a car crash (3).

As dentists we are obliged to keep the radiation risk as low as
reasonably achievable (ALARA) and on a population basis 160,000
dentists are likely to produce a few cancer-related deaths per year.

However, if X-rays are used cautiously where the clinical risks are
less than the benefits then X-ray examinations should be performed.

1. Lienhart A et al. Survey of Anesthesia-related Mortality in France.
Anesthesiology 2006; 105:1087–97
2. Ludlow JB et al Patient risk related to common dental radiographic
examinations. JADA 2008;139(9):1237-1243
3. National safety council.
(accessed 3/26/2016)

Dr. Douglas K Benn

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