Interview: How dental restorative materials could provide radiation information

Dental Tribune International

Tue. 4. July 2017

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In accidents or terror attacks suspected to involve radioactive substances, it can be difficult to determine whether people nearby have been exposed to radiation. By analysing materials or objects that come in close contact with the human body, it is possible to retrieve important information on radiation exposure. Dental Tribune Online spoke with medical radiation physicist Dr Therése Geber-Bergstrand, who has investigated the potential of teeth and dental restorative materials, among others, as indicators of radiation exposure.

Dr Geber-Bergstrand, you investigated the possibility of using materials in close contact with the body for measuring possible exposure to radiation. What was the outcome of this research regarding teeth and dental restorative materials?

Both teeth and some dental restorative materials—ceramics—have been studied for this purpose before. Though all measurements were performed on extracted teeth, all materials were dry when exposed to radiation. In my research, I wanted to mimic a more authentic irradiation situation; thus, I irradiated the teeth and restorative materials immersed in different fluids, which were water, ultra-pure water and human saliva. Furthermore, I included a previously unstudied restorative material: composite. The outcome was that the signal I measured as a result of the exposure to radiation disappeared when the teeth were irradiated in a wet condition, despite the type of fluid used. However, the signal from the restorative materials did not disappear. All the materials also showed very good sensitivity in the dose range of interest. Different restorative materials could therefore be very informative after an accident or terror attack in which members of the general public may have been exposed to ionising radiation.

Which methods did you use for the research? 

The technique used is called optically stimulated luminescence. In short, one could say that, when some kinds of material are exposed to ionising radiation, some of the radiation energy is stored in the material. To release the energy, and thus measure it, the material is stimulated with blue light. The stored energy is then released as light, but with a different wavelength, and by measuring the intensity of the released light, an estimation of the amount of radiation to which the material has been exposed can be obtained. The fact that light is used to release the stored energy means that the material has to be protected from light until read-out. For dental restorative materials that means using material from the molars.

How would it technically work to use teeth or dental restorative materials as a dosimeter? 

In the future, it could perhaps be possible to read out the signal in vivo using light guides, but in the current situation, the filling would have to be removed by a dentist, preferably under red light conditions. The sample would then be sent to our laboratory, and once the samples have been received, it would take 1–2 hours before a dose estimation is obtained. Compared with many other methods to estimate individual exposure, this is very rapid.

Which of the other materials you investigated did you find to be useful for measuring radiation exposure, and how do dental restorative materials compare to these regarding effectiveness?

I investigated table salt, various components of mobile phones, teeth and dental restorative materials, desiccants and some drugs. Salt had by far the best signal per unit dose, but the problem is that people do not carry salt packages around and this makes individual dose estimations more difficult. Components of mobile phones and dental restorative materials were more or less equally sensitive. An advantage of the restorative materials, however, is that they always are at the same position relative to the rest of the body, making the dose estimation more straight forward. In comparison, a mobile phone could be kept in a trouser pocket, breast pocket or handbag. Desiccants were the least sensitive and would in the current situation work as complementary materials.

Thank you very much for the interview.

The doctoral dissertation, titled “Optically Stimulated Luminescence for Retrospective Radiation Dosimetry. The Use of Materials Close to Man in Emergency Situations”, can be accessed here.