Developing Novel Mouth Models for Testing EPR Tooth Biodosimetry Systems

Objectives: In the event of a large-scale radiation disaster, people may be exposed to unknown amounts of radiation. Because doses above a threshold of 2 gray may require medical monitoring or treatment, it is required to assess each individual’s dose quickly and reliably. We have established the feasibility of such biodosimetry, using electron paramagnetic resonance (EPR) to measure upper incisors in vivo. Since the EPR signal in tooth enamel is related linearly to total dose and is very stable, a measurement taken any time after the radiation event provides a direct dose estimate. In the process of developing and improving the instrument and measurement techniques to obtain reliable and accurate dose estimates, it is desirable to conduct systematic and controlled studies. Since it is not possible to irradiate people for such studies, it is necessary to develop a mouth model to simulate the human oral environment.
Methods: We simulated soft tissue using gelatin and ethylene glycol and confirmed its stability over 6 months both physically and electrically. Regression analysis was performed to characterize changes in the materials over time. Simulated soft tissues were re-fabricated and installed into a mouth model with a tooth-sized gap between 2 upper incisors. 5 teeth, each irradiated to 0, 2, 4, 6 or 10 gray, were placed in the gap and measured to obtain the dose-response curve.
Results: The simulation materials remained stable for 6 months both physically and electromagnetically. The dose-response curve obtained from the mouth model was linear as expected, and the slope and intercept were similar to that for in vivo measurements.
Conclusions: We succeeded in developing a mouth model with materials that reflect key oral electromagnetic properties for EPR biodosimetry. The mouth model can be used as an alternative to human subjects to test the instrument’s accuracy and precision.