In vivo measurements of EPR signals in whole human teeth

Low-frequency EPR has the potential advantage of making accurate and sensitive measurements of absorbed radiation dose in teeth in situ. We report here on measurements within the human mouth in volunteers using 1200 MHz EPR, with an irradiated tooth in a special holder. We obtained a signal/noise ratio within 50% of that seen when the same sample was measured extraorally. The intraoral signal/noise can be improved and can be reduced further with optimization of conditions and use of more specifically designed and optimized resonators that fit within the mouth, probing 1-4 teeth, and can make the measurements in molars or incisors. The presence of amalgam fillings did not significantly impact the accuracy of measurements in those teeth or in adjacent teeth. These initial results make us optimistic that intra-oral measurements of the teeth will be feasible for accurate determination of exposures over the whole range in which acute clinical effects are possible.