Effectiveness of chemical etching for background electron paramagnetic resonance signal reduction in tooth enamel.

A method of preparing enamel samples for electron paramagnetic resonance retrospective dosimetry that leads to a reduction of the non-radiation induced signals (background) is proposed. The method is effective in removing residual dentin and in reducing surface paramagnetic centers both native and induced by the sample preparation procedure. The main steps in the method are the use of longwave length ultraviolet light for distinguishing dentin from enamel and of chemical etching with phosphoric acid for removal of surface paramagnetic centers. Several acid concentrations and etching times were tested and the optimization of the method is illustrated in regard to both sample mass loss and background signal amplitude reduction. The best acid concentration was determined to be 42%, leading to a 30% reduction in the background electron paramagnetic resonance signal amplitude per unit mass.