Background: By means of the Electron Spin Resonance technique (EPR) it is possible to detect carbonate-related paramagnetic centers in human tooth enamel. Several arguments indicate that the radicals formed after X-ray irradiation (CO2- and CO3(3-)) are ascribed to carbonate which is the most important constituent of hydroxyapatite. There is experimental evidence that the distribution of the orientation of these centers is related to microcrystal alignment in dental enamel, which might be responsible for caries susceptibility. The results reported in the literature, however, should be interpreted very carefully.
Methods: In our own preliminary research we studied twenty-seven samples of dental enamel taken from the buccal face of upper molars. Fifteen were carious and the other ones were sound. We used the R-parameter and the S-parameter to convert our experimental results into numerical values. The R-parameters, as introduced by Cevc et al. (1976-1980) is the ratio of the amplitude for the high field and the low component of the EPR signal. The S-parameter is the ratio of the amplitude of the A2 component and the low one.
Results: No significant difference was found between the R and S-value of carious and sound dental enamel samples. The degree of microcrystal alignment in enamel of clinically sound upper molar from their buccal site is very high. However, this result is not sufficient to evaluate the caries susceptibility or the caries resistance of tooth enamel.
Conclusions: Therefore, we can conclude that it is not sufficient to ascribe the caries susceptibility to the R-value, because other factors (such as etiological factors and the structure of the teeth) should be considered.