Mapping the mineral architecture in biofilm induced WSEL by SEM-EDS

Objective: To map the architectural pattern of demineralized enamel in biofilm induced white spot enamel lesions (WSELs) Ca, P and F elements were analyzed. Methods: Circular WSELs were induced on bovine enamel coupons by Streptococcus mutans MT8148 (S. muatns) biofilms in vitro for time intervals of 5, 10, 20, 30 and 40 hours. After analyzing by QLF resin embedded coupons were trimmed longitudinally up to the middle of each WSEL. In the present study, coupons were examined by an SEM S-4500 (Hitachi, Japan) and each surface was analyzed by an energy dispersive X-ray spectroscope (EDS) EMAX-7000 (Horiba, Japan). The Ca, P and F elements were mapped on the scan line from secondary electron images of the enamel coupons. In addition, the depth of the WSEL, the actual white part that lost most of the mineral particles was also measured on SEM photomicrographs by using SemAfore software (Jeol, Finland). Experiments were repeated for three times (n=5) and numerical data were analyzed by One-way ANOVA and Tukey's HSD. Results: SEM and EDS data showed that there was about four fold increase in lesion depth (µm) after 40 hrs (60.23±2.17) from that of after 10 hrs (14.83±1.4) in WSEL, difference was significant (p<0.05). The WSEL maintained similar architecture and depth increased as Ca and P elements continuously dissolved from prism rods with the increase of time. However, parts of these dissolved elements got tapped at the edge that appeared as a peak on EDS element line mapping. Conclusion: Ca and P elements equally get dissolved from the prism rods and produce similar architectural landmark on the demineralized enamel and some of the element particles get trapped in mesh of crystallites at the edge below biofilms. This study was supported by COE program for FRMDRTB at TMDU and Japan Monbukagaku Research Grant (16390544).