Evaluation of bacteria-induced enamel demineralization using optical profilometry

ObjectivesStreptococcus mutans is considered a major causative of tooth decay due to its ability to rapidly metabolize carbohydrates such as sucrose. One prominent excreted end product of sucrose metabolism is lactic acid. Lactic acid causes a decrease in the pH of the oral environment with subsequent demineralization of the tooth enamel. Biologically relevant bacteria-induced enamel demineralization was studied.MethodsOptical profiling was used to measure tooth enamel decay with vertical resolution under one nanometer and lateral features with optical resolution as a result of S. mutans biofilm exposure. Comparison measurements were made using AFM.ResultsAfter 72 h of biofilm exposure the enamel displayed an 8-fold increase in the observed roughness average (Ra), as calculated over the entire measured array. Similarly, the average root mean square (RMS) roughness, RRMS, of the enamel before and after biofilm exposure for 3 days displayed a 7-fold increase. Further, the direct effect of chemically induced enamel demineralization using biologically relevant organic acids was shown. Optical profiles of the enamel surface after addition of a 30% lactic acid solution showed a significant alteration in the surface topography with a corresponding increase in respective surface roughness statistics. Similar measurements with 10% citric acid over seconds and minutes give insight into the demineralization process by providing quantitative measures for erosion rates: comparing surface height and roughness as metrics.SignificanceThe strengths of optical profilometry as an analytical tool for understanding and analyzing biologically relevant processes such as biofilm induced tooth enamel demineralization were demonstrated.