Enamel demineralization and remineralization pH cycling models in vitro: a SEM-EDX and FTIR study

The aim of the present study was to investigate the efficiency of pH cycling models to induce enamel experimental subsurface lesions and to enhance enamel remineralization in vitro. Enamel blocks (n = 50) were obtained from the buccal surface of human permanent incisors and canines and assigned to five independent groups (n = 10/gp). In Group D1, enamel blocks were subjected to a demineralizing solution, and in Group D2 a demineralization pH cycling model was used to induce an experimental subsurface lesion. In Group R, enamel blocks with subsurface-induced lesions were treated with fluoride varnish and submitted to a remineralization pH cycling model. Enamel blocks were investigated with scanning electron microscope-energy-dispersive X-ray (SEM-EDX) and Fourier transform infrared spectroscopy (FTIR). Quantitative data were statistically analyzed (repeated measures ANOVA, Bonferroni, p < 0.05). EDX revealed significant differences with respect to atomic percentage (At%) of calcium, phosphate, fluorine (F), carbon, and oxygen between groups (p < 0.05; repeated measures ANOVA). Group R revealed the highest F (At%) on the enamel surface (0.71 ± 0.2) (p < 0.05). FTIR revealed variations in PO₄^3- and CO₃^2- characteristic bands between groups in correlation with enamel surface demineralization and remineralization. In this study, the demineralization pH cycling model (Group D2) investigated with SEM-EDX and FTIR simulated chemical and structural characteristics of enamel natural subsurface carious lesions. Surface demineralization was created in enamel when a demineralization solution was used for induction of a caries-like lesion (Group D1), without any subsurface created lesion. Remineralization pH cycling model tested in Group R revealed an effective enamel remineralization in SEM-EDX and FTIR.