Iron effect on enamel demineralization and remineralization in vitro

Objectives: The aim of the present study was to evaluate the effect of ferrous sulphate (FeSO4.7H2O), using a pH cycling model. Methods: Enamel blocks (4x4mm) had their enamel surfaces sequentially polished, allowing selection of blocks by determination of the initial surface microhardness (SMH,n=100). Caries lesions were produced only in fifty enamel blocks and the post caries SMH were determined (SMH lesion,n=50). Half of the enamel blocks were submitted to a demineralization pH-cycling (DE,n=50) during 5 days and the other half (caries lesion) to a remineralization pH-cycling (RE,n=50) during 6 days. The treatments were performed with different concentrations of FeSO4.7H2O solutions (0.333; 0.840; 18.0 and 70.0µg/mL) and a placebo group (deionized water), twice a day. Then the final SMH were determined to calculate the percentage of surface microhardness change (%SMH), and the integrated mineral loss (DZ) was calculated. Analysis of fluoride (F), calcium (Ca), phosphorus (P) and iron (Fe) present in enamel (µg/cm2) were measured after acid biopsy. Data distribution was heterogeneous and were analyzed using Kruskall-Wallis test (p<0.05). Results: In DE pH cycling, the group treated with 18,0µgFe/mL presented better results of %SMH and DZ (p>0,05) when compared to the other groups. In RE pH cycling, placebo group showed better results (p<0,05). A decline in Ca and P concentration (p<0.05) was observed when Fe concentration increased. There was no significant difference on F concentration (p>0.05) and an increase on iron concentration (p<0.05), independently of the experiment. Conclusion: The results suggest that iron reduces mineral loss, however, it interferes in the remineralization process, not allowing it to occur.