Effect of Sucrose Containing Iron (II) on Dental Biofilm and Enamel Demineralization in situ

Abstract

Since the effect of iron (Fe) on the cariogenicity of sucrose in humans is unexplored, this study assessed in situ the effect of Fe co-crystallized with sucrose (Fe-sucrose) topically applied in vitro on the acidogenicity, biochemical and microbiological composition of the dental biofilm formed in vivo and on the demineralization of the enamel. During two phases of 14 days each, 16 volunteers wore palatal appliances containing blocks of human enamel, which were submitted to four groups of separate treatments: (1) water; (2) 20% sucrose; (3) 20% (w/v) sucrose plus 18 µg Fe/ml, and (4) 20% (w/v) sucrose plus 70 µg Fe/ml. The solutions were dripped onto the blocks 8 times per day. The biofilms formed on the blocks were analyzed with respect to acidogenicity, biochemical and microbiological composition. Mineral loss was determined on enamel by surface and cross-sectional microhardness. Lower demineralization was found in the blocks subjected to Fe-sucrose (70 µg Fe/ml) than in those treated with sucrose (p < 0.05). This concentration of Fe also reduced significantly the populations of mutans streptococci in the biofilm formed on the blocks. In conclusion, our data suggest that Fe may reduce in situ the cariogenic potential of sucrose and the effect seems to be related to the reduction in the populations of mutans streptococci in the dental biofilm formed.

The effect of iron on Streptococcus mutans biofilm and on enamel demineralization

“…7 On the other hand, the mechanism for this effect does not seem to be related to inhibition of EPS production by S. mutans GTFs. 12,13 Like prior in situ dental biofilm findings, 7 our results suggest that the reduction in demineralization cannot be explained by a direct effect on GTF activity.…”

“…7 On the other hand, the mechanism for this effect does not seem to be related to inhibition of EPS production by S. mutans GTFs. 12,13 Like prior in situ dental biofilm findings, 7 our results suggest that the reduction in demineralization cannot be explained by a direct effect on GTF activity. This absence of an effect on EPS production by S. mutans in the biofilm also cannot be explained based on the concentration of Fe used in this experiment, since at the highest concentration used (100 µg/mL = 1.8 mM), 80% EPS inhibition, found in previous in vitro studies, 13 would have been expected.…”

“…5,6,10 Furthermore, it has been shown in situ that the dental biofilm formed in humans exposed to Fe has a lower S. mutans count. 7 In terms of its mechanism of action, 8 it has been suggested that Fe may have an anticaries effect due to its ability to inhibit the F-ATPase of S. mutans. Consequently, Fe may affect the acidogenicity and aciduricity of S. mutans.…”

“…11 Moreover, it has been shown that Fe inhibits glycotransferase (GTF) enzymes produced by S. mutans in vitro 12 via an oxidative mechanism involving a Fenton-type reaction. 13 However, Fe at a concentration of 70 µg/mL (1.2 mM) has shown no in situ effect either on the acidogenicity of dental biofilm or in terms of reducing the quantity of EPS in a biofilm exposed to 10% sucrose, 7 thus suggesting the need for further studies on the mechanism of action of the anticaries effect of Fe.…”

“…Iron is an essential chemical element for humans, 4 and experiments using animal caries models 5,6 and an in situ model 7 have suggested that it can also have anticaries potential. However, the mechanism by which Fe exercises its antibacterial effect, thereby contributing to the control of caries, remains under discussion.…”