Effects of Sodium Hexametaphosphate and Fluoride on the pH and Inorganic Components of Streptococcus mutans and Candida albicans Biofilm after Sucrose Exposure

Abstract

In order to improve the anticaries effects of fluoridated products, the supplementation of these products has been considered a promising alternative for caries control. This study evaluated the effects of sodium hexametaphosphate (HMP) and/or fluoride (F) on the inorganic components and pH of Streptococcus mutans and Candida albicans dual-species biofilms. The biofilms were treated 72, 78, and 96 h after the beginning of their formation with 0.25, 0.5, or 1% HMP-containing solutions with or without F (500 ppm, as sodium fluoride). F-containing solutions (500 ppm and 1100 ppm) and artificial saliva were used as controls. The biofilms were exposed to a 20% sucrose solution after the third treatment. Along with the biofilm pH, the concentrations of F, calcium, phosphorus (P), and HMP were determined. HMP, combined with F, increased F levels and decreased P levels in the biofilm fluid compared to that of the solution with 500 ppm F. Exposure to sucrose decreased the concentrations of all ions in the biomass, except for HMP; 1% HMP, combined with F, promoted the highest pH. It can be concluded that HMP affected the inorganic composition of the biofilm and exerted a buffering effect on the biofilm pH.

Buffering Capacity and Effects of Sodium Hexametaphosphate Nanoparticles and Fluoride on the Inorganic Components of Cariogenic-Related Biofilms In Vitro

“…The present study was motivated by the remarkable effects of HMPmicro on the inorganic composition and pH of cariogenic biofilms in vitro [ 14 ], along with the higher reactivity of HMPnano over micrometric particles [ 16 ]. In comparison to HMPmicro, HMPnano had a higher buffering effect on dual-species biofilms of S. mutans and C. albicans , which was potentiated by F, and increased P levels in both the biofilm biomass and biofilm fluid, without reducing F levels in these compartments.…”

“…In line with such data, the higher biofilm pH observed for the groups exposed to HMP-containing solutions is possibly related to the buffering ability of this phosphate due to its chelating property, according to which HMP in the biofilm fluid leads to the binding of HMP to H + , and of Na + to OH − [ 21 ]. The possible formation of HPO 4 2− might also have played an important role, given its substantial buffering capacity [ 14 , 21 ]. In addition, these effects were further enhanced by the addition of F, given that combined treatments of HMP and F led to a significantly higher biofilm pH in comparison to their counterparts without F, for both concentrations and particle size of the phosphate.…”

“…In fact, such an additive effect was even more notable when HMP was administered at the highest concentration, since treatments with HMP at 1% combined with F promoted a significantly higher pH in comparison to the positive control (i.e., biofilms treated with 1100 ppm F). Although the actual mechanism of the interaction of HMP and F is still unclear, recent data showed that co-administration of the two actives significantly increased the degree of saturation of HF° in the biofilm fluid in relation to hydroxyapatite, in comparison to the compounds alone [ 14 ].…”

“…This has prompted the investigation of new strategies, including the supplementation of fluoridated products with different compounds, such as sodium hexametaphosphate (HMP), an inorganic cyclophosphate salt, which is known to increase the permeability of the microbial wall and to disperse the biofilm [ 12 , 13 ]. Recent data evaluating the activity of conventional/micro-sized HMP (HMPmicro) on dual-species biofilms of S. mutans and C. albicans demonstrated that a solution containing HMPmicro in combination with F substantially affected the inorganic components of the biofilms and promoted an enhanced buffering effect in comparison to a 1100 ppm F solution [ 14 ]. In addition, it was demonstrated that the incorporation of HMP nanoparticles (HMPnano) to fluoridated toothpastes led to superior protective effects against enamel demineralization, and reduced the production of extracellular polysaccharides by biofilms in situ, in comparison to fluoridated toothpastes containing HMPmicro [ 15 ].…”

“…Considering the promising effects of HMPmicro on the inorganic components of biofilms [ 14 ], in addition to the substantial protective activity of HMPnano on enamel [ 15 ] and on the viability and virulence of cariogenic-related biofilms [ 16 ], it would be interesting to evaluate the effects of HMPnano on the pH, and on the F, calcium (Ca), phosphorus (P), and HMP concentrations of biofilms. Thus, the aim of this study was to evaluate the effects of HMPnano, combined or not with F, on the pH and inorganic components of dual-species biofilms of S. mutans and C. albicans , prior to and after exposure to sucrose.…”