The relationship between sucrose concentration and cariogenic potential was studied in situ. Adult volunteers wore intraoral palatal appliances containing human dental enamel blocks, which were extraorally submitted 8 times a day for 14 days, to the treatments: deionized distilled water and sucrose solutions from 1 to 40%. The biofilm formed was analyzed with respect to acidogenicity and biochemical composition; enamel demineralization was evaluated by microhardness. The results showed that 1% sucrose is less cariogenic than 5% or higher concentrations, although sucrose solution at 40% was still able to increase the concentration of insoluble polysaccharide in the biofilm formed. The findings suggest that the threshold of sucrose solution concentration for the formation of a cariogenic biofilm is 5%, which provided the same cariogenic potential as that observed for 10 and 20% sucrose solution.

The cariogenicity of starch alone or in combination with sucrose is controversial and the effect on dentine demineralization and on the dental biofilm formed has not been explored under controlled conditions. A crossover, single-blind study was conducted in four steps of 14 days each, during which 11 volunteers wore palatal appliance containing 10 slabs of root dentine to which the following treatments were applied extraorally: 2% starch gel-like solution (starch group); 10% sucrose solution (sucrose group); a solution containing 2% starch and 10% sucrose (starch + sucrose group), or 2% starch solution followed by 10% sucrose solution (starch → sucrose group). On the 14th day of each phase the biofilms were collected for biochemical and microbiological analyses, and dentine demineralization was assessed by hardness. A higher demineralization was found in dentine exposed to sucrose and starch sucrose combinations than to starch alone (p < 0.01), but the sucrose-containing groups did not differ significantly from each other (p > 0.05). The concentrations of soluble and insoluble extracellular polysaccharides (EPS), and the proportion of insoluble EPS, were lower in the biofilm formed in presence of starch (p < 0.01) than in those formed in the presence of sucrose or sucrose/starch combinations; however, no significant difference was observed among the groups containing sucrose (p > 0.05). RNA was successfully isolated and purified from in situ biofilms and only biofilms formed in response to sucrose and starch/sucrose combinations showed detectable levels of gtfB and gtfC mRNA. The findings suggest that the combination of starch with sucrose may not be more cariogenic to dentine than sucrose alone.

The combination of starch and sucrose has profound effects not only on the composition and structure of the polysaccharide matrix but also on gene expression of S. mutans within biofilms, which may enhance the cariogenic potential of dental biofilms.

Irradiation with an Er:YAG laser is appropriate for caries removal in primary teeth.

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Staphylococcus aureus is an important pathogen that has shown ability to establish biofilm communities that can represent a source of contamination and resistance in food processing. Rhamnolipids (RL) have attracted attention as candidates to replace synthetic surfactants, exhibiting high surface activity combined with its microbial origin, biodegradability, and low toxicity. In this work, an RL biosurfactant was evaluated regarding its ability to disrupt or remove S. aureus biofilms established on polystyrene plates using nutrient broth and skim milk as the growth media. Rhamnolipid treatment was performed at different surfactant concentrations and temperatures. Rhamnolipid removes up to 88.9% of milk-based biofilms, whereas for nutrient medium 35% removal was attained. The RL concentration affects the disruption of nutrient medium-based biofilms. High carbohydrate content of milk-based biofilms favors disruption by RL and the organization of RL molecules in solution showed a predominance of aggregates from 1 to 10 and 100 to 1,000 nm in all conditions studied. Biofilm disruption activity of RL is nutrient-specific and dependent on biofilm matrix composition. Staphylococcus aureus biofilms established in milk were significantly reduced using RL at low concentrations and temperatures. These findings suggest potential application of RL in milk (dairy) processing industries where low temperatures are applied.

Since lactose has been used as an excipient in powdered sweeteners, we evaluated its effect on dentine demineralization, in an in situ crossover study. Twelve adult volunteers wore palatal appliances containing 4 blocks of bovine root dentine, which were submitted 4 times a day to: distilled water (negative control), aqueous solution of powdered sweetener (Zero Cal^®; experimental group), 1.5% lactose solution (active group), 1.5% sucrose solution (positive control). After 15 days, microhardness was determined on dentine surface (SMH) and on the sectioned blocks (CSMH). All groups presented statistical differences in SMH before and after the treatments; water increased, while sweetener, lactose and sucrose decreased SMH. By CSMH, the only significant difference was observed after sucrose treatment. The data suggest that sweeteners containing lactose as a bulking agent may be cariogenic for root dentine.

No abstract