The Route of Sucrose Utilization by Streptococcus mutans Affects Intracellular Polysaccharide Metabolism.

Streptococcus mutans converts extracellular sucrose (Suc) into exopolysaccharides (EPS) by glucosyl-transferase and fructosyl-transferase enzymes and internalizes Suc for fermentation through the phosphotransferase system (PTS). Here, we examined how altering the routes for sucrose utilization impacts intracellular polysaccharide [IPS; glycogen, (glg)] metabolism during carbohydrate starvation. Strain UA159 (WT), a mutant lacking all exo-enzymes for sucrose utilization (MMZ952), and a CcpA-deficient mutant (∆ccpA) were cultured with sucrose or a combination of glucose and fructose, followed by carbohydrate starvation. At baseline (0h), and after 4 and 24h of starvation, cells were evaluated for mRNA levels of the glg operon, IPS storage, glucose-1-phosphate (G1P) concentrations, viability, and PTS activities. A pH drop assay was performed in the absence of carbohydrates at the baseline to measure acid production. We observed glg operon activation in response to starvation (p<0.05) in all strains, however, such activation was significantly delayed and reduced in magnitude when EPS synthesis was involved (p<0.05). Enhanced acidification and greater G1P concentrations were observed in the sucrose-treated group, but mostly in strains capable of producing EPS (p<0.05). Importantly, only the WT exposed to sucrose was able to synthesize IPS during starvation. Contrary to CcpA-proficient strains, IPS was progressively degraded during starvation in ∆ccpA, which also showed increased glg operon expression and greater PTS activities at baseline. Therefore, sucrose metabolism by secreted enzymes affects the capacity of S. mutans in synthesizing IPS and converting it into organic acids, without necessarily inducing greater expression of the glg operon.

Socioeconomic inequalities in the use of dental care services during early childhood: an epidemiological survey.

BACKGROUND: The use of dental care services contributes to the improvement of children's healthy behaviors, reducing the prevalence of future dental problems. In this way, the purpose of this study was to describe the use of dental care service during early childhood and the possible socioeconomic inequalities in this use. DESIGN: Data from the Brazilian Oral Health Survey (SB Brasil, 2010) were used. Interviews with the children's parents and clinical examinations with the children were conducted in a 5-year-old representative sample. Descriptive, bivariate and multiple hierarchical statistical analyses were applied. RESULTS: Of the 7241 children included, 3812 (53.2%) had used dental care services at least once in their lifetimes, and 1872 (48.8%) had used services for check-up/prevention. The use of dental services was greater among children with a higher family income (P < 0.05). The use of check-ups was lower among children with non-White skin color (Black and Browns) and among those who did not live in state capitals (P < 0.05). Clinical conditions and self-perception were also associated with the use (P < 0.05). CONCLUSION: Socioeconomic differences in the general use of dental care and in its use for check-ups were identified during early childhood, indicating the presence of inequalities.

Electrochemical behavior of titanium exposed to a biofilm supplemented with different sucrose concentrations.

STATEMENT OF PROBLEM: Biofilms can reduce the corrosion resistance of titanium because of the bacterial metabolism of fermentable carbohydrates, including sucrose. However, studies evaluating whether biofilms exposed to higher sucrose concentrations can affect the electrochemical behavior of titanium are lacking. PURPOSE: The purpose of this in vitro study was to test the electrochemical behavior of titanium previously exposed to biofilm supplemented with different sucrose concentrations. MATERIAL AND METHODS: Streptococcus mutans UA159 biofilms were formed on commercially pure titanium (cpTi) surfaces and supplemented constantly with different sucrose concentrations (0%, 1%, 10%, and 40%) for 7 days (experimental groups) (n=12 per group). CpTi disks without biofilm were used as a control (n=12). The standard electrochemical tests open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic curve were performed. Data were submitted to ANOVA and the Tukey honestly significant difference (HSD) tests (α=.05). RESULTS: The biofilm exposed to sucrose had an increased biofilm dry weight (P<.05). The polysaccharide amount and the pH drop were higher in the groups exposed to sucrose (P<.05). No difference was noted between the control and experimental groups for the electrochemical properties of cpTi (P>.05). CONCLUSIONS: Biofilms exposed to greater carbohydrate concentration did not alter the corrosive behavior of titanium.

Dose-response effect of chlorhexidine on a multispecies oral biofilm formed on pure titanium and on a titanium-zirconium alloy.

This study aimed to test the dose-response effect of chlorhexidine on multispecies biofilms formed on commercially pure titanium (cpTi) and titanium-zirconium (TiZr) alloy. Biofilms were formed on cpTi and TiZr discs and treated two times per day with five different chlorhexidine concentrations (0.12, 0.20, 0.50, 1, 2%). The biofilms were collected for microbiological, biochemical and microscopic analyses. The significance of differences among groups was evaluated by linear regression, ANOVA, Bonferroni and Tukey tests. The mean number of colony-forming units decreased as the chlorhexidine concentration increased for both cpTi and TiZr (p < 0.05). The maximum effect was observed with the 0.5% concentration. Confocal microscopy images suggested an increase in the number of dead bacterial cells with increased chlorhexidine concentration. The biofilm pH increased after chlorhexidine exposure (p < 0.05). Chlorhexidine showed an antimicrobial dose-response effect in controlling biofilm on cpTi and TiZr. 0.5% chlorhexidine can be used to achieve the maximum antimicrobial effect on both materials.

Biofilm extracellular polysaccharides degradation during starvation and enamel demineralization.

This study was conducted to evaluate if extracellular polysaccharides (EPS) are used by Streptococcus mutans (Sm) biofilm during night starvation, contributing to enamel demineralization increasing occurred during daily sugar exposure. Sm biofilms were formed during 5 days on bovine enamel slabs of known surface hardness (SH). The biofilms were exposed to sucrose 10% or glucose + fructose 10.5% (carbohydrates that differ on EPS formation), 8x/day but were maintained in starvation during the night. Biofilm samples were harvested during two moments, on the end of the 4th day and in the morning of the 5th day, conditions of sugar abundance and starvation, respectively. The slabs were also collected to evaluate the percentage of surface hardness loss (%SHL). The biofilms were analyzed for EPS soluble and insoluble and intracellular polysaccharides (IPS), viable bacteria (CFU), biofilm architecture and biomass. pH, calcium and acid concentration were determined in the culture medium. The data were analyzed by two-way ANOVA followed by Tukey's test or Student's t-test. The effect of the factor carbohydrate treatment for polysaccharide analysis was significant (p < 0.05) but not the harvest moment (p > 0.05). Larger amounts of soluble and insoluble EPS and IPS were formed in the sucrose group when compared to glucose + fructose group (p < 0.05), but they were not metabolized during starvation time (S-EPS, p = 0.93; I-EPS, p = 0.11; and IPS = 0.96). Greater enamel %SHL was also found for the sucrose group (p < 0.05) but the demineralization did not increase during starvation (p = 0.09). In conclusion, the findings suggest that EPS metabolization by S. mutans during night starvation do not contribute to increase enamel demineralization occurred during the daily abundance of sugar.

Contextual and individual determinants of oral health-related quality of life in older Brazilians.

PURPOSE: This cross-sectional, population-based study evaluated contextual and individual determinants on the oral health-related quality of life in older Brazilians. MATERIALS AND METHODS: Data from the National Survey of Oral Health were used. The sample was selected by multi-stage probability cluster sampling, with probability proportional to size. The Oral Impacts on Daily Performance (OIDP) was used to evaluate oral health-related quality of life (OHRQoL). Contextual variables of municipalities and individual variables of older people were included. Descriptive, bivariate and multilevel analyses were conducted. RESULTS: Of the sample of 7619 older Brazilians, 45.7% was impacted by at least one of the OIDP items. The item impact average was 1.2 (95% CI 1.04-1.37). The impact on OHRQoL was lower in older Brazilians residents in municipalities with the highest value of the GINI index (contextual variable) (p = 0.007), among edentulous people (p = 0.001) and dental prosthesis users (p < 0.001). This impact was greater among older people of nonwhite skin color (p = 0.024), lower family income (p = 0.024) and dissatisfied with the oral health (p < 0.001). CONCLUSION: A high prevalence of oral problems impacting OHRQoL in older Brazilians was identified. Furthermore, the impact prevalence was related to a positive situation in contextual determinants and a negative situation for the individual, showing a social inequalities profile in relation to individual determinants.