Concentração de fluoreto em arroz, feijão e alimentos infantis industrializados

OBJETIVO: Determinar a concentração de fluoreto na refeição brasileira típica (arroz e feijão) e em alimentos infantis industrializados e estimar suas contribuições para fluorose dental. MÉTODOS: Os alimentos foram adquiridos de supermercados das cidades de Piracicaba e Campinas, SP, Brasil. Os alimentos infantis industrializados foram comprados em 2001 e o arroz e feijão em 2003, e imediatamente analisados. Foram analisadas três marcas de arroz, três de feijão e 36 amostras de alimentos infantis divididos em cinco grupos: prontos para o consumo; mingaus; alimentos formulados; leites em pó e outros alimentos. No arroz e feijão, foram determinadas as concentrações de fluoreto nas sementes "in natura" e após cozimento com água destilada ou fluoretada (0,7 ppm). Todas as análises de fluoreto foram feitas com eletrodo específico. Considerou-se 0,07 mg/kg/dia como a dose limite de exposição a fluoreto para risco de fluorose. RESULTADOS: A concentração de fluoreto encontrada nos grãos de arroz e feijão foi baixa. Porém, a concentração aumentou 100-200 vezes após cozimento em água fluoretada e mesmo assim, foi menor que a encontrada em alguns alimentos industrializados. Uma refeição com arroz e feijão preparada com água fluoretada seria responsável por 29% da dose limite de ingestão de fluoreto em termos de fluorose aceitável; a contribuição de alguns alimentos industrializados atingiria 45%. CONCLUSÕES: A alimentação típica brasileira, mesmo preparada com água fluoretada, é mais segura em termos de risco de fluorose dental que alguns alimentos infantis industrializados

The Exopolysaccharide Matrix Modulates the Interaction between 3D Architecture and Virulence of a Mixed-Species Oral Biofilm

Virulent biofilms are responsible for a range of infections, including oral diseases. All biofilms harbor a microbial-derived extracellular-matrix. The exopolysaccharides (EPS) formed on tooth-pellicle and bacterial surfaces provide binding sites for microorganisms; eventually the accumulated EPS enmeshes microbial cells. The metabolic activity of the bacteria within this matrix leads to acidification of the milieu. We explored the mechanisms through which the Streptococcus mutans-produced EPS-matrix modulates the three-dimensional (3D) architecture and the population shifts during morphogenesis of biofilms on a saliva-coated-apatitic surface using a mixed-bacterial species system. Concomitantly, we examined whether the matrix influences the development of pH-microenvironments within intact-biofilms using a novel 3D in situ pH-mapping technique. Data reveal that the production of the EPS-matrix helps to create spatial heterogeneities by forming an intricate network of exopolysaccharide-enmeshed bacterial-islets (microcolonies) through localized cell-to-matrix interactions. This complex 3D architecture creates compartmentalized acidic and EPS-rich microenvironments throughout the biofilm, which triggers the dominance of pathogenic S. mutans within a mixed-species system. The establishment of a 3D-matrix and EPS-enmeshed microcolonies were largely mediated by the S. mutans gtfB/gtfC genes, expression of which was enhanced in the presence of Actinomyces naeslundii and Streptococcus oralis. Acidic pockets were found only in the interiors of bacterial-islets that are protected by EPS, which impedes rapid neutralization by buffer (pH 7.0). As a result, regions of low pH (<5.5) were detected at specific locations along the surface of attachment. Resistance to chlorhexidine was enhanced in cells within EPS-microcolony complexes compared to those outside such structures within the biofilm. Our results illustrate the critical interaction between matrix architecture and pH heterogeneity in the 3D environment. The formation of structured acidic-microenvironments in close proximity to the apatite-surface is an essential factor associated with virulence in cariogenic-biofilms. These observations may have relevance beyond the mouth, as matrix is inherent to all biofilms

Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation

Relationship between stressful situations, salivary flow rate and oral volatile sulfur-containing compounds

The relationship between stress, salivary flow rate and oral volatile sulfur-containing compounds (VSCs) is not clearly established. Two stressful situations were studied: psychological stress caused by a biochemistry examination (Study I) and psychophysiological stress caused by premenstrual syndrome (PMS) (Study II). Seventy-one undergraduate dental students took part in Study I and VSCs were measured 1 wk before the examination, on the day of examination and I wk after. In Study II, 50 women were selected (23 with and 27 without PMS) and the measurements were made during non-menstrual, premenstrual and menstrual stages. Unstimulated salivary flow was determined in the subjects of both studies. On the day of the biochemistry examination, VSCs significantly increased and salivary flow decreased compared with baseline values. Women with PMS showed higher VSC concentrations during the premenstrual stage than those without PMS (P < 0.05), but the salivary flow was not statistically different. A change in VSCs was observed during different stages of the menstrual cycle for the groups of women, but the salivary flow did not change. The results suggest that a stressful situation can be a predisposing factor for the increase of VSCs in the mouth air, but the mechanism cannot be simply explained by reduction of the salivary flow.110533734

The influence of mutanase and dextranase on the production and structure of glucans synthesized by streptococcal glucosyltransferases

Glucanohydrolases, especially mutanase [alpha-(1 --> 3) glucanase; EC 3.2.1.59] and dextranase [alpha-(1 --> 6) glucanase; EC 3.2.1.11], which are present in the biofilm known as dental plaque, may affect the synthesis and structure of glucans formed by glucosyltransferases (GTFs) from sucrose within dental plaque. We examined the production and the structure of glucans synthesized by GTFs B (synthesis of alpha-(1 --> 3)-linked glucans) or C [synthesis of alpha-(1 --> 6)- and alpha-(1 --> 3)-linked glucans] in the presence of mutanase and dextranase, alone or in combination, in solution phase and on saliva-coated hydroxyapatite beads (surface phase). The ability of Streptococcus sobrinus 6715 to adhere to the glucan, which was formed in the presence of the glucanohydrolases was also explored. The presence of mutanase and/or dextranase during the synthesis of glucans by GTF B and C altered the proportions of soluble to insoluble glucan. The presence of either dextranase or mutanase alone had a modest effect on total amount of glucan formed, especially in the surface phase; the glucanohydrolases in combination reduced the total amount of glucan. The amount of (1 --> 6)-linked glucan was reduced in presence of dextranase. In contrast, mutanase enhanced the formation of soluble glucan, and reduced the percentage of 3-linked glucose of GTF B and C glucans whereas dextranase was mostly without effect. Glucan formed in the presence of dextranase provided fewer binding sites for S. sobrinus; mutanase was devoid of any effect. We also noted that the GTFs bind to dextranase and mutanase. Glucanohydrolases, even in the presence of GTFs, influence glucan synthesis, linkage remodeling, and branching, which may have an impact on the formation, maturation, physical properties, and bacterial binding sites of the polysaccharide matrix in dental plaque. Our data have relevance for the formation of polysaccharide matrix of other biofilms. (C) 2004 Elsevier Ltd. All rights reserved.339122127213