Abstract
Sucrose is an important dietary factor in cariogenic biofilm formation and subsequent initiation of dental caries. This study investigated the functional relationships between sucrose concentration and Streptococcus mutans adherence and biofilm formation. Changes in morphological characteristics of the biofilms with increasing sucrose concentration were also evaluated. S. mutans biofilms were formed on saliva-coated hydroxyapatite discs in culture medium containing 0, 0.05, 0.1, 0.5, 1, 2, 5, 10, 20, or 40% (w/v) sucrose. The adherence (in 4-hour biofilms) and biofilm composition (in 46-hour biofilms) of the biofilms were analyzed using microbiological, biochemical, laser scanning confocal fluorescence microscopic, and scanning electron microscopic methods. To determine the relationships, 2nd order polynomial curve fitting was performed. In this study, the influence of sucrose on bacterial adhesion, biofilm composition (dry weight, bacterial counts, and water-insoluble extracellular polysaccharide (EPS) content), and acidogenicity followed a 2nd order polynomial curve with concentration dependence, and the maximum effective concentrations (MECs) of sucrose ranged from 0.45 to 2.4%. The bacterial and EPS bio-volume and thickness in the biofilms also gradually increased and then decreased as sucrose concentration increased. Furthermore, the size and shape of the micro-colonies of the biofilms depended on the sucrose concentration. Around the MECs, the micro-colonies were bigger and more homogeneous than those at 0 and 40%, and were surrounded by enough EPSs to support their structure. These results suggest that the relationship between sucrose concentration and cariogenic biofilm formation in the oral cavity could be described by a functional relationship.
Highlights
Dental caries, a biofilm-related disease, is associated with the presence of cariogenic bacteria and high consumption of dietary carbohydrates [1, 2]
Around the maximum effective concentrations (MECs), the micro-colonies were bigger and more homogeneous than those at 0 and 40%, and were surrounded by enough extracellular polysaccharides (EPSs) to support their structure. These results suggest that the relationship between sucrose concentration and cariogenic biofilm formation in the oral cavity could be described by a functional relationship
The mean bacterial thickness did not change with increasing sucrose concentration (Fig 1C)
Summary
A biofilm-related disease, is associated with the presence of cariogenic bacteria and high consumption of dietary carbohydrates [1, 2]. Sucrose can cause major biochemical and physiological changes during dental biofilm formation and is considered one of the most cariogenic carbohydrates [1, 3]. Sucrose fermentation by oral bacteria can rapidly reduce the pH in dental biofilms, which results in a shift in the balance of resident plaque microflora to become more cariogenic [4]. Recent studies have demonstrated that sucrose can reduce the concentrations of calcium (Ca), inorganic phosphorus (Pi), and fluoride (F) in the dental biofilms; these are critical ions involved in the demineralization and remineralization of enamel and dentin in the oral environment [6, 7]
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