Despite therapeutic progress, opportunistic oral fungal infectious diseases have increased in prevalence, especially in denture wearers. The combination of entrapment of yeast cells in irregularities in denture-base and denture-relining materials, poor oral hygiene and several systemic factors is the most probable cause for the onset of this infectious disease. Hence colonization and growth on prostheses by Candida species are of clinical importance. The purpose of this review is to critically discuss several key factors controlling the adhesion of Candida species which are relevant to denture-associated stomatitis. Although there is some consensus on the role of surface properties, studies on several other factors, as the use of denture liners, salivary properties and yeast-bacterial interactions, have shown contradictory findings. A comprehensive fundamental understanding is hampered by conflicting findings due to the large variations in experimental protocols, while other factors have never been thoroughly studied. Surface free energy and surface roughness control the initial adherence, but temporal changes have not been reported. Neither have in vivo studies shown if the substratum type is critical in dictating biofilm accumulation during longer periods in the oral environment. The contribution of saliva is unclear due to factors like variations in its collection and handling. Initial findings have disclosed that also bacteria are crucial for the successful establishment of Candida in biofilms, but the clinical significance of this observation is yet to be confirmed. In conclusion, there is a need to standardize experimental procedures, to bridge the gap between laboratory and in vivo methodologies and findings and – in general – to thoroughly investigate the factors that modulate the initial attachment and subsequent colonization of denture-base materials and the oral mucosa of patients subjected to Candida infections. Information on how these factors can be controlled is required and this may help to prevent the disease. The societal impact of such information is significant given the magnitude of the candidosis problem worldwide.

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Since in vitro and animal studies suggest that the combination of starch with sucrose may be more cariogenic than sucrose alone, the study assessed in situ the effects of this association applied in vitro on the acidogenicity, biochemical and microbiological composition of dental biofilm, as well as on enamel demineralization. During two phases of 14 d each, fifteen volunteers wore palatal appliances containing blocks of human deciduous enamel, which were extra-orally submitted to four groups of treatments: water (negative control, T1); 2 % starch (T2); 10 % sucrose (T3); and 2 % starch þ 10 % sucrose (T4). The solutions were dripped onto the blocks eight times per day. The biofilm formed on the blocks was analysed with regard to amylase activity, acidogenicity, and biochemical and microbiological composition. Demineralization was determined on enamel by cross-sectional microhardness. The greatest mineral loss was observed for the association starch þ sucrose (P,0·05). Also, this association resulted in the highest lactobacillus count in the biofilm formed (P,0·05). In conclusion, the findings suggest that a small amount of added starch increases the cariogenic potential of sucrose. Among dietary carbohydrates, starch has been pointed out as noncariogenic or slightly cariogenic when used as the sole source of carbohydrate in the diet. This observation has been supported by experiments on dental biofilm acidogenicity (Stephan, 1940;Imfeld, 1977;Lingström et al. 1989), experimental studies with animals (König & Grenby, 1965;Green & Hartles, 1967;Hefti & Schmid, 1979;Bowen et al. 1980), controlled studies in man (Gustaffson et al. 1954), epidemiological data (Marthaler & Froesch, 1967;Fisher, 1968;Newbrun et al. 1980) and in situ experiments (Lingström et al. 1994), which demonstrated that starch is less cariogenic than sucrose.However, while in primitive diets starch was consumed as the main energy source, in contemporary ones it is consumed simultaneously or interspersed with sucrose (Lingström et al. 2000). This combination, which is consumed by both adults and children, may influence dental biofilm composition and consequently dental caries. Thus, a greater prevalence of caries lesions was found in children who consume milk supplemented with a combination of cereal and sucrose (Mattos-Graner et al. 1998). Such observation in human subjects is supported by the results of experimental caries studies in animals (Firestone et al. 1982;Mundorff-Shrestha et al. 1994), suggesting that starch would enhance the cariogenic potential of sucrose.The explanation for the greater cariogenicity of the association of dietary starch with sucrose may reside in the dental biofilm formed. It is well known that the biofilm formed in the presence of sucrose is more cariogenic due to its high concentration of extracellular insoluble polysaccharides (IP), which alter the matrix of the biofilm, making it more porous (Dibdin & Shellis, 1988). These polysaccharides are produced from sucrose by bacterial enzymes named glucosyltransferases....

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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.