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

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... 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. Starch: Sucrose: Dental biofilm: Demineralization: Enamel * Corresponding author: Professor Jaime A. Cury, fax þ 55 19 3412 5218, email jcury@fop.unicamp.br Abbreviations: %AC, percentage of Actinomyces naeslundi in relation to total micro-organisms; CFU, colony-forming units; cH þ , hydrogen ionic concentration; CSMH, crosssectional microhardness; IP, inorganic polysaccharides; %LB, percentage of lactobacilli in relation to total micro-organisms; MSB, mitis salivarius agar plus bacitracin; pH 5 min , pH at 5 min; P i , inorganic P; %SM, percentage of mutans streptococci group in relation to total micro-organisms; DZ, mineral loss.