Enamel Carious Lesion Development in Response to Sucrose and Fluoride Concentrations and to Time of Biofilm Formation: An Artificial-Mouth Study

The aim of this study was to evaluate both sucrose and fluoride concentrations and time of biofilm formation on enamel carious lesions induced by an in vitro artificial-mouth caries model. For Study 1, biofilms formed by streptococci and lactobacilli were grown on the surface of human enamel slabs and exposed to artificial saliva containing 0.50 or 0.75？ppmF (22.5？h/d) and broth containing 3 or 5% sucrose (30？min; 3x/d) over 5？d. In Study 2, biofilms were grown in the presence of 0.75？ppmF and 3% sucrose over 3 and 9 days. Counts of viable cells on biofilms, lesion depth (LD), and the integrated mineral loss (IML) on enamel specimens were assessed at the end of the tested conditions. Counts of total viable cells and L. casei were affected by sucrose and fluoride concentrations as well as by time of biofilm formation. Enamel carious lesions were shallower and IML was lower in the presence of 0.75？ppmF than in the presence of 0.50？ppmF . No significant effect of sucrose concentrations was found with respect to LD and IML . Additionally, deeper lesions and higher IML were found after 9 d of biofilm formation . Distinct sucrose concentrations did not affect enamel carious lesion development. The severity of enamel demineralization was reduced by the presence of the higher fluoride concentration. Additionally, an increase in the time of biofilm formation produced greater demineralization. Our results also suggest that the present model is suitable for studying aspects related to caries lesion development. 1. Introduction Supragingival dental biofilm is a multispecies community of microorganisms embedded in a matrix attached to dental surfaces. Its accumulation on teeth is a necessary factor for occurrence of dental caries, which is considered to be a disease resulting from the sum of complex interactions among tooth structure, supragingival biofilm, diet, time, and other oral and personal factors [1]. This disease is related to frequent ingestion of rapidly fermentable carbohydrates that are converted to acid-end products by bacterial metabolism. The acidic pH produced due to fermentation of dietary carbohydrates induces ecological changes in dental biofilm. Acid-tolerant bacteria that are normal constituents of the oral microbiota, but present at low levels, have increased proportions in response to acidic environmental conditions [2]. These bacteria continue to produce acids, extending the time in which the biofilm remains at low pH levels. Additionally, the low pH produced as the result of this process disrupts the mineral equilibrium between enamel and