The presence of acquired enamel pellicle (AEP) is one of the protective factors against erosion and tooth decay. The alteration of the PAE protein profile, through the incorporation of certain proteins, can increase the protection against acid attacks and alter the initial bacterial colonization of the biofilm, modifying its structure. Statherin is an important salivary protein, which, due to its high affinity for hydroxyapatite, once incorporated in PAE can protect against intrinsic erosion. However, little is known about its protective effect against acids of bacterial origin. Thus, the objective of the present study will be to evaluate the effect of the peptide derived from staterin (Stn15pSpS) on the viability of the microcosm biofilm and enamel demineralization, aiming, ultimately, to prevent tooth decay. Samples (4 mm x 4 mm) of bovine enamel (n = 72) will be prepared and treated for 60 s (1 mL per sample) with the solutions containing the peptide, PBS (negative control) 0.12% chlorhexidine or 500 ppm NaF (positive controls), so that there is protein binding to the enamel surface. For the formation of the microcosm biofilm, saliva will be collected from 10 healthy individuals who have not brushed their teeth in the past 24 hours and who have not drunk liquids or ingested food in the past 2 hours. The saliva will be diluted (70% saliva and 30% glycerol), and later mixed with McBain's artificial saliva (1:50). 24-well plates containing the enamel samples will be filled with 1 mL of inoculum and incubated in an anaerobic jar at 37 ° C for 8 h. The other exchanges will involve McBain's saliva supplemented with 0.2% sucrose. Every 24 h, the medium will be changed until 3 days of cultivation are completed. From the second day, before changing the medium, the biofilm will be treated with Stn15pSpS in different concentrations (1.88 X 10-5 M, 3.76 X 10-5 M or 7.52 X 10-5 M) for 60 s. The negative control will be treated with PBS and the positives with 0.12% chlorhexidine or 500ppm NaF. The biofilm metabolic activity will be analyzed by the resazurin method and then the samples will be analyzed by transversal micro-radiography (TMR) to measure demineralization. caused by the biofilm in the studied conditions.The data will be checked for normality and homogeneity, using the appropriate statistical test (parametric or not, p <0.05).
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