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Dose-response effect of epigallocatechin-3-gallate (EGCG) on the bacterial adhesion and initial growth of Streptococcus mutans biofilm and on the progression of biofilm-induced caries lesion formed on bovine dental enamel

Grant number: 20/02658-7
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): July 01, 2020
Effective date (End): January 31, 2023
Field of knowledge:Health Sciences - Dentistry - Social and Preventive Dentistry
Principal researcher:Silmara Aparecida Milori Corona
Grantee:Maria Gerusa Brito Aragão
Home Institution: Faculdade de Odontologia de Ribeirão Preto (FORP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

The aim of this investigation is to evaluate the dose-response effect of epigallo-catechin-3- gallate (EGCg) on the bacterial adhesion, initial biofilm growth, and on the progression of biofilminduced caries lesions formed on bovine dental enamel. The Minimum Inhibitory Concentration (MIC) of EGCG on S. mutans will be tested. Concentrations 10x (EGCg C1), 100x (EGCGg C2), and 1000x (EGCg C3) higher than the MIC will be used against the biofilms, as they are more resistant to antimicrobials. Three experimental regimens will be adopted. I) bovine enamel blocks (n=12/group) of known Surface Hardness (SH) will be immersed into saliva to promote the formation the acquired pellicle. Then, such enamel specimens will be exposed to one-minute treatments with NaCl 50 mM (negative control), EGCg 1, EGCGg C2, EGCg C3, or chlorhexidine 0.12% (positive control). After the treatments, the blocks will be transferred to 24-weel plates containing a S. mutans inoculum and will remain there for 8h topromote the adhesion of the bacteria to the salivary pellicle. At the end of this period, the enamel blocks will be analyzed regarding the percentage of surface hardness loss (%SHL), the culture medium pH will be evaluated and the biofilm will be collected to the counting of Colony Forming Unities (CFU); II) bovineenamel blocks (n=12/group) of known SH will be immersed into saliva to promote the formation the acquired pellicle. After that, the enamel blocks will be transferred to 24-weel plates containing a S. mutans inoculum and will remain there for 8h to promote the adhesion of the bacteria to the salivary pellicle. Then, such enamel specimens will be exposed to one-minute treatments with NaCl 50 mM (negative control), EGCg C1, EGCGg C2, EGCg C3, or chlorhexidine 0.12% (positive control). Then, the enamel blocks will be transferred to a fresh medium where they will remain for 16 h to promote theinitial biofilm growth. At the end of this period, the enamel blocks will be analyzed regarding the %SHL the culture medium pH will be evaluated and the biofilm will be collected to the counting of CFU; III) bovine enamel blocks(n=12/group) of known surface hardness will be submitted to caries lesion formation through the use of a microbiological model. Thus, the biofilms formed on the saliva-coatedenamel and exposed to 1% sucrose will be cultivated for 5 days. The culture medium will be changed daily and the treatments with NaCl 50 mM (negative control), EGCg C1, EGCGg C2, EGCg C3, or chlorhexidine 0.12% (positive control) will be performed before each medium change. At the end of the th day, the enamel blocks will be collected to evaluate the caries progression by calculating the area ofintegrated microhardness loss, analyzing the calcium and phosphorous dosages by electronic spectroscopy of chemical analysis, and observing the structural enamel changes by scanning electron microscopy. The biofilm will be collected to analyses of CFU, dry weight and polysaccharides. The dose-response effectof EGCg on CFU counting, culture medium pH, and %SHL (experimental regimens I and II), integrated hardness loss, and values of calcium and phosphorous measured by EDS (experimental regimen III), CFU counts, dry weight and polyssacharides will be evaluated by linear regression. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
BRITO ARAGAO, MARIA GERUSA; FERNANDES GOMES, FRANCISCO ISAAC; MAIA PAIXAO-DE-MELO, LETICIA PINHO; MILORI CORONA, SILMARA APARECIDA. Brazilian dental students and COVID-19: A survey on knowledge and perceptions. EUROPEAN JOURNAL OF DENTAL EDUCATION, FEB 2021. Web of Science Citations: 0.

Please report errors in scientific publications list by writing to: cdi@fapesp.br.