Analysis of the dose-response effect of epigallocatechin-3-gallate (EGCG) on bacterial adhesion and initial growth of Streptococcus mutans biofilm on dental enamel

• Grant number: 19/10290-2
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2019
• End date: September 30, 2020
• Field of knowledge: Health Sciences - Dentistry - Social and Preventive Dentistry
• Principal Investigator: Silmara Aparecida Milori Corona
• Grantee: Gustavo Teodoro Costa Lizarelli
• Host Institution: Faculdade de Odontologia de Ribeirão Preto (FORP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

This study aims to analyze the dose-response effect of the Epigalocathechin-3-galate on the bacterial adhesion and initial formation of a S. mutans biofilm. Thus, an in vitro and blinded experimental study will be performed using a cariogenic S. mutans biofilm model. Two experimental regimens will be tested: I) Bovine enamel blocks (4x7x1 mm) with pre-evaluated surface microhardness (SH) will be immersed into human saliva for the formation of the salivary pellicle. Then the enamel blocks will be exposed to 1 min treatments with 50 mM NaCl (negative control), 1 mg/ml EGCg, 2 mg/ml EGCGg, 5 mg/ml EGCg or 0.12% chlorhexidine (positive control). Then the enamel blocks will be transferred to a 24-wheel plate containing a S. mutans UA159 inoculum, where they will remain for 8 h to promote adhesion of the biofilm to the salivary pellicle. At the end of this period, the culture medium pH will be evaluated, the adhered biofilm will be collected to analyze the number of colony forming unities (CFU), and the enamel blocks will also be collected to evaluate the percentage of surface hardness loss (%SHL). II) Bovine enamel blocks (4x7x1 mm) with pre-evaluated surface microhardness (SH) will be immersed into human saliva for the formation of the salivary pellicle. Then the enamel blocks will be transferred to a 24-wheel plate containing a S. mutans UA159, where they will stay for 8 h to promote adhesion of the biofilm to the salivary pellicle. At the end of this period, the pH of the culture medium will be checked, and the enamel blocks containing the adhered biofilm will be washed in 50 mM NaCl. Then, the biofilm will be exposed to 1 min treatments with 50 mM NaCl (negative control), 1 mg/ml EGCg, 2 mg/ml EGCGg, 5 mg/ml EGCg or 0.12% chlorhexidine (positive control). After the treatment, the enamel blocks will be transferred to a fresh culture medium, where they will stay for 16 hours. At the end of this period, the culture medium pH will be evaluated, the adhered biofilm will be collected to analyze the number of CFU, and the enamel blocks will also be collected to evaluate the %SHL. Linear regression will be used to evaluate the dose-response effect of EGCg on the CFU counts, pH, and %SHL.