Effect on the application of arginine on the composition and metabolism of saliva microcosm biofilms and prevention of enamel demineralization

• Grant number: 18/01654-8
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): March 01, 2019
• Effective date (End): May 31, 2021
• Field of knowledge: Health Sciences - Dentistry - Pediatric Dentistry
• Principal researcher: Thiago Cruvinel da Silva
• Grantee: Daniela Alejandra Cusicanqui Méndez
• Home Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil

Abstract

Clinical outcomes have demonstrated that arginine-containing dentifrices can be effective in reversing and protecting mineral dental tissues against demineralization, reducing the incidence of dental caries in children. The evidence level of these findings, however, is still considered low. Additionally, studies regarding the effect of arginine on dental biofilms and on demineralization-remineralization process are scarce. Therefore, the aim of this in vitro study will be determine the effect of two different concentrations of arginine (2,5 and 8%), combined or not with 1,450 ppm sodium fluoride, on the composition and metabolism of salivary microcosm biofilms, as well as on the prevention of the demineralization of dental enamel. Saliva samples collected from 3 caries-free adults will be employed to produce a microbiological pool that will be used as a stock solution to start the biofilm growth on bovine enamel blocks. This study will be divided in two phases, according to distinct time of application of treatments: I) during 72 h of biofilm growth, and II) after 72 h of biofilm growth. In each experimental phase, the biofilms will be treated according to one of 6 experimental groups, as follows: 1) deionized water (DW, negative control); 2) 1,100 ppm sodium fluoride (NaF, positive control); 3) 2,5% arginine (ARG2,5%); 4) 8% arginine (ARG8%); 5) NaF + 2,5% arginine (NaFARG2,5%); and 6) NaF + 8% arginine (NaFARG8%). The composition and viability of biofilms will be assessed by 3 distinct techniques: a) counts of colony-forming units of total microorganisms, total streptococci, mutans streptococci, and lactobacilli, grown onto Tryptic Soy Blood Agar, Mitis Salivarius Agar, Mitis Salivarius Sucrose Bacitracin Agar, and Rogosa Agar with 0.13% glacial acetic acid, respectively; b) Human Oral Microbiome Identification using Next Generation Sequencing (HOMINGS); and c) vitality of microbial cells in different depths of intact biofilms by confocal laser scanning microscopy. The metabolism of biofilms will be determined by the quantification of amounts of insoluble extracellular polysaccharides (colorimetric method) and concentration of L-lactate in culture media (enzymatic spectrophotometric method). The prevention of demineralization will be evaluated by the measurement of pH of culture media, quantification of calcium in culture medium by atomic absorption, and surface microhardness loss, integrated mineral loss and lesion depth by the mineral analyses of the structure of enamel blocks by microhardness tests and transverse microradiography. The statistical analysis will be conducted according to the normality and homogeneity of data. P values < 0.05 will be considered significant. (AU)