Radiation-related root dental caries is one of the adverse effects found in patients submitted to a head and neck radiation therapy. The first objective of this work will be to verify the influence of biofilm from irradiated patient and tooth that has undergone radiation in the development of root caries as well as to test new formulations of artificial saliva with respect to the prevention of root caries under these situations in vitro (step 1). The second objective will be to define the best fluoride agent for preventing root caries comparing different products intended for professional application in vitro. For the step 1, 576 bovine root dentin samples, irradiated (70 Gy) or not, will be divided into subgroups according to: 1) the type of human biofilm used for the formation of microcosm biofilm (biofilm from irradiated and non-irradiated patient) and 2) type of artificial saliva used for the treatment of this patient (6 formulations, highlighting the experimental ones containing sugarcane cystatin and hemoglobin). For the step 2, 180 irradiated dentin samples will be treated with one of the fluoride agents (4% TiF4 varnish, 5.42% NaF varnish, placebo varnish, 30% SDF solution and no treatment) and submitted to microcosm biofilm formation. The microcosm biofilm will be formed for 5 days, using a McBain saliva with 0.2% of sucrose at 37ºC and 5% CO2. The response variables will be: bacteria viability and extracellular polysaccharide biovolume by fluorescence using a specifics kits and confocal microscope (steps 1 and 2); CFU counting for total microorganisms, total Streptococci, Streptococcus mutans and total lactobacilli (steps 1 and 2) and quantification of lactic acid production using lactate dehydrogenase kit and microplate reader (step 2). The demineralization will be quantified by transverse microradiography (steps 1 and 2). The data will be submitted to statistical analysis (p <0.05).
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