Oral bacteria adhered to dental material surfaces are known to cause various oral diseases. This study aimed to develop a high- sensitive and non-radioisotopic fluorescence dye method for quantification of oral bacteria (Streptococcus, Actinomyces and Veillonella) adhered to denture material surfaces. The amount of adhered bacteria was estimated from the fluorescence intensity derived from resazurin, which is reduced by bacterial metabolic reactions. The addition of bacterial metabolic substrates (glucose for Streptococcus and Actinomyces and sodium lactate for Veillonella) to the reaction mixture increased the fluorescence intensity by 2.3-110 times, subsequently improved the sensitivity. Furthermore, an experimental device having silicon wells containing test material was carefully designed for accurate quantification of bacteria adhered to test materials. The improved resazurin method using a new experimental device successfully enabled the quantification of bacterial adhesion to polymethyl methacrylate and other three conventional denture materials.
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