Salivary protein adsorption and Streptococccus gordonii adhesion to dental material surfaces

Objectives The initial adhesion of microorganisms to clinically used dental biomaterials is influenced by physico-chemical parameters like hydrophobicity and pre-adsorption of salivary proteins. Here, polymethyl methacrylate (PMMA), polyethylene (PE), polytetrafluoroethylene (PTFE), silicone (Mucopren soft), silorane-based (Filtek Silorane) and methacrylate-based (Tetric EvoCeram) dental composites, a conventional glassionomer cement as well as cobalt-chromium- molybdenum (Co28Cr6Mo) and titanium (Ti6Al4V) were tested for adsorption of salivary proteins and adhesion of Streptococcus gordonii DL1. Methods Wettability of material surfaces precoated with salivary proteins or left in phosphate-buffered saline was determined by the measurement of water contact angles. Amounts of adsorbed proteins were determined directly on material surfaces after biotinylation of amino groups and detection by horseradish peroxidase-conjugated avidin-D. The same technique was used to analyze for the binding of biotinylated bacteria to material surfaces. Results The highest amount of proteins (0.18 μg/cm²) adsorbed to hydrophobic PTFE samples, and the lowest amount (0.025 μg/cm²) was detected on silicone. The highest number of S. gordonii (3.2 × 10⁴ CFU/mm²) adhered to the hydrophilic glassionomer cement surface coated with salivary proteins, and the lowest number (4 × 10³ CFU/mm²) was found on the hydrophobic silorane-based composite. Hydrophobicity of pure material surfaces and the number of attached microorganisms were weakly negatively correlated. No such correlation between hydrophobicity and the number of bacteria was detected when surfaces were coated with salivary proteins. Significance Functional groups added by the adsorption of specific salivary proteins to material surfaces are more relevant for initial bacterial adhesion than hydrophobicity as a physical property.