Surface free energies of oral streptococci and their adhesion to solids

Abstract

The adhesion of 3 strains of oral streptococci from a buffered suspension onto 3 different solid substrata was studied. Representative strains of streptococci were selected on the basis of their surface free energy (γb), namely Streptococcus mitis L1 (γb = 37 mJ·m−2), Streptococcus sanguis CH3 (95 mJ·m−2) and Streptococcus mutans NS (117 mJ·m−2). Solid substrata were also selected on basis of their surface free energy (γs), and included polytetrafluorethylene (γs = 20 mJ·m−2), polymethylmethacrylate (53 mJ·m−2) and glass (109 mJ·m−2). Bacterial adhesion was measured as the number of bacteria adhering per cm2 at equilibrium. Equilibrium was usually obtained within 20 min. S. sanguis CH3, having an intermediate surface free energy did not show a clear preference for any of the 3 solids. S. mitis L1, however, the lowest surface free energy strain, adhered in highest numbers to the low energy solid PTFE, whereas the highest γb strain, S. mutans NS, adhered in highest numbers to the highest γs solid, glass. Calculation of the interfacial free energy of adhesion (ΔFadh) for each bacterial strain showed that this parameter was predictive of bacterial adhesion to solid substrata.