Influence of oral detergents and chlorhexidine on soft-layer electrokinetic parameters of the acquired enamel...

Electron microscopy has described the salivary pellicle as an 'uneven, knotted structure'. This study describes a novel soft-layer model of salivary pellicles, based on measured electrophoretic mobilities and the influence of dentifrices and a chlorhexidine mouthwash on the parameters of the model. The enamel surface was found to possess a high number of fixed, negative charges (zN = -62 mM) and to be electrophoretically hard (1/lambda = 0.6 nm), i.e. impenetrable to fluid flow. Adsorption of a salivary pellicle resulted in a fourfold reduction in the surface fixed charge density (zN = -15 mM) along with an increase in electrophoretic softness (1/lambda = 2.3 nm). Exposure of pellicles to various dentifrices containing sodium fluoride as an active component and sodium lauryl sulfate as a detergent had little effect on the surface fixed charge densities (varying between -15 and -30 mM, depending on the dentifrice involved) and electrophoretic softnesses (varying between 2.3 and 3.4 nm). Exposure of pellicles to a dentifrice containing sodium fluoride and hexametaphosphate as an additional detergent yielded soft (8.0 nm) pellicles, penetrable to fluid flow, with few fixed, negative charges (1 mM). This is opposite to the effects of chlorhexidine, which created an electrophoretically hard pellicle (1.7 nm). This soft-layer electrokinetic model quantitatively shows that the degree to which pellicles are penetrable to fluid flow differs upon exposure to dentifrices, with relevance for plaque formation, de- and remineralization and staining processes.