In vitro salivary pellicles were found to be less hydrophobic by water contact angles than clinically formed pellicles. In this study, water contact angles were measured on enamel coated with pellicles adsorbed from reconstituted human whole saliva (RHWS) and after exposure to dentifrices or dietary components. In addition, adhesion of Streptococcus oralis J22 to pellicles formed from RHWS with minor amounts of milk added and after exposure to dentifrices was studied. Exposure of RHWS-pellicles to milk or salad oil yielded an increase in the hydrophobicity of in vitro pellicles to values observed in vivo, but a decrease was seen after exposure to a sugar solution. Pellicles formed from saliva with 0.4% milk added attracted less S. oralis cells than pellicles formed in the absence of milk components. Exposure of pellicles formed from saliva with milk added to various dentifrices had a variable effect on bacterial adhesion: markedly lower numbers of adhering S. oralis were found for a dentifrice with NaF, but exposure to dentifrices containing SnF2 or hexametaphosphate showed slightly increased adhesion. In summary, dietary components have influence on the hydrophobicity of enamel pellicles, while combinations of dietary components and dentifrices certainly influence the adhesiveness of the pellicles. The effects of dietary components on pellicle conditioning film should be taken into consideration in research on the development of ingredients to control intraoral surface chemistry and microbiology, as well as in the development of oral products.

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/λ = 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/λ = 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.