Salivary film formation on defined solid surfaces in the absence and presence of microorganisms

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Abstract
A salivary derived proteinaceous film will condition any surface exposed in the oral cavity prior to cell attachment. Studies have shown a strong correlation between the initial surface properties of a material and its cell retaining capacity, indicating that a mechanism may exist by which surface characteristics of a solid are transmitted through the adsorbed film. The aim of this study was to monitor the film organization of salivary secretions at defined liquid‐solid interfaces, and to evaluate the effect of the critical surface tension and the presence of microorganisms on the packing of the films. Fresh secretions from human parotid (HPS) and submandibular‐sublingual glands (HSMSL) were allowed to form thin films on surfaces of low and medium critical surface tensions under controlled flow conditions, in the presence and absence of microorganisms. Two strains of Streptococcus salivarius and Streptococcus sanguis were used as test microorganisms. The resulting films were monitored in situ by nondestructive surface analytical techniques, to avoid interference of either composition or organization of the adsorbed films. ATR infrared spectroscopy and ellipsometry were used to obtain information on the amount of protein and the thickness of the films. Both HPS and HSMSL formed films of approximately 200 Å thickness on surfaces of medium critical surface tension, but on the low energy surfaces HPS films were significantly thinner. More protein mass was detected in films on medium energy surfaces than on low energy surfaces. The presence of microorganisms during film deposition did not have a statistically significant effect on any of the parameters measured. These data indicate that the amount of salivary protein retained by a material is more directly related to critical surface qualities of the solid than to microorganisms in suspension, while the film's initial organization (e.g. packing, density) of salivary derived pellicles is also dependent on the specific protein‐surface combination.