Nanomechanics and morphology of salivary pellicle

Acquired salivary pellicle is a thin protein-rich film formed by the adsorption of saliva onto teeth. It plays important roles in lubrication during mastication and protecting the teeth from chemical attack. Pellicle can become colonized by bacteria to form dental plaque which can lead to dental caries if the bacteria are acidogenic. Abrasive polishing with a dentrifice is used periodically to remove the pellicle from teeth. Pellicle can interact with dietary polyphenolic compounds (tannins) to create extrinsic stains on the tooth surface. The staining can modify the pellicle's mechanical properties and change its morphology resulting in a “squeaky” feeling when the tongue is rubbed over the teeth. Atomic force microscopy imaging and nanoscale mechanical measurements show that unstained pellicle has a dense undulating morphology and is a surprisingly stiff, viscoelastic solid. In contrast, tannin-stained pellicle has fewer but larger surface undulations and exhibits substantial viscous creep.