Impact of oral astringent stimuli on surface charge and morphology of the protein-rich pellicle at the tooth-saliva interphase
The proteinaceous pellicle that develops on the surface of teeth upon contact with saliva is important for the formation of oral biofilms and for the protection of teeth from abrasion and chemically induced erosion. Astringent food ingredients comprising polyphenols, cationic macromolecules, and multivalent metal salts are known to interact with the pellicle. Applying the quartz crystal microbalance with dissipation monitoring (QCM-D), streaming current measurements, transmission electron microscopy, and atomic force microscopy [1], we provide comprehensive insights into interfacial charging, ultrastructure, thickness, and surface roughness of the pellicles formed on the model substrates silicon oxide (SiO2), Teflon® AF, and hydroxyapatite, as well as on bovine enamel before and after incubation with the astringents epigallocatechin gallate, tannic acid, iron(III) salt, lysozyme, and chitosan. The multifaceted alterations of the salivary pellicle observed by the different methods may come along with an increase in roughness perceived on the teeth, which is part of the complex sensations of oral astringency.
(A) Schematic representation of pellicle on enamel and model surfaces. (B) Thickness (d), storage modulus (G’), loss modulus (G’’), and viscosity (η) of in vitro pellicles on SiO2,Teflon® AF, and hydroxyapatite (HA) as determined by QCM-D. The type of electrolyte (artificial saliva electrolyte (ASE) or 1 mM KCl) used for rinsing the pellicle after the adsorption step is indicated for each substrate type. (C) Streaming current vs. pressure gradient (Istr/ΔP) at varied pH of 1 mM KCl solution for reference surfaces (bare SiO2 and Teflon® AF), in situ as well as in vitro pellicles on SiO2 surfaces and in vitro pellicles on Teflon® AF. Adapted from Ref. [1]., Copyright 2019, with permission from Elsevier. .
References
[1] Zimmermann et al. Impact of oral astringent stimuli on surface charge and morphology of the protein-rich pellicle at the tooth-saliva interphase. Colloids and Surfaces B: Biointerfaces 2019, 174, 451, doi: https://doi.org/10.1016/j.colsurfb.2018.11.028.