Characterisation of Structures in Salivary Secretion Film Formation. An Experimental Study with Atomic Force Microscopy

Abstract

The purpose of the present study was to characterise the structure dynamics of pure salivary secretions retained on controlled surfaces with different surface energies in the early stage of salivary film formation. Germanium prisms prepared to have either low surface energy or medium surface energy were incubated in fresh secretions of either human parotid saliva (HPS) or human submandibular/sublingual saliva (HSMSLS) for 15, 90, and 180 min. After controlled rinsing with distilled water, the surfaces were air dried and thereafter imaged with atomic force microscopy (AFM). The amount of adsorbed material and the size of the structures detected increased with increased saliva exposure time. The film thicknesses varied from 10 to 150 nm, and both HPS and HSMSLS films contained structures with diameters varying from 40 nm to 2 microm. Some of these were clustered into special formations. The HPS films exhibited a more granular morphology than the HSMSLS films. Furthermore, branched lines were detected on the low surface energy germanium prisms incubated in saliva. The results indicate that exposure time, surface energy, and type of salivary secretion all are factors affecting the adsorption characteristics of salivary films.

Optical approach to the salivary pellicle

“…Although atomic force microscopy (AFM) can reduce the required imaging time, there is always the possibility of dehydration during imaging. 22 In this study, potential modifiers of the salivary pellicle such as dehydration and mechanical damage were avoided by use of a specially designed incubating stage and imaging dish [ Figs. 1(a) The initial adsorption of discrete salivary proteins onto the enamel surface may result from electrostatic interactions through the hydrophilic regions, leaving the more hydrophobic parts of the salivary protein molecules exposed at the surface.…”

Viscous Boundary Lubrication of Hydrophobic Surfaces by Mucin

“…Mucin is one of the important constituents of saliva, and it is often assumed that it is the principle molecule contributing to oral lubrication. − Mucins are high molecular weight glycoproteins and are ubiquitous in most organisms . They play a range of key roles, from nonspecific agents of the immune system ,, to lubrication facilitators. , The latter is aided by their ability to adsorb onto surfaces of practically any chemical nature. , For example, there are two types of oral cavity surfaces: the ‘hard’ hydrophilic enamel surfaces of the teeth and the ‘soft’ hydrophobic (in the absence of a saliva coating) surfaces of gums, tongue, and palate . It is worth noting that the soft surfaces have a wide range of surface structures, roughness, and levels of keratinization, with the tongue (keratinized) having almost millimeter-sized taste buds, while gums (keratinized) and buccal (nonkeratinized) surfaces are characterized by micrometer-scale roughness…”

“…30,24 The latter is aided by their ability to adsorb onto surfaces of practically any chemical nature. 31,32 For example, there are two types of oral cavity surfaces: the 'hard' hydrophilic enamel surfaces of the teeth 33 and the 'soft' hydrophobic (in the absence of a saliva coating) surfaces of gums, tongue, and palate. 34 It is worth noting that the soft surfaces have a wide range of surface structures, roughness, and levels of keratinization, with the tongue (keratinized) having almost millimeter-sized taste buds, while gums (keratinized) and buccal (nonkeratinized) surfaces are characterized by micrometer-scale roughness.…”

Influence of two polyphenols on the structure and lubrication of salivary pellicle: An in vitro study on astringency mechanism

“…In this study, saliva was collected from one healthy donor. In order to avoid the influence of individual differences, a single donor was used to collect human whole saliva in many previous studies [14,16,40,41]. The morphology, penetration force, and friction coefficient of the original salivary pellicle in Figs.…”