Influence of ionic strength on the tribological properties of pre-adsorbed salivary films

We have studied tribological properties of pre-adsorbed salivary films formed in vitro on compliant hydrophobic surfaces. The adsorbed salivary film significantly decreases boundary friction under physiological ionic strength, which is related to a hydrophilic character of the adsorbed film and its structure. Decrease in the ionic strength below physiological conditions affects film’s structure, but it does not significantly affect boundary lubrication at low loads. Applications of high loads led to a gradual loss of lubrication due to shear-induced wear of the films. The wear became more extensive as the ionic strength of the solvent was lowered below physiological conditions.

Research highlights
► Adsorbed salivary film is a good boundary lubricant at physiological ionic strengths.
► The reduction in friction is related to a hydrophilic character of the salivary film.
► Decrease in ionic strength below 10 mM leads to a poor lubrication at high loads.
► Deterioration of lubrication at low ionic strengths is caused by a wear of the film.
► Pre-adsorbed salivary films become more susceptible to wear at low ionic strengths.