In this in vitro study, the restoration of acid-eroded enamel surface morphology and anti-wear properties under two conditions, mono-remineralization (treated with remineralization alone) and impact-remineralization (treated with cyclic impact followed by remineralization), are characterized to determine the effect of occlusal loading on enamel remineralization. Compared with the mono-remineralized surface, the impact-remineralized surface demonstrates better anti-wear performance, as manifested by a higher hardness and elastic modulus, as well as a lower friction coefficient and wear volume. Loading on the eroded enamel surface induces the fragmentation of hydroxyapatite nanoparticles, which aids crystal deposition and fusion during subsequent remineralization. In summary, owing to the enamel microstructure, occlusal loading can promote the restoration of enamel anti-wear properties by enhancing remineralization. Remineralization enhancement through occlusal-loading-induced nanoparticle fragmentation plays a significant role in preventing human teeth from excessive wear.

This study investigated the influence of two polyphenols on the structure and lubrication of the salivary pellicle, aiming to extend the understanding of astringency mechanisms. The salivary pellicle was prepared by the adsorption of human whole saliva on the enamel substrate. Low-astringency catechin and high-astringency tannic acid were used as astringents. The changes induced by the two polyphenols in the structure and lubrication of the salivary pellicle were examined using quartz crystal microbalance with dissipation (QCM-D) and nano- indentation/scratch technique. The salivary pellicle suffers from changes in structure and physical properties owing to protein dehydration and protein-polyphenol complexation when encountering polyphenolic molecules, causing increases in the roughness and contact angle but a decrease in the load-bearing capacity. Therefore, the lubrication performance of the salivary pellicle is impaired, leading to an increase and fluctuation of the friction coefficient. The intensity of astringency has a strong positive correlation with the water contact angle, surface roughness, and friction coefficient of the salivary pellicle. In summary, astringency is a tactile perception driven by the roughness and wettability of the salivary pellicle rather than oral lubrication, and increased intraoral friction is an inevitable consequence of astringency. The findings of this study will help promote and assist the objective evaluation of astringency.

In this study, the protective effects of two food hydrocolloids, Xanthan gum and Arabic gum, on dental erosion are investigated from the perspective of the nanomechanical properties and microtribological behavior of acid-eroded enamel. Enamel specimens prepared from extracted human teeth were immersed in citric acid solution (CAS), CAS with 0.03% w/v Xanthan gum and CAS with 0.03% w/v Arabic gum, respectively, for 10 min to obtain three groups of eroded specimens. The nanomechanical properties and microtribological behavior of enamel were examined using nano-indentation/scratch techniques. The results show that compared with Arabic gum, Xanthan gum inhibits enamel surface demineralization and acid permeation more effectively because of a more uniform and denser adsorption on the surface of the enamel. The impairment of the nanomechanical and microtribological properties of the enamel surface by acid erosion is mitigated more significantly by adding trace amounts of Xanthan gum than Arabic gum. In summary, adding trace food hydrocolloids reduces enamel surface demineralization and inhibits acid permeation to mitigate the influence of erosion on the mechanical and tribological properties of enamel. The adsorption state of food hydrocolloids is the determining factor in the permeability of acid agents into the enamel and plays a significant role in preventing dental erosion.