Acquired Enamel Pellicle Modification with Casein and Mucin in Different Concentrations and its Impact on Initial Dental Erosion

Abstract

Casein and mucin have been shown to improve the erosion-protective properties of the pellicle when applied in combination. The aim of this in vitro study was to optimize the concentrations of these 2 proteins to achieve a maximum protective effect. For the 2 parts of this study, we prepared a total of 195 human enamel specimens and randomly assigned them to 13 groups, corresponding to 11 different casein-mucin concentration-combinations tested and 2 negative control groups (humid chamber). They underwent 5 cycles, consisting of pellicle formation from human whole saliva (2 h, 30°C), modification of the pellicle with casein and mucin in different concentrations (immersion in protein solutions for 2 h, 30°C), and erosion for 1 min in citric acid (0.65%, pH 3.5, 30°C). Surface microhardness (SMH), surface reflection intensity (SRI), and in the first part also calcium release were monitored during the cycling process, and analyzed with Kruskal-Wallis and post hoc Dunn’s tests. The results suggest that the best concentrations to achieve the highest erosion-protective effect are 3.0% casein and 0.81% mucin, which lead to a significant protection as measured by SMH as well as SRI compared to the unmodified pellicle. For the calcium release, no significant differences were found. This concentration combination corresponds to a general raise of the protein concentrations and a change in the molar ratio of the proteins as compared to earlier studies. Casein and mucin could now be incorporated at the determined concentration as natural ingredients in oral care products designed to protect against erosion.

Pellicle Modification with Casein and Mucin Does Not Affect Surface Loss from Erosion and Abrasion

“…An explanation could be that the casein and mucin where mostly removed by the erosion. This would explain the erosion protective properties shown in earlier studies [Cheaib and Lussi, 2011;Sieber et al, 2019], without changing the lubricating properties in the subsequent brushing cycles. Surprisingly, not even the substance loss of the Ctrl group (without AEP) was different, suggesting that the presence or absence of the AEP did not influence the amount of enamel removed during toothbrushing.…”

“…Furthermore, some studies with casein or products containing digested caseins in the form of casein phosphopeptide have shown promising results in erosion protection [Ranjitkar et al, 2009;White et al, 2011;Carvalho et al, 2013;Poggio et al, 2014]. These products might support the action of casein and mucin and possibly attract more mucin to the surface [Sieber et al, 2019].…”

“…The protein concentrations of 1% casein and 0.27% mucin were chosen based on an earlier study which identified these concentrations as best for erosion protection [Sieber et al, 2019]. The solution for the pellicle modification was prepared as follows: casein from bovine milk (Sigma-Aldrich, C7078) was dissolved at the desired concentration of 1% in deionized water at 40 ° C, pH 11.5.…”

“…Proteins, like CaneCPI-5 or casein, can also improve the AEP's protective properties [Barbour et al, 2008;Santiago et al, 2017]. Combining casein with the mucus-forming protein mucin even increases the protection-improving effect [Cheaib and Lussi, 2011;Sieber et al, 2019].…”

“…Among them is lubrication, in which mucins play a key role. While mucin alone does not bind well to dental surfaces, casein can improve its binding to dental surfaces [Sieber et al, 2019]. Treating the AEP with a combination of mucin and casein is known to improve its erosion-inhibiting properties and decrease the adherence of bacteria [Cheaib et al, 2015], but it is not known whether it also influences its lubricating properties.…”