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

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.