Deposition and formation of a protective layer with hydroxyapatite

Dental erosion is triggered by exogenous acids. This means that acids which are brought into the oral cavity from the outside, for example from several fruits, can cause lasting damage to the teeth. Gastric acid, e.g. in individuals with an acid reflux problem or bulimia patients, also removes calcium and phosphate from the hydroxyapatite crystal matrix of the teeth. To counteract this demineralisation, a protective layer on the teeth can be helpful.

Summary of the study

Figure 1: Hydroxyapatite particles from oral care products accumulate on the tooth surface and form a protective layer.
Figure 1: Hydroxyapatite particles from oral care products accumulate on the tooth surface and form a protective layer.

In collaboration with the Max Planck Institute, research was conducted to determine whether hydroxyapatite particles can form a protective layer on the teeth. For this purpose, bovine teeth were prepared to make them comparable with each other later. The test specimens were immersed in various hydroxyapatite dispersions for 30 seconds. The proportion of hydroxyapatite of the dispersions differed as follows: 1%, 5%, 10%.

The analysis revealed that a protective layer was formed with all hydroxyapatite concentrations. Hydroxyapatite particles, as also used in Bioniq® Repair oral care products, build up on the teeth even after a short exposure period. This accumulation takes place due to dipole interactions and creates a protective layer against possible acid attacks.

The published study can be read here.

Source:  Fabritius-Vilpoux, K. et al. Quantitative Affinity Parameters of Synthetic Hydroxyapatite and Enamel Surfaces in vitro. Bioinspir Biomim Nan 8, 141-153 (2019).