(46j) Molecular Simulations Study of Calcium Carbonate-Amino Acid-Dentin Interactions

Dentin hypersensitivity is a common dental health condition usually associated with exposed dentin surfaces and defined as a short, sharp pain in response to chemical or thermal stimuli. One of the resolutions for this problem is addressed by Colgate® Sensitive Pro-ReliefTM dentifrice by providing physical occlusion of exposed dentinal tubules by aggregation and adhesion of calcium carbonate abrasive particles. Amino-acids presence in toothpaste, such as arginine and lysine, are expected to help the adhesion between the dentine surface and the abrasive particles and thus provide better dentinal tubules occlusion. However, the specific mechanism of interaction of amino-acid molecules with the abrasive particles and dentin components is not clear. Moreover, quantifying and direct comparison of adhesion effect on the surfaces of dentine and calcium carbonate provided by the inclusion of different amino acids has not been done.

In this work, we investigate the interactions of amino acids and calcium carbonate (calcite), and dentin (represented by hydroxyapatite, HAP) surfaces through classical molecular dynamics simulations. To quantify the adhesion effect, we estimate the potential of mean force (free energy profiles) of the separation of the calcite and HAP plates in pure water and in a mixture of water and amino acid. Simulations showed that the free energy change is noticeably higher in the case of the presence of amino acids in the system, and differs depending on the type of amino acid. The results indicate that the higher adhesion between calcite and HAP surfaces can be achieved by the inclusion of arginine components into the toothpaste solution, thus easing the blocking of exposed dentin tubules and providing effective protection against the external irritants.