Ethanol infiltration into demineralized dentin collagen fibrils via molecular dynamics simulations.

Ethanol infiltration into demineralized dentin collagen fibrils via molecular dynamics simulations.

Acta Biomater. 2016 Mar 8;

Authors: Jee SE, Zhou J, Tan J, Breschi L, Tay FR, Grégoire G, Pashley DH, Jang SS

Abstract
The purpose of this study is to investigate the interaction of neat ethanol with bound and non-bound water in completely demineralized dentin that is fully hydrated, using molecular dynamics (MD) simulation method. The key to creating resin-dentin bonds is the removal of residual free water layers and its replacement by ethanol solvent in which resin monomers are soluble, using the ethanol wet-bonding technique. The test null hypotheses were that ethanol cannot remove any collagen-bound water, and that ethanol cannot infiltrate into the spacing between collagen triple helix due to narrow interlayer spacing. Collagen fibrillar structures of overlap and gap regions were constructed by aligning the collagen triple helix of infinite length in hexagonal packing. Three layers of the water molecules were specified as the layers of 0.15-0.22 nm, 0.22-0.43 nm and 0.43-0.63 nm from collagen atoms by investigating the water distribution surrounding collagen molecules. Our simulation results show that ethanol molecules infiltrated into the intermolecular spacing in the gap region, which increased due to the lateral shrinkage of the collagen structures in contact with ethanol solution, while there was no ethanol infiltration observed in the overlap region. Infiltrated ethanol molecules in the gap region removed residual water molecules via modifying mostly the third water layer (50% decrease), which would be considered as a loosely-bound water layer. The first and second hydration layers, which would be considered as bound water layers, were not removed by the ethanol molecules, thus maintaining the helical structures of the collagen molecules.
STATEMENT OF SIGNIFICANCE: Highlight of the Research Using molecular simulation, ethanol infiltration into the demineralized dentin collagen structures is investigated. It is discovered that alignment of the collagen triple helices in the gap regions is altered by the contact with the ethanol, resulting into the infiltration of the ethanol molecules into the interlayer spacing of the collagen fibrillar structures. It is also found that non-bound water layers in the gap region are considerably mixed with the ethanol molecules, while the tightly bound water layers are not influenced by the ethanol infiltration.

PMID: 26969524 [PubMed - as supplied by publisher]

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