title: Investigation of ethanol infiltration into demineralized dentin collagen fibrils using molecular dynamics simulations.
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 ideal 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 0.15-0.22nm, 0.22-0.43nm and 0.43-0.63nm 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 tightly bound water layers, were not removed by the ethanol molecules, thus maintaining the helical structures of the collagen molecules.
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Sang Eun
authors.initials: SE
authors.lastname: Jee
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Jienfeng
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing, PR China.
authors.forename: Jianquo
authors.initials: J
authors.lastname: Tan
authors.affiliation: Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Bologna, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Breschi
authors.affiliation: Department of Endodontics, College of Dental Medicine, Georgia Regents University, Augusta, GA, USA.
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.affiliation: Faculty of Odontology, Department of Biomaterials, University of Toulouse, Toulouse, France.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Grégoire
authors.affiliation: Department of Oral Biology, College of Dental Medicine, Georgia Regents University, Augusta, GA, USA. Electronic address: dpashley@gru.edu.
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.affiliation: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, USA; Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA. Electronic address: seungsoon.jang@mse.gatech.edu.
authors.forename: Seung Soon
authors.initials: SS
authors.lastname: Jang
mesh_terms: D003094:Collagen / Q000737:chemistry*; D003804:Dentin / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry*; D006801:Humans; D056004:Molecular Dynamics Simulation
chemical_list: D000431:Ethanol; D003094:Collagen
keywords: Bound water; Collagen; Dentin matrix; Ethanol; Gap regions; Molecular dynamics simulation