title: Anisotropic demineralization and oriented assembly of hydroxyapatite crystals in enamel: smart structures of biominerals.
abstract: It is interesting to note that the demineralization of natural enamel does not happen as readily as that of the synthesized hydroxyapatite (HAP), although they share a similar chemical composition. We suggest that the hierarchical structure of enamel is an important factor in the preservation of the natural material against dissolution. The anisotropic demineralization of HAP is revealed experimentally, and this phenomenon is understood by the different interfacial structures of HAP-water at the atomic level. It is found that HAP {001} facets can be more resistant against dissolution than {100} under acidic conditions. Although {100} is the largest surface of the typical HAP crystal, it is {001}, the smallest habit face, that is chosen by the living organisms to build the outer surface of enamel by an oriented assembly of the rodlike crystals. We reveal that such a biological construction can confer on enamel protections against erosion, since {001} is relatively dissolution-insensitive. Thus, the spontaneous dissolution of enamel surface can be retarded in biological milieu by such a smart construction. The current study demonstrates the importance of hierarchical structures in the functional biomaterials.
authors.forename: Haihua
authors.initials: H
authors.lastname: Pan
authors.forename: Jinhui
authors.initials: J
authors.lastname: Tao
authors.forename: Xinwei
authors.initials: X
authors.lastname: Yu
authors.forename: Lei
authors.initials: L
authors.lastname: Fu
authors.forename: Jiali
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiangxuan
authors.initials: X
authors.lastname: Zeng
authors.forename: Guohua
authors.initials: G
authors.lastname: Xu
authors.forename: Ruikang
authors.initials: R
authors.lastname: Tang
mesh_terms: D000293:Adolescent; D000328:Adult; D016880:Anisotropy; D001641:Bicuspid / Q000737:chemistry; D003198:Computer Simulation; D003460:Crystallization; D003461:Crystallography; D003743:Dental Enamel / Q000737:chemistry*; D017886:Durapatite / Q000138:chemical synthesis / Q000737:chemistry*; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D011522:Protons; D013499:Surface Properties; D017001:Tooth Demineralization; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D014867:Water; D017886:Durapatite; D006851:Hydrochloric Acid