journal article·2022-07-26Open access

Role of the Mineral in the Self-Healing of Cracks in Human Enamel

Andrew J. Lew, Elia Beniash, Pupa U. P. A. Gilbert, Markus J. Buehler

ACS Nano· Volume 16· Issue 7

Abstract

Human enamel is an incredibly resilient biological material, withstanding repeated daily stresses for decades. The mechanisms behind this resilience remain an open question, with recent studies demonstrating a crack-deflection mechanism contributing to enamel toughness and other studies detailing the roles of the organic matrix and remineralization. Here, we focus on the mineral and hypothesize that self-healing of cracks in enamel nanocrystals may be an additional mechanism acting to prevent catastrophic failure. To test this hypothesis, we used a molecular dynamics (MD) approach to compare the fracture behavior of hydroxyapatite (HAP) and calcite, the main minerals in human enamel and sea urchin teeth, respectively. We find that cracks heal under pressures typical of mastication by fusion of crystals in HAP but not in calcite, which is consistent with the resilience of HAP enamel that calcite teeth lack. Scanning transmission electron microscopy (STEM) images of structurally intact (“sound”) human enamel show dashed-line nanocracks that resemble and therefore might be the cracks healed by fusion of crystals produced in silico. The fast, self-healing mechanism shown here is common in soft materials and ceramics but has not been observed in single crystalline materials at room temperature. The crack self-healing in sound enamel nanocrystals, therefore, is unique in the human body and unique in materials science, with potential applications in designing bioinspired materials.
Source: openalex_inverted_index · Quality: baseline

Research context

OpenAlex topics: Dental materials and restorations · Dental Erosion and Treatment · Bone and Dental Protein Studies

SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.

Affiliations

Laboratory for Atomistic and Molecular Mechanics (LAMM), Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States

Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States

Departments of Oral Biology and Bioengineering, Center for Craniofacial Regeneration, McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States

Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, United States

Departments of Chemistry, Materials Science and Engineering, Geoscience, University of Wisconsin, Madison, Wisconsin 53706, United States

Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

Center for Computational Science and Engineering, Schwarzman College of Computing, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States

Funding

Basic Energy Sciences · National Institute of Dental and Craniofacial Research · Division of Graduate Education · Air Force Office of Scientific Research · National Institute of Biomedical Imaging and Bioengineering · Office of Naval Research · U.S. Department of Health and Human Services · Division of Materials Research

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