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Chemical gradients in human enamel crystallites.
Nature. 2020 07; 583(7814):66-71.Nat

Abstract

Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development.

Authors+Show Affiliations

Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY, USA.School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, USA. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA.School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA. Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY, USA.Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. d-joester@northwestern.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

32612224

Citation

DeRocher, Karen A., et al. "Chemical Gradients in Human Enamel Crystallites." Nature, vol. 583, no. 7814, 2020, pp. 66-71.
DeRocher KA, Smeets PJM, Goodge BH, et al. Chemical gradients in human enamel crystallites. Nature. 2020;583(7814):66-71.
DeRocher, K. A., Smeets, P. J. M., Goodge, B. H., Zachman, M. J., Balachandran, P. V., Stegbauer, L., Cohen, M. J., Gordon, L. M., Rondinelli, J. M., Kourkoutis, L. F., & Joester, D. (2020). Chemical gradients in human enamel crystallites. Nature, 583(7814), 66-71. https://doi.org/10.1038/s41586-020-2433-3
DeRocher KA, et al. Chemical Gradients in Human Enamel Crystallites. Nature. 2020;583(7814):66-71. PubMed PMID: 32612224.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Chemical gradients in human enamel crystallites. AU - DeRocher,Karen A, AU - Smeets,Paul J M, AU - Goodge,Berit H, AU - Zachman,Michael J, AU - Balachandran,Prasanna V, AU - Stegbauer,Linus, AU - Cohen,Michael J, AU - Gordon,Lyle M, AU - Rondinelli,James M, AU - Kourkoutis,Lena F, AU - Joester,Derk, Y1 - 2020/07/01/ PY - 2019/08/23/received PY - 2020/04/08/accepted PY - 2020/7/3/entrez PY - 2020/7/3/pubmed PY - 2020/7/17/medline SP - 66 EP - 71 JF - Nature JO - Nature VL - 583 IS - 7814 N2 - Dental enamel is a principal component of teeth1, and has evolved to bear large chewing forces, resist mechanical fatigue and withstand wear over decades2. Functional impairment and loss of dental enamel, caused by developmental defects or tooth decay (caries), affect health and quality of life, with associated costs to society3. Although the past decade has seen progress in our understanding of enamel formation (amelogenesis) and the functional properties of mature enamel, attempts to repair lesions in this material or to synthesize it in vitro have had limited success4-6. This is partly due to the highly hierarchical structure of enamel and additional complexities arising from chemical gradients7-9. Here we show, using atomic-scale quantitative imaging and correlative spectroscopies, that the nanoscale crystallites of hydroxylapatite (Ca5(PO4)3(OH)), which are the fundamental building blocks of enamel, comprise two nanometric layers enriched in magnesium flanking a core rich in sodium, fluoride and carbonate ions; this sandwich core is surrounded by a shell with lower concentration of substitutional defects. A mechanical model based on density functional theory calculations and X-ray diffraction data predicts that residual stresses arise because of the chemical gradients, in agreement with preferential dissolution of the crystallite core in acidic media. Furthermore, stresses may affect the mechanical resilience of enamel. The two additional layers of hierarchy suggest a possible new model for biological control over crystal growth during amelogenesis, and hint at implications for the preservation of biomarkers during tooth development. SN - 1476-4687 UR - https://www.unboundmedicine.com/medline/citation/32612224/Chemical_gradients_in_human_enamel_crystallites L2 - https://doi.org/10.1038/s41586-020-2433-3 DB - PRIME DP - Unbound Medicine ER -