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Atomic migration and phase transformation processes in dental amalgams over 27 years, monitored by X-ray spectroscopy and X-ray powder diffraction

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Published/Copyright: January 13, 2025
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Zeitschrift für Naturforschung B
From the journal Zeitschrift für Naturforschung B Volume 79 Issue 12

Abstract

The identification of those intermetallic phases which constitute the complex multi-phase system of dental amalgams is rather contradictory in literature. This is intriguing, as the production processes of dental amalgams are standardized since a long time. The reason for the divergence on reported amalgam phases may be due to changes within the microstructure of dental amalgams occurring over time. With a combination of X-ray powder diffraction, Rietveld refinements and X-ray spectroscopy, we were able to show the differences in chemical phases and morphologies between a freshly prepared and a 27-year old dental amalgam sample. Atomic diffusion processes within the amalgam lead to transformation of initially formed intermetallic phases and to dissolution of phases present in the prealloyed metals which react with Hg to the dental amalgam. The main amalgam phases, Ag1+x Hg1−x and Ag2Hg3, remain stable but change in their relative concentrations: the first increases over time, while the latter decreases. The content of Cu6Sn5 as the third important constituent phase decreases over the years and concentrates in hollow spherical particles. The fourth phase is an fcc Ag–Cu mixed crystal which is only present in the freshly prepared amalgam and dissolves over the years. The silver amalgams form a matrix in which spherical Ag–Cu particles are embedded. Cu atoms migrate from within these particles towards their surface, react to η′ bronze and are substituted by Hg atoms, whereas the Ag atoms show virtually no mobility.

Keywords: dental amalgam; silver amalgam; bronze; Rietveld refinement; EDX spectroscopy
Corresponding author: Constantin Hoch, Department Chemie, LMU München, Bute-nandtstraße 5-13(D), D-81377 München, Germany, E-mail:
Dedicated to Professor Hubert Schmidbaur on the occasion of his 90th birthday.

Acknowledgment

C. H. thanks dental technician Julian Sappl for supplying a sample of commercially available amalgam for dental applications and Dr. med. dent. Jochen Motz for supplying the 27-year old amalgam sample. Many thanks go to Christian Minke from LMU München for EDX measurements and SEM imaging.

  1. Research ethics: Not applicable.

  2. Informed consent: Not applicable.

  3. Author contributions: The author has accepted responsibility for the entire content of this manuscript and approved its submission.

  4. Use of Large Language Models, AI and Machine Learning Tools: None declared.

  5. Conflict of interest: The author states no conflict of interest.

  6. Research funding: None declared.

  7. Data availability: CCDC 2403549-2403554 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

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Received: 2024-11-13
Accepted: 2024-11-16
Published Online: 2025-01-13
Published in Print: 2024-12-17

© 2024 Walter de Gruyter GmbH, Berlin/Boston

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  2. In this issue
  3. Preface
  4. Hubert Schmidbaur 90 years – an appreciation
  5. Reviews
  6. ‘Schmidbaur gold chemistry’ and beyond
  7. The ligand polyhedral model and its application to the structures and fluxional behaviour of the metal carbonyls
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  21. “Coordination caps” of graded electron-donor capacity
  22. The hare and the hedgehog – Similar thermal expansion of argento- and aurophilic contacts for different reasons
  23. Atomic migration and phase transformation processes in dental amalgams over 27 years, monitored by X-ray spectroscopy and X-ray powder diffraction
  24. Book Review
  25. Hubert Schmidbaur: From Chemical Craftsmanship to the Art of Gilding Atoms. (Lives in Chemistry.)
https://doi.org/10.1515/znb-2024-0103
Keywords for this article
dental amalgam; silver amalgam; bronze; Rietveld refinement; EDX spectroscopy

Articles in the same Issue

  1. Frontmatter
  2. In this issue
  3. Preface
  4. Hubert Schmidbaur 90 years – an appreciation
  5. Reviews
  6. ‘Schmidbaur gold chemistry’ and beyond
  7. The ligand polyhedral model and its application to the structures and fluxional behaviour of the metal carbonyls
  8. Research Articles
  9. Equiatomic transition metal (T) silicides TT′Si: systematics of 29Si NMR Knight shifts
  10. New alkaline earth and rare earth representatives adopting the Ce2Al16Pt9-type structure
  11. Bis(2-chloroethyl)sulfane revisited: (ClH4C2)2S⋯S(C2H4Cl) dimers by S⋯S interaction in the solid state
  12. Structural studies of (2R,3R)-(+)-bis(diphenylphosphino)butane and (R)-(+)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl
  13. High-pressure synthesis and crystal structure of Al3BO6
  14. LiEu[BO3]: a lithium europium(II) ortho-oxoborate with a familiar crystal structure
  15. Fluorescence analysis of wood chips and their constituents
  16. C–S–H–PCE nanocomposites as hydration accelerator in calcined clay-limestone-blended low carbon cement
  17. An intermolecular Lewis pair based on tin acid and phosphonium ylide base functions
  18. Cyanopyridine adducts of SiF4 and SiCl4
  19. A [Zn4O(fcCO2)6] oxocarboxylate cluster: synthesis, chemical and physical properties
  20. Homo- and heteronuclear complexes derived from N-picoline-functionalized benzimidazolin-2-ylidene ligands
  21. “Coordination caps” of graded electron-donor capacity
  22. The hare and the hedgehog – Similar thermal expansion of argento- and aurophilic contacts for different reasons
  23. Atomic migration and phase transformation processes in dental amalgams over 27 years, monitored by X-ray spectroscopy and X-ray powder diffraction
  24. Book Review
  25. Hubert Schmidbaur: From Chemical Craftsmanship to the Art of Gilding Atoms. (Lives in Chemistry.)
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