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PubMed · 9552638

Direct metallic amalgam alternative: a research update.

Abstract

Discussions between two group leaders at the National Institute of Standards and Technology (NIST) led to the suggestion that a mercury-free, silver-based material could be used for dental direct-filling applications. This concept brought about a new approach that, nonetheless, is still based on powder technology such as amalgams. The resulting material also retains the tin and silver components of conventional amalgams. The condensation of a loose powder mixture into a cohesive solid relies, however, on cold-welding across atomically clean silver-silver interfaces after a mild acid treatment of the surfaces. The National Institute of Dental Research (NIDR) and American Dental Association Health Foundation (ADAHF) became involved in the research in 1992, and ADAHF scientists continue to collaborate with NIST metallurgists and electrochemists toward the further development of this promising new technology.

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BibTeXRIS

F C Eichmiller, W A Marjenhoff, M P Dariel, D S Lashmore. 1996. Direct metallic amalgam alternative: a research update.. https://pubmed.ncbi.nlm.nih.gov/9552638/

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Failure mode of dental restorative materials under Hertzian indentation.

OBJECTIVE: To explore the application of Hertzian indentation testing to amalgam and GIC; study the failure behavior of the bi-layer structure of each material on a relatively soft substrate; and investigate the effect of thickness. METHODS: Amalgam (Lojic+, SDI, Bayswater, Australia) and ceramic-reinforced GIC (Advanced Healthcare, Tonbridge, UK) discs, 10 mm diameter, thicknesses ranging from 0.4 to 8.0 mm, were tested resting freely on a substrate (30% glass fibre-reinforced polyamide; E=10GPa, 10 mm diameter and 5 mm thick). Increasing load was applied to the center of the disc by a 20 mm-diameter hard steel ball until fracture occurred. Acoustic emission sensing was used as a supplemental method for crack detection. The load at the first crack was recorded. Fracture surfaces were observed under SEM to identify the crack initiation site and the failure mode. RESULTS: The main failure mode of both materials shifted from bottom-initiated radial cracking to near-contact cone cracking or subsurface plastic deformation as the thickness was increased. There was a wide thickness range for the transition of the failure mode for amalgam. Failure load was proportional to the square of thickness for amalgam, except for deviations at small and very large thickness; for the GIC, it was proportional to the thickness to the power approximately 1.6, except for thin layers. SIGNIFICANCE: The Hertzian indentation test can be applied to investigate the failure behavior of amalgam and GIC in addition to ceramics, for which purpose it may have value as a routine test. Failure mode changed with specimen thickness. The importance of considering both failure mode and failure load or strength is emphasized.

Dental Amalgam↗