ISO 23325:2020

Overview

ISO 23325:2020 - "Dentistry - Corrosion resistance of dental amalgam" - specifies how to determine and limit strength loss of dental amalgam caused by crevice corrosion. The standard applies to amalgam products within the scope of ISO 24234 or ISO 20749 and defines an accelerated in vitro test procedure to assess whether the reduction in mechanical strength from crevice corrosion remains within acceptable limits.

Key topics and technical requirements

• Scope and purpose: Establishes a pass/fail requirement for permissible reduction in strength due to crevice corrosion; intended to differentiate acceptable products rather than rank them.
• Test requirement: The mean fracture force of 10 corrosion-conditioned test-pieces shall be at least 80% of the mean of 10 control (air‑aged) test-pieces.
• Test method: Uses a Hertzian-loading strength-reduction corrosion test (radial cracking initiated from the corroded surface) to evaluate mechanical weakening after immersion in a specified solution.
• Sampling and specimen preparation:
  • Products should be taken from retail packaging and single lots.
  • Minimum alloy mass per test-piece: 3.0 g.
  • Test-pieces are prepared at (23 ± 2) °C and mixed using equipment conforming to relevant ISO requirements.
• Materials and apparatus: References specific apparatus and tolerances for moulds, mixing machines and mixing capsules (e.g., ISO 7488, ISO 13897).
• Corrosion environment: Test solution is an artificial saliva formulation (details and stock solutions provided in the standard) to simulate crevice corrosion conditions.
• Conditioning and mechanical testing: Detailed procedures for conditioning (immersion schedule, control vs. corrosion test-pieces) and mechanical fracture testing (loading arrangement, force application, data treatment) are specified.
• Reporting: Test report requirements and treatment of data are defined to ensure reproducibility and traceability.

Applications and who uses it

• Dental materials manufacturers - to verify corrosion resistance and support product quality claims for dental amalgam formulations and pre‑capsulated products.
• Independent testing laboratories - for regulatory compliance testing, incoming inspection and routine quality control.
• Regulators and conformity assessors - to evaluate whether dental amalgam products meet corrosion-resistance requirements referenced by ISO 24234 / ISO 20749.
• Research and development teams - to screen formulations for crevice corrosion susceptibility during product development.

Related standards

• ISO 24234, ISO 20749 (scope standards for dental amalgam)
• ISO/TS 17988 (corrosion test procedures)
• ISO 10993-1, ISO 7405 (biological hazard assessment - referenced as complementary, not covered by this test)
• ISO 7488, ISO 13897, ISO 1942, ISO 3696, ISO 4287, ISO 6344-1 (normative references for apparatus, terminology and test conditions)

Keywords: ISO 23325:2020, corrosion resistance of dental amalgam, crevice corrosion, Hertzian-loading strength-reduction test, artificial saliva, dental amalgam testing, ISO dental standards.