ISO/TS 20746:2016 PDF

Overview

ISO/TS 20746:2016 - "Dentistry - Determination of the strength of dental amalgam by the Hertzian indentation strength (HIT) method" provides practical, repeatable procedures for measuring the strength of dental amalgam using the Hertzian indentation strength (HIT) test. The method uses a disc-shaped specimen loaded centrally by a hardened steel ball to induce radial cracking; the resulting fracture force is used to quantify and compare the resistance to fracture of amalgam products. The specification is applicable to amalgams within the scope of ISO 24234 and ISO 20749 and can be applied to other brittle or low-plasticity restorative materials.

Key topics and technical requirements

• Specimen geometry and manufacture
  • Disc-shaped test-pieces (packed to produce approx. 10 mm diameter × 3 mm height).
  • Mould construction: hardened tool or stainless steel with flat, parallel end faces; tapered hole (included angle (7 ± 2)°) to allow ejection without damage.
  • Polished glass plate used to form the test surface; no grinding or polishing after ejection.
• Mixing and environmental conditions
  • Mixing performed at (23 ± 2) °C using mechanical mixers compliant with ISO 7488 and manufacturer’s recommended settings.
  • Set time and handling practices (e.g., allow 10 min initial set before ejection).
• Apparatus and test setup
  • HIT loading: linearly increasing force applied through a chrome steel ball to the centre of one face; specimen supported on a substrate with stiffness similar to dentine (e.g., 30% glass-filled polyamide disc as illustrated).
  • The test reproduces localized loading and radial crack initiation analogous to oral function.
• Inspection, measurement and data treatment
  • Visual inspection under specified illuminance (≥1000 lx) to detect surface defects; measurement of thickness using micrometre instruments.
  • Report fracture force and any relevant test conditions; follow the document’s data treatment and reporting clauses.

Applications and users

• Who uses this standard
  • Dental materials manufacturers (product development and quality control).
  • Independent test laboratories and research institutions assessing restorative material strength.
  • Regulatory bodies and standards committees comparing performance across products.
• Practical value
  • Provides a reproducible method to rank amalgam products by fracture resistance under localized loading.
  • Useful in R&D for formulation optimization and in verification testing for conformity with product claims.
  • Applicable to other brittle dental restorative materials where localized indentation fracture is of interest.

Related standards

• ISO 24234 - Dentistry - Dental amalgam
• ISO 20749 - (related to dental amalgam products)
• ISO 7488 - Dental amalgamators (mixing equipment)
• ISO 13897 - Dentistry - Amalgam capsules
• ISO 13565-2 - Surface texture characterization
• ISO 6344-1 - Coated abrasives - Grain size analysis

Keywords: ISO/TS 20746:2016, Hertzian indentation strength, HIT method, dental amalgam test, fracture force, dentistry standards, dental materials testing.