Overview
EN ISO 2157:2016 specifies the nominal diameters of the working parts of dental rotary instruments and the corresponding three-digit designation code numbers. Published as an ISO international standard and endorsed by CEN, the document covers burs, laboratory burs, grinding and diamond instruments, mandrels and similar rotary tools. It excludes the diameters of endodontic instruments and scaler tips.
This standard defines the theoretical (nominal) diameters in millimetres and provides the designation code numbers used as part of the ISO 6360 number coding system for rotary instruments.
Key Topics
- Scope and definitions: terms such as nominal diameter, designation code number and rotary instrument are aligned with ISO 1942 and ISO 6360-1.
- Designation format: diameters are expressed in tenths of a millimetre and shown as a three-digit code number (for example, 0.5 mm → 005).
- Diameter ranges and tables:
- Table 1: range 0.5 mm to 2.3 mm (examples: 0.5 mm = 005, 1.0 mm = 010, 2.3 mm = 023).
- Table 2: range 2.5 mm to 9.5 mm - the standard recommends using the R 20 series preferred sizes to reduce the number of diameters in this interval (example: 2.5 mm = 025, 3.15 mm = 031, 4.50 mm = 045).
- Table 3: range 10 mm to 30 mm (examples: 10.0 mm = 100, 30.0 mm = 300).
- R 20 series recommendation: substituting R 20 series sizes in the 2.5–9.5 mm range reduces duplication and simplifies manufacturing and inventory management.
Applications
EN ISO 2157:2016 provides practical value across the dental products lifecycle:
- Manufacturing & design: consistent nominal diameter definitions support repeatable production, tooling selection and quality control.
- Product labelling & coding: three-digit designation numbers enable clear identification and integration with ISO 6360 coding schemes.
- Procurement & inventory: standardized sizes simplify ordering, interchangeability and stock management for clinics and dental laboratories.
- Regulatory & conformity: adoption of the standard assists compliance with national and European standardization rules and improves traceability.
Related Standards
- ISO 6360-1 - Number coding system for rotary instruments (general characteristics) - for full instrument coding.
- ISO 1942 - Dentistry vocabulary - for harmonized terminology.
- ISO 3 - Preferred numbers - referenced for R 20 series sizes.
Note: EN ISO 2157:2016 supersedes earlier editions and was approved by CEN as the European adoption of ISO 2157:2016. For implementation, refer to the normative tables in the standard and the referenced ISO documents for definitions and coding rules.
