ISO 2157:2016

Overview

ISO 2157:2016 establishes a standardized system of nominal diameters and corresponding three-digit designation code numbers for dental rotary instruments. The standard covers working parts of instruments such as burs, laboratory burs, grinding instruments, diamond instruments and mandrels. It excludes diameters for endodontic instruments and scaler tips. Designation codes express diameters in tenths of a millimetre and are used as part of the coding system in ISO 6360 (all parts).

Key Topics

• Nominal diameter ranges: The document lists selectable nominal diameters in three ranges - 0.5 mm to 2.3 mm; 2.5 mm to 9.5 mm; and 10 mm to 30 mm - with specific code numbers assigned to each diameter.
• Three-digit designation: Each nominal diameter is represented by a three-digit code (for example, 005 = 0.5 mm; 100 = 10.0 mm) used in instrument number coding.
• Preferred series (R 20): In the 2.5 mm to 9.5 mm range the R 20 preferred-number series is recommended to reduce the number of sizes (reducing 21 sizes to 12 preferred sizes in that range).
• Normative references: ISO 2157:2016 references ISO 3 (preferred numbers), ISO 1942 (dental vocabulary) and ISO 6360-1 (number coding system for rotary instruments - general characteristics).
• Terminology and scope: The standard defines terms such as ‘‘nominal diameter’’, ‘‘designation code number’’ and ‘‘rotary instrument’’, aligning with ISO 1942 and ISO 6360-1 definitions.

Applications

ISO 2157:2016 provides practical value for a range of stakeholders:

• Manufacturers: Standardized diameters and codes simplify tooling specification, production planning and product labelling.
• Dental laboratories and clinics: Clear sizing and code numbers improve ordering, inventory management and instrument interchangeability across suppliers.
• Regulatory and procurement: Harmonised dimensions and codes support compliance, technical documentation and procurement specifications.
• Technical documentation & coding systems: The three-digit designations integrate with ISO 6360 coding schemes for consistent part numbering and data exchange.

Related Standards

• ISO 6360 (all parts) - Number coding system for rotary instruments; ISO 2157 designations form part of this coding framework.
• ISO 1942 - Dentistry vocabulary referenced for terms and definitions used in ISO 2157.
• ISO 3 - Preferred numbers series (R 20) used to recommend sizes within certain ranges.

By standardising nominal diameters and designation codes, ISO 2157:2016 helps ensure consistent sizing, clearer communication between manufacturers and users, and improved interchangeability of dental rotary instruments across clinical and industrial contexts.