ISO 28158:2018 — Dentistry — Integrated Dental Floss and Handles

1. Understanding ISO 28158:2018 and Its Scope

ISO 28158:2018 specifies requirements and test methods for integrated dental floss and handles, commonly known as dental floss picks. These oral hygiene devices consist of a handle holding a fixed segment of dental floss as an integral part, designed for home care, community care, and professional oral health maintenance for removing plaque and debris from proximal tooth surfaces. The standard covers manual-use products specifically and excludes continuous-supply floss dispensers or handles where floss is subsequently added by the user. Prepared by ISO/TC 106 Dentistry, Subcommittee SC 7 Oral care products, this second edition replaces ISO 28158:2010 with significant technical revisions including an alternative tensile test method and updated displacement criteria.

Good oral hygiene depends heavily on effective interdental cleaning. Traditional flossing techniques using spooled floss require considerable manual dexterity, which many users find challenging. Integrated dental floss and handles offer a more ergonomic solution with a single hand operation, making interdental cleaning more accessible to a broader population including elderly patients, individuals with limited manual dexterity, orthodontic patients with braces, and caregivers assisting others with oral hygiene. The standard does not address biological safety assessment, which is covered by ISO 10993-1 and ISO 7405.

2. Key Requirements, Test Methods, and Performance Criteria

The standard establishes comprehensive requirements for material quality, shape safety, and mechanical strength, with two alternative test methods for strength verification providing flexibility for manufacturers with different testing capabilities:

The static test (Annex A) uses a dead-weight loading system: the specimen is immersed in water at 37 plus or minus 2 degrees C for 90 seconds to simulate the oral environment, then clamped horizontally with the floss axis horizontal. A 10 N weight is applied through a ring with a slit of 3.0 plus or minus 0.5 mm diameter hooked onto the centre of the floss segment. After 10 seconds of loading, the specimen is inspected for floss pull-out from the handle, floss breakage, handle fracture, or displacement exceeding 10 mm. The tensile test (Annex B) uses a push-pull force gauge or tensile testing machine at 300 plus or minus 50 mm/min cross-head speed, providing automated recording of the strain-load relationship for detailed analysis. Both tests are considered equivalent for conformity assessment purposes, allowing manufacturers to choose the method that best fits their quality control infrastructure.

3. Sampling, Pass-Fail Criteria, and Practical Design Implications

The standard requires testing 10 specimens in a three-tier pass-fail system: conform if 8 or more of 10 specimens pass all criteria; non-conform if 6 or fewer pass; and if exactly 7 pass, a repeat test with 10 new specimens is required, with combined results evaluated per Table A.1 which specifies that 16-17 passes out of 20 constitutes conformity. The 10 N strength requirement, equivalent to approximately 1 kg of force, is carefully calibrated to be sufficient for normal flossing tasks while minimizing the risk of gingival injury from excessive force. The instructions for use must recommend a gentle sawing or zig-zag motion during floss insertion and removal to prevent the floss from snapping forcefully into soft gingival tissue.

Engineering Design Insights

The 10 mm displacement allowance under 10 N load provides critical design guidance for product developers. The handle must be sufficiently rigid to limit flex under load while maintaining ergonomic comfort for various grip positions. The floss-to-handle attachment interface is the primary critical failure point, specifically addressed by both test methods which check for pull-out as a distinct failure mode. The 3 mm diameter test ring with slit simulates the contact geometry of tooth surfaces, and the standard specifically warns that smaller rings cause premature breakage from force concentration. Manufacturers may choose between static and tensile testing based on their available equipment, providing quality control flexibility while maintaining consistent safety standards. From a production quality perspective, the tight 10 N threshold demands consistent manufacturing processes: variations in insert molding parameters, material batch properties, or floss tension during assembly can all affect the final product strength. Statistical process control (SPC) methods are recommended for monitoring these critical parameters during high-volume production runs.

4. FAQs