Working Length
The measured distance from a coronal reference point to the position where canal instrumentation should terminate, usually the apical constriction.
Full Definition
Working length (WL) is a critical measurement in root canal treatment that defines how deeply instruments and obturating materials should be advanced into the canal to achieve effective debridement without iatrogenic periapical injury. It is established using electronic apex locators, radiographic techniques, or a combination of both, and is recorded in millimetres in operative documentation. Editors should be aware that WL is expressed as 'X mm' (e.g., '21 mm') and typically appears in a dedicated section of the operative note. The abbreviation 'WL' is widely accepted in specialist documents but should be expanded at first use in non-specialist or patient-facing materials.
Usage
Usage note: Always express as a specific numeric value in millimetres when editing operative notes. Do not substitute 'tooth length' or 'file depth.'
In Context
- "Working length was established at 20 mm for the mesiobuccal canal and confirmed radiographically." — Operative report
- "The electronic apex locator displayed a consistent reading, allowing working length to be set at 19.5 mm." — Procedure note