- The primary purpose of determining the working length during root canal therapy is to ensure the complete debridement of pulp tissue, bacteria, and necrotic debris up to the apical constriction.
- The working length is the distance from a coronal reference point to the point where canal preparation and filling should terminate.

Precisely establishing this length is critical because:
- Effective cleaning and shaping of the root canal system depends on accurate canal length measurement.
- It helps prevent over-instrumentation beyond the apical foramen, which can cause periapical tissue damage or irritation.
- It avoids under-instrumentation, which may leave residual infected tissue and reduce the success of treatment.

Options such as protecting the coronal enamel or measuring dentin thickness for posts are unrelated to the working length. While accessory canals do exist, their identification is not the primary purpose of determining working length.

Accurate working length determination is typically achieved through radiographs or electronic apex locators, helping the clinician optimize the outcome of root canal therapy.

Reference: Grossman’s Endodontic Practice, 13th Edition, Chapter 7: Cleaning and Shaping of the Root Canal System, p. 195-198