Root canal working length determination and apical limit of root canal instrumentation and obturation

Aim: To evaluate the preferred method of root canal length determination and the apical limit for canal instrumentation and obturation amongst endodontic teachers at a dental school. Materials and methods: A questionnaire on the preferred method of root canal length determination and the apical limit for canal instrumentation and obturation was designed and distributed to staff teaching Endodontics. Results: The response rate was 82.1%. Most of the respondents were ≤ 40 years old (52.2%), trained/qualified from a UK-based institution (78.2%); over 78.2% had a further qualification. For the majority, General Dentistry or Prosthodontics were their primary practice field (30.4% each). The full-timers were mostly in academia (50.0%); most part-timers worked in hospital services (27.3%). All used radiographs to determine working length. Additional methods included preoperative radiographs (65.2%), electronic apex locators (EALs) (87%), tactile feel (17.4%) and the paper point test technique (4.3%). The median number of length determination methods was three. The most favoured apical limit was up to 0.5 mm short of the radiographic apex for canal instrumentation (39.1%) and 1.0 mm for obturation (47.8%); the majority preferred to instrument and obturate to the same apical limit. There was a statistically significant relationship between the desired apical limit for canal instrumentation and obturation (P = 0.019). Conclusions: The most popular method for determining working length was EALs; over half used both EALs and radiography. There was no agreement on the apical limit for canal instrumentation and obturation; the most desired limit was 0.5 mm from the radiographic apex for canal instrumentation, and 1 mm for obturation. The majority preferred to both instrument and obturate to the same apical limit. Keywords: apical limit, root canal, working length