Impact of simultaneous working length determination on postoperative pain in curved canals: a randomised controlled trial

Aim: Tri Auto ZX2 (Morita, Saitama, Japan), an endodontic motor with an inbuilt apex locator, claims to offer the new feature of monitoring canal length in real time to facilitate working length control during root canal preparation. As such, the present study aimed to evaluate its applicability and features in clinical settings, especially in curved canals as these tend to straighten during preparation, leading to iatrogenic errors and postoperative pain and requiring continuous monitoring of working length. This study also aimed to determine the impact of simultaneous working length determination on postoperative pain in curved canals.
Materials and methods: Sixty patients with mandibular molars with curved canals as per the eligibility criteria were randomly divided into two groups: Group 1, the control group (separate working length determination and root canal preparation, n = 29), and Group 2, the intervention group (simultaneous working length determination during root canal preparation, n = 31). Single-sitting root canal treatment was performed using Tri Auto ZX2. Patients’ age, sex, tooth number, root canal curvature, preoperative and postoperative pain assessed on the Heft-Parker visual analogue scale and analgesic intake were recorded. The data were analysed using a chisquare test, independent-samples t test and paired t test.
Results: There was a significant reduction in postoperative pain in Group 2 on days 1, 5 and 7 (P < 0.05). Group 2 showed a significant reduction in postoperative pain irrespective of canal curvature as compared to Group 1, with a significant difference in moderately curved canals (P < 0.05). Only two patients from Group 2 required analgesics, whereas nine patients required them in Group 1.
Conclusion: Working length determination during root canal preparation provides real-time canal measurement and kinematic features that help to reduce postoperative pain. The new feature of Tri Auto ZX2 can be clinically applied for single-sitting root canal treatment irrespective of canal curvature and severity of preoperative pain.