Aim: This randomized controlled clinical trial compared a novel, noninvasive radiographic method with a fourth-generation electronic apex locator (EAL) for working length determination. Methods: A geometric technique using the law of symmetric triangles was piloted on extracted teeth and applied clinically with a custom sensor holder and digital protractor to standardize angulation. The trial followed Consolidated Standards of Reporting Trials 2025 Guidelines (CTRI/2020/01/022629). A total of 208 root canals from 64 adult patients were randomly assigned into two groups: Digital radiographic (DR) method ( n = 93 canals, 30 patients) and EAL (Root ZX Mini; n = 115 canals, 34 patients). The primary outcome was radiographic master cone fit within ± 2 mm of the apex. The secondary outcomes included obturation length, postoperative symptoms, and lesion healing using the Periapical Index at a 3-month follow-up. Analysis was performed using the SPSS v23.0 ( P < 0.05). Results: Underestimation was significantly lower in the EAL group (1.7%) than in the DR group (15.1%) ( P = 0.0001). Both showed adequate master cone and obturation lengths, with a single overestimation in the DR group (1.07%, P = 0.447). EAL had higher accuracy (61.7%, P = 0.0001), while DR achieved a greater mean lesion size reduction (77% vs. 23%, P = 0.04). Conclusion: Digital radiography showed a similar tendency to underestimate working length as the EAL, with a comparable need for correction. However, it yielded accurate measurements in only about half the cases. Importantly, it achieved significantly greater lesion size reduction. Although less precise, it remains a viable and low-radiation alternative in settings lacking access to EALs.
Minu et al. (2026) studied this question.