Comparative evaluation of time efficiency and dentin preservation in ultrasonic versus loop retrieval of separated endodontic files: An ex vivo study with pilot nano-computed tomography analysis

Introduction: File separation remains a significant procedural complication. Ultrasonic retrieval often results in excessive dentin removal with prolonged procedural times. Loop devices offer a faster and more conservative alternative. This study evaluated time efficiency and dentin preservation with an indigenously developed loop device compared to ultrasonic only technique using nano-computed tomography (nano-CT). Materials and Methods: Forty extracted human mandibular molars with simulated mid-root fractures of ProTaper Gold F2 files in mesiobuccal canals were divided into two groups ( n = 20 each): Group 1 – ultrasonic only retrieval; Group 2 - indigenously developed loop device following ultrasonic troughing for file exposure. Two operators (experienced vs. novice) performed the procedures per group. The primary outcome was retrieval time, summarized as median (interquartile range [IQR]) using the Mann–Whitney U -test (α = 0.05). Post hoc operator analysis examined operator-related variability. Pilot nano-CT subset (two specimens per group; pre-and post-retrieval) assessed volumetric dentin change descriptively. Results: Group 2 had significantly shorter median retrieval time of 42.97 min (IQR 41.58–44.36) than Group 1 with 56.07 min (IQR 53.53–58.65) ( P < 0.001). The experienced operator was faster ( P = 0.0068) with a smaller interoperator gap in Group 2. In the pilot nano-CT subset, dentin loss was lower with loop (1.60 ± 0.81 mm 3 ) than with ultrasonics (3.07 ± 0.68 mm 3 ). Conclusion: Under standardized ex vivo conditions, the loop technique was more time-efficient and more conservative of dentin than ultrasonic only retrieval.