Assessment of apical debris extrusion with three nickel–titanium rotary systems using conventional and lyophilization-based quantification methods

Background: Apical extrusion of debris during root canal preparation is inevitable and may contribute to postoperative pain and periapical inflammation. The extent of extrusion varies with instrument design and motion. ProTaper Next (PTN), TruNatomy (TN), and HyFlex EDM (HEDM) systems feature distinct geometries and tapers aimed at improving shaping efficiency while reducing extrusion. The conventional Myers and Montgomery model for debris quantification lacks precision in moisture control, whereas lyophilization (freeze-drying) offers a novel, potentially more accurate alternative. Aim: The aim is to compare apically extruded debris using rectangular cross-section file system (PTN), parallelogram cross-section file system (TN), and variable cross-section file system (HEDM), and to assess lyophilization as a quantification method. Materials and Methods: Ninety extracted single-canal premolars (curvature <5°) were randomly assigned to two main groups ( n = 45). Group 1 measured debris using the Myers and Montgomery model, while Group 2 used lyophilization. Each group was subdivided into three subgroups – rectangular cross-section file system, parallelogram cross-section file system, and variable cross-section file system. Canals were irrigated with 2 mL bidistilled water after each file sequence, and extruded debris was quantified per the respective method. Results and Conclusion: All samples exhibited debris extrusion. Parallelogram cross-section file system (TN) produced the least extrusion, though differences were not statistically significant. Lyophilization demonstrated reliability and precision for debris quantification.