| research Table 2: ANOVA test values. Total sum of the square Between groups Within groups Total 0.050 0.169 0.218 df 9 190 199 Mean square F Significance 0.006 0.001 6.230 0.000 The 25/0.06 WaveOne Gold file were used with a slow in and out pecking motion, the 25/.12 and variable taper 25/~ HyFlex EDM files were used, the 25/.06 One Shape file were used without pressure and with an in and out motion, the Mtwo files were used in the sequence of 10/.04, 15/.05, 20/.06 and 25/.06, and the variable taper Neoendo files were used in the sequence of 15/.02, 20/.04, 25/.04 and 25/.06 according to the manufactur- ers’ instructions. During instrumentation, each file was removed after three pecking motions and cleaned with gauze. Distilled water was used to irrigate the canals using a 29-gauge side-vented irrigation needle. The procedure was repeated until the file reached the WL: as verified with an apex locator (Endo-Eze FIND Apex Locator, Ultradent). A single operator performed all the pro- cedures to avoid any inter-operator variability. The roots were rinsed with 1 ml distilled water to remove debris adherent to the external surface of the roots and collected in the Eppendorf tubes. The tubes were incubated at 70 °C for five days to evaporate the irrigant. The dry debris was weighed, and the mean of three consecutive readings was recorded. The amount of debris was calculated by subtracting the weight of the pre-weighed empty Eppendorf tubes from the tubes with debris after instrumentation. Statistical analysis and results Statistical analysis was performed utilising SPSS soft- ware (Version 16, IBM). A one-way analysis of variance (ANOVA) and Tukey’s post hoc test were used to analyse the data for multiple comparisons. The level of signifi- cance was taken as P < 0.05. The results showed that the instruments tested caused a measurable amount of debris extrusion apically. The highest amount of debris extrusion was seen in Sub-subgroup IIBc, and Sub-subgroup IIAb showed the least amount of debris extrusion apically (Tables 1 & 2). Discussion This study highlights the role of root canal preparation techniques, kinematics, the number of files used, file cross section, design, taper and motion, and glide path on apical debris extrusion. During root canal prepara- tion, even if the WL is controlled, the risk of extrusion of fragments of pulpal tissue, dentine chips, necrotic debris, microorganisms and intracanal irrigants beyond the apical foramen is present. This can trigger an inflam- matory reaction and thus result in postoperative com- plications. However, apical debris extrusion may differ according to the instrumentation technique and the file design.10, 11 Factors that could affect the extrusion of debris are (a) natural physical factors, such as the anatomy of the apical constriction, hardness of root dentine, quantity, pressure and flow of the irrigation, and position of the tooth; (b) mechanical factors, such as the final instru- ment, apical size, instrumentation technique, pitch design, degree of rotation of the file (full rotation versus reciprocation), speed, number of files used and operator’s skill.12–14 Crown-down preparations with a file with a short pitch design is advised, which results in less debris extru- sion.15 Caviedes-Bucheli et al. suggest that instrument design is the most influential factor rather than the num- ber of files used and type of file motion.16 Side-vented needles were used to reduce periapical extrusion of debris and irrigant compared with open-ended needles. The One Shape file system has a modified triangular design with three sharp cutting edges in the apical and middle parts as well as an S-shaped design with the two cutting edges near the shaft, explaining the reduced debris extrusion. However, the value for Sub-subgroup IIAa was not significant compared with the values for Sub-subgroups IIAb and IIBb. This may be because of HyFlex EDM being a single-file system with controlled memory and a variable cross-section design.17–19 In this study, the rotary file systems showed the least debris extrusion, and efficiency was increased by using glide path files. Improved coronal transportation of dentine chips and debris was seen with continuous movement, whereas reciprocating motion enhanced debris trans- portation towards the apex.20 Bergmans et al. advocate the use of hand instruments before the use of rotary 16 roots 2 2023