The impact of kinematics, single-file technique and preparation time on the apical extrusion of debris

Aim: To compare canal preparation time and apical extrusion of debris during instrumentation with the ProTaper Next (PTN), HyFlex CM (HCM), HyFlex EDM (HEDM), WaveOne Gold (WOG), and Reciproc Blue (RCB) systems. Methodology: Seventy-five roots of extracted mandibular first molars, with curved mesiobuccal canals (10-20 degrees) and independent foramina, were distributed across 5 experimental groups (n=15 each) according to the instrumentation system used. Roots were secured in Eppendorf tubes, the canals were irrigated with double-distilled water, and the instrumentation time was recorded. After instrumentation, the roots were removed from the Eppendorf tubes and the amount of extruded debris was calculated by subtracting the initial weight from the final weight. The assumption of normality was rejected by the Shapiro-Wilk test, followed by the Kruskal-Wallis test with a post-hoc Dunn's test. A simple linear regression analysis was run to test for correlation between amount of extruded debris and time required for instrumentation. Results: The PTN and HCM systems were associated with significantly (p<0.05) greater amounts of extruded debris and longer instrumentation time (PTN and HCM HEDM, WOG, RCB). There was no significant difference between the PTN and HCM groups (p>0.05), nor between the HEDM, WOG, and RCB groups (p>0.05). Simple linear regression demonstrated a positive correlation (r=0.74, p<0.05) between the amount of debris extruded and instrumentation time. Conclusions: The RCB, WOG, and HEDM systems were associated with less debris extrusion and shorter instrumentation time when compared to the PTN and HCM systems.