Introduction: All preparation techniques and instruments are associated with apically extruded debris (AED). Different preparation techniques promote different amounts of AED justified by the instruments design, namely its cross section, conicity, tip design and also the number of files, kinematics and cutting efficiency, associated with the quantity, type and technique of irrigation.
Objective: Compare the amount of AED, created by two hybrid techniques and two single system techniques. The null hypothesis formulated stated that all groups present the same amount of AED.
Materials and Methods: Eighty single root canal teeth were randomly assigned into 4 groups (n=20), according to the instrumentation technique: hybrid technique TruNatomy®/ProTaper Gold® (TN/PTG), hybrid technique TruNatomy/ProTaper Next® (TNP/TN), system ProTaper Gold (PTG) and system ProTaper Next (PTN) (Dentsply Sirona, Ballaigues, Switzerland). During preparation, for each specimen, a total of 13 mL 3% sodium hypochlorite (NaOCl) was used. AED was collected in Eppendorf tubes (ET). After instrumentation, each tooth was removed from the ET and, after filling with 1.5 mL NaOCl, each ET was stored in an incubator at 70ºC for 5 days. Three ET, without AED, containing 1.5mL 3% NaOCl were used as control. After the incubation period, each ET was weighed three times to obtain an average weight. The amount of AED, in each ET, was calculated by subtracting the control-weighed ET to the post-preparation weight. After checking normality (Shapiro-Wilk test), the Kruskal-Wallis non-parametric test was performed followed by the Mann-Whitney test with Bonferroni correction to identify significant differences (α=0.05).
Results: Significant differences in the AED were detected for the various techniques (p<0.001). The hybrid techniques TN/PTG and TN/PTN groups produced significantly less extrusion compared to the PTG and PTN techniques (p=0.012 and p=0.046, respectively). The TN/PTN technique had a significantly lower AED than the other groups (p≤0.046) and the PTG technique significantly higher (p≤0.012).
Discussion: In this study, the superior performance of the PTN system can be justified by the type of movement, less taper than PTG files and the type of cross-section that these instruments have, as well as the fact that this system has a smaller number of files. The significantly smaller differences related to AED, between TN/PTG and TN/PTN hybrid techniques and PTG and PTN alone, respectively, may be related to the fact that TN instruments have a maximum cervical diameter of 0.8mm which promotes greater dentin preservation when compared to S1, S2 and X1 files which cut the pericervical dentin more aggressively, as they have 1.20 maximum cervical diameter. Consequently, performing Preflaring with smaller cervical diameter before Root Canal preparation can reduce the amount of AED.
Conclusion: Hybrid instrumentation techniques TN/PTN and TN/PTG produced significantly less AED than the PTN and PTG techniques.