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Aim: A laboratory study to determine the apical pressure generated by seven canal irrigation methods in an anterior tooth with an open apex., Methodology: Canal irrigation was performed on a 3D-printed central maxillary incisor with an open apex (maximum diameter of 2.1 mm). Ultrasonically activated irrigation (UAI), sonic activation (EDDY), negative pressure irrigation (EndoVac), the self-adjusting file (SAF) and the XP-endo Finisher were employed at tooth length (TL), TL-1 mm, TL-2 mm and TL-3 mm. UAI was tested at three intensity levels additionally. Hydrodynamic irrigation with RinsEndo was performed in the pulp chamber, at the canal orifice, the coronal third, the middle of the canal and at TL. Er:YAG laser activation, at four frequency settings, was performed in the pulp chamber and at the orifice of the canal. The pressure of the fluid towards the canal terminus generated by activation was directly transferred to a pressure sensor with a range of 0 to 120 mmHg and a response time of ≤0.5 ms. The critical threshold for apical extrusion of the irrigant was set at 5.73 mmHg (lower limit of the central venous pressure: 5.88 ± 0.15 mmHg). Each experiment was repeated ten times. The tests were followed by descriptive analyses (maximum, mean, standard deviation, 95% confidence interval)., Results: EndoVac, the SAF, the XP-endo Finisher, and UAI never exceeded the critical threshold at any insertion depth or intensity level. Er:YAG laser activation exceeded the critical threshold exclusively at frequency settings that varied from the manufacturer's recommendation. EDDY at TL and RinsEndo at any insertion depth exceeded the critical threshold in 100% of the measurements. EDDY at TL-1,-2, and-3 mm crossed the critical threshold in 30%, 10%, and 20% of the measurements, respectively., Conclusions: In a simulated maxillary central incisor with an open apex, irrigation with EndoVac, Er:YAG laser activation, UAI, the SAF, and the XP-endo Finisher generated apical pressures below the critical threshold of 5.73 mmHg. By contrast, using EDDY and RinsEndo for irrigation produced higher apical pressures that exceeded the critical threshold., (© 2021 The Authors. International Endodontic Journal published by John Wiley & Sons Ltd on behalf of British Endodontic Society.)

Aim: To compare the amount of apically extruded debris and of remaining filling material during the removal of root canal filling material using three rotary NiTi retreatment instruments or Hedström files., Methodology: Ninety-six severely curved human molars of both jaws were selected. The root canals were prepared to size X2 (tip size 25, .06 taper) using the ProTaper Next system (Dentsply Sirona, Ballaigues, Switzerland), filled with gutta-percha and AH Plus sealer (Dentsply De Trey, Konstanz, Germany) and then randomly divided into four experimental groups (n = 24 each) with two subgroups of maxillary and mandibular teeth each. An experimental model was used as a phantom head to simulate the upper and lower jaws. The root filling materials were removed with one of the following files using a crown-down preparation technique: I. Hedström files (H-files) (VDW, Munich, Germany), II. R-Endo (Micro-Mega, Besançon, France), III. Reciproc (VDW) and IV. ProTaper Universal Retreatment system (PTU-R) (Dentsply Maillefer). Apically extruded material was collected in vials, which were weighed with a microbalance (10 -5  g) before and after the retreatment. The area of residual filling material in the coronal, middle and apical root level was assessed using digital analysis. These data were analysed statistically using ANOVA and the Kruskal-Wallis test., Results: Reciproc was associated with significantly less extruded debris than the H-files (P = 0.009). No significant differences were detected amongst the four retreatment techniques concerning residual filling material (P = 0.082). The amount of extruded debris and areas of remaining filling material were not correlated (P = 0.901). Location of teeth in the maxilla or mandible had no impact on the amount of extruded debris within each instrument group (P = 0.609). However, when teeth were evaluated in general irrespective of the instruments, significantly more debris was extruded in the mandibular location (P < 0.001)., Conclusions: All retreatment systems were associated with apical extrusion of debris, but H-files extruded significantly more material than Reciproc. Remnants of filling material were observed in all samples with no significant differences between the four techniques., (© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To compare the degree of fibre shedding by six brands of endodontic paper point when used for the paper point technique (PPT) of working length confirmation., Methodology: An in vitro model simulating the clinical use of paper points in PPT was used to assess the degree of fibre shedding of six brands of size 20, .02 taper paper point. Whilst observing the artificial terminal foramen with polarized light microscopy, the number of fibres shed directly (point inserted 1 mm beyond the terminal foramen) and indirectly (point inserted to length then a gutta-percha point inserted) was assessed. The degree of direct fibre shedding as a function of brand was analysed with Fisher's exact test and multiple pairwise comparisons. Indirect fibre shedding was analysed with Kruskal-Wallis and Wilcoxon rank-sum tests., Results: All brands shed fibres both directly and indirectly, with a significant influence of brand on the proportion of fibres shed directly (P < 0.0306) and on the mean number of fibres shed indirectly (P < 0.0001). Post hoc analysis demonstrated a similar hierarchy of point integrity for both tests with Classic (UnoDent, Witham, UK) shedding significantly more than other brands and SS White (Gloucester, UK) and Antaeos ® (VDW, Munich, Germany) shedding the least., Conclusion: All brands of paper point may shed cellulose fibres both directly and indirectly with a significant influence of brand on the degree of fibre shedding. Further work should be undertaken to develop biocompatible absorbent dental points., (© 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To compare the amount of debris extruded apically during root canal retreatment using ProTaper, Mtwo and Reciproc instruments with hand H-files., Methodology: In total, 60 freshly extracted human mandibular incisor teeth were used. All root canals were prepared with a Reciproc R25 file than filled with Gutta-percha and AH Plus sealer using cold lateral condensation before being assigned randomly to four groups (n = 15 each). In group 1, root fillings were removed with the Protaper Universal retreatment system; ProTaper Universal F3 and F4 instruments were used for the final preparation. In group 2, root fillings were removed with the Mtwo retreatment system; Mtwo size 30, .06 taper, size 35, .06 taper and size 40, .06 taper files were used for the final preparation. In group 3, root fillings were removed with Reciproc R25 instruments; Reciproc R40 instruments were used for the final preparation. In group 4, the root fillings were removed with Gates Glidden burs and sizes 35, 30 and 25 H-files; for final preparation, a size 40 H-file was used. Glass vials were used for debris collection. The vials were weighed before and after Gutta-percha removal. Additionally, the times required for the retreatment procedures were recorded. Data were analysed statistically using one-way analysis of variance., Results: The Reciproc system produced significantly smaller amounts of apical extruded debris than the other groups (P < 0.05). There was no significant difference between the Mtwo, H-file and ProTaper groups. The ProTaper and Reciproc groups required significantly less time than the Mtwo and H-file groups (P < 0.001)., Conclusions: Use of the reciprocating single file system resulted in the extrusion of significantly less debris compared with the full-sequence rotary NiTi instruments and hand filing. Use of the ProTaper and Reciproc instruments required less time for retreatment procedures than use of the Mtwo or H-file., (© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To evaluate the apical extrusion of debris associated with several root canal preparation systems in vitro., Methodology: Forty-five extracted human mandibular premolars with single canals and similar lengths were used. The root canals were instrumented using ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland), Twisted File (SybronEndo, Orange, CA, USA) or WaveOne (Dentsply Maillefer, Ballaigues, Switzerland). Debris extruded apically during instrumentation was collected into pre-weighed Eppendorf tubes. The Eppendorf tubes were then stored in an incubator at 70 °C for 5 days. The Eppendorf tubes were weighed to obtain the final weight of the Eppendorf tubes plus extruded debris. Three consecutive weights were obtained for each tube. The groups were compared using the Kruskal-Wallis one-way analysis of variance on Ranks and Tukey's test., Results: The ProTaper Next group produced the highest mean extrusion value whilst WaveOne produced less debris compared with all the other instruments (P > 0.05). There was a significant difference between the ProTaper Next and WaveOne group (P < 0.05)., Conclusions: Apically extruded debris was associated with all instrumentation techniques. The WaveOne system extruded less debris compared with the Twisted File and ProTaper Next., (© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To evaluate the influence of reciprocating single-file instrumentation with different working lengths (WL) and apical preparation sizes on apical bacterial extrusion., Methodology: Sixty-eight human single-rooted pre-molars were used. Conventional access cavities were prepared, and the root canals were contaminated with an Enterococcus faecalis suspension and incubated at 37°C for 30 days. Teeth were then divided into four groups of 15 specimens each (Reciproc size 25, .08 taper and Reciproc size 40, .06 taper instruments were used at the foramen; Reciproc size 25, .08 taper and Reciproc size 40, .06 taper instruments were used 1 mm short of the foramen). Positive and negative controls consisted of four infected and four uninfected pre-molars that were instrumented according to each experimental group. Bacteria extruded from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbiological samples were then incubated in a brain-heart agar medium for 24 h. The resulting bacterial titre, in colony-forming units (CFU) per mL, was determined, and these data were analysed using a Wilcoxon matched-pairs signed rank test and a Kruskal-Wallis H-test. The level of significance was set at α = 0.05., Results: No growth was observed in the negative control group. All positive controls demonstrated bacterial growth after the experimental time interval. No significant difference was found in the number of CFU amongst all experimental groups (P = 0.95)., Conclusions: This study showed that the WL and the apical preparation size did not have a significant effect on bacterial extrusion when performing reciprocating instrumentation., (© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To compare apical extrusion of debris in canals prepared with two reciprocating file systems and two different irrigation systems., Methodology: Forty single straight root canals in human mandibular pre-molars were prepared using Reciproc R40 (REC) and WaveOne Large (WO) instruments. Before preparation, the dimensions of a size 40 instrument from each system were measured under scanning electron microscopy (SEM) at 80X. The teeth were randomly divided into four different groups of 10: REC and VPro EndoSafe (REC/VPro); WO/VPro; REC and conventional irrigation (REC/CI); and WO/CI Eppendorf tubes containing a single tooth were weighed on an analytical balance to the nearest 0.1 mg before instrumentation. Irrigation was performed with a total volume of 8 mL of 2.5% sodium hypochlorite. After instrumentation, the teeth were removed from the Eppendorf tube and incubated at 37 °C for 15 days to evaporate the liquid. The tubes were weighed again, and the difference between the initial and final debris weights was calculated and statistically evaluated using analysis of variance (two-way anova) with a significance level of 0.05., Results: No significant difference was observed between the VPro and CI irrigation systems (P > 0.05). Apical extrusion of debris was confirmed in all samples, and extrusion was greater in the REC groups than in the WO groups (P < 0.05). The WO file had a 20% smaller diameter at the tip (D0 ) than the measurement provided by the manufacturer., Conclusions: All systems were associated with apical extrusion of debris. The WO system was associated with less extrusion than the REC system. The amount of extruded debris was independent of the irrigation system used and was related to the instrumentation technique. Morphological analysis of instruments using SEM revealed no correlation between the diameter provided by the manufacturer and the measured diameter for the WO Large file., (© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To assess and compare the amount of extruded debris after canal preparation using ProTaper Universal and ProTaper Next files., Methodology: Forty extracted mandibular premolars with single canals and of similar lengths were instrumented using the ProTaper Universal F3 or the ProTaper Next X3. The extruded debris during instrumentation was collected into pre-weighed Eppendorf tubes. The tubes were stored in an incubator for 5 days. The tubes were weighed to obtain the final dry weight of the extruded debris. The amount of apically extruded debris was calculated by subtracting the initial weight of the tube from the final weight. The distribution of the data was examined using the Shapiro-Wilks test. Continuous variables were compared with an independent-samples t-test for two groups., Results: All specimens were associated with apical debris extrusion. The ProTaper Universal group produced a significantly greater amount of debris extrusion (P < 0.001). The lowest and highest amounts of debris for PTU and PTN groups were recorded as 0.00117-0.00165 g and 0.00017-0.00067 g, respectively., Conclusion: ProTaper Next files was associated with significantly less extruded apical debris when compared to ProTaper Universal files., (© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To evaluate ex vivo, apical bacterial extrusion associated with two reciprocating single-file systems (WaveOne and Reciproc) compared with a conventional multifile rotary system (BioRace)., Methodology: Forty-five human single-rooted mandibular incisors were used. Endodontic access cavities were prepared, and root canals were contaminated with an Enterococcus faecalis suspension. Following incubation at 37 °C for thirty days, the contaminated teeth were divided into three groups of 15 specimens each (G1 - Reciproc, G2 - WaveOne and G3 - BioRace). Positive and negative controls consisted of 5 infected teeth and 3 uninfected incisors that were instrumented with one of the tested NiTi systems, respectively. Bacteria extruded from the apical foramen during instrumentation were collected into vials containing 0.9% NaCl. The microbiological samples were taken from the vials and incubated in brain heart agar medium for 24 h. The resulting bacterial titre, in colony-forming units (CFU) per mL, was determined, and these data were analysed by Wilcoxon matched-pairs signed rank test and Kruskal-Wallis H-test. The level of significance was set at α = 0.05., Results: No significant difference was found in the number of CFU between the two reciprocating systems (P = 0.41). The conventional multifile rotary system group was associated with significantly higher CFU than both of the two reciprocating groups (P = 0.01)., Conclusions: All instrumentation systems extruded bacteria beyond the foramen. However, both reciprocating single-file systems extruded fewer bacteria apically than the conventional multifile rotary system., (© 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To evaluate (i) the effect of irrigant flow rate, needle type, needle insertion depth and apical constriction diameter and (ii) the effect of ultrasonic, sonic and manual dynamic agitation on irrigant extrusion using a recently introduced method., Methodology: Thirty-two human teeth with a straight root canal were prepared to size 35, 0.06 taper and assigned to group A or B. The apical constriction diameter was 0.15-0.25 mm. Specimens were mounted on a plastic vial filled with distilled water to simulate a periapical lesion. A point-conductivity probe was used to determine the volume of irrigant extruded into the vial. Within group A, NaOCl was delivered at 0.14 or 0.26 mL s(-1) by an open-ended or a closed-ended needle at 1 or 3 mm short of working length (WL). In group B, NaOCl was agitated at high or low power either by an ultrasonically or sonically oscillating instrument inserted at 1 or 3 mm short of WL or by manual push-pull strokes of a gutta-percha cone. Results were analysed by repeated-measures anovas, at 0.05 significance., Results: An increase in the flow rate resulted in increased extrusion (P < 0.001). The open-ended needle extruded significantly more irrigant than the closed-ended (P < 0.001). Extrusion decreased as needles moved away from WL (P < 0.001). The effect of apical constriction diameter was not significant (P > 0.454). Manual dynamic agitation extruded significantly more irrigant than sonic and ultrasonic agitation (P < 0.001)., Conclusions: Irrigant flow rate, needle type and insertion depth and agitation technique had a significant effect on extrusion., (© 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Extrusion of intracanal debris as well as irrigants is a common occurrence during root canal treatment, and no instrument or technique has thoroughly solved this problem. Because flare-ups may arise with any irritation directed towards periapical tissues, a shaping or irrigation technique should minimize the risk of apical extrusion, even though it may not be prevented. There has been a rapid evolution of root canal instruments and irrigation systems through the last decade, and many have been assessed for their debris extrusion potential. The purpose of this review was to identify publications regarding the evaluation of debris, bacteria and irrigant extrusion during root canal treatment. A PubMed, Ovid and MEDLINE search was conducted using the keywords "apical extrusion", "debris extrusion" and "endodontic treatment". The literature search extended over a period of more than 30 years up to 2012. Content of the review was limited to apical extrusion of debris and irrigants, extrusion of liquid by irrigation methods and bacterial extrusion. Issues relevant to apical extrusion were obtained by further search in the reference sections of the retrieved articles. The review provides an update on the current status of apical extrusion., (© 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To compare the weight of apically extruded debris associated with canal shaping using K-files, and the Revo-S system using two different needle tips, open-ended and side-vented., Methodology: Forty freshly extracted mandibular premolar teeth were divided into four groups as follows; Group 1a: Hand instrumentation of root canal with open-ended needle used to provide irrigation, Group 1b: Hand instrumentation with a two side-port needle, Group 2a: Revo-S preparation with open-ended needle, Group 2b: Revo-S preparation with a two side-port needle. One Eppendorf tube for each tooth was weighed with a 0.0001 electronic weighing machine before instrumentation procedures. During instrumentation, irrigation was performed after every instrument with 1 mL distilled water. On completion of the preparation, teeth were removed from the Eppendorf tubes. All of the tubes were incubated at 37 °C for 15 days, to evaporate the irrigant. After the incubation period, tubes were weighed again. The difference between pre-and post-debris weights was calculated, and statistical evaluation was performed using analysis of variance at 0.05 level of significance., Results: No statistically significant difference was observed between K-files and the RevoS system. A significant difference was observed between needles (P < 0.05). Open-ended needles were associated with significantly more debris than side-vented needles (P < 0.05)., Conclusions: Both hand and rotary canal instrumentation resulted in extrusion of debris beyond the apical foramen. No significant difference was observed between K-files and Revo-S system. Open-ended needles were associated with significantly more extruded debris than two side-port needles., (© 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.)