Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects.

The aim of this study was to investigate the effects of glycolic acid (GA) on the microhardness, roughness, dentin mineral content distribution; smear layer removal and cytotoxicity. One hundred human teeth were randomly divided into six groups: distilled water (control group), 17% EDTA, 10% citric acid (CA), 5% GA, 10% GA, and, 17% GA. Microhardness and roughness were measured in the canal lumen. Scanning electron microscopy (SEM) images (2000×) for smear layer removal evaluation; energy dispersive X-ray spectroscopy (EDS) for chemical analysis. Cell viability assay was made on fibroblast cells. The lowest microhardness and higher roughness were observed for 17% GA. GA showed the ability to remove the smear layer to a similar level as EDTA and CA, with no statistical difference between the concentrations used. GA and CA were cytotoxic in a dose-dependent manner. GA showed potential as an endodontic agent for final irrigation in root canal terapies.

Effect of smear layer thickness and pH of self-adhesive resin cements on the shear bond strength to dentin.

CONTEXT: There are concerns in relation to the bonding efficacy of self-adhesive resin cements to dentin covered with the smear layer. AIMS: This study aims to evaluate the effect of smear layer thickness and different pH values of self-adhesive resin cements on the shear bond strength to dentin. MATERIALS AND METHODS: The dentin on the buccal and lingual surfaces of 48 sound human premolars were abraded with 60- and 600-grit silicon carbide papers to achieve thick and thin smear layers, respectively. The samples were divided into three groups (n = 16) based on the cement pH: Rely-X Unicem (RXU) (pH < 2); Clearfil SA Luting (CSL) (pH = 3); and Speed CEM (SPC) (pH = 4.5). In each group, composite resin blocks were bonded to the buccal and lingual surfaces. After 24 h, the shear bond strength values were measured in MPa, and the failure modes were evaluated under a stereomicroscope. STATISTICAL ANALYSIS: Data were analyzed with two-way ANOVA and post hoc least significant difference tests (P < 0.05). RESULTS: Cement pH had a significant effect on the shear bond strength (P = 0.02); however, the smear layer thickness had no significant effect on the shear bond strength (P > 0.05). The cumulative effect of these variables was not significant, either (P = 0.11). CONCLUSION: The shear bond strengths of SPC and CSL self-adhesive resin cements were similar and significantly lower than that of RXU. The smear layer thickness was not a determining factor for the shear bond strength value of self-adhesive resin cements.

Dentin Topographic Features following Chemomechanical Caries Removal in Primary Teeth.

AIM: Study the topographic features of dentin after caries removal with a chemomechanical agent (Papacarie) compared with the conventional drilling method. STUDY DESIGN: The sample included 7 exfoliated and extracted primary teeth with carious dentin lesions, not reaching the pulp. Each tooth was sectioned longitudinally through the center of the carious lesions into two halves. The teeth were then divided into two groups according to the method of caries removal. Following caries removal, dentin topography and the cut section were examined using the scanning electron microscope. RESULTS: Papacarie produced an irregular, porous, rough and globular dentin appearance. The dentin surfaces were generally free of smear layer, visible bacteria and the dentinal tubules were opened. The dentin cut surfaces showed patent dentinal tubules with open orifices. The drilling method created a smooth and amorphous surface with a continuous smear layer occluding the dentinal tubules. Numerous bacteria were also observed. The cut dentin surfaces showed patent dentinal tubules with their orifices plugged with smear layer. CONCLUSIONS: Papacarie produced a rough and porous surface with partial or complete removal of the smear layer and opened dentinal tubules, while the drill produced a smooth surface with uniform smear layer occluding the dentinal tubules.

Influence of Root Canal Tapering on Smear Layer Removal.

The purpose of the study presented here was to compare the influence of root canal taper on the efficacy of irrigants and chelating agents in smear layer removal. Eighty mesial roots of molar teeth were selected and prepared with rotary instruments. In group A, file 30/0.02 and in group B, file 30/0.4 were placed at working length and the smear layer was removed. In groups C and D, root canal preparation was the same as in groups A and B, respectively, except that the smear layer was not removed. The amount of the smear layer was quantified using a scanning electron microscope. Greater smear layer was detected in the apical portion of each group, whereas no significant difference was detected between groups in other portions. No statistical difference was found between canals with different tapers.

Influence of diode laser application on the efficiency of QMiX and EDTA solutions in removing smear layer.

OBJECTIVE: The aim of this study was to compare the efficacy of QMiX and ethylenediaminetetraacetic acid (EDTA) solutions with diode laser treatment in smear layer removal. BACKGROUND DATA: Removing the smear layer from the apical thirds of root canals is difficult, regardless of the solution used. Researchers have been improved some irrigation agitation methods to overcome this challenge, and agitation of irrigants with laser devices has become popular. METHODS: Seventy-five extracted mandibular premolars were used. After root canals were, prepared the specimens were divided into five groups (n = 15): Group 1, no irrigation; Group 2, 17% EDTA; Group 3, QMiX solution; Group 4, 17% EDTA with diode laser; and Group 5, QMiX with diode laser. The roots were split longitudinally and prepared for scanning electron microscopic (SEM) investigation. The smear layer was evaluated under × 500, × 1000, and × 2000 magnifications. RESULTS: The amount of smear layer was found significantly high in the control group (p < 0.001). In the EDTA group, the amount of smear layer was significantly high at the apical thirds, and the differences among the three regions were statistically significant (p < 0.001). In the QMiX group, no difference was found between the coronal and middle thirds; however, the amount of smear layer was significantly high at the apical thirds (p < 0.001). In the EDTA plus laser and the QMiX plus laser groups, the smear layer was found significantly high at the apical thirds (p < 0.001). However, no differences were found between the coronal and middle thirds in either group. CONCLUSIONS: None of the solutions completely removed the smear layer, especially at the apical thirds. Diode laser treatment with solutions decreased the amount of smear layer, without significance.

Evaluation of the smear layer removal and erosive capacity of EDTA, boric acid, citric acid and desy clean solutions: an in vitro study.

BACKGROUND: The purpose of this study was to investigate the smear layer removal and erosive capacity of various irrigation solutions with sequential use of NaOCl on instrumented root canal walls. METHODS: The root canals of single-rooted teeth were instrumented with ProTaper rotary instrument. Then, the teeth were randomly divided into five experimental groups. The root canals were irrigated with one of the following solutions (5 mL/1 min): 5% EDTA, 5% boric acid (BA), a mixture of BA and CA, 2.5% citric acid (CA) and 5% Desy Clean. After irrigating with 2.5% NaOCl and distilled water, the roots were split into two halves and each half was prepared for SEM examination. Representative photographs were taken from each third at x500 and x1000 magnifications. Double blind scoring was performed by two calibrated observers for smear layer and erosion. The scores were statistically analyzed using Kruskal-Wallis, Dunn's post hoc and Spearman's correlation tests (p = 0.05). RESULTS: There were statistically significant differences among the solutions by means of smear layer and erosion (p < 0.05). While 2.5% CA solution was the most effective solution in removal of smear layer, it was also the most erosive solution (p < 0.05). 5% Desy Clean removed smear layer effectively and caused less erosion. There was a negative, but statistically significant correlation between presence of smear layer and erosion (r = -0.684; p < 0.0001). CONCLUSION: Desy Clean can be a promising agent as an irrigation solution with optimal smear layer removal capacity and less erosive effects.

Comparison of apical and coronal extrusions using reciprocating and rotary instrumentation systems.

BACKGROUND: The aim of this study was to compare the apical and coronal extrusions by using two reciprocating and two rotary instrumentation systems. METHODS: Eighty extracted human single-rooted anterior teeth were randomly assigned to four groups. Four different root canal instrumentation systems were used according to the manufacturers instructions, including two reciprocating single-file systems, Reciproc and WaveOne, and two full-sequence rotary BLX and ProTaper instruments. Debris collected from the coronal by the instruments and apical extrusions were quantified respectively. After drying the collections, the mean weight of debris collected from apical and coronal extrusions was assessed using an electronic balance and analyzed using the Kruskal-Wallis H and Mann-Whitney U tests. RESULTS: Statistically significant differences in the apical extrusion were observed among the four groups. Reciproc and WaveOne instruments produced significantly less debris than BLX and ProTaper instruments (P < 0.05). CONCLUSIONS: All of the systems produced apical extrusion of debris. However, reciprocating single-file systems produced less apical extrusion than full-sequence rotary systems. No relationship was observed between apical and coronal extrusions.

Effect of Model Variables on in vitro Erosion.

The aim of this study was to investigate the effects of tooth type (molar/premolar), tooth surface (buccal/lingual), smear layer or no smear layer, storage of specimens in deionised water, mode and speed of agitation, and rinsing method between cycles on mean step height loss and Knoop microhardness (KHN) change. Polished human enamel specimens embedded in acrylic resin were prepared from sound permanent molar and premolar tooth surfaces. A 0.3% (pH 3.2) solution of citric acid was used to erode the specimens, in a cycling procedure, consisting of 10 min immersion followed by rinsing in deionised water for 30 s with a spray bottle, for 5 cycles. The specimens were analysed with a non-contact white light profilometer and KHN. Molar teeth (148.99±24.49 KHN) and buccal surfaces (155.62±30.35 KHN) produced significantly less microhardness change compared to premolar (186.40±20.74 KHN) and lingual surfaces (179.76±23.21 KHN; p<0001). The effect of storage and rinsing showed little difference in mean step height loss (<1 µm) and microhardness change. With no smear layer a significantly lower mean step height loss and microhardness change (p<0.001) was observed. Agitation was performed with Orbital, Gyro and See-Saw rockers at 30, 40, 60, and 70 rpm. The mean step height loss was largest for See-Saw at 70 rpm (11.73±0.91 µm) and lowest for Orbital at 30 rpm (2.76±1.12 µm). A statistical difference was found between all types of agitation and speeds (p<0.001). In conclusion, this study has shown that the variables investigated here have a significant impact on the measurable outcome, highlighting the importance of accurate and detailed method sections.

Comparison of smear layer removal using the Nd:YAG laser, ultrasound, ProTaper Universal system, and CanalBrush methods: an in vitro study.

INTRODUCTION: The aim of this study was to compare the efficacy of the Nd:YAG laser, ultrasound, the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland), and the CanalBrush (Coltene Whaledent, Langenau, Germany) methods for the removal of the smear layer from the apical third of root canals. METHODS: Fifty distal root canals from extracted human mandibular first molars were instrumented up to ProTaper Universal F5 and divided randomly into 5 groups (n = 10) according to the following final irrigation agitation techniques: no agitation (control), ProTaper Universal file, ultrasound, CanalBrush, and Nd:YAG laser. Specimens were observed under a scanning electron microscope. The presence of the smear layer was evaluated using a 3-grade scoring system. The data were analyzed with Cohen kappa, Kruskal-Wallis, and Mann-Whitney U tests. A level of significance of .05 was adopted. RESULTS: The ultrasound group performed significantly better than the rest of the groups; 56.6% of the specimens revealed no smear layer, 44.4% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In the Nd:YAG laser group, 30% of the specimens presented with no smear layer, 70% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In contrast, a heavy smear layer was observed on the surfaces of the root canals in the CanalBrush (23.4%), ProTaper Universal (13.4%), and control (86.6%) groups. Statistically significant differences were observed (P < .05). CONCLUSIONS: None of the agitation methods completely removed the smear layer. However, the ultrasound method performed significantly better followed by the Nd:YAG laser, the CanalBrush, and the ProTaper Universal system. Agitation of the irrigant improved smear layer removal in the apical third of the canal.

Phytic acid: an alternative root canal chelating agent.

INTRODUCTION: The objectives of this study were to investigate the effect of phytic acid, inositol hexakisphosphate (IP6), as a final rinse on the surface of instrumented root canals and smear-layered flat dentin surfaces treated with sodium hypochlorite (NaOCl) and to evaluate its effect on the viability and alkaline phosphatase activity of osteoblast-like cells (MC3T3-E1). METHODS: The universally accepted chelating agent EDTA was used as the control in all conducted experiments. Root canals of human canines were instrumented with rotary files and irrigated with 5% NaOCl, followed by a final rinse of 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. NaOCl-treated flat coronal dentin surfaces were also treated with 17% EDTA (1 minute), 1% IP6 (1 minute or 30 seconds), or distilled water. The presence or absence of smear layer was evaluated with scanning electron microscopy. Cell viability and alkaline phosphatase assays were performed to evaluate the effect of IP6 and EDTA on cultured MC3T3-E1 cells. RESULTS: The results demonstrated the ability of IP6 to remove the smear layer from instrumented root canals and flat coronal dentin surfaces. When compared with EDTA, IP6 was less cytotoxic and did not affect the differentiation of MC3T3-E1 cells. CONCLUSIONS: IP6 shows the potential to be an effective and biocompatible chelating agent.

Apical extrusion of debris in flat-oval root canals after using different instrumentation systems.

INTRODUCTION: The purpose of this study was to evaluate the amount of apically extruded debris in flat-oval root canal systems during cleaning and shaping with different instrumentation systems. METHODS: Seventy-two mandibular incisors were randomly assigned to 4 groups (n = 18) according to the instrumentation system to be used: the ProTaper Next rotary system (PTN; Dentsply Tulsa Dental, Tulsa, OK), the WaveOne reciprocating system (WO, Dentsply Tulsa Dental), the Twisted File Adaptive (TFA; SybronEndo, Orange, CA) rotary/reciprocating system, and the Self-Adjusting File (SAF) system (ReDent-Nova, Ra'anana, Israel). Debris extruded during the instrumentation was collected and dried in preweighed Eppendorf tubes. Three consecutive weights were obtained for each tube, and the average was calculated. The data were analyzed using the t test and analysis of variance (Games-Howell test). RESULTS: The SAF produced significantly more debris compared with the other systems (P < .05). No significant difference was noted amongst the PTN, WO, and TFA (P > .05). CONCLUSIONS: Regardless of the instrumentation system used, apical extrusion of debris was exhibited at some level, regardless of the instrumentation system used. The SAF was associated with the highest amount of debris extrusion compared with PTN, WO, and TFA.

Modern Endodontic Principles Part 3: Preparation.

The purpose of instrumentation is to facilitate irrigation and allow controlled obturation. This article will revisit methods of instrumentation of the root canal system with consideration given to length determination, apical preparation and the concept of patency filing. It will discuss hand instrumentation and rotary preparation looking at emerging technology such as reciprocating systems and the self-adjusting file. CPD/CLINICAL RELEVANCE: Mechanical preparation of the root canal system is of fundamental importance in achieving success, creating a more easily managed environment from a biological perspective.

Assessment of smear layer removal protocols in curved root canals.

This study sought to assess if the final rinse protocol interferes with the smear layer removal in the apical area of curved canals. Sixty-four extracted human mandibular molars with curved mesial roots were instrumented with rotary files and divided into six experimental groups for final rinse: 1EDTA (syringe irrigation with 1 mL of 17% ethylenediaminetetraacetic acid (EDTA) ), 5EDTA (syringe irrigation with 5 mL of 17% EDTA), 1EDTA-P (syringe irrigation with 1 mL of 17% EDTA + pumping with gutta-percha point), 5EDTA-P (syringe irrigation with 5 mL of 17% EDTA + pumping with gutta-percha point), 1EDTA-EA (syringe irrigation with 1 mL of 17% EDTA + EndoActivator) and 5EDTA-EA (syringe irrigation with 5 mL of 17% EDTA + EndoActivator). Final rinsing was carried out over 3 min. The specimens were split lengthwise and observed under a scanning electron microscope using a score criterion. Comparison among the groups showed statistically significant difference only between the 5EDTA-EA group and the other groups (Kruskal-Wallis and Dunn's post-hoc tests, P < 0.05). The combination of 5 mL of 17% EDTA and 3 mL of 2.5% sodium hypochlorite (NaOCl) with the EndoActivator removed smear layer from the apical area of curved root canals more effectively than the other protocols used.

An in vitro comparison of apically extruded debris and instrumentation times with ProTaper Universal, ProTaper Next, Twisted File Adaptive, and HyFlex instruments.

INTRODUCTION: The purpose of this study was to compare the in vitro amount of apically extruded debris with new endodontic rotary nickel-titanium instruments. METHODS: Sixty mandibular premolars were instrumented up to size 25 using ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Next (Dentsply Maillefer), Twisted File Adaptive (SybronEndo, Orange, CA), and HyFlex (Coltene-Whaledent, Allstetten, Switzerland) rotary systems. The apically extruded debris was collected and dried in preweighed Eppendorf tubes. The amount of extruded debris was assessed with an electronic balance. The total time required to complete root canal shaping with the different instruments was also recorded. The significance level was set at P = .05. RESULTS: The instrumentation time with the ProTaper Universal rotary system was significantly longer than with all the other instruments (P < .05). The Twisted File Adaptive and ProTaper Next systems extruded significantly less debris than the ProTaper Universal and HyFlex systems (P < .05). CONCLUSIONS: The ProTaper Next and Twisted File Adaptive instrumentation systems were associated with less debris extrusion compared with the ProTaper Universal and HyFlex systems.

Sealer penetration into dentinal tubules in the presence or absence of smear layer: a confocal laser scanning microscopic study.

INTRODUCTION: The aim of this study was to test the dentinal tubule penetration of AH26 (Dentsply DeTrey, Konstanz, Germany) and MTA Fillapex (Angelus, Londrina, PR, Brazil) in instrumented root canals obturated by using cold lateral compaction or warm vertical compaction techniques in either the presence or absence of the smear layer. METHODS: Forty-five extracted single-rooted human mandibular premolar teeth were used. The crowns were removed, and the root canals were instrumented by using the Self-Adjusting File (ReDent-Nova, Ra'anana, Israel) with continuous sodium hypochlorite (2.6%) irrigation. Final irrigation was either with 5% EDTA or with sodium hypochlorite. The canals were dried and obturated by using rhodamine B-labeled AH26 or MTA Fillapex in combination with the cold lateral compaction or the warm vertical compaction technique. After setting, the roots were sectioned horizontally at 4-, 8-, and 12-mm distances from the apical tip. On each section, sealer penetration in the dentinal tubules was measured by using confocal laser scanning microscopy. RESULTS: Regardless of the usage of EDTA, MTA Fillapex, compared with AH26, was associated with greater sealer penetration when used with the cold lateral compaction technique, and, conversely, AH26, compared with MTA Fillapex, was associated with greater sealer penetration when used with the warm vertical compaction technique (P < .05). Removal of the smear layer increased the penetration depth of MTA Fillapex used with the cold lateral compaction technique (P < .05); however, it had no significant effect on the penetration depth of AH26. CONCLUSIONS: Greater sealer penetration could be achieved with either the MTA Fillapex-cold lateral compaction combination or with the AH26-warm vertical compaction combination. Smear layer removal was critical for the penetration of MTA Fillapex; however, the same did not hold for AH26.

Debris remaining in the apical third of root canals after chemomechanical preparation by using sodium hypochlorite and glyde: an in vivo study.

INTRODUCTION: During chemomechanical instrumentation, several liquid or paste substances are used to ease the action of the files and to eliminate debris and the smear layer. The aim of this study was to evaluate whether the use of a paste containing EDTA during cleaning and shaping of the root canal helps to eliminate debris. METHODS: Twenty root canals in dog teeth were instrumented by a crown-down technique by using nickel-titanium rotary files. In 10 root canals (group A), sodium hypochlorite was used during instrumentation, followed by a final irrigation with 17% liquid EDTA. In another 10 canals (group B), sodium hypochlorite was again used as the irrigating solution, but Glyde File Prep paste was used with every instrument, and a final irrigation with EDTA was also carried out. Two additional teeth were used as positive and 2 as negative controls. The jaws were prepared for histologic evaluation. RESULTS: In group A where Glyde was not used during cleaning and shaping, little or no debris was found in the apical third of the instrumented root canals; however; in group B in which Glyde File Prep paste was used during chemomechanical instrumentation, moderate to high accumulation of debris was observed in the apical third. CONCLUSIONS: The use of Glyde File Prep paste during rotary mechanical instrumentation favors the accumulation of debris in the apical third of the root canals. Irrigation with NaOCl and a final flush with EDTA by means of a small-gauge needle with simultaneous aspiration led to less accumulation of debris than in the Glyde File Prep group (P < .05).

Antibacterial activity of various root canal sealers and root-end filling materials in dentin blocks infected ex vivo with Enterococcus faecalis.

OBJECTIVE: The aim was to investigate the antibacterial activity of the root-end filling materials MTA and IRM, different endodontic sealers and calcium hydroxide [Ca(OH)2] in experimentally infected dentinal tubules. MATERIALS AND METHODS: Ninety-four human root segments were prepared and the root canals were enlarged to ISO size 90. After smear removal, the specimens were infected with Enterococcus faecalis for 3 weeks. The roots were divided into eight groups and filled either with MTA, IRM, Ca(OH)2, gutta-percha and EndoRez (ER)/GuttaFlow (GF)/AH Plus (AH+) or with Resilon and Epiphany (EpRe). One group of specimens was left unfilled for control. Half of the specimens were treated for 1 day and the other half for 7 days in humid conditions at 37°C. Dentin samples from each canal were collected by enlarging the canals to ISO size 150; thus a dentinal depth of 300 µm was sampled. The number of cultivable bacteria was determined for each specimen. Statistical significance was set to 5%. RESULTS: After 1-day or 7-days of treatment, compared to control, all materials (except ER and GF at day 7) significantly reduced the number of bacteria. At day 1 and day 7, no significant difference was found between ER and GF and between Ca(OH)2, AH+, EpRe, IRM and MTA. However, a significant difference was found between these two groups of materials (except between GF and EpRe at day 7). Significantly more bacteria were cultured in the ER, GF, EpRe and IRM groups at day 7 compared to day 1. CONCLUSIONS: All materials exerted varying degrees of antibacterial activity which generally tended to decrease with time. The most stable antibacterial effect throughout the 7-day period was for Ca(OH)2, AH+ and MTA.

Comparative evaluation of canal isthmus debridement efficacy of modified EndoVac technique with different irrigation systems.

INTRODUCTION: The purpose of this study was to evaluate the canal isthmus debridement efficacy of a new modified EndoVac (Discus Dental, Culver City, CA) irrigation protocol in comparison with EndoVac, passive ultrasonic irrigation (PUI), and conventional needle irrigation in mesial roots of mandibular molars. METHODS: The mesial roots of 64 extracted mandibular molars mounted in resin using Kuttler's endodontic cube, sectioned at 2 and 4 mm from the working length, were randomly divided into 4 groups (n = 16): group 1: Max-I-Probe (Dentsply Tulsa Dental, York, PA), group 2: EndoVac (EVI), group 3: modified EndoVac, and group 4: PUI. The specimens were reassembled and instrumented. A standard irrigation protocol was used during cleaning and shaping and final irrigation with the 4 irrigation/agitation techniques. Images of the isthmus region were taken before and after cleaning and shaping and after final irrigation. The percentage reduction of debris in the isthmus region was calculated by using the software program Image J (v1.43; National Institutes of Health, Bethesda, MD). Intergroup analysis was performed using the Kruskal Wallis and Mann-Whitney U tests. Intragroup analysis was performed using Friedman and Wilcoxon signed rank tests. The level of significance was set at P < .05. RESULTS: Intragroup analysis revealed a statistically significant difference in the percentage reduction of debris after cleaning and shaping and after final irrigation protocol in all the groups (P < .001). The final irrigation protocol produced significantly cleaner canal isthmuses in all the groups (P < .001). On intergroup analysis, the modified EVI group performed significantly better than the other groups. The EVI and PUI groups performed better than the Max-I-Probe group. There was no statistical significance between the EVI and PUI groups. CONCLUSIONS: Canal isthmuses were significantly cleaner with the modified EndoVac irrigation technique when compared with the cleanliness seen with the other irrigation systems.

Effects of different sonic activation protocols on debridement efficacy in teeth with single-rooted canals.

OBJECTIVES: The effects of different EndoActivator® (EA) sonic activation protocols on root canal debridement efficacy were examined. METHODS: Root canals in 48 single-rooted teeth were instrumented, irrigated initially with NaOCl and divided into 6 groups (N=8) based on the application time of QMix (antimicrobial calcium-chelating irrigant), and the time and sequence of EA irrigant activation - Positive Control: 90s QMix; Negative Control: 90s saline; Group 1A: 15s QMix+15s QMix with EA-activation; Group 1B: 30s QMix+30s of QMix with EA-activation; Group 2A: 15s QMix with EA-activation+15s QMix; Group 2B: 30s QMix with EA-activation+30s QMix. Split roots were examined with scanning electron microscopy for assignment of smear and debris scores in locations along the coronal, middle and apical thirds of the canals. The overall cleanliness of pooled canal locations in the Positive Control and the 4 experimental groups were compared with chi-square tests. RESULTS: Significant differences were detected among the 5 groups (P<0.001). Post hoc pairwise comparisons indicated that the overall canal cleanliness was in the order (from best to worst): 1B=2B>2A>1A>Positive Control. Completely clean canals could not be achieved due to the absence of continuous irrigant flow for EA to clear intraradicular debris. CONCLUSIONS: Irrespective of the sonic activation sequence, irrigant activation for 30s during a 60-s period of QMix application appears to maximise the smear layer and debris removal potential of the EndoActivator® system. CLINICAL SIGNIFICANCE: Sonic activation of root canal irrigants produces cleaner root canals and reduces the time required for final delivery of a canal wall smear later-removing irrigant when compared to the use of needle irrigation alone.