An ex vivo evaluation of a new root canal irrigation technique with intracanal aspiration

AIM: To evaluate the effectiveness of a new root canal irrigation technique with intracanal aspiration in removing the smear layer and to assess irrigant extrusion ex vivo. METHODOLOGY: Thirty-five instrumented canals of extracted human canine teeth that had been resected apically by removing 3 mm of the root tip were divided into one control and four experimental groups of seven teeth each. The roots were fixed in a plastic case and surrounded with normal saline agar coloured with 1% acid red. No irrigation was performed in the control teeth. Each root canal in the experimental groups was irrigated with 9 mL of 14% ethylenediaminetetraacetic acid for 3 min, and then with 6 mL of 6% sodium hypochlorite (NaOCl) for 2 min. In the intracanal aspiration technique, the irrigant was delivered from the tip of an injection needle placed 12 mm from the apical root-end and an aspiration needle that was connected to a Root ZX apex locator placed 2 and 3 mm short of the apical root-end in groups 1 and 2, respectively. In the conventional method, the tip of an injection needle used for delivery of the irrigant and as an active electrode was placed 2 and 3 mm short of the apical root-end in groups 3 and 4, respectively, the tip of the aspiration needle was placed 12 mm from the apical root-end in these groups. The readings of the Root ZX during irrigation were recorded. The cleanliness of the canal was evaluated by scoring smear layer from scanning electron microscopy (SEM) images of the canal. Extrusion of NaOCl was detected by measuring the discoloured area of the agar around the apical root-end. The data obtained were statistically analysed by one-way anova, the Kruskal-Wallis test and Friedman's test. RESULTS: In the SEM study, the canals in groups 1-3 were significantly cleaner than those in the control and group 4 (P < 0.05). The mean Root ZX readings in groups 1-3 were approximately "0.5". The discoloured area in group 3 was significantly larger than the other groups (P < 0.05). CONCLUSIONS: Irrigation using the intracanal aspiration technique allowed more effective removal of the smear layer than that performed by the conventional method in an apically resected canine tooth. The intracanal aspiration technique produced limited extrusion of the irrigant beyond the apical foramen.     

Debris and irrigant extrusion potential of 2 rotary systems and irrigation needles

The purpose of this study was to compare the amount of apically extruded irrigant using 2 Ni-Ti rotary systems. Forty mandibular premolars with single canals were randomly assigned into 4 groups. Flower arrangement foam cubes were weighed with a precision balance before being attached to the apical portions of all teeth. In group 1, preparation was completed with ProTaper files. In group 2 canals were prepared with RaCe files. In groups 1 and 2, the irrigant was delivered with a 30-gauge conventional dental needle. In groups 3 and 4, teeth were prepared as in groups 1 and 2 with the exception that the irrigant was delivered with a side-vented irrigation needle. The weight of the extruded material (irrigant and debris) for each group was calculated by comparing the pre- and postinstrumentation weights of the foams used for periapical modeling. Obtained data were analyzed by Kruskal-Wallis and Mann-Whitney U tests, with P equals .05 as the level for statistical significance. ProTaper files used with regular needle irrigation had the highest fluid extrusion. The lowest irrigant extrusion was observed with the RaCe system combined with a side-vented irrigation needle. Within the limitations of this study, it can be concluded that irrigation needle and rotary instruments have an effect on the amount of extruded root canal irrigant.     

Comparative Safety of Various Intracanal Irrigation Systems

The objective of this project was to evaluate the safety of various intracanal irrigation systems by measuring the apical extrusion of irrigant. Twenty-two single canal, extracted mature teeth were instrumented and secured through the lid of a scintillation vial to collect apically extruded irrigant. A precision syringe pump delivered controlled amounts of irrigant at a constant flow. The irrigation systems used were EndoVac Micro and Macro Cannula, EndoActivator, manual irrigation with Max-I-Probe needle, Ultrasonic Needle Irrigation, and Rinsendo. Results were analyzed by using one-way analysis of variance with Scheffé test (P < .05). The EndoVac Micro and Macro cannulae groups did not extrude irrigant, and there was no statistically significant difference between these 2 groups and the EndoActivator group. Within the groups that produced extrusion, EndoActivator extruded statistically significantly less irrigant than Manual, Ultrasonic, and Reinsendo groups. There was no statistically significant difference among Manual, Ultrasonic, and Rinsendo groups. This study showed that the EndoVac did not extrude irrigant after deep intracanal delivery and suctioning the irrigant from the chamber to full working length. EndoActivator had a minimal, although statistically insignificant, amount of irrigant extruded out of the apex when delivering irrigant into the pulp chamber and placing the tip into the canal and initiating the sonic energy of the EndoActivator. Manual, Ultrasonic, and Rinsendo groups had significantly greater amount of extrusion compared with EndoVac and EndoActivator.     

不同根管预备方法对根尖孔溢出碎屑和液体的影响

目的 比较手用不锈钢K挫，手用镍仗挫和机用不锈钢K锉，机用镍钛锉行根管预备后，推出根尖孔的牙本质碎屑重量和冲洗液的体积。方法 将80颗单根离体牙分为4组，每组20颗，分别用手用不锈钢K锉，手用镍钛锉，机用不锈钢K锉，机用镍钛锉预备根管。预备过程中从根尖孔推出的牙本质碎屑和液体，用预先称重的离心管收集，测得推出根尖孔的液体体积和牙本质碎屑的重量。结果 机用镍钛锉组推出根尖孔的牙本质碎屑量比其他组少，但四组间无显著性差异。机用镍钛锉组推出根尖孔的液体量较少，四组间有显著性差异。结论 机用镍钛锉用于根管预备推出根尖孔的液体量及牙本质碎屑均较少。     

根尖止点阻止根充材料超充的效果研究

目的:研究根管治疗中制备根尖止点对阻止根管充填材料超充的影响。方法:选取80个单根管上、下颌尖牙,其中40个牙采用逐步后退技术,常规制备根尖止点进行根管预备至根尖孔上1mm,另40个牙亦采用逐步后退技术预备至根尖孔,不进行根尖止点的制备;再将以上各组牙随机平分为两组,分别采用冷牙胶侧方加压和热牙胶垂直加压方法充填根管,观察并记录每组中牙胶超出根尖的牙数,收集每个牙超出的充填材料(牙胶和糊剂)并称量,对实验结果进行统计学分析。结果:制备根尖止点的侧方加压组与不制备根尖止点的侧方加压组之间根充材料超出的量、制备根尖止点的垂直加压组与不制备根尖止点的垂直加压组之间根充材料超出的量均无统计学差异(P>0.05)。结论:通过在初尖锉的基础上扩大3#的方法制备根尖止点并不一定能起到减少根充材料超充的作用。     

Apical extrusion of debris and irrigants using two hand and three engine-driven instrumentation techniques

AIM: To evaluate the weight of debris and irrigant volume extruded apically from extracted teeth in vitro after endodontic instrumentation using the balanced force technique, a hybrid hand instrumentation technique, and three engine-driven techniques utilizing nickel-titanium instruments (ProFile .04, Quantec 2000 and Pow-R). METHODOLOGY: Five groups of 20 extracted human teeth with single canals were instrumented using one or other of five techniques: balanced force, hybrid, Quantec 2000, ProFile .04, or Pow-R. Debris extruded from the apical foramen during instrumentation were collected into preweighed 1.5 mL tubes. Following instrumentation, the volume of extruded irrigant fluid was determined by visual comparison to control centrifuge tubes filled with 0.25 mL increments of distilled water. The weight of dry extruded dentine debris was also established. RESULTS: Overall, the engine-driven techniques extruded less debris than the manual ones. However, there was no statistical difference between the balanced force technique and the engine-driven methods. The volume of irrigant extruded through the apex was directly associated with the weight of extruded debris, except within the ProFile group. The hybrid technique was associated with the greatest extrusion of both debris and irrigant. CONCLUSIONS: Overall, the engine-driven nickel-titanium systems were associated with less apical extrusion.     

Intracanal aspiration technique for root canal irrigation: evaluation of smear layer removal

A new irrigation technique (intracanal aspiration technique, IAT) was developed to minimize the extrusion of root canal irrigant. Fifteen instrumented canals of extracted canines were divided into one control and four experimental groups of 3 teeth each. Each root was fixed in a case and surrounded with colored saline agar to measure the meter value of the Root ZX and to evaluate the extrusion of the irrigant. In control teeth, no irrigation was performed. In Groups 1 and 2, the root canal was irrigated using IAT with an aspiration needle placed 2 or 3 mm short of the apex. In Groups 3 and 4, the root canal was irrigated in a conventional manner with a washing needle placed 2 or 3 mm short of the apex. The file folder of a Root ZX was attached to the aspiration needle in Groups 1 and 2, and to a washing needle in Groups 3 and 4. Each canal was irrigated with 9 ml of 14% EDTA solution and 6 ml of 6% NaClO in experimental groups, and the meter value of the Root ZX during irrigation was recorded. After the irrigation, cleanliness of the canal was evaluated using a SEM and extrusion of NaClO by discoloration of the agar. Irrigation using IAT was more effective for removing smear layer compared to the conventional method and extrusion of the irrigant was minimized. In addition, the Root ZX measurement during IAT could monitor the extent of the irrigant in the apical canal.     

An in vitro experiment on the effect of an attempt to create an apical matrix during root canal preparation on coronal leakage and material extrusion

OBJECTIVE: A common approach to creating an apical matrix (apical stop) in the apical dentin is to enlarge the root canal to 3 sizes greater than that of the first file that binds at the working length. The aim of this study was to test the hypothesis that this procedure will reduce the amount of material extruded and the leakage along the apical root fillings. STUDY DESIGN: The canals of half of 120 maxillary and mandibular canines were prepared to the apical foramen through use of the serial shaping technique; the apical matrix creation procedure was not used. Each of the other 60 canals was prepared to 1 mm short of the apical foramen, and the canal was enlarged to at least 3 sizes greater than that of the first binding file to create an apical matrix. All the canals prepared with and all the canals prepared without the apical matrix creation procedure were obturated with laterally or vertically compacted cold or warm gutta-percha. In the leakage test, after post space preparation, the amount of fluid transport along the apical root fillings was measured. In the material extrusion test, the number of teeth with gutta-percha extrusion was recorded and the weight of the apically extruded materials was measured. RESULTS: In both the leakage and the extrusion tests, no significant difference was found between canals prepared with and canals prepared without the apical matrix creation procedure. CONCLUSION: The hypothesis that a procedure to enlarge root canals to 3 sizes greater than that of the first binding file will reduce the amount of filling materials extruded and the leakage was not proved, as our results show.     

A laboratory study of root fillings in teeth obturated by lateral condensation of gutta-percha or Thermafil obturators

The aim of this in vitro study was to assess the quality of root canal obturation and degree of apical dye penetration in teeth root-filled with either laterally condensed cold gutta-percha or Thermafil obturators. A total of 144 extracted teeth with single roots were included in the study. All canals were prepared with a standard technique using a sonic handpiece with copious irrigation. Radiographs taken of the teeth to show the maximum degree of canal curvature were then exposed and the angle, radius and position of curvature determined. This information about the canals, together with their working length and diameter at end-point was used to divide the teeth into two experimental and two control groups. A total of 71 teeth were filled with Thermafil obturators, 69 with lateral condensation while four teeth remained unfilled and acted as controls. Following obturation, the teeth were radiographed in two planes and the technical quality of fill assessed on a four-point scale. All access cavities were then sealed and the teeth immersed in dye for 48 h before being split longitudinally. Linear dye penetration via the apical foramen was then assessed. In both straight and curved canals obturation with Thermafil obturators was significantly quicker (P< 0.001) than lateral condensation. Apical extrusion of gutta-percha occurred significantly more often in straight canals obturated with lateral condensation (P< 0.005) but there was no difference in curved canals. There was little difference in the radiographic quality of fill in the apical halves of the root fillings but Thermafil obturators were significantly better in the coronal halves when viewed from the proximal. Apical leakage of dye was significantly worse (P< 0.05) in curved canals filled with lateral condensation with a similar, but not significant, trend in straight canals. Under the conditions of this study, Thermafil obturators proved a satisfactor alternatie to lateral condensation of gutta-perch.     

Apical extrusion of intracanal bacteria following use of various instrumentation techniques

Aim To evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using a manual technique and three engine‐driven techniques utilizing nickel–titanium instruments (K3, RaCe, and FlexMaster). Methodology Seventy extracted human mandibular premolar teeth with similar dimensions were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and then dried. The contaminated roots were divided into four experimental groups of 15 teeth each and one control group of 10 teeth. G1. RaCe group: the root canals were instrumented using RaCe instruments. G2. K3 group: the root canals were instrumented using K3 instruments. G3. FlexMaster group: the root canals were instrumented using FlexMaster instruments. G4. Manual technique group: the root canals were instrumented using K‐type stainless steel instruments. G5. Control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The resultant microbiological samples were removed from the vials and then incubated in culture media for 24 h. The number of colony‐forming units (CFU) was determined for each sample. The data obtained were analysed using the Kruskal–Wallis one‐way analysis of variance and Mann–Whitney U‐tests, with α = 0.05 as the level for statistical significance. Results There was a significant difference between experimental‐control and engine‐driven‐manual technique groups (P < 0.05). The manual technique was associated with the greatest extrusion of microorganism. Conclusions All instrumentation techniques extruded intracanal bacteria apically. No significant difference was found in the number of CFU among the engine‐driven techniques; manual techniques extruded significantly more microorganisms.     

A preliminary study of the percentage of gutta-percha-filled area in the apical canal filled with vertically compacted warm gutta-percha

AIM: The aim of this study was to determine the influence of the width of apical root canals and the depth of heat application during warm vertical compaction on the percentage of gutta-percha-filled area (PGFA) in the apical root canal. METHODOLOGY: Two groups of extracted human canines (total 60) were instrumented and filled with vertically compacted warm gutta-percha up to the apical foramen (AF). Using the Touch 'n Heat device heat was applied 4 mm from the AP in one group and 2 mm in the other. The number of teeth with gutta-percha extrusion was recorded. A horizontal section was cut 1.5 mm from the AF of each tooth. The cross-sectional area of the canal and the gutta-percha was measured using an image-analysis programme. The PGFA was then calculated. Multiple linear regression was performed to investigate the association between the experimental variables and the PGFA, and the occurrence of gutta-percha extrusion. RESULTS: A significant association was seen between the depth of heat application and the PGFA (P= 0.000), and between the canal area and the PGFA (P= 0.038). The average PGFA reached 96.1% when heated to 2 mm, as compared with 87.0% when heated to 4 mm. PGFAs were lower in wide apical canals than in small canals. Gutta-percha extruded in seven teeth (12%) and was independent of experimental variables. CONCLUSIONS: After warm vertical compaction, the quality of adaptation of gutta-percha to the wall of the apical root canal varies; the influencing factors in this study were the depth of heat application and the width of the apical root canal.     

Influence of foraminal enlargement on the apical extrusion of filling material: Volumetric analysis using micro‐computed tomography

The aim of this study was to compare the root canal instrumentation techniques that involve foraminal enlargement versus those not involving it, in regard to the apical extrusion of filling material, using micro‐computed tomography (micro‐CT). Twenty‐two premolars with single canals were instrumented using the ProTaper Universal System and then randomly divided into two groups (n = 11): Group NFE, without foraminal enlargement, and Group FE, with foraminal enlargement. Instrumentation was performed up to 1 mm short of the apical foramen, and foraminal patency was maintained at each instrument change in both groups. Prior to obturation, the apical portion of the specimens was wrapped in adhesive paper to ensure complete separation between apex and extruded material. The canals were filled according to the continuous wave of condensation technique. The apically extruded material was collected and measured using micro‐CT. Extrusion in Group FE was significantly higher than in Group NFE (0.928 mm³ vs. 0.148 mm³; P < 0.001).     

Deviations of Mesial Root Canals of Mandibular First Molar Teeth at the Apical Third: A Micro–computed Tomographic Study

Introduction

The present study aimed to quantitatively analyze apical foramen deviations of mesial root canals of mandibular first molar teeth by means of micro–computed tomographic (micro-CT) imaging.

Spectrophotometric Determination of Irrigant Extrusion Using Passive Ultrasonic Irrigation,EndoActivator, or Syringe Irrigation

Introduction

Sodium hypochlorite (NaOCl) irrigation is critical to endodontic success, and several new methods have been developed to improve irrigation efficacy (eg, passive ultrasonic irrigation [PUI] and EndoActivator [EA]). Using a novel spectrophotometric method, this study evaluated NaOCl irrigant extrusion during canal irrigation.

Methods

One hundred fourteen single-rooted extracted teeth were decoronated to leave 15 mm of the root length for each tooth. Cleaning and shaping of the teeth were completed using standardized hand and rotary instrumentation to an apical file size #40/0.04 taper. Roots were sealed (not apex), and 54 straight roots (n = 18/group) and 60 curved roots (>20° curvature, n = 20/group) were included. Teeth were irrigated with 5.25% NaOCl by 1 of 3 methods: passive irrigation with needle, PUI, or EA irrigation. Extrusion of NaOCl was evaluated using a pH indicator and a spectrophotometer. Standard curves were prepared with known amounts of irrigant to quantify amounts in unknown samples.

Results

Irrigant extrusion was minimal with all methods, with most teeth showing no NaOCl extrusion in straight or curved roots. Minor NaOCl extrusion (1–3 μL) in straight roots or curved roots occurred in 10%–11% of teeth in all 3 irrigant methods. Two teeth in both the syringe irrigation and the EA group extruded 3–10 μL of NaOCl.

Conclusions

The spectrophotometric method used in this study proved to be very sensitive while providing quantification of the irrigant levels extruded. Using the PUI or EA tip to within 1 mm of the working length appears to be fairly safe, but apical anatomy can vary in teeth to allow extrusion of irrigant.     

Apically-extruded debris using the ProTaper system

The purpose of this in vitro study was to determine the quantity of debris and irrigant extruded apically using the ProTaper system compared to ProFiles and K-Flexofiles. Thirty-six mesio-buccal root canals of human mandibular molars were selected and divided into three groups of twelve canals. Two groups were instrumented with ProFiles and ProTapers according to the manufacturer's instructions. The other group was instrumented with K-Flexofiles using the step-back technique. A standard amount of irrigant was used for each canal. Apically-extruded debris and irrigant was collected in pre-weighed vials. The mean weight of extruded debris and irrigant for each group was statistically analysed using Student's t-test and one-way ANOVA. All instrumentation techniques produced extruded debris and irrigant. Although the mean amount of extrusion with the step-back technique was higher than the two rotary systems, there was no significant difference between the three groups (p > 0.05). NiTi rotary systems were associated with less apical extrusion, but were not significantly better than hand file instrumentation. All techniques extruded debris.     

Influence of irrigant needle depth in removing bioluminescent bacteria inoculated into instrumented root canals using real-time imaging in vitro

AIM: To test the hypothesis that the mechanical efficacy of irrigation in reducing bacteria in the root canal is dependent on depth of placement of the irrigation needle. METHODOLOGY: The root canals of 30 permanent cuspids were instrumented to apical size 60 using a crown-down technique. A suspension of the bioluminescent reporter strain Pseudomonas fluorescens 5RL was inoculated into each canal of sterilized teeth. Emission of bioluminescence (photons s(-1)) from each tooth was quantified on four sequential occasions using luminometry and bioluminescence imaging: (i) background, (ii) after inoculation, (iii) after irrigating the inoculated teeth with 3 mL of a nonantimicrobial irrigant delivered either 1 mm (group 1, n = 15) or 5 mm (group 2, n = 15) from working length (WL) using a 28G safety-ended irrigating needle, (iv) after an additional 3 mL irrigation (total 6 mL). Intragroup and intergroup comparisons were made using Wilcoxon matched pairs and Mann-Whitney tests, respectively. RESULTS: In group 1, there was a mean log10 decrease in bacteria of 0.68 +/- 0.26 after 3 mL of irrigant compared with 1.19 +/- 0.48 after 6 mL (P < 0.001); in group 2 the mean log10 decrease was 0.58 +/- 0.28 after 3 mL of irrigant compared with 0.69 +/- 0.35 after 6 mL (P < 0.02) (Wilcoxon matched pairs). Using 3 mL of irrigant, needle depth did not have a significant effect on reduction of intracanal bacteria (P = 0.407), but the effect became significant when 6 mL of irrigant was used (P < 0.002) (Mann-Whitney tests). CONCLUSIONS: The mechanical efficacy of 6 mL of irrigant in reducing intracanal bacteria was significantly greater when delivered 1 mm compared with 5 mm from WL.     

Dynamic recording of irrigating fluid distribution in root canals using thermal image analysis

AIM: To investigate the influence of the size and the depth of insertion of irrigating needles, and the diameter of the master apical file on flow distribution during fluid irrigation in root canals. METHODOLOGY: Stepback canal instrumentation was employed on seven extracted human single canal teeth. The size of the master apical files ranged from sizes 25, 30, 35, 40, 45, 50 to size 80 within the seven teeth, respectively. A thermal imaging system (ThermaCAM; National Instruments Co., Austin, TX, USA) was used to record the dynamic fluid distribution following root canal preparation. The dynamic fluid distribution was analysed during irrigation by insertion of different irrigating needle tips (23, 25 and 27 gauge) at various depths (3, 6 and 9 mm) from the root apex. The whole process of irrigation was recorded by a video camera and analysed by two observers separately. The success of the irrigation process was defined when the irrigant was able to flow into to the apical region immediately after injection. RESULTS: The aqueous irrigant was flushed into the apical region when a size 27 gauge irrigating needle was placed into a size 30 canal at a point 3 mm from the apical stop. When the same needle tip was placed 6 mm from the root canal apex, successful irrigation was achieved only in the canals prepared to size 50 or larger. When a size 25 gauge irrigating needle was placed 3 mm from the working length, the canal size had to be no <45 to allow for successful irrigation. When a size 23 gauge needle was placed at the same position, the canal needed to be prepared to size 50 to allow thorough irrigation of the apex. At 9 mm from the apical stop, none of the irrigating needles could achieve successful irrigation of any canal size. CONCLUSION: The flow distribution of root canal irrigation can be affected adversely by large diameter irrigating needles, by greater distances between the needle tip and the apical stop, and by narrow root canals.     

The effect of maintaining apical patency on periapical extrusion.

Thirty-three human maxillary incisors were secured in the openings of a glass vial. Root canals were instrumented to the apical constriction with a step-back technique and a patency file was not used throughout the root canal preparation. The irrigant, 1% NaOCl, was delivered by means of a plastic syringe with a 23-gauge needle and the overflow was suctioned with an aspirator. The total volume of irrigant used was 10 ml. Apically extruded debris and NaOCl were measured. The apical constriction was then deliberately enlarged. With a step-back technique a new 'apical constriction' was created, coronally to the original one. A patency file was again not used, and irrigation was identical to the that used during the initial root canal preparation. Extruded debris and NaOCl in each bottle were again measured. Results indicated that there was significant difference in the amounts of extruded material before and after the enlargement of the apical constriction with greater extrusion when the constriction remained intact.     

Does apical negative pressure prevent the apical extrusion of debris and irrigant compared with conventional irrigation? A systematic review and meta‐analysis

The aim of this study was to evaluate if apical negative pressure (ANP) irrigation prevents the apical extrusion of debris and irrigant compared with conventional needle irrigation through a systematic review and meta‐analysis. A computer search of dental literature was performed using four different databases. A combination of the terms ‘apical negative pressure’, ‘endovac’, ‘apical extrusion’, ‘extrusion’ and ‘endodontics’ was used. Studies that used extracted human teeth with a mature apex and that evaluated the apical extrusion of debris and/or irrigating solution were included. After an evaluation of the full studies according to the eligibility criteria, eight studies were critically analysed and subjected to quality assessment and risk of bias. Only four studies that evaluated extrusion of irrigant were considered as having high methodological quality and were subjected to a meta‐analysis. Studies evaluating extrusion of debris did not have sufficient methodological quality to be subjected to the meta‐analysis. The forest plot indicated that ANP irrigation prevents the risk of irrigant extrusion compared with conventional irrigation (OR 0.07 [95%CI 0.02–0.20]; P < 0.00001). This systematic review and meta‐analysis showed that ANP prevents the apical extrusion of irrigant. There is no evidence if this type of irrigation prevents the extrusion of debris.     

Efficacy of smear layer removal at the root tip by using ethylenediaminetetraacetic acid and erbium, chromium: yttrium, scandium, gallium garnet laser

Introduction

The purpose of this study was to compare the efficacy of laser-driven irrigation in removing the smear layer and debriding the apical region of the root canal (the root tip) with that of ultrasonic irrigation.

Methods

Forty extracted human teeth with straight single roots were randomized into 4 groups (n = 10). The specimens were shaped by using hand instruments up to a size 30/.02 file (Control, Laser 1, and Laser 2 groups) or a size 20/.02 file (Laser 3 group). During instrumentation, each canal was irrigated with 3% NaOCl and 17% ethylenediaminetetraacetic acid alternately between the use of successive files. The 4 groups of 10 teeth were processed as follows. In the Control group, teeth were irrigated with 17% ethylenediaminetetraacetic acid, and the irrigant was activated with an ultrasonic device for 60 seconds. In the Laser 1 and Laser 3 groups, the irrigant was activated with the laser for 60 seconds. In the Laser 2 group, the irrigant was activated with the laser for 30 seconds.

Results

There were significant differences between the smear layer and debris scores for the Laser 1 group and those for the Control (P < .001), Laser 2 (P = .002), and Laser 3 groups (P = .012 and P = .013, respectively). Completely clean root canals were found in the Laser 1 group.

Conclusions

Use of a laser with a plain fiber tip, which produces cavitation in the irrigant, has potential as an improved alternative method for removing of the smear layer from the apical region of a straight root canal.