Isthmus Cleanliness Research Articles

Effect of Chemical Debridement and Irrigant Activation on Endodontic Treatment Outcomes: An Updated Overview.

Chemical debridement is considered one of the most important steps during root canal treatment to target unreached areas and provide thorough disinfection of the canals. The efficiency of this step efficiency can be increased using different agitation and irrigation techniques/devices. This comprehensive review aimed to summarize the effect of various irrigant activation and agitation techniques/devices on endodontic treatment outcomes. Using mechanical active irrigation, which enables the activation or agitation of the irrigating solution, is beneficial in root canal treatment by increasing the efficiency of delivering the irrigant up to working length and ensuring isthmus cleanliness. However, considerable variation was noticed between the protocols used in each technique with a lack of well-designed randomized clinical trials to focus on the long-term outcome. Moreover, a low level of evidence was noticed regarding the effectiveness of certain activation techniques over others. Therefore, each study needs to be carefully weighed before using its results and embracing its conclusion. Future studies need to focus more on the antimicrobial effect of each technique and its effect on the healing of apical periodontitis. Also, recent advances, such as multisonic and laser activation, are promising tools that need more clinical investigations to show their efficiency.

Comparative evaluation of the efficacy of diode laser, EndoActivator, passive ultrasonic irrigant, and manual irrigation activation systems in debridement of root canal isthmus

Objective: This study aimed to compare the efficacy of diode laser, EndoActivator, passive ultrasonic irrigation (PUI), and manual dynamic activation (MDA) in the debridement of root canal isthmus using a stereomicroscope. Materials and Methods: A total of 65 extracted mandibular first molars were selected for the study. The access cavity preparation was done and the working length was determined. All teeth were prepared using ProTaper rotary system up to F2. The samples were randomly divided into five groups (n = 13) used in the study. Group 1: Diode laser (n = 13): samples were irrigated using a diode laser having a wavelength of 980 nm. Group 2: EndoActivator (n = 13): the samples were irrigated using EndoActivator sonic device. Group 3: PUI (n = 13): samples were irrigated using an ultrasonic device. Group 4: MDA (n = 13): samples were irrigated manually by placing a master gutta-percha cone of F2 size. Group 5: Conventional needle irrigation (n = 13): no activation of irrigant. Following irrigant activation, the mesial roots were sectioned 4 mm from the apex and the isthmus cleanliness was observed under a stereomicroscope at ×20. Statistical analysis was done using ANOVA and post hoc Tukey's test. Results: EndoActivator showed the least amount of debris when compared to diode laser, passive ultrasonic irrigant, and MDA. MDA showed more amount of debris at the isthmus level. Conclusion: EndoActivator showed the least amount of debris at the isthmus level of mandibular molars when compared to diode laser, passive ultrasonic irrigant, and MDA.

A Comparative Assessment of Three Different Irrigating Systems in Root Canal Treatment: An In vitro Study.

Background:Exact diagnosis, efficient cleaning, shaping as well as disinfection of the root canals lead to successful root canal treatment. The present study compared three different irrigating systems in root canal treatment.Methodology:Sixty recently extracted permanent mandibular molars were classified into four groups: Group I, II, III, and IV with 15 teeth each. Group I comprised Endo-Irrigator Plus system. Group II comprised EndoActivator, Group III utilized passive ultrasonic irrigation (PUI), and Group IV was control, in which no activation of the irrigant was done. Stereomicroscope (X20) magnification was used for checking isthmus cleanliness. The scoring criteria were divided into score 1–5 depending on the amount of debris in root canal walls.Results:The mean ± standard deviation debris removal score in Group I was 2.6 ± 0.80, in Group II was 3.8 ± 0.72, in Group III was 3.9 ± 1.06, and in Group IV was 4.2 ± 0.82. The difference was significant (P < 0.05).Conclusion:Authors found that Endo-Irrigator Plus exhibited better cleaning efficacy followed by EndoActivator and PUI.

Activated Irrigation vs. Conventional non-activated Irrigation in Endodontics - A Systematic Review.

Objective:Irrigant activation has been claimed to be beneficial in in vitro and clinical studies. This systematic review aims to investigate the clinical efficiency of mechanically activated irrigants and conventional irrigation.Methods:A literature search (PROSPERO registration number: CRD42018112595) was undertaken in PubMed, Cochrane and hand search. The inclusion criteria were clinical trials, in vivo/ex vivo on adult permanent teeth involving an active irrigation device and a control group of conventional irrigation. The exclusion criteria were studies done in vitro, animals and foreign language. Adult patients requiring endodontic treatment of permanent dentition and irrigant activation during the treatment were chosen as the participants and intervention respectively.Results:After removal of duplicates, 89 articles were obtained, and 72 were excluded as they did not meet the selection criteria. 6 devices (EndoVac, EndoActivator, Ultrasonic, MDA (manual dynamic agitation), CUI (Continuous Ultrasonic Irrigation) and PUI (Passive Ultrasonic Irrigation)) and 6 variables of interest (Post-operative pain, periapical healing, antibacterial efficacy, canal and/or isthmus cleanliness, debridement efficacy and delivery up to working length) were evaluated in the 17 included articles. The risk of bias and quality of the selected articles were moderate. Results showed that mechanical active irrigation reduces post-operative pain. It improved debridement, canal/isthmus cleanliness. It also improved delivery of irrigant up to working length. Bacterial count was more with active irrigation, though not significant. There is no effect on long-term periapical healing.Conclusion:It may be concluded that mechanical active irrigation devices are beneficial in reducing post-operative pain and improving canal and isthmus cleanliness during Endodontics.

Debris Removal from the Mesial Root Canal System of Mandibular Molars with Laser-activated Irrigation

IntroductionThe purpose of this study was to compare in vitro the canal and isthmus debridement of manual-dynamic, passive ultrasonic, and laser-activated irrigation with an Er:YAG laser in mesial roots of human mandibular molars. MethodsFifty extracted mandibular molars with an isthmus were embedded in resin and sectioned axially 4 mm from the apex. The teeth were reassembled with guide pins and bolts, and the mesial canals were instrumented up to a ProTaper F2 rotary file (Dentsply Maillefer, Ballaigues, Switzerland). Teeth were randomly assigned to the following irrigant activation groups (n = 10): conventional needle irrigation (NI), manual-dynamic irrigation with a ProTaper F2 gutta-percha cone, ultrasonically activated irrigation using a size 20 Irrisafe (Satelec Acteon, Mérignac, France), and laser-activated irrigation (LAI) with an Er:YAG laser and a conical 400-μm fiber tip in the canal entrance or a 600-μm tip over the canal entrance. Root cross-sectional images were taken before and after final irrigation, and the area occupied by debris in the main canal and the isthmus was determined using image analysis software. Differences in debris before and after activation were statistically compared within and across groups. ResultsSignificant reductions in debris levels were observed in all groups, except for NI and manual-dynamic irrigation (canal only). None of the methods rendered the canal systems debris free. In the canal, LAI with an Er:YAG laser and a 600-μm tip over the canal entrance removed significantly more debris than NI. In the isthmus, LAI with an Er:YAG laser and a conical 400-μm fiber tip in the canal entrance removed significantly more debris than NI. ConclusionsWithin the limitations of this in vitro study, canal and isthmus cleanliness significantly improved after irrigant activation.

Comparative evaluation of the efficacy of three different irrigation devices in removal of debris from isthmus: An in vitro study

Aim: To evaluate the cleaning efficacy of endoactivator, EndoVac (EV), and self-adjusting file (SAF) as irrigant adjunct in the removal of debris from isthmus. Materials and Methods: Forty extracted human mandibular molars were taken. Canals were prepared up to F4 protaper file. Irrigation after each file size was done by 1 ml normal saline. Final irrigation was done by 4 ml of 5% NaOCl and activated in each canal for 1 min with different activating systems. Teeth were divided randomly into 4 groups according to activation system as manual activation (control group, n = 10), Group 2 SAF system (n = 10), Group 3 endoactivator (n = 10), and Group 4 EV (n = 10). After activation final flush was done with 1 ml saline. The mesial root of each tooth was sectioned and checked for isthmus cleanliness by stereomicroscopic analysis. Images were analyzed by ImageJ software. Percentage of debris remaining in each group was calculated. Results: There is no statistically significant difference in cleaning efficacy of endoactivator, EV, and SAF systems. Conclusion: All three techniques remove debris from isthmus area more efficiently than manual dynamic activation.

A comparison of the cleaning efficacy of ProRinse® syringe needle, ProUltra® PiezoFlow TM , and EndoActivator® irrigation techniques using software program ImageJ

The purpose of this ex vivo study was to evaluate the efficacy of three different irrigation techniques, ProRinse® syringe needle, ProUltra® PiezoFlow TM , and EndoActivator®, in cleaning the canals and isthmuses of human mandibular molars using a software program ImageJ. Materials and Methods : A custom-made metal cube was used to create a sealed canal system. Eighty extracted mandibular molars were randomly divided into four equal groups. Teeth were mounted; sectioned at 2, 4, and 6 mm; and reassembled into the metal cube. Chemo-mechanical preparation was done for all teeth. The teeth were divided into four groups for final debridement: Group 1 (control group) received only needle irrigation, group 2 used the ProRinse® syringe needle with 5% NaOCl irrigation within a 1-mm working length, group 3 used ProUltra® PiezoFlow TM ultrasonic agitation for 30 seconds, and group 4 used the EndoActivator® system to agitate for 30 seconds. All groups received a final irrigation with 5% NaOCl in each canal. Specimens were evaluated by digital image capture with a stereomicroscope. Statistical analysis was completed using an ANOVA test and Tukey's test. Results: The results showed no statistically significant difference in canal or isthmus cleanliness between the four groups. However, there was a statistically significant difference (P < 0.05) in isthmus cleanliness in group 4 at the 4-mm level. Conclusions: EndoActivator® produced a good result in isthmus cleaning at the 4-mm level.

Multivariate analysis of the cleaning efficacy of different final irrigation techniques in the canal and isthmus of mandibular posterior teeth

ObjectivesThe aim of this study was to compare the cleaning efficacy of different final irrigation regimens in canal and isthmus of mandibular molars, and to evaluate the influence of related variables on cleaning efficacy of the irrigation systems.Materials and MethodsMesial root canals from 60 mandibular molars were prepared and divided into 4 experimental groups according to the final irrigation technique: Group C, syringe irrigation; Group U, ultrasonics activation; Group SC, VPro StreamClean irrigation; Group EV, EndoVac irrigation. Cross-sections at 1, 3 and 5 mm levels from the apex were examined to calculate remaining debris area in the canal and isthmus spaces. Statistical analysis was completed by using Kruskal-Wallis test and Mann-Whitney U test for comparison among groups, and multivariate linear analysis to identify the significant variables (regular replenishment of irrigant, vapor lock management, and ultrasonic activation of irrigant) affecting the cleaning efficacy of the experimental groups.ResultsGroup SC and EV showed significantly higher canal cleanliness values than group C and U at 1 mm level (p < 0.05), and higher isthmus cleanliness values than group U at 3 mm and all levels of group C (p < 0.05). Multivariate linear regression analysis demonstrated that all variables had independent positive correlation at 1 mm level of canal and at all levels of isthmus with statistical significances.ConclusionsBoth VPro StreamClean and EndoVac system showed favorable result as final irrigation regimens for cleaning debris in the complicated root canal system having curved canal and/or isthmus. The debridement of the isthmi significantly depends on the variables rather than the canals.

In Vitro Canal and Isthmus Debris Removal of the Self-Adjusting File, K3, and WaveOne Files in the Mesial Root of Human Mandibular Molars

IntroductionThe purpose of this study was to compare the effectiveness of debris removal between the Self-Adjusting File (SAF), WaveOne, and K3 file systems in the mesial roots of mandibular molars. In addition, the SAF was tested as a potential adjunct after instrumentation with other systems. MethodsThe mesial roots of 30 extracted mandibular molars were mounted in resin by using the K-Kube, sectioned at 2 and 4 mm from working length, and randomly placed into 3 groups: K3 group, sequential preparation with K3 files to an apical size of 35/.04; WaveOne group, preparation with WaveOne primary file; and SAF group, preparation with SAF. Images were taken before instrumentation, after instrumentation, after final irrigation, and after SAF adjunct irrigation. A cleanliness percentage was calculated by using interactive software. Comparisons between groups were analyzed with repeated-measures analysis of variance and post hoc tests (P < .05). ResultsThere was no significant difference in canal cleanliness among the groups, but the WaveOne was significantly worse for isthmus cleanliness. Use of the SAF as an adjunct only significantly improved canal cleanliness in the K3 group at the 2-mm level by an average of 1.7%. ConclusionsThere was no difference in canal cleanliness between the 3 file systems; however, the SAF and K3 files performed significantly better than the WaveOne with respect to isthmus cleanliness. When used as a final irrigation adjunct device after instrumentation, the SAF provided a significant improvement only in a subset of the K3 group.

Comparison of Debris Removal with Three Different Irrigation Techniques

Introduction The purpose of this study was to compare the effectiveness of debris removal between EndoVac, PiezoFlow, or needle irrigation (Max-i-Probe) in mandibular molars. Methods The mesial roots of 30 extracted mandibular molars were mounted in resin by using the K-Kube and then sectioned at 2 and 4 mm from the apex. The specimens were reassembled and instrumented to size 40/0.04. A standard irrigation protocol was used during instrumentation in the PiezoFlow and Max-i-Probe groups. During instrumentation of teeth in the EndoVac group, the manufacturer’s recommendations for irrigation were followed. Images of the canals and isthmuses were taken before final irrigation. The percentage of cleanliness for each canal and isthmus was calculated by using interactive software. The specimens were reassembled for final irrigation with EndoVac, PiezoFlow, and Max-i-Probe by using similar volumes of irrigants. Images were again used to calculate cleanliness. Comparisons of canal and isthmus cleanliness before and after final irrigation were made by using paired t tests, and the groups were compared with repeated-measures analysis of variance ( P < .05). Results There were no statistically significant differences in canal and isthmus cleanliness among all 3 groups at 2 and 4 mm from working length before or after final irrigation. Canal and isthmus cleanliness significantly improved at all levels after the final irrigation regimen in each group. Conclusions Final irrigation by using EndoVac, the PiezoFlow, or Max-i-Probe with similar volumes of irrigants significantly improved canal and isthmus cleanliness.

In Vitro Comparisons of Debris Removal of the EndoActivator TM System, the F File TM, Ultrasonic Irrigation, and NaOCl Irrigation Alone after Hand-rotary Instrumentation in Human Mandibular Molars

Introduction The purpose of this in vitro study was to compare the debris removal efficacy of the EndoActivator TM system, the F file TM, ultrasonic irrigation, or 6% NaOCl irrigation alone in human mandibular molars after hand-rotary instrumentation. Methods A custom brass cube (K-Kube) was used to create a sealed canal system, allowing each tooth to serve as its own control. Forty extracted mandibular molars were randomly divided into 4 equal experimental groups. Each tooth was mounted, sectioned at 1, 3, and 5 mm from the working length, and then reassembled into the K-Kube, and the mesial roots were similarly prepared by using hand-rotary instrumentation. For final debridement, group 1 used F file for 30 seconds, group 2 used EndoActivator system for 30 seconds, group 3 used ultrasonic irrigation for 30 seconds, and group 4 used irrigation with 6% NaOCl within 1 mm of working length. All groups received a final irrigation with 6% NaOCl in each canal. Specimens were evaluated at 1, 3, and 5 mm from the working length for cleanliness by capturing a digital image with a stereomicroscope. All specimens had the percent cleanliness for each canal and isthmus calculated both before and after final debridement. Statistical analysis was completed by using a repeated-measures analysis of variance with Tukey post hoc tests. Results and Conclusions The results showed no statistically significant difference in canal or isthmus cleanliness among the 4 groups, but there was a statistically significant difference ( P < .001) in canal cleanliness between the 1-mm level versus the 3-mm and 5-mm levels for all of the groups.

In vitro evaluation of cleaning efficacy of various irrigation methods in mandibular molars

The aim of this in vitro study was to evaluate the cleaning efficacy of various irrigation methods in the mandibular mesial roots. The forty five mesial root canals were shaped by Profile .06 instruments to apical size #30 and irrigated with 5 ml of 3.5% NaOCl. The teeth were divided into 3 groups and irrigated finally for 1 minute; Group 1: syringe irrigation, Group 2: ultrasonic irrigation, Group 3: RinsEndo irrigation. After histological processing, the cross sections of apical 1, 3, and 5 mm level were examined with an optical microscope. The cleanliness values of canals and isthmuses were calculated and analyzed by MannWhitney U test. 1. There were no significant differences in both canal and isthmus cleanliness between syringe irrigation and ultrasonic irrigation except 5 mm level of isthmus. 2. RinsEndo irrigation had significantly higher canal cleanliness values than syringe irrigation at 1 mm and 3 mm levels (p < 0.05). Also, RinsEndo irrigation had significantly higher isthmus cleanliness values than syringe irrigation at all levels evaluated (p < 0.05). 3. There were no statistical differences in both canal and isthmus cleanliness between ultrasonic irrigation and RinsEndo irrigation except 3 mm level of canal. From this study, RinsEndo irrigation can be useful as an additional irrigation procedure.

The In Vivo Evaluation of Hand/Rotary/Ultrasound Instrumentation in Necrotic, Human Mandibular Molars

This in vivo, prospective, randomized, single-blinded study histologically compared biofilm/necrotic debridement efficiency of a hand/rotary technique versus a hand/rotary/1 min ultrasound technique in the mesial roots of necrotic, human mandibular molars. The hand/rotary group consisted of 20 mesial roots. The hand/rotary/ultrasound group consisted of 20 mesial roots prepared with the same hand/rotary technique followed by 1 min of ultrasonic irrigation, per canal, utilizing an ultrasonic needle in a MiniEndo unit. Following extraction, histologic preparation and staining, 0.2 mum cross-sections from the 1- to 3-mm apical levels were evaluated for percentage of biofilm/necrotic debris removal. Cleanliness results at the 1-, 2- and 3-mm levels for the hand/rotary and hand/rotary/ultrasound techniques, respectively, were: Canals, 80% versus 95%, 92% versus 99%, and 95% versus 100%; Isthmuses, 33% versus 83%, 31% versus 86%, 45% versus 91%. Statistical analysis revealed mean percent canal and isthmus cleanliness values to be significantly higher for hand/rotary/ultrasound technique at all levels evaluated.

In Vivo Debridement Efficacy of Ultrasonic Irrigation Following Hand-Rotary Instrumentation in Human Mandibular Molars

This study histologically compared the in vivo debridement efficacy of hand/rotary canal preparation versus a hand/rotary/ultrasound technique in mesial root canals of vital mandibular molars. Group 1 consisted of 16 teeth prepared with a hand/rotary technique whereas group 2 consisted of 15 teeth prepared in similar fashion but followed by 1 min of ultrasonic irrigation, per canal, utilizing an ultrasonic needle in a MiniEndo unit. Five uninstrumented mandibular molars served as histologic controls. After extraction and histologic preparation, 0.5 μm cross-sections, taken every 0.2 mm from the 1- to 3-mm apical levels, were evaluated for percentage of tissue removal. Nonparametric analysis revealed mean percent canal and isthmus cleanliness values to be significantly higher for group 2 at all levels evaluated, except one. In conclusion, the 1 min use of the ultrasonic needle after hand/rotary instrumentation resulted in significantly cleaner canals and isthmuses in the mesial roots of mandibular molars.

An in vivo evaluation of the efficacy of ultrasound after step-back preparation in mandibular molars

This study histologically compared the in vivo debridement efficacy of the step-back preparation versus a step-back/ultrasound preparation in the mesial root canals of vital mandibular molars. Group 1 consisted of 17 teeth prepared with a step-back technique using intermittent irrigation with 5.25% sodium hypochlorite. Group 2 consisted of 17 teeth prepared with a step-back technique as in group 1 followed by 3 min of ultrasonic instrumentation per canal utilizing a #15 Endosonic file in an Enac unit set at 3.5. An additional 6 ml/canal of 5.25% sodium hypochlorite was used during the ultrasonic preparation. Eight uninstrumented mandibular molars served as histological controls. Following extraction and histological preparation, 0.2-microns cross-sections from the 1- to 3-mm apical levels of the canal and isthmus were evaluated for percentage of tissue removal using an Olympus CUE-2 Image Analysis System. Factorial analysis of variance indicated canal and isthmus cleanliness values were significantly higher, at all 11 apical levels, with the ultrasonic technique. Sample values at the 1-, 2-, and 3-mm levels for the step-back and step-back/ultrasonic techniques, respectively, were: canal, 64% versus 92%, 81% versus 97%, and 90% versus 99.9%; isthmus, 2% versus 46%, 15% versus 60%, and 16% versus 83%.

An in vivo comparison of the step-back technique versus a step-back/ultrasonic technique in human mandibular molars

This study compared the in vivo debridement efficacy of the step-back preparation versus a step-back/ultrasound preparation in the mesial root canals of vital human mandibular molars. Group 1 consisted of 15 teeth prepared with a step-back technique using intermittent irrigation with 5.25% sodium hypochlorite. Group 2 consisted of 23 teeth prepared with a step-back technique as in group 1 followed by 3 min of ultrasonic instrumentation (Cavi-Endo) using 5.25% sodium hypochlorite (30 ml per min). Group 3 consisted of 21 teeth which were uninstrumented and served as controls. Following extraction and histological preparation, the 1- and 3-mm levels of the canal and isthmus were evaluated for percentage of tissue removal using a compensating polar planimeter. At the 3-mm level, there were no statistical differences in canal or isthmus cleanliness between the step-back group and the step-back/ultrasound group. At the 1-mm apical level, statistical analysis indicated that the step-back/ultrasonic technique was superior to the step-back technique in canal (99.6% versus 88%) and isthmus (86% versus 10%) cleanliness.

An in vitro comparison study to quantitate the debridement ability of hand, sonic, and ultrasonic instrumentation

This study compared, histologically and quantitatively, the debridement ability of hand, sonic, and ultrasonic instrumentation on the mesial root canals of 50 human mandibular molars. The time of instrumentation per canal for each treatment group was also evaluated. Only those roots with canal curvature between 20 and 40 degrees were used in this study. The Cavi-Endo unit utilizing 2.6% NaOCl demonstrated a significantly greater percentage of canal cleanliness at the 1-mm level than any other treatment group except for the ENAC ultrasonic system. The ENAC ultrasonic system significantly cleaned a greater percentage of the canal than the sonic instrument or the Cavi-Endo/water group. Sonic instrumentation was not significantly better than hand instrumentation in canal cleanliness at the 1-mm level. Statistical analysis indicated no significant difference in canal and isthmus cleanliness at the 3-mm level. However, the Cavi-Endo unit utilizing 2.6% NaOCl exhibited the greatest percentage of canal and isthmus cleanliness. Sonic and ultrasonic instrumentation were significantly faster in preparing the root canal system than hand instrumentation in this study. This study compared, histologically and quantitatively, the debridement ability of hand, sonic, and ultrasonic instrumentation on the mesial root canals of 50 human mandibular molars. The time of instrumentation per canal for each treatment group was also evaluated. Only those roots with canal curvature between 20 and 40 degrees were used in this study. The Cavi-Endo unit utilizing 2.6% NaOCl demonstrated a significantly greater percentage of canal cleanliness at the 1-mm level than any other treatment group except for the ENAC ultrasonic system. The ENAC ultrasonic system significantly cleaned a greater percentage of the canal than the sonic instrument or the Cavi-Endo/water group. Sonic instrumentation was not significantly better than hand instrumentation in canal cleanliness at the 1-mm level. Statistical analysis indicated no significant difference in canal and isthmus cleanliness at the 3-mm level. However, the Cavi-Endo unit utilizing 2.6% NaOCl exhibited the greatest percentage of canal and isthmus cleanliness. Sonic and ultrasonic instrumentation were significantly faster in preparing the root canal system than hand instrumentation in this study.

An in vitro comparison of the efficacy of the stepback technique versus a step-back/ultrasonic technique in human mandibular molars

This study compared the effect of the step-back preparation versus a step-back/ultrasound preparation on the tissue removal from the mesial root canals of 60 extracted human mandibular molars. The step-back/ultrasound preparation significantly cleaned isthmuses at both levels and canals at the 1-mm level more effectively than the step-back preparation. Statistical analysis indicated no significant difference, in canal cleanliness at the 3-mm level, between the step-back and the step-back/ ultrasound groups. There were no significant differences demonstrated in isthmus cleaning ability when comparing the step-back group with the control group, at both the 1- and 3-mm levels. At the 1-mm level, operator 1 significantly cleaned canals in the step-back group more effectively than operator 2. However, in the step-back/ultrasound group, no significant differences were demonstrated between operators in their ability to clean canals at this level. In both experimental groups, operator comparisons indicated no significant differences in isthmus cleanliness at the 1-mm level. This study compared the effect of the step-back preparation versus a step-back/ultrasound preparation on the tissue removal from the mesial root canals of 60 extracted human mandibular molars. The step-back/ultrasound preparation significantly cleaned isthmuses at both levels and canals at the 1-mm level more effectively than the step-back preparation. Statistical analysis indicated no significant difference, in canal cleanliness at the 3-mm level, between the step-back and the step-back/ ultrasound groups. There were no significant differences demonstrated in isthmus cleaning ability when comparing the step-back group with the control group, at both the 1- and 3-mm levels. At the 1-mm level, operator 1 significantly cleaned canals in the step-back group more effectively than operator 2. However, in the step-back/ultrasound group, no significant differences were demonstrated between operators in their ability to clean canals at this level. In both experimental groups, operator comparisons indicated no significant differences in isthmus cleanliness at the 1-mm level. Este estudio comparó el efecto de la preparación escalonada versus la preparación escalonada por ultrasonido en la remoción de tejido del conducto de la raiz mesial de 60 molares humanos inferiores extraídos. La preparación escalonada por ultrasonido limpió los istmos en ambos niveles significati-vamente y los conductos a un nivel de 1 mm más efectivamente que la preparación escalonada. El análisis estadístico no indicó diferencias significativas en la limpieza del conducto a un nivel de 3 mm entre los grupos de técnica escalonada y técnica escalonada por ultrasonido. No se demostraron diferencias significativas en la capacidad de limpieza de los itstmos cuando se comparó el grupo de técnica escalonada con el grupo de control, tanto en el nivel de 1 mm como en el de 3 mm. En el nivel de 1 mm, el operador 1 limpió los conductos en el grupo de técnica escalonada en forma significati-vamente más efectiva que el operador 2. Sin embargo, en el grupo de técnica escalonada por ultrasonido, no se demostraron diferencias de importancia entre los operadores en su capacidad de limpiar los conductos a este nivel. En ambos grupos experimentales, las comparaciones del operador no indicaron diferencias significativas en la limpieza de los istmos en un nivel de 1 mm. Este estudio comparó el efecto de la preparación escalonada versus la preparación escalonada por ultrasonido en la remoción de tejido del conducto de la raiz mesial de 60 molares humanos inferiores extraídos. La preparación escalonada por ultrasonido limpió los istmos en ambos niveles significati-vamente y los conductos a un nivel de 1 mm más efectivamente que la preparación escalonada. El análisis estadístico no indicó diferencias significativas en la limpieza del conducto a un nivel de 3 mm entre los grupos de técnica escalonada y técnica escalonada por ultrasonido. No se demostraron diferencias significativas en la capacidad de limpieza de los itstmos cuando se comparó el grupo de técnica escalonada con el grupo de control, tanto en el nivel de 1 mm como en el de 3 mm. En el nivel de 1 mm, el operador 1 limpió los conductos en el grupo de técnica escalonada en forma significati-vamente más efectiva que el operador 2. Sin embargo, en el grupo de técnica escalonada por ultrasonido, no se demostraron diferencias de importancia entre los operadores en su capacidad de limpiar los conductos a este nivel. En ambos grupos experimentales, las comparaciones del operador no indicaron diferencias significativas en la limpieza de los istmos en un nivel de 1 mm.