Disinfecting and Shaping Type I C-shaped Root Canals: A Correlative Micro–computed Tomographic and Molecular Microbiology Study

IntroductionThis ex vivo study compared the disinfection and shaping abilities of 2 preparation protocols in C-shaped canals.MethodsMandibular second molars with type I C-shaped canals were pair matched based on micro–computed tomographic (micro-CT) analysis and distributed into 2 groups. The canals were contaminated with a mixed bacterial culture and prepared using 2 protocols, both with 2.5% sodium hypochlorite irrigation: XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland) supplemented with XP-endo Finisher (FKG Dentaire) (XP-E) and BioRaCe (FKG Dentaire) supplemented with a Hedström file (Dentsply/Sirona, Tulsa, OK) (BR-Hed). Micro-CT scans and intracanal bacteriologic samples were taken before (scan #1 and sample 1) and after preparation (scan #2 and sample 2) and after the supplementary step (scan #3 and sample 3). Canal shaping was evaluated by micro-CT imaging, and disinfection was assessed by quantitative polymerase chain reaction.ResultsMicro-CT data from the XP-E (n = 21) and BR-Hed (n = 23) protocols revealed no significant differences between groups regarding shaping parameters (canal volume, surface area, structure model index, and prepared walls) after preparation and after the supplementary step (P > .05). All these parameters significantly increased after each preparation step (P < .05), except for structure model index changes after the XP-endo Finisher (P > .05). Bacteriologic data from the XP-E (n = 21) and BR-Hed (n = 22) groups showed that 14 (66.7%) and 10 (45.5%) S2 samples still had detectable bacteria, respectively. The corresponding figures for supplementary steps with the XP-endo Finisher and Hedström file were 11 (52.4%) and 10 (45.5%), respectively. Bacterial counts in sample 1 significantly decreased in samples 2 and 3 in both groups (P < .01). Intragroup comparison between sample 2 and sample 3 showed a 66% reduction in counts after using the Hedström file and 18% after using the XP-endo Finisher (P > .05 for both groups). The quantitative bacterial reduction was not different between groups (P > .05).ConclusionsThe XP-endo Shaper and BioRaCe systems have similar disinfecting and shaping abilities in C-shaped canals. Supplementary steps with the Hedström file and the XP-endo Finisher were similarly effective in improving shaping, but this was not sufficient to enhance disinfection. About half of the cases, in both groups, still harbored detectable amounts of bacteria.     

Micro–computed Tomographic Assessment of Supplementary Cleaning Techniques for Removing Bioceramic Sealer and Gutta-percha in Oval Canals

IntroductionThe aim of this study was to conduct a micro–computed tomographic assessment of the effectiveness of 3 supplementary cleaning techniques in reducing the residual volume of gutta-percha and a bioceramic sealer after performing endodontic retreatment procedures in teeth with oval canals.MethodsThirty-six mandibular premolars were instrumented with the ProTaper Next system (instruments X1–X3; Dentsply Maillefer, Ballaigues, Switzerland) and filled with gutta-percha and Bio-C Sealer (Angelus, Londrina, PR, Brazil) using the single-cone technique. The teeth were reinstrumented with the Reciproc R40 instrument (VDW, Munich, Germany) and divided into 3 groups according to the supplementary cleaning technique used (n = 12): ultrasonic-assisted irrigation (UAI), EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK) irrigation (EAI), or the XP-endo Finisher R system (XPR; FKG Dentaire, La Chaux-de-Fonds, Switzerland). Micro–computed tomographic imaging was used to quantify the residual volume of filling material. One-way analysis of variance complemented by the Tukey test was used to perform the statistical analysis (P < .05).ResultsSignificant reductions were obtained in the residual filling material after supplementary cleaning (P < .05). XPR (47.5%) led to significantly greater (P < .05) filling material removal than UAI (16.6%) or EAI (22.6%). The removal values of the 2 latter systems were not significantly different.ConclusionsXPR was more effective than UAI and EAI in removing filling material in mandibular premolars with oval canals. None of the tested supplementary cleaning techniques completely removed the residual filling material.     

Cleaning,Shaping, and Disinfecting Abilities of 2 Instrument Systems as Evaluated by a Correlative Micro–computed Tomographic and Histobacteriologic Approach

IntroductionThis study assessed the cleaning, shaping, and disinfection abilities of 2 instrumentation systems in molar root canals using a novel correlative analytical approach.MethodsThe root canals from extracted mandibular and maxillary molars with apical periodontitis were pair matched according to anatomic similarities as determined by micro–computed tomographic analysis and prepared with either XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland) (n = 16) or Reciproc Blue (VDW, Munich, Germany) (n = 16) instruments and 2.5% sodium hypochlorite irrigation. Pre- and postpreparation micro–computed tomographic scans were used to identify and calculate the unprepared surface areas (shaping), which were histobacteriologically evaluated for the presence of residual bacteria (disinfection) and pulp tissue remnants (cleaning) in each canal third.ResultsUnprepared canal surface areas for XP-endo Shaper and Reciproc Blue in the full canal length were approximately 26% and 19% (P < .05), respectively (30% and 23% in the apical part of the canal, P > .05). Preparation with Reciproc Blue resulted in 37.5% canals free of bacteria in all sections examined and 56% in the apical sections only. XP-endo Shaper resulted in 44% canals free of bacteria in all sections, and 56% in the apical part of the canal only. Pulp tissue remnants were not observed in 31% (all canal sections) and 50% (apical canal sections) of specimens from both instrument systems. No significant differences were observed between instruments when comparing the amount of pulp tissue remnants and the number of cases negative for bacteria and tissue remnants (P > .05).ConclusionsAlthough the Reciproc Blue instrument had superior shaping ability in comparison with XP-endo Shaper, both systems performed similarly in cleaning and disinfecting root canals. Irregular canals and difficult-to-reach areas were not thoroughly cleaned and disinfected by any of the tested systems.     

Micro–computed Tomographic Evaluation of the Shaping Ability of 3 Reciprocating Single-File Nickel-Titanium Systems on Single- and Double-Curved Root Canals

IntroductionWe performed a micro–computed tomographic assessment of the preparation of moderately single- and double-curved root canals using 3 single-file reciprocating nickel-titanium systems: S1 Plus Standard (Sendoline, Täby, Sweden), WaveOne Gold Primary (Dentsply Sirona, Ballaigues, Switzerland), and Reciproc R25 (VDW, Munich, Germany).MethodsSeventy-five moderately curved mandibular molars with 2 separate mesial root canals were assigned to 3 experimental groups (n = 25) (ie, S1 Plus Standard, WaveOne Gold Primary, and Reciproc 25 groups) by forming matched triples according to curvature (15°–40°), radius (≤18 mm), and type of curvature (single or double curved). Teeth were scanned before and after root canal preparation with a resolution of 10.5 μm using micro–computed tomographic imaging (Bruker SkyScan 1272; Bruker microCT, Kontich, Belgium). The following parameters were assessed: changes in root canal volume and surface area, percentage of unshaped canal walls, structure model index, canal transportation, and centering ratio. Data were analyzed using 2- and 3-way analysis of variance with Tukey and Scheffé post hoc tests (significance level of 5%).ResultsNo significant differences among groups were observed concerning all parameters. The type of curvature had no significant effect on all tested parameters. Within all experimental groups, canal transportation increased significantly from the apical to the coronal region, of which the majority was directed toward the furcational area.ConclusionsPreparation with the 3 nickel-titanium systems did not result in significantly different dimensional changes, and there was no significant effect of the type of curvature on all tested parameters.     

Micro–computed Tomographic Evaluation of the Shaping Ability of XP-endo Shaper,iRaCe, and EdgeFile Systems in Long Oval-shaped Canals

Introduction

This study evaluated the shaping ability of the XP-endo Shaper (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland), iRaCe (FKG Dentaire SA), and EdgeFile (EdgeEndo, Albuquerque, NM) systems using micro–computed tomographic (micro-CT) technology.

Changes in Geometry and Transportation of Root Canals with Severe Curvature Prepared by Different Heat-treated Nickel-titanium Instruments: A Micro–computed Tomographic Study

IntroductionThe aim of this study was to compare the shaping ability of 4 different nickel-titanium systems, considering their variation in alloy treatment, kinematics, and design, used to prepare canals with severe curvature using micro–computed tomographic analysis.MethodsThirty-two mesial roots of mandibular molars with severe curvature were matched based on similar morphologic dimensions and assigned to 4 experimental groups (n = 8) according to the canal preparation: ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Reciproc (RC; VDW GmbH, Munich, Germany), Reciproc Blue (RCB, VDW GmbH), and TRUShape (TRU; Dentsply Tulsa Dental Specialties, Tulsa, OK) systems. Changes in 2-dimensional (area and perimeter) and 3-dimensional (volume, surface area, and structure model index) morphologic parameters as well as canal transportation were compared among groups using the analysis of variance post hoc Tukey tests with the significance level set at 5%.ResultsPreparation significantly increased all analyzed parameters. No statistically significant differences (P > .05) were observed between RC and RCB or between PTN and TRS in any of the analyzed parameters. In the cervical third, RC and RCB presented higher mean increases than PTN and TRU. In the apical third, there were no statistically significant differences (P > .05) among the systems.ConclusionsThe instruments of greater taper may promote greater morphologic changes. However, regardless of the number of instruments (multiple or single), the type of movement (rotation or reciprocating), the type of heat treatment of alloys, and the particular characteristics of each instrument (taper and design), the evaluated systems did not result in different dimensional changes and canal transportation in the critical apical area.     

New Ultrasonic Tip Decreases Uninstrumented Surface and Debris in Flattened Canals: A Micro–computed Tomographic Study

IntroductionThe preparation of flattened root canals using reciprocating or rotary nickel-titanium instruments associated with the Flatsonic ultrasonic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was evaluated by micro–computed tomographic imaging.MethodsTwenty-four flattened distal canals of mandibular molars with a buccolingual diameter 4 or more times larger than the mesiodistal diameter were selected. The root canals were randomly divided into 2 experimental groups for preparation: a Reciproc Blue (RB; VDW GmbH, Munich, Germany) 40/.06 file in reciprocating motion or ProDesign Logic (PDL; Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) 40/.01 and 40/.05 files in rotary motion (n = 12). A complementary preparation was performed with the Flatsonic ultrasonic tip for both preparations. Micro–computed tomographic scanning at a resolution of 8.74 μm was performed before and after preparation with the nickel-titanium instruments and after the use of the Flatsonic tip. The percentages of increase in volume, debris, and uninstrumented surface were analyzed. The data obtained were submitted to the paired and unpaired t test, analysis of variance, and the Tukey test (α = 5%).ResultsThe percentage increase in volume, debris, and uninstrumented surface was similar between RB and PDL in the entire root canal (P > .05). The PDL promoted a lower percentage of debris in the cervical third and a lower percentage of increase in volume in the apical third in comparison with RB (P < .05). The Flatsonic decreased debris and uninstrumented surface after PDL preparation in all thirds (P < .05). After preparation with RB, the Flatsonic decreases the debris in the cervical third and the uninstrumented surface in the cervical and middle thirds (P < .05).ConclusionsThe preparation of flattened root canals using RB or PDL produced a high percentage of debris and uninstrumented surface. The Flatsonic ultrasonic tip significantly improved the cleaning of flattened root canals.     

Cleaning and Shaping Ability of Gentlefile,HyFlex EDM,and ProTaper Next Instruments: A Combined Micro–computed Tomographic and Scanning Electron Microscopic Study

IntroductionThis ex vivo study aimed to evaluate the cleaning and shaping ability of a unique stainless steel rotary system (Gentlefile; MedicNRG, Kibbutz Afikim, Israel) compared with 2 nickel-titanium rotary instruments.MethodsThirty human mandibular premolars with a 15° to 25° curvature were equally distributed into 3 groups for final instrumentation with Gentlefile Red (#23/0.04), HyFlex EDM OneFile (#25/0.08∼; Coltene/Whaledent, Altstätten, Switzerland), and ProTaper Next X2 (#25/0.06v; Dentsply Sirona, Ballaigues, Switzerland) (n = 10/each). The untouched canal area, volume changes, and transportation were evaluated on pre- and post-instrumentation micro–computed tomographic images. Five random regions of the canal wall located 1–7 mm from the apical foramen were evaluated with scanning electron microscopy for superficial debris and a smear layer via a 5-point scoring system. Data were compared using the Kruskal-Wallis test with post hoc Dunn's pairwise comparison test with Bonferroni correction and Wilcoxon signed-rank test (α = 5%).ResultsAll instruments generated no overt procedural errors. Untouched area and volume changes did not show any significant differences among the 3 groups (P > .05). The Gentlefile exhibited less transportation at the level of 5–7 mm from the apex compared with ProTaper Next (P < .05). The Gentlefile showed a smaller debris score than ProTaper Next and better smear layer removal than the others (P < .05). Complete cleanliness was not achieved by any of the systems investigated.ConclusionsCanals instrumented with the Gentlefile exhibited less transportation at the mid-root level and better cleanliness than those instrumented with HyFlex EDM and ProTaper Next.     

TRUShape Versus XP-endo Shaper: A Micro–computed Tomographic Assessment and Comparative Study of the Shaping Ability—An In Vitro Study

IntroductionThe aim of this study was to evaluate and compare the shaping ability of XP-endo Shaper (XP; FKG Dentaire, La Chaux-de-Fonds, Switzerland) and TRUShape (TS; Dentsply/Tulsa Dental Specialties, Tulsa, OK) during the preparation of moderated curved root canals using micro–computed tomographic imaging.MethodsTwenty human maxillary premolars with 2 roots were randomly separated into 2 groups of 10 teeth, which were scanned before and after root canal preparation using the SkyScan 1275 X-ray microtomograph (Bruker micro-CT, Kontich, Belgium) at a nominal resolution of <4 μm. Premolars and irrigant were maintained at 37° before and during preparation; group 1 was treated using XP and group 2 with TS. After preparation, researchers measured the amount of dentin removed, untreated superficies of canal walls, root canal volume, degree of canal transportation, and centering ability. Values of central tendency and dispersion were calculated using Statgraphics Centurion XV software (StatPoint Technologies, Inc, Warrenton, VA); means and median were compared using the Mann-Whitney-Wilcoxon test. The level of significance was set at 5% (P < .05).ResultsNo significant statistical differences were observed between the 2 groups in shaping ability, untreated superficies of canal walls, degree of canal transportation, and centering ability (P > .05).ConclusionsInstrumentation of moderately curved root canals using the XP single file and the TS file system were equally effective. XP and TS maintained the original anatomy of the root canals and showed a similar percentage of untreated canal walls, centered ability, and minimal apical transportation.     

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.

Root Canal Shaping Effect of Instruments with Offset Mass of Rotation in the Mandibular First Molar: A Micro–computed Tomographic Study

Introduction

The aim of this study was to evaluate the root canal shaping effect of 2 nickel-titanium rotary instruments with offset mass of rotation compared with an instrument with a conventional centered mass of rotation.

Micro–computed Tomographic Assessment and Comparative Study of the Shaping Ability of 6 Nickel-Titanium Files: An In Vitro Study

IntroductionThis research studies and compares the shaping ability of WaveOne Gold (WG; Dentsply Tulsa Dental Specialties, Tulsa, OK), the Reciproc Blue (RB; VDW, Munich, Germany), TRUShape (TS, Dentsply Tulsa Dental Specialties), XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland), iRace (IR, FKG), and TruNatomy (TN; Dentsply Sirona, Ballaigues, Switzerland) in the preparation of moderately curved canals and using micro–computed tomographic technology.MethodsSixty lower molars with 2 mesial canals were randomly distributed into 6 groups of 10 molars and 20 canals per group (n = 20). Specimens were scanned before and after preparation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WG, group 2 with RB, group 3 with TS, group 4 with XP, group 5 with IR, and group 6 with TN. After instrumentation, researchers quantified the changes produced in the canal geometry in terms of surface, volume, structure thickness, surface convexity index, structure model index, percentage of surface touched, and centroids. Wilcoxon and analysis of variance tests were performed to compare the values before and after preparation and the differences between groups. The significance level was established at 5%.ResultsThere were no significant differences between WG and RB (P > .05) and between TN and XP (P > .05). TN had significant differences with WG, RB, TS, and IR (P < .05). All the files produced similar apical transportation (P > .05).ConclusionsWG and RB and TN and XP had similar shaping effectivity. TS and WG touched the highest percentages of canal surfaces (81% and 73%, respectively) but produced the biggest changes in the canal anatomy. TN and XP better kept the canal anatomy, but TN touched the lowest percentage of canal surface (50%). All the files used were able to clean and to shape moderately curved canals with minimal apical transportation.     

Analysis of Instrumentation Protocols Regarding the Quality of Mesial Canal Preparation in Mandibular Molars: A Micro–computed Tomographic Study

IntroductionThis study aimed to use micro–computed tomographic imaging to analyze the quality of the endodontic preparation of mesial canals in mandibular molars provided by 3 instrumentation protocols.MethodsForty-five extracted mandibular molars with 2 independent mesial canals were selected, and the initial micro–computed tomographic imaging was performed. The initial volume values of the canals were submitted to statistical analysis for paired division. The groups were determined according to the final enlargement of the canal and the working length adopted (ie, G25.06/+1 mm, G35.05/foramen, and G50.01/−1 mm). At the end of each instrumentation sequence, the root canals were scanned and analyzed with regard to the increase in the total and apical volume, centralization, and preparation transportation and the percentage of the total and apical uninstrumented walls.ResultsFor the intragroup comparison, the Wilcoxon test was used, and for the intergroup analysis, the Kruskal-Wallis and Dunn tests were used (P < .05). In the analysis of the canal total volume, a statistical difference was found between G25.06/+1 mm and the remaining groups (P < .05). In the apical third, a statistical difference was observed between G25.06/+1 mm and G50.01/−1 mm (P < .05). No statistical difference was found between the groups in terms of centralization and transportation of the preparation or in terms of the percentage of the total or apical uninstrumented walls.ConclusionsThe preparation of the mesial canals of mandibular molars up to larger tip files but with a lower taper at 1 mm before the foramen resulted in a larger volume of apical preparation, kept the preparation centralized, and provided safe apical dentin wear without excessive cervical wear.     

A Micro–computed Tomographic Evaluation of the Accuracy of 3 Electronic Apex Locators in Curved Canals of Mandibular Molars

Introduction

This study evaluated the accuracy of 3 electronic apex locators (EALs) (CanalPro [Coltene-Endo, Cuyahoga Falls, OH], Apex ID [SybronEndo, Glendora, CA], and Root ZX Mini [J Morita, Tokyo, Japan]) in curved mesial canals of extracted mandibular molars using micro–computed tomographic (micro-CT) scanning.

Geometric Analysis of the Distolingual Root and Canal in Mandibular First Molars: A Micro–computed Tomographic Study

IntroductionThe purpose of this study was to comprehensively assess by micro–computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.MethodsOne hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.ResultsAll DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.ConclusionsThe novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.     

Efficacy of Reciprocating Instruments for Removing Filling Material in Curved Canals Obturated with a Single-cone Technique: A Micro–computed Tomographic Analysis

Introduction

The aim of this study was to evaluate the efficacy of nickel-titanium reciprocating instrument techniques and passive ultrasonic irrigation (PUI) for retreatment in curved canals and obturated with correspondent single cones.

Methods

Twenty molars were selected with mesial-buccal canals with curvatures between 20° and 40°, and they were instrumented with a Reciproc R25 instrument (VDW, Munich, Germany) in a reciprocating motion and obturated with single cones and AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). The teeth were divided into 2 groups (n = 10) according to the instrument used for the removal of filling material: group 1: Reciproc R25 instrument and group 2: WaveOne Primary instrument (Dentsply Maillefer). The analysis of the remnant filling material was made through micro–computed tomographic imaging after the use of reciprocating instruments and again after the use of PUI with xylene. The effective time of retreatment was registered.

Results

The filling material of the root canal was efficiently removed (P < .05) for both groups. The percentage of removal of filling materials was 93% for the Reciproc group and 92% for the WaveOne group. There were no statistical significant differences (P > .05) between the groups in relation to the removal of filling material ability and the time needed for the procedure. The effective time for the removal of filling material was 78.7 seconds and 89.5 seconds for the Reciproc and WaveOne groups, respectively.

Conclusions

It was concluded that both instruments efficiently but not completely removed the filling material from inside the root canals. The use of xylene with PUI increased the removal of filling material a little, but it was not statically significant.     

Assessment of Mechanical Root Canal Preparation with Centric Reciprocating or Eccentric Rotary Kinematics: A Micro–computed Tomographic Study

IntroductionThe aim of this study was to compare, using micro–computed tomographic imaging, the preparation of mesial canals of mandibular molars with the Reciproc (VDW GmbH, Munich, Germany) and XP-endo Shaper (FKG, La Chaux-de-Fonds, Switzerland) systems, evaluating changes in dentin and canal volume, the percentage of untouched walls, the volume of accumulated hard tissue debris, and root canal deviation in the apical third.MethodsTwenty-four mandibular molars with 2 mesial root canals and a single foramen were anatomically paired and divided into 2 experimental groups (n = 12) according to the system used. The specimens were scanned before and after preparation with the SkyScan 1176 microtomographic scanner (Bruker-microCT, Kontich, Belgium) at a resolution of 17.42 μm. The resulting data were statistically compared at a significance level of 5% using the Student t test and the Mann-Whitney test.ResultsA significant difference was observed in the untouched surface area for the total canal and the cervical and middle thirds, with the lowest untouched surface area in the XP-endo Shaper group (P < .05). The volume of accumulated hard tissue debris was significantly higher in the Reciproc group in the total canal as well as in the middle and apical thirds. There was no significant difference between the groups regarding the volume of dentin removed or the increase in canal volume and surface area (P > .05).ConclusionsThe XP-endo Shaper touched more walls and left less accumulated hard tissue debris in the root canal system than the Reciproc group. Although the XP-endo Shaper showed superior results, neither system was able to fully prepare the root canal.     

Effect of Access Cavity Preparation on Dentin Preservation,Biomechanical Property,and Instrumentation Efficacy: A Micro–Computed Tomographic Study

IntroductionThe purpose of this study was to evaluate the influence of a contracted endodontic cavity (CEC) on dentin preservation, biomechanical property, and instrumentation efficacy of first permanent molars in comparison with a traditional endodontic cavity (TEC).MethodsForty-eight extracted intact maxillary and mandibular first molars were selected and scanned by micro–computed tomographic (micro-CT) imaging. Each tooth type was anatomically matched and assigned to the CEC group or the TEC group (n = 12). After root canal instrumentation with the ProGlider (Dentsply Maillefer, Ballaigues, Switzerland) and WaveOne Gold (Dentsply Maillefer), the specimens were scanned by micro-CT again. Pre- and postpreparation micro-CT imaging was used to evaluate the dentin preservation and instrumentation efficacy. The results on volume and thickness reduction in the coronal dentin and pericervical dentin (PCD), root canal volume and surface area, percentage of unprepared surface area, canal transportation and centering ratio, and canal wall thickness in the “danger zone” were measured and analyzed with the Shapiro-Wilk and independent sample t tests. Based on micro-CT imaging of maxillary and mandibular first molars, CEC and TEC models were constructed on the intact tooth, and 2 different static loads were applied to the occlusal load points. The stress distribution patterns and von Mises stress on the occlusal surface and cervical region were assessed by 3-dimensional finite element analysis.ResultsThe CEC had a significantly lower volume and thickness reduction of coronal dentin and PCD above the alveolar crest compared with the TEC group (P < .05), whereas no difference was observed in PCD below the alveolar crest between the 2 groups (P > .05). There was no difference regarding all instrumentation efficacy outcomes (root canal volume and surface area, percentage of unprepared surface area, canal transportation and centering ratio, and canal wall thickness) in the danger zone between the 2 groups (P > .05). The CEC effectively reduced the maximum von Mises stress and stress concentration area on the occlusal surface and cervical region compared with the TEC.ConclusionsThe CEC preserved more coronal dentin and PCD above the alveolar crest and thus reduced stress concentration on the occlusal surface and cervical region. The CEC had no significant adverse effects on the instrumentation efficacy compared with the TEC given that the instrumentation procedures were performed with ProGlider and WaveOne Gold files.     

Micro–computed Tomographic Evaluation of the Shaping Ability of WaveOne Gold,TRUShape, EdgeCoil,and XP-3D Shaper Endodontic Files in Single,Oval-shaped Canals: An In Vitro Study

IntroductionThis study evaluated and compared the shaping ability of the WaveOne Gold (Dentsply/Tulsa Dental Specialties, Tulsa, OK), TRUShape 3D Conforming File (Dentsply/Tulsa Dental Specialties), EdgeCoil (EdgeEndo, Albuquerque, NM), and XP-3D Shaper (Brasseler USA, Savannah, GA) endodontic file systems on oval-shaped canals using micro–computed tomographic (micro-CT) technology.MethodsThirty-two oval-shaped, single-canal extracted human teeth were decoronated 1 mm coronal to the cementoenamel junction and scanned via a micro-CT scanner (μCT100; Scanco Medical, Bassersdorf, Switzerland). Teeth were divided into 4 groups (n = 8) and instrumented according to the manufacturer's instructions. Coregistered images, before and after root canal preparation, were evaluated for morphometric measurements of the surface area, volume, structure model index (SMI), conicity, and percent of walls untouched using the manufacturer's evaluation software (IPL Register, Scanco Medical). Data were statistically compared between groups using 1-way analysis of variance and within groups using a paired sample t test.ResultsInstrumentation with all file types increased the surface area, volume, and conicity between and within groups. There was no statistically significant difference between the groups for any of the rotary instruments used (P < .05).ConclusionsInstrumentation of oval-shaped canals with WaveOne Gold, TRUShape, EdgeCoil, and XP-3D Shaper rotary endodontic instruments similarly increase the volume, surface area, and conicity. None of the file systems were capable of contacting all of the surface area in any canal.