Shaping ability of three nickel-titanium rotary instruments in simulated L-shaped canals: OneShape, Hero Shaper, and Revo-S.

BACKGROUND: Shaping ability of a file plays an important role during instrumentation in an endodontic treatment. This study aimed to compare the shaping ability of OneShape (OS), Hero Shaper (HS), and Revo-S (RS) instruments in simulated L-shaped canals. METHODS: Forty-eight simulated L-shaped canals were prepared to an apical size of 25 using OS, HS, and RS (all from Micro-Mega SA, Besançon, France), (n = 16 canals/group) systems. The amount of resin removed after each canal's preparation was measured and compared after producing a composite image made from the superimposition of pre and post-instrumented canals. Canal aberrations and the preparation time were also recorded. The data were statistically analysed by using ANOVA, Tukey, and Chi-square tests. RESULTS: One file fractured during instrumentation in the RS group. A significant difference was found at the apical end of the prepared simulated canal between the groups, with RS showing the least amount of resin removal from the inner side of the canals and HS showing the highest amount of resin removal from the outer side (P < 0.05). Regarding the total width of the canals after preparation, a significant difference was found between the groups at the apical end and the straight portion of the canals, and RS removed the least amount of resin at the straight portion of the canals (P < 0.05). No statistically significant differences were found between the different instruments regarding canal aberrations' incidence (P > 0.05). CONCLUSIONS: All of the files showed a tendency to straighten the canals, whereas OS files maintained the original canal curvatures well.

Stereomicroscopic Evaluation of Microcrack Formation in Dentin by ProTaper Next, Revo S, and WaveOne Gold File System.

BACKGROUND: During the biomechanical preparation of the root canal by rotary file systems, stress is generated within the canal, which leads to dentinal microcrack formation. Such defects are evaluated only under the microscope. AIM: The present study aimed to evaluate dentinal microcrack formation after instrumentation with ProTaper Next (M-wire), Revo S (conventional NiTi), and WaveOne Gold (Gold-wire) file systems under the stereomicroscope. MATERIALS AND METHODS: Forty single-rooted teeth free from any defect were selected and divided into four groups (Control, PTN, RS, and WOG). Experimental groups were instrumented with file system used in the study, and the control group were left unprepared. Samples were further decoronated and sectioned at 3 mm, 6 mm, and 9 mm from the apex perpendicular to the long axis and examined under a stereomicroscope at ×25 for different types of microcracks (no fracture, complete fracture, partial fracture, and other fracture). STATISTICAL ANALYSIS USED: Data analysis was done by the Chi-square test using the SPSS version 17.0 software. A two-sided (α = 2) P < 0.05 (P < 0.05) was considered statistically significant. RESULTS: The null hypothesis was rejected. There was a statistically significant difference between the groups. All file systems created microcracks in the root dentin. WOG group showed an incidence of 66.7% for no fracture, PTN group had 40% for other fracture, and RS group had 60% for complete fracture. CONCLUSION: Single file system WOG with gold wire technology proves to be the best choice for canal preparation among the tested groups in terms of least dentinal crack formation.

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. METHODS: Thirty-six extracted human mandibular first molars with 2 independent mesial canals and 1 oval distal canal were selected and divided equally into 3 groups for instrumentation with ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Revo-S (RS; Micro-Mega, Besançon, France), and ProTaper Universal (PTU, Dentsply Maillefer) systems (n = 12). For apical preparation, PTN X2 (#25/0.06), RS SU (#25/0.06), and PTU F2 (#25/0.08) were used in the mesial canals and PTN X3 (#30/0.07), RS AS30 (#30/0.06), and PTU F3 (#30/0.09) were used in the distal canals. Specimens were scanned before and after instrumentation using a SkyScan 1272 scanner (Bruker micro-CT, Kontich, Belgium) at 10-µm isotropic resolution. Changes in the canal area, volume, structure model index (SMI), and untouched canal area were evaluated. Canal transportation and centering ratio were measured at 1, 3, 5, and 7 mm from the apical foramen. Data were statistically analyzed using 1-way analysis of variance with the Tukey post hoc test. RESULTS: The PTN and RS systems showed significantly less transportation and better centering ability compared with the PTU system at 1 mm from the apical foramen (P < .05). All instrumentation increased the canal area, volume, and SMI values without significant differences among the 3 groups (P > .05). CONCLUSIONS: Regardless of the differences in the cross-sectional design, alloy type, and taper variation, instruments with offset mass of rotation showed better root canal shaping ability compared with an instrument with a centered mass of rotation.

3D Micro-CT Analysis of Void and Gap Formation in Curved Root Canals.

OBJECTIVE: This study used microcomputed tomography (micro-CT) to compare the volumes of voids and gaps in curved root canals instrumented and filled using various techniques. METHODS: Twenty extracted mandibular first molars with two curved mesial root canals were used. Root canals were instrumented using a self-adjusting file (SAF) or Revo-S file system. For standardization, mesiobuccal canals were instrumented with SAF and mesiolingual canals were instrumented with Revo-S in each root. The canals were divided into four experimental groups (n=10 in each). The canals were then filled via cold lateral compaction (CLC) or a thermoplasticized injectable technique (TT) using gutta-percha and AH Plus root canal sealer. The roots were scanned with a micro-CT, and the volumes of the voids and gaps were calculated using three-dimensional (3D) micro-CT images. Data were analyzed using unpaired t- and Kruskal-Wallis tests. A value of P<0.05 was considered significant. RESULTS: None of the tested techniques provided void- or gap-free fillings. Nevertheless, the SAF showed more gap formation than the Revo-S, and TT showed higher gap formation in all experimental groups. These differences, however, were not statistically significant (P>0.05). CONCLUSION: The SAF and Revo-S rotary file systems yielded comparable results. No statistically significant difference was found between the results of the various instrumentation and filling techniques.

Comparison of apical debris extrusion of two rotary systems and one reciprocating system.

BACKGROUND: Postoperative inflammation and endodontic failure occur due to apical extrusion of debris. AIM: To evaluate the amount of apically extruded debris after preparation of straight root canals in extracted human teeth using three rotary systems. MATERIALS AND METHODS: Sixty single-rooted human teeth with single root canal and apical foramen were selected and randomly divided into three experimental groups (n = 20) according to the rotary system used: Group 1 - ProTaper, Group 2 - Revo-S, Group 3 - WaveOne. Apical enlargement was done up to size 40/0.06 for Groups 1 and 2 and 40/0.08 for Group 3. For debris collection, each tooth was held in a preweighed Eppendorf tube fixed inside a glass vial through rubber plug. After instrumentation, each tooth was separated from the Eppendorf tube and the debris adhering to the root surface was collected by washing the root with 1 mL of bi-distilled water and incubated at 70°C for 5 days. The dry weight of extruded debris was weighed in an electronic balance. STATISTICAL ANALYSIS: The mean weights of extruded debris were statistically analyzed using GraphPad prism version 6 and the intergroup comparison was done using unpaired t-test. RESULTS: There was a statistically significant difference in the mean debris score among all the three groups - ProTaper (0.00065 g), Revo-S (0.00045 g) and WaveOne (0.00089 g). CONCLUSION: Revo-S system was associated with significantly less debris extrusion compared with ProTaper or WaveOne.

Stereomicroscopic evaluation of defects caused by torsional fatigue in used hand and rotary nickel-titanium instruments.

OBJECTIVE: The aim of this study was to evaluate defects caused by torsional fatigue in used hand and rotary nickel-titanium (Ni-Ti) instruments by stereomicroscopic examination. MATERIALS AND METHODS: One hundred five greater taper Ni-Ti instruments were used including Protaper universal hand (Dentsply Maillefer, Ballaigues, Switzerland), Protaper universal rotary (Dentsply Maillefer, Ballaigues, Switzerland), and Revo-S rotary (MicroMega, Besançon, France) files. Files were used on lower anterior teeth. After every use, the files were observed with both naked eyes and stereomicroscope at 20× magnification (Olympus, Shinjuku, Tokyo, Japan) to evaluate defects caused by torsional fatigue. Scoring was assigned to each file according to the degree of damage. STATISTICS: The results were statistically analyzed using the Mann-Whitney U test and the Kruskal-Wallis test. RESULTS: A greater number of defects were seen under the stereomicroscope than on examining with naked eyes. However, the difference in methods of evaluation was not statistically significant. Revo-S files showed minimum defects, while Protaper universal hand showed maximum defects. The intergroup comparison of defects showed that the bend in Protaper universal hand instruments was statistically significant. CONCLUSION: Visible defects in Ni-Ti files due to torsional fatigue were seen by naked eyes as well as by stereomicroscope. This study emphasizes that all the files should be observed before and after every instrument cycle to minimize the risk of separation.

Assessment of the fracture resistance of teeth instrumented using 2 rotary and 2 reciprocating files versus the Self-Adjusting File (SAF): An ex vivo comparative study on mandibular premolars.

AIM: Current ex vivo study compared fracture resistance of teeth instrumented using 5 endodontic files, filled with Gutta-percha and AH Plus. MATERIALS AND METHODS: Sixty freshly extracted, single-rooted mandibular premolars were acquired and decoronated to obtain 15 mm segments. These samples were randomly divided into six groups (n = 10). Group 1 served as the control containing untreated samples (without instrumentation or filling). In Groups 2-6, samples were instrumented using rotary (Universal ProTaper and Revo-S), reciprocating (WaveOne and RECIPROC(®)), and self-adjusting file (SAF), respectively. Following instrumentation, the samples were filled by lateral compaction with Gutta-percha and AH Plus. A week later, after the sealer was completely set, a vertical load was applied to the specimen's canal in each group until fracture. The loads required for fracture were recorded, and statistical analysis was performed. RESULTS: The mean fracture load differed significantly among the groups (P < 0.01; one-way ANOVA). Tukey's post-hoc tests revealed that the fracture resistance was similar in the control and SAF groups (P > 0.05) and was significantly higher than that of the 2 rotary and reciprocating groups (P < 0.01). CONCLUSION: The samples instrumented by the SAF exhibited a better fracture resistance.

Evaluation of Time to Fracture and Vertical Forces Applied by a Novel Gentlefile System for Root Canal Preparation in Simulated Root Canals.

INTRODUCTION: A great number of studies performed in the last 3 decades have shown the superior mechanical features of nickel-titanium files as compared with stainless steel files. A novel file system recently developed, Gentlefile, defies these findings and claims to have superior qualities despite the fact it is made from stainless steel. METHODS: Three file systems were used in this experiment: ProTaper Next (X1, X2, and X3), RevoS (SC2, SC3, and AS30), and Gentlefile (GF1, GF2, and GF3). Time to fracture, rotations to fracture, and vertical forces applied to a simulated root canal, which was fabricated from a metal block with a Plexiglas cover, were measured. RESULTS: The GF system required significantly longer time and more rotations to fracture compared with the ProTaper and RevoS systems (P < .001). The GF system applied significantly less vertical force to the canal in comparison with the ProTaper and RevoS systems (P < .01). CONCLUSIONS: Under the limitations of this study the GF system showed better mechanical properties in comparison with the ProTaper and RevoS systems. Further investigation is needed to assess the clinical meaning of these findings.

Shaping Ability of 5(th) Generation Ni-Ti Rotary Systems for Root Canal Preparation in Curved Root Canals using CBCT: An In Vitro Study.

BACKGROUND: Various root canal systems are available commercially with each manufacturer stating superior characteristics of their respective systems. Fifth generation root canal systems claim to have better flexibility and superior debris elimination due to their offset design. This study aims to compare the effects of fifth generation rotary systems on canal curvature, transportation and centering ratio of curved mesial root canals of mandibular molar via cone-beam computed tomographic (CBCT) imaging. MATERIALS AND METHODS: A total of 60 mandibular first molars with an angle of curvature ranging from 20 to 40° of the mesiobuccal root were divided into three groups with 20 canals each. Before instrumentation, the groups were balanced with respect to the angle and radius of canal curvature based on CBCT images taken. All root canals were shaped to an apical size of 25: OneShape (OS) (Micro Mega, Besancon, France), ProTaper Next X2 (PTN) (Dentsply Maillefer), Revo S(RS) (Micro Mega, Besancon, France). CBCT assessment was done post instrumentation. SPSS version 16 software was used for statistical analysis. The significance level was set at P = 0.05. RESULTS: The OS system maintained better canal centricity and less transportation as compared to PTN and RS. There was no significant difference among the three groups in canal curvature after instrumentation. CONCLUSIONS: All file systems used straightened the root canal curvature similarly. OS instrumentation exhibited superior performance compared with the RS and PTN systems with respect to transportation and centering ratio.

Comparative evaluation of root canal preparations of maxillary first molars with self-adjusting file, reciproc single file, and revo-s rotary file: A micro-computed tomography study.

This study was aimed to use micro-computed tomography (µ-CT) to evaluate the canal shaping properties of three nickel-titanium instruments, Self-Adjusting File (SAF), Reciproc, and Revo-S rotary file, in maxillary first molars. Thirty maxillary molars were scanned preoperatively by using micro-computed tomography (µ-CT) scans at 13,68 µm resolution. The teeth were randomly assigned to three groups (n = 10). The root canals were shaped with SAF, Reciproc, and Revo-S, respectively. The shaped root canals were rescanned. Changes in canal volumes and surface areas were compared with preoperative values. The data were analyzed using Kruskal-Wallis and Conover's post hoc tests, with p < .05 denoting a statistically significant difference. Preoperatively canal volumes and surface area were statistically similar among the three groups (p > .05). There were statistically significant differences in all measures comparing preoperative and postoperative canal models (p = 0.0001). These differences occurred after instrumentation among the three experimental groups showed no statistically significant difference for volume (p > .05). Surface area showed the similar activity in buccal canals in each of the three techniques whereas no statistically significant difference was detected among surface area, the SAF, and the Revo-S in the palatal (P) canal. Each of three shaping system showed the similar volume activity in all canals, but SAF and Revo-S provided more effectively root planning in comparison with Reciproc in P canal.

A comparative evaluation of root canal area increase using three different nickel-titanium rotary systems: An ex vivo cone-beam computed tomographic analysis.

BACKGROUND AND OBJECTIVES: The present study was undertaken to compare and evaluate the area increase of root canals with ProTaper, iRaCe and Revo-S systems using cone beam computed tomography for analysis. MATERIALS AND METHODOLOGY: Forty five extracted human mandibular premolars having single canal and straight root were collected. Teeth were randomly assigned to three groups (n=15). Samples were decoronized by maintaining root length at 14 mm. Pre-instrumentation cone beam computed tomography scan was done after stabilizing the samples on wax blocks. The working length was determined at 1 mm short from the apical foramen by using a ISO 15 K-file tip protruding at apical foramen. Preparation was carried out according to the manufacturer's instructions. Finally, canals were instrumented upto 30/.06 apically for each group. After each instrumentation, root canals were irrigated with 2ml of 3% sodium hypochlorite solution followed by 2 ml of 17% EDTA solution. Final irrigation was done with 5ml of saline. Post instrumentation cone beam computed tomography scans of all samples in the 3 groups were acquired. RESULTS: Mean percentage of area increase in different thirds of the canal was highest for ProTaper followed by i-RaCe and Revo-s system which was statistically significant. INTERPRETATION AND CONCLUSION: Root canal area increase was highest for ProTaper followed by i-Race and Revo-S systems.

Effect of ProTaper Universal, Endoflare, Revo-S, HyFlex coronal flaring instruments, and Gates Glidden drills on crack formation.

INTRODUCTION: The aim of the present study was to evaluate crack formation after flaring root canals with Gates Glidden drills and ProTaper Universal (SX; Dentsply Maillefer, Ballaigues, Switzerland), Endoflare (MicroMega, Besançon, France), Revo-S (MicroMega), and HyFlex (Coltene-Whaledent, Allstetten, Switzerland) flaring instruments. METHODS: One-hundred eight mandibular molars were selected. Eighteen teeth were left unprepared to serve as negative controls; the experimental groups consisted of the mesiobuccal and mesiolingual root canals of the remaining 90 teeth, which were instrumented with the following coronal flaring instruments: Gates Glidden drills and ProTaper Universal SX, Endoflare, Revo-S SC1, and HyFlex 25.08 instruments. All roots were then sectioned perpendicular to the long axis at 1, 2, 3, 4, 6, and 8 mm from the cementoenamel junction. The sections were inspected under a stereomicroscope, and any crack formations were recorded. The data were analyzed using the chi-square test (P = .05). RESULTS: The Gates Glidden drills resulted in a higher rate of crack formation than that noted in the control group (P < .05). Flaring of the root canals using the ProTaper Universal, Endoflare, Revo-S, and HyFlex instruments resulted in crack formation similar to that of the control group (P > .05). CONCLUSIONS: The use of the Gates Glidden drills resulted in the formation of the most cracks. However, the results for the ProTaper Universal, Endoflare, Revo-S, and HyFlex flaring instruments were similar to those of the control group in terms of crack formation.

Comparison of cyclic fatigue resistance of nickel-titanium coronal flaring instruments.

INTRODUCTION: The purpose of this study was to compare the cyclic fatigue resistance of coronal flaring instruments. METHODS: Three groups of nickel-titanium (NiTi) endodontic coronal flaring instruments were tested in steel canals with a 3-mm curvature radius and 60° (n = 18) and 45° of curvature (n = 18). The cyclic fatigue of the following NiTi instruments was tested: ProTaper Sx (Dentsply Maillefer, Ballaigues, Switzerland), HyFlex 25.08 (Coltene-Whaledent, Allstetten, Switzerland), and Revo-S SC1 (Micro-Mega, Besancon, France). The length and diameter of the fractured fragment and the total area of the fractured surface of each instrument were measured. The data were then statistically analyzed using a 1-way analysis of variance and the post hoc Tukey test (α = .05). RESULTS: At the 60° of curvature, Revo-S had the highest fatigue resistance, HyFlex had the second highest fatigue resistance, and ProTaper Universal had the least fatigue resistance. At the 45° of curvature, the Revo-S and HyFlex showed superior cyclic fatigue resistance compared with the ProTaper. The length of the fracture fragment of the ProTaper instrument was longer than that of the other groups at the 60° of curvature. At the 45° of curvature, the length of the fracture fragment of the ProTaper and HyFlex instruments was longer than that of Revo-S. The mean diameter and surface area of the HyFlex instruments in the fractured part was higher than that of other groups at both angles of curvature. CONCLUSIONS: The Revo-S SC1 and HyFlex 25.08 instruments showed better cyclic fatigue resistance than the ProTaper Sx instrument.

Weight of apically extruded debris following use of two canal instrumentation techniques and two designs of irrigation needles.

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