Root Canal Shaping Using Nickel Titanium, M-Wire, and Gold Wire: A Micro-computed Tomographic Comparative Study of One Shape, ProTaper Next, and WaveOne Gold Instruments in Maxillary First Molars

Shaping ability of three instrumentation system in moderately curved canals: A micro-CT study

This study aims to compare the shaping ability of three systems using micro-computed tomography (micro-CT). Moderately-curved mesial canals of 36 mandibular molars were assigned to three groups (n = 24); Protaper Next (PTN, 0.25, 0.06), WaveOne Gold (WOG, 0.25, 0.07), TruNatomy (TRN, 0.25, 0.04), and instrumentation was performed. Pre- and post-micro-CT scans were obtained. Canal volume and surface, structure model index (SMI), centroid shift, canal transportation, and untouched canal were analyzed. One-way ANOVA and Student's t-test were used for statistics. There was no difference in SMI, centroid shift, and centering ability between the study groups (p > .05). Removed dentin and canal surface changes were lower in TRN, while untouched dentin walls were higher (p < .05). Cross-sections became more rounded (p < .05), but not significant between groups (p > .05). Considering the removed dentin by TRN, it can be used in critical dentin thickness, such as the danger zone (DZ). PTN, WOG, and WOG kept the original canal course similarly. Untouched dentin by TRN (41%) was wider than PTN and WOG, consequently, meticulous irrigation is recommended. TRN, which provides a controlled increase in canal volume, can be used in thin dentin such as the DZ, however, its use should be supported by copious irrigation and brushing considering the rate of untouched dentin walls. RESEARCH HIGHLIGHTS: TRN presented a higher untouched dentin wall compared to PTN and WOG. Canal volume and surface changes were the lowest in the TRN group. The centering abilities were similar in PTN, WOG, and TRN.

Comparative evaluation of remaining dentin thickness, canal centering ability and apical deformity between ProFit S3 and Protaper gold - A nano CT study

Purpose

For the root canal treatment to be successful, the root canal system must be cleaned and shaped, and must be gradually widened from the apical to the coronal region in order to preserve dentin thickness. ProFit S3 (Profit Dental, India) patented rotary file with variable taper design preserves dentin. The study employs ultra-high-resolution nano-computed tomography to assess the volumetric changes of two new rotary files in permanent mandibular premolars.

Materials and methods

Based on inclusion and exclusion criteria, this in-vitro investigation used extracted premolars. Before the pre-operative scan, samples were made and the working length was determined using a high-precision nano-CT (SkyScan 2214, Bruker, Kontich, Belgium). A single skilled pediatric dentist used ProFit S3 (Profit Dental, India) and Protaper Gold (PTG; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) to prepare the canals. Post-op scans were similar to pre-ops. For 3D root canal visualization and analysis, NRecon software was used to rebuild images.

Results

Profit S3 has a mean value of 0.65500 and Protaper gold 1.38800, indicating a significant range. Protaper gold followed Profit S3 in canal volume differential. The two rotating file systems differed significantly (p 0.05). ProFit S3 maintained mesiodistal and buccolingual dentin thickness at 4 mm, 8 mm, and 12 mm, followed by Protaper Gold.

Conclusions

ProFit S3 exhibited the lowest mean canal volume difference compared to Protaper gold. Unlike Protaper Gold, ProFit S3 offers a variable taper design that preserves root canal anatomy, peri cervical dentin, and dentin thickness.

Influence of two kinematics on canal transportation and centering ability of WaveOne Gold and One Curve files

This research examines canal transportation and centering ability of single-file systems when operated in continuous rotation or reciprocation. Sixty J-shaped resin blocks were used. The specimens were divided into two main groups (n = 30). Then, based on the motion used to operate the instruments, each group was subdivided into two subgroups (n = 15). Group A1: One Curve/rotation, Group A2: One Curve/clockwise reciprocation, Group B1: WaveOne Gold/Reciprocation, Group B2: WaveOne Gold/counter-clockwise rotation. Pre- and post-instrumentation images were obtained using digital microscope. Canal transportation was measured at five levels. A non-significant difference (p > 0.05) resulted between two motions at all levels. However, group A1 showed significantly less transportation at levels 3 and 4 (p ≤ 0.05), also more centered preparation at level 4 (p ≤ 0.05) than group B1. Within the limitations of this study, the apical transportation and centering ability of single-file systems are unaffected by different kinematics.

Shaping Efficiency of Rotary and Reciprocating Kinematics of Engine-driven Nickel-Titanium Instruments in Moderate and Severely curved Root Canals Using Microcomputed Tomography: A Systematic Review of Ex Vivo Studies

INTRODUCTION

This systematic review aimed to compare reciprocating with continuous rotary instrumentation kinematics, by means of microcomputed tomography evaluations, in extracted human permanent teeth with moderate and severe canal curvatures.

METHODS

The research protocol was registered in the International Prospective Register of Systematic Reviews and given the reference number CRD42023404035. An electronic search was undertaken in MEDLINE (PubMed), EBSCO, Scopus, Web of Science databases until December 2021. Manual screening of issues in endodontic journals and references of relevant articles were assessed individually. The risk of bias (RoB) of the included articles was evaluated with the QUIN tool (Quality Assessment Tool for In Vitro Studies).

RESULTS

Among 1640 retrieved articles, 49 were included in the qualitative synthesis. Fifteen articles had low RoB, 33 articles had medium RoB, and only 1 study was at high RoB. Continuous rotary systems had better centering ability in both moderate and severe canal curvatures and resulted in less apical transportation in severely curved root canals. None of the kinematic systems was capable of instrumenting the entire canal surface area. Reciprocating kinematics systems tended to provide higher increase in surface area of severely curved canals and produced fewer dentinal microcracks in moderately curved canals.

CONCLUSIONS

The evidence presented in this review suggests that continuous rotary system seems to be better than reciprocating system in solving the major issues encountered during root canal instrumentation of extracted teeth with moderate and severe curvatures.

Can the detection of second mesiobuccal canals be enhanced based on the volume of adjacent canals?

OBJECTIVES

The purpose of this study was to evaluate whether the presence of the second mesiobuccal (MB2) canal is related to volumetric differences on the adjacent canals of maxillary molars.

DESIGN

Forty-seven maxillary first and second molars with and without the MB2 canal were individually scanned using microcomputed tomography (micro-CT). The volume of each canal was measured by an evaluator with experience in micro-CT analysis. The intraclass correlation coefficient (ICC) was obtained. Multiple logistic regression and odds ratio was calculated. To compare the volume of canals in molars with and without MB2, the Mann-Whitney test was applied (α = 0.05).

RESULTS

The intra-examiner reproducibility was almost perfect (ICC=0.97). Multiple logistic regression demonstrated that the volume of the mesiobuccal (MB1) canal can possibly act as a predictor of the presence of the MB2 canal. It was also found that the MB1 canal volume is larger in molars without the MB2 canal (p = 0.01). No statistically significant difference was observed in the adjacent canals (p > 0.05).

CONCLUSIONS

Despite the challenging detection of the presence of MB2 canals, clinicians should be aware that MB1 canals of reduced volume are highly suggestive of their presence.

Mechanical performance of original; yellowish and blueish ProFile instruments: isolating heat-treatment as a variable

The present study aimed to perform two different heat-treatments in an austenitic NiTi ProFile instrument and to compare the mechanical performance of original and heat-treated instruments. Heat treatment of ProFile (tip size 25 and 0.06 taper) instruments were carried out in a furnace in argon atmosphere using a heating rate of 10° C/min. After reaching the programmed temperatures of 450 ºC or 500 ºC the system remained at a constant temperature for 10 minutes; followed by cooling in water at room temperature. Afterwards; the three groups (n=30 per group) of instruments were compared regarding their cyclic fatigue (n=10 per group); bending (n=10 per group); and buckling resistance (n=10 per group). After cyclic fatigue tests; a scanning electron microscope was used to analyze the fracture surfaces and observe the fracture mode. Statistical analysis was performed using One-way ANOVA and Student-Newman-Keuls test; with an alpha type error set at 0.05. Yellowish and blueish coloration was observed in the ProFile instruments after 450 ºC or 500 ºC heat treatments; respectively. Conventional ProFile instruments showed the lower cyclic fatigue; and the higher bending and buckling resistance (P<0.05). In contrast; yellowish ProFile instruments (heat treated at 500° C) showed the higher cyclic fatigue; and the lower bending and buckling resistance (P>0.05). It can be concluded that the different heat treatments performed on ProFile instruments increased its cyclic fatigue resistance and improved the flexibility and buckling resistance.

Comparative Analysis of Root Canal Dentin Removal Capacity of Two NiTi Endodontic Reciprocating Systems for the Root Canal Treatment of Primary Molar Teeth. An In Vitro Study

The objective of the present study was to evaluate and compare the dentin removal capacity of Endogal Kids and Reciproc Blue NiTi alloy endodontic reciprocating systems for root canal treatments in primary second molar teeth via a micro-computed tomography (micro-CT) scan. Materials and Methods: Sixty root canal systems in fifteen primary second molar teeth were chosen and classified into one of the following study groups: A: EK3 Endogal Kids (n = 30) (EDG) and B. R25 Reciproc Blue (n = 30) (RB). Preoperative and postoperative micro-CT scans were uploaded into image processing software to analyze the changes in the volume of root canal dentin using a mathematical algorithm that enabled progressive differentiation between neighboring pixels after defining and segmenting the root canal systems in both micro-CT scans. Volumetric variations in the root canal system and the root canal third were calculated using a t-test for independent samples or a nonparametric Mann–Whitney–Wilcoxon test. Results: Statistically significant differences (p = 0.0066) in dentin removal capacity were found between the EDG (2.89 ± 1.26 mm³) and RB (1.22 ± 0.58 mm³) study groups for the coronal root canal third; however, no statistically significant differences were found for the middle (p = 0.4864) and apical (p = 0.6276) root canal thirds. Conclusions: Endogal and Reciproc Blue NiTi endodontic reciprocating systems showed similar capacity for the removal of root canal dentin, except for the coronal root canal third, in which the Reciproc Blue NiTi endodontic reciprocating system preserved more root canal dentin tissue.

Morphological characteristics of the mesiobuccal root in the presence of a second mesiobuccal canal: a micro-CT study

Objectives

This study investigated the internal morphology of mesiobuccal (MB) roots of maxillary molars with a second mesiobuccal (MB2) canal.

Materials and Methods

Forty-seven maxillary first or second molars from Brazilians were scanned using micro-computed tomography. The following measurements were obtained from the MB roots: root thickness, root width, and dentin thickness of the buccal aspect of the first mesiobuccal (MB1) canal, between the MB1 and MB2 canals, and the palatal aspect of the MB2 and MB1 canals at 3 mm from the root apex and in the furcation region. For statistical analysis, the Student’s t-test and analysis of variance with the post-hoc Tukey test were used (α = 0.05).

Results

In maxillary molars with an MB2 canal, MB roots were significantly thicker (p = 0.0014) and narrower (p = 0.0016) than in maxillary molars without an MB2 canal. The dentin thickness of the palatal aspect of the MB1 canal was also significantly greater than that of MB roots without an MB2 canal at 3 mm from the root apex (p = 0.0007) and in the furcation region (p < 0.0001). In the furcation region of maxillary molars with an MB2 canal, the dentin thickness between the MB1 and MB2 canals was significantly smaller than that in the buccal and palatal aspects (p < 0.0001).

Conclusions

The internal morphology of MB roots of maxillary molars with an MB2 canal revealed differences in dentin thickness, root diameter, and distance between the canals when compared with maxillary molars without an MB2 canal.

Shaping ability of four single-file systems in the instrumentation of second mesiobuccal canals of three-dimensional printed maxillary first molars

Background

This study evaluated and compared the shaping ability of four advanced single-file nickel-titanium (NiTi) systems during the preparation of curved second mesiobuccal (MB2) canals in maxillary first molar replicas fabricated by three-dimensional (3D) printing via micro-computed tomography (Micro-CT) imaging.

Methods

A total of 60 3D-printed maxillary first molar replicas were constructed from one extracted tooth, with an angle of curvature ranging from 15° to 25°. The MB2 canals from these 60 replicas were divided into 4 groups of 15 replicas according to the canal instrumentation system used, namely, Waveone gold (WOG), Reciproc blue (RCB), XP-endo shaper (XPS) and M3-L. The specimens were scanned before and after preparation using Micro-CT. The pre- and post-instrumentation images of each specimen were superimposed, and the amount of resin removed, the change in surface area, the canal transportation, and centering ability were assessed using the Mimics software. Instrumentation time was also recorded. One-way analysis of variance and least significant difference (LSD) tests were used to statistically compare the groups. The significance level was set at 5%.

Results

Instrumentation time with M3-L was significantly longer than the other systems (P<0.05). The amount of resin removed and the change in surface area generated by the 4 systems were different at the apical, middle, and coronal thirds, and the total canal (P<0.05). Overall, WOG and XPS resulted in the less change than RCB and M3-L. There was no significant difference among the groups at the middle third regarding canal transportation and centering ability (P>0.05). However, a significant difference was found at the apical level (P<0.05), where RCB showed the poorest centering ability and the highest canal transportation (P<0.05). In addition, XPS resulted in the least canal transportation (P<0.05) at the coronal level, while there was no significant difference between the four groups in terms of centering ability.

Conclusions

The M3-L instrument required more time to prepare the curved MB2 canals compared with the other systems. Overall, WOG and XPS showed the least resin removal and surface area change. M3-L, XPS, and WOG instruments respected the original canal curvature better than RCB files.

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.

Postoperative Pain after Use of the WaveOne Gold and XP-endo Shaper Systems: A Randomized Clinical Trial

INTRODUCTION

The present study aimed to clinically compare the incidence of postoperative pain after endodontic treatment of posterior teeth using the WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland) and XP-endo Shaper (XPES; FKG Dentaire, La Chaux-de-Fonds, Switzerland) systems.

METHODS

In a single-blind randomized clinical trial, 148 vital teeth with an indication for conventional endodontic therapy for prosthetic purposes were treated by 5 specialists following a preestablished protocol. All participants were unaware of the treatment they received. The teeth were randomly divided into 2 groups (n = 74) according to the instrumentation system used (the WOG group and XPES group). The treatments were performed in a single session. The participants were asked to rate the intensity of postoperative pain on a visual analog scale (no pain, mild pain, moderate pain, and severe pain) after 24, 48, and 72 hours and 7 days.

RESULTS

The incidence of postoperative pain was higher in the XPES group after 24, 48, and 72 hours compared with those in the WOG group (P < .05). Two participants in the WOG group experienced severe postoperative pain after 24 hours. None of the participants in either group reported pain after 7 days (P > .05, Mann-Whitney test).

CONCLUSIONS

Postoperative pain is expected after preparation of the root canal system with the WOG and XPES systems tested, but it only persists for a short period. Although more common after the use of the XPES system, the pain was classified as mild at all time points.

Shaping ability of a new heat-treated NiTi system in continuous rotation or reciprocation in artificial curved canals

The purpose is to evaluate canal transportation of a new heat-treated NiTi system, the Endostar E3 Azure operated in continuous rotation or reciprocation. 40 resin blocks were divided into two groups. The first was shaped in continuous rotation while the second in reciprocation. A preoperative and two postoperative images were taken, one after the use of the 20/06 and one after the 25/06. The images were superimposed to determine canal transportation. Time required for canal shaping was recorded. One-sample and student t tests, repeated-measure analyses of variance, univariate analyses and Bonferroni multiple comparisons tests were used for statistical analysis. The significance level was set at p < 0.05. There was no significant difference between continuous and reciprocating motion with the 20/06 and 25/06, respectively, at 1 mm (p = 0.761, p = 0.559), 2 mm (p = 0.584, p = 0.810) and 3 mm (p = 0.651, p = 0.070). The reciprocating motion showed significantly less canal transportation at 5 mm (p = 0.049, p < 0.001) and 7 mm (p < 0.001, p < 0.001) for the 20/06 and 25/0.6. Continuous rotation was more time-consuming than reciprocation (p < 0.001). The Endostar E3 Azure in reciprocation respected the original canal curvature better than in continuous rotation at all levels, and required less time to prepare artificial curved canals. Endodontists should know the shaping abilities of novel heat-treated NiTi files, regarding canal transportation and its relation with the instruments' motion and apical diameter enlargement.

Shaping ability of three thermally treated nickel-titanium systems in S-shaped canals

This study aimed to compare the shaping ability of ProTaper Next (PTN), HyFlex EDM (HEDM) and One Curve (OC) systems manufactured via different thermal treatment methods in simulated S-shaped canals. Sixty S-shaped canals in clear resin blocks were enlarged to a final apical size of 25 using PTN, HEDM and OC instruments (n = 20 canals/group). Composite images were obtained by superimposing pre- and post-preparation images. The amount of removed resin was measured perpendicularly to the canal surface in 22 points. Prepared canal width and canal transportation at different levels were determined. Canal aberrations were also recorded. Data were statistically analysed using analysis of variance, the Kruskal-Wallis and the chi-square tests at a 0.05 significance level. OC produced the most conservative enlargement and better maintained particularly the apical curvature of the S-shaped canals than HEDM and PTN. OC and HEDM better maintained the canal terminus and coronal curvature than PTN.

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

INTRODUCTION

This 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.

METHODS

Sixty 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%.

RESULTS

There 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).

CONCLUSIONS

WG 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.

Assessment of root canal transportation of 2Shape and ProTaper gold in mandibular molar mesial canals: A micro-computed tomographic study

The aim of this study was to compare shaping abilities of Protaper Gold® (PTG) and 2Shape® (TS) by using a new automatic process and micro-computed tomography (Micro-CT). 32 first mandibular molars with two separate mesial canals were selected. Only mesial roots were prepared with PTG and TS. Pre- and post-operative scans were performed using Micro-CT to provide volumes with a voxel size of 20 μm. Volumes, non-instrumented area, amount of transportation and centering ability in coronal, middle and apical third shaping time and procedural errors were recorded. TS and PTG increased the endodontic volume of 2.98 mm³ (±1.56) and 3.21 mm³ (±1.78) respectively with no statistical difference (p = .168) and no procedural errors. No significant difference was found concerning canal transportation among groups but only within the same group PTG (p value < .001) and TS (p value < .001). The mean centering ratio was significantly different only between the section levels for PTG (p value < .001) and TS (p value = .01); it was significantly reduced in the cervical third. The percentage of untouched canal walls ranged between 29.78% (±15.145) and 36.60% (±11.968) respectively for PTG and TS with no statistical difference among groups (p value = .168). TS and PTG with post machining heat treatment were able to produce centered preparations with no significant difference or procedural errors. TS system provided a shorter preparation time than PTG files.

Root Canal Transportation after Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files

Background: Root canal preparation during endodontic treatment may be associated with various complications, including a change in the original pathway of the root canal lumen. The aim of our study was to determine whether files of similar sizes that use various movement kinematics (rotary, reciprocal, adaptive motion) cause root canal transportation, and whether the differences between such systems are statistically significant. Methods: The degree of root canal transportation (DT) was calculated with the use of computed tomography scans for 3 groups of teeth (for each group: n = 20) in which the root canals were prepared using either rotary (ProTaper Next—PTN), reciprocal (WaveOne Gold—WOG), or adaptive movement (Twisted Files—TF) instruments. Results: For rotary ProTaper Next instruments, the mean value of the DT index was 0.0795 (SD = 0.0179) for 3 mm from the apex, 0.09 (SD = 0.0262) for 6 mm from the apex, and 0.106 (SD = 0.0221) for 9 mm from the apex. For reciprocal WaveOne Gold Primary instruments, the mean value of the DT index was 0.0355 (SD = 0.015) for 3 mm from the apex, 0.061 (SD = 0.02) for 6 mm from the apex, and 0.08 (SD = 0.25) for 9 mm from the apex. For Twisted Files, the mean value of the DT index was 0.05 (SD = 0.03) for 3 mm from the apex, 0.092 (SD = 0.17) for 6 mm from the apex, and 0.08 (SD = 0.02) for 9 mm from the apex. Conclusions: The use of PTN, WOG, and TF files resulted in root canal transportation to a different degree. The use of rotary PTN files produced the most transported preparation, whereas the use of WOG files produced the conservative root canal preparation that allowed the retention of the original shape of the root canal.

Comparison of Canal Transportation and Centering Ability of ProGlider and WaveOne Gold Glider in Curved Canals

OBJECTIVES

 The aim of this study was to compare the volume variation and maintenance of the root canal position when using the ProGlider 16.02 (PG) and the WaveOne Gold Glider 15.02 (WOGG) file systems for glide path preparation.

MATERIALS AND METHODS

 Twenty-four moderately curved mesiobuccal canals of maxil-lary first molars were selected and randomly divided into two groups: PG and WOGG. The selected teeth were scanned using microtomography before and after root canal preparation to assess centralization and linear transport at 1, 3, 5, and 7 mm from the apical foramen.

STATISTICAL ANALYSIS

 The data were analyzed with the Mann-Whitney U test. The level of significance was 5%.

RESULTS

 There were no significant differences in volume variation or root canal transport (p > 0.05). There was a significant difference in the centralization of the root canal at 3 mm from the foramen (p < 0.05).

CONCLUSIONS

 WOGG and PG instruments presented similar results regarding the root canal volume increase and transport. WOGG caused higher decentralization at 3 mm from the apical foramen.

Influence of Negotiation, Glide Path, and Preflaring Procedures on Root Canal Shaping-Terminology, Basic Concepts, and a Systematic Review

INTRODUCTION

Negotiation, glide path, and preflaring are essential steps in root canal shaping procedures. This report aimed to discuss the terminology, basic concepts, and clinical considerations of negotiation, glide path, and preflaring procedures and the influence of these steps on root canal shaping.

METHODS

This systematic review was undertaken following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol has been registered with the International Prospective Register of Systematic Reviews (number CRD42019127021). A comprehensive literature search was performed by 2 independent reviewers using a selected search strategy in 2 electronic databases (PubMed and Scopus) until January 28, 2019. A further search was performed manually in endodontic journals. Studies investigating or comparing at least 1 shaping property resulting from root canal instrumentation with a glide path or preflaring in human extracted teeth or clinical studies were included.

RESULTS

The literature shows that the definition of glide path and preflaring procedures remains controversial, which requires an elaboration in the American Association of Endodontists' Glossary of Endodontic Terms. After the removal of irrelevant and duplicated articles, 98 articles were included. The impact of glide path preparation and preflaring on working length determination, apical file size determination, canal transportation, separation of endodontic files, shaping time, dentinal microcrack formation, and extrusion of debris was discussed. Because of heterogeneity among the included studies, quantitative synthesis was not performed for most of the parameters.

CONCLUSIONS

An evidence-based guideline is needed to define and correlate the basic concepts and current applications of each step of contemporary advancements in root canal instruments. Glide path preparation reduces the risk of debris extrusion, has no influence on the incidence of dentinal crack formation, and improves the preservation of the original canal anatomy. The creation of a glide path may have no impact on Reciproc files (VDW, Munich, Germany) in reaching the full working length. Preflaring increases the accuracy of working length determination. Further randomized clinical trials are required to evaluate the effect of a glide path and preflaring on root canal treatment outcomes.

The retreatment abilities of ProTaper Next and F6 Skytaper: a micro-computed tomography study

Purpose

The aim of this study was to evaluate the retreatment abilities of the ProTaper Next (PTN) and F6 SkyTaper (F6) systems by using micro-computed tomography (microct), radiographic and microscopic imaging techniques.

Materials and methods

The root canals of twenty-six extracted mandibular premolar teeth were prepared and obturated. For the retreatment procedure, the teeth were randomly divided into two equal groups according to endodontic instruments: PTN (X4) and F6 (#40/.06). Pre- and post-operative filling material volumes were measured with micro-ct, and areas were measured with radiographic and microscopic imaging techniques. The percentages of residual material were calculated, and then statistically compared. The significance level was set at p<0.05.

Results

There was no statistically significant difference between F6 and PTN for retreatment efficacy in the micro-ct and radiographic imaging techniques (p>0.05). PTN demonstrated better cleaning ability when evaluated by microscopic imaging. (p<0.05). The correlation was moderate between micro-ct and radiographic, and micro-ct and microscopic imaging groups; however, it was strong between radiographic and microscopic imaging methods.

Conclusion

The PTN and F6 files had similar effects in the removal of filling material with microct evaluation. The radiographic imaging method gave similar results with micro-ct imaging.

Shaping Ability of XP Endo Shaper File in Curved Root Canal Models

The aim of this study was to assess the shaping ability of the XP Shaper (XPS) file in severely curved canal models under simulated body temperature and compare it with that of the WaveOne Gold (WOG) file. Ninety-six simulated root canals were equally distributed into XPS and WOG systems to be shaped by eight files each. Files were assessed under a stereomicroscope prior to canal shaping to detect deformation if any. The canals were shaped at 35 ± 1°C using the X-Smart Plus motor. Images of the canals were obtained before and after instrumentation using a stereomicroscope to measure the amount of removed resin from both the inner and outer curvature sides at apex (0 mm) and 3 mm and 6 mm from the apex. The shaping time was calculated. The data were statistically analyzed by the independent t-test at 5% significance level. The XPS and WOG systems shaped the canals in 37.0 ± 9.5 and 62.6 ± 11.3 seconds (P < 0.05), respectively. At the apex level, the amount of resin removal in both sides did not show a significant difference between the tested groups (P > 0.05). At 3 mm and 6 mm levels, the WOG removed more resin than XPS at both sides (P < 0.05). In XPS, deformation was observed in four files: one file after the first use, one file after the fourth use, and two files after the sixth use. In WOG, two files were deformed: one file after the fifth use and one file after the sixth use. One XPS file was fractured after the sixth use. In short, XPS and WOG files can be used in shaping severely curved canals as they showed the ability to maintain the original shape with minimal transportation. Both file systems showed signs of deformation after use with a lower number of deformed files observed in WOG throughout the experiment.

Comparison of Shaping Ability of Different Single-File Systems Using Microcomputed Tomography

OBJECTIVES

 To evaluate the shaping ability of four different single-file systems using micro-computed tomography (micro-CT).

MATERIALS AND METHODS

 Eighty mesiobuccal and mesiolingual canals of permanent mandibular molars were randomly assigned to four groups according to the file used; WaveOne Gold, RECIPROC Blue, HyFlex EDM, and One Shape (n = 20). The samples were scanned using micro-CT for the preinstrumentation record; then the canals were instrumented and scanned for the postinstrumentation records.

STATISTICAL ANALYSIS

 The data were then analyzed statistically using one-way analysis of variance (ANOVA) with the level of significance set at α = 0.05.

RESULTS

 The results of canal centering ratio and canal transportation showed that no significant difference was found among the four file groups at the middle and the coronal levels. However, a significant difference was found at the apical level (p < 0.05), where WaveOne Gold showed the best centering ratio and the least amount of canal transportation. The change in the canal volume was significant at the coronal level (p < 0.05), whereas the change in the canal volume was higher for the HyFlex EDM group than the other groups. No significant difference was found between the other groups at the apical level, middle level, or in the total percentage of canal volume.

CONCLUSION

 WaveOne Gold produced a more centralized canal preparation with a lesser amount of transportation at the apical level. HyFlex EDM showed the highest canal volumetric change at the coronal level. The interim design of the endodontic files has a high impact on the behavior of the file inside the root canal.

Canal transportation and centering ratio after preparation in severely curved canals: analysis by micro-computed tomography and double-digital radiography

OBJECTIVES

This study compared canal transportation and centering ratio produced after instrumentation with a single heat-treated reciprocating system, WaveOne Gold (WOG; Dentsply Sirona, Tulsa, OK, USA) and a single heat-treated rotary instrument, XP-endo Shaper (XPS; FKG, La Chaux-de-Fonds, Switzerland), using micro-computed tomographic (micro-CT) imaging, and evaluated the ability of double-digital radiography (DDR) to detect canal transportation.

MATERIALS AND METHODS

Mesial root canals of mandibular molars with severe curvature (25-70°) were randomly assigned to either WOG or XPS groups for preparation. Centering ratio was measured by micro-CT imaging, while canal transportation was measured by micro-CT and DDR methods at 3, 5, and 7 mm from the apex. Data were statistically compared between groups using the t test (α = 5%).

RESULTS

The micro-CT method showed that XPS's shaping ability regarding the centering ability (P = 0.030) and canal transportation (P = 0.028) was significantly better than WOG only at the 7-mm level. The DDR technique detected no difference in canal transportation between groups at any level (P > 0.05); however, a significant difference between evaluation methods was detected at the 5-mm level in the WOG group (P = 0.023).

CONCLUSIONS

Micro-CT technique revealed a significantly better centering ability and less canal transportation with XPS compared to WOG. The DDR technique was not capable of detecting the significant difference between the tested groups.

CLINICAL RELEVANCE

Root canal curvatures may lead to procedural errors during endodontic treatment. Thus, differences on the shaping ability of single heat-treated reciprocating and rotary systems should be known.