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

Investigation of four nickel titanium endodontic instruments, with cyclic fatigue resistance, scanning electron microscopy, and energy dispersive x-ray spectroscopy

The aim of this study was to compare of four different nickel-titanium (Ni-Ti) endodontic files and evaluate in terms of cyclic fatigue resistance and metallurgical properties. Four different type Ni-Ti root canal files Protaper Next X2 (PTN) (Dentsply Maillefer, Ballaigues, Switzerland), One Curve (OC) #25.06 (Micro Mega, Besancon, France), EndoPlus Flex Plus Gold X2 (EPG) (Turkuaz Dental, Denizli, Turkey), and EndoPlus Flex Plus Blue #25.06 (EPB) (Turkuaz Dental, Denizli, Turkey) files were tested for cyclic fatigue resistance (n = 20). During experiments artificial zirconia block canal was used. The artificial canal designed with curvature 60° and 5-mm radius. The number of cyclic to fracture (NCF) was noted. Fractured length (FL) parts of Ni-Ti files were recorded to assessment of fracture volumetric point. All fractured surfaces of Ni-Ti files were assessed by scanning electron microscope (SEM) to confirm the type of fractures. Descriptive evaluation become accomplished for the fundamental composition of units with the aid of using energy-dispersive x-ray spectroscopy (EDX). NCF data were evaluated via Bonferroni test with post hoc multiple comparison method. OC showed the highest NCF values (p < .05). The standardization of the study was confirmed as the FL of files was statistically similar in length (p > .05). SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. EDX analysis confirmed that EPB established the poorest Ni content file. RESEARCH HIGHLIGHTS: The cyclic fatigue-related failure of One Curve was significantly more resistant than Protaper Next and EndoPlus files. Scanning electron microscopy images showed that One Curve and Protaper Next have round tips Energy dispersive x-ray spectroscopy showed that all four endodontic instruments mainly have Nickel and Titanium elements.

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.

Evaluation of Minimally Invasive Preparation of Curved Mesial Canals of Mandibular Molars - An In Vitro Study

INTRODUCTION

Curved mesial roots can be challenging for different stages of endodontic treatment. Preparation aims to enlarge, clean, and shape the root canal system, and hundreds of systems are available to carry it out. Aiming to maintain pericervical dentin, minimally invasive preparation was proposed, and with it, instruments with lower tapers emerged. This study aimed to evaluate the increase in canal volume, the centering ability of the instruments, and root canal transportation of two different rotary systems with lower tapers.

METHODS

Eighteen curved mesial roots of extracted mandibular molars were scanned by micro-CT at 3 moments: initial and after the 2 stages of endodontic preparation. The canals were prepared using TruNatomy (TN) and ProDesign Logic 2 (PDL2) instruments up to sizes 25.04 and 26.04, respectively, and after 36.03 and 35.05, respectively. The data were analyzed using parametric and nonparametric tests with a significance level of 5%.

RESULTS

TN and PDL2 systems showed no difference regarding the increase in the volume of the canals with the first instruments, but after preparation with a diameter size of 35 or 36, there was a difference (P < .01) between the systems in the cervical and middle thirds.

CONCLUSION

Both systems shaped the mesial canals of mandibular molars while keeping low transportation and good centering ability in enlargements up to diameter size 35 or 36 with tapers of 3 or 5%.

A Comparative Evaluation of the Efficiencies of Different Rotary File Systems in Terms of Remaining Dentin Thickness Using Cone Beam Computed Tomography: An In Vitro Study

AIM

The aim of this study was to evaluate and compare the dentin thickness of the mesio-buccal canal of the lower first molar after canal preparation with three different rotary file systems using cone beam computed tomography (CBCT).

METHODOLOGY

TruNatomy (Dentsply Sirona, USA), 2Shape (Micro-Mega, France), and One Curve (Micro-Mega, France) were the three different rotary files that were employed. A total of 45 excised human permanent first mandibular molars were divided into Groups A (TruNatomy), B (2Shape), and C (One Curve) at random. To measure the residual dentin thickness at 3 mm, 5 mm, and 7 mm from the radiographic apex, the mesial root of the tooth was removed from the tooth, and a mesio-buccal canal was taken. Samples were mounted in clear acrylic resin and were subjected to a pre-instrumentation CBCT scan. The mesio-buccal canal was cleaned and shaped while maintaining the final mesio-buccal canal preparation of Group A - 26/0.04, Group B - 25/0.04, and Group C - 25/0.04. The samples were extensively irrigated with 3% sodium hypochlorite and 17% EDTA, and a post-instrumentation scan was performed on them. Statistics were used to determine the values from CBCT scans that were recorded for pre- and post-instrumentations.

RESULTS

The results showed that Group A had the greatest drop in dentin thickness, followed by Group B and Group C. The change in dentin thickness was greatest at 3 mm and 7 mm.

CONCLUSION

In contrast to TruNatomy and 2Shape rotary file systems, One Curve has the advantage of maintaining a tooth's thickness at 3 and 7 millimeters from the radiological apex. Since the TruNatomy file system removes more dentin than the other two combined, it should be used cautiously. Choosing the right instrument is crucial for cleaning and shaping during root canal preparation.

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.

Three-Dimensional Printed Teeth in Endodontics: A New Protocol for Microcomputed Tomography Studies

This study aimed to describe a support material removal protocol (SMRP) from inside the root canals of three-dimensional printed teeth (3DPT) obtained by the microcomputed tomography (microCT) of a natural tooth (NT), evaluate its effectiveness by comparing the 3DPT to NT in terms of internal anatomy and behaviour toward endodontic preparation, and evaluate if 3DPT are adequate to assess the differences between two preparation systems. After the SMRP, twenty 3DPT printed by PolyJet™ were microCT scanned before preparation and thereafter randomly assigned into two groups (n = 10). One group and NT were prepared using ProTaper Gold® (PTG), and the other group with Endogal® (ENDG). MicroCT scans were carried out after preparation, and the volume increase, volume of dentin removed, centroids, transportation, and unprepared areas were compared. For the parameters evaluated, no significant differences were found between the 3DPT and NT before and after preparation (p > 0.05), and no significant differences were found between the 3DPT PTG group and the 3DPT ENDG group (p > 0.05). It can be concluded that the SMRP described is effective in removing the support material SUP706B™. PolyJet™ is adequate for printing 3DPT. Furthermore, 3DPT printed with high-temperature RGD525™ have similar behaviour during endodontic preparation with PTG as the NT, and 3DPT can be used to compare two preparation systems.

Microcomputed tomographic evaluation of 6 NiTi files on the pericervical dentin and the smallest dentin thickness zones in mesial root canals of mandibular molars: an in vitro study

OBJECTIVE

The aim of this study was to evaluate six files on the pericervical dentin (PCD) and the smallest dentin thickness zones (SDTZ) in mesial root canals of mandibular molars.

MATERIALS AND METHODS

Sixty mandibular molars with two mesial canals and Vertucci configuration were aleatory allocated in 6 experimental groups of 10 molars and 20 root canals. Specimens were scanned before instrumentation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WaveOne Gold (WG), group 2 with Reciproc Blue (RB), group 3 with TRUShape (TS), group 4 with XP-endo Shaper (XP), group 5 with iRace (IR), and group 6 with TruNatomy (TN). After instrumentation, the molars were scanned again and the images recorded were reconstructed with the NRecon v.1.7 (Bruker micro-CT) and analyzed with CTAn v.1.20.8 software (Bruker micro-CT) quantifying the changes produced in the surface, volume, structure thickness, SMI, and centroids at the Pericervical Dentin area of the root canals (PCD) located from the root canal orifices at the floor of the pulp chamber to 4 mm in the apical direction, and the changes in the Smallest Dentin Thickness Zones (SDTZ) located (from the furcation to 4 mm and 7 mm in the apical direction. The data obtained were compared using Wilcoxon and ANOVA with a 5% significance level.

RESULTS

XP and TN were similar in all the parameters (P >.05) at the PCD, but TN showed significant differences from WG, RB, TS, and IR (P <.05), while XP showed significant differences from WG (P <.05) in volume, surface, and structure thickness. Regarding the changes in the SDTZ, the amount of dentin removed was similar between the groups in both canals at the middle 1/3, at the cervical 1/3 for MB canals, and in ML canals for RB, TS, XP, IR, and TN (P>.05). The action of WG was significantly different from that of XP and TN in the cervical 1/3 of the ML canal (P <.05).

CONCLUSIONS

XP and TN rotatory files with small taper and volume maintained better with minor changes at the PCD and SDTZ, while WG reciprocation file produced the largest change. All the files were maintained centered at the PCD, and their performances were safe with a minimal thickness higher 0.5 mm at the SDTZ, and without risk of perforation.

TRIAL REGISTRATION

No clinical trials were indicated in this study.

CLINICAL RELEVANCE

The choice of endodontic files is a relevant factor in the conservative performance of root canal treatments.

Exploring the Efficacy of 6 Preparation Systems for Achieving Minimal Root Canal Transportation: A Micro-CT Investigation

INTRODUCTION

This study aimed to assess the canal transportation with 6 preparation systems.

METHODS

Sixty curved mesial roots of mandibular molars were scanned, and their root canals (n = 20 per group) were prepared with XP-endo Shaper, BioRace, ProTaper Next, Twisted File Adaptive, Reciproc, or Reciproc Blue systems. After preparation, a new scan was conducted, and transportation was determined by comparing the geometric center of the canal in 13,542 cross-sectional slices. The transport direction frequencies were recorded, and linear transport were compared using a Univariate GLM model and Tukey honestly significant difference tests (α = 5 %).

RESULTS

Transportation was affected by the preparation system and root third (P < .05), with no significant effect observed for the root canal (P > .05). The Twisted File Adaptive had the highest transport (P < .05), and the lowest transports were observed with XP-endo Shaper, ProTaper Next, and BioRace (P < .05). Reciproc Blue and Reciproc showed intermediate results (P < .05). The apical and coronal third exhibited the lowest and highest transportation, respectively (P < .05). A significant interaction was observed between the preparation system and root third (P < .05). In the coronal third, transportation was mostly toward the disto-inside direction, whereas in the middle and apical thirds, transportation was predominantly toward the mesio-outside direction.

CONCLUSIONS

XP-endo Shaper had the lowest mean linear transportation followed by the ProTaper Next, BioRace, Reciproc Blue, and Reciproc systems. The Twisted File Adaptive system had the worst performance. The direction of transportation was generally toward the inner aspect of the canal at the coronal third and toward the outer aspect of the curve at the middle and apical thirds.

Shaping ability of BlueShaper, TruNatomy, DC Taper and HyFlex EDM in long oval canals: An ex vivo study

AIM

This study evaluated and compared the shaping ability of four rotary instrument systems in long-oval root canals using microcomputed tomographic (micro-CT) evaluation. Currently, there is no data available on the canal shaping abilities of BlueShaper and DC Taper instruments.

METHODOLOGY

Sixty-four single-rooted mandibular premolars were matched based on similar root canal morphologic features as determined by (micro-CT) and randomly assigned to 1 of 4 experimental groups (n = 16) according to the instrument system used: BlueShaper, TruNatomy, DC Taper and HyFlex EDM One File. Changes in the root canal surface and volume, remaining dentine thickness, and number of prepared areas were assessed.

RESULTS

No significant differences were found amongst the four instrument systems for the parameters evaluated (p > .05). There was a significant reduction in the number of unprepared areas and the remaining dentine thickness after each increase in size of the instruments tested (p < .05).

CONCLUSIONS

The four instrument systems perform similarly in long oval root canals. Although none could prepare all canal walls, larger preparations incorporated significantly more surfaces in the final shape.

Disinfection and Shaping of Vertucci Class II Root Canals after Preparation with Two Instrument Systems and Supplementary Ultrasonic Activation of Sodium Hypochlorite

INTRODUCTION

This study compared disinfection and shaping after root canal preparation with either XP-endo Shaper or TruNatomy instrument systems, supplemented by ultrasonic activation of sodium hypochlorite (NaOCl) with either stainless-steel (SS) or nickel-titanium (NiTi) inserts.

METHODS

Mesial roots from mandibular molars with Vertucci class II configuration were divided into 2 groups (n = 24) based on anatomically paired micro-computed tomography (micro-CT) analyses. Pre and postpreparation micro-CT scans were obtained to evaluate the shaping performance. The canals were contaminated with a mixed bacterial culture for 30 days and then subjected to preparation with either XP-endo Shaper or TruNatomy instruments using NaOCl irrigation. Supplementary ultrasonic activation of NaOCl was conducted using either an SS (TruNatomy group) or NiTi (XP-endo Shaper group) insert. Bacteriological samples were taken from the canals before preparation (S1), after preparation (S2), and after the supplementary approach (S3). Bacterial reduction was evaluated using a quantitative real-time polymerase chain reaction.

RESULTS

Preparation with both instrument systems significantly reduced bacterial counts (P < .01). After preparation, 36% (TruNatomy) and 35% (XP-endo Shaper) were negative for bacteria. These values increased to 59% and 65% after ultrasonic activation with the SS and NiTi inserts, respectively. The quantitative data in S2 showed that XP-endo Shaper promoted a significantly higher bacterial reduction than TruNatomy (P < .05). No significant intragroup differences were observed after ultrasonic activation (P > .05), probably because the SS insert promoted a significantly higher S2-to-S3 reduction than the NiTi insert (P < .01). Micro-CT analysis revealed no significant differences in the unprepared areas between the groups (P > .05).

CONCLUSIONS

The XP-endo Shaper caused a significantly higher bacterial reduction than TruNatomy in Vertucci class II canals. Better antibacterial results after ultrasonic activation were observed for the SS ultrasonic inserts than for the NiTi inserts.

Shaping ability of different NiTi rotary systems during the preparation of printed mandibular molars

This study aimed to evaluate the shaping ability of XP-endo Shaper, TruNatomy and EdgeFile X3 during the preparation of resin-printed mandibular molar mesial root canals. Thirty-three resin-based mandibular mesial roots with two canals, obtained from extracted tooth cone-beam computed tomography (CBCT) image and printed on a three-dimensional (3D) printer, were divided into three experimental groups according to the different nickel-titanium (NiTi) systems used for root canal preparation. The specimens were scanned using CBCT imaging before and after root canal preparation. Then images were registered using a dedicated software and changes in the canal area, volume, untouched canal surface and the maximum and minimum dentine wall wear were calculated. The XP-endo Shaper instruments showed improved shaping ability with lower untouched root canal surface and better preservation of root canal anatomy during the preparation of resin-printed mandibular mesial root canals compared with TruNatomy and EdgeFile X3 systems.

Comparative Evaluation of Debris Extrusion, Remaining Dentin Thickness and Fracture Resistance of Endodontically Treated Teeth Using Rotary and Reciprocating Endodontic File Systems: An In Vitro Study

BACKGROUND

Preventing the apical extrusion of debris during instrumentation is of paramount importance to reduce the occurrence of flare-ups in endodontically treated teeth. Furthermore, an essential requirement for the longevity and strength of an endodontically treated tooth and its ability to resist fracture is the preservation of residual dentin thickness during instrumentation. The aim of this study was to compare the amount of debris extrusion, remaining dentin thickness at the coronal third, middle third, apical third, and the fracture resistance of the teeth using rotary (TruNatomy; Dentsply Sirona, Charlotte, NC) and reciprocating (WaveOne Gold; Dentsply Sirona) endodontic file systems.

METHODS

An in vitro study included 52 single-rooted, oval canal shaped teeth that underwent exploration and initial cleaning with a no. 15 K-file. The prepared canals were then randomly assigned to two groups: Group I, with instrumentation with the TruNatomy rotary file (n=26) and Group II, with instrumentation with the WaveOne Gold reciprocating file. Parameters like debris extrusion, remaining dentin thickness, and fracture resistance were evaluated in both the groups. Analysis was performed using a paired t-test for the assessment of difference between groups and one-way ANOVA test followed by the post-hoc Tukey test for difference between the coronal, middle and apical third for each study group.

RESULTS

The results revealed no significant difference (t=0.454, p=0.652) between the TruNatomy rotary file and WaveOne Gold reciprocating file in apical extrusion of debris after their use in root canal therapy. For the remaining dentin thickness, a significant difference was present between the TruNatomy rotary file and WaveOne Gold reciprocating rotary file at the coronal (t=5.766, p<0.0001) and middle (t=3.690, p=0.001) levels. The mean fracture resistance was significantly more (t=15.877, p<0.0001) with the TruNatomy rotary file compared to the WaveOne Gold reciprocating rotary file.

CONCLUSION

The TruNatomy rotary file system outperformed the WaveOne Gold reciprocating file system in terms of maintaining the remaining dentin thickness and providing improved fracture resistance. Nevertheless, debris extruded apically was comparable between the TruNatomy rotary file system and the WaveOne Gold reciprocating file system.

Pulp-Dentin Complex Regeneration with Cell Transplantation Technique Using Stem Cells Derived from Human Deciduous Teeth: Histological and Immunohistochemical Study in Immunosuppressed Rats

The aim of this study was to histologically verify the performance of pulp-derived stem cells used in the pulp-dentin complex regeneration. Maxillary molars of 12 immunosuppressed rats were divided into two groups: the SC (stem cells) group, and the PBS (just standard phosphate-buffered saline) group. After pulpectomy and canal preparation, the teeth received the designated materials, and the cavities were sealed. After 12 weeks, the animals were euthanized, and the specimens underwent histological processing and qualitative evaluation of intracanal connective tissue, odontoblast-like cells, intracanal mineralized tissue, and periapical inflammatory infiltrate. Immunohistochemical evaluation was performed to detect dentin matrix protein 1 (DMP1). In the PBS group, an amorphous substance and remnants of mineralized tissue were observed throughout the canal, and abundant inflammatory cells were observed in the periapical region. In the SC group, an amorphous substance and remnants of mineralized tissue were observed throughout the canal; odontoblasts-like cells immunopositive for DMP1 and mineral plug were observed in the apical region of the canal; and a mild inflammatory infiltrate, intense vascularization, and neoformation of organized connective tissue were observed in the periapical region. In conclusion, the transplantation of human pulp stem cells promoted partial pulp tissue neoformation in adult rat molars.

Analysis of Shaping Abilities of Rotary File Systems in Oval Canals with Moderate Root Curvature: A Randomized Controlled Ex Vivo Study

AIM

The purpose of this study was to evaluate and compare the canal transportation tendencies and centering ability of the TruNatomy shaper (TN) and XP-endo shaper (XPS) rotary systems in oval-shaped canals with moderate root curvature (15°-25°), using cone-beam computed tomography (CBCT) imaging.

MATERIALS AND METHODS

Sixty single-rooted permanent human teeth were chosen after considering the inclusion and exclusion criteria. The teeth were divided into two groups (n = 30). The test group was instrumented with TN files and the other with XPS according to manufacturer's instructions. CBCT images were taken before and after instrumentation to record the root canal distances from mesial, distal, buccal, and lingual borders of the root at 3, 5, and 7 mm distances from the root apex using a specific formula. Statistical analysis was done using the Statistical Package for the Social Sciences software program, version 20.0. The data were analyzed using the unpaired t test.

RESULTS

Both TN and XPS were safe for use in oval-shaped canals with moderate root curvature. However, the XPS showed higher buccolingual transportation as compared with TN at 3 mm from the apex and higher mesiodistal transportation at 3 and 5 mm levels from the apex as compared with TN.

CONCLUSION

Canal transportation has been detected in both systems; however, the values obtained were within the safe range (<0.3 mm). Overall, no significant difference was observed between TN and XPS (p > 0.05) in their canal transportation tendencies and centering ability.

CLINICAL SIGNIFICANCE

The study assesses the canal centering and transportation tendencies of the recently launched TN rotary system in extracted teeth with a combination of morphologies. The findings of the study are significant clinically as minimum transportation of the canal, minimal dentin removal, efficient disinfection, and three-dimensional obturation of the root canal are considered important factors in deciding the prognosis of endodontic therapy.

Optimization of automated preparation of long oval-shaped root canals using supplementary instrumentation

This study compared the preparation of long oval-shaped root canals using WaveOne Gold and XP-endo Shaper systems, both supplemented or not with manual instrumentation. Twenty-four long oval-shaped canals of mandibular incisors were distributed into two groups according to the instrumentation: WaveOne Gold Primary or XP-endo Shaper systems. All root canals were manually instrumented with a size 25 K-file after automated preparation. The specimens were scanned by using a micro-CT device (17.42 µm) before and after automated preparation and manual instrumentation. The increased surface of the root canal and the percentage of untouched areas were assessed. Both WaveOne Gold and XP-endo Shaper systems increased the root canal surface and had similar untouched areas (p>0.05). Supplementary instrumentation increased the surface of the root canal and decreased the untouched walls (p<0.05). WaveOne Gold and XP-endo Shaper systems provided a similar preparation of long oval-shaped canals and manual instrumentation improved their preparation.

Design, metallurgy, mechanical properties, and shaping ability of 3 heat-treated reciprocating systems: a multimethod investigation

OBJECTIVE

This study aimed to compare 3 reciprocating systems regarding design, metallurgy, mechanical properties, and shaping ability.

MATERIALS AND METHODS

New Reciproc Blue R25, WaveOne Gold Primary, and REX 25 instruments (n=41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin, and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. Results were compared using one-way ANOVA post hoc Tukey and Kruskal-Wallis tests with a significant level set at 5%.

RESULTS

All instruments showed symmetrical cross sections with asymmetrical blades, no radial lands, no major defects, and an almost equiatomic nickel and titanium ratio. The highest R-phase start temperatures were observed with WaveOne Gold (46.1°C) and REX (44.8°C), while Reciproc Blue had the lowest R-phase start (34.5°C) and finish (20°C) temperatures. WaveOne Gold had the lowest time to fracture (169 s) and the highest maximum load (301.6 gf) (P <0.05). The maximum torque of Reciproc Blue (2.2 N.cm) and WaveOne Gold (2.1 N.cm) were similar (P >0.05), but lower than REX (2.6 N.cm) (P <0.05). No statistical differences were observed among instruments in the angle of rotation (P >0.05) and in the shaping ability in both mesial and distal canals (P >0.05).

CONCLUSION

Although the overall design, temperature transition phases and mechanical behavior parameters were different among tested instruments, they were similar in terms of shaping ability.

CLINICAL RELEVANCE

All tested heat-treated NiTi reciprocating systems showed similar shaping ability, without clinically significant errors.

Evaluation of design, mechanical properties, and torque/force generation of heat-treated NiTi glide path instruments

BACKGROUND

Recently, various kinds of heat-treated nickel-titanium (NiTi) glide path instruments have been manufactured. This study aimed to investigate design, phase transformation behavior, mechanical properties of TruNatomy Glider (#17/02), V Taper 2H (#14/03), and HyFlex EDM (#15/03) and compare torque/force generated during simulated glide path preparation with them.

METHODS

The designs and phase-transformation behaviors of the instruments were examined via scanning electron microscopy (n = 3) and differential scanning calorimetry (n = 2). Their bending (n = 15), torsional (n = 15), and cyclic fatigue resistances (n = 15) were tested. The ultimate strength and distortion angle were obtained from torsional resistance test. The number of cycles to failure (NCF) was calculated from cyclic fatigue resistance test. The preparation of the glide path was simulated using a double-curved artificial canal (n = 15), and the maximum torque and screw-in forces were measured. Data except NCF was compared between brands with one-way ANOVA with Tukey's honestly significant difference test. NCF was analyzed via Kruskal-Wallis and Mann-Whitney U tests.

RESULTS

TruNatomy Glider had the greatest number of threads. TruNatomy Glider showed progressive taper, while V Taper 2H and HyFlex EDM had constant taper. The austenitic transformation-finish temperatures of all the instruments were above body temperature. V Taper 2H demonstrated significantly lower ultimate strength, higher distortion angle, and a higher number of cycles to failure compared with HyFlex EDM and TruNatomy Glider (p < 0.05). The maximum torque generated during preparing glide path was lowest for V Taper 2H, and the maximum screw-in force was lowest for HyFlex EDM (p < 0.05). TruNatomy Glider generated the highest torque and screw-in force during the apical preparation.

CONCLUSIONS

V Taper 2H #14/03 showed superior cyclic fatigue resistance and lower ultimate strength. TruNatomy Glider generated greater clockwise torque and screw-in force during apical preparation. The mechanical properties, torque, and screw-force was affected by design of heat-treated glide path instruments. Cervical pre-flaring prior to glide path instrument is recommended.

Micro-Computed Tomography Evaluation of Minimally Invasive Shaping Systems in Mandibular First Molars

The aim of this study was to compare the shaping ability of a modified ProTaper Next technique (PTNm) with that of TruNatomy (TN) in lower molars mesial curved canals using micro-computed tomography (Micro-CT). Sixty mesial canals of first mandibular molars were randomly assigned between two groups (n = 30). After canal scouting with K-File #10, glide path and shaping were carried out with TN or PTNm systems. The PTNm sequence consists of ProGlider, followed by ProTaper Next X1 and apical finishing with NiTiFlex #25 up to working length (WL) to ensure adequate apical cleaning. Samples were scanned using micro-CT and pre- and post-shaping volumes were matched to analyse geometric parameters: the volume of removed dentin; the difference of canal surface; centroid shift, minimum and maximum root canal diameters; cross-sectional areas; the ratio of diameter ratios (RDR) and the ratio of cross-sectional areas (RA). Measurements were assessed 2 mm from the apex and in relation to the middle and coronal root canal thirds. Data were analysed using ANOVA (p < 0.05). No statistically significant differences were found between the groups for any parameter at each level of analysis, except for RA at the coronal level (p = 0.037). The PTNm system showed the tendency to enlarge more in the coronal portion with a lower centroid shift at apical level compared with TN sequence (p > 0.05). Both PTNm and TN sequences demonstrated similar maintenance of original anatomy during the shaping of lower molar mesial curved canals.

A Multimethod Assessment of a New Customized Heat-Treated Nickel-Titanium Rotary File System

This study aimed to compare three endodontic rotary systems. The new Genius Proflex (25/0.04), Vortex Blue (25/0.04), and TruNatomy (26/0.04v) instruments (n = 41 per group) were analyzed regarding design, metallurgy, and mechanical performance, while shaping ability (untouched canal walls, volume of removed dentin and hard tissue debris) was tested in 36 anatomically matched root canals of mandibular molars. The results were compared using one-way ANOVA, post hoc Tukey, and Kruskal−Wallis tests, with a significance level set at 5%. All instruments showed symmetrical cross-sections, with asymmetrical blades, no radial lands, no major defects, and almost equiatomic nickel−titanium ratios. Differences were noted in the number of blades, helical angles, cross-sectional design, and tip geometry. The Genius Proflex and the TruNatomy instruments had the highest and lowest R-phase start and finish temperatures, as well as the highest and lowest time and cycles to fracture (p < 0.05), respectively. The TruNatomy had the highest flexibility (p < 0.05), while no differences were observed between the Genius Proflex and the Vortex Blue (p > 0.05). No differences among tested systems were observed regarding the maximum torque, angle of rotation prior to fracture, and shaping ability (p > 0.05). The instruments showed similarities and differences in their design, metallurgy, and mechanical properties. However, their shaping ability was similar, without any clinically significant errors. Understanding these characteristics may help clinicians to make decisions regarding which instrument to choose for a particular clinical situation.

Torsional Fracture Resistance of Niti Rotary Glide Path Files under Flexural Stress

This study aimed to evaluate the effects of flexural stress on the torsional fracture resistance of NiTi glide path files. PathFile #16/02, RaCe #15/04, RaCe Evo #15/04, HyFlex EDM #15/03, TruNatomy Glider #17/02, and V Taper 2H #17/04 were examined by scanning electron microscopy (SEM) (n = 3/brand) and subjected to differential scanning calorimetry (n = 2/brand). Torsional fracture resistance testing was performed in straight (ISO 3630-1) and flexural modes (n = 15/brand/mode). Flexural mode testing involved instruments rotating within a stainless-steel artificial double-curved canal. Ultimate strength and distortion angle until failure were recorded, and fractured instruments were examined by SEM. Statistical analyses involved independent sample t-test and one-way analysis of variance with Games–Howell pots hoc test. Austenitic transformation- finishing temperatures of heat-treated files were above body temperature. For RaCe Evo, HyFlex EDM, TruNatomy Glider, and V Taper 2H, the flexural mode resulted in a significantly higher distortion angle compared to the straight mode (p < 0.05). The maximum torque of RaCe Evo, HyFlex EDM increased with the flexural stress (p < 0.05). V taper 2H showed the highest distortion angle and ultimate strength. SEM showed typical patterns of torsional fracture for all tested files. The flexural stress positively affected distortion angle of heat-treated NiTi glide path files.

Shaping ability of rotary and reciprocating single-file systems in combination with and without different glide path techniques in simulated curved canals

Background/purpose

Materials and methods

Results

Conclusion

A micro-CT analysis of radicular dentine thickness in mandibular first premolars presenting C-shaped root canals: Identification of potential danger zones

AIM

To describe the radicular dentine thickness in mandibular first premolars presenting C-shaped root canals, in order to identify the canal walls with less thickness as potential danger zones. In addition, to describe the internal and external anatomical characteristics of these teeth and to associate them to the dentine thickness.

METHODOLOGY

A total of 70 mandibular first premolars presenting C-shaped root canals were examined. Their internal morphology was analyzed using Vertucci´s and Fan´s criteria, and their external morphology was analyzed using the ASUDAS score. Besides, the dentine thickness around the root canals was two/three-dimensionally determined at five root planes and quantified in the distal and the mesial aspects.

RESULTS

According to Fan´s, ASUDAS, and Vertucci´s classifications, the most common canal configurations were category C3, grade 3, and type V, respectively. In Vertucci's type III anatomy, the mesial root wall of the lingual canal showed significantly less dentine thickness than the distal wall in the middle plane (p = 0.031). Similarly, in Vertucci's type V anatomy, significantly less dentine thickness was observed in the mesial root wall of the buccal and lingual canals in the middle plane (p < 0.001) and the buccal canal in the middle-apical plane (p = 0.014) than the distal root wall of these canals. In teeth with ASUDAS grade 3 and 4 scores, significantly less dentine thickness was observed in the mesial in comparison with the distal root wall of these canals. These differences were demonstrated in the middle and middle-apical planes (p < 0.001) of grade 3 teeth and the middle-apical plane (p < 0.001) of grade 4 teeth. In these root planes, the Ver1-AS3 and VerV-AS3 combinations presented a 4-times greater risk of presenting walls with a critical dentine thickness of 0.6 mm (OR=4, p = 0.025) than the combinations Ver1-AS2, VerV-AS2, VerV-AS4, and VerIII-AS3.

CONCLUSIONS

The root canal system configuration of mandibular first premolars with C-shaped canals showed a wide range of anatomical variations. The lowest dentine thickness was located in the mesial wall of the canals in the middle and apical root thirds of Vertucci´s type III and V anatomies and in teeth with deep radicular grooves scored as ASUDAS grade 3 and 4. In the middle and middle-apical planes, the presence of the combinations Ver1-AS3 and VerV-AS3 showed a high risk of presenting a critical dentine thickness of 0.6 mm. Therefore, these root canal walls with less dentine thickness represent potential instrumentation danger zones in mandibular first premolars with C-shaped canals.

The impact of TruNatomy and ProTaper Gold instruments on the preservation of the periradicular dentin and on the enlargement of the apical canal of mandibular molars

INTRODUCTION

This study aimed to evaluate the preservation of the periradicular dentin and the enlargement of the apical canal of mandibular molars with TruNatomy and ProTaper Gold instruments.

METHODS

Twenty mandibular molars were scanned in a micro-CT device, anatomically paired, and distributed into 2 groups (n=10). In the ProTaper Gold group, mesial and distal canals were prepared up to F2 (25/.08v) and F3 (30/.09v) instruments, while in the TruNatomy group, mesial and distal canals were enlarged until Prime (26/.04v) and Medium (36/.03v) instruments, respectively. After a new scan, surface area, volume, unprepared areas, transportation, percentage of dentin removal, and dentin thickness parameters were calculated. Data were compared between groups using Mann-Whitney, Student t-test, and the non-metric multidimensional scaling test with alpha set at 5%.

RESULTS

No difference was found between groups regarding unprepared canal areas and reduction of dentin thickness (P > 0.05). Transportation was lower than 0.1 mm in all groups and statistical differences were observed only at the apical third of the mesiobuccal canal with lower values in the TruNatomy group. ProTaper Gold removed more dentin than TruNatomy at the coronal level of mesial roots (1.8% and 1.0%, respectively) (P < 0.05).

CONCLUSIONS

TruNatomy and ProTaper Gold were efficient for performing canal preparation in mandibular molars. The tested systems were similar in terms of untouched canal walls and remaining dentin thickness, and slightly different in the apical transportation of mesial canals and percentage of dentin removal at the coronal third, but without clinically significant errors.

Impact of several NiTi-thermally treated instrumentation systems on biomechanical preparation of curved root canals in extracted mandibular molars

AIM

To evaluate the shaping ability of several heat-treated nickel-titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro-computed tomography, considering their variation in kinematics and design.

METHODOLOGY

Curved-mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n = 10), established by determining homogeneous 3D parameters of volume and surface area: R-Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP-endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10 ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross-sectional measures of area, perimeter, roundness, major/minor diameters and 3-dimensional (volume, surface area, structure model index - SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro-CT. Data were analysed using analysis of variance and post hoc Tukey tests (α = 5%).

RESULTS

Reciproc Blue and XPS had significantly greater mean increases in cross-sectional area measurements, only in the middle third, when compared with RM and HFX (p < .05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p > .05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p < .05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p < .05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p < .05). The smallest dentine thickness was observed after the use of RCB (p < .05), in the danger and safety zones.

CONCLUSIONS

XP-endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved-mesial canals of extracted molar teeth treated on a laboratory benchtop.

Shaping ability of ProTaper Gold and WaveOne Gold nickel-titanium rotary instruments in simulated S-shaped root canals

Background/purpose

Gold metal technology improves flexibility and the resistance to cyclic fatigue of the endodontic mechanical files. This study compared the performance of ProTaper Gold (PTG) multiple file system and WaveOne Gold (WOG) single file system in simulated S-shaped root canals, which represents one of the most challenging root canal morphology.

Materials and methods

Forty S-shaped canals (n = 20 canals/per group) in resin blocks were instrumented to an apical size of 0.25 mm using PTG and WOG Primary, respectively. The total amount of resin removal, canal transportation, centering ratio, and the degree of canal straightening were measured in Photoshop CS6 software. Statistical analysis was performed by using Mann–Whitney U-test (α = .05).

Results

None of the files fractured during the instrumentation. The WOG group removed significantly less amount of resin at 0, 3, 6, 7 and 9 mm from the apex (P < .05). The WOG group remained more centered in canals at 0 mm from the apex (P < .05). The PTG group showed a better centering ability and less canal transportation at 4, 5 and 6 mm from the apex (P < .05). In the coronal curvature portion, the use of WOG Primary significantly decreased curvature angle and increased radius compared with PTG instruments (P < .05). There was no significant difference between the two groups in terms of the apical curvature angle and radius change (P > .05).

Conclusion

The WOG Primary file has a less aggressive dentin cutting and more centered apical preparation. The PTG system is more advantageous in shaping the coronal curvature of S-shaped canal.

Shaping ability of modern Nickel-Titanium rotary systems on the preparation of printed mandibular molars

Introduction

This study aimed to evaluate the shaping ability of TruNatomy (Dentsply Maillefer, Ballaigues, Switzerland), VDW.ROTATE (VDW GmbH, Munich, Germany) and ProTaper Gold (Dentsply Maillefer, Ballaigues, Switzerland) during the preparation of resin-printed mandibular molar mesial root canals.

Materials and Methods

Thirty-three printed resin-based mandibular mesial roots with two canals were obtained from extract tooth cone-beam computed tomography (CBCT) image. The printed teeth were divided into three groups (n = 11) according to the system used for root canal preparation: TruNatomy, VDW.ROTATE, and ProTaper Gold. The specimens were scanned using CBCT imaging before and after root canal preparation. Then images were registered using a dedicated software and changes in the canal area, volume, untouched canal surface, and the maximum and minimum dentin wall wear were calculated.

Statistical Analysis Used

Data were statistically analyzed using Shapiro-Wilk for normality, one-way ANOVA, and Tukey or Kruskal-Wallis H tests with alpha set at 5%.

Results

No differences were observed for changes in the canal area, volume, untouched canal surface area, and minimum dentine wall wear parameters for the whole canal length (P > 0.05). The mean of untouched canal surface area for the TruNatomy, VDW.ROTATE, and ProTaper Gold was 40%, 44%, and 44%, respectively. The maximum dentine wall wear was significantly lower in the ProTaper Gold group than in the TruNatomy and VDW.ROTATE groups (P < 0.05).

Conclusions

TruNatomy, VDW.ROTATE, and ProTaper Gold systems showed similar shaping ability in printed resin-based mandibular mesial roots without clinically significant errors. A large amount of untouched canal surface area was observed for all systems.

Efficacy of reciprocating instruments and final irrigant activation protocols on retreatment of mesiobuccal roots of maxillary molars: a micro-CT analysis

Objectives

This study evaluated the efficacy of 3 reciprocating systems and the effects of 2 instruments for irrigant activation on filling material removal.

Materials and Methods

Forty mesiobuccal roots of maxillary molars were prepared up to size 25.06 and obturated. Micro-computed tomography (micro-CT) examination #1 was performed. Teeth were then divided into 4 groups (n = 10), according to the retreatment protocol: (1) manual, (2) Reciproc Blue, (3) WaveOne Gold, and (4) X1 Blue. Micro-CT examinations #2 and #3 were performed after filling removal and repreparation, respectively. Next, all teeth were divided into 2 new groups (n = 20) according to the irrigant activation protocol: XP Clean (XP Clean size 25.02) and Flatsonic (Flatsonic ultrasonic tip). Micro-CT examination #4 was performed after irrigant activation. Statistical analysis was performed with a significance level set at 5%.

Results

WaveOne Gold removed a significantly greater amount of filling material than the manual group (p < 0.05). The time to reach the WL was similar for all reciprocating systems (p > 0.05). X1 Blue was faster than the manual group (p < 0.05). Only manual group improved the filling material removal after the repreparation stage (p < 0.05). Both activation protocols significantly improved the filling material removal (p < 0.05), without differences between them (p > 0.05).

Conclusions

None of the tested instruments completely removed the filling material. X1 Blue size 25.06 reached the working length in the shortest time. XP Clean and Flatsonic improved the filling material removal.

The shaping ability of WaveOne Gold, TRUShape and XP-endo Shaper systems in oval-shaped distal canals of mandibular molars: A microcomputed tomographic analysis

AIM

To compare the shaping ability of a heat-treated centric reciprocating file system (WaveOne Gold), a heat-treated eccentric rotary multifile system (TRUShape 3D Conforming Files), and a heat-treated expandable one-file rotary system (XP-endo Shaper) extending its activation time, in preparing oval-shaped root canals in extracted mandibular molars by means of microcomputed tomography (micro-CT) analysis.

METHODOLOGY

Thirty moderately curved oval-shaped distal roots of mandibular molars were selected. The normality of canal length, curvature angle, volume, surface area, structure model index, and aspect ratio were confirmed. The samples were randomly divided into three groups (n = 10). Micro-CT scans were taken before and after canals were instrumented using WaveOne Gold (size 35, .06 taper), or TRUShape (size 30, .06v taper), both following the manufacturer's instructions, or XP-endo Shaper following a new protocol with extended activation time. The mechanical preparation time for each sample was recorded. Pre- and postoperative images were analysed for the percentage of unprepared canal areas and the percentage of removed dentine. Data were compared between groups using the statistical analyses one-way ANOVA and Tukey tests (p < .05).

RESULTS

The percentage of unprepared canal areas was significantly higher with WaveOne Gold (% 11.5 ± 4.0) and TRUShape (% 12.4 ± 5.8) compared with XP-endo Shaper (% 5.2 ± 2.6) (p < .05). XP-endo Shaper removed significantly more dentine (3.3 ± 1.5 mm³ ) than WaveOne Gold (1.8 ± 0.8 mm³ ) and TRUShape (1.9 ± 0.8 mm³ ) (p < .05). No significant differences were seen for mechanical preparation time between WaveOne Gold (79 ± 31 s), TRUShape (104 ± 41 s) and XP-endo Shaper (71 ± 23 s) (p > .05).

CONCLUSIONS

The comparison of three recognized root canal filing systems has shown that with similar preparation times, the XP-endo Shaper removed more dentine (mm³ ) leaving less unprepared canal wall area (%) than WaveOne Gold and TRUShape when preparing oval-shaped root canals of extracted mandibular molars.

Volume Percentage of Filling Voids in Root Canals Prepared by a Novel Nickel-Titanium Rotary System (TruNatomy) Using Two Different Obturation Techniques

This study aimed to compare the volume percentage of filling voids in root canals prepared with a newly introduced rotary system, TruNatomy (Dentsply Maillefer), and obturated by the modified continuous wave (CW) or single cone (SC) filling technique. Plastic tooth models with four canals were enlarged by using TruNatomy files and randomly allocated into either the CW or SC group. The volume percentage of filling voids at 1–6 mm from the apex was analyzed by using microcomputed tomography; mean values were compared by using independent two-sample t-tests (p < 0.05). The mean volume percentages of the filling voids were 2.81 ± 1.11% and 1.77 ± 0.82% in the CW and SC groups, respectively. In the apical area (1–4 mm), volume percentages in the palatal were significantly different between the CW and SC groups; in the middle area (4–6 mm), volume percentages in the palatal and the second mesiobuccal canals were significantly different (p < 0.05). The SC group showed lower volume percentages of filling voids than the CW group. The canals prepared by the TruNatomy system can be obturated well by both the SC and CW techniques. The SC technique showed a lower number of voids, especially in the palatal canals.