Effect of tip design of nickel-titanium and stainless steel files on root canal preparation

Advancing Nitinol: From heat treatment to surface functionalization for nickel–titanium (NiTi) instruments in endodontics

Nickel-titanium (NiTi) alloy has been extensively researched in endodontics, particularly in cleaning and shaping the root canal system. Research advances have primarily focused on the design, shape, and geometry of the NiTi files as well as metallurgy and mechanical properties. So far, extensive investigations have been made surrounding surface and thermomechanical treatments, however, limited work has been done in the realm of surface functionalization to augment its performance in endodontics. This review summarizes the unique characteristics, current use, and latest developments in thermomechanically treated NiTi endodontic files. It discusses recent improvements in nano-engineering and the possibility of customizing the NiTi file surface for added functionalization. Whilst clinical translation of this technology has yet to be fully realized, future research direction will lie in the use of nanotechnology.

•

Nitinol (Nickel Titanium alloy) is widely used to clean/shape root canal system in endodontics.

•

To enhance its performance, various thermo-mechanical and nano-engineering modifications have been performed.

•

This comprehensive review summarizes the latest advances and future trends relating to functionalized NiTi endodontic files.

Cone-beam Computed Tomographic Analysis of Deciduous Root Canals after Instrumentation with Different Filing Systems: An In Vitro Study

Aim and objective

To evaluate root canal transportation, centering ability ratio (CAR), remaining dentine thickness, dentinal cracks, and instrumentation time after instrumentation with different filing systems in root canals of primary teeth by cone beam computed tomography (CBCT) analysis.

Materials and methods

Sixty prepared canals of primary teeth divided into 4 groups with 15 canals in each were prepared with NiTi K files, Proaper Next (PTN) files, OneShape (OS), and WaveOne (WO) files, respectively. Using CBCT scan, the pre- and postinstrumentation scan was done to obtain images at three levels (apical, middle, and cervical). The results obtained were statistically analyzed using SPSS 21 statistical software version.

Result

Significant statistical difference was found between different filing systems.

Conclusion

ProTaper Next files showed least canal transportation and the best centering ability was shown by OS file system. The NiTi K hand files preserved maximum remaining dentin thickness (RDT) and produced minimum dentin cracks. WO file system took least instrumentation time when compared to the other three filing systems.

Clinical significance

The use of rotary instruments in the pulpectomy of primary teeth represents a promising technique being advantageous for the pediatric patients by maintaining the original canal curvatures, showing greater ability to maintain dentin thickness, causing lesser dentin cracks, and reducing chair time thus favoring preparation of more conical root canals and better obturation.

How to cite this article

Singh P. Cone-beam Computed Tomographic Analysis of Deciduous Root Canals after Instrumentation with Different Filing Systems: An In Vitro Study. Int J Clin Pediatr Dent. 2022;15(S-1):S22-S29.

Comparison of five rotary systems regarding design, metallurgy, mechanical performance, and canal preparation-a multimethod research

OBJECTIVES

To compare the design, metallurgy, mechanical performance, and canal preparation of 5 rotary systems.

MATERIAL AND METHODS

A total of 735 25-mm NiTi instruments (sizes 0.17[0.18]/.02v, 0.20/.04v, 0.20/.07v, 0.25/.08v, 0.30/.09v) from ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, and U-File systems were compared regarding overall geometry and surface finishing (stereomicroscopy and scanning electron microscopy), nickel and titanium ratio (energy-dispersive spectroscopy), phase transformation temperatures (differential scanning calorimetry), mechanical performance (torsional and bending tests), and unprepared canal surface (micro-CT). One-way ANOVA and Mood's median tests were used for statistical comparisons with a significance level set at 5%.

RESULTS

Stereomicroscopic analysis showed more spirals and high helical angles in the Premium Taper Gold system. All sets of instruments had symmetrical spirals, no radial lands, no major defects, and an almost equiatomic ratio between nickel and titanium elements, while differences were observed in their tips' geometry and surface finishing. At room temperature (20 °C), DSC test revealed martensitic characteristics for ProTaper Gold and Go-Taper Flex, and mixed austenite plus R-phase for the Premium Taper Gold, while ProTaper Universal and U-Files had full austenitic characteristics. Overall, larger instruments had higher torque resistance and bending load values than smaller ones, while a lack of consistency and mixed values were observed in the angle of rotation. The 0.25/.08v and 0.30/.09v instruments of ProTaper Universal and U-File had the highest maximum torques, the lowest angles of rotation, and the highest bending loads than other tested systems (P < .05). No significant difference was noted regarding the untouched root canal walls after preparation with the tested systems (P > .05).

CONCLUSIONS

Although differences observed in the overall geometry and phase transformation temperatures have influenced the results of mechanical tests, unprepared canal surface areas were equivalent among systems.

CLINICAL RELEVANCE

Root canal preparation systems with similar geometries might present different mechanical behaviors but equivalent shaping ability.

Comparison of canal transportation and centering ability of manual K-files and reciprocating files in glide path preparation: a micro-computed tomography study of constricted canals

Background

Optimum Glide Path (OGP) is a new reciprocating motion aiming to perform efficient glide path preparation in constricted canals. The aim of this study was to investigate and compare manual and OGP movement in terms of canal transportation and centering ability in glide path preparation of constricted canals.

Methods

Thirty constricted mesial root canals of mandibular molars, with initial apical size no larger than ISO#8, were selected and negotiated with #6–#8 K-files under the microscope. Canals were randomly divided into two experimental groups: Group 1 (MAN, n = 15): Glide path was established by using #10-#15 stainless steel K-files manually; Group 2 (OGP, n = 15): #10-#15 Mechanical Glide Path super-files were used with OGP motion (OGP 90°, 300 rpm). Each instrument was used to prepare only 2 canals (as in one mesial root). Canals were scanned before and after glide path preparation with micro-computed tomography (micro-CT) to evaluate root canal transportation and centering ratio at 1, 3 and 5 mm levels from the root apex. File distortions and separations were recorded. Paired t-test was used to statistically evaluate the data (P < .05).

Results

Group 2 showed a significantly lower transportation value than group 1 at 1-mm and 3-mm levels (P < .05), however the difference at 5-mm level was not significant. There was no significant difference regarding the centering ratio between the groups. Six #10 K-files were severely distorted in group 1, while no file separation or distortion was found in group 2.

Conclusions

OGP motion performed significantly less canal transportation (apical 3 mm) and file distortion during glide path establishment in constricted canals comparing to manual motion, while the centering ability between the two was similar.

Clinical relevance

OGP reciprocating motion provides a safer and efficient clinical approach compared to traditional manual motion in glide path establishment with small files in constricted canals.

Endodontic Treatment in Artificial Deciduous Teeth through Manual and Mechanical Instrumentation: A Pilot Study

“In vitro” studies seek to simulate actual biological conditions in the laboratory providing principles to be studied later. To facilitate the development of new techniques of root instrumentation in primary teeth and to ensure the integrity and function of the element, this study aimed to demonstrate the technological advances in endodontics through endodontic treatment performed on artificial primary teeth using a rotary instrumentation system and reciprocation. Instrumentation of the root canal was performed via a manual, rotary, and Reciproc system. Results showed that current systems can facilitate endodontic treatment in one session. These procedures become increasingly easy with the help of technological advances in dentistry.

Endodontic Treatment in Artificial Deciduous Teeth by Manual and Mechanical Instrumentation: A Pilot Study

Introduction

“In vitro” studies seek to simulate actual biological conditions in the laboratory and providing principles to be studied later, to facilitate the development of new techniques of root instrumentation in primary teeth and to ensure the integrity and function of the element.

Aim

This study aimed to demonstrate the technological advances in endodontics by endodontic treatment performed on artificial primary teeth using a rotary instrumentation system and reciprocation.

Materials and methods

Instrumentation of the root canal was performed via a manual, rotatory and Reciproc system.

Results

The rotatory systems can facilitate endodontic treatment in one session.

Conclusion

These procedures become increasingly easy and rapid with the help of technological advances in dentistry.

How to cite this article

Hecksher F, Vidigal B, Coelho P, Otoni D, Alvarenga C, Nunes E. Endodontic Treatment in Artificial Deciduous Teeth by Manual and Mechanical Instrumentation: A Pilot Study. Int J Clin Pediatr Dent, 2018;11(6):510-512

Comparison of apical transportation and centering ability of Mtwo and Reciproc R25 in severely curved canals using cone-beam computed tomography

Background:

Apical transportation (AT) of the root canal moves the physiologic canal terminus to a new location on the external root surface and results in the accumulation of debris and residual microorganisms due to inadequate cleaning and shaping of the canal end. This study aimed to assess the prevalence of AT following canal preparation with Mtwo and Reciproc R25 using cone-beam computed tomographic (CBCT).

Materials and Methods:

In this in vitro study, 40 mesiobuccal root canals of the maxillary molars with 19–22 mm length and (>40°) taper were prepared in two groups using Mtwo and Reciproc R25 rotary systems along with irrigation with 2.5% NaOCl. CBCT scans were obtained of the canals before and after preparation under similar conditions, and the values were measured using the device software. The amount of AT was measured according to Gambill et al. Data were analyzed using SPSS 17 and Chi-square and t-tests. P < 0.05 was considered significant.

Results:

Both systems caused some degrees of AT. No significant difference was found between the two systems in terms of the amount and direction of AT (P > 0.05); overall, the frequency of AT toward the mesial wall was greater than that toward the distal direction. However, this difference was not statistically significant.

Conclusion:

The mean amount of AT and the ability to keep the instruments in severely curved canals were not significantly different in canals prepared by Mtwo and Reciproc rotary systems. Thus, these systems can be used in the clinical setting with the lowest risk of AT.

Comparison of canal transportation and centering ability of Twisted Files, HyFlex controlled memory, and Wave One using computed tomography scan: An in vitro study

Aim:

The aim of the present study was to compare the canal transportation and centering ability of three rotary nickel-titanium (NiTi) systems (Twisted Files [TF], HyFlex controlled memory [CM], and Wave One [WO]) in curved root canals using computed tomography (CT).

Materials and Methods:

Sixty freshly extracted single-rooted teeth having curved root canals with at least 25–35 degrees of curvature were selected. The teeth were randomly divided into three experimental groups of twenty each. After preparation with TF, HyFlex CM, and WO, all teeth were scanned using CT to determine the root canal shape. Pre- and post-instrumentation images were obtained at three levels, 3 mm apical, 9 mm middle, and 15 mm coronal above the apical foramen were compared using CT software. Amount of transportation and centering ability were assessed. The three groups were statistically compared with analysis of variance and post hoc Tukey's honestly significant difference test.

Results:

Least apical transportation and higher centering ability were seen in HyFlex CM file system in all the three sections followed by TF. WO file system showed maximum transportation.

Conclusions:

The canal preparation with HyFlex CM file system showed lesser transportation and better centering ability than TF, WO file system.

Geometric analysis of maxillary first premolar prepared by two nickel-titanium rotary instruments

AIM

The present study was conducted with the aim of evaluating and comparing the shaping ability of two Nickel-titanium rotary instruments, with two disparate design features, on root canal geometry of extracted human maxillary first premolars using microcomputed tomography.

STUDY DESIGN

Twenty four bifurcated maxillary first premolars were divided into two groups and embedded in a rubber-based impression material. Both groups were submitted to micro-computed tomography before and after canal preparation (buccal and palatal) with either ProFile Vortex or Revo-S rotary instruments. Images were reconstructed and cross-sections corresponding to a distance 1, 2, 3, 4, 5, 6, and 7 mm from the anatomical apex were selected for canal transportation analysis. Volume changes were also measured.

RESULTS

The degree and direction of canal transportation were non-significant for both instruments. Statistically significant differences were observed only between levels in the buccal canal in both groups. There was no significant difference between the two rotary systems in regards to the volume of dentin removed.

CONCLUSION

Our findings showed that ProFile Vortex and Revo-S instruments respected the original root canal anatomy and behaved similarly. ProFile Vortex rotary systems produced with innovative process were concluded to shape the upper maxillary premolar by leading minimal canal transportation, similar to Revo-S, rotary systems produced from traditional process.

Single file reciprocating technique using conventional nickel-titanium rotary endodontic files

This study was aimed to evaluate the applicability of a reciprocating movement technique with conventional nickel-titanium files for root canal preparation. Forty-four simulated canals in resin blocks were used in this study and divided as following four groups according to the instruments used and preparation methods. Group CP (n = 12) and CR (n = 12) were instrumented with continuous rotation using four files of ProFile and RaCe, respectively. Group RP (n = 10) and RR (n = 10) were instrumented with a reciprocation movement by using a single ProFile and RaCe file, respectively. The resin blocks were scanned before and after instrumentation, and the images were superimposed. To compare the efficiency of canal shaping, the preparation time, and centering ratio were calculated. Morphologic changes of tested files were examined by scanning electron microscopy (SEM). Data were analyzed by ANOVA and Duncan's post hoc test at p < 0.05. The preparation time was markedly shorter in Groups RP and RR than in Groups CP and CR. No significant difference in the centering ratio was noted between groups. Although the files used for Groups CP and CR showed no distortion under the SEM evaluation, the files used for Groups RP and RR had considerable torsional distortion. This study suggests that the reciprocating instrumentation technique using conventional nickel-titanium rotary file systems might have a comparable efficacy for the root canal shaping with reduced shaping time. Although the reciprocating technique seems to be an effective alternative to the conventional rotation technique, the risk of torsional distortion and fracture should be considered before clinical application.

The effect of single-file reciprocating systems on Substance P and Calcitonin gene-related peptide expression in human periodontal ligament

AIM

To quantify the effect of two single-file reciprocating root canal preparation systems on Substance P (SP) and Calcitonin gene-related peptide (CGRP) expression in healthy human periodontal ligament (PDL).

METHODOLOGY

Forty PDL samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. Prior to extraction, 20 of these premolars were divided equally in two groups, and then, root canals were prepared using one of two different single-file systems: WaveOne and Reciproc. Ten premolars were prepared with hand files and served as a positive control group. The remaining 10 premolars where extracted without treatment and served as a negative control group. All PDL samples were processed, and SP and CGRP were measured by radioimmunoassay.

RESULTS

Greater SP and CGRP expression were found in the hand instrumentation group (1.220 pmol SP and 0.084 pmol CGRP per mg of PDL), followed by the WaveOne group (0.908 pmol SP and 0.046 pmol CGRP per mg of PDL) and the Reciproc group (0.511 pmol SP and 0.022 pmol CGRP per mg of PDL). The lower SP and CGRP values were associated with the intact control group (0.453 pmol SP and 0.018 pmol CGRP per mg of PDL). The Kruskal-Wallis test revealed significant differences between groups (P < 0.001). Post hoc Tukey HSD tests revealed significant differences in SP and CGRP expression between intact teeth in the control group and all the other groups (P < 0.001) except with the Reciproc group (P = 0.165 and P = 0.42 for SP and CGRP, respectively). Hand instrumentation was associated with significant differences with all the other groups (P < 0.001). Differences between the WaveOne and Reciproc groups were also significant (P < 0.001).

CONCLUSION

Substance P and CGRP expression in PDL cells increased when teeth were prepared with WaveOne as well as with hand instrumentation. Reciproc maintained SP and CGRP levels in line with the negative control group.

Influence of the rotary and/or oscillatory reciprocating systems in the morphological changes of narrow and curved molar root canals anatomy

OBJECTIVE: This study evaluated four mechanized Endodontic systems, ProTaper Universal, K3 Endo, Twisted file (rotary) and the oscillatory reciprocating system Endo - Eze TiLOS, in order to verify and measure alterations in original anatomy with deviations at cervical, medium and apical root canal thirds. MATERIAL AND METHOD: It was used MB root canals of 60 extract human lower molars, to produce a line of severe angles, according to the classification of Schneider. Samples were included in Ester vinyl resin, mounted in the Teflon Furnace, transversally sectioned at the cervical, middle and apical thirds, which were subsequently photographed using a digital camera Cyber Shot DSC-TX10,attached to an operating microscope 3101XY DFVasconcelos with 40× magnification in order to measure the anatomical transversal area of the root canal, using the software AutoCAD 2008, comparing pre and post-instrumentation. All samples assembled in the Furnace also were submitted to x-ray in a standardized way to enable the comparison of the angle of Schneider pre-and post-instrumentation. Once collected the data, they were compared statistically using the program BioEstat 5.0. RESULT: The analysis of the results showed that in the cervical third, rotary systems were more effective than Endo-Eze TiLOS System with statistically significant differences (p ≤ 0,05). Apical and middle third changes in anatomy were similar, but apically, the ProTaper system caused more deviations when comparing the angle of Schneider,and areas before and after instrumentation(p ≤ 0,05). CONCLUSION: It was concluded that all the systems caused alteration in the original anatomy of the root canal when parameters as angle of Schneider and areas before and after preparation were used.

A comparison of torque required to fracture rotary files with tips bound in simulated curved canal

The purpose of this study was to compare torque force and rotation needed to fracture three types of nickel titanium alloy rotary instruments in a simulated curved root canal space that were bound at the file tip. Files of similar size tips were studied. The files studied were ProFiles with 0.04 taper diameters of 15, 20, 25, 30, 35, 40, 45; 0.04 ProFile GT sizes 20, 30, 40; and ProTaper files sizes S1, S2, F1, F2, and F3. All files were 25 mm in length. Unwinding was defined as the rotation in degrees it took for a file to fracture after the first evidence of permanent deformation. All files exhibited permanent deformation before breaking, with the ProFile GT files demonstrating the greatest unwinding. The #45 0.04 ProFile withstood the most force while the #20 ProFile GT required the least amount of force before beginning to exhibit permanent deformation. The S1 and S2 ProTaper files fractured with so little rotation that no extended data were recorded. Generally, as the file diameter increased, the force needed to begin unwinding also increased. Also, as the file diameter increased, the force needed to fracture also increased.

Current Challenges and Concepts in the Preparation of Root Canal Systems: A Review

Nickel-titanium rotary instruments are important adjuncts in endodontic therapy. This review attempts to identify factors that influence shaping outcomes with these files, such as preoperative root-canal anatomy and instrument tip design. Other, less significant factors include operator experience, rotational speed, and specific instrument sequence. Implications of various working length definitions and desired apical widths are correlated with clinical results. Despite the existence of one ever-present risk factor, dental anatomy, shaping outcomes with nickel-titanium rotary instruments are mostly predictable. Current evidence indicates that wider apical preparations are feasible. Nickel-titanium rotary instruments require a preclinical training period to minimize separation risks and should be used to case-related working lengths and apical widths. However, and despite superior in vitro results, randomized, clinical trials are required to evaluate outcomes when using nickel-titanium instruments.

A comparison of torque required to fracture three different nickel-titanium rotary instruments around curves of the same angle but of different radius when bound at the tip

Instrument fracture is an unfortunate but possible sequela of instrumentation of canals, especially when the instrument is bound at the tip. The purpose of this study was to compare the torque required to fracture three file sizes of three different rotary file types around two simulated canal curvatures, gradual or acute, when the tip of the working end of the file was bound. Profile Series 29 0.04 and 0.06 taper and Profile 0.06 ISO rotary files were placed passively into simulated canal curvatures of the same angle but of different radii. The file tips were bound 2 mm from the working end and a measurable torque was applied until fracture. ANOVA with Tamhane post-hoc comparison showed that the 0.06 Series 29 did not differ from the ISO 0.06 taper or the 0.04 Series 29 but there was statistical difference (p < 0.01) showing that the 0.04 Series 29 broke with less force than did the 0.06 ISO files. Statistical tests (p < 0.01) also showed smaller files failed with less torque, as did files in more acute canal curvatures.

Comparing apical preparations of root canals shaped by nickel-titanium rotary instruments and nickel-titanium hand instruments

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files. The specimens were divided into two groups (n = 11), after radiographing the roots from the buccolingual and mesiodistal planes with pathfinding files in situ. More strongly and less strongly curved canals were, respectively, assigned to the Lightspeed and nickel-titanium K-file groups. Using a reassembly technique, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were made of the experimental roots embedded in clear plastic. Stereomicroscopic 35-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and size 40 Master Apical Files, for the Lightspeed and K-file groups, respectively. Similar 35-mm slides of the instrumented canals were taken and electronically superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional areas of the prepared root canals were evaluated at specific levels. No significant differences in displacement of canal centers or between the mean cross-sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar displacement of canal centers after preparation.

Stress analysis of human tooth root using various root canal instruments

This study compared external root stresses from instrumentation by several motor-driven nickel-titanium instruments to stresses developed by hand files. Twelve curved first molar mesial roots were invested in PLM-9 photoelastic material to disclose net stress transmitted from the canal through the dentin. Minimal fringe patterns were observed during instrumentation with all techniques. Light-speed yielded the least change. In no case was a complete 60 psi fringe change noted.