Vertical Load Induced with Twisted File Adaptive System during Canal Shaping

Assessment of Vertical Force Generated with Single File Systems during Shaping of Constricted Root Canals

OBJECTIVES

 This study aimed to evaluate the shaping force generated with OneShape (OS) and HyFlex EDM (HEDM) systems designed for single file shaping, in comparison with ProTaper Next (PTN).

MATERIALS AND METHODS

 Maxillary premolar teeth received access cavity preparation and their canals were shaped with OS, HEDM, or PTN to size 25 according to manufacturer's instructions with consistent pressure on the files to give a gentle "in-and-out" movements of 2 mm amplitude. The canal shaping was completed with a total of three insertions. After each insertion, 1% NaOCl irrigation and recapitulation with K-file size 15 were performed. The vertical shaping force was measured using a force gauge (M5-20 Advanced Digital Force Gauge; Mark-10 Corporation, NY).

STATISTICAL ANALYSIS

 The shaping time was analyzed by using a one-way analysis of variance (ANOVA) test and differences between the mean apical and coronal maximum force values were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. The level of significance was set as 0.05.

RESULTS

 The magnitude of the vertical forces increased with successive advancements of the instruments within the canal. During canal shaping procedures in all groups, the apical and coronal maximum force values of the OS and HEDM ranged from 2.5 to 7.2 N and 1.3 to 2.9 N, respectively. PTN generated the lowest maximum apical forces during the second and third insertions (p < 0.05). HEDM generated significantly less maximum coronal forces than both OS and PTN during the first insertion while the use of OS was associated with the highest amount of force values in the second and third insertions (p < 0.05). In terms of shaping time, no significant differences were detected among the three tested systems (p = 0.606).

CONCLUSION

 The tested single file systems were associated with higher shaping forces in the apical direction that were significant in the second and third insertions.

Impact of Sequential Use of Reciprocating Files on the Shaping Load During Root Canal Treatment

INTRODUCTION

The purpose of this in vitro study was to investigate the apical and coronal loads generated during shaping canals with 2 successive reciprocating files in comparison to a single reciprocating file from the same system.

METHODS

A total of 40 narrow and straight canals were distributed into two groups: R-Motion with single file (RMS) and R-Motion with multiple files (RMM). In both groups, the R-Motion system was used in a reciprocating motion. After establishing glide path, the RMS canals were shaped down to working length with a single file (25/.06) in two insertions while the RMM canals were shaped with two files (20/.04 and 25/.06) to the working length. The shaping time and effects of tested groups on the apical and coronal peak loads were statistically analyzed using the t-test and Mann-Whitney U test, respectively, at a 95% confidence level.

RESULTS

All canals were completely shaped in three insertions and no file deformation or fracture was observed. The RMS and RMM were able to shape canals in 117.3 ± 15.1 and 123.7 ± 7.3 seconds, respectively (P < .05). Within each group, the shaping load appeared to increase with the successive insertions of the file. In both groups, the ranges of apical and coronal peak loads were 0.41-1.87 N and 0.38-1.03 N, respectively. The RMM and RMS had comparable apical and coronal peak loads (P > .05) except in the last insertion where RMM showed clearly lower apical peak load than RMS (P < .01).

CONCLUSIONS

Under the current laboratory conditions using the R-Motion system, preshaping the canal with a smaller reciprocating file was shown to favorably reduce the apical peak loads induced during canal shaping of extracted teeth.

Impact of cooling on shaping ability of thermally treated files in canal models with double curvature

Background

This study compared the ability of thermally treated files in shaping simulated canals with double curvature. Fifty-six canals were enlarged to a final size of 25 with ProTaper Next (PTN) or ZenFlex (ZF).

Materials

Half of the samples were shaped with cooled files (n = 14 each). The amount of removed resin was measured and canal deviation was determined at eight levels. Shaping time and maximum shaping torque values were also recorded. Data were statistically analyzed using analysis of variance and LSD, Kruskal-Wallis, and chi-square tests at a 0.05 significance level.

Results

Compared to PTN and cooled PTN, ZF and cooled ZF required lesser time to shape the canals. The maximum torques were found comparable between the groups. All the groups generated negligible deviations at every canal level evaluated and maintained the canal geometry. Although not significant, the cooled PTN and ZF files exhibited lesser canal deviations than their counterparts.

Conclusion

All groups demonstrated similar shaping ability whilst maintaining the original curvature of the canal in simulated canals with double curvature. However, ZF groups were able to shape the canals faster than PTN groups. There was a trend that cooled files made lesser canal deviations compared to their counterparts.

Effect of Different Downward Loads on Canal Centering Ability, Vertical Force, and Torque Generation during Nickel-Titanium Rotary Instrumentation

This study aimed to examine how downward loads influence the torque/force and shaping outcome of ProTaper NEXT (PTN) rotary instrumentation. PTN X1, X2, and X3 were used to prepare J-shaped resin canals employing a load-controlled automated instrumentation and torque/force measuring device. Depending on the torque values, the handpiece was programmed to move as follows: up and down; downward at a preset downward load of 1 N, 2 N or 3 N (Group 1N, 2N, and 3N, respectively; each n = 10); or upward. The torque/force values and instrumentation time were recorded, and the canal centering ratio was calculated. The results were analyzed using a two-way or one-way analysis of variance and the Tukey test (α = 0.05). At the apex level, Group 3N exhibited the least canal deviation among the three groups (p < 0.05). The downward force was Group 3N > Group 2N > Group 1N (p < 0.05). The upward force, representing the screw-in force, was Group 3N > Group 1N (p < 0.05). The total instrumentation time was Group 1N > Group 3N (p < 0.05). In conclusion, increasing the downward load during PTN rotary instrumentation improved the canal centering ability, reduced the instrumentation time, and increased the upward force.

Kinematics of 'Adaptive Motion' under constant torque values

INTRODUCTION

To demonstrate the unknown kinematics of complex adaptive motion with respect to disclosed values, the aim of the present study was (i)to analyze the adaptive motion and (ii)to compare the effects of constant torque values on kinematics.

METHODS

A new endodontic motor(Aseptico AEU-28SYB Elements) and 8:1 contra-angle handpiece were used for analysis. A pilot test was conducted for synchronizing the external experimental stress on the shaft of the target object and the inbuilt torque sensor of the motor source. A load setup was developed by attaching universal precision weights to the shaft of the of the target object. The groups were adaptive motion with no load(TFA-0), adaptive motion with 100 gcm(TFA-100), and 200 gcm(TFA-200) constant load. The peak-to-peak based phase identification method was used to analyze the kinematics. Student's t and Mann Whitney U tests were used where applicable(α=0.05).

RESULTS

A noteworthy observation was the inconsistent kinematics of the TFA-100 compared to the kinematics of TFA-0 and TFA-200. TFA-100 presented mixed-phased kinematics, which consisted of both quaternary(n=33) phases similar to that of TFA-200, and dual(n=17) phases similar to that of TFA-0. The sequence of these quaternary and dual phases of TFA-100 was arbitrarily changing. The kinematic parameters of dual-phase intermittent motion of TFA-0 and TFA-100 and quaternary-phase reciprocating motion of TFA-100 and TFA-200 revealed significant differences(p<0.05).

CONCLUSIONS

The main conclusions of the present study are the kinematics of adaptive motion was demonstrated and the 100 gcm load is not sufficient for predictable and constant operation in reciprocating mode.

The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation

(1) Background: Root canal preparation constitutes an important factor for success in endodontics. However, various complications may occur during this stage. The aim of this study was to compare the incidence of cracks within radicular dentin after instrumentation with ProTaper Next (PTN), WaveOne Gold (WOG), and Twisted Files (TF), which utilize different kinematics. (2) Methods: Eighty single-rooted teeth were classified into four groups (n = 20). Three groups were instrumented using PTN (X1, X2), WOG (Primary), and TF (SM1–3). The non-instrumented group constituted the control group. Post-preparation, the roots were sectioned 3, 6, and 9 mm from the apex using a low-speed saw (Southbay Technology Inc., San Clemente, CA, USA). The specimens were viewed through a microscope at x25 magnification (Leica M320, Wetzlar, Germany), and their surface was assessed tactilely to determine the presence of the crack. (3) Results: Partial cracks within radicular dentine were observed in all study groups (PTN: n = 4/20%, WOG: n = 3/15%, TF: n = 4/20%); no cracks were observed in the control group. No significant differences were observed among experimental groups. OR values for the incidence of cracks were: OR = 11.182 for PTN, OR = 8.2 for WOG, and OR = 8.2 for TF. (4) Conclusions: Instrumentation with PTN, WOG, and TF may result in dentinal cracks formation.

Vertical Load and Torque during Postspace Preparation and Their Influence on Microcrack Development

PURPOSE

To investigate, in vitro, the magnitudes of vertical load and torque generated during post space preparation of root canal treated teeth and their influence on microcrack development.

MATERIALS AND METHODS

Forty extracted premolars with single canals were decoronated. The roots were prepared using ProTaper Next system (Dentsply Sirona) to X3 file, obturated, and provisionalized. After a 3-week incubation period, the roots were distributed into 2 groups according to the post drill system used (ParaPost fiber post and RelyX fiber post). During post space preparation, the vertical load, torque, and preparation time were recorded. Before and after the post space preparation, the roots were imaged with micro-computed tomography (SkyScan 1172; Bruker micro-CT) to detect new microcracks. The data were analyzed using the Mann-Whitney U-test and chi-square test.

RESULTS

In ParaPost and RelyX, the post space was prepared in 48.31 ±25.28 and 47.71 ±13.36 seconds, respectively (p = 0.360). The peak vertical load generated with ParaPost (20.23 ±7.80 N) was significantly lower than that of RelyX (29.43 ±5.82 N) (p = 0.010). The maximum torque attained with ParaPost (1.42 ±0.61 N.cm) was found to be significantly lower than that of RelyX (3.23 ±1.58 N.cm) (p = 0.000). No post drill fracture or visible deformation was noticed throughout the experiment. New microcracks were found in three ParaPost samples only.

CONCLUSIONS

The choice of postdrill influenced the loads and torques generated during postspace preparation. The ParaPost system showed favorably lower load and torque values during the postspace preparation compared with the RelyX system.

Analysis of Torque and Force Induced by Rotary Nickel-Titanium Instruments during Root Canal Preparation: A Systematic Review

The aim of this review was to provide a detailed literature analysis of torque and force generation during nickel-titanium rotary root canal instrumentation. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search was performed using in PubMed and in journals for articles published in English from 1987 to June 2020 on studies that investigated dynamic torque and force in vivo or in vitro. We assessed article titles and abstracts to remove duplicates, and the titles and abstracts of the remaining articles were screened for eligibility. Full texts were read to verify eligibility by considering predetermined inclusion and exclusion criteria. Fifty-two out of 4096 studies met the inclusion criteria, from which we identified 26 factors that influence torque or force generation. Factors associated with higher torque or force generation and supported by multiple studies with mostly consistent results included convex triangle cross-sectional design, regressive taper, short pitch length, large instrument size, small canal size, single-length preparation technique, long preparation time, deep insertion depth, low rate of insertion, continuous rotation (torque), reciprocating motion (force), lower rotational speed and conventional alloy. However, several factors are interrelated, which obscured the independent effect of each factor, and there was insufficient scientific evidence supporting the influence of some factors.

Analysis of Force and Torque with XP Shaper and OneCurve Systems During Shaping of Narrow Canals

Objective:

The purpose of this laboratory-based study was to compare the shaping forces and torques developed by the XP Shaper (FKG Dentaire SA, La Chaux-de-fonds, Switzerland) and OneCurve (Micro-Mega, Besancon, France) systems during shaping of narrow canals.

Methods:

Mandibular premolars with a single canal were divided equally into two groups; XP Shaper and OneCurve (n=16 each). In both groups, the canals were shaped with XP Shaper file (30/01) or OneCurve file (25/O6) that was inserted three times until it reached the canal length. The tooth was surrounded by water under controlled simulated intracanal temperature throughout the experiment. The inward and outward peak forces and the peak torques were recorded and analyzed statistically using the Mann-Whitney test. The shaping times were analyzed using Student’s t-test. The significance level was set at 5%.

Results:

In both groups, the developed forces in both directions and the torques increased with the successive insertions of the file. In the two groups, the inward peak forces ranged from 0.33 to 3.12 N, while the outward peak forces ranged from 0.09 to 1.96 N. In the three insertions, the XP Shaper showed significantly lower peak forces in both directions. The peak torque developed in both groups ranged from 0.12 to 1.52 N.cm. XP Shaper had significantly lower torque values in all the insertions than OneCurve. The XP Shaper system was able to completely shape the canals in 33.4 seconds while the OneCurve system was able to completely shape the canals in 32.8 seconds.

Conclusion:

The XP Shaper system showed favorably lower force and torque values during canal shaping compared with the OneCurve system.

Vertical Force Induced with WaveOne and WaveOne Gold Systems during Canal Shaping

INTRODUCTION

The aim of this study was to evaluate the amount of vertical force induced with WaveOne (WO; Dentsply Sirona, York, PA) and WaveOne Gold (WOG, Dentsply Sirona) systems during the canal shaping of extracted teeth.

METHODS

Thirty canals in 15 maxillary premolars were divided into 2 groups: WO and WOG. The canals were gently shaped with WO/WOG Primary instruments according to the manufacturer's instructions. The vertical forces induced during canal shaping in the apical and coronal directions were recorded. The apically and coronally directed peak forces were used for analysis using the Mann-Whitney U test. The instrumentation time was analyzed using the Student t test. All statistical analyses were performed using SPSS software (Version 22.0; IBM, Armonk, NY) at a 5% significance level.

RESULTS

The force increased with the successive instrument insertions within each group. The apically and coronally directed peak forces of the WO and WOG groups ranged from 2.89-11.58 N and from 1.53-2.92 N, respectively. In the 3 insertions, WO showed higher peak forces in both directions. For apically directed peak forces, WO had significantly higher peak forces in the first and third insertions than WOG (P < .01). For coronally directed peak forces, WO had significantly higher values in the first and second insertions (P < .05).

CONCLUSIONS

The WOG system had significantly lower apically and coronally directed peak force values compared with the WO system.