Comparative study on the shaping ability and cleaning efficiency of rotary Mtwo instruments. Part 1. Shaping ability in simulated curved canals

Comparative Analysis of Three Nickel-Titanium Rotary Files in Severely Curved L-Shaped Root Canals: Preparation Time, Aberrations, and Fracture Rates

Background

This simulated study of 30 severely curved L-shaped root canals aimed to compare preparation time, aberrations, width measurements, and fractured files of three nickel-titanium (Ni-Ti) files, namely, ProTaper, ProTaper Next (PTN), and WaveOne (WO).

Methods

Thirty simulated L-curved root canals of resin blocks were randomly divided into three groups. The canals were prepared to a tip size of 25 using ProTaper, PTN, and WO rotary file systems. Pre- and post-operative views for each sample were captured by a professional camera at a standardized distance and position. Blue India ink was injected into the pre-operative canals, and red India ink was injected into the post-operative canals to give a clear superimposition image. Five points were assessed through the halfway of the canal to the orifice (area between the beginning of curvature and apical end point). Preparation time, aberrations, width measurements, and fractured files were recorded and analyzed.

Results

Mean preparation time was longest in ProTaper (4.89±0.68 minutes). PTN and WO were the fastest in preparing the canals (about 3 minutes). A statistically significant difference was found between WO and ProTaper & PTN and ProTaper (p=0.000), while the difference was non-significant (p > 0.05) between WO and PTN. Nine aberrations consisting of three zips, one ledge and one outer widening were related to ProTaper, while WO recorded a ledge and fractured file, but for PTN system, it verified an outer widening and ledge. Only one WO file fractured, with no deformation observed in the other instruments. No significance was recorded among the width measurements in the different levels.

Conclusion

ProTaper next achieved faster cutting than the ProTaper and WO file systems. PTN maintained the best apical termination position and produced the least canal aberration, followed by WO and ProTaper.

Micro-CT Study on the Supplementary Effect of XP-Endo Finisher R after Endodontic Retreatment with Mtwo-R

BACKGROUND

During the course of a non-surgical orthograde endodontic retreatment, supplementary instrumentation is usually required for better removal of root canal filling material.

AIM

The aim of this study was to assess the effectiveness of XP-Endo Finisher R in endodontic retreatment of oval root canals.

MATERIALS AND METHODS

The study was performed on extracted mandibular incisors preliminary cut at the cementoenamel junction. The root canals of 12 extracted lower central incisors were initially shaped with the rotary nickel-titanium system XP-Endo Shaper (30/.04) and filled with continuous waves of condensation. Root canal retreatment was performed with the МTwo Retreatment - R1 (15/.05) and R2 (25/.05) files, followed by the XP-Endo Finisher R (30/.00). Three micro-computed tomography scans were performed during the course of the experiment: 1) after the filling of the root canals, 2) after the first retreatment procedures, and 3) after the supplementary shaping. Kolmogorov-Smirnov test for normality and Friedman and Kruskal-Wallis tests for comparison of several independent samples.

RESULTS

There were no statistically significant differences in the percentage of removed obturation material in the different parts of the root canal after the use of Mtwo-R (P = 0.649) and XP-Endo Finisher R (P = 0.934). The additional instrumentation with XP-FR reduced the percentage of the remaining root canal filling insignificantly (P = 0.190).

CONCLUSIONS

The combined action of Mtwo-R retreatment files and XP-Endo Finisher R resulted in significant reduction of the amount of root canal filling material. Nevertheless, none of the examined rotary systems guaranteed its complete removal.

Transportation and Centering Ability of Kedo-S Pediatric and Mtwo Instruments in Primary Teeth: A Cone-beam Computed Tomography Study

Background

Cleaning and debriding the canals and preserving the shape of the canal without deformation is the primary goals of pulpectomy. Transportation is a critical endodontic iatrogenic fault that could cause a catastrophe. This study evaluated the canal centering ability and canal transportation caused by Kedo-S pediatric and Mtwo instruments, using a cone-beam computed tomography (CBCT).

Materials and methods

This in vitro study was performed on distal roots of 50 primary mandibular first molars. The teeth were scanned using CBCT and randomly divided into two groups. The canals were then prepared using either Kedo-S or Mtwo files (n = 25). The instrumented canals were rescanned. The scanned volumes were sectioned at 2, 4, and 6 mm from cementoenamel junction (CEJ). Canal transportation (CT) and instrument centering ability were estimated and compared in both groups.

Results

The mean values for two study groups were compared. T -test was used to determine theP value. The Levene's test was used to test the significance between two groups. The two groups showed similar results in terms of transportation and centering ability (P > 0.05).

Conclusion

Kedo-S pediatric and Mtwo instruments demonstrated similar canal centering ability and CTs.

How to cite this article

Haridoss S, Rakkesh KM, Swaminathan K. Transportation and Centering Ability of Kedo-S Pediatric and Mtwo Instruments in Primary Teeth: A Cone-beam Computed Tomography Study. Int J Clin Pediatr Dent 2022;15(S-1):S30-S34.

Computed Tomographic Assessment of Remaining Dentin and Risk of Perforation after Kedo-S and Mtwo Rotary Instrumentation in Root Canals of Primary Teeth: An In Vitro Study

Background

Root canal cleaning is a key step in the endodontic treatment of the primary molars. An innovative generation of endodontic instruments has been devised with the aim of emerging better procedures. The objective of the study is to assess the preparation of time, the risk of lateral perforation, and the removal of dentin from Kedo-S and Mtwo rotary instruments on primary teeth.

Study design

This is an in vitro experimental study comparing the two groups.

Materials and methods

A total of 50 extracted mandibular primary first molars are collected, divided randomly into two groups of 25 teeth each. Group I: Kedo-S Pediatric rotary file, Group II: Mtwo rotary file. Distal canal is standardized for evaluation and teeth are sectioned at the CEJ. The teeth were instrumented according to manufacturer's guideline. Both the groups are scanned before and after instrumentation of the canal using cone-beam computed tomography (CBCT) and values are evaluated.

Results

Compared with Mtwo files, Kedo-S files need less instrumentation time and limited lateral perforation. No statistical differences were reported between the instrumentation of Kedo-S and Mtwo with regard to the amount of dentin removed.

Conclusion

In pediatric endodontics, Kedo-S pediatric rotary file can be considered an effective alternative to traditional rotary files because it requires less instrumentation time and preserves dentin thickness.

How to cite this article

Swaminathan K, Rakkesh KM, Haridoss S. Computed Tomographic Assessment of Remaining Dentin and Risk of Perforation after Kedo-S and Mtwo Rotary Instrumentation in Root Canals of Primary Teeth: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(S-1):S87-S91.

Longitudinal craze line propagation in human root dentin after instrumentation with NiTi rotary files of different instrument tapers after long-term chewing simulation

Objectives

The aim of this study was to investigate whether file design and taper significantly influence microcrack initiation during machine preparation.

Materials and methods

Sixty extracted teeth with straight single canals were selected. The teeth were randomly assigned to four groups based on their root canal anatomy and the corresponding NiTi rotary file system (I, Mtwo; II, ProTaper Universal; III, F6 SkyTaper; control, no preparation and filling). The root canals of the experimental groups were filled using the single-cone technique. The tested teeth were all subjected to a mechanical chewing simulation with flat lead loading over a period of 3 years (corresponding to 150,000 cycles). The teeth were checked for dentinal defects (accumulative crack growth in length) under the digital microscope (Keyence VHX-5000) at time 0 (baseline prior to chewing simulation) and after 3, 6, 12, 24, and 36 months of loading. The cumulative crack increase was statistically analyzed using the Kruskal–Wallis test, Jonckheere–Terpstra test, and the Wilcoxon rank-sum test. The significance was set at p < 0.05.

Results

In contrast to preparation with greater-tapered instruments, ProTaper Universal (group II) and F6 SkyTaper (group III) instrumentation with the smaller tapered Mtwo files (group I) showed less accumulative propagation of craze lines (p < 0.05) at all time points.

Conclusion

Instruments with greater taper for root canal instrumentation should be used with care to avoid negative long-term effects in the form of propagation of dentinal defects over time. A positive cutting-edge angle and a smaller taper have a positive effect on a lower craze line development.

Clinical relevance

Instruments with a positive cutting-edge angle and a smaller taper are beneficial for the long-term preservation of dentinal tooth structure.

Canal transportation and centering ability of root canals prepared using rotary and reciprocating systems with and without PathFiles in cone-beam computed tomography-based three-dimensional molar prototypes

Background:

It is important to use instruments that cause minimal changes in the canal path for root canal preparation. There is inadequate literature comparing rotary and reciprocating systems and hand files. No study used three-dimensional printed models to compare rotary, reciprocating, and hand files.

Aims:

We aimed to assess the canal transportation and centering ability of WaveOne Gold, ProTaper Gold, and NiTi Flex K-file systems with and without glide path preparation.

Material and Methods:

Forty-nine resin models were randomly divided into Group I A – WaveOne Gold with WaveOne Gold Glider and Group I B – WaveOne Gold without glide path; Group II A – ProTaper Gold with ProGlider and Group II B – ProTaper Gold without glide path; and Group III A – NiTi Flex K-files with no. 10 stainless steel K-file and Group III B – NiTi Flex K-files without glide path. Pre- and postinstrumentation cross-sectional images at levels 3, 5, 7, 9, and 11 mm were compared.

Results:

WaveOne Gold caused the least canal transportation and improved centering ability (P < 0.05). NiTi Flex K-files transported the canal more than others in the apical levels (3, 5 mm). Glide path creation reduced canal transportation and improved canal-centering ability.

Conclusions:

WaveOne Gold system has better centering ability and lesser canal transportation than ProTaper Gold and NiTi Flex K-file. Glide path creation reduced canal transportation and improved canal-centering ability.

Shaping ability of two root canal instrumentation systems in oval-shaped canals: A microcomputed tomography study

The objective was to evaluate the shaping ability of XP-endo Shaper and Mtwo systems in oval-shaped canals preparation by microcomputed tomography (micro-CT) along the entire canal. The volume, surface area and percentage of unprepared area were evaluated by image processing in entire canal and apical third (5 mm). Apical transportation and centring ability were evaluated at 3, 5 and 7 mm from the apex. Forty single-canal oval canines were paired in two groups (n = 20) according to the instrumentation system: XP-endo Shaper and Mtwo. The teeth were scanned by micro-CT before and after instrumentation, using a thermal vat at 37°C. The XP-endo Shaper system was more effective in the instrumentation of oval-shaped canals when compared to Mtwo system, resulting in greater volume increases and lower percentage of unprepared canals walls in apical region. Regarding apical transportation and centring ability, no statistical difference was observed.

Residual smear layer after root canal instrumentation by using Niti, M-Wire and CM-Wire instruments: A scanning electron microscopy analysis

Objective:

The purpose of this study was to compare the amount of residual smear layer after root canal instrumentation by using Ni-Ti, M-Wire, and CM-Wire instruments.

Materials and Methods:

Seventy-two mandibular incisors were randomly divided into six groups according to the system used: WaveOne (WO), Reciproc (RP), Unicone (UC), ProTaper Next (PN), Mtwo (MT), and HyFlex (HF). Afterward, the specimens were cleaved in the mesiodistal and buccolingual direction for analysis by scanning electron microscopy.

Results:

Considering both directions and root canal thirds, there was no difference between HF, MT, and PN. RP, UC, and WO presented a significant difference between the directions, and the cervical third showed a significantly smaller quantity of residual smear layer compared with the apical third. When the systems were compared among them, there was a significant difference only between RP and WO.

Conclusions:

Residual smear layer observed after instrumentation with the different systems was similar, except for quantities between the reciprocating systems.

Comparative evaluation of instrumentation timing and cleaning efficacy in extracted primary molars using manual and NiTi rotary technique - Invitro study

Aim

To compare the timing of instrumentation and cleaning efficacy between manual K files and NiTi rotary files in extracted primary molars.

Study design

in-vitro study was conducted in 90 root canals of extracted primary molars which were subdivided in three groups viz. Control (No instrumentation), Manual (K files), Rotary (ProFiles) with 30 canals in each group. Mesiobuccal (MB) and Mesiolingual (ML) canals of mandibular molars, and MB and Distobuccal (DB) canals of maxillary molars were included in the test group whereas Distal canals in mandibular molars and Palatal canals in maxillary molars were included in the control group.

Method

Teeth were mounted and canals were injected with India ink to stain the canal walls. Canal preparation was done as per the group. After instrumentation, teeth were demounted, decalcified and cleared to make them transparent for scoring according to the extent of removal of India ink. Timing of instrumentation and cleaning efficacy of canals in coronal, middle and apical thirds were assessed in each sample.

Results

Mean timing of instrumentation in rotary group was 3.54 ± 1.14 min and 4.32 ± 1.04 min in manual group. Mean cleaning efficacy scores in manual and rotary groups were 2.03 and 1.66 in coronal third, 1.08 and 1.18 in middle third and 0.67 and 1.08 in apical third respectively. Inter-group comparisons showed no statistically significant difference in cleaning efficacy among test groups in all thirds of root canals.

Conclusion

NiTi rotary technique has comparable cleaning efficacy, with significantly less timing of instrumentation compared to manual K-files.

Evaluation of the usage-induced degradation of Genius and Reciproc nickel-titanium reciprocating instruments

The aim of this study was to characterize the main features and the usage-induced degradation of the Genius file after four severely curved root canal instrumentations and to compare their properties to the Reciproc files. Brand new and ex vivo used files were analysed by scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometry (EDS), differential scanning calorimetry (DSC), X-ray diffraction (XRD), optical metallography, and nano-indentation to disclose their morphological, chemical, mechanical, thermal, and phase composition features. Nano-indentation data were statistically analysed using the Student's t test for normal distribution or the Kolmogorov-Smirnov test for not-normal distributions. SEM analysis showed the presence of micro-cracks near the tip on both files after ex vivo usage test. EDS analysis confirmed that both files are manufactured from an almost equiatomic NiTi alloy. DSC analysis revealed that the transition temperature of the Genius is below 20 °C, while that of the Reciproc is above 20 °C. XRD analysis of Genius files identified cubic B2 austenite with minor peaks of residual monoclinic B19 martensite, while the contemporaneous presence of martensite, austenite and hexagonal R-phase was observed in the Reciproc files. Significant differences in nanohardness and modulus of elasticity (P < .05) were observed in both Genius and Reciproc files before and after use. The collected results showed that both instruments can be safely used as single-use files.

Shaping effectiveness and surface topography of reciprocating files after multiple simulated uses

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer's instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals.

A Comparative Evaluation of Intracanal Calcium Hydroxide Removal with Hand File, Rotary File, and Passive Ultrasonic Irrigation: An In Vitro Study

Aim

The aim of this study was to compare the effectiveness of hand file (K-file), rotary file (HERO shaper), and passive ultrasonic irrigation (PUI; U-file) in removing Ca(OH)₂ from the root canal.

Materials and Methods

Thirty single-rooted teeth were collected and decoronated to standardize the length to 14 mm. Cleaning and shaping were conducted using HERO shaper rotary files (up to no. 25, 4% taper). Ca(OH)₂ powder was mixed with normal saline and filled into the canals using lentulo spiral and the orifice was sealed with zinc oxide eugenol. After 7 days of incubation, samples were divided into three groups of 10 samples each: Group I (hand files)-no. 20 K-file; Group II (rotary files)-no. 25, 4% HERO shaper; Group III (PUI)-no. 20 U-file. Ca(OH)₂ paste was removed using 2 mL of 3% sodium hypochlorite solution followed by 1-minute activation of the respective file system. All the samples were finally irrigated with 17% ethylenediaminetetraacetic acid and flushed with distilled water.

Results

Ultrasonic group was more effective in removing Ca(OH)₂ followed by HERO shaper and hand file.

Conclusion

It was concluded that PUI had the highest ability to remove Ca(OH)₂ from the root canal walls.

Nickel-titanium instruments in endodontics: a concise review of the state of the art

The introduction of automated instrumentation in endodontics represented a major advance in progress for this specialty, with improvements in the quality and predictability of root canal preparation and a significant reduction in procedural errors. In recent years, endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments. In addition, new movements have also been incorporated to offer greater safety and efficiency, optimizing the properties of the NiTi alloy, especially through eccentric rotary motion. An understanding of the mechanical properties of these new NiTi instruments and their effect on the clinical performance of root canal preparation is essential if dental practitioners are to select the instruments that provide optimal clinical outcomes, especially in curved or flattened canals. The objective of this literature review is to present and discuss the characteristics of the NiTi alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of NiTi instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation.

Shaping ability of four root canal instrumentation systems in simulated 3D-printed root canal models

Introduction

The aim of this study was to compare the shaping ability of four root canal preparation systems in newly developed 3D-printed root canal models.

Materials and methods

For this study, 1080 3D-printed acrylic resin blocks with nine different root canal configurations were produced. They were prepared with Reciproc R25 (#25), F6 SkyTaper (#25 and #30) F360 (#25 and #35) and One Shape (#25) (N = 30 per system). Pre- and post-instrumentation images were superimposed for evaluation of the centering ratio of the different systems. Ledges, instrument fractures and preparation times were also recorded. Analysis of variance (ANOVA) and post-hoc Tukey tests were conducted, comparing the mean canal centering ratios and the mean preparation times.

Results

There were significant differences between all systems regarding the centering ratios in the different root canal configurations (ANOVA p < 0.001). The root canal configuration had considerable effect on the centering ratio of the instruments. The best overall mean centering ratios were achieved with F6 SkyTaper #25 instruments especially in canal configurations with big curvature angles and radii, while F360 #35 was least centered especially in canals with small curvature angles and radii. Most ledges occurred with OneShape, while it was the significantly (p < 0.001) fastest preparation system (86.7 s (SD 13.53)) and Reciproc the significantly (p < 0.001) slowest (103.0 s (SD 20.67)).

Conclusion

3D-printed root canals are suitable to produce challenging canal configurations and to investigate the limitations of root canal instruments. We found that all instruments caused canal transportations. However, F6 SkyTaper #25 files had better overall centering ratios than the other instruments. In canal configurations with small curvature radii, the centering ratio of some instruments is low and the probability for ledges is increased.

Canal shaping of different single-file systems in curved root canals

Background/Purpose

This study compared maintenance of canal anatomy, occurrence of apical transportation, and working time observed after instrumentation with One Shape New Generation rotary system (Micro-Mega), with those observed after instrumentation with Reciproc (VDW) and WaveOne (Dentsply-Maillefer) reciprocating systems.

Materials and methods

The mesial canals of 45 mandibular molars (curvature angles between 35° and 45°) were selected. Specimens were randomly divided into three groups, and canal preparations were performed using One Shape, Reciproc, or WaveOne systems (size #25). A digital double radiographic technique was used to determine apical transportation and change in angle of curvature. Also, working time and instrument failures were recorded. Data were statistically analyzed.

Results

During preparation, no file fractured. No statistically significant differences were found among groups. No system showed a significantly faster preparation time than others (P > 0.05). All instruments maintained the original canal curvature well and were safe to use.

Conclusion

Both continuous rotary instrument and reciprocating systems did not have any influence on the presence of apical transportation or caused an alteration in angle of canal curvature.

Effect of retreatment instruments on microcrack formation: a microcomputed tomography study

INTRODUCTION

The purpose of this study was to compare the occurrence of microcracks in teeth prepared with different retreatment systems using microcomputed tomography (micro-CT).

METHODS

Forty-two freshly extracted mandibular premolar teeth were used. The root canals were instrumented with stainless steel K-files to an apical size of 35/.02 using the balanced-force technique and were obturated using the passive compaction technique. The specimens were divided into 3 experimental groups according to retreatment system used (n = 14): ProTaper Universal retreatment (PTUR), Mtwo retreatment (MTR), or D-RaCe retreatment (D-RC) systems. Each specimen was scanned using a high-resolution micro-CT system before instrumentation, after obturation, and after the removal of the filling material. The images were evaluated, and the presence of microcracks was recorded.

RESULTS

The PTUR system demonstrated the highest percentage, while MTR and D-RC retreatment systems resulted in similar numbers of microcracks.

CONCLUSIONS

Clinicians should be aware that all retreatment systems may cause microcracks.

Influence of heat treatment on cyclic fatigue and cutting efficiency of ProTaper Universal F2 instruments

BACKGROUND/PURPOSE

Heat pretreatment can improve the cyclic fatigue life of nickel-titanium (NiTi) instruments. This study evaluated the effects of two different heat treatments on the cyclic fatigue resistance and cutting efficiency of ProTaper Universal F2 files.

MATERIALS AND METHODS

The files were divided into three groups: no treatment (control), heat treatment at 400°C (HT400) and heat treatment at 600°C (HT600). The phase transformation of the files was evaluated by differential scanning calorimetry. In cyclic fatigue tests, the differences in file performance in four simulated canals among the three groups were assessed. The cutting efficiency was tested at four cutting portions (3 mm, 6 mm, 9 mm, and 12 mm) from the tip of the file.

RESULTS

Differential scanning calorimetry showed a prolonged phase transformation of the files only after 600°C treatment. At 3 mm cutting portion, 400°C heat-treated files had significantly better cutting ability than those in the control group. However, the files in the HT600 group had significantly lower cutting efficiency than those in the other two groups at the four tested positions. In the cyclic fatigue test, fatigue lives of the files after 400°C and 600°C treatment were prolonged from 2.1 to 2.8 times and from 1.7 to 5.5 times, respectively.

CONCLUSION

Although 600°C treatment increased resistance to cyclic fatigue, it reduced the cutting efficiency of the files. The 400°C treatment maintained the cutting ability and prolonged the cyclic fatigue life of the files. Therefore, for clinical use of ProTaper Universal F2 files, 400°C pretreatment is a better choice than 600°C pretreatment.

Influence of three Ni-Ti cleaning and shaping files on postinstrumentation endodontic pain: A triple-blinded, randomized, controlled trial

Aim:

This randomized, controlled trial evaluated the incidence of postinstrumentation pain on using two different rotary Ni–Ti and one reciprocating Ni–Ti cleaning and shaping systems.

Materials and Methods:

Asfter sample size estimation, a total of 152 patients were randomized to three groups (Group WO [WaveOne], Group PU [ProTaper Universal], and Group Mt [Mtwo]). Selection of patients was based on root curvature, periapical lesion, vitality, gender, and diagnosis of the patient. A similar clinical protocol was followed and endodontic treatment was performed. Pre- and post-instrumentation pain scores (2, 4, 6, 8, 12, 36, and 48 h) were recorded using visual analog scale score. Kruskal–Wallis test was done for overall comparison of the groups. Bonferroni-corrected Mann–Whitney test was done for pair-wise comparisons and Friedman test was done to compare pain between time points in each file system (P < 0.05).

Results:

All preinstrumentation pain values were higher than postinstrumentation pain values (P < 0.05). At 48 h, patients in Group WO experienced more pain compared to the other two groups. Pain scores of nonvital teeth were significantly higher when compared to vital teeth. Among nonvital teeth, patients in Group WO had early onset of pain at 6 h and lasted till 48 h, whereas pain started at 12 h and lasted till 36 and 48 h for Group Mt and Group PU, respectively.

Conclusion:

Patients treated with WaveOne files experienced more pain when compared to the other files. Nonvital teeth experienced more pain compared to vital teeth. Group Mt had the lowest postinstrumentation pain.

'Volumetric analysis of hand and rotary root canal instrumentation and filling in primary teeth using Spiral Computed Tomography' - an invitro study

AIM

To compare and evaluate the volumetric analysis of pre- and post-root canal instrumentation in primary teeth using hand and rotary files and also to analyse the volume of root canal filling.

MATERIALS AND METHODS

A total of 20 primary teeth were divided into two groups randomly and subjected to spiral computed tomography (SCT) analysis before and after instrumentation. For manual technique (Group 1), teeth were prepared using K files and rotary (Group 2) preparation was performed with Mtwo files. Volumetric enlargement was calculated using Osirix software. Root canals were then filled with rotary lentulospiral using zinc oxide-eugenol cement (ZOE). The filled volume in each canal was measured using SCT and the percentage of obturated volume was calculated. The data were statistically analysed using paired t-tests.

RESULTS

There was a statistically significant difference in the volume of root canal enlarged in both the groups. Rotary files showed significant increase in the volume compared to K files. Mtwo instrumented root canals showed good obturated volume compared to manual technique, although voids were common in both the groups.

CONCLUSION

Rotary root canal instrumentation may be indicated for utilization in primary teeth, for enhancing root canal preparation and good quality of root canal filling.

Rotary endodontics in primary teeth - A review

Endodontic treatment in primary teeth can be challenging and time consuming, especially during canal preparation, which is considered one of the most important steps in root canal therapy. The conventional instrumentation technique for primary teeth remains the "gold-standard" over hand instrumentation, which makes procedures much more time consuming and adversely affects both clinicians and patients. Recently nickel-titanium (Ni-Ti) rotary files have been developed for use in pediatric endodontics. Using rotary instruments for primary tooth pulpectomies is cost effective and results in fills that are consistently uniform and predictable. This article reviews the use of nickel-titanium rotary files as root canal instrumentation in primary teeth. The pulpectomy technique is described here according to different authors and the advantages and disadvantages of using rotary files are discussed.

Evaluation of cutting ability and plastic deformation of reciprocating files

This in vitro study evaluated the cutting ability of reciprocating files and the deformations caused by their multiple use. Five Reciproc® R25 files were divided into five groups for 10 simulated root canal preparations each. The resin blocks were weighed and photographed (12.5X and 20X) before and after preparation. The canals were prepared according to the manufacturer's instructions. Enlargement of the root canals was evaluated by comparison of pre- and post-preparation images using a computer software. The preoperative and postoperative weight differences determined the cutting ability of repeatedly used instruments. The data were analyzed using Lilliefors and Friedman statistical tests. The cutting ability and enlargement of the canals gradually decreased after each use, with significant differences observed at the 8th and 9th repetitions, respectively. There was no evidence of file deformation. The cutting ability and enlargement of the simulated canals gradually decreased when a reciprocating file was used up to 10 times.

Shaping ability of reciprocating single-file and full-sequence rotary instrumentation systems in simulated curved canals

Objective:

The purpose of this study was to evaluate the shaping ability of three nickel-titanium systems in simulated curved canals.

Materials and Methods:

Sixty simulated canals were prepared to apical size 25 with Reciproc, S5, and twisted file (TF) instruments. Standardized pre and postoperative images were taken using a digital camera, were superimposed and aberrations were recorded. Material removal was measured at five points: The canal orifice, halfway to the orifice, beginning of the curve, the apex of the curve, and end-point. The data were analyzed using Kolmogorov–Smirnov, analysis of variance, and Tukey tests.

Results:

The mean total width of the prepared canals in the Reciproc group was greater than the TF and S5 groups at halfway to the orifice, the beginning of the curve, the apex of the curve, and the end-point (P < 0.05). Mean absolute transportation was always <0.16 mm; however, significant differences occurred between the three systems at the orifice, halfway to the orifice, and the beginning of the curve (P < 0.05). TF created minimal absolute transportation at halfway to the orifice and the beginning of the curve, and greater absolute transportation at the orifice compared with the Reciproc and S5 instruments. However, the difference between the S5 and TF groups was not statistically significant at halfway to the orifice (P > 0.05).

Conclusions:

Under the conditions of the study, Reciproc produced widest canal shapes. TF provided more centered apical preparation and maintained the original canal shape well.

Evaluation of Root Canal Preparation Using Rotary System and Hand Instruments Assessed by Micro-Computed Tomography

Background

Complete mechanical preparation of the root canal system is rarely achieved. Therefore, the purpose of this study was to evaluate and compare the root canal shaping efficacy of ProTaper rotary files and standard stainless steel K-files using micro-computed tomography.

Material/Methods

Sixty extracted upper second premolars were selected and divided into 2 groups of 30 teeth each. Before preparation, all samples were scanned by micro-computed tomography. Thirty teeth were prepared with the ProTaper system and the other 30 with stainless steel files. After preparation, the untouched surface and root canal straightening were evaluated with micro-computed tomography. The percentage of untouched root canal surface was calculated in the coronal, middle, and apical parts of the canal. We also calculated straightening of the canal after root canal preparation. Results from the 2 groups were statistically compared using the Minitab statistical package.

Results

ProTaper rotary files left less untouched root canal surface compared with manual preparation in coronal, middle, and apical sector (p<0.001). Similarly, there was a statistically significant difference in root canal straightening after preparation between the techniques (p<0.001).

Conclusions

Neither manual nor rotary techniques completely prepared the root canal, and both techniques caused slight straightening of the root canal.

Assessment of root canal enlargement using Mtwo and BioRace rotary files

Objective. To evaluate root canal enlargement following mechanical shaping using 2 nickel titanium rotary systems. Material and Methods. Forty single-rooted teeth were immersed in resin and sectioned perpendicular to the long axis at 4, 8, and 12 mm from the apex. Digital capture of sections was performed before and after canal instrumentation using Mtwo and BioRace instruments. The area increase of endodontic space was calculated by subtraction. Results. The use of both instruments has allowed the removal of great amounts of dentin from the canal walls, even when the endodontic morphology is characterized by awkwardness to reach recesses. Conclusions. Both procedures seem to be valid and no differences were found between Mtwo and BioRaCe considering the amount of dentin removed at different distances from the apex.

Comparison of Time Required by D-RaCe, R-Endo and Mtwo Instruments for Retreatment: An in vitro Study

INTRODUCTION

To evaluate and compare the amount of time required by three rotary NiTi instruments in removing gutta-percha from root canal during retreatment with hand file as control.

MATERIALS AND METHODS

Eighty human mandibular premolars with single straight root canals were prepared and obturated by cold lateral condensation with gutta-percha and AH Plus sealer. After two weeks, the 80 teeth were divided into one control group and 3 retreatment groups (n = 20 each). Gutta-percha was removed using H-files, the D-RaCe, or the Mtwo or the R-Endo retreatment systems. Retreatment time was calculated using stopwatch.

RESULTS

D-RaCe and Mtwo required significantly less time than R-Endo and hand file. Hand file took maximum time, which was significantly slower than all groups. However, D-RaCe and Mtwo retreatment time was statistically insignificant.

CONCLUSION

D-RaCe and Mtwo remove gutta-percha faster than R-Endo and Hand files.

Cutting efficiency of instruments with different movements: a comparative study

OBJECTIVES

The aim of the present study was to evaluate the cutting efficiency of two new reciprocating instruments, Twisted File Adaptive and WaveOne Primary.

MATERIAL AND METHODS

10 new Twisted File Adaptive (TF Adaptive) (SybronEndo, Glendora, CA, USA) and 10 new WaveOne Primary files (Dentsply Maillefer, Ballaigues, Switzerland) were activated using a torque-controlled motor, respectively TFA motor (SybronEndo, Glendora, CA, USA) and Silver motor (VDW, Munich, Germany). The device used for the cutting test consisted on a mainframe to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Mean and standard deviations of each group were calculated and data were statistically analyzed with one-way ANOVA and Bonferroni t test (P < 0.05).

RESULTS

TF Adaptive displayed significantly greater maximum penetration depth than WaveOne Primary (P < 0.05). In fact, TF Adaptive instruments (Group 1) cut the Plexiglas block to a mean depth of 8.7 (SD 0.5) mm, while WaveOne Primary instruments cut the Plexiglas block to a mean depth of 6.4 (SD 0.3) mm.

CONCLUSIONS

Twisted File Adaptive instruments demonstrated statistically higher cutting efficiency than WaveOne instruments.

Comparison of Hero 642 and K3 rotary nickel-titanium files in curved canals of molars and a systematic review of the literature

The aim of the present study was to compare the root canal preparation ability of rotary nickel-titanium (NiTi) Hero 642 and K3 files in curved mandibular or maxillary molars. A total of 40 extracted mandibular molars with two separate mesial canals, an apical width of approximately size ≤15 and a root canal curvature of 15–30° were randomly divided into two groups and instrumented using Hero 642 (n=20) or K3 files (n=20). Canal straightening, working length, transportation, cross-sectional area, minimum dentin thickness and the canal angle curvature degree were examined, and a systematic review of the literature was conducted. No statistically significant differences were observed between the two groups with regard to the mean degree of straightening, mean change in working length, mean transportation, amount of dentin removed or remaining minimum dentin thickness (P>0.05). The canal angle curvature decreased in the two groups postoperatively. The systematic review identified six studies, and overall the two files performed similarly in the majority of categories examined. Therefore, the rotary NiTi Hero 642 and K3 files demonstrated comparable shaping abilities and maintenance of working length.

Cleaning capacity of hybrid instrumentation technique using reamer with alternating cutting edges system files: Histological analysis

Aim:

The aim of the following study is to evaluate the cleaning capacity of a hybrid instrumentation technique using Reamer with Alternating Cutting Edges (RaCe) system files in the apical third of mesial roots of mandibular molars.

Materials and Methods:

Twenty teeth were selected and separated into two groups (n = 20) according to instrumentation technique as follows: BioRaCe - chemomechanical preparation with K-type files #10 and #15; and files BioRaCe BR0, BR1, BR2, BR3, and BR4; HybTec - hybrid instrumentation technique with K-type files #10 and #15 in the working length, #20 at 2 mm, #25 at 3 mm, cervical preparation with Largo burs #1 and #2; apical preparation with K-type files #15, #20, and #25 and RaCe files #25.04 and #30.04. The root canals were irrigated with 1 ml of 2.5% sodium hypochlorite at each change of instrument. The specimens were histologically processed and photographed under light optical microscope. The images were inserted onto an integration grid to count the amount of debris present in the root canal.

Results:

BioRaCe presented the highest percentage of debris in the apical third, however, with no statistically significant difference for HybTec (P > 0.05).

Conclusions:

The hybrid technique presented similar cleaning capacity as the technique recommended by the manufacturer.

The evaluation of two rotary instrumentation techniques under "operator-related variables" standardized conditions

Objective:

We aimed here to evaluate the enlargement characteristics of two nickel-titanium rotary instrument systems that use two different preparation techniques, in simulated root canals under “operator-related variables” standardized conditions.

Materials and Methods:

A total of 40 simulated canals in resin blocks were divided into two groups as the Mtwo group for use with a single-length technique and the ProTaper instrument system group for use with crown down technique. To standardize the operator-related variables, all preparations were carried out with a computer controlled device that was developed and used previously as described in a published study. The pre- and post-operative digital images of the canals were superimposed and measured at 11 levels from the apical tip. The distances between the pre- and post-operative outer lines of the root canals were measured at both the inner and outer sides of the curve. The amount of removed material and the symmetry of the preparations were evaluated. Statistical analyses were performed with Mann-Whitney test.

Results:

Significantly more material was removed by Mtwo at 9 levels and by ProTaper at 2 levels (P < 0.05) while no significant difference was determined at 11 levels. The preparations made with ProTaper were more symmetrical at 4 levels while no significant difference was determined at 7 levels.

Conclusion:

Mtwo removed significantly more material than ProTaper at different levels of the curved root canals. Mtwo and ProTaper made symmetrical preparations and maintained the original shape of the root canal at different levels under controlled operator-related variables.

A new device to test cutting efficiency of mechanical endodontic instruments

BACKGROUND

The purpose of the present study was to introduce a new device specifically designed to evaluate the cutting efficiency of mechanically driven endodontic instruments.

MATERIAL AND METHODS

Twenty new Reciproc R25 (VDW, Munich, Germany) files were used to be investigated in the new device developed to test the cutting ability of endodontic instruments. The device consists of a main frame to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1mm. The instruments were activated by using a torque-controlled motor (Silver Reciproc; VDW, Munich, Germany) in a reciprocating movement by the "Reciproc ALL" program (Group 1) and in counter-clockwise rotation at 300 rpm (Group 2). Mean and standard deviations of each group were calculated and data were statistically analyzed with a one-way ANOVA test (P<0.05).

RESULTS

Reciproc in reciprocation (Group 1) mean cut in the Plexiglas block was 8.6 mm (SD=0.6 mm), while Reciproc in rotation mean cut was 8.9 mm (SD=0.7 mm). There was no statistically significant difference between the 2 groups investigated (P>0.05).

CONCLUSIONS

The cutting testing device evaluated in the present study was reliable and easy to use and may be effectively used to test cutting efficiency of both rotary and reciprocating mechanical endodontic instruments.

Reduction in Enteroccocus faecalis counts - a comparison between rotary and reciprocating systems

AIM

To compare the chemomechanical reduction and regrowth of Enterococcus faecalis between rotary and reciprocating systems in root canal preparation.

METHODOLOGY

Seventy-six single-rooted human mandibular premolars were selected and standardized to 15 mm in length. Root canals were enlarged up to a size 25 K-file and irrigated with distilled water and then were infected with E. faecalis for 4 weeks. The specimens were divided into 3 groups (n = 24) for instrumentation with Mtwo, Twisted File and WaveOne. Each group was further divided into two subgroups (n = 12) according to the irrigant used: distilled water or 5.25% sodium hypochlorite (NaOCl). Before and after rotary preparation, microbiological samples were collected using three sterilized paper points, and efficacy was expressed as reduction in percentage. The proportion of grown samples for 60 days was evaluated using nonparametric Kaplan-Meier survival analysis. Differences amongst groups were tested using the log-rank test at a significance level of 0.05.

RESULTS

In the main root canal, the percentage reduction in the distilled water and 5.25% NaOCl groups ranged from 95.9% to 100%, with no significant differences amongst the three systems (P > 0.05). The bacterial regrowth in NaOCl groups revealed that Mtwo had the lowest number of samples regrown at 60 days, giving statistically significant differences with respect to Twisted File (P = 0.029) and WaveOne (P = 0.005).

CONCLUSIONS

Reciprocating and rotary systems resulted in similar percentage reduction in E. faecalis when using either distilled water or 5.25% NaOCl solution. Over time, the Mtwo system was more effective regarding disinfection.

An ex vivo comparative analysis on shaping ability of four NiTi rotary endodontic instruments using spiral computed tomography

Objective:

Analysis of shaping ability of four different rotary endodontic instruments using spiral computed tomography (CT).

Materials and Methods:

Eighty freshly extracted human mandibular first molars were used in the present study. Samples were randomly divided into four experimental groups with twenty samples in each group. Images of mesiobuccal canal of each sample were obtained pre- and post-operatively using spiral CT. All samples were prepared using their respective endodontic file systems (group I - ProTaper, group II - K3, group III - RaCe, and group IV - Mtwo). Image analyses were done using image analysis software for evaluation of canal transportation and centering ability. Data was then statistically analyzed using analysis of variance.

Results:

There was no statistically significance in transportation in their intergroup difference at any of the three locations (coronal, middle, and apical third). In centering ability there was no statistically significance in the coronal and middle third of the intergroup. However, there was a statistically significance of (P = 0.044) at the apical third between all the groups.

Conclusion:

Canals prepared with ProTaper had more canal transportation at all the three levels of root canal (coronal, middle, and apical third). Canals prepared with Mtwo were well centered at coronal and middle third whereas with RaCe canals were centered only at the apical third. All instruments showed some degree of canal aberrations in terms of shaping ability.

Assessment of the separation incidence of mtwo files used with preflaring: prospective clinical study

INTRODUCTION

The Mtwo rotary system was designed to be used at full length without performing previous cervical enlargement or creating a manual glide path. However, to our knowledge, no study has investigated whether preflaring influences instrument fatigue. The purpose of this clinical study was thus to evaluate the incidence of separation of Mtwo instruments during the preparation of mandibular and maxillary molars and bicuspids that was preceded by cervical preflaring.

METHODS

A total of 556 treatments were performed by 6 endodontists after calibration. Cervical enlargement and exploration with hand files were undertaken before using the rotary files. The canals were negotiated with small K-type hand files. Cervical and middle thirds were prepared with hand files and Gates-Glidden burs. Irrigation was performed with 2 mL of 2.5% NaOCl after each instrument. The working length was established, and the apical third was prepared with Flexofiles until a #15 file could reach the working length, establishing a glide path. The Mtwo instruments were used following manufacturer's recommendations and disposed of after being used in 5 teeth. Each file was examined under ×8 magnification after use. In cases of file deformation or separation, the entire file kit was no longer used, except when using the 10.04 file. Because of its high failure rate, which is well-established in the related literature, this instrument could be replaced at any time.

RESULTS

Separation and deformation rates were 1.98% and 28.78%, respectively. Ten of the total separations observed occurred with the 10.04 file (90.01%) and one with the 15.05 file (9.09%).

CONCLUSIONS

The use of Mtwo rotary instruments preceded by cervical preflaring with manual files and Gates-Glidden burs provides a low separation incidence.