Micro–computed Tomographic Evaluation of the Shaping Ability of 3 Reciprocating Single-File Nickel-Titanium Systems on Single- and Double-Curved Root Canals

Micro-computed tomography analysis of shaping ability of nickel-titanium instruments activated by continuous rotation or adaptive motion

This study assessed the ability of Twisted File Adaptive (TFA), TruNatomy (TRN) and VDW.Rotate (VR) instruments activated by continuous rotation (CR) and adaptive motion (AM) to shape curved root canals. Thirty mandibular molars with two separate mesial canals 20°-40° curved were collected and scanned using micro-computed tomography (μCT). The canals were then randomly assigned into six groups (n = 10): TRN, VR or TFA instruments activated by CR or AM. TRN groups 17.02, 20.04 and 26.04; VR groups 15.04, 20.05 and 25.06; TFA groups were shaped consecutively using 15K-file, 20.04 and 25.06. After they were shaped, the canals were scanned again. The volume of removed dentin, canal transportation and centring ratio were calculated μCT images. All data were analysed using the Kruskal-Wallis test or one-way analysis of variance (p < 0.05). With both kinematics, the TRN instrument removed the least amount of dentin, the VR-CR and the TFA-AM removed the most (p < 0.05). The transportation and centring ratios among all groups were similar (p > 0.05). The volume of dentin removed, the diameter or design features of the instruments and different kinematics did not affect the centring ratio and the amount of transportation and remained within safe limits. All three instruments activated by either kinematics were found to have similar effectiveness in shaping curved root canals.

Assessment of the Influence of Fabric Structure on Their Electro-Conductive Properties

Electro-conductive fabrics are key materials for designing and developing wearable smart textiles. The properties of textile materials depend on the production method, the technique which leads to high conductivity, and the structure. The aim of the research work was to determine the factors affecting the electrical conductivity of woven fabrics and elucidate the mechanism of electric current conduction through this complex, aperiodic textile material. The chemical composition of the material surface was identified using scanning electron microscopy energy dispersion X-ray spectroscopy. The van der Pauw method was employed for multidirectional resistance measurements. The coefficient was determined for the assessment of the electrical anisotropy of woven fabrics. X-ray micro-computed tomography was used for 3D woven structure geometry analysis. The anisotropy coefficient enabled the classification of electro-conductive fabrics in terms of isotropic or anisotropic materials. It was found that the increase in weft density results in an increase in sample anisotropy. The rise in thread width can lead to smaller electrical in-plane anisotropy. The threads are unevenly distributed in woven fabric, and their widths are not constant, which is reflected in the anisotropy coefficient values depending on the electrode arrangement. The smaller the fabric area covered by four electrodes, the fewer factors leading to structure aperiodicity.

Assessment of the Penetration of an Endodontic Sealer into Dentinal Tubules with Three Different Compaction Techniques Using Confocal Laser Scanning Microscopy

Adequate root canal sealing is essential for the success of endodontic treatment. There are numerous techniques available; identifying simple and efficient techniques is important to provide good patient care. The purpose of the study was to compare the maximum penetration depth and the percentage of sealant penetration of an endodontic sealer into dentine tubules using cold lateral condensation, continuous wave, and hybrid techniques, and to contrast the effectiveness of two different tapered gutta-percha master cones (0.02 and 0.04). A sample of sixty single root teeth was used. Six experimental groups were formed from the three filling techniques and the two tapered master cones. Images were acquired using a confocal laser scanning microscope. In the apical root third, the penetration percentage was higher in the hybrid compared with the continuous wave technique. The results indicated a higher penetration depth of hybrid compared with cold lateral condensation in the middle and coronal thirds, and in the apical third, a higher penetration was identified in the hybrid group compared with the continuous wave group. No significant differences in penetration were found comparing 0.02 with 0.04 taper gutta-percha groups. The coronal cross-sections presented a higher penetration than the apical third sections. In conclusion, the hybrid technique a had higher maximum sealer penetration than the continuous wave in the apical third, and the coronal third hybrid and continuous wave had a higher penetration than cold lateral condensation.

Method to determine the root canal spatial geometry using an algorithm of the e-Vol DX CBCT software

This study evaluated a method to determine the spatial geometry of root canal preparation (RCP) using navigation dynamics and a specific algorithm from a new CBCT software (e-Vol DX). CBCT scans of 168 root canals of mandibular molars were acquired before and after RCP, using nickel-titanium (NiTi) instruments (ProTaper Next, BioRace, Reciproc Blue, and WaveOne Gold). The spatial geometry of the root canals and the operative risk of disproportional wear of dentinal walls after RCP were evaluated using a new CBCT software. A 3-point scoring system was used after the measuring of cementum/dentin thickness before and after RCP in all root thirds. The root thirds were distributed into three parts of similar sizes, and the scores were categorized at three levels: 1. mild risk (1/3), 2. moderate risk (2/3), 3. severe risk (3/3). These levels were proposed according to the risk of creating disproportionate shapes, thin walls, or perforations. The data were analyzed statistically by Fischer's exact test (α = 5%). There were no significant differences in operative risk among the NiTi engine-driven systems, for the distal or mesial walls of all the root canal thirds (p>0.05). The spatial geometry method to assess operative risk allows clinical planning for a predictable enlargement of the root canal in all root thirds. Based on using a map-reading strategy on root canals in CBCT scans, NiTi engine-driven instruments did not present an increased operative risk during RCPs.

Shaping ability of WaveOne Gold and OneReci by using two apical sizes: a micro-computed tomographic assessment

Backround

OneReci (MicroMega, Besançon, France) is a recently introduced single-file reciprocating system with scarce information revealed on its shaping ability. This study aimed to compare the shaping abilities of OneReci and a well-documented single-file reciprocating system WaveOne Gold (WOG; Dentsply Maillefer, Ballaigues, Switzerland) and evaluate the effect of increased apical enlargement on the preparation quality, using micro-computed tomography (micro-CT).

Methods

After an initial micro-CT scanning, twenty mesial root canals of mandibular molars were anatomically matched. The canals were assigned to two experimental groups (n = 10), using OneReci or WOG in different canals of the same root. The glide paths were created, and root canals were prepared twice, using size 25 and 35 instruments of the systems, respectively. The specimens were scanned with micro-CT after each preparation. The increase in canal volume, amount of dentin removal, unprepared root canal surface, canal transportation, centering ratio and preparation times were assessed. The data were analysed with independent sample t-tests, variance analyses, Friedman and Mann-Whitney U tests. The significance level was set at 5%.

Results

Each preparation increased the canal volume and dentin removal while decreasing the unprepared root surface. The difference between the systems became significant after preparation with size 35 instruments (p < 0.05). Regarding canal transportation and centering ratio, the difference was insignificant (p > 0.05). The first preparation step (glide path + size 25 instrument) was significantly faster in the OneReci group (p < 0.05).

Conclusions

Preparation with size 25 instruments of the systems appeared to be safe with similar shaping performances. Larger apical preparation promoted significantly higher dentin removal, volume increase, and prepared surface area in WOG.

A critical appraisal of research methods and experimental models for studies on root canal preparation

It is the aim of this review to present a critical overview and summary on the contemporary possibilities, limitations and challenges of research related to root canal preparation. Frequently used research tools and contemporary research designs will be presented and discussed critically focussing on shortcomings and benefits with special regard to clinical relevance and scientific evidence. A plethora of experimental set-ups for assessing the shaping of root canals have been described in the endodontic literature using a considerable number of techniques and instruments. Nevertheless, it can be stated that scientific evidence demonstrating the clinical impact of many investigated topics is questionable or even missing. Instead of technical, radiographic and geometrical parameters, further research should focus on biological aspects and clinical evidence of the impact of root canal preparation on the outcome of root canal treatment.

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

Background

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

Methods

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

Results

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

Conclusions

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

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

INTRODUCTION

This research studies and compares the shaping ability of WaveOne Gold (WG; Dentsply Tulsa Dental Specialties, Tulsa, OK), the Reciproc Blue (RB; VDW, Munich, Germany), TRUShape (TS, Dentsply Tulsa Dental Specialties), XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland), iRace (IR, FKG), and TruNatomy (TN; Dentsply Sirona, Ballaigues, Switzerland) in the preparation of moderately curved canals and using micro-computed tomographic technology.

METHODS

Sixty lower molars with 2 mesial canals were randomly distributed into 6 groups of 10 molars and 20 canals per group (n = 20). Specimens were scanned before and after preparation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WG, group 2 with RB, group 3 with TS, group 4 with XP, group 5 with IR, and group 6 with TN. After instrumentation, researchers quantified the changes produced in the canal geometry in terms of surface, volume, structure thickness, surface convexity index, structure model index, percentage of surface touched, and centroids. Wilcoxon and analysis of variance tests were performed to compare the values before and after preparation and the differences between groups. The significance level was established at 5%.

RESULTS

There were no significant differences between WG and RB (P > .05) and between TN and XP (P > .05). TN had significant differences with WG, RB, TS, and IR (P < .05). All the files produced similar apical transportation (P > .05).

CONCLUSIONS

WG and RB and TN and XP had similar shaping effectivity. TS and WG touched the highest percentages of canal surfaces (81% and 73%, respectively) but produced the biggest changes in the canal anatomy. TN and XP better kept the canal anatomy, but TN touched the lowest percentage of canal surface (50%). All the files used were able to clean and to shape moderately curved canals with minimal apical transportation.

Analysis of second mesiobuccal root canal instrumentation in maxillary first molars with three nickel-titanium rotary instruments: a micro-computed tomographic study

The aim of this study was to evaluate the shaping characteristics of Protaper Universal (PTU; Dentsply Tulsa Dental Specialties, Johnson City, TN), Hero Shaper (HS; MicroMega, Besacon, France) and Hyflex CM (HCM; Coltene-Whaledent, Allstetten, Switzerland) nickel-titanium systems with various apical sizes and tapers in second mesiobuccal (MB2) canal instrumentation using micro-computed tomographic imaging. A total of 27 maxillary first molars with independent patent MB2 canals were selected and randomly assigned to three groups according to the 3-dimensional morphologic aspects obtained from preoperative micro-computed tomographic scans. Canals were first negotiated with a size 8 K-file and finally prepared to F1, F2, and F3 with PTU and to sizes 20.04 taper, 25.04 taper, and 30.04 taper with HS and HCM. Postoperative scans were performed after each instrumentation with the same parameters used in the initial scan. The canal volume, canal transportation, untouched canal surface and wall thickness were measured and calculated using Mimics 10.01 software (Image Works, Materialise, Belgium). Statistical analysis was performed using one-way analysis of variance post hoc LSD tests. PTU removed more dentin than HS and HCM in all sections when instrumented to the same apical size (P < 0.05). HS and HCM presented a lower mean value of canal transportation than PTU in all measured sizes and sections. PTU presented a lower mean value of distal wall thickness than HS and HCM at the level of 1 and 2 mm below the furcation region in all measured sizes. In conclusion, for MB2 canal instrumentation, HS and HCM of 0.04 taper are safer than PTU.

The Influence of Brushing Movement on Geometrical Shaping Outcomes: A Micro-CT Study

Brushing motion has been proposed for endodontic single-file reciprocating systems to eliminate coronal interferences, but it may hesitate in a less conservative root canal shaping. The aim of the study was to compare the maintenance of the original root canal anatomy using the WaveOne Gold (WOG) technique with or without a brushing motion. Sixty extracted human mandibular first molars were selected. Manual canal scouting and mechanical glide path were performed. Samples were randomized into two groups (n = 30): WOG Primary was used to shape the mesio-lingual canals without (NB group) or with (B group) an intentional brushing motion. Specimens were scanned with micro-computed tomography (micro-CT) before and after instrumentation in order to match the volumes. Increases in canal volume and surface area were measured. Centroid shift and thickness of removed dentine from the inner curvature were assessed at the furcation, 1.5 mm and 3 mm apically from the furcation, and in relation to the point of maximum curvature. Data were analyzed by one-way ANOVA and post-hoc Student–Newmann–Keuls tests (p < 0.05). No brushing technique resulted in being significantly associated with a better maintenance of the canal anatomy, especially in the coronal third (p < 0.05). When using the WOG system, a no-brushing technique resulted in less invasive shaping, reducing the risk of stripping.