Cleaning and Shaping Oval Canals with 3 Instrumentation Systems: A Correlative Micro–computed Tomographic and Histologic Study

Exploring morphometric transformations in temperature-sensitive NiTi instruments alongside real-time intracanal temperature dynamics

AIM

This study was twofold: (i) it aimed to investigate the morphometric changes of three temperature-sensitive nickel-titanium (NiTi) instruments at different temperatures, and (ii) to conduct an in vivo real-time analysis of intracanal temperature changes.

METHODS

Changes in the shape and length of XP-Endo Shaper, XP-Endo Finisher, and XP-Endo Finisher-R were evaluated in real time whilst heated in a temperature-controlled water bath from 22 to 45°C. Instruments were fixed to a laminated water-resistant 1 mm graph paper attached to a stone block. Instruments were imaged whilst subjected to increasing temperature using a digital camera attached to an operating microscope. From recorded videos, still frames were extracted at 10-s intervals and changes in the length and shape of each instrument were measured and changes were plotted against time. Moreover, the intracanal temperature of distal roots of lower molars was measured in vivo for patients attending the clinic for non-surgical root canal treatments. The temperature was measured using a K-type thermocouple probe inserted into the mid-root level after irrigating the canal with a solution set at room temperature (22°C) or heated to 45°C. The intraoral and intracanal temperatures were recorded using a video camera for 180 s at 5-s intervals to plot the change in the intraoral and intracanal temperature, after both irrigation solution temperatures, with time.

RESULTS

The shape transformation of XP-Endo Shaper began at 31.5 ± 2.0°C and reached its optimal transformation at 35.1 ± 1.0°C. For the Finisher and Finisher-R, shape transformations began at 29.2 ± 1.9 and 26.9 ± 2.2°C reaching the optimal transformation at 33.9 ± 1.4 and 32.7 ± 1.7°C, respectively. The average decreases in lengths of XP-Endo Shaper, Finisher, and Finisher-R after full transformation were 0.43 ± 0.23, 1.07 ± 0.22, and 1.15 ± 0.22 mm, respectively. The intracanal temperature reached 32.9 ± 0.8 and 33.2 ± 1.0°C after 3 min of application of irrigation solutions set at 22 or 45°C, respectively.

CONCLUSION

The tested instruments exhibited diverse changes in their shapes and lengths at varying temperatures. Despite the temperature of the irrigation solution, the intracanal temperature consistently remained lower than the intracanal temperature once equilibrium was reached. This highlights the importance of considering the temperature of irrigation solution during in vitro testing of endodontic instruments.

Debridement ability of the WaveOne Gold and TruNatomy systems in the apical third of root canals: ex vivo assessment

Cleaning and shaping the root canal system are essential steps for performing successful endodontic therapy, and are challenging procedures in the apical region. This study aimed to conduct an ex vivo assessment of the debridement ability of the WaveOne Gold (Medium 35/.06) and TruNatomy (Medium 36/.03) systems in the apical third of round root canals of mandibular premolars. Forty-eight teeth, extracted for orthodontic or periodontal reasons, were divided into three groups (n=16), as follows: Group C, control (without instrumentation or irrigation); Group WOG, instrumentation with WaveOne Gold; Group TN, instrumentation with TruNatomy. A total of 40 mL of 2.5% sodium hypochlorite and 5 mL of 17% ethylenediamine tetraacetic acid were used per root canal in all the groups. Ten 0.5-μm serial cross-sections per specimen were obtained every 0.2 mm from a 2-mm segment of the apical region, extending from 1 to 3 mm short of the root apex. The sections were stained with hematoxylin-eosin and analyzed under a digital microscope (100x). The percentages of unprepared walls and remaining debris were quantified using ImageJ software. Generalized linear models were used to analyze the results (α=5%). Groups WOG and TN had significantly lower percentages of unprepared walls and remaining debris than Group C (p<0.05). There was no significant difference between groups WOG and TN for either of the variables studied (p>0.05). Instrumentation with the WaveOne Gold Medium and TruNatomy Medium instruments was associated with equivalent percentages of unprepared walls and remaining debris in the apical third of round canals of mandibular premolars.

The effect of root canal preparation tapers on planktonic bacteria and biofilm reduction in the apical third: A correlative microtomography and microbiological laboratory study

AIM

To evaluate the influence of different preparation tapers on the reduction in planktonic bacteria and biofilms of Enterococcus faecalis and Candida albicans in the apical third (4 mm) of the mesial roots of mandibular molars, correlating decontamination with canal shape.

METHODOLOGY

After microtomography analysis for morphological standardization of the canals, 48 mandibular molar roots, each containing two canals (96 canals), were contaminated with E. faecalis and C. albicans and divided into four groups (n = 11) for canal instrumentation using ProDesign Logic 2 files with different tapers G (.03): # 25.03; G (.04): # 25.04; G (.05): # 25.05; and G (.06): # 25.06 and irrigation with 2.5% sodium hypochlorite. Four roots were examined under a scanning electron microscope (SEM) to qualitatively assess biofilm formation. Eight roots were used as the negative control group (samples were not contaminated). Bacteriological samples were taken exclusively from the apical third of the roots before and after chemical-mechanical preparation and bacterial counts were determined (CFU/mL). The final micro-CT scan was used to quantify the volume variation and unprepared canal area in the apical third. Statistical analysis was performed using the Kruskal-Wallis, Student-Newman-Keuls and Wilcoxon tests for analysis of microbiological data. anova and the Tukey or Games-Howell test were used for analysis of micro-CT data and Spearman's test for correlations (α = 5%).

RESULTS

All groups showed a significant reduction in bacteria (p < .05), with no statistically significant difference between groups. There was no significant difference in per cent volume increase between groups. The unprepared area (Δ%) was affected by the file used (p = .026) and was significantly lower for G (.06) compared to G (.03). There was no statistically significant correlation among bacterial reduction, volume and unprepared area (p > .05).

CONCLUSION

The different preparation tapers influenced root canal shaping in the apical third but did not improve decontamination in this region.

Shaping Ability of TRUShape and XP-endo Shaper in C-Shaped Canals Using 3D-Printed Replicas: A Micro-CT Study

OBJECTIVE

 This study compared the shaping ability of TRUShape and XP-endo Shaper systems on C-shaped root canals replicas using microcomputed tomography (micro-CT).

MATERIAL AND METHODS

 Thirty three-dimensional replicas based on a mandibular second molar classified as C1 type I C-shaped canal were randomly divided into two groups (n = 15): TRUShape (G.TRU) and XP-endo Shaper (G.XP) and instrumented with each system according to the manufacturer's instructions. Changes in volume and surface and the unprepared area of the root canal were measured by scanning on micro-CT before and after instrumentation.

RESULTS

 The unprepared areas were 39% in the G.TRU and 43% in the G.XP group with no significant difference between them (p > 0.05), but both the tested systems left a high percentage of unprepared root canal walls of C-shaped root canals.

CONCLUSION

 TRUShape and XP-endo Shaper showed a high rate of unprepared areas with similar results after C-shaped root canals replicas for root canal preparation.

Assessment of Smear Layer Removal and Penetration Depth of Root Canal Irrigant Using Different Irrigation Activation Systems: A Comparative Study

AIM

The aim of the current study was to evaluate the penetration depth and smear layer removal of root canal irrigant using various irrigation activation techniques.

MATERIALS AND METHODS

In this investigation, sixty single-rooted premolars extracted for orthodontic purposes were chosen. Diamond burs were used to create an access cavity, and #10 K-file was used to determine the patency. About sixty samples were divided into the following three groups (20 samples in each group), group I: Irrigation with conventional needle, group II: Activation of EndoVac system, group III: Passive ultrasonic irrigation (PUI). The efficacy of the smear layer was assessed using a scanning electron microscopy at a ×2000 magnification. One-way ANOVA was used to record and analyze the data. All statistical analyses were performed with a significance level of p < 0.05.

RESULTS

At coronal third, the maximum smear layer was removed in group II (1.26 ± 0.02) followed by group III (1.84 ± 0.16) and group I (2.89 ± 0.21). At middle third, smear layer removal was maximum in group I (1.18 ± 0.10) followed by group III (1.72 ± 0.09) and group I (2.66 ± 0.18). At apical third, the more smear layer was removed in group II (1.02 ± 0.01) followed by group III (1.58 ± 0.08) and group I (2.38 ± 0.06). There was a highly significant difference found between the three different irrigation systems at all three levels (p < 0.001).

CONCLUSION

In conclusion, every irrigation device that was evaluated was successful in removing the smear layer from the root canal. However, the EndoVac system group removed a greater amount of smear layer compared with PUI and conventional needle group.

CLINICAL SIGNIFICANCE

With the goal of promoting cleaning that is beyond the ability of mechanical devices, irrigation is a crucial part of root canal therapy. If an efficient irrigation delivery system is used, the irrigants can reach the working length (WL). This type of distribution system needs to provide a suitable amount of irrigants up to the WL, as well as have enough flow and be effective at debriding the entire canal system. How to cite this article: Pujari MD, Das M, Das A, et al. Assessment of Smear Layer Removal and Penetration Depth of Root Canal Irrigant Using Different Irrigation Activation Systems: A Comparative Study. J Contemp Dent Pract 2024;25(4):331-334.

Effect of different sealer activation techniques on dentinal tubule penetration

The aim of this study was to evaluate the influence of different activation techniques on dentin tubule penetration of root canal sealer. Seventy-five teeth with single canals were chemomechanically prepared. A calcium silicate-based sealer was stained with a fluorescent dye (rhodamine B), placed into the canals and activated according to the following groups: control (no activation), EDDY, EndoActivator, ultrasonic and XP-Endo Finisher. Then, the samples were obturated. The percentages of sealer penetration at various depth levels of root sections were measured with confocal laser scanning microscopy. XP-Endo Finisher presented the highest penetration at 50 μm (p < 0.05). XP-Endo Finisher showed similar penetration with EDDY at 100 and 200 μm (p > 0.05) while presented higher penetration than the other groups (p < 0.05). At 500 μm, XP-Endo Finisher presented higher penetration than EndoActivator (p < 0.05) while similar penetration with the other groups (p > 0.05). XP-Endo Finisher can be recommended for activation during sealer placement for better penetration into dentin tubules.

Diamond-coated ultrasonic tip decreases debris and uninstrumented surface after preparation of curved canals with isthmus

The aim of this study was to evaluate root canal preparation with nickel titanium rotary instruments and complementary preparation with ultrasonic tip in curved canals of mandibular molars with isthmus. Twenty-eight mesial roots of mandibular molars with curvature between 20° and 40° and presence of isthmus throughout the entire extension of the root canals were prepared using ProDesign Logic CM (PDL) up to size 40.05, or HyFlex EDM (HFEDM) up to size 40.04. Complementary preparation was performed in the isthmus region using the ultrasonic insert E18D (Helse, Istmo Diamantada). The root canals were scanned using micro-CT (SkyScan 1176) at 9 µm voxel size before and after each preparation step. Transportation, percentage of increase in volume, debris and uninstrumented surface (UNS) were evaluated. Mann Whitney, Wilcoxon, paired and non-paired t-tests were used for statistical analysis (α = 0.05). The canals prepared with PDL and HFEDM obtained similar results for all the variables assessed before using E18D (p > 0.05). E18D significantly decreased the percentage of debris and UNS values in both Groups (p < 0.05). The complementary preparations with E18D caused a smaller quantity of debris in the isthmus of the canals previously prepared with PDL in comparison with HFEDM (p < 0.05). PDL and HFEDM provided similar root canal preparation. PDL promoted a smaller quantity of Debris in the isthmus than HFEDM after using E18D. E18D significantly improved cleaning, and reduced Debris and UNS.

Accumulated Hard Tissue Debris and Root Canal Shaping Profiles Following Instrumentation with Gentlefile, One Curve, and Reciproc Blue

INTRODUCTION

This laboratory study aimed to evaluate the accumulated hard tissue debris (AHTD) and shaping performance following root canal instrumentation with a novel stainless steel rotary system (Gentlefile; MedicNRG, Kibbutz Afikim, Israel) compared with two single-file nickel-titanium instruments of different kinematics through micro-computed tomography (micro-CT) analysis.

METHODS

Thirty isthmus-containing mesial roots of human mandibular molars with a curvature of 15°-35° were scanned with micro-CT at an isotropic resolution of 12 μm and randomly assigned to three groups (n = 10) according to the instruments used for canal preparation: Gentlefile (GF; #23/.04), One Curve (OC; #25/.06; Micro-Mega, Besancon, France), and Reciproc Blue R25 (RB; #25/.08; VDW, Munich, Germany). The AHTD, unprepared canal surface area, volume changes, surface area changes, and transportation were evaluated by comparing preoperative and postoperative micro-CT images. In addition, the time required for canal preparation was recorded. Data were statistically analyzed using the one-way analysis of variance (ANOVA) test or the Kruskal-Wallis test at a significance level of 5%.

RESULTS

No significant differences were observed in the percentage of AHTD or in the unprepared canal surface area between the three groups (P > .05). The RB group demonstrated a significantly greater percentage increase in volume and surface area than the GF group (P < .05). The GF and OC groups showed significantly less transportation at 3 mm from the apex than the RB group (P < .001). The OC group required significantly less time for instrumentation than the RB and GF groups (P < .05).

CONCLUSIONS

Instrumentation with GF (#23/.04), OC, and RB yielded similar levels of AHTD and unprepared surface area in isthmus-containing curved canals. GF achieved this with less dentin removal and apical transportation, at the expense of a longer preparation time.

Efficacy of Different Irrigant Activation Systems on Debris and Smear Layer Removal: A Scanning Electron Microscopy Evaluation

Background

Irrigation is an essential component of root canal treatment to enable cleaning beyond the reach of mechanical instruments. The study aimed to assess and compare the efficacy of different final irrigation protocols, including sonic- and ultrasonic-powered irrigant-activation systems, on debris and smear layer removal in the coronal, middle, and apical thirds of straight oval root canals.

Materials and Methods

Straight oval root canals of 60 human mandibular incisors were prepared to size 40.04 and divided into four groups (n = 15) according to the final irrigation protocols: (a) Eddy sonic activation (b) endosonic passive ultrasonic irrigation (PUI), (c) irrisafe PUI, and (d) manual syringe and needle irrigation with no additional activation, which served as control. After the treatment procedures, the roots were split and observed using scanning electron microscopy. The presence of remaining debris and smear layer at the coronal, mid-root, and apical thirds of the canals were evaluated using a score system and statistically analyzed using multinominal models with significance level set at p < 0.05.

Results

None of the final irrigation protocols completely removed all debris and smear layer from all root canals. When the syringe and needle were used without activation, more debris and smear layer were found in the apical third of the canals. Activation of the final irrigant with each of the three devices significantly reduced the presence of debris in the apical third, compared to the syringe and needle final irrigation, with no difference among the three activation devices. Eddy and irrisafe activation also significantly reduced the residual smear layer in the apical third, compared to syringe and needle alone, while the reduction in the remaining smear layer by endosonic activation did not reach the significance level.

Conclusions

Removal of debris and smear layer from the apical part of the root canal by syringe and needle irrigation alone may be significantly improved by using sonic or ultrasonic activation of the final irrigant. Endosonic activation was less effective in removal of smear layer from the apical part of the canals compared to the other two activation systems.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Comparative evaluation of different instrument kinematics on contact percentage, dentin removal and apical debris extrusion in oval canals

The aim of this study was to compare four different instrument kinematics in oval canals. Distal root of sixty extracted first mandibular molars with single oval canal were allocated randomly to four groups (n = 15) namely protaper universal [PTU] (Rotary), self-adjusting file [SAF] (Adaptive), TruShape [TS] (Rotary) and WaveOne [WO] (Reciprocating). The percentage of untouched and touched surfaces of the root canal was evaluated using micro-computed tomography (MCT). Pre- and post-instrumentation weight was assessed using digital microbalance for determining the amount of dentin removed and apical extrusion of debris. The results were tabulated, and their mean difference was statistically analysed using one-way ANOVA and Tukey's HSD test. PTU and SAF exhibited significantly less mean percentage of untouched surface compared to TS. TS files removed less dentin and extruded less debris in long oval canals.

The efficacy of a novel SWEEPS laser-activated irrigation compared to ultrasonic activation in the removal of pulp tissue from an isthmus area in the apical third of the root canal

This study aimed to evaluate the efficacy of Shock Wave Enhanced Emission Photoacoustic Streaming (SWEEPS) in the removal of remaining pulp tissue from the root canal isthmus area in lower molars and compare it with ultrasonically activated irrigation (UAI) and conventional needle irrigation (NI). Forty-one lower molars with isthmuses between mesial canals were included in the study. The teeth were randomly distributed into experimental groups (n = 12/each) based on the final irrigation protocol (SWEEPS, UAI, or NI) and a control group (C) (n = 5). The traditional access cavity of the mesial part of each tooth was made in all samples. The mesial root canals in the experimental groups were instrumented with a Wave One Gold Primary (25/.07) file using 3% sodium hypochlorite (NaOCl) while the distal canal served as a control for the presence of pulp tissue. No treatment was performed in the C group. Sections from the isthmus region were processed for histopathology to measure the remaining pulp tissue (RPT). The results were analyzed using analysis of variance and the Kruskal-Wallis test (α = 0.05). There were no significant differences in the relative surface area of root canals and isthmus among the groups (p > 0.05). Samples in the SWEEPS group had significantly less RPT than UAI, NI, and C (p = 0.003, 0.014, 0.003, respectively). There were no significant differences between the UAI and NI (p = 0.583). SWEEPS was the most efficient in debridement of the root canal isthmus area. UAI and NI showed similar but lower efficiency.

XP-endo Finisher effectively reduces hard-tissue debris accumulated in root canals with isthmus after preparation with a reciprocating file system

This study compared the accumulated hard-tissue debris (AHTD) after preparation with WaveOne Gold (WOG) to XP-endo Shaper (XPS), without and with a supplementary step using XP-endo Finisher (XPF) using clinically applicable irrigation. Twenty-four mesial roots with two canals and single foramen were micro-CT-scanned and matched. Scans were also taken after preparation with WOG or XPS, and after XPF. Irrigation with 2.5% NaOCl (total: 17 ml per canal) and 17% EDTA (2.5 ml per canal) was performed using a 30ga Max-I-Probe needle placed up to the working length. Morphological parameters were calculated and compared within and among groups. XPF significantly reduced unprepared area within XPS and WOG groups, and AHTD within WOG (p < 0.05). There were no significant differences between WOG and XPS after preparation and after XPF (p > 0.05). In conclusion, WOG and XPS produced a similar volume of AHTD, but the supplementary step with XPF decreased the AHTD in the WOG group.

Microtomographic Assessment of the Shaping Ability of the Hyflex CM and XP-endo Shaper Systems in Curved Root Canals

OBJECTIVE

 This study compared the shaping ability of the Hyflex CM and XP-endo Shaper rotary file systems in curved mesial canals of mandibular molars using micro-computed tomography.

MATERIAL AND METHODS

 Seventeen mesial roots of extracted first mandibular molars with two independent mesial canals were scanned before and after root canal preparation with the tested rotatory file systems. Each mesial canal from the same specimen was prepared with one of the two systems. The parameters analyzed were canal centering (transportation) for the cervical, middle, and apical segments, as well as for the entire canal (0-10 mm from the apex); and canal volume increase, canal surface area increase, and unprepared canal walls for two segments, 0 to 4 mm and 0 to 10 mm from the apex.

RESULTS

 There was no significant difference between both systems regarding canal centering (transportation), volume increase, and unprepared canal walls for the 0 to 10 mm segment (p> 0.05); however, a significant difference was observed for the 0 to 4 mm segment (p <0.01), where the Hyflex CM left 28.46% of unprepared walls and XP-endo Shaper left 13.26%.

CONCLUSIONS

 The shaping ability of the two tested rotatory file systems in mesial roots of first mandibular molars was similar for all parameters in all the segments evaluated, except for the 0 to 4 mm segment, where XP-endo Shaper left a smaller area of unprepared canal walls than Hyflex CM.

Anatomical complexities affecting root canal preparation: a narrative review

A fundamental aspect of the Endodontic field is the knowledge of root canal anatomy. Using a variety of techniques, the internal and external anatomy of teeth have been extensively investigated throughout the past century. Recent improvements in three-dimensional computed tomography have enabled more detailed evaluations of root canal morphology in both clinical and laboratory settings. Essentially, researches have unveiled that the root canal constitutes a complex system, comprising not only the main root canal but also lateral components, including isthmuses, fins, accessory canals and apical ramifications. Undoubtedly, this intricate morphology poses a significant challenge when it comes to the process of shaping, cleaning and disinfecting the root canal system. This article aims to explore the anatomical aspects of the root canal system that impact the chemomechanical procedures.

Cleaning and Disinfecting Oval-Shaped Root Canals: Ex Vivo Evaluation of Three Rotary Instrumentation Systems with Passive Ultrasonic Irrigation

Background and Objectives: Successful root canal treatment depends on the thorough removal of biofilms through chemomechanical preparation. This study aimed to investigate and compare the cleaning and disinfecting efficiency of oval-shaped root canals using XP-endo Shaper (XPS), ProTaper Next (PTN), and HyFlex CM (HCM) in combination with passive ultrasonic irrigation (PUI). Materials and Methods: Ninety extracted teeth were contaminated and randomly divided into three groups: XPS, PTN, and HCM. Each group was assigned to three subgroups: subgroup A (sterile saline), subgroup B (3% sodium hypochlorite and 17% ethylenediaminetetraacetic acid), and subgroup C (3% sodium hypochlorite, 17% ethylenediaminetetraacetic acid, and PUI). Bacterial sampling was conducted both from baseline samples and samples after chemomechanical preparation. Scanning electron microscopy (SEM) was used to evaluate the residue bacterial biofilms, hard tissue debris, and smear layers on the buccolingual walls of oval-shaped root canals. Results: When combined with sterile saline, XPS demonstrated a higher reduction of bacterial counts and was more effective in eradicating Enterococcus faecalis in the middle third of the canals compared to the other instruments (p < 0.05). Additionally, when used with antimicrobial irrigants, XPS was more effective in disinfecting the coronal third of the canals than the other instruments (p < 0.05). Furthermore, XPS reduced hard tissue debris more effectively in the middle third of canals than in the apical third (p < 0.05). Conclusions: XPS outperforms PTN and HCM in disinfecting oval-shaped root canals. Despite the fact that combining XPS and PUI improves cleaning and disinfecting, removing hard tissue debris from the critical apical area remains challenging.

Influence of brushing motions on the shaping of oval canals by rotary and reciprocating instruments

OBJECTIVE

The effects of brushing on shaping with three different instruments were assessed in oval canals.

DESIGN

Mandibular incisors were assigned to 6 groups (n = 12/group) according to the system, each one with or without brushing: Reciproc Blue, VDW.Rotate, and Race EVO. Micro-computed tomography was performed before and after preparation.

RESULTS

Brushing strokes caused no increase in canal volume, surface area, and structure model index independently of the system (p > 0.05), except for RaCe EVO in the full canal surface area (p < 0.05). Brushing did not increase the prepared areas (p > 0.05), except for Reciproc in the apical canal (p < 0.05). Reciproc with no brushing exhibited less pericervical dentin than with brushing (p < 0.05), while RaCe EVO with brushing resulted in less remaining dentin (p < 0.05).

CONCLUSIONS

The brushing motion had no effects on the overall shaping performance of the 3 instruments tested. An exception was the increase in prepared surface area in the apical canal segment when the Reciproc instrument was used with brushing strokes.

Biofilm elimination from infected root canals using four different single files

INTRODUCTION

Enterococcus faecalis (E. faecalis) is the most commonly isolated bacterium from infected root canals. It is found in the form of a biofilm, which makes it more resistant to antimicrobials, and requires optimal chemomechanical strategies to maximize root canal disinfection.

AIM

To evaluate the efficacy of 4 different endodontic file systems against E. faecalis biofilm growth in root canals using colony-forming units per milliliter (CFU/mL) and scanning electron microscope (SEM).

METHODS

Eighty-five extracted human mandibular premolars with straight root canals and apical diameters not larger than the #15 K-file were randomly selected. After performing a pilot study (n = 15) to determine the ideal incubation period for E. faecalis biofilm development, sixty-five root canals were infected with E. faecalis, incubated for 3 weeks, and then mechanically prepared using one of four single files (XP-endo Shaper, Hyflex EDM, One Curve, and Fanta. AFTM F One) (n = 15). Five infected root canals were excluded for the positive control. Five non-contaminated root canals were included for the negative control. Samples were collected using sterile paper points pre- and post-instrumentation to determine the bacterial load (CFU/mL). Root canals from each group were topographically evaluated at the coronal, middle, and apical segments using scanning electron microscope (SEM). Bacterial reduction data were estimated and statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests (post hoc test) (P ≤ .05).

RESULTS

XP-endo Shaper, Hyflex DEM, and One Curve significantly could eradicate E. faecalis biofilms in infected root canals with no significant difference among them compared to Fanta. AF™ F One.

CONCLUSION

None of the systems were capable of completely eliminating biofilms. XP-endo Shaper, Hyflex EDM, and One Curve mechanically eliminated E. faecalis biofilms compared to Fanta. AF™ F One from infected root canals.

Shaping ability of non-adaptive and adaptive core nickel-titanium single-file systems with supplementary file in ribbon-shaped canals analysed by micro-computed tomography

This study compared shaping ability between two single-file systems and before/after using supplementary file in untouched area, volume of removed dentin, maximum cut depth (the highest cut depth by main file) and remaining thinnest dentin (the thinnest root dentin after preparation). Ribbon-shaped distal canals of mandibular molars were prepared with non-adaptive core (WaveOne Gold) or adaptive core (XP-endo Shaper) files (n = 15/group) and additionally prepared with a supplementary file (XP-endo Finisher), and the shaping ability was investigated using micro-computed tomography. XP-endo Shaper group demonstrated significantly less overall untouched area than WaveOne Gold group (38.21 ± 6.98% vs. 47.68 ± 9.16%) (p < 0.05). No significant difference was detected between XP-endo Shaper and WaveOne Gold groups in volume of removed dentin (1.85 ± 0.53 vs. 1.66 ± 0.33 mm³ ), maximum cut depth (0.10-0.28 vs. 0.10-0.29 mm) and remaining thinnest dentin (0.66-0.80 vs. 0.78-0.88 mm). Supplementary XP-endo Finisher treatment significantly decreased untouched area (11%-23% reduction) (p < 0.05) with minimally cut root dentin (0.01-0.02 mm).

Root Canal Cleaning after Different Irrigation Techniques: An Ex Vivo Analysis

Background and Objectives: The endodontic space is a complex area on both micro and macro levels; therefore, traditional irrigation techniques may not guarantee a complete cleaning of such a complicated tridimensional system. The presented ex vivo study aimed to evaluate root canal cleanliness, obtained through an equal volume of traditionally applied sodium hypochlorite (NaOCl), compared to ultrasonically activated NaOCl and ultrasonically activated NaOCl that had undergone intracanal heating NaOCl. Materials and Methods: A total of 60 freshly extracted human mandibular premolars underwent root sample length standardization (18 mm), root canal preparation and, based on the irrigation method employed, were randomly and equally assigned to three study groups, composed of root samples treated with ultrasonically activated NaOCl, ultrasonically activated NaOCl that had undergone intracanal heating and traditionally applied NaOCl. The root specimens were subsequently fixated with 4% buffered formalin solution and decalcified in Morse liquid. A total often 6-micron-thick serial cross-sections were obtained, dyed using hematoxylin and eosin and examined through an optical microscope at 40×, 100×, and 200×. Results: Ultrasonically activated NaOCl that had undergone intracanal heating showed a significantly smaller amount of debris compared to ultrasonically activated and traditionally applied NaOCl groups (p value < 0.05). Conclusions: Root canal cleanliness saw significant enhancements by ultrasonically activated NaOCl that had undergone intracanal heating.

Influence of apical preparation size and final irrigation protocol on the debridement of oval root canals

This study assessed the influence of apical preparation size and final irrigation protocol on the debridement of the apical third of oval root canals of mandibular molars. Seventy-seven distal roots were divided into 7 groups (n = 11): Control: without instrumentation or irrigation; Group 30CI: ProTaper Next (up to size 30; PTN) + conventional irrigation (CI); Group 30UAI: PTN + ultrasonically activated irrigation (UAI); Group 30XPF: PTN + XP-endo Finisher (XPF); Group 40CI: PTN + ProDesign Logic (up to size 40; PDL) + CI; Group 40UAI: PTN + PDL + UAI; and Group 40XPF: PTN + PDL + XPF. The total volume of irrigating solutions used per root canal in all the experimental groups was 33 mL of 2.5% sodium hypochlorite (NaOCl) and 6 mL of 17% ethylenediaminetetraacetic acid (EDTA). After specimen processing and histological analysis under a digital microscope (100x), the percentages of untouched canal walls (UCW) and remaining debris (RD) were assessed using Image J software. A descriptive and exploratory analysis was conducted, indicating that the data failed to meet the assumptions of an analysis of variance. Therefore, generalized linear models were used to assess the effects of the different instrumentation and irrigation protocols, as well as the interaction among them, on the percentage of UCW and RD. No significant difference was found among the irrigation protocols regarding the percentage of UCW, irrespective of apical preparation size (p>0.05). However, UCW and RD were significantly lower in groups 40CI, 40UAI and 40XPF than in groups 30CI, 30UAI and 30XPF (p<0.05). The percentage of RD was significantly lower in the UAI and XPF groups than in the CI groups, irrespective of apical preparation size (p<0.05). The difference between preparation sizes 30 and 40, with respect to RD, was higher when CI was used (p<0.05). In conclusion, instrumentation up to apical preparation size 40 resulted in lower percentages of UCW and RD than up to apical preparation size 30. Use of UAI or XPF resulted in lower percentages of RD than CI.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

A single-file endodontic treatment: A promising endodontic concept

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Characterisation of deformed or separated nickel-titanium retreatment instruments after clinical use - A multicentre experience: Defect profiles of clinically-used retreatment instruments

OBJECTIVES

The present study examined the defect characteristics of clinically-used, discarded nickel titanium rotary retreatment instruments and analysed the impact of clinical use on their metallurgical properties.

METHODS

92 XP-endo Shaper (XPS; FKG Dentaire) and 20 XP-endo Finisher (XPFR; FKG Dentaire) instruments with structural deformation or separation were collected after retreatment from four endodontic clinics over a 20-month period. The types of defects and their relative locations were recorded. The lateral and fractured surfaces of the separated instruments were examined with scanning electron microscopy. Differential scanning calorimetry was used to investigate the thermal behaviour of new, deformed and fractured instruments.

RESULTS

77 (84%) XPS and 4 (20%) XPFR had an area with structural change while 15 (16%) XPS and 16 (80%) XPFR were fractured. All unfractured, deformed XPFR showed unwinding close to the coronal end of the flute. Fractures in XPS and XPFR were often close to the coronal end of the flutes or the expanding segments of the insruments. Most of the XPS fractures were torsional failure (67%) while XPFR failed predominantly by cyclic fatigue (81%). The austenite-finishing temperature of XPFR (40°C) was higher than that of XPS (35°C). Both XPS and XPFR exhibited 2-stage phase transformations.

CONCLUSIONS

Torsional failure was more prevalent in XPS instruments and fatigue failure was more prevalent in XPFR instruments. Among the investigated instruments, XPFR were more likely to separate without warning whereas XPS frequently exhibited plastic deformation. The latter may be used as a pre-separation forewarning sign during clinical retreatment.

CLINICAL SIGNIFICANCE

The failure mode of XP-endo Shaper and XP-endo Finisher used clinically for retreatment appeared to be different. Plastic deformation, the forewarning sign of instrument seaparation, occurs when XP-endo instruments are used for retreatment.

Combination of a new ultrasonic tip with rotary systems for the preparation of flattened root canals

Objectives

This study evaluated 2 nickel-titanium rotary systems and a complementary protocol with an ultrasonic tip and a small-diameter instrument in flattened root canals.

Materials and Methods

Thirty-two human maxillary second premolars with flattened canals (buccolingual diameter ≥4 times larger than the mesiodistal diameter) at 9 mm from the radiographic apex were selected. The root canals were prepared by ProDesign Logic (PDL) 30/0.01 and 30/0.05 or Hyflex EDM (HEDM) 10/0.05 and 25/0.08 (n = 16), followed by application of the Flatsonic ultrasonic tip in the cervical and middle thirds and a PDL 25/0.03 file in the apical third (FPDL). The teeth were scanned using micro-computed tomography before and after the procedures. The percentage of volume increase, debris, and uninstrumented surface area were analyzed using the Kruskal-Wallis, Dunn, Wilcoxon, analysis of variance/Tukey, and paired and unpaired t-tests (α = 0.05).

Results

No significant difference was found in the volume increase and uninstrumented surface area between PDL and HEDM (p > 0.05). PDL had a higher percentage of debris than HEDM in the middle and apical thirds (p < 0.05). The FPDL protocol resulted in less debris and uninstrumented surface area for PDL and HEDM (p < 0.05). This protocol, with HEDM, reduced debris in the middle and apical thirds and uninstrumented surface area in the apical third (p < 0.05).

Conclusions

High percentages of debris and uninstrumented surface area were observed after preparation of flattened root canals. The HEDM, Flatsonic tip, and 25/0.03 instrument protocol enhanced cleaning in flattened root canals.

Different biomechanical preparation protocols on the penetration and bond strength of the filling material to dentin

The aim of this study was to evaluate the influence of different instruments and mechanisms of agitation of the irrigating solution on the penetration by confocal laser scanning microscopy (CLSM), and the bond strength (BS) of the filling material to the dentin by push-out test. Human premolars were distributed in two experimental groups (n=30), according to the instrumentation system: ProTaper Next (PN) or XP-endo Shaper (XS) and three irrigation protocol (n=10): NaviTip (Nv), XP-endo Finisher (XF), passive ultrasonic irrigation/ XP-endo Finisher (PUIXF). The 2.5% NaOCl and 17% EDTA were the irrigating solutions used. The filling was performed using a lateral condensation technique, with AH Plus added to 0.1% rodhamine B. The roots were sectioned, obtaining 2 slices for each third of the root. The first slice was submitted to the sealer penetration analysis and the push-out test. The second slice was submitted to qualitative analysis (SEM) of the union interface. For the penetration (%) Tukey showed that PNXF (82.38±13.48), PNPUIXF (82.48± 12.02), XSXF (82.24±11.28) and XSPUIXP (86.23±10.45) presented the highest values, different (p<0.05) from PNNv (68.29±15.12) and XSNv (71.41±16.50). The BS (MPa) test evidenced that in the cervical third, PNPF (4.92±1.04) and XPSPF (5.03±0.70) obtained the highest values differing from the others groups (p<0.05). CSLM and SEM showed greater penetration of the sealer on the entire length of the root canal when the irrigation solution was stirred. In conclusion that the association PUI and XP-endo Finisher favored the penetration and bond strength of the filling material to the root dentin.

Planned Apical Preparation Using Cone-Beam Computed Tomographic Measures: A Micro-Computed Tomographic Proof of Concept in Human Cadavers

INTRODUCTION

This study assessed the amount of unprepared surface areas at the apical 4-mm segment of the root canal after a planned preparation based on cone-beam computed tomography (CBCT) measurements.

METHODS

Eighteen posterior mandible segments were obtained from cadavers and scanned using CBCT and micro-computed tomographic (micro-CT) imaging. CBCT images were used to measure the largest initial canal diameter from 29 root canals of premolars at 1, 2, 3, and 4 mm short of the apical foramen. Each measurement was used to select a master apical instrument with size/taper that was 1 diameter larger to prepare the apical 4 mm of each particular root canal. A post-preparation micro-CT scan was obtained, and the unprepared canal areas were calculated.

RESULTS

A very high amount of surface areas over the apical 4 mm of the root canal was included in the final preparation (mean >90%). The unprepared areas ranged from as low as 3.7% to a maximum of 14.6% (mean and median, 9.2% and 9.1%, respectively).

CONCLUSIONS

The proposed planned apical root canal preparation resulted in optimized root canal shaping with a substantial amount of prepared surface areas. The protocol used also resulted in a conservative canal enlargement using final instruments that were 1 size larger than the initial largest canal diameter.

Influence of pecking frequency at working length on the volume of apically extruded debris: A micro-computed tomography analysis

Background/purpose

There is no consensus to date on how many repetitive pecking motions at working length (WL) should be regarded as optimal during instrumentation. Therefore, this study aimed to evaluate the effect of pecking frequency at WL on the volume of apically extruded debris using three single-file systems in curved, oval-shaped canals.

Materials and methods

Forty-five single-rooted mandibular premolars with curved, oval-shaped canals were prescanned by micro-computed tomography, anatomically paired-matched, and randomly divided among three groups (n = 15 each): Reciproc Blue (RB), WaveOne Gold (WOG) and XP-endo Shaper (XPS). Samples were embedded in agarose gel to collect extruded debris. After preparation to the WL, each sample was rescanned after one, two, four, 10, and 20 pecking motions at WL, respectively. The debris volume was innovatively calculated by a modification of an existing method using micro-computed tomography. The apical preparation size was also measured. Data were compared using a two-way repeated-measures analysis of variance.

Results

All single-file systems extruded debris apically, irrespective of the pecking frequency at WL. The extruded debris volume correlated positively with the minor foramen size (P < 0.05); both increased with pecking frequency for each single-file system (P < 0.05). The minor foramen size corresponded to the instrument tip size when reaching the WL once.

Conclusion

To produce less debris extrusion and obtain a predictable foramen size corresponding to the instrument tip size, a single pecking motion may be preferred when using single-file systems. Caution should be exercised when applying the current results to clinical situations.

Novel laser activated photoacoustic streaming for removing pulp remnants from round root canals after single file reciprocating instrumentation: Photoacoustic streaming for removing pulp

BACKGROUND

This study evaluated the efficacy of a new laser-assisted irrigation system, the shock wave enhanced emission photo-acoustic streaming (SWEEPS) technique in removing pulp tissue from single-rooted premolars.

METHODS

Freshly extracted mandibular premolars with round root canals (n=40), scanned using cone beam computed tomography, were randomly divided into control and four experimental (according to the irrigation technique used) groups (n=8/group). Groups 1, 2, and 3 were instrumented using Reciproc Blue (RB25/.06) followed by final irrigation protocol (FIP), activated by SWEEPS, ultrasonically activated irrigation (UAI), and conventional irrigation (CI), respectively. In these groups, 7 mL 3% NaOCl in total was used during instrumentation; for FIP, 3% NaOCl (60 s), ethylenediaminotetraacetic acid (60s), and 3% NaOCl (30s). In group 4, SWEEPS activation of 3% NaOCl for 6 × 30 s alone was performed. The untreated control group specimens were processed for histological evaluation of remaining pulp tissue (RPT) in each canal third. The results were analyzed using the Mann-Whitney U test (α =0.05).

RESULTS

Significant differences were observed between the control group and the experimental groups (p<0.05). In the middle third, the UIA and SWEEPS showed similar efficacy (p=0.171), superior to CI and SWEEPS without instrumentation (p<0.05). In the apical third, SWEEPS was the most efficient (p=0.002), and UIA and CI showed no difference (p=0.643).

CONCLUSION

SWEEPS was superior to UIA and CI in removing RPT in the apical region of round canals after single instrument root canal preparation; SWEEPS without instrumentation was inefficient in removing pulp tissue.

Deficiencies in Root Canal Fillings Subsequent to Adaptive Instrumentation of Oval Canals

Simple Summary

Employing a chemo-mechanical preparation, one of the primary procedural phases in endodontic therapy is carefully removing debris, pulp tissue, and bacteria from the root canal system. The cross-sectional root canal shapes comprise circular, oval, long oval, flattened, or irregular. The frequency of oval root canals in the apical third of human teeth is around 25 to 50%. Motorised endodontic files leave almost 60% of the oval root canal perimeter unaffected by their instrumentation, thus resulting in faulty obturation that is required to prevent reinfection and to restrict the passage of microorganisms and toxins to and from the periapical tissue.

Abstract

The purpose of this study was to explore the influence of instrumentation and the potential for debris deposition using XP-endo shaper plus (XP-SP) and full-sequence SAF (F-SAF) on the adaption of thermoplastic root canal fillings in oval canals. Following the manufacturer’s instructions, ninety human permanent mandibular incisors with a single oval canal 6 mm from the apex (verified using pre-operative CBCT scanning) were instrumented with XP-SP and F-SAF. Obtura III Max apparatus was used for root canal obturation without the use of a root canal sealer. The roots were then sectioned 6 mm from the apex and examined with a digital stereomicroscope at x25 magnification to assess the root canal fillings. The F-SAF was associated with a significantly higher (p < 0.01) percentage of entire adaptation of the root fillings (76%) compared to the XP-SP (57%). Furthermore, the XP-SP group was also associated with higher (p < 0.01) defective obturation with debris at 17% and with voids at 26%. However, the F-SAF had lower percentages of defective obturations (7% with debris and 17% with voids). The quality of obturation of oval canals instrumented using full-sequence SAF was better.

Influence of conservative endodontic access cavities on instrumentation of oval-shaped straight root canals

AIM

To evaluate the influence of the design of endodontic access cavities on the percentage of unprepared areas of canal walls and flexural fatigue of instruments activated by reciprocating movement in oval-shaped straight root canals of extracted teeth.

METHODOLOGY

Forty-two mandibular incisors with oval canals were scanned by a microcomputed tomography (micro-CT) device for homogeneous selection and distribution of the samples. Then, the teeth were divided into two groups (n = 21) according to the design of access cavity being tested: ultraconservative endodontic access cavity (UltraAC) and traditional access cavity. The canals were accessed with the aid of a surgical microscope, instrumented with the WaveOne Gold Medium system and irrigated with 2.5% NaOCl and 17% EDTA. The unprepared areas of the canal wall were analysed by overlaying images before and after instrumentation and expressed as percentages. micro-CT data were analysed using t-test, Mann-Whitney and Wilcoxon tests. The endodontic instruments used during instrumentation were subjected to static flexural fatigue testing using an artificial stainless steel canal with a 60° angle of curvature and a radius of 5 mm, located 5 mm from the tip of the instrument. The instruments were activated until fracture occurred, and the time in seconds for the fracture was recorded using a digital timer. The number of cycles to fracture was calculated and analysed statistically. For flexural fatigue data, an anova test complemented by a Tukey range test was used. The significance level of 5% was used for all analyses.

RESULTS

There was no significant difference between the groups related to unprepared areas by the instrument during canal preparation (p > .05). The difference in flexural fatigue resistance between the groups was not significant.

CONCLUSION

The use of UltraAC did not interfere with the canal instrumentation of extracted mandibular incisors with straight and oval canals. There was no difference in the flexural fatigue resistance of the instruments in relation to access cavity design.

Scope of Preparation of Oval and Long-Oval Root Canals: A Review of the Literature

Successful endodontic treatment depends on cleaning and disinfecting the root canals, in order to provide conditions for three-dimensional filling, which should prevent root canal reinfection. However, anatomical complexities pose a challenge during endodontic treatment. The present study was a literature review carried out in the following databases: PubMed, SciELO, and MEDLINE, which were searched for articles published from 2017 to 2021. Micro-CT studies published in English, which analysed the capacity for preparation of oval and long-oval root canals, were included. The following keywords were used: “oval-shaped canals,” “long-oval-shaped canals,” “endodontics,” and “micro-CT.” The aim of this study was to carry out a literature review of micro-CT studies on the scope of the capacity for preparation performed in oval and long-oval root canals with rotary and reciprocating instruments.

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

AIM

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

METHODOLOGY

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

RESULTS

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

CONCLUSIONS

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

The prevalence of oval-shaped root canals: A morphometric study using cone-beam computed tomography and image analysis software

This study aimed to evaluate the prevalence of oval-shaped root canals at the apical, medial and coronal cross sections of all tooth groups using CBCT and image analysis software. Based on the diameter values, the long/short diameter ratio was calculated and each root canal was classified regarding its shape. Oval-shaped canals were present in 45% at the apical, 50% at the medial and 56% at the coronal level of all teeth. The mandibular central incisors presented oval canals in 24%, long oval in 28% and flat in 2% at the apical level. Mandibular molars showed a statistically significant difference (P < 0.05) in the distribution of oval-shaped canals between cross-sectional levels. Analysis of CBCT scans with an image analysis software could be a reliable and reproducible method and a valuable tool for objective determination of root canal shape in further research.

Postoperative Pain after Use of the WaveOne Gold and XP-endo Shaper Systems: A Randomized Clinical Trial

INTRODUCTION

The present study aimed to clinically compare the incidence of postoperative pain after endodontic treatment of posterior teeth using the WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland) and XP-endo Shaper (XPES; FKG Dentaire, La Chaux-de-Fonds, Switzerland) systems.

METHODS

In a single-blind randomized clinical trial, 148 vital teeth with an indication for conventional endodontic therapy for prosthetic purposes were treated by 5 specialists following a preestablished protocol. All participants were unaware of the treatment they received. The teeth were randomly divided into 2 groups (n = 74) according to the instrumentation system used (the WOG group and XPES group). The treatments were performed in a single session. The participants were asked to rate the intensity of postoperative pain on a visual analog scale (no pain, mild pain, moderate pain, and severe pain) after 24, 48, and 72 hours and 7 days.

RESULTS

The incidence of postoperative pain was higher in the XPES group after 24, 48, and 72 hours compared with those in the WOG group (P < .05). Two participants in the WOG group experienced severe postoperative pain after 24 hours. None of the participants in either group reported pain after 7 days (P > .05, Mann-Whitney test).

CONCLUSIONS

Postoperative pain is expected after preparation of the root canal system with the WOG and XPES systems tested, but it only persists for a short period. Although more common after the use of the XPES system, the pain was classified as mild at all time points.

Shaping efficiency of XP-endo shaper and Mtwo instruments in long oval root canals: A micro-CT study

This study evaluated the shaping ability of XP-endo Shaper and Mtwo systems in long-oval-shaped canals of extracted human mandibular molars using micro-computed tomography (micro-CT). Images recorded before and after preparation were evaluated for morphometric measures regarding increase in canal volume, dentin removed, surface area, untouched walls and structure model index (SMI). Data were statistically analysed using the Mann-Whitney test with 5% of significance. On both groups, the root canal preparation significantly increased all analysed parameters (P > 0.05). There was no statistical difference between XP-endo Shaper and Mtwo systems in the increase of the canal volume (30.50%-27.82%), in volume of dentin removed (2.77%-2.40%), in the increase of the canal surface area (11.30%-8.86%), in canal untouched surfaces (9.57%-8.51%) and in the SMI (2.59%-2.68%), respectively. XP-endo Shaper and Mtwo systems showed similar shaping efficiency and were not able to completely prepare the walls of long-oval-shaped canals of extracted human mandibular molars.

Apical pressures generated by several canal irrigation methods: A laboratory study in a maxillary central incisor with an open apex

Aim

A laboratory study to determine the apical pressure generated by seven canal irrigation methods in an anterior tooth with an open apex.

Methodology

Canal irrigation was performed on a 3D‐printed central maxillary incisor with an open apex (maximum diameter of 2.1 mm). Ultrasonically activated irrigation (UAI), sonic activation (EDDY), negative pressure irrigation (EndoVac), the self‐adjusting file (SAF) and the XP‐endo Finisher were employed at tooth length (TL), TL—1 mm, TL—2 mm and TL—3 mm. UAI was tested at three intensity levels additionally. Hydrodynamic irrigation with RinsEndo was performed in the pulp chamber, at the canal orifice, the coronal third, the middle of the canal and at TL. Er:YAG laser activation, at four frequency settings, was performed in the pulp chamber and at the orifice of the canal. The pressure of the fluid towards the canal terminus generated by activation was directly transferred to a pressure sensor with a range of 0 to 120 mmHg and a response time of ≤0.5 ms. The critical threshold for apical extrusion of the irrigant was set at 5.73 mmHg (lower limit of the central venous pressure: 5.88 ± 0.15 mmHg). Each experiment was repeated ten times. The tests were followed by descriptive analyses (maximum, mean, standard deviation, 95% confidence interval).

Results

EndoVac, the SAF, the XP‐endo Finisher, and UAI never exceeded the critical threshold at any insertion depth or intensity level. Er:YAG laser activation exceeded the critical threshold exclusively at frequency settings that varied from the manufacturer's recommendation. EDDY at TL and RinsEndo at any insertion depth exceeded the critical threshold in 100% of the measurements. EDDY at TL—1,—2, and—3 mm crossed the critical threshold in 30%, 10%, and 20% of the measurements, respectively.

Conclusions

In a simulated maxillary central incisor with an open apex, irrigation with EndoVac, Er:YAG laser activation, UAI, the SAF, and the XP‐endo Finisher generated apical pressures below the critical threshold of 5.73 mmHg. By contrast, using EDDY and RinsEndo for irrigation produced higher apical pressures that exceeded the critical threshold.

Effect of XP-endo Shaper versus conventional rotary files on postoperative pain and bacterial reduction in oval canals with necrotic pulps: a randomized clinical study

AIM

To assess postoperative pain and bacterial reduction following the use of XP-endo Shaper versus conventional rotary files in preparation of oval canals with necrotic pulps.

METHODOLOGY

This superiority, parallel, randomized, double blinded clinical trial was conducted in the clinic of the Endodontic Department, Faculty of Dentistry, Cairo University, Egypt. Sixty single-canalled mandibular premolars with necrotic pulps were randomly assigned into two equal groups. Canals were instrumented using XP-endo Shaper files in the intervention group and iRaCe rotary files in the control group. Bacterial samples were taken before and after canal instrumentation. Incidence and severity of postoperative pain was assessed using a modified VAS after 6, 12, 24 h and daily for 5 days. A culture method was used to assess the number of bacterial colony forming units. Incidence of analgesic intake as well as flare-ups was recorded. Data were analysed using chi-square, Fisher Exact, Mann-Whitney, Independent t-test, and Spearman's correlation for pain and bacterial counts.

RESULTS

The XP-endo Shaper compared with the iRaCe group was associated with a significantly lower incidence of postoperative pain at 6, 12, and 24 h (P = 0.039, 0.047, and 0.026, respectively), and severity of postoperative pain at 6 h (mean difference: 1.33, 95% CI: 0.307-2.352, P = 0.02), 12 h (mean difference: 1.1, 95% CI: 0.26-1.936, P = 0.007), 24 h (mean difference: 0.94, 95% CI: 0.178-1.701, P = 0.008) and 48 h (mean difference: 0.97, 95% CI: 0.192-1.747, P = 0.038). There was a significant decrease in bacterial count following canal instrumentation in both groups (P < 0.001) with no significant difference between them (mean difference: 0.83 × 10⁵ , 95% CI: 0.336 × 10⁵ -1.996 × 10⁵ , P = 0.56). A weak correlation existed between postoperative pain severity and bacterial counts (P = 0.54). There was no significant difference in analgesic intake between the two groups (P = 0.085). Flare-ups occurred in 3.3% of teeth in the iRaCe group, while no flare-ups occurred in the XP-endo Shaper group.

CONCLUSIONS

XP-endo Shaper was associated with a significantly lower frequency of postoperative pain for up to 24 h, and lower severity of postoperative pain for up to 48 h compared with iRaCe files. Both systems were equally effective in bacterial reduction from oval root canals with necrotic pulps.

Effect of canal preparation with XP-endo Shaper and ProTaper Next on root canal geometry and dentin thickness of mandibular premolars with radicular grooves and two canals: a micro-CT study

OBJECTIVES

This study aimed to evaluate the effects of different shaping protocols on the root canal geometry and remaining dentin thickness of mandibular premolars with radicular grooves (RG) and two canals by means of micro-CT.

MATERIALS AND METHODS

Mandibular premolars with RG and two canals were matched based on their similar morphological dimensions and assigned to 2 experimental groups according to the canal preparation (n=8): XP-endo Shaper (XPS) and ProTaper Next (PTN) systems. Before and after preparation, morphometric measurements of the volume, surface area, structure model index, area, perimeter, roundness, major and minor diameters, as well as untouched canal walls, canal transportation, and dentin wall thickness were evaluated. Data were statistically compared within and between groups using the independent sample t test (α=5%).

RESULTS

XPS revealed less changes in volume, surface area, area, perimeter, and major and minor diameters (P<0.05). There was no significant difference in structure model index (SMI), roundness, and percentage of untouched canal walls between groups (P>0.05). XPS resulted in less apical canal transportation and a higher remaining dentin thickness toward the RG compared to PTN in lingual canals (P<0.05).

CONCLUSIONS

XPS revealed fewer changes in root canal geometry as well as lower transportation and a greater remaining dentin thickness in the lingual canals toward the RG compared to PTN.

CLINICAL RELEVANCE

Internal and external anatomical characteristics of mandibular premolars might have an influence on biomechanical preparation. Considering the risk of perforation, the canal preparation using XPS appears to be more conservative compared to PTN.

Three-dimensional analysis of the root canal preparation with Reciproc Blue®, WaveOne Gold® and XP EndoShaper®: a new method in vivo

Background

The purpose of this study was to evaluate the changes in canal volume after root canal preparation in vivo with 3 different single-file techniques (Reciproc-Blue®, WaveOne-Gold® and XP-EndoShaper®), with a new method using CBCT and 3D reconstruction.

Methods

In this prospective study, thirty human lower premolars from healthy patients were used, in which extraction was indicated for orthodontic reasons. All the teeth used were caries- and restoration-free with complete root development, without signs of periodontal disease or traumatic occlusion, and with only one straight canal (up to 25º curvature). Teeth were randomly divided into three different groups: Reciproc-Blue, WaveOne-Gold and XP-EndoShaper. CBCT scans before root canal preparation were used to create a 3D reconstruction with RHINOCEROS 5.0 software to assess the initial canal volume, and then compared with 3D reconstructions after canal preparation to measure the increase in canal volume. Student’s t test for paired data were used to determine statistically significant differences between the before and after canal volumes. Anova test was used to determine statistically significant differences in the percentage of canal volume increase between the groups and Tukey's post-hoc test were used to paired comparison.

Results

Reciproc-Blue showed the higher increase in canal volume, followed by WaveOne-Gold and XP-EndoShaper (p = 0.003). XP-EndoShaper did not show a statistically significant increase in canal volume after root canal preparation (p = 0.06).

Conclusion

With this model, Reciproc-Blue showed higher increase in root canal volume, followed by WaveOne-Gold, while XP-EndoShaper did not significantly increase root canal volume during preparation.

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.

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.

Supplementing filling material removal with XP-Endo Finisher R or R1-Clearsonic ultrasonic insert during retreatment of oval canals from contralateral teeth

This study compared the efficacy of XP-Endo Finisher R and R1-Clearsonic insert in removing filling material remnants from oval canals. Twelve pairs of contralateral premolars were treated and subsequently retreated with Reciproc 50. A supplementary procedure with XP-Endo Finisher R or R1-Clearsonic was performed. Micro-computed tomography was used to quantify the filling material volume in the full canal and apical segment lengths. Intragroup analyses revealed significant reduction of filling material after both procedures, not only in the full canal but also in the apical segment (P < 0.05). The amount of filling material removed with XP-Endo Finisher R and R1-Clearsonic was 47.9% and 52.2% in the apical segment (P > 0.05), and 82.1% and 64.6% in the full canal (P < 0.05). None of the instruments was effective in completely removing the filling material from the apical canal, but better results were obtained with XP-Endo Finisher R in the total canal length.

Contrast-enhanced micro-CT to assess dental pulp tissue debridement in root canals of extracted teeth: a series of cascading experiments towards method validation

AIM

To validate a new method for the evaluation of pulp tissue debridement in the root canals of extracted teeth using an impregnation protocol involving potassium triiodide, a radiocontrast solution known as Lugol's, combined with micro-computed tomographic (micro-CT) imaging.

METHODOLOGY

The impact of NaOCl on the radiopacity of Lugol's solution was assessed using a two-fold dilution series of Lugol in distilled water and 5.25% NaOCl, which were then pipetted into transparent dishes and radiographed. To verify the influence of Lugol on the proteolytic effect of NaOCl, a dissolution test was performed using fresh bovine meat. Ten slices did not undergo any tissue processing, whilst twenty slices were fixed in formaldehyde for 24 h. After that, 10 of them were immersed in Lugol for another 24 h. Then, all specimens were placed in NaOCl and the time required for a complete tissue dissolution was recorded. For the last experiments (histological validation and micro-CT assessment), 8 extracted mandibular premolars with formerly vital pulps were immersed in buffered formalin, scanned in a micro-CT device, accessed, immersed in Lugol for 7 days and scanned again. Then, the root canals of 5 teeth were prepared and scanned, and the volume of remaining pulp tissue identified and quantified, whilst 3 teeth were histologically processed. The same specimens were subjected to histological assessment, and the images of the histologic sections were registered with the corresponding micro-CT images to verify whether the pulp tissue in the histological sections matched its counterpart in the Lugol-impregnated tissues identified in the micro-CT slices.

RESULTS

There was no discernible effect on radiopacity when NaOCl was mixed with Lugol's solution. Tissue processing did not affect the time required for the complete dissolution of fresh bovine meat. Histological evaluation revealed a correlation between micro-CT and histological images confirming the identification of Lugol-impregnated pulp tissue in micro-CT images.

CONCLUSIONS

The radiocontrast Lugol's solution was unaffected by NaOCl and did not interfere with its soft tissue dissolution capability. The impregnation protocol using Lugol's solution allowed the visualization of pulp tissue on the micro-CT images and the identification of pulp remnants after chemical-mechanical canal procedures.

An In Vitro Evaluation Study of the Geometric Changes of Root Canal Preparation and the Quality of Endodontic Treatment

Introduction

The geometry of root canals differs in different parts, especially in the apical region, and it is affected by different preparation techniques. The aim of this study was to evaluate the geometric changes of root canal preparation by general dentists regardless of the endodontic instrumentation systems and to study the quality of endodontic treatment by evaluating the untouched areas after mechanical preparation and the smear layer removal.

Materials and Methods

100 extracted maxillary canines were collected for the in vitro study from 10 dentists, and the dentists were asked to treat the teeth endodontically. The teeth then were separated and examined under an optical microscope to evaluate the root canal final diameter and the untouched areas. Then, the teeth were examined under a scanned electronic microscope to evaluate the smear layer in coronal, middle, and third parts of the canal. Statistical significance was set as P < 0.05.

Results

The mean diameter of the root canal after instrumentation in the coronal and middle thirds was 2.50 ± 1.12 and 1.75 ± 1.24 mm, respectively, and the untouched area percentage observed in the apical thirds was 71%. For smear layer removal, it was better in the coronal and middle thirds than in the apical (P < 0.05).

Conclusion

The changes in the diameter of the root canal, the percentage of untouched areas after mechanical preparation, and the percentage of smear layer were observed in a higher percent in the apical third than in the coronal and middle thirds, and this raises the question of changing the technique of processing the root canal, especially in the apical third.

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.

Evaluation of Cross-Sectional Root Canal Shape and Presentation of New Classification of Its Changes Using Cone-Beam Computed Tomography Scanning

The root canal system is considering the most important factor in endodontic treatment, due to the complexity of its anatomy and morphology. The aim of this study was to evaluate the cross-sectional root canal shape in three thirds (coronal, middle, apical) in different age groups using cone-beam computed tomography scanning (CBCT) and to present a new classification for root canal shape changes. This cross-sectional study included 300 CBCT scans for patient aged 20–70, and these scans were evaluated to study the morphology of the cross-sectional root canal shape in coronal, middle, and apical thirds among three age groups, namely the young (20–44), middle (45–59), and elderly (60–70). The root canal shape was classified as round, oval, long oval, and ribbon (with or without isthmus). The cross-sectional root canal shape was identified in two groups: canals with an unchanging (constant) shape and canals with changing shape. In turn, in canals with changing shape, the change could be identified in the region of the middle or apical thirds of the canal. The results showed that root canal shape changes in two cases: (1) the presence of one or more canals in the root (with or without isthmus between them), and (2) with age, as it was observed that the cross-sectional shape of the root canal becomes round in the apical third with age. A new classification of the changes of root canal shape in three thirds (coronal, middle, apical) was presented in this study.