Mesial Root Canals Research Articles

Finite element analysis of stress in mandibular molars repaired after fractured instrument removal

BackgroundThis study assessed stress distributions in simulated mandibular molars filled with various materials after the removal of fractured instruments from the apical thirds of the root canals.MethodsFinite element models of the mesial and distal root canals were created, where fractured instruments were assumed to be removed using a staging platform established with a modified Gates-Glidden bur (Woodpecker, Guangxi, P.R. China). Each canal was treated with different materials: Biodentine (Septodont, Saint Maur-des-Fosses, France), mineral trioxide aggregate (MTA), and gutta-percha. In addition to these, four control models were also created. In total, 14 models were generated and subjected to a 300 N force applied at a 45° angle to simulate the stress.ResultsModel 1 (Biodentine) and 2 (Gutta-percha + Biodentine) showed the lowest stresses among mesial root canal models, whereas Model 5 (Gutta-percha) showed the highest. Among distal root canal models, Model 6 (Biodentine) and 7 (Gutta-percha + Biodentine) showed the lowest stresses, while Model 10 (Gutta-percha) showed the highest. In addition, Biodentine (Septodont) and Gutta-percha + Biodentine (Septodont) produced similar stress levels in both mesial and distal roots, while MTA and Gutta-percha + MTA led to increased stresses, especially in the distal root. Among the control models, the highest maximum von Mises stress values were in Model 13 and Model 14, which had a staging platform and were not filled with any root canal filling material, after the broken instrument was removed.ConclusionsBiodentine (Septodont) may be preferable to MTA for filling staging platform cavities post-fractured instrument removal due to lower stress levels. Furthermore, calcium silicate-based materials alone or in combination with Gutta-percha showed similar stress levels, suggesting their potential use for root canal filling. All models demonstrated structural integrity within safe limits.

Do instrument kinematics and the apical preparation limit influence canal disinfection and bacterial extrusion?

This in vitro research assessed the influence of the instrument kinematics (rotary and reciprocating) and the apical preparation limit on the root canal disinfection and apical bacterial extrusion. After 21days of Enterococcus faecalis biofilm formation in 72 mesial root canals of mandibular molars, the root canals were distributed into 2 groups (n = 36) according to the systems used for preparation: ProDesign S and Reciproc. The groups were redistributed according to the limit of apical preparation (n = 11): (a) 1mm up to the apical foramen (TL-1); (b) at the apical foramen (TL = 0); (c) 1mm beyond the apical foramen (TL + 1). After preparation, the remaining biofilm adhered to the dentin walls at the apical third was removed by sonication. The aliquots of bacterial suspension released, and the irrigating solution leaked through the apical foramen during preparation were plated for colony-forming units (CFUs) counting. Data were statistically assessed by the Kruskal-Wallis and Dunn tests (α = 5%). Both systems promoted decontamination of the apical third, regardless the limit of apical preparation (p > 0.05). A larger quantity of bacteria was extruded from the root canals prepared 1mm beyond the apical foramen, regardless the instrumentation kinematics (p < 0.05). The apical third of the root canal was efficiently decontaminated after preparation, regardless the instrumentation kinematics and the apical limit. However, a larger quantity of bacterial extrusion was observed when preparation was performed beyond the anatomical root canal limits.

Comparative Evaluation of Crack Propagation During Root Canal Preparation in Primary Molar with Manual Instrumentation, ProTaper Universal and ProTaper Next Rotary File Systems: An in vitro Study.

Root canal preparation with rotary files causes dentinal cracks in root canals of primary teeth affecting their longevity. Nickel-titanium rotary files have been widely used for root canal preparation in primary teeth. The present study compared occurrence of dentinal microcracks in root canals of extracted primary molar teeth prepared using Hedstrom (H) files, ProTaper Universal rotary files, and ProTaper Next rotary file systems. In this in vitro experimental study, 80 primary molar mesial root canals were randomly divided into four groups of 20 canals each (n=20). Group I was prepared with H files. Group II was prepared with ProTaper Universal rotary files using shaping files SX and S2. Group III was instrumented with ProTaper Next rotary files X1 and X2 while Group IV was left unprepared and served as control. Roots were stained with 1% methylene blue solution and sectioned perpendicular to the long axis at 2mm, 4mm, and 6mm from the apical foramen. Slices obtained were examined under the stereomicroscope. Data obtained were subjected to statistical analysis using chi square tests. Dentinal microcracks were observed in groups prepared using H files, ProTaper Universal, and ProTaper Next rotary files. Highest percentage of cracked root canals (20%) was seen in Group I, prepared by H files. These cracks were complete in nature, found in apical sections and statistically significant (p= 0.016). Group III prepared with ProTaper Next showed 10% dentinal cracks, followed by ProTaper Universal group with 5% cracked root canals. H files may be considered more aggressive at apical third due to complete cracks produced.

Efficacy of Laser Activated versus Sonic Activated Irrigation for Debris Removal in Conservatively Instrumented Root Canals.

To compare the efficacy of laser activated and sonic activated irrigation on the removal of debris in mesial root canal systems of mandibular molars using micro-computed tomographic analysis. Forty-eight mesial roots of extracted mandibular molars with isthmus were selected and randomly allocated into 2 groups: Sonic Group and Laser Group. The root canals were minimally instrumented to a maximum apical file size of 20/06v (DCTaper, SSWhite, NJ). The Sonic Group received irrigant activation using the SmartLite Pro EndoActivator (Dentsply Tulsa, OK) with a 15/02 tip. The Laser Group received irrigant activation using the WaterLase iPlus (Biolase, CA) with a RFT2 tip. The teeth were activated for the same time with the same volume of irrigants. Micro-computed tomographic scans were obtained preinstrumentation, preirrigation, and postirrigation. To quantify debris removal, the air-filled volume was measured preirrigation and postirrigation, and the percentage increase in air-filled volume was calculated. Data were analyzed statistically (independent samples t-test, significance set at 5%). The Laser Group demonstrated a significantly higher mean percentage increase in air-filled volume (37.4%) compared to the Sonic Group (20.2%). This difference was statistically significant (P<.05). The Laser Group was significantly more effective in removing debris compared to the Sonic Group in minimally instrumented root canal systems. However, due to the limitations of this study, further research is needed to assess the impact of laser activated irrigation on clinical outcomes.

Assessing Dentinal Microcracks using Micro-CT after Root Canal Preparation with Different Rotary Endodontic File Systems

ABSTRACT Objective: This study aimed to evaluate the propagation of dentinal microcracks in the mesiobuccal (MB) and mesiolingual (ML) canals following root canal preparation using two different rotary endodontic file systems, TruNatomy (continuous rotation) and MicroMega ONE RECI (reciprocating motion), using micro-computed tomography (micro-CT). Materials and Methods: Fifty freshly extracted human mandibular first and second molars were selected based on specific inclusion criteria. Root canal preparation was confined to the MB and ML canals in mesial roots of mandibular molars (Vertucci Type IV canal configurations) using TruNatomy and MicroMega ONE RECI systems. Pre- and post- preparation scans were taken for all the specimens using micro-CT to identify and measure dentinal microcracks. Statistical analysis was performed using a t-test and Fisher’s exact test, with significance set at P &lt; 0.05. Results: The results indicated no statistically significant differences between the two systems in terms of microcrack formation or propagation. In the ML canal, 8.0% of teeth prepared with TruNatomy and 12.0% with MicroMega ONE RECI exhibited microcracks (P = 0.643). In the MB canal, microcracks were found in 12.0% of the TruNatomy group and 8.0% of the MicroMega ONE RECI group (P = 0.643). Both systems showed a significant increase in canal volume, but no significant differences between the instruments (P &lt; 0.001). Conclusion: Both TruNatomy and MicroMega ONE RECI demonstrated similar outcomes regarding dentinal microcrack formation and propagation in the MB and ML canals, with no significant differences. Both systems were effective in enlarging the canals while preserving the natural canal anatomy. These findings suggest that the choice of instrumentation system can be guided by clinical ease and efficiency as both systems offer comparable mechanical effects on dentin integrity during root canal preparation.

Efficacy of the Orifice-Level Passive Ultrasonic Activation Technique in Removing Debris from Mandibular Molars: An Ex Vivo Study.

Introduction: This study aimed to evaluate the efficacy of the orifice-level passive ultrasonic activation (OL-PUA) technique in removing debris from the mesial root canals of mandibular molars, besides comparing it with other approaches, including manual dynamic agitation (MDA), EndoActivator, and laser-activated irrigation (LAI). Methods: Ninety mesial roots of mandibular molars were prepared up to 25.06 using the Race rotary system, filled with 3% sodium hypochlorite (NaOCl), and then they were randomly assigned to 5 groups (n=15) based on the activation protocol: MDA, EndoActivator, OL-PUA, LAI (using a diode laser), and needle irrigation (no activation). Moreover, one group served as the negative control using normal saline as the final irrigant. The roots were decalcified and sectioned into coronal, middle, and apical cross-sections. After histological staining, the remaining debris was assessed with an optical microscope and measured in the canals and isthmuses using histomorphometric analysis. Statistical analyses were performed by using one-way ANOVA and Tukey's HSD post hoc test (P=0.05). Results: Although less residual debris was observed after OL-PUA/LAI than using the EndoActivator/MDA methods, no significant difference was found between the four activation techniques at any root third (P>0.05). The OL-PUA/LAI group harbored significantly less remaining debris than the needle-irrigated samples at all root thirds (P<0.05). Debris accumulation increased from the coronal to the apical root thirds. Conclusion: No statistical difference was detected between the four activation techniques in terms of debris-removal performance, and none of them resulted in completely debris-free canals. Orifice-level PUA proved to be a promising approach with significant efficacy in removing debris compared to control groups.

Evaluation of the shaping ability of different rotary file systems in severely and abruptly curved root canals using cone beam computed tomography

BackgroundWhen selecting an instrument for canal preparation, it is important to consider several parameters that influence the shaping efficiency, including instrument design, metallurgy, and operating motion. This study aimed to evaluate the shaping ability of the ProTaper Next (PTN), WaveOne Gold (WOG), and XP-endo Rise Shaper (XPRS) rotary systems in severely and abruptly curved root canals using cone beam computed tomography (CBCT) and ImageJ software. Materials and MethodsForty-eight mesial root canals of the mandibular first molars were assigned equally to three groups: PTN, WOG, and XPRS. Using ImageJ software, CBCT images were acquired pre- and post-instrumentation to assess dentin removal, remaining dentin thickness (RDT), canal transportation, and centering ratio at the coronal, middle, and apical levels. Statistical analyses were conducted on all numerical data. ResultsAll rotary systems removed significantly more distocoronal dentin in the danger zone (DZ), than the mesiocoronal area. PTN removed significantly more dentin and caused less RDT than XPRS (p < 0.05). However, there were no significant differences between PTN-WOG and WOG-XPRS. In the DZ, the highest percentage of specimens with an RDT < 0.5 mm was observed when using PTN (50%), followed by WOG (31.3%), and XPRS (6.3%). Compared with PTN and WOG, XPRS demonstrated less coronal transportation. Among all rotary systems, there was no significant difference in apical transportation or centering ratio. ConclusionsBased on our observations, all rotary instruments exhibited a tendency to remove dentin in the DZ, but to different degrees. XPRS demonstrated better results in terms of coronal transportation and dentin thickness in the DZ. Comparable centering abilities and minimal apical transportation were demonstrated using all rotary instruments.

Does Root Canal Shaping Effect the Accuracy of Electronic Apex Locators in Curved and Straight Root Canals?

Objective: To assess the influence of root canal preparation (RCP) on the precision of electronic apex locators (EALs) in both straight and curved root canals. Methods: The experimental setup included forty-two extracted human mandibular molars featuring both straight distal canals (0-10 degrees) and curved mesial root canals (30-50 degrees). Initial working length (AWL1) measurements were conducted under a stereomicroscope at X15 magnification prior to root canal preparation (RCP). Subsequently, electronic working length (EWL1) was determined using two different electronic apex locators (EALs) – Propex-Pixi and EndoRadar. RCP was carried out with ProTaper Ultimate F1, F2 files in mesial canals, and F1, F2, F3 files in distal straight root canals. The RCP procedure involved the implementation of a standard irrigation protocol along with the use of a sonic device for activation. Following RCP, measurements were repeated under a stereomicroscope and documented as AWL2. EWL measurements were also repeated and recorded as EWL2 after the preparation. The variation was calculated by subtracting AWL from EWL for each tooth (EWL1-AWL1 and EWL2-AWL2). Statistical analysis employed Paired Sample t-test and Wilcoxon tests. Results: There was no statistically significant difference observed in the accuracy of Propex-Pixi and EndoRadar Pro before and after root canal preparation for both straight and curved canals. Conclusion: Root canal preparation did not alter the accuracy of the electronic apex locators (EALs) used in this study, whether applied to curved or straight root canals.

Quality of Root Canal Filling in Curved Canals Utilizing Warm Vertical Compaction and Two Different Single Cone Techniques: A Three-Dimensional Micro-Computed Tomography Study.

Successful endodontic treatment depends on three-dimensional (3D) root canal filling to prevent the leakage of residual bacteria. Different obturation techniques with different sealers should be compared by employing advanced assessment tools. This study compared the obturation quality of warm vertical compaction (WVC) and two different single-cone (SC) techniques using micro-computed tomography (micro-CT). Thirty-three extracted maxillary molars with mesial root canal curvature of 20‒40º were prepared in vitro with One-Curve files and randomly assigned to three groups (n=11) for root canal obturation with WVC, SC technique with AH Plus sealer (SC-AH), or SC technique with SureSeal bioceramic (BC) sealer (SC-Su). The root canals underwent micro-CT examinations before and after obturation to determine the volume percentages (VPs) of voids and gaps at different distances from the apex (coronal, middle, and apical thirds). Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests. The highest VP of voids and gaps was recorded in the SC-Su group, with no significant difference from other groups (p> 0.05). There were significant differences in VP of gaps at different distances from the apex (p<0.05). The VPs of gaps in the apical third of all the samples were significantly higher than in the coronal and middle thirds. However, the difference in VP of voids was not significant at different distances from the apex (p>0.05). None of the tested techniques could provide a void-free and gap-free filling. The apical third of the canals showed the highest VP of gaps in all obturation techniques.

Microcomputed tomographic evaluation of 6 NiTi files on the pericervical dentin and the smallest dentin thickness zones in mesial root canals of mandibular molars: an in vitro study.

The aim of this study was to evaluate six files on the pericervical dentin (PCD) and the smallest dentin thickness zones (SDTZ) in mesial root canals of mandibular molars. Sixty mandibular molars with two mesial canals and Vertucci configuration were aleatory allocated in 6 experimental groups of 10 molars and 20 root canals. Specimens were scanned before instrumentation using the SkyScan 1275 (Bruker microCT, Kontich, Belgium). Group 1 was treated with WaveOne Gold (WG), group 2 with Reciproc Blue (RB), group 3 with TRUShape (TS), group 4 with XP-endo Shaper (XP), group 5 with iRace (IR), and group 6 with TruNatomy (TN). After instrumentation, the molars were scanned again and the images recorded were reconstructed with the NRecon v.1.7 (Bruker micro-CT) and analyzed with CTAn v.1.20.8 software (Bruker micro-CT) quantifying the changes produced in the surface, volume, structure thickness, SMI, and centroids at the Pericervical Dentin area of the root canals (PCD) located from the root canal orifices at the floor of the pulp chamber to 4 mm in the apical direction, and the changes in the Smallest Dentin Thickness Zones (SDTZ) located (from the furcation to 4 mm and 7 mm in the apical direction. The data obtained were compared using Wilcoxon and ANOVA with a 5% significance level. XP and TN were similar in all the parameters (P >.05) at the PCD, but TN showed significant differences from WG, RB, TS, and IR (P <.05), while XP showed significant differences from WG (P <.05) in volume, surface, and structure thickness. Regarding the changes in the SDTZ, the amount of dentin removed was similar between the groups in both canals at the middle 1/3, at the cervical 1/3 for MB canals, and in ML canals for RB, TS, XP, IR, and TN (P>.05). The action of WG was significantly different from that of XP and TN in the cervical 1/3 of the ML canal (P <.05). XP and TN rotatory files with small taper and volume maintained better with minor changes at the PCD and SDTZ, while WG reciprocation file produced the largest change. All the files were maintained centered at the PCD, and their performances were safe with a minimal thickness higher 0.5 mm at the SDTZ, and without risk of perforation. No clinical trials were indicated in this study. The choice of endodontic files is a relevant factor in the conservative performance of root canal treatments.

Can the addition of surfactants to NaOCl irrigation impact on the percentage of voids of root canal filling?

This study evaluated the impact of canal irrigation using surfactants associated to NaOCl on the percentage of voids of root canal filling through micro-computed tomographic (micro-CT) analysis. 27 mandibular mesial roots with Vertucci type II canal configuration with isthmus were selected and scanned in a micro-CT device. The specimens were assigned to three groups (n = 9), according to the irrigation solution during instrumentation: 2.5% NaOCl without additives (control), 2.5% NaOCl with 0.1% Benzalkonium Chloride and 2.5% NaOCl with 0.1% Tween 80. After obturation, the specimens were rescanned, and the percentage of voids were calculated. Data were analysed using one-way ANOVA with a significance level of 5%. The percentage of voids were similar among the groups (p > 0.05). None of the specimens showed completely voids-free areas. The addition of surfactants to NaOCl irrigation did not improve the quality of root canal filling of mandibular mesial root canals.

Micro-CT Assessment of Filling Removal Effectiveness in the Apical Third of Curved Canals with Different Types of Anatomy.

The aim of this study was to assess the effectiveness of filling removal material from the apical third of curved mesial root canals of mandibular molars. Reciprocating instrumentation followed by additional rotary instrumentation with instruments made of alloys with different heat treatments was evaluated. Thirty-six mesial roots of mandibular molars were divided into two groups: Group Class IV consisted of 16 roots with two independent canals, and Group Class II consisted of 20 roots with two canals that merged into one at their apical level. Each of these two groups were further divided into two subgroups, according to the additional rotary instrument used after the reciprocating instrumentation: Group RH and Group RM for Hyflex and Mtwo, respectively. After each procedural step, the roots were scanned by micro-tomography. After each step of filling removal, the Wilcoxon matched pair test and the Mann-Whitney test were used for the evaluation between groups. The significance level adopted was 5%. Significant differences were observed between groups with different Class II and Class IV anatomies, regarding filling removal after Reciproc (P<0.05). After the use of an additional rotary instrumentation, no differences were observed between the two groups (P>0.05). In the apical third of mesial roots of mandibular molars with Class II anatomy, an additional rotary instrumentation was shown to be necessary for improving the removal of filling material after using the single-file reciprocating instrumentation technique.

Prevalence of middle mesial root canal in mandibular molars in an Iranian population: A micro-computed tomography study

ABSTRACT Background: Knowledge about the anatomic variations of the root canal system and their prevalence is necessary for clinicians to ideally clean the root canal system. The anatomic complexity of the root canal system is one of the reasons for its inadequate debridement, resulting in residual microorganisms and root canal treatment failure. The present study aimed to evaluate the prevalence of middle mesial root canals in mandibular molars in an Iranian population. Materials and Methods: The samples in the present descriptive/cross-sectional study consisted of mandibular first and second molars (n = 100, with 50 first and 50 s molars). A convenient sampling method was used to collect samples. The teeth were mounted in gypsum and scanned using a micro-computed tomography unit. The images were reconstructed with software, and the relevant checklist was completed by the observers. The data were analyzed with SPSS v26 using the Chi-squared test at a significance level of P &lt; 0.05. Results: The prevalence of the middle mesial root canal in the present study was 36% for mandibular first molars and 22% for mandibular second molars, with an overall prevalence of 29%. The prevalence of the middle mesial root canal was not significantly different between the first and second mandibular molars (P = 0.12). The mean distance between the mesiobuccal and mesiolingual root canal orifices in the teeth with a middle mesial root canal was significantly higher than in those without the middle mesial root canal (P &lt; 0.001). In addition, there was no significant difference in the prevalence of the middle mesial root canal between the teeth with and without the second distal root canal (P = 0.89). Conclusion: The prevalence of the middle mesial root canal in the studied population was 29%, which is significant clinically. In addition, the mean distance between the mesiobuccal and mesiolingual root canal orifices in teeth with a middle mesial root canal was higher than that in teeth without this root canal.

Antimicrobial activity of Er,Cr:YSGG and Ultrasonic on E. faecalisbiofilm in the mesial root canal systems of lower molars

Antimicrobial activity of Er,Cr:YSGG and Ultrasonic on E. faecalisbiofilm in the mesial root canal systems of lower molars

Influence of sealer and supplementary approach on filling material removal during endodontic retreatment.

Both root canal sealer-based and supplementary protocols may influence removal of filling material during endodontic retreatment. Mesial root canals of extracted mandibular molars were prepared using HyFlex EDM 25/.08, and filled with a calcium silicate sealer (Bio-C Sealer), or an epoxy resin (AH Plus), using the single cone technique (n = 12). Retreatment was performed using ProDesign Logic (PDL) RT and PDL 35/.05. The specimens were randomly divided into two experimental groups (n = 12), and the sealers were distributed similarly. A supplementary protocol was performed with PDL 50/.01 or XP-endo Finisher. Root canal transportation and volume, in addition to the remaining filling material percentage were evaluated using high-resolution (5 µm voxel size) micro-CT. Statistical analysis was performed using t-tests (α = 0.05). Root canals filled with AH Plus presented high residual filling material (p < 0.05). Both protocols decreased residual volume of filling material in the apical third (p < 0.05). PDL 50/.01 increased the apical root canal volume (p < 0.05). No difference was observed between the systems regarding canal transportation (p > 0.05). In conclusion, AH Plus is more difficult to remove from the apical third than Bio-C Sealer. PDL 50/.01 and XP-endo Finisher enabled greater removal of filling materials in the apical third, in the retreatment of curved root canals, without promoting apical transport.

Natural canal deviation and dentin thickness of mesial root canals of mandibular first molars assessed by microcomputed tomography.

The aim of this study was to assess the centralization and dentin thickness of mesial root canals of the first mandibular molars by microcomputed tomography (micro-CT). Material and methods: Ninety-nine mandibular molars of Vertucci's type IV canals were scanned by micro-CT. The mesiodistal deviation and centroid were assessed, in both mesiobuccal (MB) and mesiolingual (ML) canals, for the apical 4mm and the full canal length. Results: The dentin thickness was similar for both MB and ML canals. The narrowest thickness was in the distal wall of an MB canal (0.07mm), while the widest was found in the mesial wall of an MB canal (2.46mm). In centroid analysis, both the MB and ML canals exhibited deviations when compared to the root centroid, along the full canal length and the apical 4mm. For the MB canal, the mean deviation was 0.83mm (0.02 mm-2.30 mm) for the full canal and 0.18mm (0.01 mm-1.01 mm) for apical 4mm. Similarly, for the ML canal, the mean deviation measured 0.83 mm (0.05mm-3.99mm) for the full canal and 0.21 mm (0.01mm-1.01mm) for the apical 4 mm. Overall, deviations were observed towards the mesial of the roots, with 69% for MB and 57% for ML canals for the full canal, and 51% for MB canals within the 4 mm. The exception was the ML canal, which exhibited a higher deviation towards distal in the apical 4mm, accounting for 52% of cases. The dentin thickness was consistent between the mesial canals of mandibular molars. However, there is no centrality of mesial canals in their roots, with frequent deviation to mesial.

Evaluation of the Quality of Canal Obturation Using the Continuous Wave Method after Shaping with Different NiTi Rotary Instruments by Micro-CT

Abstract Objective The aim of this article was to evaluate the influence of mesial root canal preparation of mandibular molars with the reciprocal systems (RCP) and self-adjusting file (SAF) in the incidence of voids spaces in endodontic obturation performed by modified continuous wave compaction (MCWC) technique, through images obtained in micro-computed tomography (micro-CT). Materials and Methods Mesial roots of 15 mandibular molars, with two independent root canals, were divided into three groups (n = 5/roots), according to the endodontic instrumentation strategy (RCP, SAF, and twisted file [TWF]). After the root canals (n = 10, for each instrumentation system) were filled with MCWC, images of each specimen were obtained by micro-CT followed by three-dimensional reconstruction. The percentage of voids was obtained (in mm3) in relation of the total volume, cervical–middle, and apical thirds. Statistical Analysis The data obtained were submitted to statistical analysis by Kruskal–Wallis and Dunn tests (p &lt; 0.05). Results With respect to the total volume of root canal, TWF demonstrated a lower percentage in comparison to SAF (p &lt; 0.05). No significant difference was obtained between TWF and RCP or RCP and SAF (p &gt; 0.05). In the apical third, RCP showed a smaller percentage of voids when compared with SAF (p &lt; 0.05); however, TWF demonstrated similarity with RCP and SAF (p &gt; 0.05). The middle–cervical third exhibited no statistically difference between TWF and RCP or RCP and SAF (p &gt; 0.05), whereas TWF was lower than SAF (p &lt; 0.05). Conclusion Root canal preparation of mesial root of mandibular molars with TWF provides a lower incidence of voids in the endodontic filling performed by MCWC.

Morphological assessment of the isthmus in mesial root canals of first mandibular molars.

The aim of this in silico study was to perform a qualitative and quantitative analysis of the threedimensional morphological characteristics of the isthmus in the mesial root canals of mandibular molars using microcomputed tomography (micro-CT). Six hundred first mandibular molars were selected, including 317 with two mesial canals with isthmuses between the canals, and fully formed root. Isthmus morphology was determined in 3D longitudinal sections using Fan et al. (2010) classification. Root length, and the volume and area of apical and coronal level were measured. Additionally, the structural model index (SMI) of the canals were also assessed. The prevalence of isthmuses in the mesial root canals was 32% type II, 29% type III, 22% type IV, and 17% type I. The root length was found to be 9.1±0.5 mm, the volume and area, of all root canal system, were 41.8±40.1 mm3 and 63.6±24.2 mm2 respectively. The isthmi volume and area alone were 11.06±9.03 mm3 and 30.02±11.02 mm2. The study confirmed that isthmuses are present in mesial canals of mandibular first molars, being more frequent in the apical third. The high prevalence of isthmuses with complex morphological features underscores the importance of using intracanal medications to disinfect areas unprepared by instruments.

Efficiency and complications in root canal retreatment using nickel titanium rotary file with continuous rotation, reciprocating, or adaptive motion in curved root canals: a laboratory investigation

BackgroundIt is currently unknown whether rotary file motion affects the best outcome of root canal retreatment. This experimental study compared the efficacy, efficiency, and complications of single-use NiTi rotary files using continuous rotation, reciprocating, and adaptive motions in root canal filling removal in curved root canals. Reciproc blue R25 was used with reciprocating motion (RB), VDW.ROTATE retreatment files with continuous rotation (VR), and ProTaper NEXT X2 with continuous rotation (PTNc) or adaptive motion (PTNa).MethodsForty mesial root canals of extracted mandibular first and second molars with an angle of curvature between 20°–40° and a radius of curvature between 5 and 10 mm were collected. The specimens were instrumented and obturated with gutta-percha and AH Plus sealer using the continuous wave of condensation technique. The specimens were randomly divided into 4 retreatment groups (n = 10), RB, VR, PTNc, and PTNa. The percentage of root canal filling removal in each group was analyzed using Micro-Computed Tomography (µCT). The motor running time, total time, root canal complication, and instrument complication were recorded and statistically analyzed (p-value < 0.05).ResultsThe pre-operative root canal curvature and root canal filling volume were comparable among groups. The percentage of root canal filling removal from the whole canal in the PTNc, RB, PTNa, and VR group was 98%, 96%, 95%, and 93%, respectively. A significant difference was observed between the PTNc and VR groups for the whole canal and the apical-third part. The motor running time and total time were significantly different between the groups. Instrument fracture was observed at 40% in the VR and 20% in the PTNa group, but none in the RB and PTNc groups.ConclusionsThe ProTaper NEXT X2 with continuous rotation and RB files can be used with high efficacy and efficiency in curved root canal retreatment. Continuous rotation is more efficacious and efficient than adaptive motion when using the NiTi rotary file. Single file retreatment can be used in small canals with high efficacy, cost-effectiveness, and less time consumption.

Shaping outcomes of Reciproc Blue and Rotate in roots canals with band-shaped isthmuses: micro-CT study.

This study assessed the outcome of shaping the mesial roots of mandibular first molars containing band-shaped isthmuses with an isthmus floor located at the apical third with Reciproc Blue and Rotate instruments in terms of canal transportation, canal aberrations and unprepared apical canals. Pair-matched mesial roots of mandibular first molars according to their isthmus location (distance from apical foramina) and size were constructed based on quantitative measurements (length, major and minor diameter at isthmus roof and floor) on preoperative micro-CT scanning (n = 10). The pair-matched specimens were prepared either using Reciproc Blue R25 (25.08v) or Rotate (15.04, 20.05, 25.06) instruments and then subjected to a second micro-CT scanning. Micro-CT scans were analysed to evaluate the canal transportation at the apical foramen and isthmus floor levels and the frequency of procedural errors (separated instruments, artificial canal preparation, cross shaping and unprepared apical canals). Canal transportation values were compared using Mann-Whitney U, and the distribution of procedural errors was compared with chi-square tests with a 5% significance threshold. Greater transportation values were detected in the apical foramen level compared to the isthmus floor in both groups. No significant difference was detected between Rotate and Reciproc Blue groups in terms of absolute transportation values and the incidence of procedural errors (p > .05). Preparation of mesial root canals containing a band-shaped isthmus at the apical portion with Reciproc Blue and Rotate instruments caused transportation of the original canal position at the isthmus floor and the apical foramen levels and resulted in procedural errors. This ex vivo micro-CT study using controlled pair-matched specimens showed that presence of a band-shaped isthmus complicates canal preparation procedure irrespective of the preparation systems.