Canals Of Mandibular First Molars Research Articles

Micro-computed tomographic evaluation of the shaping ability of three nickel-titanium rotary systems in the middle mesial canal of mandibular first molars: an ex vivo study based on 3D printed tooth replicas

BackgroundThe preparation of the middle mesial (MM) canal of mandibular molars represents a challenge because it is often curved, narrow, and close to the root concave. The purpose of this study was to evaluate the ex vivo shaping ability of 3 nickel-titanium (NiTi) rotary systems in the MM canal using 3D printed resin tooth replicas.MethodsA permanent mandibular first molar with a MM canal was acquired from a pool of extracted teeth and reproduced by a 3D printer. The resin tooth replicas (n = 18) were equally assigned to 3 groups for the evaluation of the shaping abilities of 3 NiTi rotary systems (OneShape [OS], Twisted Files [TF], and ProTaper Gold [PTG]) according to the manufacturer’s recommendations. The tooth replicas were scanned by micro-computed tomography (micro-CT) twice before and after instrumentation of the mesiobuccal (MB), mesiolingual (ML), and MM root canals. After 3D reconstruction, the canal straightening, change of root canal volume and surface area, the mesial and distal canal wall thickness and canal transportation at the levels of 1, 2, and 3 mm below furcation were assessed. One-way variance analysis and Turkey’s post hoc test were used for comparisons of the means among different groups, and paired-t test was used to compare the mesial and distal sides of the mesial roots.ResultsAs compared with OS and TF, the use of PTG in preparation of MM canals resulted in significantly more straightening of canal curvature (p < 0.05), greater post-instrumentation canal volume and surface area, and thinner mesial and distal remaining canal wall thickness at 1, 2 and 3 mm below furcation (all p < 0.05). Regarding the root canal transportation in the mesiodistal direction, there was no significant difference among the 3 instruments (all p > 0.05) after the preparation of the MB and ML canals. However, in the MM canal, more pronounced transportation was detected in the PTG group at 2 mm below furcation, and in the TF group at 3 mm below furcation as compared with the other 2 systems (both p < 0.05).Conclusions3D printed tooth replicas have the advantages of consistency and can be an ideal model to evaluate the shaping ability of different instruments in the MM canal. OS and TF files performed similarly and both are appropriate for shaping the MM canal, while PTG may cause excessive and uneven resin removal, especially near the furcation, and may lead to root fragility and procedural errors.

Evaluation of apical transportation and centering ability of three single-file systems in severely curved canals using micro-computed tomography

Background: This study aimed to compare the apical transportation and centering ability of One Curve, HyFlex EDM, and EdgeFile X1 in curved mesiobuccal and mesiolingual canals of mandibular first molars. Materials and Methods: In this in vitro experimental study, 60 mesiobuccal and mesiolingual canals of the mandibular first molars with a minimum length of 19 mm and 25°–40° curvature were randomly divided into three groups (n = 20) for root canal preparation with One Curve, HyFlex EDM, and EdgeFile X1. After access cavity preparation and confirming the glide path, the baseline micro-computed tomography (micro-CT) scans were obtained, and the root canals were instrumented with the respective systems according to the manufacturers’ instructions. Apical transportation and centering ability were assessed at 1, 3, 5, and 7 mm from the apex by comparing pre- and postinstrumentation micro-CT scans. One-way ANOVA, independent t-test, and Duncan's post hoc test were used to statistically compare the groups, and data were analyzed by SPSS version 24 (alpha = 0.05). Results: The three groups were not significantly different regarding apical transportation at 5 and 7 mm from the apex (P &gt; 0.05). At 1 mm level, One Curve caused significantly lower apical transportation; while, at 3 mm level, HyFlex EDM resulted in significantly higher apical transportation (P &lt; 0.05). No significant difference was noted in the centering ability of the three groups at 1, 3, and 5 mm from the apex (P &gt; 0.05). At 7 mm level, EdgeFile X1 showed significantly lower centering ability (P &lt; 0.05). Conclusion: One Curve caused lower canal transportation in the apical third compared with EdgeFile and HyFlex EDM, but no significant difference was noted among the three in the coronal third of the roots.

Prevalence and morphology of middle mesial canal in mandibular first molars in an Indian sub-population: A cone-beam computed tomographic analysis

Aim: The aim of this study was to check for the prevalence and morphology of middle mesial (MM) canals in mandibular first molars in an Indian population divided as per the different zones of the country using cone-beam computed tomography (CBCT) scans. Methods: A total of 452 CBCT scans were selected according to the inclusion and exclusion criteria on December 2021. The scans were obtained from five different zones of the country with 80–100 scans selected from each zone. They were checked in an axial view to see for the presence of a MM canal (MMC) and if present, were confirmed in a coronal view. Results: Of the 452 scans viewed, 39 showed the presence of MMCs (8.6%). Bilateral presence was seen in 8 scans (1.8%). Hence, overall, 47 molars out of 904 examined showed the presence of MMCs. Thus, the tooth prevalence rate for the presence of MMC was 5.2%. Seventy percent of teeth presenting with MMCs showed two apical exits. Males showed more prevalence when compared to the female population (10.25% vs. 6.88%, P &lt; 0.05). Furthermore, with increasing age, there was a consistent decrease in the incidence of MMCs (P &lt; 0.05). Conclusion: Overall, the prevalence of MMCs in an Indian sub-population is 8.6%. Although on a lower range compared to other population, careful exploration is necessary to avoid missing the MMC which might lead to failure of treatment. Age and gender are also found as the important factors that influence the presence of a MMC.

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.

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.

Comparative Evaluation of Root Canal Transportation and Centering Ability in Curved Mesiobuccal Canals of Mandibular First Molars after Instrumentation with Different File Systems-An In vitro Study.

To assess the canal transportation and centering ability in the mandibular first molars' curved mesiobuccal canals after instrumentation with file systems XP endo Shaper, self-adjusting File (SAF), Hyflex EDM, Pro Taper NEXT, WaveOne Gold, and K files with the help of Cone-Beam Computed Tomography (CBCT). Ninety recently extracted mandibular first molars with mesiobuccal roots that had a 25-30 degree canal curvature were assessed. Following preoperative CBCT scans, teeth were allocated randomly to six experimental groups of fifteen. After preparation with XP endo Shaper, SAF, Hyflex EDM, Pro Taper Next, WaveOne Gold, and K files, post-instrumentation scans were taken using same parameters as pre operative scans. At 3 mm, 6 mm, and 9 mm from the apex, samples were assessed for canal transportation and centering ratio. Apical transportation was least for XP endo Shaper as compared to other groups except SAF and the results were statistically significant. K file showed the highest apical transportation toward the lateral wall of the root canal. XP endo Shaper was better in maintaining centering ability of middle and apical third of canal and SAF was better in maintaining centering ability of coronal third. In root canal preparation, least apical transportation and better centering ability with XP endo Shaper than other file systems compared. K file showed the highest transportation.

Taper 0.06 Versus Taper 0.04: The Impact on the Danger Zone

IntroductionThis study aimed to evaluate the effects of root canal enlargement on the danger zone (DZ) of mandibular molars. MethodsThirty mesial roots of mandibular first molars were scanned in micro-computed tomography (S1). Canals were sequentially enlarged with rotary instruments up to sizes 30/0.04 (S2) and 30/0.06 (S3). The dentin thickness was measured at 0.1-mm intervals after each preparation step (n = 2964 slices). Root level and position of the DZ were also recorded. Data were compared using analysis of variance with Bonferroni pairwise comparison, Cochran's Q method, and Pearson's test (α = 5%). ResultsComparing the specimens before (S1) and after (S2 and S3) preparations showed a significant reduction in the thickness of the DZ (P < .05), as well as between S2 and S3 steps (P < .05). At S1, the DZ was mostly located in the middle third of the root, but after preparation, it shifted toward the coronal direction (P < .05). Both S2 (P = .004, r = 0.508) and S3 (P = .004, r = 0.506) preparation steps showed a positive correlation between canal length and the root level of the DZ. At S1, the DZ was positioned toward the distal and mesial in 73.4% (n = 22) and 26.6% (n = 8) of the specimens, respectively. After S3, the number of specimens with DZ positioned toward the mesial aspect of the root significantly reduced to 3.3% (n = 1), whereas none of the specimens with DZ positioned toward the distal changed its position after root canal enlargements (P > .05). ConclusionOverall, the enlargement of mesial canals of mandibular first molars with final instruments sizes 30/0.04 and 30/0.06 affected the thickness, root level, and position of the DZ.

PRESENCE OF EXTRA CANAL IN PERMANENT MANDIBULAR FIRST MOLAR

Background: The success of root canal therapy depends on proper knowledge of root canal system, presence of extra canals, complete debridement and three-dimensional obturation of the entire root canal system. Previous studies have reported three to five canals in mandibular first molars. There might be chance of missing the canal that may lead to root canal failure, because of the variability in the number of root canals. The objective of this study was to determine the percentage of extra canal in the permanent mandibular first molar in patients undergoing root canal treatment. Methods: This cross-sectional study was conducted in the Department of Conservative Dentistry and Endodontics of Peoples Dental College and Hospital over a period of ten months from 6th September 2021 to 31st July 2022 after receiving ethical clearance from Institutional review Committee (IRC) Peoples dental college on 5th September 2021 (ref no1/ch no 5,2078/2079). About 350 mandibular first molar was selected by convenient sampling. After access preparation, all canal orifices were located and data were recorded. Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 22.0 with frequency table. Results: Out of 350 patients, the percentage of three canals, four canals and five canals were respectively 273(78%), 76(21.7%) and 1(0.3%). Conclusions: The finding of this study supports the presence of extra canals in mandibular first molar. Thus, the clinicians require more diagnostic approaches, access modifications, and skills to locate, clean and shape the entire root canal system.

Prevalence of middle mesial canals in mandibular first molars in coastal Andhra population – A Cone beam computed tomography study

Introduction: Recognition of variations in root canal anatomy is an essential prerequisite for successful endodontic diagnosis and treatment. Most of the endodontic failures result from missed canals. The mandibular first molar has the most complex root canal system and a high percentage of treatment failures are due to the impossibility of locating, instrumenting and obturating the middle mesial canal (MM). There are very few studies available regarding the incidence of MM canal in mandibular first molar. The present study evaluated the prevalence of the middle mesial canals in mandibular first molars using cone beam computed tomography (CBCT). Materials and Methodology: CBCT images of mandibular first molars were collected from patients (n= 100) who had undergone CBCT imaging. The images were analyzed and the prevalence of MM canals were calculated. Results: The data were analysed using descriptive statistics. In total of 100 patients, 60 were women and 40 were men, with age range 11-60 years old. 21 MM canals were identified in this study. In this, 11 were female and 10 were male. The prevalence of the MM canal in mandibular first molar MM canals were identified in 21% (21/100). Conclusion: Within the limitations of the study, it can be concluded that though advanced techniques like troughing and magnification help in finding and negotiating MM canals, 3D radiographies like CBCT can be as used as valuable adjunct to the above mentioned methods. When these canals are treated, the success rate of the endodontic treatment would definitely increase. Clinical studies with long-term follow-ups are needed to determine the effect of preparation of MM canals on the outcome of nonsurgical endodontic treatment in mandibular first molars. Keywords: Cone Beam Computed Tomography, Mandibular First Molar, Middle Mesial Canal, Prevalence.

Centering ability and root canal transportation of protaper gold and v taper gold using cone-beam computed tomography: An in vitro study

Introduction: This study aimed to evaluate the central ability and root canal transportation of two types of rotary files in curved molar canals using cone-beam computed tomography (CBCT) in mesiodistal (MD) and buccolingual (BL) directions.Method and Material: A total of 40 mesiobuccal root canals of mandibular first molars with an angle of 25-35 degrees and radius curvature of 5 millimeters were randomly divided into two groups of 20 canals each. Group A was prepared with Pro Taper Gold (PTG), and Group B with V Taper Gold (VTG). Pre- and post-instrument CBCT scans were recorded. Images were reconstructed, then cross-sections were detected corresponding to distances of 3, 6, and 9 mm from the anatomic apex using Gambill’s method. Statistical analysis was performed with T-test and repeated measure ANOVA. P-value was set at 0.05.Results: There was a significant difference in centering ratio and canal transportation at all three levels of 3-, 6-, and 9- mm, mesiodistally. PTG has higher centering ability in 6 mm and 9 mm sections with more canal transportation at 3 mm and 6 mm. In the BL direction, no statistically significant difference in central ability was observed among the PTG and VTG groups. The centering ability of both groups became higher from the apex to the coronal part. The last and the most canal transportation in both PTG and VTG groups was reported at 6 mm level and 9 mm level, respectively.Conclusion: Both rotary instruments efficiently cleaned and shaped curved canals. ProTaper Gold had better centering ability, while V Taper Gold showed less canal transportation.

Middle mesial canal

The occurrence, instrumentation, and obturation of the isthmus between the mesiobuccal and mesiolingual canals in mandibular first molars were studied. The morphology of these middle mesial canals was as follows: eight fins, two confluent canals, and two independent canals. Failures of root canal treatment are mainly due to missed canals and ignorance about the anatomy of the root canal system. The middle mesial (MM) canal is one such type of canal in mandibular molars which is often missed. This case series explain and illustrates three cases with middle mesial canals which is treated successfully.

Assessment of the middle mesial canals of mandibular first molars using cone-beam computed tomography: an in vivo study.

For a successful root canal therapy, it is necessary to locate all the canals debride and seal them with an inert filling material. The clinician must be aware of the internal morphology and variations in a permanent tooth. Mandibular first molars are widely studied to identify variations in the anatomy of the pulp space. In this study, the primary objective was to measure the distance between the mesiobuccal (MB) and mesiolingual (ML) canals in patients with and without a middle mesial canal (MMC) using cone-beam computed tomography (CBCT). The secondary objectives were to assess the tapering degree of the mesial root and to measure the dentinal thickness in relation to the danger-zone area in patients with and without an MMC. A total of 200 CBCT scans were evaluated for the presence of an MMC. Two observers performed the observations, and the results obtained were subject to statistical analyses. The results revealed the prevalence of MMC was 5%. The average distance between the MB and ML canals was higher when there was an MMC [M(SD) = 3.61 (0.6) vs. 2.69 (0.66)]. However, there were no differences between the groups in the distance to the danger-zone area and the tapering degree of the mesial root. On CBCT images, the MMC was clearly visible 3 mm apical to the level of the cementoenamel junction; beyond 3 mm, the MMC could not be traced. Based upon the results of this study, the average distance between the MB and ML canals was higher when there was an MMC. A lesser degree of taper would be preferred to prepare the MMC than to prepare the other canals. It is recommended that careful examination of the canal 3 mm apical to the cementoenamel junction should be carried out when attempting to detect an MMC.

Kayma yolu oluşturulmasının apikalden çıkan debris miktarına ve kök kanal anatomisinin korunmasına etkisi

Purpose: This study aimed to investigate the effect of glide path preparation before shaping with reciprocating single-file, rotary single-file and multiple-file systems on the debris extrusion from the apical, and on the root canal transportation. &#x0D; Materials and Methods: One hundred twenty curved mesial root canals of mandibular first molars were randomly distributed to six groups (n=20). The root canals were prepared with Reciproc in Group R, OneShape in Group OS, and ProTaper Next in Group PN. In the last three groups (RG, OSG and PNG), a glide path was created before the shaping instruments used in the first 3 groups. The pre- and post-preparation weight were measured by using a 10-5 microbalance. Pre- and post-preparation of the root canals were scanned by using cone-beam computed tomography (CBCT). &#x0D; Results: The debris extrusion in RG and OSG was significantly higher than R and OS, respectively. However, no significant differences were found between PN and PNG. Considering the root canal transportation, RG showed lower than R for 5 mm and 7 mm levels and the OSG group showed lower than OS for all levels. Creating a glide path significantly increased the shaping time for OS and PN groups. &#x0D; Conclusion: In advance of shaping with a single-file system in curved canals, creating a glide path preserves canal anatomy. However, it may lead to increase apical debris extrusion.

Comparison of Canal Transportation in TruNatomy, ProTaper Gold, and Hyflex Electric Discharge Machining File Using Cone-beam Computed Tomography

This study was carried out to compare canal transportation in three new rotary file systems, namely TruNatomy, ProTaper Gold, and Hyflex Electric Discharge Machining file system, using cone-beam computed tomography. The study was conducted on 105 extracted teeth consisting of 60 extracted mandibular first molars and 45 mandibular second premolars involving the mesiolingual canal of mandibular first molar and the root canal of second premolar. The teeth were randomly divided into three groups of 35 out of which each group consisted of 20 mandibular first molars and 15 mandibular second premolars. The TruNatomy rotary file was used in group I, ProTaper Gold was used in group II, and Hyflex Electric Discharge Machining was used in group III. Cone-beam computed tomography scan images were obtained both before and after instrumentation. Changes caused by preparation in the coronal, middle, and apical thirds were determined on cone-beam computed tomography scans and analyzed using the Kruskal-Wallis test at p ≤ 0.05 level of significance. TruNatomy showed least amount of canal transportation as compared with other two file systems at all the three levels of canals. ProTaper Gold showed maximum amount of canal transportation as compared with other two file systems at all the three levels of canals. The Hyflex EDM rotary file system showed transportation, which was more than the TruNatomy file system while it was less than that of ProTaper Gold. The difference was statically significant at the middle one-third level (p = 0.03) and at the coronal level (p = 0.02). The TruNatomy system has least amount of canal transportation as compared with ProTaper Gold and Hyflex EDM system. With potential to preserve tooth structure, this file has an added advantage over other rotary file systems. The TruNatomy file system has been recently introduced with good cyclic fatigue resistance. It is necessary to evaluate the root canal transportation caused by the TruNatomy file.

The Effect of Ultrasonic Agitation on the Porosity Distribution in Apically Perforated Root Canals Filled with Different Bioceramic Materials and Techniques: A Micro-CT Assessment.

The present study evaluated the effect of ultrasonic agitation on the porosity distribution of BioRoot RCS/single gutta-percha cone (BR/SC) and MTA Flow (MF) root canals fillings used as apical plugs in moderately curved and apically perforated roots. Eighty mesial root canals of mandibular first molars were enlarged up to ProTaper NEXT X5 rotary instrument 2 mm beyond the apical foramen, simulating apical perforations. Specimens were randomly divided into four experimental groups (20 canals per group) according to the material and technique used for root canal obturation: BR/SC, BR/SC with ultrasonic agitation (BR/SC-UA), MF and MF with ultrasonic agitation (MF-UA). The ultrasonic tip was passively inserted into the root canal after the injection of flowable cement and activated for 10 s. The specimens were scanned before and after obturation with a high-resolution micro-computed tomography scanner, and the porosity of the apical plugs was assessed. The differences between groups were analyzed using the Kruskal-Wallis and Mann-Whitney tests, with the significance level set at 5%. None of the obturation materials and techniques used in this study was able to provide a pore-free root canal filling in the apical 5 mm. Considerably higher percentages of open and closed pores were observed in the MF and MF-UA groups, with the highest porosity being in the MF-UA group (p < 0.05). No significant differences were observed between the BR/SC and BR/SC-UA groups, where the quantity of open and closed pores remained similar (p > 0.05).

Static Cyclic Fatigue Resistance in Abrupt Curvature, Surface Topography, and Torsional Strength of R-Pilot and ProGlider Glide Path Instruments

IntroductionThis study aimed to compare ProGlider (Dentsply Sirona, Ballaigues, Switzerland) and R-Pilot (VDW, Munich, Germany) instruments in terms of their cyclic fatigue resistance using an artificial stainless steel canal showing an abrupt apical curvature, torsional resistance according to the ISO specification, and topographic changes on the instrument surface after glide path management in mesial canals of mandibular first molars with the abrupt curvature selected based on their micro–computed tomographic examination. MethodsEighty instruments were used: 40 ProGlider (size 0.16, .02v taper) and 40 R-Pilot (size 0.125, .04 taper) instruments. The cyclic fatigue resistance was tested in a static test model using an artificial canal with an abrupt apical curvature (angle of curvature of 90° and radius of curvature of 2 mm). The torsional resistance test was performed according to ISO 3630-1 specifications. To determine surface topography of the unused and used instruments, mesial root canals of mandibular molars with an abrupt apical curvature were selected to prepare a glide path with either the ProGlider or R-Pilot instrument. An optical profilometer and scanning electron microscopy were used to determine the surface properties. Normally distributed torsional and cyclic resistance data were analyzed using the Student t test, whereas quantitative data obtained by the optical profilometer were analyzed with the Kruskal-Wallis H test with a 5% significance threshold. ResultsThe R-Pilot showed significantly higher cyclic fatigue and torsional resistance than the ProGlider (P < .05). Angular deflection values were similar between instruments (P < .05). Measurements made from the blade area showed that the surface roughness values of the ProGlider were larger. Cutting blade measurements showed that unused instruments had significantly greater roughness values than used ones (P < .05). Although there was a 14% increase between the blade edge radii of the used and unused R-Pilot instruments, this difference was determined as 61% in ProGlider instruments. ConclusionsThe R-Pilot exhibited greater cyclic fatigue strength than the ProGlider when tested in an artificial canal with an inner diameter of 1.0 mm and an abrupt apical curvature. Torsional resistance of the R-Pilot was higher than the ProGlider, but the angular deflection values were similar. Glide path preparation in a mesial root canal with an abrupt apical curvature did not increase the surface roughness of both instruments but resulted in a greater blade edge radius.

Geometric Analysis of the Distolingual Root and Canal in Mandibular First Molars: A Micro–computed Tomographic Study

IntroductionThe purpose of this study was to comprehensively assess by micro–computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population. MethodsOne hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature. ResultsAll DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion. ConclusionsThe novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.

CLEANING EFFICIENCY OF XP ENDOFINISHER R VERSUS SONIC IRRIGATION AFTER RETREATMENT (S.E.M IN VITRO STUDY)

Introduction: Non-surgical endodontic treatment is the best way to re-establish sound periapical tissues after reinfection or inefficient treatment of a previously obturated teeth due to apical or coronal leakage. It requires regaining the accessibility to the root canal system by removing the initial root canal filling, more cleaning, and reobturation. The aim of the study: Is to compare the cleaning productivity of the XP Endo Finisher R (XPR) and the Endo Activator (EA) after retreatment using the scanning electron microscope (SEM). Material and Methods: This study was performed on forty-five mesiobuccal canals of mandibular first molars. All teeth were obturated then retreated using D-Race rotary files. Teeth were haphazardly divided into three groups according to the cleaning method used: Group (1): XPR. Group (2): EA. Group (3): control group (no final cleaning). All the teeth were sectioned longitudinally and canal cleaning ability was assessed by the SEM. Data were statistically analyzed using Chi-Square and Kruskal Wallis tests. Results: Significant differences in the smear layer and debris removal between both XPR and EA groups and the control group were detected (P<0.05). Conclusions: The XPR and the EA are both efficient in removing the debris and the smear layer after retreatment. Moreover, the XPR performed better than the EA. None of the investigated techniques were able to totally remove the filling material. Keywords: Retreatment, XP Endo Finisher R, Endo Activator, Scanning Electron Microscope. Running title: XPR versus EA after retreatment.

A comparative evaluation of the shaping ability of four different single-file systems in severely curved mesiobuccal root canals of mandibular first molars: An in vitro study

Aim: The aim of this study was to compare the shaping ability of four different single-file systems in severely curved mesiobuccal root canals in extracted human mandibular first molars.Materials and Methods: Sixty extracted intact human mandibular first molars with at least one curved mesial root were collected and used for the study. The study samples (n = 60) were divided into four experimental groups (n = 15 each): WaveOne (WO) (Group I), WaveOne Gold (WOG) (Group II), OneShape (Group III), and F360 (Group IV). The working length was established. All the study samples were prepared with respective file systems according to manufacturer's instructions. Pre- and postinstrumentation radiographs were taken and images were transferred to AutoCAD 2016 to determine the radius of curvature of each root canal. The canal curvature was assessed as a difference between before and after instrumentation to determine canal straightening. The data obtained were subjected to statistical analysis using SPSS version 20.0.Results: The pre- and postinstrumentation readings were compared using one-sample t-test, and difference was found to be statistically significant (P < 0.05). The mean difference in root curvature was estimated by pre- and postinstrumentation readings. According to mean change in the root curvature, the order determined was Group IV < III < II < I. Intergroup comparison was conducted using ANOVA statistical analysis, and it was found to be statistically significant.Conclusion: WOG and WO reciprocating files showed a marked tendency to straighten the severely curved canals, whereas F360 and OneShape continuous files maintained the original canal curvatures well.

Classification and morphology of middle mesial canals of mandibular first molars in a southern Chinese subpopulation: a cone-beam computed tomographic study

BackgroundCone-beam computed tomography (CBCT) was employed to study the morphology and curvature of middle mesial canals (MMCs) of mandibular first molars (MFMs).MethodsCBCT scanning was performed on MFMs of 1100 patients. Patients' images that met the inclusion criteria were divided into group A (< 40 years old) and group B (≥ 40 years old) for further study. The images were used to study the incidence of MMCs at different ages, measure the curvature of MMCs in the mesiodistal and buccolingual directions using the Schneider method, and observe the anatomical morphology of the mesial root canal system. All statistical analyses were performed by using SPSS 21.0 software. Quantitative data were presented as mean ± standard deviation. Student’s t-test was used to calculate the statistical significance. P < 0.05 was considered statistically significant.ResultsIn 875 patients, 1750 MFM images met the inclusion criteria. Among these cases, 158 MFMs contained an MMC, yielding an incidence rate of 9.03%. The incidence rate of MMCs was 11.22% in group A and 6.61% in group B, and this difference was statistically significant (P < 0.05). The curvature in the mesiodistal direction was 29.39 ± 8.53° in group A and 26.06 ± 8.50° in group B, and this difference was also significant (P < 0.05). The curved regions in groups A and B were often located in the middle 1/3 of canal. No significant difference in the distance between MMC orifices and mesiobuccal canal orifices or mesiolingual canal orifices was noted (P > 0.05). The most common mesial root canal morphological type was type II (3-2) (53.80%).ConclusionThe incidence of MMCs in MFMs declined as age increased. The canal systems of MMCs were varied and complex, mainly exhibiting an obvious mesiodistal curve. CBCT is an outstanding method to help guide root canal therapy.*Yeqing Yang and Buling Wu have contribute equally to this article.