MB1 Canals Research Articles

Shaping ability of HyFlex EDM and ProTaper Gold files with or without using glide path files: An in vitro study

Abstract Introduction: The necessity of using a glide path before the canal preparation is inconclusive. Therefore, this study aimed to assess the shaping ability of two rotary systems in the maxillary first molars’ first mesiobuccal canal (MB1), with or without employing the glide path files. Materials and Methods: The MB1 canals of 100 extracted molars were randomly prepared using either HyFlex EDM (HEDM) or ProTaper Gold (PTG) systems (n = 50 each). Half of the samples in each group were prepared using ProGlider (PG) or HyFlex EDM Glide (HEG). The cone-beam computed tomography scanning was conducted before and after the instrumentation. The canal transportation, centering ability, and remaining dentin thickness were evaluated and compared between the groups using the independent sample t-test and Mann–Whitney U-test (α =0.05). Results: Using HEDM compared to PTG led to greater centering ability at the sub-furcation area (P < 0.05), lower canal transportation at 2 mm below furcation (P = 0.025), and more dentin removed at the middle area (P = 0.011). The systems’ centering ability and canal transportation were comparable when path files were used. Utilizing HEG with HEDM decreased dentin removal at 2 mm below furcation (P = 0.045) and middle area (P = 0.008). Canal preparation with HEDM-HEG caused less dentin removal at 2 mm below furcation than PTG-PG (P = 0.007). Conclusions: The HEDM system outperformed PTG regarding centering ability in the sub-furcation areas and canal transportation 2 mm below the furcation. However, HEDM showed more dentin removal in the middle region than PTG, which was resolved when HEG was used. Therefore, using PathFile with the HEDM system might be suggested.

A Cone-Beam Computed Tomographic Analysis of Mesiobuccal Root Canals of Maxillary First Molars.

The maxillary first molar is crucial for proper bite formation and jaw positioning in adulthood. The prevalence of dental caries in the study's sample population suggests it is a common candidate for endodontic therapy. Multiple studies have shown that the canal and root morphology of the maxillary first molar are abnormal. The distobuccal and palatal roots of 286 maxillary first molars were removed at the furcation. The mesiobuccal roots were then imaged using cone-beam computed tomography (CBCT) on all specimens. The specimens were analyzed in comparison with one another. The following factors were studied. The number and arrangement of canals, as described by Vertucci; the presence or absence of an isthmus, as described by Kim; the canal curvature angle, as measured by the Schneider method; characteristics such as calcified segments, lateral canals, and an apical delta.For the flow analysis, CBCT was utilized to examine the root channel architecture of 286 mesiobuccal (MB) permanent maxillary first molar. Type I canal arrangement was found in 51.6% of teeth, Type II in 33.3%, Type III in 4.6%, Type IV in 4.2%, Type V in 2.5%, and Type VII in 1.5%. Type I, II, III, and V isthmus were each present in 26%, 6.7%, 9.5%, and 10.2% of the samples, respectively. Teeth with MB1 canal angulations of 0-20 degrees, 21-40 degrees, and more than 40 degrees were found in 56, 188, and 41 teeth, respectively. From 0 to 20 degrees, 21 to 40 degrees, and more than 40 degrees, 15 teeth, 88 teeth, and 25 teeth, respectively, had angulations in their MB2 canals. Only 9.8% of the samples had lateral canals, while 16.1% had both accessory canals and apical deltas. There were 19 cases with calcified segments in the coronal third of the MB1 canal and 13 cases in the middle third. There were no calcifications at the distal end of the MB1 canal. Thirteen of the specimens showed calcification only in the most caudal third of the MB2 canal, whereas the middle and distal thirds were uncalcified. Utilizing a noninvasive approach, a CBCT scan has the capacity to provide valuable insights into the root canal configuration.

Relationship between apical periodontitis and missed canals in mesio-buccal roots of maxillary molars: CBCT study

ObjectivesThe objectives of this study were to: (1) assess the frequency of missed canals in the mesiobuccal root (MB) of endodontically treated maxillary molars and its association with apical periodontitis (AP); (2) examine the correlation between the presence of a confluent or separate missed MB2 canal and the prevalence of AP; and (3) examine the correlation between the technical quality of endodontic treatment in the MB1 canal and the prevalence of AP. MethodsWe obtained and examined 800 cone-beam computed tomography (CBCT) scans from 800 patient records over 6 months. The parameters noted for each tooth included the tooth number; presence of missed canals in the MB root; configuration of missed MB2 canals (confluent or separate); technical acceptability of root canal treatment (RCT) of treated MB1 canals; and the CBCT periapical index score. Data were analyzed in SPSS version 24. ResultsA total of 203 maxillary molars from 148 CBCT scans were included. The MB2 canal prevalence was 88.2% in maxillary first molars and 62.7% in maxillary second molars. MB2 was found in 164 endodontically treated maxillary molars. During treatment, MB2 was missed in 150 (91.5%) and treated in 14 (8.5%) teeth. A total of 103 teeth (50.73%) had AP, which was observed in 67.3% of teeth with a missed MB2 canal but only 14.3% of teeth with a treated MB2 canal. The prevalence of AP was 43.7% in teeth with confluent MB2 canals and 80.9% in teeth with separate MB2 canals. ConclusionThe MB2 canal frequency was significantly higher in the examined maxillary first molars than the maxillary second molars. The MB2 canal was missed in most teeth that underwent endodontic treatment. The AP prevalence was relatively higher in endodontically treated maxillary molars with missed MB2 canals.

Location of the Second Mesiobuccal Canal of Maxillary Molars in a Brazilian Subpopulation: Analyzing Using Cone-beam Computed Tomography.

This study aimed to evaluate the spatial location of the second mesiobuccal canal (MB2) of maxillary molars (MMs), using cone-beam computed tomography (CBCT), in a Brazilian subpopulation. The CBCT examination of 250 patients performed on the Eagle 3D device was analyzed, totaling 787 MMs. Using the Radiant Dicom Viewer software, measurements were made of the distances, in millimeters (mm), between the first mesiobuccal canal (MB1), MB2, and palatal (P) canal inputs, from the axial sections. The Image J software evaluated the angle formed by the lines. The data obtained were analyzed statistically by Fisher's exact and Chi-square tests with a significance of 5%. The prevalence of MB2 canals observed was 76.44 and 41.73% in the first and second molars (1MMs and 2MMs), respectively (p < 0.05). The average of the distances and angles performed, for the location of the MB2 canals of the analyzed teeth, were MB1-P = 5.83 mm, MB1-MB2 = 2.31 mm, and MB2 for the intersection of the connecting distance from MB2-T = 0.90 mm. The average angle formed between the MB1-P and MB1-MB2 distances was 25.89° and 19.68° for the 1MMs and 2MMs, respectively. It was also observed that 91.4 and 75.4% of the maxillary 1MMs and 2MMs, respectively, presented the MB2 canals mesially located at the line connecting the MB1-P canals (p < 0.0001). The MB2 canals were located mesially to the MB1 canal with an average distance of 2 mm between the canals. The anatomical knowledge of the spatial location of the MB2 canal in different ethnicities is important for the planning and execution of endodontic treatment.

Can the detection of second mesiobuccal canals be enhanced based on the volume of adjacent canals?

ObjectivesThe purpose of this study was to evaluate whether the presence of the second mesiobuccal (MB2) canal is related to volumetric differences on the adjacent canals of maxillary molars. DesignForty-seven maxillary first and second molars with and without the MB2 canal were individually scanned using microcomputed tomography (micro-CT). The volume of each canal was measured by an evaluator with experience in micro-CT analysis. The intraclass correlation coefficient (ICC) was obtained. Multiple logistic regression and odds ratio was calculated. To compare the volume of canals in molars with and without MB2, the Mann-Whitney test was applied (α = 0.05). ResultsThe intra-examiner reproducibility was almost perfect (ICC=0.97). Multiple logistic regression demonstrated that the volume of the mesiobuccal (MB1) canal can possibly act as a predictor of the presence of the MB2 canal. It was also found that the MB1 canal volume is larger in molars without the MB2 canal (p = 0.01). No statistically significant difference was observed in the adjacent canals (p > 0.05). ConclusionsDespite the challenging detection of the presence of MB2 canals, clinicians should be aware that MB1 canals of reduced volume are highly suggestive of their presence.

Use of Biodentine in the resolution of a failure in paraendodontic surgery

To present a clinical case report of successful endodontic retreatment, in a maxillary first molar, with symptomatic apical periodontitis in the mesiobuccal root that had already undergone endodontic treatment and paraendodontic surgery. A patient was referred for evaluation of upper right first molar with swelling, severe pain and sensitivity to percussion and palpation. She reported having undergone endodontic treatment 1 year ago and, 6 months later, when the symptoms returned, a paraendodontic surgery was performed by the same professional. A cone-beam computed tomography (CBCT) was requested and the images showed extensive bone rarefaction associated with the mesiobuccal root, which had the MB1 canal treated and the MB2 canal untreated. The periapical region of the apices of the distobuccal and palatine roots showed signs of normality, and the treatment plan was established with selective endodontic retreatment only in the mesiobuccal root, with the location and treatment of the MB2 canal and retreatment of the MB1 canal. Retreatment was performed in 2 sessions with an intracanal dressing with calcium hydroxide paste. The canals were filled with Biodentine (BD, Septodont, Saint Maur de Fossés, France). Clinically, the patient had no further signs or symptoms and tomographic images showed evidence of bone repair after 24 months. Correct planning and execution of all phases of endodontic retreatment were fundamental for the success of this case report.

Morphological characteristics of the mesiobuccal root in the presence of a second mesiobuccal canal: a micro-CT study.

ObjectivesThis study investigated the internal morphology of mesiobuccal (MB) roots of maxillary molars with a second mesiobuccal (MB2) canal.Materials and MethodsForty-seven maxillary first or second molars from Brazilians were scanned using micro-computed tomography. The following measurements were obtained from the MB roots: root thickness, root width, and dentin thickness of the buccal aspect of the first mesiobuccal (MB1) canal, between the MB1 and MB2 canals, and the palatal aspect of the MB2 and MB1 canals at 3 mm from the root apex and in the furcation region. For statistical analysis, the Student’s t-test and analysis of variance with the post-hoc Tukey test were used (α = 0.05).ResultsIn maxillary molars with an MB2 canal, MB roots were significantly thicker (p = 0.0014) and narrower (p = 0.0016) than in maxillary molars without an MB2 canal. The dentin thickness of the palatal aspect of the MB1 canal was also significantly greater than that of MB roots without an MB2 canal at 3 mm from the root apex (p = 0.0007) and in the furcation region (p < 0.0001). In the furcation region of maxillary molars with an MB2 canal, the dentin thickness between the MB1 and MB2 canals was significantly smaller than that in the buccal and palatal aspects (p < 0.0001).ConclusionsThe internal morphology of MB roots of maxillary molars with an MB2 canal revealed differences in dentin thickness, root diameter, and distance between the canals when compared with maxillary molars without an MB2 canal.

Micro-CT evaluation of maxillary first molars: interorifice distances and internal anatomy of the mesiobuccal root.

This study aimed to describe the morphometric relationship of root canal orifices on the pulp floor in the presence/absence of mesiobuccal second canal (MB2) in the maxillary first molars and other aspects of its internal anatomy. Sixty-two maxillary first molars were scanned by micro-CT. The presence of the MB2 canal was verified. The distance between the center points of the MB1, MB2, distobuccal (DB), and palatal (P) canal orifices on the pulp floor were measured (MB1-MB2, MB1-DB, MB2-DB, MB1-P, and DB-P). The MB1-P to DB-P ratio was calculated. The distances between the anatomic apex and the MB1 and MB2 apical foramina were measured. The length of the band-shaped isthmus was also measured. Student's t-test was applied to verify the association between the presence of an MB2 canal, the interorifice distances, and the ratio of the MB1-P to DB-P distance (α = 5%). The MB2 canal was present in 43 roots (69.35%). Statistics showed significant differences when MB2 was present for the largest MB1-P distance (p < 0.05) and higher values for the MB1-P to DB-P ratio (p < 0.05). A band-shaped isthmus was detected in 25.8% of MB roots. The mean distance from the apical foramen to the isthmus floor ranged from 1.74 for MB1 canals to 1.42 for MB2 canals. Canal orifice distances on the pulp floor may predict the presence of MB2 canals. There was a high incidence of isthmus, accessory canals, and apical delta in the critical apical zone in MB roots of maxillary first molars.

Apical periodontitis of endodontically treated maxillary first molar: Cone-Beam Computed Tomography study

Objective: The purpose of this study was to analyze the Cone-beam computed tomograghy(CBCT) scan of endodontically treated maxillary first molars and investigate how second mesiobuccal (MB2) canal is treated, how the prognosis of mesiobuccal (MB) root is different compared to other roots and the prognosis factor on apical periodontitis. Methods: Subjects were endodontically treated maxillary first molars whose were collected from CBCT scans taken from January 2018 until December 2019. A total of 525 maxillary first molars were analyzed by an endodontist to determine the presence of the MB2 canal, the quality of the root canal filling, and the presence of apical periodontitis. The chi square test and Fisher's exact test was used to examine the relationship between each variable. Results: MB2 canals were found in 46.3%, of which 76.5% were not treated. The more main canal of mesiobuccal root (MB1 canal) was well filled, the more significantly MB2 canal was well filled (p&lt;0.001). The apical periodontitis of MB root was not related to the filling quality of MB1 canal (p=0.370) and was related to the filling quality of MB2 canal (p=0.004). The apical periodontitis of MB root was related to the quality of canal filling of MB2 canal and the apical periodontitis of DB and P root. Conclusions: It was found that the majority of MB2 canals were not treated. The apical periodontitis of MB root was analyzed to be related to the quality of canal filling of MB2 canal. The apical lesion of the MB root was not correlated with the treatment of the MB1 canal, but it was significantly related to the quality of filling of MB2 canal.

Precision of Dynamic Navigation to Perform Endodontic Ultraconservative Access Cavities: A Preliminary In Vitro Analysis

IntroductionUltraconservative access cavities (UCACs) have been proposed to reduce crown weakening, but there is no consensus about their design and size and about their advantages and disadvantages, which are also related to how differently they are performed. The purpose of the present study was to evaluate the possible use of a novel Dynamic Navigation System (DNS) in planning and executing UCACs and its precision in vitro, compared with a manual approach (MA) without any guide. MethodsTwenty radiopaque, artificial teeth replicas were randomly divided into 2 identical groups and scanned using cone-beam computed tomography. In the first group (MA) MB1 canal orifice was reached, starting from the central part of the molar occlusal surface, using a micro endodontic bur. In the second group, DNS allowed to plan and execute a more direct, straight-line truss access. After cavity preparation, teeth were scanned again, and cone-beam computed tomography images were compared. Data were statistically analyzed with analysis of variance test. ResultsSignificant differences (P < .05) were found in the tested parameters between the 2 groups. The DNS group was significantly more precise, showing smaller mean values in the angulation (4.8°) and in the maximum distance from the ideal position (0.34 mm), when compared with MA group (mean values, 21.2° and 0.88 mm, respectively). ConclusionsHence, we may conclude that the use of DNS increased the benefits of UCACs by minimizing the potential risk of iatrogenic weakening of critical portions of the crown and reducing negative influences to shaping procedures.

The MB3 canal in maxillary molars: a micro-CT study.

To assess the internal and external morphologies of the mesiobuccal (MB) root of maxillary molars presenting a third root canal (MB3), using micro-computed tomography (micro-CT). Two-hundred and sixty-five extracted maxillary first and second molars with different root configurations were imaged in a micro-CT scanner at 19.6-μm pixel size. Sixteen teeth presenting MB3 canal were selected and evaluated regarding root configuration, minimal dentine thickness 2mm under the furcation area, canal configuration of the MB root, MB3 canal morphology (location, independent or confluent orifice, and anatomy types), and the apical anatomy (aspect ratio, number of accessory canals and foramina, presence of isthmus, and independent MB3 foramen). Overall, a high variability in canal configuration was detected in the MB root. MB3 canal was observed in 10 maxillary first molars and 6 maxillary second molars (n = 16). Minimal dentine thickness related to the MB3 canal at the coronal third was smaller than that of the MB1 canal. A complex internal anatomy comprising 13 different root canal configurations was observed. A high number of independent MB3 orifices at the pulp chamber floor was observed in the first molars (7 out of 10 teeth), while most of the specimens (n = 14) showed a confluent anatomy of the MB3 canal. A varied number of accessory canals and foramina were observed. At the apical third, isthmus could be observed in 6 specimens, while an independent MB3 foramen was present in 37.5% of the MB roots. MB3 canal is a rare anatomical variation present in maxillary first and second molars. Its presence can be associated to a complex internal anatomy of the MB root which includes the presence of isthmuses and multiple accessory canals and foramina at the apical third, but also a thin dentine thickness at the coronal third and a confluent anatomy of the MB3 with the other main canals.

The second mesiobuccal canal in three-rooted maxillary first molar of Karnataka Indian sub-populations: A cone-beam computed tomography study

IntroductionElusive second mesiobuccal canal (MB2) in maxillary first molar are often missed during endodontic therapy and are a major cause of treatment failures. Its prevalence is known to vary among different populations and there is limited information on its prevalence in Indian population. AimThis study investigated the prevalence and location of second mesiobuccal (MB2) canal in mesiobuccal root of maxillary first molar using cone beam computed tomography (CBCT) images in an Indian population. Materials and methodsCBCT images of 598 three rooted maxillary first molars were studied. In each CBCT image, the floor of pulp chamber was located and advanced by 2 mm to standardize the observation for MB2 canal. Its location was determined in relation to mesiobuccal (MB1) and palatal (P) canal. Statistical analysisThe data was analysed using descriptive statistics. The presence of MB2 canal was correlated with age, gender and tooth position using Chi square test. ResultsThe prevalence of MB2 canal in three rooted maxillary first molar was 61.9%. It was seen that the prevalence of MB2 was highest in 20–40years age group (67.4%) followed by > 40 years (57.5%) and lowest in <20 years (50.6%) and the difference was statistically significant (p = 0.005). It is located mesiopalatally; 2.5 mm ± 0.6 mm palatally and 1.0 ± 0.4mmmesially to the MB1 canal or present directly on the line joining the MB1 and palatal canal. ConclusionThere is a high probability of finding MB2 canal in Indian patients. The access cavity must be modified from a triangular shape to rhomboid shape. Troughingmesiopaltally (about 2.5 mm palatally and 1 mm mesially) from MB1 to a depth of about 2 mm from the floor of pulp chamber may be necessary for locating MB2 canal.

Micro-CT analysis of danger zone thickness in the mesiobuccal roots of maxillary first molars.

To evaluate dentine thickness from both distal ('danger zone') and mesial ('safety zone') aspects of the MB1 and MB2 canals of maxillary first molars at the furcation level using micro-CT imaging. One hundred maxillary first molars with two canals in the MB root were selected from a Brazilian subpopulation and scanned at a resolution of 19.6μm in a micro-CT device. From each specimen, two axial cross-sectioned images were selected at 2 and 3mm apical to the furcation level of the MB root and evaluated for the smallest dentinal thickness. Measurements were made from the outer perimeter of the MB1 and MB2 canals towards the external root surface from both distal (danger zone) and mesial (safety zone) aspects of the root. The influence of an isthmus was also considered in the analysis, and samples were classified according to the presence or absence of an isthmus in the axial sections. Non-parametric Wilcoxon signed-rank tests were used to compare dentinal thickness between MB1 and MB2 canals with a significant level set at 5%. Colour-coded 3D models of dentine thickness throughout the MB root were created and evaluated qualitatively. At both levels, median dentine thickness of the MB2 canal was significantly lower in both distal and mesial aspects of the root in comparison with the MB1 canal (P<0.01). The presence of an isthmus was not a variable that influenced dentinal thickness. Colour-coded models indicated that dentine thickness was dependent on the cross-sectional shape of the MB root. At least 50% of the sample had <1mm of dentine thickness at the danger zone of the MB2 canal. Danger zones in the MB roots of maxillary first molars were not symmetrical. MB2 canals had less dentine thickness on both aspects of the root compared to the MB1 canal.

The ability of Reciproc instruments to reach full working length without glide path preparation: a clinical retrospective study.

BackgroundReciproc instruments are the only contemporary root canal instruments where glide path preparation is no longer strictly demanded by the manufacturer. As the complete preparation of root canals is associated with success in endodontic treatment we wanted to assess the ability and find predictors for Reciproc instruments to reach full working length (RFWL) in root canals of maxillary molars in primary root canal treatment (1°RCTx) and retreatment (2°RCTx) cases.MethodsThis retrospective study evaluated 255 endodontic treatment cases of maxillary molars. 180 were 1°RCTx and 75 2°RCTx. All root canals were prepared with Reciproc instruments. The groups were compared and in a binary logistic regression model predictors for RFWL were evaluated.ResultsA total of 926 root canals were treated with Reciproc without glide path preparation. This was possible in 885 canals (95.6%). In 1°RCTx cases 625 of 649 (96.3%) canals were RFWL and in 2°RCTx cases 260 of 277 (93.9%). In second and third mesiobuccal canals (MB2/3) 90 out of 101 (89.1%) were RFWL with Reciproc in 1°RCTx and in the 2°RCTx treatment group 49 out of 51 cases (96.1%). In mesio-buccal (MB1) canals “2°RCTx” was identified as negative predictor for RFWL (OR 0.24 (CI [0.08–0.77])). In MB2/3 canals full working length was reached less often (OR 0.04 (CI [0.01–0.31])) if the tooth was constricted and more often if MB2/3 and MB1 canals were convergent (OR 4.60 (CI [1.07–19.61])).DiscussionUsing Reciproc instruments, the vast majority of root canals in primary treatment and retreatment cases can be prepared without glide path preparation.

CBCT for the assessment of second mesiobuccal (MB2) canals in maxillary molar teeth: effect of voxel size and presence of root filling

To compare detection of the second mesiobuccal (MB2) canal in maxillary molar teeth using cone-beam computed tomography (CBCT) with different voxel sizes against conventional radiographic examination when the MB1 was unprepared, prepared and filled. Radiographic examination and 0.2-, 0.25- and 0.3-mm CBCT (n=89) were performed in 3 stages: S1, no first mesiobuccal (MB1) canal preparation or filling; S2, after MB1 preparation and filling; and S3, after MB1 root canal filling removal and canal repreparation. Images were analysed using the i-Cat software. After RE and CBCT acquisition in S3, all the samples were clarified to directly visualize the presence of the MB2 canal. All images were analysed by a blinded, previously calibrated examiner. Accuracy, specificity and sensitivity were compared using analysis of variance (P<0.05 level of significance). MB2 root canals were detected in 67% of the samples. Overall, radiographic examination was associated with lower mean accuracy values for detecting MB2 than CBCT regardless of the MB1 condition. The MB1 root canal condition did not influence MB2 detection in 0.2-mm voxel images. The presence of root fillings in the MB1 canals reduced the detection of MB2 canals, especially in the 0.3- and 0.25-mm voxel-size images (P<0.05). CBCT was associated with higher mean values of specificity and sensibility than radiographic examination for the detection of MB2 canals. When endodontic retreatment is necessary removal of the root filling prior to the CBCT examination eliminates artefacts, thereby permitting the use of the 0.3-mm voxel protocol that has good diagnostic performance and lower radiation dose.

Microcomputed tomography analysis of mesiobuccal orifices and major apical foramen in first maxillary molars.

Objective:Aim of the study was to determined by microcomputed tomography (µCT) the horizontal distance between the main (MB1) and the second mesiobuccal canal (MB2) orifices, the vertical distance between the MB1 and MB2 orifices planes, and the distance between the anatomic apex and major apical foramen (AF). Furthermore, we characterized the entire internal and external anatomy of the MB, distalbuccal (DB) and palatal (P) maxillary first molars roots.Materials and Methods: Twenty-two intact extracted first maxillary molars were scanned by X-ray computed transaxial µCT and then 2D and 3D images were processed and analyzed.Results:The results showed that 77.27% of the mesiobuccal (MB) roots presented a second MB canal, and 29.41% of the MB2 were independent from the MB1 canals. In 15 teeth, there were three root canal orifices on the chamber floor, and 10 of these teeth presented MB2 canals. The mean vertical distance between the MB1 and MB2 planes was 1.68 ± 0.83 mm. Seven teeth had four orifices. The mean horizontal interorificial distance between the MB1 and MB2 orifices was 1.21 ± 0.5 mm. Accessory canals were observed in 33.33% of the roots, loops in 6.06%, while isthmuses were found in 15 of the 22 MB roots. Of the total roots, 74.24% presented one foramen, while all of the roots showed a major apical foramen that was not coincident with the anatomic apex. Conclusions:Our µCT analysis provided interesting features on the horizontal and vertical distance between the MB1 and MB2 orifices and on the distance of AF and anatomic apex.Clinical Relevance:These results have an important clinical value because might support the endodontist in the recruitment, negotiation and obturation of maxillary first molar canal system.

Morphological characteristics of mesiobuccal root canals of the first maxillary molars

The first maxillary molar is a tooth with three roots, and mesiobuccal one is with the most complex canal morphology. Factors influencing variations of its morphology are numerous, and may significantly complicate endodontic treatment. The objective was to investigate the number, configuration and curvature orientation of the mesiobuccal root canals in the maxillary first molars. The study was conducted on 200 mesiobuccal (MB) roots of extracted first molars in human subjects using radiography. In each canal Flexofile was introduced until reaching the apical foramen and the root was then radiographed in series from two projections. Number of root canals (MB1, MB2 and MB3), configuration according to Vertucci classification, and the orientation of the curvature were established. Relevant statistical parameters and the significance of differences were computed (p < 0.05). Of total 200 mesiobuccal roots 86.5% were with two, 9% with three, and 4.5% with a single canal. Most frequent configurations were type IV (36%) and II (34.5%). From the clinical projection all MB, canals were oriented distally, from the proximal 78% palatally and 22% buccally. The orientation of all MB2 canals was distal from the clinical projection, from the proximal projection 76% were oriented palatally, and 24% buccally. The MB3 canal was always oriented distally from the clinical projection, and buccally from the proximal aspect. The mesiobuccal roots of the first maxillary molars showed multiple canals in 96%, with dominant Vertucci type II and IV of configuration. All canals were curved.

Root canal morphology of the mesiobuccal root of maxillary first molars: a micro‐computed tomographic analysis

To investigate ex vivo, the root canal morphology of the MB root of maxillary first molar teeth by means of micro-computed tomography. Thirty extracted intact human maxillary first molar teeth were selected for micro-tomographic analysis (SkyScan 1072, Aartselaar, Belgium) with a slice thickness of 38.0 mum. The following data regarding the MB root were analysed and recorded: number and type of root canals, prevalence of isthmuses, prevalence of intercanal connections, presence of accessory canals, presence of loops and number of apical foramina. The MB2 canal was present in 80% of specimens and was independent in 42% of these cases. When present, the MB2 canal merged with the MB1 canal in 58% of cases. Communications between the two canals were found in all specimens, with isthmuses in 71% of the cases. These communications and isthmuses were respectively in 42% and 54% of the cases in the coronal third, in 59% and 79% of the cases in the middle third and in 24% and 50% of the cases in the apical third. A single apical foramen was found in 37% of specimens, two apical foramina were present in 23% of the cases, with three or more separate apical foramina occurring in 40% of the specimens. The MB root canal anatomy was complex: a high incidence of MB2 root canals, isthmuses, accessory canals, apical delta and loops was found.

Detection of the second mesiobuccal canal in mesiobuccal roots of maxillary molar teeth ex vivo

To assess the effectiveness of magnification and dentine removal (troughing) when locating the second mesiobuccal canal in mesiobuccal roots of maxillary molars. A total of 208 extracted human maxillary molars were examined. After crown and pulp removal, the MB1 and 2 canals in the mesiobuccal root were located in three stages that were performed by two undergraduate dental students. Stage 1: canals were located with an endodontic explorer; stage 2: additional canals in the same teeth were located under magnification with a digital microscope (VH-8000, Keyence, Japan); stage 3: additional canals in the same teeth were located by removing dentine (troughing) from the pulp chamber floor within 3 mm from MB1 canal towards the palatal canal with an Enac ultrasonic tip (ST 21, Osada, Japan). In each group, the canals were prepared with Gates Glidden burs and K-files. The distal and palatal roots were then removed, and Indian ink was injected into the canal system within the mesio-buccal root. The root surfaces were washed with 6% NaOCl, and then rendered transparent to observe canal morphology. The root canal configurations were classified into five categories following the modified Weine's classification. More than one canal in the mesio-buccal root was observed in 48% of specimens. Detection rates of multiple canals were 7, 18 and 42% following stages 1, 2 and 3, respectively. There was a significant difference between the stages for detecting the MB2 canal (P < 0.05, Friedman test). Both magnification (stage 2) and dentine removal under magnification (stage 3) were effective in detecting the presence of the MB2 canal. However, MB2 canals could not be detected in 13% of the teeth because of canal calcification or branching located more apically.