Morphology of Mandibular First Molars Analyzed by Cone-beam Computed Tomography in a Korean Population: Variations in the Number of Roots and Canals

Influence of root shape on canal complexity at the mandibular molar apical surgical resection level: A micro-CT study

OBJECTIVES

This study aimed to investigate the relationship between the aspect ratios of mandibular molar roots at the apical 3-mm level and their root canal complexity.

DESIGN

This study used micro-CT imaging to analyze 163 two-rooted mandibular molars. The aspect ratios of the roots at the apical 3-mm level were categorized as "< 2.75" or "≥ 2.75" (mesial) and "< 1.75" or "≥ 1.75" (distal). A two-dimensional (2D) analysis focused on four apical axial cross-section levels to determine the presence of main and accessory canals and isthmus. Additionally, a three-dimensional (3D) assessment of the apical 4-mm of both roots examined main and accessory canals, apical foramina, apical deltas, and middle mesial canals.

RESULTS

Mesial roots with aspect ratios ≥ 2.75 showed a higher number of main canals at all levels compared to those with aspect ratios < 2.75 at the 3-mm level. Additionally, the ≥ 2.75 group exhibited more accessory canals and a higher average number of accessory canals. The 3D assessment confirmed significantly more accessory canals and apical foramina in the ≥ 2.75 group. The prevalence of roots with apical deltas was nearly double in the ≥ 2.75 group, and middle mesial canals were exclusively found in this group. In the distal root, the ≥ 1.75 group showed a significantly higher number of main canals at all axial levels. No significant differences were observed between groups in terms of accessory canals, apical foramina, or deltas.

CONCLUSIONS

A higher root aspect ratio is related to higher anatomical complexity.

Cone-beam computed tomographic analysis of canal convolution in mesial root of mandibular second molars and a proposed new classification

Aim

The aim is to evaluate the anatomical characteristics of mesiolingual and mesiobuccal canals in mandibular second molars particularly in terms of its exit direction, distance of confluence from the minor constriction, and the angle of confluence.

Materials and Methods

The cone-beam computed tomography images of hundred mandibular second molars were analyzed. Endodontically treated teeth and those with anatomical variations such as C-shaped canal configuration were excluded from this study. The distance of the confluence from the minor constriction, angle of confluence, and the exit direction of the mesiobuccal and the mesiolingual canals were assessed. Data were analyzed using an independent t-test.

Results

The course of the mesiobuccal and mesiolingual canals beyond the confluence was towards the center of the root. The average angle of confluence was 32.75°-35.28°. The average distance of confluence from the minor constriction was 2.19 to 2.68 mm. The mesiolingual canal was straighter whereas the mesiobuccal canal had a tortuous course. Considering the results of the present study, a new classification has been proposed for the root canal morphology of the mesial root of mandibular second molars.

Conclusion

The variation in the morphology of mandibular second molars highlights that the mesiolingual canal presented a mild curvature through and beyond the confluence when compared to the mesiobuccal canal which exhibited a tortuous course through the confluence.

The effect of cone beam computerized tomography voxel size and the presence of root filling on the assessment of middle mesial canals in mandibular molar teeth

INTRODUCTION

The study aims to compare the detection of the middle mesial canal (MMC) in mandibular molar teeth using cone beam computed tomography (CBCT) with different voxel sizes when the mesiobuccal (MB) and mesiolingual (ML) canals have three distinct phases (unpreparation, preparation and obturation and the removal of the obturation and repreparation).

METHODS

Two hundred forty-two extracted human mandibular molars were collected and kept in a physiological saline solution prior to use. 0.2-, 0.28- and 0.35-mm voxel sizes CBCT (n = 242) were performed in three phases (Ph): Ph1, no MB and ML canal preparation or obturation; Ph2, after MB and ML canals preparation and obturation; and Ph3, after the removal of the obturation of MB and ML canals and canals repreparation. Images were analyzed using OnDemand3D® software. After the CBCT acquisition in Ph3, all the samples were clarified to visualize the presence of the MMC directly. A blinded, previously calibrated examiner analyzed all the images.

RESULTS

The MMC was detected in 15 of the 242 teeth after the clearing technique. The lowest MMC detection rate was observed at 0.35-mm voxel size regardless of the ML and MB canal condition, while the highest was observed at 0.2-mm voxel size (P < 0.05). There is no statistically significant difference between 0.2-mm and 0.28-mm voxel sizes (P > 0.05). In all voxel sizes, the highest rate of detectability of the MMC was seen in Phase 1, while the lowest was in Phase 2.

CONCLUSIONS

It may be appropriate to take a 0.20-mm voxel size CBCT image, especially after the removal of root canal filling.

CLINICAL RELEVANCE

An appropriate CBCT voxel size and the absence of root canal filling in the root canal system help to detect the missing MMC.

A systematic review and meta-analysis of the prevalence and global distribution of middle mesial canals in mandibular molars identified by CBCT

OBJECTIVES

This systematic review and meta-analysis aimed to evaluate the prevalence of middle mesial canal (MMC) in permanent mandibular molars of different populations and regions based on cone-beam computed tomography (CBCT) studies.

MATERIALS AND METHODS

PubMed, Scopus, Embase, Web of Science, and Open-Grey were searched up to October 2023 according to specific keywords. A hand search was conducted on the references of the included studies and articles from three peer-reviewed journals in endodontics. The main variable of interest was the prevalence of MMC. Additional data such as the total number of included cases, age and country of the population, CBCT device information, voxel size, and field of view details were also extracted. Extracted data were analyzed qualitatively with the JBI quality assessment checklist and quantitatively with STATA software.

RESULTS

Of 32,793 studied teeth, the cumulative prevalence of MMC in both mandibular 1st and 2nd molars was 3.11% (95% CI: 2.00-4.44%). The subgroup analysis reveals a prevalence of 4.15% (95% CI: 2.69-5.89%) for mandibular 1st molars and 1.2% (95% CI: 0.2-2.83%) for mandibular 2nd molars. The highest prevalence of MMC in 1st molar was attributed to South Asia (11.24%) and Africa (6.61%).

CONCLUSIONS

The prevalence of MMC varies among regions. Clinicians should be aware of the potential prevalence of MMC, particularly in mandibular first molars, as a missed MMC could result in endodontic failure.

CLINICAL RELEVANCE

The presence of MMCs varies in different geographic regions (0% to 29.7%). Clinicians should always look for MMC when doing an endodontic treatment on mandibular molars, as the presence of this canal is not uncommon. We suggest searching for this canal as if searching for the second mesiobuccal canal of maxillary 1st molars.

Prevalence and anatomic associations of middle mesial canals and isthmi in mandibular first molars: A CBCT-based study in a Northern Chinese population

This study investigated the prevalence of the middle mesial canal (MMC) and isthmus in a northern Chinese subpopulation using cone-beam computed tomography (CBCT). CBCT images of 1060 mandibular first molars (MFMs) were analysed. Data analysis was performed using the chi-square test, t-test, and multiple logistic regression analysis (p < 0.05). The prevalence of MMC and isthmus was 15.2% and 40.6%, respectively. The average dentinal thickness in the danger zone was 1.61 ± 0.14 mm. Patients younger than 40 years were two times more likely to have MMC (odds ratio [OR] = 2.204). Additionally, for every 1 mm reduction in the MB-ML orifice distance, the likelihood of detection of MMC in MFM nearly doubled (OR = 1.738). Furthermore, MFMs with MB-ML isthmus were five times more likely to exhibit MMC than those without it (OR = 4.756). The findings revealed that the prevalence of MMC and isthmus in MFMs is high and suggested that anatomical and demographic variables can serve as valuable indicators for clinicians in anticipating their presence.

Microcomputed tomography (micro-CT) analysis of apical mandibular premolar in relation to clinical sign presentation: An in vitro study

Introduction

Variations in anatomic apex and apical foramina of root canals are common in different teeth types. The sophisticated 3D micro-CT aids researchers in investigating the apical morphology, such as the apical foramen (AF) and constriction (AC).

Objectives

To measure the length between the foramen and the apex and the physiological length to the apex, in lower premolar teeth. Furthermore, a measurement was conducted on the average length from the foramen to the apex of the lower premolar teeth with respect to the presence of clinical and non-clinical signs.

Methods

A total of 80 lower premolar teeth were selected based on the inclusion criteria. All samples were scanned using micro-CT ZEISS X-Radia (17 µm), and the datasets were analysed. The root canal AF and AC were reconstructed using Drishti software (V3.0) by utilising a 4-digit system code in millimetres (mm).

Results

More than half of the lower premolars (n = 47, 58.8 %) demonstrated a clinical signs presentation, while the rest had a non-clinical sign (n = 33, 41.3 %). There was a significant difference (p = 0.013) between the non-clinical and clinical groups in the mean length from the apical foramen to the apex (AFA) at 0.59 mm and 0.47 mm, respectively. Meanwhile, the non-clinical and clinical mean length from apical constriction to apex (ACA) were 0.75 mm and 0.73 mm, and the mean length from AF to AC (AFC) was 0.48 mm and 0.53 mm, respectively. Nonetheless, no significant differences were detected between the ACA and AFC of non-clinical and clinical groups.

Conclusion

The clinical signs presentation observed in lower premolars mainly affected the apical morphology, particularly the position and length of the root AF, and less so the AC position and length. Therefore, the information is useful for clinical purposes.

Radix entomolaris and radix paramolaris: A cone-beam computed tomography study of permanent mandibular molars in a large sample from Slovenia

OBJECTIVES

To investigate the prevalence, unilateral/bilateral concurrency, and external morphology of permanent mandibular molars (PMMs) with radix entomolaris (RE) and radix paramolaris (RP) in a sample from Slovenia.

DESIGN

Medium field-of-view cone-beam computed tomography images of 1315 participants (681 males, 634 females) aged 13-90 years (mean age 45.5) were retrospectively examined. A total of 1363 first, 1824 second, and 1314 third PMMs were evaluated. The external morphology of the affected teeth was categorized according to Carlsen and Alexandersen's classifications.

RESULTS

The individual-level RE frequencies in the first, second, and third PMMs were 1.6%, 1.9%, and 10.1%, respectively. The respective RP frequencies were 0%, 1.8%, and 3.2%. The first PMMs exclusively exhibited type A RE morphology, whereas in the second and third PMMs, types B and AC morphologies predominated. Bilateral concurrence rates were low (0-7.1%), with the exception of type A RE in first PMMs (62.5%). RE occurrences in the first and second PMMs were correlated (odds ratio = 70.2; 95% confidence interval 17.4 -282.7; P < 0.001). In concurrent cases, the second PMM followed its anterior neighbor in expressing type A morphology, and conversely, all affected second PMMs standing next to a two-rooted first PMM exhibited non-type A morphology.

CONCLUSIONS

In this sample, the first and second PMMs exhibited low supernumerary root frequencies comparable to those of other European samples. The third PMM was most often affected. The presence of RE on the first PMM increased the possibility of its presence on the adjacent second PMM and vice versa.

A Cone Beam Computed Tomography-Based Investigation of the Frequency and Pattern of Radix Entomolaris in the Saudi Arabian Population

Background and Objectives: An understanding of the anatomical complexity of teeth is a significant factor for a successful endodontic treatment outcome. The aim of this study was to explore the frequency and pattern of distribution of radix entomolaris (RE) in mandibular first molars (MFMs) of a Saudi Arabian subpopulation using CBCT scans. Materials and Methods: This study was conducted at dental clinics of Qassim University from February to May 2023 by evaluating CBCT scans that were previously obtained for diagnostic purposes. Scans of Saudi national patients with bilaterally present MFMs and fully formed root apices were included. Conversely, scans with one/or two missing MFMs, MFMs with incomplete root apices, full- or partial-coverage prosthesis, endodontic treatment, and associated radicular resorption were excluded from study. A total of 303 CBCT scans with 606 bilateral MFMs were analyzed by two calibrated evaluators for the presence of, and type according to Song's typolgy of RE. The data were analyzed using SPPS-24. The descriptive variables were documented as frequencies and percentages. The chi-square test was used to determine the association between the prevalence of RE with the gender, jaw side and age group. Both inter-rater and intra-rater agreements were estimated for detecting and classifying RE using Cohen's kappa test. Results: The sample had 63.7% males and 36.3% females. The prevalence of RE was 6.6%, with Song's type III (57.5%) as the most common variant. Absolute agreement was noted between the raters about the presence of RE and very strong agreement was noted for the classification of the RE. Conclusions: RE is an uncommon finding among the mandibular first molars of the Saudi population without any gender and quadrant predilection. The clinicians' knowledge of the presence and Song's type of RE may contribute towards the enhancement of endodontic treatment outcomes.

Prevalence of Middle Mesial Canal in Mandibular Molars of a Saudi Subpopulation: A Prospective Cone-Beam Computed Tomography Study

BACKGROUND

Root canal treatment is compromised when one or more root canals are left unmanaged, especially in the case of multirooted teeth. Cone-beam computed tomography (CBCT) has the advantage of clearly recognizing the anatomical structures without any blurring and superimposition. There are few studies that assess the middle mesial canal (MMC) prevalence in the Saudi population using CBCT imaging. Thus, the present study was conducted to assess the MMC prevalence in the first and second mandibular molars in the Saudi population using CBCT imaging.

MATERIALS AND METHODS

Data from 616 patients and 1014 teeth were assessed. The mesial roots of the mandibular first and second molars were examined using CBCT to assess the presence of the MMC in both axial and coronal sections. The potential correlation between the prevalence of MMC was assessed with gender and age. The data collected were subjected to statistical analysis using IBM SPSS version 20.0 software (IBM Corp., Armonk, NY).

RESULTS

The mean age was 34.39 ± 12.12 years, showing male predominance. A total of 2.6% and 0.2% cases of MMC were found in the first and second molars, respectively. A significant difference (p-value < 0.05) was observed among both genders in relation to age groups and the presence of MMC. MMC in the first molar was seen mainly in patients aged <20 years and only one case was reported with MMC in the second molar among patients aged 41-60 years.

CONCLUSION

A higher incidence of MMC was found in the first than the second mandibular molar. For accessing the MMC, the patient's age, high magnification, and troughing are some influential factors. In the future, clinical studies with long-term follow-ups are required to assess the influence of biomechanical preparation of MMC on the result of nonsurgical endodontic management in mandibular first as well as second molars.

Assessment of the Prevalence of Radix Entomolaris and Distolingual Canal in Mandibular First Molars in 15 Countries: A Multinational Cross-sectional Study with Meta-analysis

AIM

The aim of this study was two-folded: i) to assess the prevalence of Distolingual Canal (DLC) and Radix Entomolaris (RE) in Mandibular First Molars (M1Ms), using Cone Beam Computed Tomography (CBCT) images and ii) to assess the impact of sociodemographic factors on the prevalence of these conditions worldwide.

METHODS

CBCT images were scanned retrospectively and the ones including bilateral M1Ms were included in the study. The evaluation was performed by 1 researcher in each country, trained with CBCT technology. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating axial sections from coronal to apical. The presence of DLC and RE in M1Ms (yes/no) was identified and recorded.

RESULTS

Six thousand three hundred four CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries regarding the prevalence of both RE and DLC (P < .05). The prevalence of DLC ranged from 3% to 50%, and the overall prevalence was 22% (95% CI: 15%-29%). RE prevalence ranged from 0% to 12%, and the overall prevalence was 3% (95% CI: 2%-5%). There were no significant differences between left and right M1Ms or between genders for either DLC or RE (P > .05).

CONCLUSION

The overall prevalence of RE and DLC in M1Ms was 3% and 22%. Additionally, both RE and DLC showed substantial bilaterally. These variations should be considered by endodontic clinicians during endodontic procedures in order to avoid potential complications.

The global prevalence of middle mesial canal in mandibular first and second molars assessed by cone beam computed tomography: A systematic review and meta-analysis

BACKGROUND

This meta-analysis sought to identify the in vivo prevalence and influencing factors of middle mesial canal (MMC) in mandibular first and second molars based on cone-beam computed tomography (CBCT) scans.

METHODS

MEDLINE/PubMed, Web of Science, Scopus, SciELO, Google Scholar databases/search engines were searched in period between 15^th and 21^st November 2022, to retrieve the in vivo CBCT-based studies that assessed the prevalence of MMC in mandibular first and/or second molars. The studies were strictly assessed using pre-defined inclusion and exclusion criteria for relevancy and eligibility through screening the title and abstract, and then assessed through reading the full texts using the same criteria. Subsequently, the fulfilled studies were assessed qualitatively using the Newcastle-Ottawa Quality Assessment Scale, and quantitatively using meta-analysis to calculate the pooled prevalence rates of MMC. The publication bias was assessed using funnel plot and Egger's test.

RESULTS

Out of 1,122 studies, 33 studies comprised 13,349 and 7,624 mandibular first and second molars, respectively, were eligible for inclusion. Twenty studies scored high quality, while thirteen scored moderate quality. The global prevalence of MMC in the first molar was 4.4% (95% CI = 0.035-0.053, P<0.001), significantly higher than that of the second molar which was 1.3% (95%, CI = 0.008-0.018, P<0.001). Gender, molar side, and age were not influencing factors of MMC prevalence.

CONCLUSION

The prevalence of MMC is not uncommon, being higher in the mandibular first molar compared to the mandibular second molar. The prevalence of MMC is not influenced by age, molar's side, and gender.

Assessment of the Prevalence of Middle Mesial Canal in Mandibular First Molar: A Multinational Cross-sectional Study with Meta-analysis

BACKGROUND

An additional canal found in the mandibular first molar (M1M) is the middle mesial canal (MMC), which is often missed during root canal treatment. In this study, the prevalence of MMC in M1M on cone-beam computed tomography (CBCT) images was evaluated in 15 countries, along with the effect of some demographic factors on its prevalence.

METHODS

Deidentified CBCT images were scanned retrospectively, and the ones including bilateral M1Ms were included in the study. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating three planes (coronal, sagittal, and axial) after a 3-dimensional alignment of the long axis of the root(s). The presence of an MMC in M1Ms (yes/no) was identified and recorded.

RESULTS

In total, 6304 CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries (P < .05). MMC prevalence ranged from 1% to 23%, and the overall prevalence was 7% (95% confidence interval [CI]: 5%-9%). No significant differences were found between the left and right M1M (odds ratio = 1.09, 95% CI: 0.93, 1.27; P > .05) or between genders (odds ratio= 1.07, 95% CI: 0.91, 1.27; P > .05). As for the age groups, no significant differences were found (P > .05).

CONCLUSIONS

The prevalence of MMC varies by ethnicity, but it is generally estimated at 7% worldwide. Physicians must pay close attention to the presence of MMC in M1M, especially for opposite M1Ms, due to the prevalence of MMC being significantly bilateral.

Frequency of middle mesial canal in mandibular first molars and its association with various anatomic variables

This study aimed to determine the frequency of the middle mesial canal in the mandibular first molars and its association with various anatomical features. Two experienced endodontists evaluated 149 CBCT images, containing n = 298 mandibular first molars and n = 298 mandibular second molars. Binary logistic regression was used to explore the relationship between the presence of middle mesial canal and other independent variables. The middle mesial canal was found in 7.7% (n = 23) of mandibular first molars and 11.4% of which exhibited adjacent C-shaped mandibular second molars. The presence of an adjacent C-shaped mandibular second molar was associated with a 3 times increased likelihood of finding a middle mesial canal (P = 0.048, OR: 3.108) in mandibular first molars. The middle mesial canal is an uncommon finding with a rare occurrence of bilateral presence in mandibular molars; however, an adjacent C-molar is an important predictor of middle mesial canal presence.

Analysis of the mandibular molars root canals morphology. Study by computed tomography

This study aimed to analyze the root and root canal morphology of mandibular first and second molars using CBCT images. A total of 2,400 mandibular molars exams were selected from 600 patients aged between 18 and 75 years. The number of roots, number of root canals, and root canal configuration according to the Vertucci classification were verified. Overall, 94.92% of mandibular first molars and 90.17% of mandibular second molars had two separate roots. Among the biradicular molars, the first molars showed a greater incidence of type IV canals in the mesial root and type I in the distal root. In the second molars, the most common canal form was type IV in the mesial root and type I in the distal root. In the triradicular molars, the type IV and type I configurations were the most common in the mesial root of the first molar and second molar, respectively. In both triradicular molars, there was a prevalence of type I canal in the distal and DL roots. Statistical analysis was performed at a significance level of 0.05. The number of roots was correlated with gender (Spearman test), and the canal's configuration with gender and bilaterality (Wilcoxon test). The subpopulation studied has a high incidence of bilateral symmetry and mandibular molars with two roots with two distinct mesial canals and one distal canal. The bilateral configuration is possible to estimate the number of canals, especially in images that are difficult to visualize, such as atresic canals.

Evaluation of Root Canal Configuration of Maxillary and Mandibular First Molar by CBCT: A Retrospective Cross-Sectional Study

Adequate knowledge of root canal morphology along with its probable variations is imperative to acquire successful endodontic treatment. This retrospective cross-sectional study aimed to investigate the root canal configuration of maxillary and mandibular first molar using Cone-Beam Computed Tomography (CBCT) among patients in Al-Ahsa region, Saudi Arabia. A total of 377 samples were included, out of which 123 CBCT (I-CAT Vision QTM) scans with intact all first permanent molars were selected in this study and scanned in sagittal, axial, and coronal views by using BlueSkyPlan software. The number of canals in each root and their configuration according to the Vertucci classification system was evaluated. Statistical analysis was analyzed using SPSS version 21 (IBM). Chi-square test was applied to evaluate the association of root canal morphology and mandibular and maxillary first molars with respect to gender. Out of 123 CBCT scans, 59 (48.0%) were males and 64 (52.0%) were females; the mean age was 26.95 ± 10.65 years. The mesiobuccal root of bilateral maxillary first molar had Type-I (87.0%) of Vertucci classification followed by Type-IV (9.8%). Additionally, all mesiobuccal roots (100%) of the left mandibular first molar had Type-I of Vertucci’s classification. A significant association has been observed between gender and a number of canals in bilateral maxillary first molars. Females showed a significantly higher prevalence of three-root canal configuration in maxillary first molars of both sides compared four canals found most commonly in males (p = 0.004). This study concluded that the majority of maxillary and mandibular permanent first molars had three roots and three canals with Type-I Vertucci’s classification in patients belonging to the Al-Ahsa region of the Saudi Arabia. It was also proved that gender is significantly associated with the number of canals in a bilateral maxillary molar.

Three-Rooted Permanent Mandibular First Molars: A Meta-Analysis of Prevalence

Introduction

Although numerous amounts of high-level evidence were present, they solely emphasized the tooth-level prevalence of three-rooted permanent mandibular first molar. Global patient-level prevalence and bilateral symmetrical distribution of this type of teeth were needed to be tackled across the world. The research question was "What is the global prevalence of three-rooted permanent mandibular first molars?"

Materials and Methods

In vivo epidemiological studies undergone with Cone Beam Computed Tomography (CBCT) were eligible. The proportions of the prevalence of three-rooted permanent mandibular first molars were presented in the forest plots by random effect model. The calculation was performed with MetaXL version 5.3. Subgroup analysis, sensitivity analysis, and publication bias method were also calculated.

Results

Seventy-two studies from 31 countries were selected for both qualitative and quantitative analyses. 26302 patients and 37994 permanent mandibular first molars were included in the analysis. 9% of permanent mandibular first molars all over the world demonstrated 3 roots. These three-rooted teeth were found in 10% of the world population, more than 45% of which revealed bilateral symmetry of that anatomy. Right-side dominance and no sexual dimorphism were seen in the distribution of three-rooted permanent mandibular first molars. Global tooth-level prevalence of Radix Entomolaris and Radix Paramolaris was 12% and 0.1%, respectively.

Conclusion

The prevalence of three-rooted permanent mandibular first molars (PMFMs) was influenced by different geographical locations across the world and also by widespread habitation of the Mongoloid descent. The authors postulate that globalization, together with blending among ethnicities, may have a great impact on the reduction or accentuation of the anatomical significance in some populations.

Proximity of maxillary molar apexes to the cortical bone surface and the maxillary sinus

Objectives

Materials and Methods

Results

Conclusions

Atypical Radicular Anatomy in Permanent Human Teeth: A Systematic Review

The aim of the present study is to classify and quantify the anatomical variations of teeth in terms of form and number of root canals reported in human teeth employing the classification systems proposed previously. An electronic (PubMed) and manual search were performed to identify case reports noting any of the anatomical variations. Each alteration was studied independently. The electronic search was performed using the following keywords: anatomical aberration, root canal, permanent Dentition, case report, c-shaped canal, dens invaginatus, palato-radicular groove, palato-radicular groove, palato-gingival groove, radix entomolaris, dental fusion, dental gemination, taurodontism, dilaceration. The initial search revealed 1497 papers, of which 938 were excluded after analyzing the titles and abstracts. Therefore, 559 potential papers were considered. Of those, 140 articles did not meet the inclusion criteria. For the final revision, 419 papers were considered. We found that the mandibular first premolar had the highest prevalence of C-shaped canals. Dens invaginatus was more frequently found in the mandibular lateral incisor. Taurodontism was more prevalent in the maxillary first molar and in the mandibular first molar. Dilaceration was not clearly associated with a particular tooth. The classifications systems used in this review allowed for the better understanding and analysis of the many anatomical variations present in teeth. The variations in shape most found were dens invaginatus and radix entomolaris. The most frequently reported anatomical variation was in the number of canals.

Assessment of the prevalence and configuration of middle distal canals in the mandibular molars in a Saudi subpopulation using Cone-Beam computed tomography

•

CBCT should be performed before treatment of complex root canal anatomy.

•

Occurrence of middle distal (MD) canal in the mandibular molar has been reported.

•

The prevalence of the MD canal in a Saudi subpopulation was found to be low.

•

It is crucial to determine additional canals to achieve successful root canal therapy.

Purpose

The prevalence of the middle distal (MD) canal in the mandibular molar is significantly low among countries including the USA, Spain, Turkey, and Jordan; however, analysis of its prevalence and configuration has not been performed in Saudi Arabia. Therefore, we aimed to assess the prevalence and configuration of the MD canal in Saudi Arabia.

Methods

A retrospective analysis of 132 cone-beam computed tomography (CBCT) images was performed to evaluate the presence of the MD canal in patients visiting the Radiology Department of The College of Dentistry in King Saud University between July 2018 and July 2019. The canal was examined if it was confluent with the distobuccal (DB) or distolingual (DL) canals, fin, or independent. Moreover, the distances from the MD canal to the DL and DB canals and cementoenamel junction (CEJ) were recorded.

Results

One MD canal (0.7%) was observed in 145 teeth. It was confluent with the DL canal. No statistical significance was observed among sex and age. The distances from the MD canal to the DL canal, DB canal, and CEJ were 1.4 mm, 1.9 mm, and 3.1 mm, respectively.

Conclusions

The prevalence of the MD canal was significantly low in a Saudi subpopulation (0.7%). Careful evaluation of CBCT images and the pulpal floor is significantly important to detect the MD canal to ensure a good prognosis.

Worldwide Assessment of the Mandibular First Molar Second Distal Root and Root Canal: A Cross-sectional Study with Meta-analysis

INTRODUCTION

This study assessed the prevalence of radix entomolaris and 2 canals at the distal aspect of mandibular first molars among different geographic regions by means of cone-beam computed tomographic imaging.

METHODS

Precalibrated observers from 23 worldwide geographic locations followed a standardized screening protocol to assess 5750 cone-beam computed tomographic images of mandibular first molars (250 per region), gathering demographic data and recording the presence of radix entomolaris and a second canal at the distal aspect of teeth. Intra- and interrater reliability tests were conducted and comparisons among groups were performed using proportions and odds ratio forest plots. The significance level was set at 5%.

RESULTS

The results of intra- and interrater tests were above 0.79. The prevalence of radix entomolaris varied from 0.9% in Venezuela (95% confidence interval [CI], 0%-1.9%) to 22.4% in China (95% CI, 17.2%-27.6%). Regarding the proportion of a second distal canal, it ranged from 16.4% in Venezuela (95% CI, 11.8%-21.0%) to 60.0% in Egypt (95% CI, 53.9%-66.1%). The East Asia subgroup was associated with a significantly higher prevalence of an extra distolingual root, whereas the American subgroup, the American native ethnic group, and elderly patients were linked to significantly lower percentages of a second canal at the distal aspect of teeth. No significant differences were noted between male or female patients.

CONCLUSIONS

The overall worldwide prevalence rates of radix entomolaris and a second canal at the distal aspect of the mandibular first molar were 5.6% and 36.9%, respectively. The East Asia geographic region and Asian ethnic group had a higher prevalence of a second distal root.

The mid-mesial canal prevalence in mandibular molars of a Saudi population: A cone-beam computed tomography study

INTRODUCTION

The aim was to assess the prevalence of Mid Mesial Canal (MMC) in the first and second mandibular molars in a Saudi subpopulation sample and assess its relation to side, gender, and age using Cone beam computed tomography (CBCT).

METHODS

The CBCT scans at King Saud University Dental Hospital between 2016 and 2019 were reviewed and filtered. The MMC of the mandibular molars were assessed according to Pomeranz et al. classification which was: (1) independent; (2) fin; (3) confluent with the mesiobuccal canal; and (4) confluent with the mesiolingual canal. Three calibrated observers examined the MMC on all planes at both sides. Age and gender factors were used to analyze that prevalence. A chi-squared test was used and (P ≤ 0.05) was considered to be statistically significant.

RESULTS

395 patients, and 1377 teeth met the inclusion criteria. The total number of mid-mesial canals was 12 (0.9%): nine at the mandibular first molar (1.3%) and three in the mandibular second molar (0.4%). The most common type of mid-mesial canal was confluent (n = 10), of which 6 fused with the mesiobuccal canal and 4 fused with the mesiolingual canal. Two canals were of the fin type, and there was no instance of independent mid-mesial canal. There was no significant difference between all variables: tooth type, tooth side, patient gender, and patient age group (p > 0.05).

CONCLUSION

In this study, the most common MMC configuration was the confluent type followed by the fin type and no independent type were found. The patient side, gender and age did not influence the prevalence of the MMC.

Evaluation of C-shaped canals in mandibular second molars of a selected patient group using cone beam computed tomography: prevalence, configuration and radicular groove types

The aim of the present study was to examine the prevalence, symmetry and configurations of C-shaped canals and radicular groove types in mandibular second molars according to age and sex in a Turkish sub-population using cone beam computed tomography (CBCT). In total, 674 CBCT images (368 females and 306 males, aged 18-76 years) of 1348 mandibular second molars were evaluated. The symmetry, configuration of C-shaped root canals, radicular groove types with age and sex were noted. One sample chi-square test and chi-square test were used to determine statistically significant differences. The statistical significance level was set at p < 0.05. Of the 1348 mandibular second molars evaluated, 10.7% had C-shaped root canals. C-shaped root canals appeared to be significantly more common in females than in males (p < 0.05). C1 (44.4%) was the most frequent configuration in the coronal third, and C2 (44.4%), and C4 (31.9%) were the most frequent configurations in middle and apical thirds, respectively. Type 2 (45.1%) was the most common radicular groove type (p < 0.05). The frequency of C-shaped root canals in mandibular second molars in a Turkish sub-population was considerably high (10.7%). CBCT can aid the detection of C-shaped canals and their configurations. Dentists should consider the possibility of C-shaped canals in root canal treatment of mandibular second molars, as these configurations have implications for biomechanical preparation and filling methods.

Prevalence and Morphology of C-Shaped Canals: A CBCT Analysis in a Korean Population

This retrospective study of roots with C-shaped canals investigated their prevalence, configuration type, and lingual wall thickness, as well as the panoramic radiographic features of roots in permanent mandibular second molars confirmed to have C-shaped canals on cone-beam computed tomography (CBCT) in a Korean population. In total, 1884 CBCT images of mandibular second molars were examined by two endodontists to analyze the presence of C-shaped canals according to age and sex. The bilateral occurrence of C-shaped roots and their morphology on panoramic radiography were assessed and statistically analyzed using the chi-square test. The classification of Fan et al. was applied to categorize the configurations of C-shaped canals. The lingual wall thickness was calculated in the mesial, middle, and distal areas at the orifice and at 5 mm from the apex. The Mann-Whitney U test was used to analyze the mean difference of lingual wall thickness between the apex and orifice level. A P value of 0.05 was considered to indicate statistical significance in the statistical analyses. Of 2508 mandibular second molars, 924 (36.8%) had C-shaped root canals. The prevalence was significantly lower in the over 61 age group (24.08%) than in the 21-30-year age group (40.02%) and was higher in women (42.32%). Most cases were bilateral (85.9%). The C1 type was the most common (35.3%). The prevalence of C1 type canals decreased, while that of C3b type canals increased with age. In 75.2% of teeth having C-shaped root canals on CBCT, fused roots were observed on panoramic views. The difference in the lingual wall thickness at the orifice and 5 mm from the apex was significant in the middle area in all configurations of C-shaped root canals. When performing nonsurgical or surgical endodontic procedures of the mandibular second molars, clinicians should consider age, sex, ethnicity, and anatomical variations.

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

Background

Cone-beam computed tomography (CBCT) was employed to study the morphology and curvature of middle mesial canals (MMCs) of mandibular first molars (MFMs).

Methods

CBCT 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.

Results

In 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%).

Conclusion

The 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.

Prevalence and Distribution of the Middle Mesial Canal in Mandibular First Molar Teeth of the Kerman Population: A CBCT Study

PURPOSE

Missed additional canals are one of the most important reasons for RCT failures in molar teeth. This study aimed to determine the prevalence and distribution of middle mesial canals in mandibular first molars of the Kerman population.

MATERIALS AND METHODS

A retrospective study was performed on de-identified cone beam image sets from 3 private radiology centers in Kerman. A total of 100 mandibular first molars from 62 patients (mean age 32 years) were included. Information regarding the patient's age and gender, the location of teeth, and the presence or absence of a MMC and also a second distal canal in MMC cases was recorded in an Excel table. Data were analyzed using SPSS software (IBM-USA).

RESULTS

The overall prevalence of MMCs in the mandibular first molars was 8.1% (10.0% in females and 6.3% in males). More cases of MMCs were seen on the right side (12.2%) than the left side (3.4%). One case of bilateral MMCs combined with bilateral second distal canals in the mandibular first molars was seen in a 26-year-old female. A further case of bilateral MMCs was found in a 32-year-old male but with single-canal distal roots on both sides.

CONCLUSION

The overall prevalence of MMCs in the Kerman population (8.1%) is at the lower end of the reported range of the international literature (0.26% to 53.8%). In the cohort examined in this study, mid mesial canals were more prevalent in females and on the right side. There was no definite relationship between MMCs and second distal canals in the mandibular first molar teeth in the same subject. MMCs may be unilateral or bilateral. Careful exploration of the pulpal floor between canal orifices is essential to prevent missing the MMC, as this would cause undesirable clinical outcomes.

Prevalence of middle mesial canal and radix entomolaris of mandibular first permanent molars in a western Chinese population: an in vivo cone-beam computed tomographic study

Background

The aim of this study was to investigate the prevalence of the middle mesial canal (MMC) and radix entomolaris (RE) in mandibular first permanent molars in a western Chinese population using cone-beam computed tomography (CBCT).

Methods

A total of 1174 CBCT images of the mandibular first molars were collected from West China Hospital of Stomatology, Sichuan University. The following information was recorded and evaluated: the detection rate and location of the MMC and RE, the curvature of the RE, the canal configuration and bilateral symmetry.

Results

The detection rates of the MMC and RE were 3.41 and 25.04%, respectively, as calculated by individuals, and 1.79 and 22.15%, respectively, as calculated by total teeth. The average curvature in the buccolingual (BL) orientation (40.63 ± 14.39°) was significantly larger than that in the mesiodistal (MD) orientation (17.64 ± 7.82°) (p < 0.05). Of 587 patients, 71.72% (421/587) had bilateral symmetry according to the root canal morphology. The prevalence of three-rooted mandibular first molars was higher in males than in females, while the prevalence of two-rooted mandibular first molars was higher in females than in males.

Conclusions

Our results showed that the RE could be detected in almost 1/4 of the western Chinese population; thus, RE detection requires special attention and careful assessment in endodontic treatment.

Cone-beam computed tomography investigation of middle mesial canals and isthmuses in mandibular first molars in a Chinese population

Background

While there is ample research into the anatomy of mandibular molars, little is known regarding isthmuses and middle mesial (MM) canals in Chinese populations. The goal of this study was to determine the prevalence of MM canals and isthmuses in the mesial root of mandibular first molars using Cone-beam Computed Tomography.

Methods

Cone-beam Computed Tomography images of 357 mature mandibular first molars were retrospectively analyzed. Presence of isthmuses and MM canals, and the length of isthmuses in the mesial root were recorded. Meanwhile, we also recorded possible correlated factors such as demographics, side of mandible, presence of separated distal-lingual roots.

Results

Of these 357 teeth, 209 showed evidence of either complete or partial communication in the mesial root. Of these, 11(3.1%) exhibited true MM canals while 198(55.5%) exhibited isthmuses. Sex or side of mandible was not correlated with the prevalence of isthmuses (P > 0.05). However, there was a significant association between the presence of a distal-lingual root and the prevalence of such communication (P < 0.001). The average length of isthmuses was 4.3 ± 3.1 mm.

Conclusions

We detected high rate of isthmuses and low rate of MM canals in mesial roots of mandibular first molars, which is important as such areas should be identified and cleaned during root canal treatment.

C-shaped canals in mandibular molars of a Brazilian subpopulation: prevalence and root canal configuration using cone-beam computed tomography

OBJECTIVES

To assess C-shaped root canal configuration by identifying its prevalence and each configuration type proportion, according to tooth (mandibular first or second molar) and demographic characteristics in a Brazilian population, using cone-beam computed tomography (CBCT). Moreover, it was verified if there is a relationship between root canal configuration observed in two-dimensional reconstructions of CBCT and presence of C-shape.

METHODS

Mandibular jaw CBCT scans (184 males and 220 females, aged 15 to 80 years), which presented 1464 mandibular molars (710 first molars and 754 second molars), were assessed. Teeth were evaluated for the presence and type of C-shaped root canals by observing the roots at five levels in CBCT axial reconstructions. Root canal configuration was assessed in panoramic reconstructions. Data were statistically analyzed at a significance level of 5%.

RESULTS

Of the 1464 mandibular molars, 125 (8.5%) were classified as C-shaped. This variation was more prevalent in females (n = 107, 85.6%) and in second molars (n = 108, 86.4%). C1 (uninterrupted C-shaped canal) was the most prevalent type of C-shaped configuration (41.76%), while C5 (no canal lumen) was the least prevalent type (0.96%). Single root with single canal in panoramic reconstructions was the most predominant configuration for C-shaped teeth (n = 54, 43.2%). Fused roots presented 17.2 higher odds of being associated with C-shaped root canals than non-fused roots.

CONCLUSIONS

C-shaped root canals were more prevalent in mandibular second molars and in females. Additionally, clinicians should bear in mind the greater possibility of C-shaped configuration in mandibular molars with fused roots.

CLINICAL RELEVANCE

Mandibular molars with C-shaped canals present a clinical challenge. A higher C-shaped proportion was noted in radiographic fused root types, which had 17.2 higher odds of presenting such anatomy when compared to radiographic non-fused roots. Root radiographic features may help in diagnosis of complex C-shaped morphologies.

Biometric analysis of apical surgery-related anatomy of mandibular first molars: a cone-beam computed tomography study in a Mongoloid population

Objective

To evaluate the apical surgery-related anatomy of two-rooted and three-rooted mandibular first molars (MFMs) in a Mongoloid population.

Methods

A total of 502 cone-beam computed tomographic images were used to evaluate the root configuration, the distance from the buccal bone to each root, root dimensions, and the complete root resection distance at the resection level for roots of MFMs.

Results

The prevalence of two-rooted and three-rooted MFMs was 85.1% and 14.9%, respectively. At the resection level, the distance from the buccal bone to the mesial and distal roots of two-rooted MFMs was 2.24 and 3.15 mm, respectively, while the distance was 2.44, 2.01, and 8.55 mm for the mesial, distobuccal, and distolingual roots of three-rooted MFMs, respectively. The distance from the buccal bone to each root was longer in men than in women. The largest distance for complete root resection was detected for the distal root in two-rooted MFMs and for the distolingual root in three-rooted MFMs.

Conclusions

The prevalence of three-rooted MFMs is common in the Mongoloid population. The distance from the buccal bone to root apex differs according to root configurations and sex. Surgical access to the distolingual root is difficult because of the long access distance.

Cone-beam computed tomographic analysis on root and canal morphology of mandibular first permanent molar among multiracial population in Western European population

Objectives:

In the present study, confluent canals in the mandibular first molar's mesial root were investigated in an Italian population by means of cone-beam computed tomography (CBCT).

Materials and Methods:

A total of 200 molars, selected from the CBCT examinations of 130 patients who required this type of X-ray study as part of their dental treatment, were examined. The evaluated parameters were number of canals, root canal system configuration, presence of apical confluences, distance between confluences and apical foramina, which canal had a higher degree of curvature, and symmetry between left and right elements in the same individual.

Statistical Analysis Used:

Percentages of the cases were reported.

Results:

All the examined roots presented two canals. In 59% of cases, a Vertucci Type IV canal configuration was observed, while in 41% of cases, a Type II configuration was observed. Apical confluences were present in 41% of cases. The average distance between confluences and apical foramina was 2.85 mm. When confluences were present, the mesiobuccal canal showed a higher degree of curvature in 78% of cases. Symmetry in Vertucci configuration was seen in 88% of cases.

Conclusions:

Apical confluences in the mesial roots of mandibular molar can be present in a significantly high number of cases, and their recognition is essential to prevent the iatrogenic errors during canal instrumentation.

Root and Root Canal Morphology Differences Between Genders: A Comprehensive in-vivo CBCT Study in a Saudi Population

OBJECTIVES

To comprehensively explore the differences of all maxillary and mandibular permanent teeth in relation to number of roots, number of root canals, and root canal configuration between both genders in a Saudi Arabian population.

METHODS

This retrospective radiographic study comprised 208 subjects (48% males and 52% females) with a mean age 28.74±9.56 years. The CBCT images of the recruited subjects were evaluated for all permanent teeth. A careful examination was obtained by optimal visualization using all the software features. The data were analyzed using SPSS software program. Cohen's Kappa test was used for reliability and the Chi-squared test of association was used for the differences between both genders in relation to the study variables. A P-value < 0.05 was considered significant.

RESULTS

A total of 5254 maxillary and mandibular permanent teeth were evaluated. In relation to number of roots, there were no significant differences between both genders for all maxillary and mandibular teeth together (P= 0.064) as well as for maxillary and mandibular teeth separately (P= 0.315 and P= 0.100, respectively). A significant difference was found between males and females in relation to the number of canals of maxillary teeth (P= 0.014). For mandibular teeth, the significant level of difference was at the cut-off point (P= 0.050). For all maxillary and mandibular teeth together, the distribution among both genders was not significant (P= 0.082). The difference between both genders with regard to canal configuration of maxillary roots was highly statistically significant (P< 0.001). For mandibular teeth, the difference between males and females in relation canal configuration of anterior and premolar teeth was significant (P= 0.016) while, the difference was not significant when related to mesial roots of 1st and 2nd molars (P= 0.205). However, the difference was highly significant when related to distal roots of 1st and 2nd molars (P< 0.001).

CONCLUSION

No significant differences between both genders in relation to number of roots were found. Regarding the number of canals, significant differences were found only in three groups out of 14 groups of teeth with females who had a smaller number of canals than males. For canal configuration, two groups of maxillary teeth and three groups of mandibular teeth showed statistically significant differences between both genders.

Anatomical variations and bilateral symmetry of roots and root canal system of mandibular first permanent molars in Saudi Arabian population utilizing cone- beam computed tomography

Aim

The aim of the study was to evaluate the anatomical variations of the roots and root canal system, and to determine the symmetry between right and left sides of mandibular first permanent molars in Saudi Arabian population using images derived from cone beam computed tomography (CBCT) scans.

Methods

The CBCT scans (with the following parameters: FOV 170 × 120 mm, 90 Kv, 5–8 mA, 17.5 s exposure time and 0.25 mm voxel size) were retrieved from the database and axial, coronal and sagittal sections of mandibular first molars were examined. The number of roots, canals and type of canal configuration based on Vertucci’s classification were recorded. Bilateral symmetry between right and left side of the same individuals and differences between genders were investigated.

Results

Out of 174 mandibular first molars, 97.1% were two rooted and 2.9% were three rooted (distolingual root). In regards to the number of canals, 73% had three, 25.3% had four and 1.7% had two root canals. In teeth with four root canals, 90.9% of the extra canal was in the distal root, while 9.1% in the extra distolingual root. The most common canal configuration in mesial and distal root were type IV (64.9%) and type I (77%), respectively. Symmetrical analysis revealed 100% symmetry in number of roots and 56.4% in number of canals between right and left teeth in the same individual.

Conclusions

Within the limitation of this study, wide range of canals configurations were noted in mandibular first molars among the Saudi Arabian population. The prevalence of three rooted mandibular first molars was relatively low. Three canals were most commonly seen in mandibular first molars. Bilateral symmetry was varied in number of canals and canals configurations, which could be of clinical significance while performing root canal treatment on both side mandibular first permanent molars.

Presence of isthmi in mandibular mesial roots and associated factors: an in vivo analysis

Purpose

To investigate the prevalence of isthmi and middle mesial (MM) canals in the mesial roots of mandibular first molars (MFM) in a Mongoloid subpopulation and to evaluate their association with demographic and anatomic characteristics.

Methods

Cone-beam computed tomography (CBCT) images of 496 patients with 823 MFMs were selected and analyzed. The following data were collected: patient age and gender, side, presence and distribution of MM canal and isthmus, distance between mesiobuccal (MB) and mesiolingual (ML) orifices, and MB–ML root canal system (RCS) morphology. Logistic regression was used to determine the association between demographic and anatomic characteristics and the presence of isthmi in the apical third.

Results

The overall prevalence of isthmus and an MM canal in MFM was 64.6% and 10.8%, respectively. The highest prevalence of isthmi and MM canals was found in patients of ≤ 20 and of 41–60 years, respectively (p < 0.05). The prevalence of isthmi declines with age. A total of 41.3% of the MFMs had isthmi in the apical third of the mesial roots. Younger age, shorter MB–ML orifice distance, and Weine type II RCS increased the probability of the presence of an isthmus in the apical third (p < 0.05).

Conclusion

The prevalence of isthmus in MFM is high in the subject population, but the prevalence of MM canals is not as high as previously reported. Demographic and anatomic characteristics could aid clinicians to better predict the presence of MM canal and an isthmus.

Radiographic Indications of Vertucci Type V Configuration in the Distal Root of Mandibular Molars: A Case Series

Knowledge of the prevalent root canal anatomy and potential variations is necessary before the initiation of endodontic treatment. The purpose of this study was to aid in the detection and treatment of the Vertucci type V canal configuration when present in the distal root of the mandibular molars. This case series presents 3 radiographic indications of a type V configuration in the distal roots of the mandibular molars as revealed on conventional periapical radiographs: a "ghost" apex, a fast break canal, and eccentric canal tracing. Nonsurgical endodontic treatment was performed for 5 mandibular molars with the type V distal root canal. Four cases showed posttreatment resolution of symptoms and return of normal function. One case was classified as "failed" because of persistent symptoms and clinical signs. The tooth was surgically treated and subsequently healed. These case reports show the importance of visualizing and managing the anatomic variations of the canal system in distal roots of mandibular molars and incorporating these capabilities into clinical practice to enhance the occurrence of a successful outcome. Additionally, clinical guidelines are provided that can help clinicians overcome the challenges in diagnosing and treating such complex cases.

Root canal morphology of permanent teeth in a Malaysian subpopulation using cone-beam computed tomography

Background

To determine the root canal morphology of human permanent maxillary and mandibular teeth in a Malaysian subpopulation using cone-beam computed tomography (CBCT).

Methods

A total of 208 CBCT images were examined retrospectively. Prevalence of an extra root/canal and internal morphology based on Vertucci’s classification were observed in human maxillary and mandibular permanent teeth. Variations in the external and internal morphology were compared in relation to gender and tooth side (left vs right) using Pearson Chi-square and Fisher’s exact tests with significance level set at p < 0.05.

Results

In the maxillary arch, the prevalence of three canals were observed in 0.3% of first premolars and two canals in 46.5% of second premolars. Males displayed significantly higher prevalence of two canals in maxillary second premolars than females (p < 0.05). The prevalence of a second mesiobuccal canal in maxillary first and second molars were 36.3 and 8.5%, respectively. Males displayed significantly higher prevalence of a second mesiobuccal canal in maxillary second molars than females (p < 0.05). The prevalence of a second palatal canal in maxillary first and second molars were 0.9 and 0.6%, respectively. In the mandibular arch, the prevalence of two canals were observed in 5.1% of central incisors, 12.3% of lateral incisors, 6.1% of canines, 18.7% of first premolars and 0.5% of second premolars. The prevalence of a middle mesial canal, second distal canal and extra root (radix entomolaris) were detected in 1.9, 19.5 and 21.4% of mandibular first molars, respectively. The prevalence of a C-shaped canal was observed in 48.7% of mandibular second molars. Females displayed significantly higher prevalence of a C-shaped canal in the right mandibular second molars than males (p < 0.05). No other statistically significant differences in root anatomy and root canal morphology were observed in relation to gender and tooth side.

Conclusions

Wide variations in the root canal morphology exist among Malaysians. CBCT is a clinically useful tool in the identification of external and internal morphological variations in the human teeth.

Morphology and prevalence of middle canals in the mandibular molars: A systematic review

Objectives:

The purpose of this paper is to systematically review the various studies and case reports on the morphology and prevalence of middle canals in the mandibular molars.

Methodology:

Electronic databases such as MEDLINE, PubMed, EBSCOhost, ScienceDirect and various journals were screened to identify published literature till March 2017 and earlier for articles related to middle canals in the human permanent mandibular molars. Obtained articles were categorized as original researches, case reports and review articles. Well-defined review questions were developed using the patient population, intervention, comparison and outcome framework to summarize the objectives: “Does middle canal vary in morphology and anatomic location? What is the prevalence of middle canals in mandibular molars? Does ethnicity affect the prevalence of middle canals in mandibular molars?” Morphology was studied and prevalence rates were determined from the evaluation of data extracted from the articles.

Results:

The search strategy resulted in 87 articles, of which 36 were original research papers and 51 were case reports. The prevalence of middle canals in the various populations ranged from 0.26% to 53.8%. Middle canals were reported in Europeans, Asians, Africans and South and North American populations. The prevalence of middle mesial canal and middle distal canal in various races was reported as up to 53.8% and 10%, respectively. The orifice of middle canal exists below a dentinal projection in the groove between the two main canals. They were observed in fin, confluent and independent configuration. Out of these, confluent configuration was more prevalent.

Conclusion:

Middle canal varies in morphology and anatomic location. Ethnicity affects the prevalence of middle canals in the mandibular molars.

Root and root canal variations of the human maxillary and mandibular third molars in a Chinese population: A micro-computed tomographic study

OBJECTIVES

To investigate the anatomical variations of the root and root canal configuration of the human third molars.

DESIGNS

A total of 130 maxillary and 130 mandibular third molars were collected from a native Chinese population. All teeth were scanned by micro-computed tomography. After 3D reconstruction, the root and canal morphology of each tooth was examined both qualitatively and quantitatively.

RESULTS

For maxillary molars, a single fused root (67 cases, 51.5%) and a single root canal system (64 cases, 49.2%) was most common root/canal form; the typical three-rooted molars were detected only in 33 cases (25.4%), and the secondary MB canals were detected only in 9 molars (6.9%). For mandibular molars, 62 teeth were single-rooted (47.7%) and 42 had a single root canal system (32.3%); 20 singled-rooted and 60 double-rooted molars exhibited independent mesial and distal root canal systems (61.5%), and the type 1-1 canal was the most common configuration for mesial (57 cases) and distal (81 cases) root canal systems. C-shaped canals were detected in 11 maxillary and 36 mandibular single-rooted molars. The mean root surface area, root and crown volume of mandibular third molars were significantly higher than the maxillary third molars (P <  0.01).

CONCLUSION

The root canal system of the third molars may exhibit several anatomic variations. Whereas in most of cases, the degree of the canal differentiation was at a low level, and the canal form was not complicate.

[Cone-beam computed tomography for determination of mesial root canal curvatures of human mandibular first molars]

OBJECTIVE

To investigate mesial root canal curvatures of human mandibular first molars using cone-beam computed tomography (CBCT).

METHODS

CBCT was performed for scanning the mandibular first molars of 1600 Chinese subjects, among whom the subjects identified to have middle mesial canals were divided into 5 age groups, namely group A (18-29 years), group B (30-39 years), group C (40-49 years), group D (50-59 years), and group E (60-80 years) for further analysis. All the CBCT images were reconstructed using Planmeca Romexis CBCT image reconstruction system, and the curvature of the mesial root was measured using the Schneider method.

RESULTS

A total of 2856 CBCT images were obtained from the 1600 subjects, among whom 168 (5.88%) were found to have middle mesial canals in the mandibular first molars. The prevalence of middle mesial canals was 37.50% in group A, 17.80% in group B, 14.88% in group C, 19.64% in group D, and 10.12% in group E. The moderate of the curvature in the mesiodistal direction was significantly higher in group A than in the other groups (P < 0.05); the curvature in mesiodistal direction differed significantly among the 5 groups (P < 0.05), and was the greatest in group A followed by group C and group D, and was the smallest in group E. The curvature in the buccolingual direction was similar among the 5 groups. The incidence of mesiodistal and buccolingual curvature of the middle mesial canals was significantly higher in the middle 1/3 of the root canal than in the upper 1/3 and apical 1/3 of the root canal.

CONCLUSIONS

The incidence of middle mesial canals in the mesial root of the mandibular first molars decreases with age. The middle mesial canal system of the mandibular first molar is complex and variable, and most of the first molars have obvious curvature in the mesiodistal and buccolingual directions. CBCT can provide reference for clinical treatment to reduce the treatment failure rate.

Anatomy of Permanent‎ ‎Mandibular‎ First‎ Molars in a Selected Iranian Population Using ‎Cone-beam Computed Tomography

Introduction:

Knowledge of radicular anatomy has a crucial impact on endodontic practices. Since some anatomic features such as modifications of Vertucci are not evaluated adequately, this study was conducted.

Methods and Materials:

In this in vivo study, cone-beam computed tomography (CBCT) images of‎ 312‎ intact bilateral first‎ molars‎ from‎ 156‎ patients‎ (‎79‎ ‎males‎ and‎ 77‎ females with an average age of ‎35.58‎±‎11.17‎ years‎)‎ were‎ investigated by a trained dentist in terms of number‎ of‎ roots,‎ number‎ of‎ canals‎ in‎ each‎ root‎ and‎ in‎ ‎each‎ tooth,‎ and shapes‎ of‎ canals‎ according‎ to‎ Vertucci’s‎ classification‎ and‎ its‎ modifications.‎ Groups were compared using the Chi-square test. The level of significance was set at 0.05.

Results:

Of all teeth, 5.2%‎ had‎ 3‎ roots.‎‎ ‎Mesial‎ roots‎ had‎ mostly‎ 2‎ canals‎ while distal roots had a similar frequency of 1 and 2 canals.‎ ‎Of‎ all‎ teeth,‎ ‎‎39.7%‎ had‎ 3‎ canals,‎ 45.2%‎ had‎ 4‎ canals,‎ 13.8%‎ had‎ 5‎ canals,‎ and‎ 1.3%‎ had‎ 6‎ canals.‎ There were no significant differences between males and females, ‎in terms of number of roots (P=0.137), number of canals in mesial (P=0.453) or distal roots (P‎‎=0.328), and total number of canals (P=0.138).‎ The most frequent Vertucci classes in mesial and distal roots were IV ‎‎followed‎ by‎ II and I‎, respectively. There were no significant differences between males and females in terms of Vertucci classes of mesial (P=0.211) or distal (P=0.205) roots.

Conclusion:

In this population, there were 3 to 6 canals per tooth (mostly 4 and 3 canals).‎ Males and female’s ‎might be similar regarding the number of roots, or number of canals in each root, number of ‎canals in each tooth, or the predominant canal shape in each root.