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.

Endodontic treatment of the mandibular first molar with six root canals: A case report and literature review

The mandibular first molars normally have three or four root canals and rarely have five or more root canals. The present study reported a rare anatomical configuration with six root canals in the mandibular right first molar diagnosed during endodontic treatment using a dental operating microscope and confirmed with the help of cone-beam computed tomography (CBCT) images. The present case report revealed that there is an increasing possibility of detecting additional canals through the magnification of the microscope and the improvement of CBCT diagnostic technology. As more abnormal morphologies in root canals are reported, dentists need to understand this diversity in anatomical structure and improve treatment techniques.

Impacted Mandibular First Molar: A Rare Riddle

Tooth impaction incidence is in the range of 5.6 to 18.8% of the population. Eruption failure of the first permanent molar is very rare; the prevalence is 0.01% of the population. The permanent molars are of particular importance in providing adequate occlusal support as well as coordinating facial growth. Failure of the eruption of permanent molars might lead to an array of complications like a reduction in the vertical dimension, extrusion of the antagonist teeth, a posterior open bite, inclination and resorption of adjacent teeth, and cyst formation. Various treatment modalities for impacted teeth include periodic observation, orthodontic relocation, and partial dislocation. More invasively, surgical exposure and extraction of teeth before prosthetic treatment may be performed. It is imperative to diagnose and manage the condition early, as delayed treatment may result in a myriad of problems, like a decreased force of the spontaneous eruption, a decreased percentage of treatment success, and a prolonged period of treatment, increasing the complications furthermore. Because of the importance of permanent molars, eruptive guidance is required before impacted tooth extraction. This article summarizes a case in which the surgical-orthodontic combined approach to the impacted mandibular first molar avoided the need for prolonged orthodontic treatment that would have required repositioning the deeply impacted first molar to the dental arch. As an outcome, patient satisfaction improves.

A comparison of volume of tissue removed and biomechanical analysis of different access cavity designs in two-rooted mandibular first molars: a multi-sample three-dimensional finite element analysis

INTRODUCTION

The aim of this study was to compare the biomechanical properties and the amount of coronal tissue removed among the different access cavities with a multi-sample three-dimensional finite element analysis in mandibular first molar. The correlation between the amount of tissue removed and the fracture resistance of the teeth was also analysed.

METHODS

Micro-CT data from 20 two-rooted mandibular first molars were included in this study as three-dimensional modelling prototypes. The models of untreated molars and molars treated with the Traditional Access Cavity (TradAC), the Conservative Access Cavity (ConsAC) and the straight-line minimally invasive endodontic access cavities (SMIAC) were created. Each model was loaded in 3 ways to simulate the functional conditions of occlusion. The amount of tissue removed and the maximum stress in the cervical region were recorded and analysed, and the correlation between them was also analysed.

RESULTS

The amount of coronal tissue and peri-cervical dentin (PCD) removed in SMIAC and ConsAC was less than that of TradAC. The mean maximum stress in the cervical region was significantly smaller in SMIAC and ConsAC than in TradAC. The amount of hard tissue and PCD loss was positively correlated with the maximum stress in the cervical region of the tooth.

CONCLUSIONS

In mandibular first molars, it could be beneficial to improve the fracture resistance of the tooth after endodontic treatment by the minimally invasive access cavity to reduce the loss of coronal tooth tissue and PCD. The SMIAC may be an option balancing biomechanical properties and clinical convenience.

First Molars in Permanent Dentition and their Malformations in Various Pathologies: A Review

Permanent maxillary and mandibular first molars are the first permanent teeth to erupt into the oral cavity along with the mandibular incisors. It serves as an excellent record of maternal and fetal health, reflecting the prenatal, perinatal, and postnatal health and diseases. This review focuses on the molar morphogenesis, molar malformations, their etiopathogenesis, and pathologies causing specific pattern of molar malformations.

Periodontal treatment of furcation involvement at the mandibular first molar with a follow-up of 27 years

Due to the complicated anatomical structures in the furcation area of multirooted mandibular first molars, dental hygiene is greatly compromised once the furcation is involved in the periodontitis, leading to the unfavorable prognosis of teeth with furcation involvement. A patient came to a dental office with the chief complaint of "mobile mandibular posterior tooth" 27 years ago. The periapical film showed alveolar bone resorption at the root furcation of the right mandibular first molar. Flap surgery and fine supportive therapy were conducted. The patient was diagnosed with "furcation involvement Class Ⅲ" during a revisit three years ago. Satisfactory and healthy periodontal statuses were observed 2, 9, 24, and 33 months after the periodontal flap surgery plus tunneling procedures. A follow-up of 27 years in the present case demonstrated that a favorable prognosis of furcation involvement can be achieved after adequate periodontal treatment.

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

INTRODUCTION

The purpose of this study was to comprehensively assess by micro-computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population.

METHODS

One hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature.

RESULTS

All DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P < .05) but not for types I and III (P > .05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion.

CONCLUSIONS

The novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal.

Root and Canal Configuration of Mandibular First Molars in a Yemeni Population: A Cone-beam Computed Tomography

Objective:

To describe root and canal morphology of mandibular first molars (MFMs) in a Yemeni population using cone-beam computed tomography (CBCT).

Methods:

CBCT images of 500 right and left untreated MFMs with fully developed roots from 250 Yemenis (125 male and 125 female) comprised the sample size of this study. The following characteristics were recorded: (1) number of roots and their type and morphology, (2) number of canals orifices per root, (3) type of canal configuration and (4) primary variations in the morphology of the root and canal systems.

Results:

96.8% of MFMs are double-rooted. A third root was found in 3.2%, more in females than males. Mesial root was mainly ribbon-shaped (92.2%) and distal root was kidney-shaped in 56.2%. Two canals orifices were found in mesial root of 95.8% and one canal orifice was found in distal root of 96.4%. Vertucci type II canal configuration was the most frequent (57%), followed by type IV (35.6%) in mesial root. Type III canal configuration was the most prevalent (48.8%), followed by type I (41%) in distal root. Variant 3 represented the most common root and canal morphology (89.8%).

Conclusion:

MFMs in Yemeni population are mainly two-rooted with 3.2% having a supernumerary distolingual root. Cross section of mesial root was mainly ribbon-shaped and distal root was kidney-shaped. Vertucci type II and III configurations were the higher incidence in mesial and distal roots, respectively. The presence of two canals in mesial root and one canal in distal root of MFMs with two separate roots (variant 3) was the most common morphology.

Management of Three Rooted Mandibular First Molar with Six Canals: A Case Report

The objective of dentists is to preserve teeth affected by either caries, trauma, or any other pathological condition. Teeth with deep carious lesions often require endodontic treatment to preserve their form and function. Sound knowledge of root canal anatomy, endodontic pathology, and proper treatment protocol are vital in endodontic treatment success. Currently, there has been an ongoing trend of case reports that highlight the presence of extra canals, which in turn, cautions the clinician to be more prudent. Any missed canal during root canal therapy is the common cause of treatment failure. This case report emphasizes the fact that proper understanding of pulp anatomy combined with the use of modern diagnostic aids and proper treatment protocol is essential for treatment success. This case report describes successful management of three rooted mandibular first molar with extra canals.

[Finite-element analysis of mandibular first molar with two marginal designs of endocrown for the repair of different defects]

OBJECTIVE

This study aimed to evaluate the stress distribution of the mandibular first molar with different thicknesses and heights of the axial wall restored by the endocrown with two marginal designs and thus provide a theoretical basis for selecting clinical preparation through the finite-element method.

METHODS

Two marginal endocrowns of the mandibular first molar with different axial-wall thicknesses (t=1, 2, 3 mm) and heights (h=2, 3, 4 mm) were established. Group A was the butt-joint design, whereas group B was the shoulder-surrounded design. After applying vertical and oblique loads , the size and distribution of the maximum principal stress and equivalent stress of residual tooth tissue were recorded.

RESULTS

The maximum principal stress and equivalent stress distribution of residual tooth tissue were similar among different models. Group A showed a lower maximum principal stress and equivalent stress than group B at the same thickness and height under vertical load. Meanwhile, under oblique load, the maximum principal stress values of groups A and B decreased with increased thickness at constant height. Group A showed lower equivalent stress than group B at the same thickness and height of 2 and 
3 mm. However, when the height was 4 mm, the trend was reversed.

CONCLUSIONS

In mastication, when bearing the vertical force, the retention of the butt-joint marginal endocrown preferred to the shoulder-surrounded one. Given the higher axial wall of the shoulder-surrounded marginal endocrown, it showed better ability to bear the oblique force than the butt-joint one.

[Vital pulp preservation treatment in mandibular right first molar with vertical root fractures: a case report]

This case presents vertical root fracture with vital pulp in mandibular right first molar. Examinations of the history, clinical tests, laser Doppler flowmetry, and radiographs revealed that the tooth showed positive response to electric pulp testing and was normal compared with the healthy control tooth. This study aimed to use a novel vital preserving surgical technique (microapical surgery and nanometer bioactive materials) to make an effective therapeutic decision for the vital tooth with vertical root fracture.

Assessment of the Role of the Mandibular First Molar Tooth in Mandibular Fracture Patterns of 29 Dogs

Mandibular fractures at the level of the first molar tooth (M1) were assessed in 29 dogs. Patients included in this study demonstrated fractures involving the M1 tooth, tooth bud, or alveolus (if tooth was absent). Diagnostic imaging evaluation included intraoral dental radiography and/or computed tomography (CT) with 3D reconstruction. The distal root was involved in 55.2% of cases, mesial root involvement in 34.5% of cases, and the tooth was absent in 10.3% of cases. Fractures were described in the rostral-to-caudal direction. Fractures tended to occur in the caudoventral direction ( P = .057). Cases with CT imaging were also evaluated in the buccolingual direction. Fractures were found to occur significantly more frequently in the caudolingual direction ( P = .022). When classifying fracture patterns along M1 according to a previously published fracture classification system, it was noted that fractures occurred significantly more frequently in either the mesial ( P < .001) or distal ( P < .001) roots by coursing along the periodontal ligament space and communicating with the periapical region. Active or nonworsening periodontitis was described as radiographic or tomographic evidence of (>25%) bone loss in the vertical or horizontal direction. Periodontitis was associated with 7 (24.1%) cases. These results help frame the challenges associated with fracture repair at the M1 location. Treatment planning considerations should include limited structural support caudal to fractures involving the distal root, more frequent involvement of the distal root over the mesial root, risk for poor endodontic prognosis, and the predilection for unfavorable fracture patterns to occur.

Evaluation of Roots and Canal Systems of Mandibular First Molars in a Vietnamese Subpopulation Using Cone-Beam Computed Tomography

Objectives:

The aim of this study is to determine the prevalence of the first lower molars that have two roots or three roots and the number of the root canals of the mandibular first molars in the Vietnamese subpopulation using cone-beam computed tomography (CBCT).

Materials and Methods:

The study was conducted on 166 patients who had CBCT as indicated by dentists in Nguyen Trai Dental CT Center, Ho Chi Minh City using the Picasso Trio (Ewoo Vatech, Korea). The number of root canals of the first lower molars was examined by moving cross-sectional slices from the pulpal floor to the apex. The orifices, middle thirds, and apical thirds of the canals of the first lower molar were observed, and the root canals of each root of the mandibular first molars were observed in three planes.

Results:

The prevalence of two, three, and four root canals of the mandibular first molars was 4.5%, 66.8%, and 28.9%, respectively. For the distal roots of these molars, a classification of Vertucci type I was the most common at a rate of 80.8%–97.6%. Whenever these teeth had three roots, a Vertucci type I was the classification of 100% of distolingual roots.

Conclusion:

Majority of the mandibular first molars has two roots and three canals. CBCT is appropriate equipment useful in investigating the complex root canal morphology of human teeth.

Comparison of three different apex locators in determining the working length of mandibular first molar teeth with irreversible pulpitis compared with an intraoral periapical radiograph: A block randomized, controlled, clinical trial

AIM

The aim of the present study was to assess the clinical accuracy APEX and 0.5 marks of three different apex locators - iPex II, Root ZX, and Apex ID - before and after canal preparation in the mandibular first molar.

METHODS

Sixty patients between the ages of 13-60 years participated in the study. After access gaining and canal preparation stages files were inserted with the apex locator clip attached until the electronic apex locators (EALs) shows readings of APEX and 0.5 marks and same is confirmed with periapical radiographs. Eighteen apex locator readings were recorded from each tooth, and 1080 readings were obtained from the 60 patients.

RESULTS

Differences among readings from apex locators and radiographic readings were assessed using paired t test. Only in two patients (1 male and 1 female) were the APEX mark readings different from the radiograph estimation. When the 0.5 mark readings of three different EALs were compared with each other, we could observe that the readings from Root ZX differed significantly (P < 0.05).

CONCLUSIONS

In the present study, we observed the negligible differences in readings between the EAL at the APEX mark readings, coinciding with the radiographic observation. Clinically, we recommend the apical foramen be located with the apex locators' APEX mark readings prior to identifying the apical constriction position.

A deep-learning artificial intelligence system for assessment of root morphology of the mandibular first molar on panoramic radiography

OBJECTIVES:

The distal root of the mandibular first molar occasionally has an extra root, which can directly affect the outcome of endodontic therapy. In this study, we examined the diagnostic performance of a deep learning system for classification of the root morphology of mandibular first molars on panoramic radiographs. Dental cone-beam CT (CBCT) was used as the gold standard.

METHODS:

CBCT images and panoramic radiographs of 760 mandibular first molars from 400 patients who had not undergone root canal treatments were analyzed. Distal roots were examined on CBCT images to determine the presence of a single or extra root. Image patches of the roots were segmented from panoramic radiographs and applied to a deep learning system, and its diagnostic performance in the classification of root morphplogy was examined.

RESULTS:

Extra roots were observed in 21.4% of distal roots on CBCT images. The deep learning system had diagnostic accuracy of 86.9% for the determination of whether distal roots were single or had extra roots.

CONCLUSIONS:

The deep learning system showed high accuracy in the differential diagnosis of a single or extra root in the distal roots of mandibular first molars.

[Mandibular first molar with C-shaped root canal system: a two-case report]

The root and canal anatomy of the mandibular first molar is highly complicated. A mandibular first molar with a C-shaped root canal system is rare. This article describes two different cases of this system. Case 1 has a complete C-shaped fused root. The root canal is characterized by a mesial lingual root canal and a C-shaped fused root canal. Case 2 has a C-shaped fused root in the buccal region and a distal lingual root. The root canal is characterized by a type Ⅱ-Ⅰroot canal in the buccal region and a distal lingual root canal.

Micro-computed tomographic evaluation of the effect of the final apical size prepared by rotary nickel-titanium files on the removal efficacy of hard-tissue debris

Objective

This study was performed to compare the removal efficacy of hard-tissue debris in mandibular first molars prepared to various apical sizes.

Methods

The mesial root canals of 40 extracted mandibular first molars were prepared by rotary nickel-titanium files to an apical size of #25/0.04 (Group #2504), #30/0.04 (Group #3004), #35/0.04 (Group #3504), and #40/0.04 (Group #4004). Irrigation was performed with 5.25% NaOCl and 17% EDTA. Micro-computed tomography was used to scan the samples before and after root canal preparation. Remnant hard-tissue debris was identified, quantified, and visualized three-dimensionally using shape recognition and image superimposition analysis, and the debris was mapped to its location.

Results

After preparation, 11.67%±2.99% of the root canals contained hard-tissue debris in Group #2504, 8.00%±2.71% in Group #3004, 7.17%±2.88% in Group #3504, and 4.51%±1.61% in Group #4004. The amount of accumulated hard-tissue debris was significantly less in Group #4004 than in the other groups. However, there were no significant differences between Groups #3004 and #3504.

Conclusions

An increased final apical size resulted in significantly lower debris accumulation. However, no root canal in any group was completely free from hard-tissue debris, and debris was mostly found in the isthmus of the mesial root canals.

Rare case of a mandibular first molar with seven canals confirmed by cone beam computed tomography and its endodontic management

The endodontic treatment of a mandibular molar with aberrant canal configuration can be diagnostically and clinically challenging. This case report presents the treatment of a mandibular first molar with seven root canals, of which four canals were located in the mesial root and three in distal root. This case presents a rare anatomic configuration and points to the importance of expecting and searching for additional canals.

Cone-beam computed tomographic analysis of middle mesial canals and isthmus in mesial roots of mandibular first molars-prevalence and related factors

Context:

The internal anatomy of mandibular first molars has been studied in depth in different populations. However, limited information is present in differentiating a true middle mesial (MM) canal from an isthmus.

Aims:

The primary aim of this study was to identify the prevalence of a true MM canal and isthmus by retrospectively analyzing cone-beam computed tomography (CBCT) images in vivo. The secondary aim was to determine any correlation between related factors such as sex and age.

Materials and Methods:

CBCT images of 130 patients with the age group of 13–70 years were selected. Findings of MM canals and isthmus were recorded along with variables such as age and sex. Prevalence was compared using the Chi-square test (P < 0.05).

Results:

Out of 143 mandibular first molars, the prevalence of the MM canal was 18.2%. There was no statistically significant difference between sex and prevalence of the MM canal and isthmus. The prevalence of isthmi in the mesial roots was 78.4%. Their presence was significantly higher in the apical third area (37.1%) (P < 0.05). Both MM canal and isthmus were seen significantly higher in the age group of 31–50 years (P < 0.05).

Conclusions:

This study showed a high prevalence of MM canals (18.2%) and isthmus (78.4%). The prevalence of the MM canal and isthmi was significantly higher in the middle age groups. This knowledge may direct the clinicians in locating them leading to good endodontic prognosis.

Anatomical profile of the mesial root of the Burmese mandibular first molar with Vertucci's type IV canal configuration

This study evaluated the anatomical profile of the mesial root canals of the Burmese mandibular first molar with Vertucci's type IV canal configuration (VT4) using microcomputed tomography analysis. Seventy-five mesial roots of extracted mandibular first molars were scanned and evaluated. Fourteen middle mesial canals (MMCs) were observed in the specimens; each specimen had an average of 1.63 lateral canals and 3.77 apical foramina. The lateral canals arising from the mesiobuccal canal, mesiolingual canal, MMC, and isthmus terminated at an average distance of 0.92, 0.73, 2.11, and 1.89 mm, respectively, from the apex. The mean distance between the centers of the mesiobuccal and mesiolingual canals at 1.5 mm coronal to the furcation was 2.60 mm. A higher incidence of isthmus was observed in the apical 2-6-mm region compared with the apical 0-2-mm region (P < 0.05). The incidence of lateral canals in the isthmus was similar to that of the mesiobuccal and mesiolingual canals (P > 0.05). This study shows that the mesial root of the Burmese mandibular first molar with VT4 has complex anatomical profiles comprising MMCs and isthmus and their lateral canals.

Endodontic management of contralateral mandibular first molars with six root canals

The knowledge of variations in root canal morphology is essential for a successful endodontic outcome. Contralateral mandibular molar with six root canals is a rare entity. Root canal treatment of mandibular molars with aberrant canal configuration can be diagnostically and technically challenging. While dealing with variant mandibular molars, mishaps may happen. This case report describes variations in contralateral mandibular molars and also an endodontic mishap while managing them.

A Cone-beam Computed Tomographic Study of Apical Surgery-related Morphological Characteristics of the Distolingual Root in 3-rooted Mandibular First Molars in a Chinese Population

INTRODUCTION

Apical surgery on the separate distolingual (DL) root of a 3-rooted mandibular first molar is thought to be difficult because DL roots are always severely curved, small, and shorter than distobuccal (DB) roots, and they are located far from the buccal cortical bone. The purpose of this study was to use cone-beam computed tomographic images to investigate the apical surgery-related morphological characteristics of DL roots in a Chinese population.

METHODS

The screening process identified 83 subjects with 128 mandibular first molars with separate DL roots. The degree of root canal curvature was measured in the mesiodistal (MD) and buccolingual (BL) planes using the Schneider method. Distances were measured from the DL root apex to the buccal cortical bone, to the buccal cortical bone opposite the DB root apex, and to the buccal cortical bone opposite the mesiobuccal (MB) root apex. The lengths of the remaining DB, MB, and DL roots were measured after resection of 3 mm of the DL apical root. Angulations of the DL root canal were determined before and after DL apical root resection.

RESULTS

The teeth were classified into 3 types: type I, straight in the MD and BL planes; type II, straight in the MD plane and curved in the BL plane; and type III, curved in the MD and BL planes. Only 5 molars (3.9%) were classified as type I, whereas 52 (40.6%) molars were type II and 71 (55.5%) molars were type III. The type I DL root has a significantly shorter length and longer distance from the DL root apex to the buccal cortical bone than type II and III roots (P < .05). The distance from the DL root apex to the buccal cortical bone opposite the MB root apex is significantly longer than the distance to the buccal cortical bone opposite the DB root apex in types I and II (P < .05), whereas the distance is nearly equal for type III. The angulations for root-end preparation of types II and III DL roots vary from 57.5° to 129.1° and from 55.8° to 128.1°, respectively.

CONCLUSIONS

A new classification was proposed for DL roots in 3-rooted mandibular first molars based on the root canal curvature. Type I is unsuitable for apical surgery. Access to the type II DL root apex should be through the DB root apex, whereas access to the type III DL root apex through the MB root apex is more feasible. Apical surgery on types II and III DL roots may be accomplished when the depth of the root-end preparation is reasonably reduced, and fine and personalized angulated ultrasonic retro tips are used.

Endodontic management of mandibular first molars with mid mesial canal: A case series

The purpose of this study is to demonstrate the importance of knowledge of the internal anatomy of root canals for the success of endodontic treatment. Lack of knowledge of anatomic variations and their characteristics in different teeth has been pointed out as one of the main cause of endodontic therapy failure. Dental operating microscope plays a key role in the identification of canal and success of endodontic treatment. This case series describes the endodontic treatment of mandibular first molars with extra root canals, evaluate the occurrence of this extra canal, and discuss the importance of their identification and treatment.

[Clinical application of cone beam computed tomography combined with micro-ultrasound technique in treating three mesial canals in mandibular first molars]

Objective The aim of this study is to investigate the influence of cone beam computed tomography (CBCT) and micro-ultrasound technique for the treatment of three mesial canals in mandibular first molars. The three mesial canals according to Pomeranz's classification were characterized. Methods A total of 75 permanent mandibular first molars for root canal treatment were randomly selected from patients belonging to the age group of 14-60 years. After preparing the access cavity and locating the main canals, the middle mesial canal orifices in all teeth were determined with an endodontic explorer under direct vision (StageⅠ), under magnification with the aid of micro-ultrasound (Stage Ⅱ), and with the combined use of CBCT and micro-ultrasound to remove the dentin wall and calcifications (Stage Ⅲ). Results Middle mesial canals were detected in 4.0%, 18.7%, and 22.7% of the teeth in StagesⅠ-Ⅲ, respectively. Statistical analysis showed significant differences (P<0.05) between StagesⅠand Ⅱ with regard to middle mesial canal detection. The number of Stage Ⅲ was more than that of Stage Ⅱ. The difference between the two stages was no significant. Among the 17 middle mesial canals, "confluent", "fin" and "independent" anatomies were 52.9%, 35.3%, and 11.8%. Conclusion When used with adjunctive aids, including CBCT, micro-ultrasound facilitates dental clinicians in the location and treatment of middle mesial canals.

A micro-computed tomography study of the negotiation and anatomical feature in apical root canal of mandibular molars

The aim of this study was to investigate the clinical negotiation of various apical anatomic features of the mandibular first molars in a Chinese population using micro-computed tomography (micro-CT). A total of 152 mandibular first molars were scanned with micro-CT at 30 µm resolution. The apical 5 mm of root canal (ARC) was reconstructed three dimensionally and classified. Subsequently, the access cavity was prepared with the ARC anatomy blinded to the operator. The ARC was negotiated with a size 10 K file with or without precurve. Information on the ability to obtain a reproducible glide path was recorded. The anatomical classification of ARC was Type I with 68.45% in mandibular first molars. The negotiation result of ARC with Category i was 387 canals (74.00%). With a bent negotiating file, 96 canals were negotiated, including 88 reproducible glide paths (Category ii) and 8 irregular glide paths (Category iii). About 7.65% canals could not be negotiated with patency successfully (Category iv). The statistical analyze shown the anatomic feature of ARC had effect on the negotiation of ARC (p < 0.05). In conclusion, ARC anatomic variations had a strong potential impact on the negotiation. The category of negotiation in ARC would be helpful in the using of NiTi rotary instruments. Negotiation of ARC to the working length with patency should be careful and skillful because of the complexities of ARC. SCANNING 38:819-824, 2016. © 2016 Wiley Periodicals, Inc.

Endodontic management of mandibular first molar with seven canals using cone-beam computed tomography

The endodontic treatment of a mandibular molar with aberrant canal configuration can be diagnostically and clinically challenging. Successful endodontic therapy thus depends on the clinician's ability to anticipate and look for these aberrant variations. A mandibular first molar with seven canals represents a rare anatomical variant, particularly when four canals are found in distal root. Based on in vitro studies, its incidence is reported to be between 0.2% and 3%. With the advent of cone-beam computed tomography (CBCT) as an adjunctive diagnostic aid, the determination of root canal anatomy in teeth with complex canal configurations has become more precise. The present case report discusses successful nonsurgical management of radix entomolaris along with middle mesial canal and middle distal canal in mandibular first molar with seven canals (four canals in distal and three in mesial) employing CBCT as an adjunctive diagnostic aid to conventional radiography.

Crown morphology of the mandibular first molars with distolingual roots

Background/purpose

Most mandibular first molars have two roots. A major common variation of this tooth is the presence of a distolingual root, which is a common Mongoloid trait in certain populations. The aim of this article was to examine crown morphology in relation to the presence of the distolingual root.

Materials and methods

Using dental casts, the crown morphology of 141 mandibular first molars from 71 Taiwanese individuals was analyzed. Periapical radiographs were used to detect distolingual roots. The length and width of the crowns and the crown units (i.e., trigonid and talonid) were measured. Ten intercuspal distances and five cusp angles were examined.

Results

The buccolingual dimension of the crown and its ratio to the mesiodistal dimension were significantly increased in molars with a distolingual root, compared to molars without a distolingual root. Mesiodistal crown dimensions were similar; however, the crown unit dimensions were different: molars with a distolingual root had a shorter mesiodistal trigonid dimension but a longer talonid dimension, compared to molars without a distolingual root. The intercuspal distances from the three buccal cusps to the distolingual cusp were significantly longer, however, the distance between the mesiobuccal cusp and mesiolingual cusp was significantly shorter in teeth with a distolingual root than in teeth without a distolingual root. A significantly wider mesiolingual angle and narrower distolingual angle were observed in molars with a distolingual root, compared to molars without a distolingual root.

Conclusion

The presence of a distolingual root significantly increased the buccolingual dimension of the crown and the location of distolingual cusp is significantly closer to the lingual side.

Root Canal Morphology and Configuration of 118 Mandibular First Molars by Means of Micro-Computed Tomography: An Ex Vivo Study

INTRODUCTION

The aim of this study was to investigate the root canal system morphology of the mandibular first molar by means of micro-computed tomography.

METHODS

The root canal configuration, foramina, and accessory canals frequency of 118 mandibular first molars were investigated by means of micro-computed tomography and 3-dimensional software imaging. A 4-digit system describes the root canal configuration from the coronal to apical thirds and the main foramina number.

RESULTS

The most frequent root canal configurations in mesial root were 2-2-2/2 (31.4%), 2-2-1/1 (15.3%), and 2-2-2/3 (11.9%); another 24 different root canal configurations were observed in this root. A 1-1-1/1 (58.5%), 1-1-1/2 (10.2%), and 16 other root canal configurations were observed in the distal root. The mesiobuccal root canal showed 1-4 foramina in 24.6%, and the mesiolingual showed 1-3 foramina in 28.0%. One connecting canal between the mesial root canals was observed in 30.5% and 2 in 3.4%. The distolingual root canal showed 1-4 foramina in 23.7%, whereas a foramen in the distobuccal root canal was rarely detected (3.4%). The mesiobuccal, mesiolingual, and distolingual root canals showed at least 1 accessory canal (14.3, 10.2, and 4.2%, respectively), but the distobuccal had none.

CONCLUSIONS

The root canal configuration of mandibular first molars varies strongly. According to our expectations, both the mesial and distal roots showed a high number of morphologic diversifications. The root canal system of the mesial root showed more root canal configuration variations, connecting and accessory canals than the distal root.

Evaluation of three obturation techniques in the apical third of mandibular first molar mesial root canals using micro-computed tomography

Background/purpose

Recent studies have demonstrated a high incidence of isthmuses in mandibular first molar mesial roots, and intratubular mineralization following mineral trioxide aggregate obturation. This study assessed the filling quality of three obturation techniques in the apical 5 mm of mandibular first molar mesial root canals.

Materials and methods

Sixty extracted human mandibular first molar mesial roots with two separate canals that had interconnecting isthmuses, were prepared to an apical size of 40/0.06. They were allocated to three groups of 20 roots for obturation by either cold lateral compaction (CLC) or the continuous wave of condensation (CW) that used gutta-percha and AH Plus sealer, or by an orthograde canal obturation using OrthoMTA. The obturated roots were scanned by micro-computed tomography and assessed for the volumetric ratio (%) of gutta-percha, sealer, and OrthoMTA within the main canals or isthmuses in the apical 5 mm area. Measurements were analyzed statistically for differences among three obturation techniques.

Results

In the main canals, filled volume ratios were not significantly different among groups. Within isthmuses, the filled volume ratio for CLC was lower than in CW (P = 0.025) or OrthoMTA (P = 0.002). In isthmuses, the gutta-percha volume ratio in CLC was lower than in CW (P = 0.005), although the sealer volume ratio was higher than in CW (P = 0.049).

Conclusion

CLC demonstrated lower filling densities in isthmuses in the apical region than either CW or OrthoMTA. Orthograde MTA obturation showed comparable filling quality to gutta-percha with sealer.

Endodontic management of a mandibular first molar with six root canal systems

Internal anatomy of pulp is complex. The first mandibular molars typically have two roots, one mesial with two root canals and another distal root, which contains one or two canals. A 20-year-old female patient reported with intermittent pain and incomplete root canal treatment in left lower back region since 1-week. Refined access cavity revealed initially two canals in mesial and two canals in the distal root. With operating microscope and cone beam computerized tomography, two additional canals (L-mesio-buccal and B-mesio-lingual) were identified in mesial root. One-year follow-up showed patient was asymptomatic and complete healing of periapical radiolucency.

Comparison of mandibular first molar mesial root canal morphology using micro-computed tomography and clearing technique

OBJECTIVE

Micro-computed tomography (MCT) with alternative image reformatting techniques shows complex and detailed root canal anatomy. This study compared two-dimensional (2D) and 3D MCT image reformatting with standard tooth clearing for studying mandibular first molar mesial root canal morphology.

MATERIALS AND METHODS

Extracted human mandibular first molar mesial roots (n=31) were scanned by MCT (Skyscan 1172). 2D thin-slab minimum intensity projection (TS-MinIP) and 3D volume rendered images were constructed. The same teeth were then processed by clearing and staining. For each root, images obtained from clearing, 2D, 3D and combined 2D and 3D techniques were examined independently by four endodontists and categorized according to Vertucci's classification. Fine anatomical structures such as accessory canals, intercanal communications and loops were also identified.

RESULTS

Agreement among the four techniques for Vertucci's classification was 45.2% (14/31). The most frequent were Vertucci's type IV and then type II, although many had complex configurations that were non-classifiable. Generally, complex canal systems were more clearly visible in MCT images than with standard clearing and staining. Fine anatomical structures such as intercanal communications, accessory canals and loops were mostly detected with a combination of 2D TS-MinIP and 3D volume-rendering MCT images.

CONCLUSIONS

Canal configurations and fine anatomic structures were more clearly observed in the combined 2D and 3D MCT images than the clearing technique. The frequency of non-classifiable configurations demonstrated the complexity of mandibular first molar mesial root canal anatomy.

Endodontic treatment of mandibular molars with atypical root canal anatomy: reports of 4 cases

The variations in root canal anatomy of multirooted teeth represent a continuous challenge to endodontic diagnosis and treatment. Although the most common configuration of mandibular molars is one containing 2 roots and 3 root canals, there are many different combinations. Very rarely, an additional third (supernumerary) root is seen. When it is located distolingually to the main distal root, this third root is called radix entomolaris (RE), and when it is located mesiobuccally to the mesial root, it is called radix paramolaris (RP). Variations of root canal systems need not always be in the form of extra roots or extra canals. Single roots with single canals can also occur. A general dentist should be aware of these unusual root canal morphologies in mandibular molars for the success of endodontic treatment. These case reports describe the root canal treatment of a case of RE in the mandibular first molar, 2 rare cases of RP (1 each in the mandibular first and second molars), and a mandibular second molar with a single root and root canal.

Single C-shaped canal in mandibular first molar: A case report

The variability of root canal system morphology presents a continuous challenge to endodontic diagnosis and therapeutics. There have been reports of teeth with multiple roots and canals as also those with lesser number of root and root canals. Variations of root canal systems need not always be in the form of extra canals. Clinicians should be aware that there is a possibility of existence of fewer numbers of roots and root canals than normal, which presents varied canal anatomy and poses a challenge to the clinician's expertise. This case report deals with the management of an unusual case of C-shaped canal in mandibular molar with two buccally fused roots. Cone-beam computed tomography (CBCT) was employed to confirm the extension of the unusual anatomy. The Self Adjusting File (SAF) system was used to ensure complete cleaning of the canal system. One-year follow-up of the case showed good healing. The clinician should expect to encounter unusual features when performing endodontic treatment. Use of diagnostic aids like CBCT, improved magnification with dental operating microscope, and the use of novel file systems like SAF ensure success.

Surgical removal of fractured endodontic instrument in the periapex of mandibular first molar

The purpose of this article is to present the surgical removal of a broken endodontic file from the periapical region of the distal root of a mandibular first molar. The methods of diagnosis and measurement of the distance of the instrument to the adjacent vital structures in the periapical region was done with simple means and in an economical manner.

Prevalence of cusp 7 in permanent mandibular first molars in an Indian population: a comparative study of variations in occlusal morphology

AIM

The aims of the present study were to determine the prevalence of cusp 7 in permanent mandibular first molars in an Indian population, and to comparatively evaluate the variations in occlusal morphology of these teeth, including the difference in the number of cusps and fissure patterns.

METHODS

A total of 1123 Indian participants from the Government College of Dentistry, Indore, Madhya Pradesh, India, were selected for the study. For the analyses of cusp 6 and cusp 7 in permanent mandibular first molars, the Arizona State University Dental Anthropology System was used. Groove patterns were analyzed and classified as Y, +, X, and Ұ.

RESULTS

Of the 1123 individuals, 132 (11.75%) were found to have cusp 7, while 78 (6.95%) had cusp 6. Thus, a total of 210 participants had the six-cusped mandibular first molars, 98 (8.73%) had the four-cusped mandibular first molars, and two had the seven-cusped variant. Overall, the most common fissure pattern was the Y pattern (50.36%), while the least common was the X pattern (1.25%). Mandibular first molars with cusp 7 demonstrated a highly significant (P < 0.05) dominance of the Ұ pattern (36.80%) over the Y (30.74%), + (27.71%), and X (4.46%) fissure patterns.

CONCLUSION

A significant prevalence of cusp 7 (11.25%) in permanent mandibular first molars was found in the present study in an Indian population.

Mandibular first molar with three distal canals

With the increasing number of reports of aberrant root canal morphology, the clinician needs to be aware of the variable anatomy. Various case reports have been published with the finding of middle mesial canal in mandibular first molar, however finding of middle distal canal in distal root of mandibular first molar is rare. This case report describes root canal treatment of two rooted mandibular first molar with five root canals (three in distal and two in mesial root), and Sert and Bayirli Type XVIII canal configuration in distal root.

Endodontic management of permanent mandibular left first molar with six root canals

The endodontic treatment of a mandibular molar with aberrant canal configuration can be diagnostically and clinically challenging. This case report presents the treatment of a mandibular first molar with six root canals, of which three canals were located in the mesial root and three in distal root. Third canals were found between the two main root canals. This case presents a rare anatomic configuration and points to the importance of expecting and searching for additional canals.

Spiral computed tomographic evaluation and endodontic management of a mandibular first molar with three distal canals

The use of spiral computed tomography serves as a boon in endodontic diagnosis of complex anatomic variations. The present case demonstrates the spiral tomographic evaluation and endodontic management of a mandibular first molar with 5 canals (2 mesial and 3 distal canals), which is a very rare anatomic variant. Such anatomic variations should be taken into account in day to day endodontic practice to ensure a high degree of clinical success.

Canal complexity of a mandibular first molar

The endodontic treatment of a mandibular molar with aberrant canal configuration can be diagnostically and technically challenging. This case report presents the treatment of a mandibular first molar with five root canals, of which three were located in the mesial root. A third canal was found between the mesiobuccal and mesiolingual root canals. The morphological pattern of separate apical terminations of three mesial root canals with separate orifices, as manifested in this case, is a rare one.

Root canal morphology of human mandibular first permanent molars in an Iranian population

Background and aims

The knowledge of variations in root canal morphology is critical for a successful endodontic treatment. The purpose of this study was to investigate variations in the root canal system of human mandibular first permanent molars in an Iranian population.

Materials and methods

In this study, 209 mandibular first molar teeth were decalcified, dye-injected, and cleared in order to determine the number and configuration of the root canals.

Results

The results demonstrated that 65.56% of the mandibular first molars under study had three, 31.57% had four and 2.87% had two canals.

Conclusion

According to the results of this study and considering variations in the root canal systems of the mandibular first molars, it seems that great care should be taken in the root canal treatment of these teeth.