Three-dimensional morphological analysis of C-shaped canals in mandibular first premolars in a Chinese population

Prevalence and morphology of different root canal systems in mandibular premolars: a cross-sectional observational study

BACKGROUND

This study investigated the prevalence and morphology of C-shaped and non-C-shaped root canal systems in permanent mandibular first (PM1) and second (PM2) premolars using retrospective analysis of cone-beam computed tomography (CBCT) scans, and panoramic radiographs.

METHODS

CBCT scans from 2000 patients were screened for the presence of premolars with C-shaped canals and then assessed at three axial levels to determine the canal classification. The teeth were also assessed for Vertucci configuration, number of roots, and radicular grooves. Pre-existing panoramic radiographs were evaluated to identify features specific to PM1/2 with multiple canals or C-shaped anatomy.

RESULTS

A total of 1576 PM1 and 1424 PM2 from 880 patients were evaluated. The overall prevalence of C-shaped canals was 2.2% (3.3% PM1, 1.0% PM2), with 49 (5.6%) patients presenting with at least one C-shaped mandibular premolar. There were 2.3 ± 0.6 and 2.4 ± 0.5 different classifiable cross-sections per tooth for PM1 and PM2, respectively. The sudden disappearance or bifurcation of a canal on panoramic radiographs was associated with the presence of multiple canals (P < 0.001) or C-shaped anatomy (P = 0.03).

CONCLUSIONS

There was substantial variation in cross-sectional anatomy within and between C-shaped premolars, which will affect endodontic treatment planning. © 2023 Australian Dental Association.

Uncovering the Enigma of the C-shaped Root Canal Morphology

A C-shaped canal describes an anatomical configuration of a tooth's root canal that resembles the alphabet C when viewed occlusally in a prepared access cavity. In the second molar of the maxillary arch, the root canals unite into a single, continuous, extensive root canal morphology to form a C-shaped canal. The natural crevices found in tooth roots where blood vessels and nerves are housed are called root canals. The frequently referred etiology resulting in the development of the C-shaped canal arrangement is the inability of Hertwig's epithelial root sheath to undergo fusion. The occurrence of the C-shaped canal anatomic variation varies among populations, with the majority of cases occurring in mandibular second molars. C-shaped canals pose several challenges in endodontic treatment such as in their diagnosis, biomechanical preparation, debridement, and obturation. Nevertheless, the desired result can be achieved with relative ease if one has a solid grasp of the different root canal configurations and uses the relevant clinical expertise. Therefore, three-dimensional radiography is utilized to help identify and negotiate C-shaped canals by enabling three-dimensional reconstruction of the root canal system. Efficient C-shaped canal configuration treatment may be attained using hand-driven and rotary instruments assisted by sonic or ultrasonic hand-pieces. Four alternative gutta-percha filling methods are used in C-shaped canals: core-carrier, ultrasonic compaction, cold lateral compaction, and single cone with injectable gutta-percha. The core-carrier technique is the most efficient obturation technique in the C-shaped canal. Calcium silicate materials (CSMs) are also used for the obturation of C-shaped canals. The most frequently used CSMs are mineral trioxide aggregate and biodentine.

CBCT and Micro-CT analysis of the mandibular first premolars with C-shaped canal system in a Chinese population author

OBJECTIVES

The purpose of this study was to survey the prevalence of C-shaped root canal system in mandibular first premolar in Chinese population by reading Cone-beam computed tomography (CBCT) images and to analyze its anatomical characteristics by CBCT and Micro-computed tomography (Micro-CT).

METHODS AND MATERIALS

The prevalence and the morphologic features of C-shaped root canal system were evaluated by observing CBCT images of 760 patients (1520 mandibular first premolars). 66 mandibular first premolars with C-shaped root canal system were scanned by Micro-CT. The morphologic features including radicular groove, C-shaped root canal categories in the cross-sections and in the 3D models, accessory and connecting canals, apical foramina and accessory foramina, were analyzed using image software.

RESULTS

C-shaped root canal system was identified in 16.9% of mandibular first premolars. The minimum mesial wall thickness most commonly occurred at the lingual site (69.7%). Regarding to the cross-sectional classification, the maximum was C2 (41.5%). In the 3D classification, the most common was S (34.8%). Accessory canals were observed in 36.4% of the samples and occurred mostly in the middle and apical regions. 42.4% samples had 1-3 variable connecting canals, and 40.9% samples had only one apical foramen.

CONCLUSIONS

The incidence of C-shaped root canal system in mandibular first premolars was 16.9% in the Chinese population. The anatomy was very complex and variable, mostly distributed in the middle and apical regions of the root canal. The mesial wall of C-shaped canal was extremely thin on the lingual side.

Prevalence and correlation of C-shaped root canals of mandibular premolars and molars in Eastern Chinese individuals

The aim of this study was to investigate the prevalence, correlation, and differences of C-shaped root canals (CSRCs) morphology in permanent mandibular premolars and molars in Eastern Chinese individuals using cone-beam computed tomography (CBCT). A total of 8000 mandibular first premolars (MFPs), mandibular second premolars (MSPs), mandibular first molars (MFMs), and mandibular second molars (MSMs) CBCT images from 1000 patients (692 females and 308 males) were collected. The prevalence, correlation, bilateral/unilateral presence, the morphology of CSRCs, level of canal bifurcation, gender differences, and location of radicular grooves (RGs) were evaluated. The prevalence of CSRCs in MFPs, MSPs, MFMs and MSMs were 10.25%, 0.25%, 0.55% and 47.05%, respectively. The prevalence of CSRCs in MFPs of males was higher than that in females, while the prevalence of CSRCs in MSMs of females was higher than that in males (P < 0.05). The bilateral symmetry presence of CSRCs in MSMs was significant but not in MFPs, MSPs, and MFMs. RGs were predominantly found on the mesiolingual (ML) surface of premolars and the lingual surface of molars. There was a high prevalence of CSRCs in MFPs and MSMs in the Eastern Chinese population, but there was no correlation. The prevalence of CSRCs in MFPs and MSMs differ significantly by gender (P < 0.05).

A micro-CT analysis of radicular dentine thickness in mandibular first premolars presenting C-shaped root canals: Identification of potential danger zones

AIM

To describe the radicular dentine thickness in mandibular first premolars presenting C-shaped root canals, in order to identify the canal walls with less thickness as potential danger zones. In addition, to describe the internal and external anatomical characteristics of these teeth and to associate them to the dentine thickness.

METHODOLOGY

A total of 70 mandibular first premolars presenting C-shaped root canals were examined. Their internal morphology was analyzed using Vertucci´s and Fan´s criteria, and their external morphology was analyzed using the ASUDAS score. Besides, the dentine thickness around the root canals was two/three-dimensionally determined at five root planes and quantified in the distal and the mesial aspects.

RESULTS

According to Fan´s, ASUDAS, and Vertucci´s classifications, the most common canal configurations were category C3, grade 3, and type V, respectively. In Vertucci's type III anatomy, the mesial root wall of the lingual canal showed significantly less dentine thickness than the distal wall in the middle plane (p = 0.031). Similarly, in Vertucci's type V anatomy, significantly less dentine thickness was observed in the mesial root wall of the buccal and lingual canals in the middle plane (p < 0.001) and the buccal canal in the middle-apical plane (p = 0.014) than the distal root wall of these canals. In teeth with ASUDAS grade 3 and 4 scores, significantly less dentine thickness was observed in the mesial in comparison with the distal root wall of these canals. These differences were demonstrated in the middle and middle-apical planes (p < 0.001) of grade 3 teeth and the middle-apical plane (p < 0.001) of grade 4 teeth. In these root planes, the Ver1-AS3 and VerV-AS3 combinations presented a 4-times greater risk of presenting walls with a critical dentine thickness of 0.6 mm (OR=4, p = 0.025) than the combinations Ver1-AS2, VerV-AS2, VerV-AS4, and VerIII-AS3.

CONCLUSIONS

The root canal system configuration of mandibular first premolars with C-shaped canals showed a wide range of anatomical variations. The lowest dentine thickness was located in the mesial wall of the canals in the middle and apical root thirds of Vertucci´s type III and V anatomies and in teeth with deep radicular grooves scored as ASUDAS grade 3 and 4. In the middle and middle-apical planes, the presence of the combinations Ver1-AS3 and VerV-AS3 showed a high risk of presenting a critical dentine thickness of 0.6 mm. Therefore, these root canal walls with less dentine thickness represent potential instrumentation danger zones in mandibular first premolars with C-shaped canals.

Normal Variants of the Oral and Maxillofacial Region: Mimics and Pitfalls

A normal variant is defined as an incidental, often asymptomatic, imaging finding that mimics a true pathologic condition. Given the complex anatomy and wide variety of normal variants in the oral and maxillofacial region, a thorough understanding of commonly encountered normal variants in this region is essential to avoid misinterpretation and unnecessary further imaging or interventions. Moreover, familiarity with normal variants that are known to become symptomatic at times is necessary to facilitate further workup and guide the treatment plan. Intraoral radiography and panoramic radiography, which are unique to oral and maxillofacial radiology, provide two-dimensional (2D) images. Hence, the overlapping of structures or the displacement of the tomographic layer on images can confuse radiologists. It is crucial to understand the principle of 2D imaging to avoid being confused by ghost images or optical illusions. In addition, understanding the normal development of the maxillofacial region is essential when interpreting maxillofacial images in children or young adults because the anatomy may be quite different from that of mature adults. Knowledge of changes in the jaw bone marrow and each tissue's growth rate is essential. It is also necessary to know when the tooth germ begins to calcify and the tooth erupts for diagnostic imaging of the maxillofacial region. The authors describe imaging findings and clinical manifestations of common normal variants in the oral and maxillofacial region, divided into four parts: the maxilla, mandible, tooth, and temporomandibular joint, and discuss the imaging approach used to differentiate normal variants from true pathologic conditions. Online supplemental material is available for this article. ^©RSNA, 2022.

Evaluation of mesial root canal configuration of mandibular first molars using micro-computed tomography

Purpose

The aim of this study was to evaluate the root canal morphology of mesial roots of mandibular first molars.

Materials and Methods

Forty extracted mandibular first molars were used in this study. The morphological examination of root canals was conducted in accordance with the Vertucci classification using micro-computed tomography (micro-CT). Any aberrant root canal configurations not included in the Vertucci classification were recorded, and their frequency was established using descriptive statistics. Intra-observer reliability was assessed using the Wilcoxon signed-rank test, while inter-observer reliability was assessed using the Cohen kappa test. Significance was evaluated at the P<0.05 level.

Results

The mesial roots of mandibular first molars had canal configurations of type I (15%), type II (7.5%), type III (25%), type IV (10%), type V (2.5%), type VI (7.5%), and type VII (7.5%). The images showed 10 (25%) additional configuration types that were not included in the Vertucci classification. These types were 1-3-2-3, 1-2-3-2-3, 2-3-1, 2-3, 1-2-3-1, 2-1-2-3, 3-2-1, 1-2-3-1, 2-3-2-3, and 1-2-1-2-1. The intra-observer differences were not statistically significant (P>0.05) and the kappa value for inter-observer agreement was found to be 0.957.

Conclusion

Frequent variations were detected in mesial roots of mandibular first molars. Clinicians should take into consideration the complex structure of the root canal morphology before commencing root canal treatment procedures to prevent iatrogenic complications. Micro-CT was a highly suitable method to provide accurate 3-dimensional visualizations of root canal morphology.

Assessment of C-Shaped Canal Morphology in Mandibular and Maxillary Second Molars in an Iraqi Subpopulation Using Cone-Beam Computed Tomography

Endodontic treatment is basically dependent on knowledge of the root canal anatomy. The goal of this study was to use cone-beam computed tomography (CBCT) imaging to examine the C-shaped canal configuration of mandibular and maxillary second molars in an Iraqi subpopulation. The prevalence and configurations of C-shaped canals were evaluated in 368 mandibular second molars and 369 maxillary second molars using CBCT scans. The effects of gender, age, and unilateral/bilateral on the presence of C-shaped canals were investigated. Chi-square and Fisher's exact tests were used to determine the level of significance (p ≤ 0.05), and kappa value was used to check reliability of results of the research. In mandibular second molars, the prevalence of C-shaped canals was 17.4%. The prevalence was significantly higher in females (23%) than males (10.4%) using the chi-square test. There is no significant difference in the prevalence of C-shaped canal depending on age and tooth position. The C2 type was the most common (56.3%). This prevalence did not differ with gender, age, or tooth position. In maxillary second molars, C-shaped canals were present in 7.9%. Type I (subtype C) (fusion of 2 root canals MB-DB) was the most common type of fused root (65.5%). There is no significant difference in the prevalence of C-shaped canal depending on the type of fused root, age, and tooth position. The majority of C-shaped canals in mandibular second molars were bilateral in both genders, but unilateral presence was more common in maxillary second molars in both genders. Within the limits of this study, C-shaped canals were found to be more common in mandibular second molars than in maxillary second molars in an Iraqi subpopulation.

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.

Cone-beam computed tomography evaluation of C-shaped root and canal morphology of mandibular premolars

BACKGROUND

Mandibular premolars are complicated teeth to endodontically treat due to the anatomical variations that can present. The purpose of this study was to determine the presence of C-shaped configurations in mandibular premolars by cone-beam computed tomography (CBCT).

METHODS

380 mandibular first premolars and 308 mandibular second premolars cone-beam computed tomographic images were obtained from 292 patients (175 female and 117 male). Tooth position, number of roots, root canals, C-shaped root canal system configuration, level of canal bifurcation and radicular grooves were evaluated by two endodontists trained in CBCT evaluation; previously calibrated between them, and a radiologist with endodontic experience. Data were statistically compared by The Chi-square test (α = 0.05) to examine any significant difference between gender and C-shaped root canal system and any significant difference between C-shaped configuration according to Fan criteria and gender.

RESULTS

Overall 100% (n = 688) teeth examined, 19.2% (n = 132) had a C-shaped root canals system. 9.16% (n = 63) in male patients and 10.03% (n = 69) in female patients. The prevalence of C-shaped root canal system in mandibular first premolar was 83.33 and 16.66% in mandibular second premolars. According to Fan classification, the mandibular first premolars showed 3.63% as C1, 9.09% C2, 59.09% C3, 21.81% C4a, 1.8% C4b. Mandibular second premolars showed 13.63% as C1, 18.18% C2, 13.63% C3, 27.27% C4a, 9.09% C4b. Male patients showed 4.54% as C1, 3.78% C2, 22.72% C3, 11.36% C4a, 0.75% C4b, and 4.54% out of classification. Female patients showed 0.75% as C1, 6.81% C2, 30.03% C3, 9.84 C4a, 2.27% C4b, and 2.27% out of classification. The 53.36% canal bifurcation in mandibular first premolars and 50.09% in mandibular second premolars were in the middle third. No statistical differences were found between C-shaped root canal system and gender or C-shaped configuration according to Fan criteria and gender. P was < 0.05.

CONCLUSIONS

Within the limitation of this study, the presence of C-shaped anatomical system is relatively low in mandibular second premolars than in mandibular first premolars.

Efficacy of root canal treatment in c-shaped canals with adjunctive photodynamic therapy using micro-CT

AIM

To investigate the efficacy of conventional root canal treatment (cRCT) with adjunctive photodynamic therapy (aPDT) against microbial biofilms within infected c-shaped root canals.

METHODS

In this in vitro report, the inoculation of 20 freshly extracted human mandibular molar teeth having c-shaped root canal configuration was performed with E. faecalis and P. aeruginosa to produce three-day biofilms in prepared canal system. PDT used a combination of chlorin (ce6) and polyethylenimine (PEI) as the photosensitizer (PS). A 200 μ-fiber was employed to deliver a 660 nm diode laser light into the root canal, and this was compared and conjugated with conventional endodontic treatment utilizing antiseptic irrigation and mechanical debridement.

RESULTS

The utilization of aPDT (group-2) resulted in a considerable decrease in the count of E. faecalis and P. aeruginosa from 12.84 ± 2.18 CFU/mL to 5.13 ± 0.67 CFU/mL, and from 14.06 ± 3.98 CFU/mL to 4.82 ± 1.05 CFU/mL pre-and post-treatment, respectively. A statistically significant reduction in the bacterial counts of both microbes was observed after treatment among the samples of the both study groups (p < 0.05). Specimens in group-2 (8.42 ± 1.14 MPa) demonstrated the highest mean push-out bond strength, whereas the lowest was shown by samples in group-1 (7.08 ± 1.09 MPa). ANOVA showed no statistical difference between the research groups (p = 0.676). The independent t-test revealed that the mean push-out bond strength scores of the cervical segments were higher than the apical and middle segments of roots in research groups (p < 0.05).

CONCLUSION

In c-shaped root canals, the application of photodynamic therapy as an adjuvant to conventional root canal treatment contributes to a statistically significant decrease in the microbial count of E. faecalis and P. aeruginosa along with an improved push-out bond strength of the root canal filling material with root.

Effect of canal preparation with XP-endo Shaper and ProTaper Next on root canal geometry and dentin thickness of mandibular premolars with radicular grooves and two canals: a micro-CT study

OBJECTIVES

This study aimed to evaluate the effects of different shaping protocols on the root canal geometry and remaining dentin thickness of mandibular premolars with radicular grooves (RG) and two canals by means of micro-CT.

MATERIALS AND METHODS

Mandibular premolars with RG and two canals were matched based on their similar morphological dimensions and assigned to 2 experimental groups according to the canal preparation (n=8): XP-endo Shaper (XPS) and ProTaper Next (PTN) systems. Before and after preparation, morphometric measurements of the volume, surface area, structure model index, area, perimeter, roundness, major and minor diameters, as well as untouched canal walls, canal transportation, and dentin wall thickness were evaluated. Data were statistically compared within and between groups using the independent sample t test (α=5%).

RESULTS

XPS revealed less changes in volume, surface area, area, perimeter, and major and minor diameters (P<0.05). There was no significant difference in structure model index (SMI), roundness, and percentage of untouched canal walls between groups (P>0.05). XPS resulted in less apical canal transportation and a higher remaining dentin thickness toward the RG compared to PTN in lingual canals (P<0.05).

CONCLUSIONS

XPS revealed fewer changes in root canal geometry as well as lower transportation and a greater remaining dentin thickness in the lingual canals toward the RG compared to PTN.

CLINICAL RELEVANCE

Internal and external anatomical characteristics of mandibular premolars might have an influence on biomechanical preparation. Considering the risk of perforation, the canal preparation using XPS appears to be more conservative compared to PTN.

Evaluation of Palatal Furcation Groove and Root Canal Anatomy of Maxillary First Premolar: A CBCT and Micro-CT Study

Objectives

This study is aimed at investigating the root and root canal morphology by cone beam computed tomography (CBCT) and palatal furcation groove of the buccal root by microcomputed tomography (micro-CT) of maxillary first premolars in a Chinese subpopulation.

Methods

This study assessed CBCT images of 440 patients aged 14-80 years. Based on Vertucci's classification, the number of roots and the canal configuration were determined. Forty-eight maxillary first premolars with furcation grooves were analyzed by micro-CT in patients aged 18-25 years.

Results

Based on the CBCT assay, 70.22% and 29.32% of maxillary first premolars were 1 root and 2 roots, respectively. The configuration indicated statistical difference (P < 0.05) between male and female patients. The most common canal type was type IV and was found in 44.32% of cases, followed by type I in 27.84%, and then type II in 20.57%. Root bifurcations had 40.13% prevalence which was distributed more in the middle third than in the cervical and the apical third. For the micro-CT study, 95.83% of the furcation groove configuration was found in the bifurcated maxillary first premolars. The length varied from 1.02 to 7.63 mm. The mean depth of this groove was 0.57 mm in the root coronal, 0.47 mm in the root middle, and 0.22 mm in the root apical level. Palatal dentin width was smaller than 1 mm.

Conclusion

The anatomy of the root and root canal system and the irregular wall width of maxillary first premolars with furcation grooves may help dentists to understand the anatomical morphology and improve the outcomes of endodontic treatment.

Mandibular first premolar with five root canals: a case report

Background

Understanding the anatomical morphology of the root canal is key for successful root canal treatment. The aims of this case presentation are to report a unique case of root canal treatment involving five root canals in the mandibular first premolar and to highlight the importance of variation in root canals of mandibular first premolars in clinical practice.

Case presentation

A 25-year-old male with intermittent pain in relation to the lower right posterior teeth over 3 weeks was diagnosed with symptomatic pulpitis in tooth #44. Four root canals were found, including mesiobuccal, distobuccal-1, distobuccal-2, and distolingual roots, and the Mtwo rotary system was used for root canal preparation. The four root canals were filled after 2 weeks, when a fifth canal was found, located in the buccal cavity. The fifth canal was confirmed to be the mesiolingual root canal by cone beam computed tomography (CBCT) and was found to be curved. After completion of the root canal filling, CBCT was performed, and a three-dimensional root canal image was reconstructed. After 1 week of observation, the tooth was repaired using composite resin filling.

Conclusions

This is the first case presentation of a fifth canal of the mandibular first premolar and advances our understanding of variations in the anatomy of the mandibular first premolar. This case report provides a reference for the treatment of mandibular first premolars.

Prevalence and morphology of multiple roots, root canals and C-shaped canals in mandibular premolars from cone-beam computed tomography images in a Thai population

Background/purpose

Variations in root and root canal morphology of mandibular premolars of Thais has not been reported, and understanding these variations enhances endodontic success. The purpose was to investigate prevalence and morphology of multiple roots, root canals and C-shaped canals in mandibular premolars in a Thai population from cone-bean computed tomography (CBCT) images.

Materials and methods

A total of 349 first mandibular premolars and 416 second premolars from CBCT images with 0.125-mm voxel size and 60 × 60 mm field of view were evaluated. Number of roots, root canals, and C-shaped canals were recorded and statistically analyzed using chi-square test. Root canal configurations were defined according to the Vertucci's classification. Levels and distances of separated multiple canals were reported.

Results

Multiple roots in mandibular first premolars were found at 5.73% while none of second premolars had. Multiple root canals were found in the first premolars at 19.48% and the second premolars at 3.85%. C-shaped canals (C1/C2) were found in the first premolars at 3.72% and the second premolars at 0.48%. All parameters in the first premolars were significantly higher than in the second premolars (p < 0.01). The majority of multiple root canals were defined as Vertucci's type V (1–2 canals). Multiple root canals were frequently separated at the middle level of roots about 6.5–7.0 mm from the cementoenamel junction.

Conclusion

Prevalence of multiple roots/root canals and C-shaped canals in mandibular first premolars were significantly higher than in mandibular second premolars. Level of separation in multiple root canals was frequently at the mid-root level.

Preparation of the lingual canal in mandibular first premolar with canal bifurcation

The aim of this study was to establish an effective method of locating and negotiating the lingual canal in mandibular first premolars with two canals during root canal preparation. A total of 125 mandibular first premolars with radicular grooves were collected, and after micro-computed tomography scanning, 50 mandibular first premolars with a Vertucci V/III canal form were selected based on the inclusion criteria. Access cavities were prepared, and the lingual canals (LCs) were searched in four following steps: step 1 direct vision and a straight K-file; step 2 stereomicroscopy and a straight K-file; step 3 stereomicroscopy and a pre-curved K-file; and step 4 a long-neck bur. After localization, the LCs were instrumented. In most cases, access to the LC was achieved by step 2 (19/50, 38%) or step 3 (22/50, 44%). In three cases (6%), step 1 alone was enough to achieve access to the orifice, and in six cases (12%), access to the lingual canal was not achieved until step 4. Overall, 43 of the 50 mandibular first premolars (86%) were successfully instrumented, and the remaining seven failed. Two cases failed in the process of negotiating the canal to full length and five cases failed due to procedural errors (ledge formation, canal perforation, vertical fracture, or instrument separation). The LC in mandibular first premolars is a major endodontic challenge. A stereomicroscope and a pre-curved K file are suggested to be valuable tools for detecting and accessing the extra LC.

Characteristics of Endodontic Emergencies during Coronavirus Disease 2019 Outbreak in Wuhan

Introduction

In late 2019, an outbreak of a new coronavirus named severe acute respiratory syndrome coronavirus 2 was detected in Wuhan, China. A great percentage of patients with this disease developed symptoms of dry cough, malaise, and a high fever. During this time, several patients requiring assessment and treatment of endodontic emergencies were directed to the School and Hospital of Stomatology at Wuhan University, Wuhan, China. We examined the characteristics of these patients.

Methods

A total of 96 patients with a mean age of 42.24 ± 18.32 years visited the general and emergency department of the School and Hospital of Stomatology at Wuhan University because of endodontic emergencies during the peak period of February 22 to March 2, 2020. Patient information was collected and organized by date of visit, sex, age, and systemic disease history. Body temperature was measured and acquired for each patient, a coronavirus disease 2019 (COVID-19) epidemiologic investigation questionnaire was given to each patient, an endodontic diagnosis was determined for the offending tooth, and a verbal numerical rating scale (VNRS) was used to record pain levels.

Results

Of the total patient visits during this period, 50.26% of visits were for endodontic treatment. No patients had a fever (>37.2°C). One patient with a confirmed COVID-19 history was admitted after recovery. Three admitted patients had been exposed to confirmed or suspected COVID-19 patients. Twelve admitted patients (12.5%) with a mean age of 62.42 ± 13.77 years had a history of systemic diseases. The most common age group for endodontic emergencies was 45–64 years (30.21%), and patients of this group showed a significantly higher mean VNRS score compared with that of the 6- to 19-year age group and the 20- to 34-year age group (P < .05). The majority of endodontic emergency diagnoses were diseases of symptomatic irreversible pulpitis (53.10%). Patients who were diagnosed with symptomatic irreversible pulpitis, symptomatic apical periodontitis, and acute apical abscess showed a significantly higher mean VNRS score than that of other groups (P < .05).

Conclusions

Endodontic emergencies, with symptomatic irreversible pulpitis being the most common, consist of a much higher proportion of dental emergencies in a COVID-19 high-risk area than normally. Vital pulp therapy can advantageously reduce treatment time, resulting in a reduced risk of infection for vital pulp cases. Rubber dams, personal protective equipment, and patient screening are of great importance during the COVID-19 outbreak in protecting clinicians.

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.

Frequency of non-single canals in mandibular premolars and correlations with other anatomical variants: an in vivo cone beam computed tomography study

Background

A knowledge regarding anatomical variants is important to achieve success in endodontic treatment. Root canal treatment of mandibular first premolars (PM1 s) is challenging due to the existence of numerous variations in canal configurations, including a C-shaped variant. We aim to determine the frequency and morphologic characteristics of non-single canals of mandibular first (PM1 s) and second (PM2 s) premolars in a Korean population using cone beam computed tomography (CBCT) and to evaluate correlations between non-single canals of PM1 s and other anatomical variants, such as distolingual roots (DLRs) in mandibular first molars (M1 s) and C-shaped canals in mandibular second molars (M2 s).

Methods

A total of 971 PM1 s and 997 PM2 s from 500 patients were examined in vivo by CBCT. Root canal configurations and C-shaped canals were determined in accordance with the Vertucci classification and Fan classification, respectively. The correlation between non-single canals in PM1 s and DLRs in M1 s was evaluated using logistic regression analysis.

Results

PM2 s typically had one root (99.89%) with one canal (98.4%). Among PM1 s with non-single canals (21.2%), Vertucci type V (10.9%) and C-shaped (3.7%) canals were prevalent. Among C-shaped PM1 canals, the majority were Vertucci type V (77.8%); a C-shaped configuration (C2) was predominant mostly at the middle and/or apical third of the root. After adjusting for other variables (i.e., sex, age, and side), C-shaped canals in PM1 s was significantly correlated with the presence of DLRs in M1 s (odds ratio = 2.616; 95% confidence interval, 1.257–5.443; p = 0.010).

Conclusions

The presence of C-shaped PM1 canals was positively related to the presence of DLRs in M1 s. Although C-shaped canals in PM1 s are difficult to distinguish, this finding could aid clinicians in predicting C-shaped canal configurations in PM1 s of patients who exhibit DLRs in M1 s.

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.

Investigation using cone beam computed tomography analysis, of radicular grooves and canal configurations of mandibular premolars in a Turkish subpopulation

OBJECTIVE

To conduct an in vivo evaluation of prevalence of root canal configurations, lengths of C-shaped canals, prevalence and depths of radicular grooves (RGs), in mandibular first and second premolars in a Turkish subpopulation using cone beam computed tomography (CBCT).

MATERIALS AND METHODS

CBCT images of 327 first and 264 second premolars were included. Canal configurations, locations, lengths, and types of C-shaped canals, and RGs were evaluated on CBCT images. Data were statistically analyzed (P < 0.05).

RESULTS

First and second premolars were classified as follows: type I, (83.8%, 97.72%); type V, (12.22%, 0.76%); type III, (3.06%, 0.76%); and other types. RGs were exhibited by 14.68% of first and 2.27% of second premolars (P < 0.05). Incidence of complex canals (types III, V and other types, 89.8%) in first premolars with RGs was significantly higher versuswithout RGs (P < 0.05). C-shaped configuration was exhibited by 4.58% of first (80% semilunar-type), and 1.13% of second premolars (P < 0.05). All first premolars with C-shaped canals showed RGs and complex canals.

CONCLUSIONS

Complex canals and RGs frequently co-exist in mandibular premolars. C-shaped canals are not common in mandibular premolars, and mostly located in middle thirds. Type V is the most prevalent complex canal configuration in first premolars, and frequently associated with a C-shaped semilunar-type anatomy.

Radicular Groove Accessory Canal Morphology in Mandibular First Premolars: Micro-computed Tomographic Study

INTRODUCTION

The purpose of this study was to investigate the morphologic features of radicular groove accessory canals (RGACs) in mandibular first premolars and their relationship to root anatomy by micro-computed tomographic imaging.

METHODS

A total of 154 single-rooted mandibular first premolars with radicular grooves were selected. The teeth were scanned by micro-computed tomographic imaging, and the following parameters were recorded: (1) the presence of RGACs, (2) the origin of RGACs, (3) the position of the RGAC foramen in the groove in relation to root length, (4) the foramen diameter, (5) the type of groove present according to the Arizona State University dental anthropology scoring system (ASUDAS), and (6) the type of anatomy present according to Vertucci's classification. The data were recorded and statistically analyzed using the chi-square test (P < .05).

RESULTS

The incidence of RGACs in the teeth was 49.9%. The average distance from the cementoenamel junction plane to the RGAC foramen was 8.83 ± 2.53 mm, and the majority of the RGAC foramina were located in the middle third. Regarding the severity of the groove, the presence of RGACs was significantly higher for groups ASUDAS 3 and 4 compared with ASUDAS 1 and 2 (85.7% and 14.3%, respectively). The presence of at least 1 RGAC was greatest for Vertucci type V (46%) and for more complex types (46%) when compared with Vertucci types I and III.

CONCLUSIONS

Mandibular first premolars with radicular grooves often present with RGACs. An association between the internal and external anatomy and the presence of RGACs was detected in this study.

Micro-CT Evaluation of Root and Canal Morphology of Mandibular First Premolars with Radicular Grooves

Abstract The aim of this study was to evaluate morphological features of 70 single-rooted mandibular first premolars with radicular grooves (RG) using micro-CT technology. Teeth were scanned and evaluated regarding the morphology of the roots and root canals as well as length, depth and percentage frequency location of the RG. Volume, surface area and Structure Model Index (SMI) of the canals were measured for the full root length. Two-dimensional parameters and frequency of canal orifices were evaluated at 1, 2, and 3 mm levels from the apical foramen. The number of accessory canals, the dentinal thickness, and cross-sectional appearance of the canal at different root levels were also recorded. Expression of deep grooves was observed in 21.42% of the sample. Mean lengths of root and RG were 13.43 mm and 8.5 mm, respectively, while depth of the RG ranged from 0.75 to 1.13 mm. Mean canal volume, surface area and SMI were 10.78 mm3, 58.51 mm2, and 2.84, respectively. Apical delta was present in 4.35% of the sample and accessory canals were observed mostly at the middle and apical thirds. Two-dimensional parameters indicated an oval-shaped cross-sectional appearance of the root canal with a high percentage frequency of canal divisions (87.15%). Canal configuration type V (58.57%) was the most prevalent. C-shaped configuration was observed in 13 premolars (18.57%), whereas dentinal thickness ranged from 1.0 to 1.31 mm. Radicular grooves in mandibular first premolars was associated with the occurrence of several anatomical complexities, including C-shaped canals and divisions of the main root canal.

The best radiographic method for determining root canal morphology in mandibular first premolars: A study of Chinese descendants in Taiwan

Background/purpose

There is large variation in root canal morphology and undetected canals and incomplete instrumentation are reasons for root canal treatment failure. The purpose of this study was to determine the best radiographic method for determining root canal morphology in mandibular first premolars in Chinese descendants in Taiwan.

Materials and methods

Mandibular first premolars extracted due to caries, periodontal diseases, trauma, or for orthodontic reasons were used. Four indices were examined: (1) root canal bifurcation observed in the buccolingual view; (2) root canal continuity in the buccolingual view; (3) double root outline in the buccolingual view; and (4) Vertucci canal classification in the mesiodistal view.

Results

A total of 82 left and right mandibular first premolars were included, a complicated root canal was confirmed in 38 (46.3%) by cross-sectional imaging and a single root canal was found in 44 (53.7%). Bifurcation identified on the mesiodistal view exhibited the highest sensitivity (94.7%) and second highest specificity (88.6%) for identifying a complicated root canal; however, this view is not possible to obtain clinically. Canal bifurcation on the buccolingual view was the most specific (93.2%), but had the lowest sensitivity (73.7%). Canal continuity on the buccolingual view had a sensitivity of 94.7%, and specificity of 70.5%.

Conclusion

Combined X-ray analyses, such as performing the buccolingual view for identification of canal bifurcation and canal continuity, may increase the accuracy of identifying complex root canal morphology.

Use of cone-beam computed tomography and three-dimensional modeling for assessment of anomalous pulp canal configuration: a case report

Three-dimensional (3D) reconstruction of cone-beam computed tomography (CBCT) scans appears to be a valuable method for assessing pulp canal configuration. The aim of this report is to describe endodontic treatment of a mandibular second premolar with aberrant pulp canal morphology detected by CBCT and confirmed by 3D modeling. An accessory canal was suspected during endodontic treatment of the mandibular left second premolar in a 21 year old woman with a chief complaint of pulsating pain. Axial cross-sectional CBCT scans revealed that the pulp canal divided into mesiobuccal, lingual, and buccal canals in the middle third and ended as four separate foramina. 3D modeling confirmed the anomalous configuration of the fused root with a deep lingual groove. Endodontic treatment of the tooth was completed in two appointments. The root canals were obturated using lateral compaction of gutta-percha and root canal sealer. The tooth remained asymptomatic and did not develop periapical pathology until 12 months postoperatively. CBCT and 3D modeling enable preoperative evaluation of aberrant root canal systems and facilitate endodontic treatment.

C-shaped root canal configuration: A review of literature

The aim is to review and discuss the etiology, incidence, anatomic features, classification, diagnosis and management of the C-shaped canal configuration. C-shaped canal configuration is a variation that has a racial predilection and is commonly seen in mandibular second molars. The intricacies present in this variation of canal morphology can pose a challenge to the clinician during negotiation, debridement and obturation. Manual and electronic searches of literature were performed from 1979 to 2012, in Pub Med by crossing the keywords: C-shaped canals, mandibular second molar, mandibular first premolar, root canal morphology. Knowledge of the C-shaped canal configuration is essential to achieve success in endodontic therapy. Radiographic and clinical diagnoses can aid in identification and negotiation of the fan-shaped areas and intricacies of the C-shaped anatomy. Effective management of this anomalous canal configuration can be achieved with rotary and hand instrumentation assisted with sonics and ultrasonics. Modifications in the obturation techniques will ensure a 3-dimensional fill of the canal system and chamber retained restorations like amalgam or composites, serve as satisfactory post endodontic restorations.

The relationship between root concavities in first premolars and chronic periodontitis

OBJECTIVE

To evaluate the significance of first premolar root concavity on clinical indices of chronic periodontal disease and alveolar bone defects.

METHODS

Three-dimensional reconstruction by cone beam computed tomography was used to observe root surface anatomy and the type of alveolar bone defect seen in the mesial and distal sites of 272 first premolars from 99 patients who had presented with chronic periodontitis. Periodontal clinical indicators at each site were measured using a Florida Probe Corporation (Gainesville, FL, USA).

RESULTS

The incidence of mesial and distal root concavities of the maxillary first premolars was 100% and 39.3% respectively, and in the mandibular, the incidence was 42.5% and 31.3% respectively. The distributions of the different types of concavities in terms of both age and gender of the patients were not statistically significant. The mean probing depth and clinical attachment loss of the first premolars with root concavities were significantly higher than those without concavity (p < 0.05). Plaque accumulation was significantly different in the premolars with/without root concavities (p < 0.001). The type of alveolar bone defects with concavities was significantly different from those without concavities (p < 0.05). Ramp shape bone defects were dominant for teeth without concavities, while crater shape was seen for teeth with concavities.

CONCLUSION

Root concavities of the first premolars were associated with periodontal disease, and the type of interproximal alveolar bone defect. Root concavities may be important in contributing to local periodontal disease of the first premolars.