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The mandibular first premolar is commonly a single-rooted tooth with occasional presentation of radicular variations. This tooth usually has one root with only one canal (97.9 %). Presence of three canals is very rare. Anomalies may appear during odontogenesis which can lead to anatomical variations in teeth. Similarly, these variations may be associated with characteristics that can be attributed to specific population groups. Due to their low frequency, these additional canals can easily be missed. For this reason, a meticulous knowledge of tooth morphology and their possible anatomical variations are necessary, and the presence of extra roots and canals should be always considered before initiation of root canal treatment. Additionally, different radiographs and appropriated access cavity preparation is needed to ensure a success endodontic treatment. This article reports a diagnosis and endodontic treatment of a mandibular first premolar with three canals. [ABSTRACT FROM AUTHOR]

Introduction: The morphology of the root canal of the first premolars is not always the same and therefore a good knowledge of its dental anatomy is essential. Aim: To assess the morphology of roots and root canals of mandibular first premolars in a Peruvian population using cone-beam computed tomography (CBCT). Materials and Methods: This was a descriptive cross-sec-tional study. A total of 370 mandibular first premolars fulfilling the inclusion criteria were evaluated using CBCT, and the number of roots and root canals, the Vertucci’s classification of root canal configuration, age, sex and side of the tooth were registered. Results: One and two roots were presented in 96.2% (n=356) and 3.8% (n=14), respectively, of the mandibular first premolars analyzed, and one canal was present in 67.6% (n=250) and two canals in 32.2% (n=119). A type I root canal configuration was found in 67.6% (n=250) of the cases followed by type V with 26.2% (n=97). A statistically significant association was found between the number of roots and canals (p

Abstract 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.

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. [ABSTRACT FROM AUTHOR]

The anatomy of the root canal system always affects endodontic treatment outcomes. Mandibular premolar teeth demonstrate extreme variations in root canal morphology. Mandibular first premolars typically exhibit basic single-root and single-canal anatomy. The occurrence of three roots in the mandibular first premolar has not been commonly reported in the literature. This article reported a case of a 26-year-old male with spontaneous pain of the mandibular first premolar representing the presence of an extra canal on the periapical radiograph. Cone-beam computed tomography (CBCT) was used to assess the root canal details which led to the finding of three canals. Further, a periapical bone defect was detected, and finally, the nonsurgical endodontic management of the mandibular first premolar with three canals and three different apical foramina was performed in one session. [ABSTRACT FROM AUTHOR]

Understanding the variations in root canal morphology is important for successful endodontic treatment. Mandibular first premolars have a single root in 98% of cases, and multiple root canals are found in approximately 20% of cases. However, the details of these characteristic findings in panoramic radiography and their diagnostic accuracy are unknown. This study aimed to investigate the characteristic radiographic findings of mandibular first premolars possessing multiple root canals and determine the diagnostic accuracy using panoramic radiography. Four radiologists evaluated 347 mandibular first premolars in 186 patients who underwent panoramic radiography and dental cone beam computed tomography (CBCT). Two radiologists confirmed the existence of single or multiple root canals using CBCT. The remaining two radiologists evaluated the imaging findings of the root canal morphology and classified them into two patterns: gradual narrowing and sudden narrowing. In the case of the sudden narrowing pattern, the location of sudden narrowing was also evaluated. A gradual narrowing pattern was observed in 56% of teeth with a single root canal, and a sudden narrowing pattern was observed in 83% of teeth with multiple root canals. When sudden narrowing between the cervical and apical 1/4 of the root canal was used as the diagnostic criterion for multiple root canal teeth, the highest diagnostic performance was observed (sensitivity, 76.1%; specificity, 73.9%). The sudden narrowing between the cervical level and the apical 1/4 level of the root canal is a practical diagnostic criterion for mandibular first premolar with multiple root canals. [ABSTRACT FROM AUTHOR]

Aim: To describe the radicular dentine thickness in mandibular first premolars presenting C‐shaped root canals, 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 associate them with the dentine thickness. Methodology: A total of 70 mandibular first premolars presenting C‐shaped root canals were examined. Their internal morphology was analysed using Vertucci's and Fan's criteria, and their external morphology was analysed 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 =.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 <.001) and the buccal canal in the middle‐apical plane (p =.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 <.001) of grade 3 teeth and the middle‐apical plane (p <.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 (odds ratio [OR] = 4, p =.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 grades 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. [ABSTRACT FROM AUTHOR]

Aim: To investigate anatomical and morphological variability of permanent mandibular first premolar teeth in the population of Manipur state of Indian subcontinent. Materials and Methods: Four hundred and eighty teeth from a pool of Manipuri population were studied for anatomical and morphological variability using staining and clearing technique. All samples were evaluated for the number of roots, root canals, root canal configuration, presence of lateral canals, intercanal communications, and apical deltas. Results: Single root with one canal was present in 81.25% (390/480) and single root with two canals in 18.75% (90/480) of samples. Root canal configuration according to Vertucci's classification was as follows: Type I (43.7%) followed by Type V (25%), Type VI (12.5%), and Type II, III, and VII (6.25%). Intercanal communications in the apical third were 12.5% (60/480) and 6.25% (30/480) in the middle third of the root. Occurrence of lateral canals in the apical third was 18.75% (90/480). Apical delta was found in 37.75% (180/480) of samples. Conclusion: The results of this study highlight the variability patterns of mandibular first premolar tooth existent in the population of the state of Manipur. Single-rooted teeth are most common with predominantly Vertucci's Type I root canal configuration and significant presence of lateral canals and apical ramifications. Clinical Significance: Sound knowledge of anatomy of the root canal and possible variations can contribute to a successful treatment outcome.

Objective To observe the anatomical morphology of root canal system of human mandibular first premolar based on the reconstructed images of cone-beam CT (CBCT). Methods The CBCT images of 1 102 mandibular first premolars meeting the inclusion criteria were reconstructed. We observed the root canal morphology and root canal groove (depression)of mandibular first premolars, and measured the thinnest root canal wall thickness of single premolars in different cross sections by one volume viewer software. Results Among the 1 102 mandibular first premolars, there were 958 type I root canals, 92 type V root canals, 42 type C root canals and 10 type III root canals. The detection rates of type I, type III, type V and C root canals in 424 male patients were 75. 0%, 2. 4%, 15. 6% and 7. 1%, respectively. The detection rates of type I, type III, type V and C root canals in 678 female patients were 94. 4%, 0, 3. 8%, and 1. 8%, respectively (all P<0. 05). Among the 1 102 mandibular first premolars, 524 (564) had root groove (depression), and the incidence of root groove (depression)was 47. 5%. Among the 524 teeth with root surface groove (depression), the starting positions were 4 at 1/3 of root crown, 500 at 1/3 of root middle and 20 at 1/3 of root apex. Among the 564 root surface grooves (depressions), 356 were on the mesial root surface, 194 on the distal root surface, 10 on the lingual root surface, and 4 on the buccal root surface. The starting positions were 4 at 1/3 of the root crown, 536 at 1/3 of root middle, and 24 at 1/3 of root apex. The thickness of the thinnest root canal wall at the junction of crown and root was (1. 74±0. 14)mm, and the thickness of the thinnest root canal wall at the junction of crown and root in men was greater than that in women (P< 0. 05). The thinnest root canal wall thickness at the junction of 1/3 of root neck and 1/3 of root middle was (1. 24± 0. 10)mm, with no significant difference between men and women (P>0. 05). The thinnest root canal wall thickness at the junction of 1/3 of the middle root and 1/3 of the apical root was (0. 85±0. 11)mm, with no significant difference between men and women (P>0. 05). Conclusions The root canal morphology of mandibular first premolar is complex and changeable. Type I is the most common root canal type, and there are differences between men and women. The incidence of root surface groove (depression)of mandibular first premolar is high. And it often occurs on the mesial root surface and mostly starts at 1/3 of the root. The thickness of the thinnest root canal wall of a mandibular first premolar with a single root canal in different cross sections is different, and the thickness of the thinnest root canal wall at the junction of crown and root differs in gender. [ABSTRACT FROM AUTHOR]

We studied 229 previously obtained CBCT images. It is revealed that a incidence complicated root canal morphology of mandibular teeth (two root and two root canals in mandibular incisors, canines, premolars; C-shaped second molars and premolars) were two root canals in mandibular incisors - 47,2%, first premolars - 20,5%, two root and two root canals in canines - 6,1%, second premolars - 3,5%,C-shaped second molars - 2,9%. The incidence of C-shaped canals in mandibular first premolars were 14,4%, in mandibular second premolars - 0,9%, in second premolars - 2,9%.

The mandibular first premolar, which is the anteriormost tooth in the mandibular arch, differs from other teeth in that it typically has two roots and two to four canals. The current case involves treating a mandibular first premolar with two canals through endodontic therapy. The 42-year-old male patient's left mandibular first premolar was diagnosed with irreversible pulpitis. The lateral view X-ray depicted two canals. In the dental procedure, endodontic treatment involves working under an operating microscope and using magnification to treat the affected tooth. After canal shaping the tooth was treated with the crown after it had been cleaned and then adjusted for the bite. As aforementioned, no signs of periapical disease were observed when the tooth was rediscovered a year later. However, this case study indicates that any shift in the anatomy of the canal in premolars should be well monitored and controlled to improve endodontic treatment outcomes of such teeth as the mandibular first premolars., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Gurav et al.)

Proper knowledge of the anatomic structure of the root canal system is a vital prerequisite for successful root canal therapy. This report presents the endodontic management a two-rooted lower first premolar with five root canals. A similar case has not been reported to date. The use of cone beam computed tomography (CBCT) in rare and doubtful cases helps establish an accurate diagnosis and render successful endodontic treatment thereafter. This article helps broaden our knowledge about the possible anatomic diversities as to teeth with more roots and root canals than expected normally. [ABSTRACT FROM AUTHOR]

Aim: The aim of this case report is to present a series of anatomical variations and endodontic treatments in four two-canal mandibular premolar teeth and three rooted three-canal maxillary second premolar teeth with root canal treatment indications identified via clinical and radiographic examinations. The success of root canal treatment is achieved with a thoroughly examined root canal morphology that has been accurately determined radiographically and clinically before adequate shaping, irrigation, and hermetic filling procedures. Root canals that are not found or not adequately disinfected can cause root canal treatment failure and complications, such as pain, swelling, also known as flare-up, or persistent fistula, after treatment. Canal variations in the teeth were detected via periapical radiographs during the root canal instrumentation stage. Methodology: The endodontic treatments of four two-canal mandibular premolar teeth and one triple-rooted three-canal maxillary second premolar with root canal treatment indications were described. Conclusion: To achieve full success in root canal treatment, anatomical variations should be examined in detail before and during treatment, and treatment should be completed with appropriate techniques. [ABSTRACT FROM AUTHOR]

Aim: To investigate anatomical and morphological variability of permanent mandibular first premolar teeth in the population of Manipur state of Indian subcontinent. Materials and Methods: Four hundred and eighty teeth from a pool of Manipuri population were studied for anatomical and morphological variability using staining and clearing technique. All samples were evaluated for the number of roots, root canals, root canal configuration, presence of lateral canals, intercanal communications, and apical deltas. Results: Single root with one canal was present in 81.25% (390/480) and single root with two canals in 18.75% (90/480) of samples. Root canal configuration according to Vertucci's classification was as follows: Type I (43.7%) followed by Type V (25%), Type VI (12.5%), and Type II, III, and VII (6.25%). Intercanal communications in the apical third were 12.5% (60/480) and 6.25% (30/480) in the middle third of the root. Occurrence of lateral canals in the apical third was 18.75% (90/480). Apical delta was found in 37.75% (180/480) of samples. Conclusion: The results of this study highlight the variability patterns of mandibular first premolar tooth existent in the population of the state of Manipur. Single-rooted teeth are most common with predominantly Vertucci's Type I root canal configuration and significant presence of lateral canals and apical ramifications. Clinical Significance: Sound knowledge of anatomy of the root canal and possible variations can contribute to a successful treatment outcome. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aim: The endodontic literature reports considerable variations in the root canal morphology of mandibular first premolars, including variations in number of roots and root canals. Additionally C-shaped canal configuration has also been documented in some case reports. Thus, the aim of this study was to determine the incidence of C-shaped canal morphology in mandibular first premolars in an Indian population. Materials and Methodology: A total of 110 human mandibular left and right first premolars were collected. All teeth were subjected to CBCT exposures, made with the unit operating in continuous mode at 80 kV and 12 mA with an exposure time of 12s. CBCT images were analyzed using CS 3D Imaging Software 3.1 in the oblique cut. Result: Out of 110 teeth, five teeth (4.54%) presented with the C-shaped canal configuration. Conclusion: Limitations inherent in 2D imaging can be overcome by newer imaging techniques such as CBCT to better appreciate the variations in root canal anatomy.

Aim: The current study aimed to investigate the root canal anatomy and their variations associated with premolar teeth in a defined population using tooth-clearing technique. Materials and Methods: Three hundred extracted premolar teeth (maxillary and mandibular) were collected from western Maharashtra (Pune). Access cavities were prepared and samples were placed in 2.5% sodium hypochlorite for 48 h. They were then decalcified with 5% nitric acid, dehydrated, and rendered clear by immersion in methyl salicylate, and methylene blue dye was injected. After staining, cleared teeth were evaluated for (i) number of roots and root canals, (ii) number of apical foramina, (iii) shape of root, (iv) type of root canal based on Vertucci's classification, (v) presence of lateral canals and their locations, and (vi) presence of root curvatures. Results: Vertucci Type I canal configuration represented the highest percentage (72.66%) followed by Type II (11.66%), Type III (6.33%), Type IV (4.66%), Type VI (2.66%), Type V (1.66%), Type VIII (0.66%), and C shaped (2.33%). Accessory canals were detected in 22.8% and intercanal connections were observed in 24.8% while 54% showed apical delta. Conclusion: Such knowledge is clinically useful for localization, negotiation, and subsequent management of premolar teeth in the studied population.

Knowledge about the presence and anatomy of c-shaped canals in the root is essential for endodontic treatment. Identification of the presence of a c-shaped canal and its classification might help the clinician to modify the treatment protocol. The aim of this study was to determine the prevalence of c-shaped canals and to evaluate the variations in these canals in mandibular first premolars and second molars. Sixty first premolars and 32 second molars from the mandible were scanned using microcomputed tomography (CT) at a resolution of 50 µm. Transverse sections were obtained from each root and categorized. Alterations in the configurations of the c-shaped canals were noted. The prevalence of c-shaped canals in the mandibular first premolars was 17% and in the mandibular second molars was 16,67%. Alterations in configuration were observed all along the root canal. The dentist should be aware of the presence of c-shaped canals and the possibility of alterations in the shape of these canals while performing endodontic treatment. In cases where a c-shaped root canal is suspected, radiographic examinations should be performed to detect alterations in the configurations so that successful treatment can be provided. [ABSTRACT FROM AUTHOR]

The aim of this study was to systematically revise the root canal configuration (RCC) literature and to investigate the root canal morphology of mandibular first premolars (Ma1Ps) of 2 populations by means of micro–computed tomographic imaging. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines including RCC randomized controlled trials and cross-sectional, cohort, comparative, validation, and evaluation studies. Furthermore, the RCC, physiological foramina, the frequency of accessory and connecting canals, and the physiological foramina morphology of 109 Ma1Ps were investigated by means of micro–computed tomographic imaging. The RCC results are described using a 4-digit system code. The most frequent RCCs observed were 1-1-1/1 (70.6%), 1-1-2/2 (7.3%), 1-2-2/2 (7.3%), and 1-2-1/1 (5.5%). Accessory canals were observed in 31.2%. Connecting canals were observed in 1-1-2/2 (4.6%), 1-2-2/2 (4.6%), 1-1-2/1 (1.8%), and 1-2-1/1 (1.8%) RCCs. Accessory foramina were observed in 52.3%; 30.3% of the Ma1Ps had 1 accessory foramen, 12.8% had 2, 2.8% had 3, 2.8% had 4, 2.8% had 5, and 0.92% had 6. The narrow and wide diameter mean of 136 physiological foramina was 0.28 mm (±0.9) and 0.37 mm (±0.11) when only 1 physiological foramen was present. This study provides detailed root canal morphology of Ma1Ps in a Swiss-German population. Within the limitations of the study, the authors recommend a final physiological foramen preparation size of instrument tip sizes 30–40; yet, such a decision should be carefully considered on an individual basis. [ABSTRACT FROM AUTHOR]

To compare the accuracy of digital periapical radiography (DPR) and cone beam computed tomography (CBCT) in evaluating the root canal configuration (RCC) of mandibular first premolars by using a clearing technique (CLT). 122 extracted human mandibular first premolars were radiography by DPR and CBCT, then cleared and stained. All radiographs were interpreted by three evaluators, who classified the RCC by using Vertucci's classification. All interpreted data from DPR and CBCT were statistically compared with CLT by using a chi-square test at a significance level of a = 0.05. Post-analyses of the RCC's percentages of correct identifications by three techniques, chisquare test revealed no significant difference (P = .156) between CBCT and CLT, but with some significant differences (P = .000) between DPR and CLT, together with those between DPR and CBCT (DPR = 94.26% and CBCT = 98.36% in the overview; and DPR = 76.67% and CBCT = 93.33% in the teeth with two root canals). For those with single root canal, no significant difference among three techniques was observed. CBCT gave as accurate evaluations of the mandibular first premolars' RCC as CLT, while DPR provided the least accuracy. [ABSTRACT FROM AUTHOR]

Proper knowledge of the anatomic structure of the root canal system is a vital prerequisite for successful root canal therapy. This report presents the endodontic management a two-rooted lower first premolar with five root canals. A similar case has not been reported to date. The use of cone beam computed tomography (CBCT) in rare and doubtful cases helps establish an accurate diagnosis and render successful endodontic treatment thereafter. This article helps broaden our knowledge about the possible anatomic diversities as to teeth with more roots and root canals than expected normally.

The mandibular first premolar has complicated morphology of root canal, it has more variation which in⁃ creases the incidence of multiple root canals. A successful root canal therapy not only need strict cleaning, disinfection and filling, but also need a correct understanding of root canal morphology and anatomy. Otherwise there might be a risk of missing canals that resulting the failure of the therapy. Also crown closure is one of the successful elements of root canal therapy. This is a case report accompanied by a review of the literature that shows the unusual anatomy of the mandibular first molar with three roots and three root canals.

Root canal therapy of mandibular first premolar is challenging for there are some variations in mandibu⁃ lar first premolar root canal. And it is easy to fail when there are some tiny missing root canals. This article reported a mandibular first premolar with apical furcation which was found by the combined application of X⁃ray and CBCT. This article also focuses on root canal exploration and instrumentation, in order to provide evidence for treatment of mandibu⁃ lar first premolar.

Objective. The aim of this paper was to analyze the distribution of stress and deformation on the mandibular first premolar under two types of loading (axial and para-axial load of 200 N) using the FEM computer method. Materials and Method. For this research a µCT scan of the first mandibular premolar was used, and the method used in this research was FEM analysis under two types of loading. Results. The values of the von Mises stress measured in the cervical part of an intact tooth under axial load were up to 12 MPa, and under paraaxial load over 50 MPa. The values of the stress measured on the bottom of the noncarious lesion are very high ≈ 240 Mpa. Stress values in the cervical part of the intact tooth are higher in the zone of the sub-surface enamel. The deformation values of the tooth under para-axial loading were ≈ 10 times higher than the value of the deformation under axial load. The greatest deformations were seen in the area of the tooth crown. Conclusions. Occlusal loading leads to significant stress in the cervical part of teeth. The values of the measured stress are greater under the action of paraxial load. The values of stress in abfraction lesions measured under a paraxial load are extremely high. Exposing the lesion to further stress will lead to its deepening. The total deformation of the entire tooth under paraxial load was ≈ 10 times higher compared to the deformation value of the tooth under axial load. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the size, shape and position of the physiological foramen and the relationship between the age and gender to the location and size of the apical foramen of mandibular first premolars. One hundred and one extracted human mandibular first premolar teeth were examined; age and gender of the patients were recorded. Apices of teeth were examined stereomicroscopically for number, size and shape of apical foramina; frequency and deviation of accessory foramina from the apex and the relation with age and gender. Sixty‐four of the premolars had one foramen and 23% had two. The distances from the foramina openings to the apices ranged from 0.07 to 2.18 mm. In younger range irregular shape was dominant (41%), whilst in older range, round shape was dominant (45%). The shape of the apical foramen changed with age and the distance from the foramen to the anatomical apex increased with age. [ABSTRACT FROM AUTHOR]

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. 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). 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. 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. [ABSTRACT FROM AUTHOR]

To evaluate and compare several anatomical parameters of mandibular first premolars from individuals from different Latin American countries using micro-computed tomography. Five hundred extracted mandibular first premolars from Brazilian, Argentinian, Chilean, Colombian, and Ecuadorian individuals were scanned using micro-computed tomography (n = 100 teeth/country). Root canal configurations were classified according to established parameters. Analyses also included: canal volume and surface area, structure model index, distances from the apical foramen to the root apex or the cementoenamel junction, major/minor apical canal diameters, canal orifice shape, and prevalence of ramifications. A single root was the most common anatomy in all countries (range, 97%−100%). Vertucci's type-I canal was the most frequent configuration (range, 36%−66%), followed by C-shaped and type-V canals. The oval-shaped canal orifice was the most predominant in all countries (range, 34%−58%), followed by the circular shape (range, 16%−47%). C-shaped canals occurred in all subpopulations (range, 14%−26%), always associated with radicular grooves. Ranges for canal ramifications were as follows: accessory canals, 36%−73%; lateral canals, 4%−12%; and apical delta, 4%−14% of the teeth. Many anatomic parameters differed significantly between countries (P <.05). Vertucci's types-I and -V, and C-shaped canals were the most prevalent configurations in the subpopulations investigated. Accessory canals and several complex anatomies were found, with some significantly different frequencies between countries. • Anatomy of mandibular first premolars of 5 South American countries was compared. • The most prevalent configurations were type I, V, and C-shaped canals. • Oval and long oval were the most frequent shapes. • All C-shaped canals showed radicular grooves. • Some anatomical differences were observed among countries. [ABSTRACT FROM AUTHOR]

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.

Cone-beam computed tomography (CBCT) can provide valuable data for root canal systems of human teeth in vivo. This study used CBCT to evaluate the number of roots and canals of 300 mandibular first premolars in 150 northern Taiwanese patients. Methods: The root canal systems of 300 mandibular first premolars in 150 northern Taiwanese patients with bilateral premolars were analyzed by CBCT. Results: Of the 300 mandibular first premolars, 197 (65.7%) had one root with one canal (1R1C), 49 (16.3%) had one root with two canals (1R2C), 51 (17.0%) had two roots with one canal in each root (2R2C), and three (1.0%) had three roots with one canal in each root (3R3C). Statistical analyses showed that women had a significantly higher incidence of 1R1C mandibular first premolars (71.4%) than men (58.8%, p = 0.031), and men had a significantly higher incidence of 2R2C mandibular first premolars (27.2%) than women (8.5%, p

A successful endodontic treatment requires knowledge of the internal configuration of dental root canals. Most of the people who live in Yucatan are of Maya origin, characterized by a Mongoloid dental pattern. Because of their ethnicity, variations are expected. The purpose of this investigation is to assess the morphological characteristics and variability of this population. One hundred and five extracted first mandibular premolars of Mexican Maya population were analyzed; the sample was obtained from the Oral Surgery Clinic in the School of Dentistry at the Autonomous University of Yucatan with written informed consent. Analyses were performed by means of Cone Beam Computed Tomography. Vertucci's Type I was the most prevalent configuration with 51.4%, but 41 cases (39.1%) presented a radicular groove and a C-shaped canal configuration. Overall, we documented 1, 2, 3, and 4 root canals. Mandibular first premolars are very variable in the Yucatecan population. The variability and frequency of C-shape is similar to mandibular second molars confirming the importance of the ethnic background for the endodontic treatments. [ABSTRACT FROM AUTHOR]

In the literature we found that approximately 98% of the mandibular second teeth premolars are single-rooted. The incidence of two roots was 1.8%. Three roots were found in 0.2% of the teeth studied. Four roots were rare and were found in less than 0.1% of the teeth studied. Studies of the internal canal morphology revealed that a single canal was present in 75.8% of the teeth. Two or more canals were found in 24.2% of the evaluated teeth. A single apical foramen was found in 78.9% of the teeth, whereas 21.1% had two or more apical foramina. Major reason for failure of root canal treatment is miss canals. The premolars are difficult for endodontic treatment and have higher failure rate. This may be due to their anatomic variations of the root canal morphology. The bucal canal is easier to be founded while the lingual is more often missed when the tooth has two canals presented. The comlications may occur if the endodontist does not use the latest diagnostic equipment which decrease the chances of success. This article reports and discusses the successful treatment of a mandibular second premolar with two canals in a 43-year old Bulgarian male. Clinical examination showed a large carious lesion with pulp exposure. Radiographs showed no periapical changes. An endodontic treatment with TF-system was made and the canals were obturated with the method - cold lateral condensation and a sealer.

Introduction Mandibular premolars exhibit considerable variations in their root canal system that can be particularly difficult to diagnose. Avoiding mishaps and successful nonsurgical endodontic therapy depends on an absolute understanding of the root and root canal morphology to locate, prepare, and obturate the canals. Methods This case report describes the endodontic therapy of a mandibular first premolar with 2 roots and 3 canals with confirmation of cone-beam computed tomography. It also cites the incidence of morphologic variations reported in mandibular first premolars, based on ethnic diversity. Result Cone-beam computed tomography (axial and sagittal sections) confirmed the presence of 2 roots and 3 canals in a mandibular first premolar. Here, the main canal divided into 3 root canals at the middle third, otherwise described as Sert and Bayirli's type IX canal configuration. Conclusion The occurrence of documented cases of a mandibular first premolar with Sert and Bayirli's type IX root canal configuration is rare. Failure to recognize a second and third canal in the present case might have otherwise resulted in endodontic reinfection. [ABSTRACT FROM AUTHOR]

Introduction The purpose of this study was to examine the frequency and bilateral consistency of distolingual roots (DLRs) in permanent mandibular first molars (PMFMs) and root canal configurations in PMFPs (permanent mandibular first premolars) and to determine the correlation between the root canal configurations of PMFPs with the appearance of DLRs in PMFMs. Methods A total of 932 cone-beam computed tomographic images of PMFMs and PMFPs were collected from 233 patients. The frequency and bilateral consistency of DLRs in PMFMs along with root canal configurations (root number and canal number) of PMFPs were recorded and evaluated ipsilaterally and contralaterally. Multivariable logistic regression analysis was used to evaluate the correlation between the root canal configurations of PMFPs with the appearance of DLRs in PMFMs. Results The prevalence of PMFMs with DLRs was 24.7%, and the incidence of complicated root canal configurations of PMFPs was 26.6%. The incidence of complicated root canal configurations of PMFPs was 19.6% in the non-DLR group, 37.2% in the unilateral DLR group, and 44.7% in the bilateral DLR group. After adjusting for categoric variables including sex, age, and side, the odds ratios for the frequency of complicated root canal configurations of PMFPs in the unilateral DLR and bilateral DLR groups compared with the non-DLR group were 2.472 (95% confidence interval, 1.434–4.263; P = .001) and 3.392 (95% confidence interval, 1.976–5.823; P < .001), respectively. Conclusions An increasing and corresponding trend between the presence of DLRs in PMFMs and complicated root canal configurations in PMFPs was noted in Taiwanese individuals. These results suggest that the clinicians should familiarize themselves with the anatomic variants of PMFMs and PMFPs before endodontic treatment. [ABSTRACT FROM AUTHOR]

Objectives: This study evaluated the accuracy of cone-beam computed tomography (CBCT) in detecting the root canal morphology of mandibular first premolars using micro-computed tomography (micro-CT) as a reference standard. Materials and methods: In total, 143 extracted human mandibular first premolars were selected and scanned using micro-CT and CBCT. The acquired images were used to evaluate the root canal morphology in each tooth, and evaluations were repeated after 2 weeks. The root canal configurations observed on the three-dimensional images were recorded, and the findings from both modalities were compared using chi-square tests. The actual agreement between the two modalities was assessed using kappa statistics. Results: In total, the root morphologies in 136 mandibular first premolars were consistently identified by both CBCT and micro-CT: type I in 104, type III in five, type V in 20, and type IX in seven. Of the remaining seven teeth, the morphology in two, one, and four teeth was identified as type I, type VII, and type IX (type 1-3 in two and type 1-2-3 in two), respectively, by micro-CT and misdiagnosed as type III, type V, and type V, respectively, by CBCT. There were no significant differences between the two modalities with regard to the accurate detection of root canal configurations, with a kappa value of 0.886 for the actual agreement. Conclusions: Although CBCT may be accurate in detecting the root canal configuration in mandibular first premolars, it produces poorer image details compared with micro-CT. Clinical relevance: CBCT is a reliable radiological technique, but its accuracy in detecting details of the root canal morphology in mandibular first premolars, especially in some complex root canal configurations, needs to be improved. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate canal configuration of mandibular first premolars in an Egyptian population. Two hundred fifty human extracted mandibular first premolars were collected from Egyptian patients and a small hole in the center of the occlusal surface of each tooth was made perforating the roof of the pulp chamber. Teeth were decalcified by immersing in nitric acid and dehydrated in ascending concentrations of ethyl alcohol. A waterproof black ink was passively injected from the occlusal hole into pulp system and stained teeth were immersed in methyl salicylate solution for clearing. Standardized pictures of the cleared teeth were obtained and anatomical features of the root canal were observed. The average length of the mandibular first premolar teeth was 22.48 ± 1.74 mm, one-rooted teeth were 96.8% and the two-rooted were 3.2%. Vertucci Type I canal configuration represented the highest percentage (61.2%) followed by Type V (16.4%), Type IV (13.2%), Type II (5.6%) and Type III (2.8%). Vertucci Type VI canal configuration represented the lowest percentage (0.4%) and a complex configuration was found in one tooth. Accessory canals were detected in 22.8% and inter-canal connections were observed in 24.8% while 54% showed apical delta. Such knowledge is clinically useful for localization and negotiation of canals of mandibular first premolar, as well as their subsequent management in Egyptian population.