Internal morphology of distal roots of mandibular first molars revealed by computed microtomography.

To evaluate the internal morphology of 100 distal roots of mandibular first molars using micro-CT. Teeth were scanned to characterise: Vertucci type, root length, canal shape, presence and location of accessory canals, and the number of foramina at 4 mm from the apex, presence of root isthmus and the length from the primary canal to the apical foramen. Vertucci type I was found in 57% of cases, followed by V (27%). The most common cross-section 1 mm from the apex was oval (49%) and circular (38%). The average root length was 16.06 mm (16.61-19.02 mm). The mean foramen size was 0.32 and 0.53 mm for the minor and major diameters, respectively. The volume, surface area and SMI were 7.84 mm3 , 68.87 mm2 and 1.52 mm, respectively. Root isthmi were found in 47% of the samples, and the length mean from the primary canal to the apical foramen was 2,03 mm. The internal morphology of the distal roots of mandibular first molars may be complex and shows variations.

An Automated Measurement Method for the Endodontic Working Width of Lower Molars by Means of Parametric Models Using Cone-beam Computed Tomographcy and Micro-Computed Tomography.

INTRODUCTION: A new method for the approximation of the root canal's cross-sectional shape and its working width using cone-beam computed tomographic (CBCT) or micro-computed tomographic (micro-CT) imaging was introduced. METHODS: Scanned data from 29 extracted human mandibular first and second molar distal root canals without instrumentation were reconstructed and analyzed with a self-developed measurement algorithm. The 3-dimensional volume models were sliced perpendicular to the vertical axis. Using different 2-dimensional parametric models, the contour of each root canal slice was approximated and used to determine the canal's cross-sectional dimensions. The measurements of minor width, major width, and the root canal's conicity were statistically analyzed using analysis of variance. RESULTS: The measured minor and major widths of the investigated root canals were significantly higher (probability value P < .05) when evaluated by CBCT images than the results obtained from micro-CT data. Both dimensions increased starting from the apical foramen (P < .01). The narrowest measured canal widths were 0.19-0.24 mm for CBCT imaging and 0.09-0.21 mm for micro-CT imaging in the apical part. The maximum values for conicity were between 13% and 17% in the cervical third. CONCLUSIONS: The 3-dimensional imaging data from CBCT and micro-CT imaging enabled a valuable anatomic assessment of the root canal's cross-sectional working width along the canal up to the physiological foramen in order to determine an adequate apical diameter as well as the correct measured taper in the cervical and medial part.

Conserved and differentiated functions of CIK receptor kinases in modulating stem cell signaling in Arabidopsis.

The shoot apical meristem (SAM) and root apical meristem (RAM) act as pools of stem cells that give rise to aboveground and underground tissues and organs in higher plants, respectively. The CLAVATA3 (CLV3)-WUSCHEL (WUS) negative-feedback loop acts as a core pathway controlling SAM homeostasis, while CLV3/EMBRYO SURROUNDING REGION (ESR) 40 (CLE40) and WUSCHEL-RELATED HOMEOBOX5 (WOX5), homologs of CLV3 and WUS, direct columella stem cell fate. Moreover, CLV3 INSENSITIVE KINASES (CIKs) have been shown to be essential for maintaining SAM homeostasis, whereas whether they regulate the distal root meristem remains to be elucidated. Here, we report that CIKs are indispensable for transducing the CLE40 signal to maintain homeostasis of the distal root meristem. We found that the cik mutant roots displayed disrupted quiescent center and delayed columella stem cell (CSC) differentiation. Biochemical assays demonstrated that CIKs interact with ARABIDOPSIS CRINKLY4 (ACR4) in a ligand-independent manner and can be phosphorylated by ACR4 in vitro. In addition, the phosphorylation of CIKs can be rapidly induced by CLE40, which partially depends on ACR4. Although CIKs act as conserved and redundant regulators in the SAM and RAM, our results demonstrated that they exhibit differentiated functions in these meristems.

Continuous Measurement of Three-Dimensional Root Canal Curvature Using Cone-Beam Computed and Micro-Computed Tomography: A Comparative Study.

The knowledge of root canal curvature is crucial regarding the prevention of ledge formation, root perforation and the possibility of endodontic instruments' fracture during endodontic treatments. Therefore, a quantification method of the root canal curvature as well as the applicability of diagnostically relevant tomographic three-dimensional (3D) imaging data is necessary. Hereby, cone-beam computed tomography (CBCT) images and micro-computed tomography (µCT) data of distal root canals were analysed concerning the continuous three-dimensional curvature of human mandibular molars ( n = 50). The curvature of the canal's three-dimensional centre line was determined by evaluating the tomographic images. The centroids of each root canal slice were identified and approximated by spline curves to obtain the centre line and therefore, its curvature. Comparing the results evaluated from CBCT and µCT images, minimum radii of curvature of 2.6 mm and 2.1 mm were determined, respectively. The observation of the centre line demonstrated the requirement of the three-dimensional imaging data from CBCT and µCT for a reliable curvature analysis. Conclusively, the evaluation of CBCT and µCT images results in comparable radii of curvature. Thus, the application of the introduced method in combination with CBCT applied to patient cases could offer an important preliminary diagnostical step to prevent endodontic treatment complications.

Receptor-like protein kinase-mediated signaling in controlling root meristem homeostasis.

Generation of the root greatly benefits higher plants living on land. Continuous root growth and development are achieved by the root apical meristem, which acts as a reservoir of stem cells. The stem cells, on the one hand, constantly renew themselves through cell division. On the other hand, they differentiate into functional cells to form diverse tissues of the root. The balance between the maintenance and consumption of the root apical meristem is governed by cell-to-cell communications. Receptor-like protein kinases (RLKs), a group of signaling molecules localized on the cell surface, have been implicated in sensing multiple endogenous and environmental signals for plant development and stress adaptation. Over the past two decades, various RLKs and their ligands have been revealed to participate in regulating root meristem homeostasis. In this review, we focus on the recent studies about RLK-mediated signaling in regulating the maintenance and consumption of the root apical meristem.

Isthmus Incidence in Human Permanent Mandibular First Molars of a South Indian Population: A Cone-Beam Computerized Tomographic Study.

AIM: This study aimed to analyze incidence of isthmus in human permanent mandibular first molar teeth using cone-beam computed tomographic imaging techniques in a South Indian population. MATERIALS AND METHODS: Three hundred permanent mandibular first molar teeth were collected, cleaned, and stored in normal saline. They were divided into groups (GPs) I and II based on number of roots, and were further subdivided (right and left [RL] subgroups A and B for GP I; and RL subgroups C and D for GP-II). Samples were processed and isthmus incidence was evaluated by cone-beam tomography, compared, and statistically analyzed. RESULTS: Overall in mandibular first molars, the isthmus incidence in mesial root was 97.2%, distal root was 39%, and distolingual root was 0%. There was no statistically significant difference between the right and left mandibular first molar teeth with regard to incidence of isthmus (P > 0.05). There was an incidence of type I (38.67%), type II (56.33%), type III (3%), and type IV (2%) isthmuses in mesial root and type I (12.33%), type II (16%), and type III (10.67%) in distal root. CONCLUSION: Incidence of isthmus was very high in the mesial root of the mandibular first molar and should be factored during nonsurgical and surgical endodontic treatment procedures to achieve successful treatment outcomes.

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

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

A Mandibular First Molar with Three Distal Canals: A Case Report and Literature Review.

For a successful root canal treatment, it is critical for a clinician to have complete knowledge of the root canal morphology. There are numerous cases in literature concerning the unusual anatomy of mandibular first molars. This report presents a case of a mandibular first molar with three distal canals. An overview of the types and numbers of the common anatomic forms of this tooth also is presented, as is a summary of published anomalies.

Measurement of Differential Na(+) Efflux from Apical and Bulk Root Zones of Intact Barley and Arabidopsis Plants.

Rapid sodium cycling across the plasma membrane of root cells is widely thought to be associated with Na(+) toxicity in plants. However, the efflux component of this cycling is not well understood. Efflux of Na(+) from root cells is believed to be mediated by Salt Overly-Sensitive-1, although expression of this Na(+)/H(+) antiporter has been localized to the vascular tissue and root meristem. Here, we used a chambered cuvette system in which the distal root of intact salinized barley and Arabidopsis thaliana plants (wild-type and sos1) were isolated from the bulk of the root by a silicone-acrylic barrier, so that we could compare patterns of (24)Na(+) efflux in these two regions of root. In barley, steady-state release of (24)Na(+) was about four times higher from the distal root than from the bulk roots. In the distal root, (24)Na(+) release was pronouncedly decreased by elevated pH (9.2), while the bulk-root release was not significantly affected. In A. thaliana, tracer efflux was about three times higher from the wild-type distal root than from the wild-type bulk root and also three to four times higher than both distal- and bulk-root fluxes of Atsos1 mutants. Elevated pH also greatly reduced the efflux from wild-type roots. These findings support a significant role of SOS1-mediated Na(+) efflux in the distal root, but not in the bulk root.

Mandibular first molar with three distal canals.

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

A study on the C-shaped root canal system of mandibular second molar / 대한치과보존학회지

C-shaped canals are known to present a complex canal anatomy with numerous fins connecting individual canals, thus requiring supplementary effort to accomplish a successful root canal treatment. This study examined the frequency of the C-shaped mandibular second molars and interrelation between the clinical records and radiographs to recognize them treated in the Department of Conservative Dentistry of the Chosun University Dental Hospital during a six-year period (1998 - 2004). This study reviewed the clinical records of 227 patients who underwent root canal treatment of the mandibular second molars. After opening the chamber, those cases with C-shaped orifices in the pulpal floor were selected, and the C-shaped root canal types were classified according to Melton's criteria. Three experienced dentists evaluated the radiographs of the C-shaped mandibular second molar on a viewer using a magnifying glass in order to determine if the root apex was fused or separated, the distal root canal was either centered or mesial shifted in the distal root, and if there was bilateral symmetry in a panorama. In conclusion, there is a high frequency of C-shaped mandibular second molars in Koreans. Simultaneous interpretation of the root shape and distal root canal using the preoperative, working length and post-treatment radiographs is important for diagnosing a C-shaped mandibular second molar.