Root and Root Canal Morphology of Premolars in a Sample of the Lebanese Population: Clinical Considerations

ABSTRACT Objectives: The aim of this study was to investigate the anatomy of the maxillary and mandibular premolars among a sample of the Lebanese population and to explore their incidence by sex and the symmetry between the left and right sides. Materials and Methods: This retrospective analysis of 250 cone-beam computed tomography (CBCT) scans consisted of 960 maxillary and 972 mandibular premolars. Roots, canals, and morphology types were recorded. Vertucci’s classification was used to categorize the canal morphologies. Fisher’s exact and chi-square tests (P≤.05) were applied. Results: The majority of maxillary first premolars had two roots (85.3%) with two canals (91.3%). Most of the maxillary second premolars showed one root (79.8%). Two-root canals (53.55%) were more common than one canal (44.2%). The three-root, three-canal morphology was rarely spotted in the maxillary first (0.4%) and second premolars (2.3%). The one-root (99.2%) and one-canal (84.5%) morphologies were most frequently located in the mandibular first and second premolars (100%, 88.6%), and two canals being less common (15.5%, 11.4%) correct same as before. The total prevalence of premolars with a complex root canal morphology was 62.4%, found in types II, III, and V to VIII. Men had significantly more roots and root canals in their maxillary first premolars than women (P≤.05). No significant differences were observed between the contralateral premolars (P\u3e.05). Conclusions: Premolars displayed wide variations in root and root canal morphology and symmetry between the contralateral premolars. Keywords: cone-beam computed tomography (CBCT), mandibular premolars, maxillary premolars, root canal anatomy, root canal configuration, sex distribution, symmetry. Objectif Cette étude vise à examiner le nombre de racines, les canaux radiculaires et la morphologie des canaux des prémolaires maxillaires et mandibulaires, au sein d’une population libanaise. Matériels et méthodes 250 images CBCT de 960 prémolaires maxillaires et 972 prémolaires mandibulaires ont été analysées rétrospectivement. Les tests de Fisher Exact et du Chi-Carré (P \u3c 0,05) ont été appliqués pour évaluer le nombre de racines et de canaux radiculaires, la fréquence et la symétrie entre les côtés gauche et droit, ainsi que l’incidence au sein du sexe. La classification de Vertucci a été utilisée pour classer les morphologies des canaux. Résultats Les premières prémolaires maxillaires étaient principalement caractérisées par deux racines (1 racine : 14,4%, 2 racines: 85,3% et 3 racines: 0,4%), avec deux canaux (91,3%). Une racine a été observée dans de nombreuses deuxièmes prémolaires maxillaires (79,8 %). Cependant, deux canaux radiculaires (53,55 %) étaient plus fréquents qu’un canal (44,2 %). Trois racines et trois canaux ont rarement été repérés dans les premières (0,4 %, 0,4 %) et les deuxièmes prémolaires maxillaires (2,3 %, 2,3 %). Une racine avec un canal était localisée respectivement le plus fréquemment dans la première (99,2 %, 84,5 %) et la deuxième prémolaire mandibulaire (100 %, 88,6 %), bien que deux canaux soient moins fréquents (15,5 %, 11,4 %). Des prémolaires avec une anatomie complexe du canal radiculaire ont été trouvées avec une prévalence de 16,2% allant du type II, III et de V à VIII. Les résultats ont également montré des différences entre les sexes : les hommes avaient remarquablement plus de racines et de canaux radiculaires dans leurs premières prémolaires maxillaires que les femmes (P \u3c 0,05). Aucune différence statistique n’a été observée entre les paires prémolaires controlatérales (P ³ .5). Conclusion Au sein de cette sous-population libanaise, les prémolaires maxillaires et mandibulaires présentaient de grandes variations dans la morphologie des racines et des canaux radiculaires, et une symétrie entre les paires controlatérales. Ces résultats susciteraient un intérêt clinique pour les praticiens et les chercheurs. Mots-clés : CBCT, prémolaires mandibulaires, prémolaires maxillaires, anatomie canalaire, configuration canalaire, symétrie, sexe

Influence of the EndoActivator Irrigation System on Dentinal Tubule Penetration of a Novel Tricalcium Silicate-Based Sealer

This study compared the effects of a conventional endodontic needle with an agitation system on a novel tricalcium silicate-based sealer (NTS) in terms of dentinal tubule penetration and interfacial adaptation to a root canal. Fifty single-rooted, recently-extracted human maxillary central incisors were randomly distributed into two homogeneous groups characterized by two different final cleansing systems: Conventional endodontic needle, or EndoActivator®. After instrumentation, all the teeth were filled with the gutta-percha single cone technique in conjunction with the novel tricalcium silicate-based sealer. Teeth were horizontally sectioned at 1 and 5 mm from the apex and were observed under a confocal laser scanning microscope (CLSM) at five magnifications. The maximum, mean, and the circumferential percentage of the sealer penetration inside the tubules were measured. Moreover, the gap width was evaluated using Image J software (National Institutes of Health, Bethesda, MD). EndoActivator® did not result in a significantly higher circumferential percentage of sealer penetration than conventional irrigation (p > 0.05). However, the gap width was significantly lower with EndoActivator®, compared to conventional needles at both 1 mm (p = 0.035) and 5 mm (p = 0.038). The EndoActivator® irrigation system did not significantly improve the NTS penetration, as compared to the conventional endodontic needle irrigation. Activation of the irrigation reduced the gap width significantly

Influence of the Maxillary Sinus on the Accuracy of the Root ZX Apex Locator: An Ex Vivo Study

This study evaluated the accuracy of the Root ZX (J. Morita, Tokyo, Japan) electronic apex locator in determining the working length when palatal maxillary molar roots are in a relationship with the sinus. Seventeen human maxillary molars with vital pulp were scheduled for an extraction and implant placement as part of a periodontal treatment plan. The access cavity was prepared, and a #10 K file (Dentsply Maillefer, Ballaigues, Switzerland) was inserted into the palatal root using the Root ZX apex locator in order to determine the electronic working length (EWL); then, the teeth were extracted. To determine the real working length (RWL), a #10 K file was introduced into the root canal until its tip touched a glass plate. EWL and RWL were compared. Images reconstructed with CBCT (cone beam computerized tomography) revealed that eight palatal roots were related to the maxillary sinus, whereas nine were not. The results showed a significant difference between the EWL and the RWL of the palatal roots related to the sinus (p < 0.001). No significant difference was observed in measurements of roots not in contact with the sinus (p > 0.05). Within the study limitations, the reliability of Root ZX was influenced by the relationship of the roots with the maxillary sinus

Influence of the EndoActivator Irrigation System on Dentinal Tubule Penetration of a Novel Tricalcium Silicate-Based Sealer

This study compared the effects of a conventional endodontic needle with an agitation system on a novel tricalcium silicate-based sealer (NTS) in terms of dentinal tubule penetration and interfacial adaptation to a root canal. Fifty single-rooted, recently-extracted human maxillary central incisors were randomly distributed into two homogeneous groups characterized by two different final cleansing systems: Conventional endodontic needle, or EndoActivator®. After instrumentation, all the teeth were filled with the gutta-percha single cone technique in conjunction with the novel tricalcium silicate-based sealer. Teeth were horizontally sectioned at 1 and 5 mm from the apex and were observed under a confocal laser scanning microscope (CLSM) at five magnifications. The maximum, mean, and the circumferential percentage of the sealer penetration inside the tubules were measured. Moreover, the gap width was evaluated using Image J software (National Institutes of Health, Bethesda, MD). EndoActivator® did not result in a significantly higher circumferential percentage of sealer penetration than conventional irrigation (p > 0.05). However, the gap width was significantly lower with EndoActivator®, compared to conventional needles at both 1 mm (p = 0.035) and 5 mm (p = 0.038). The EndoActivator® irrigation system did not significantly improve the NTS penetration, as compared to the conventional endodontic needle irrigation. Activation of the irrigation reduced the gap width significantly

Dentinal tubule penetration of AH Plus, BC Sealer and a novel tricalcium silicate sealer: a confocal laser scanning microscopy study

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Gastrointestinal cancer cells treatment with bevacizumab activates a VEGF autoregulatory mechanism involving telomerase catalytic subunit hTERT via PI3K-AKT, HIF-1α and VEGF receptors

<div><p>Background</p><p>Targeting angiogenesis has been considered a promising treatment of choice for a large number of malignancies, including gastrointestinal cancers. Bevacizumab is an anti-vascular endothelial growth factor (anti-VEGF) being used for this purpose. However, treatment efficacy is largely questioned. Telomerase activity, responsible for cancer cell immortality, is detected in 85–95% of human cancers and is considered a potential regulator of VEGF. The aim of our study was to investigate the interrelationship between VEGF and hTERT in gastrointestinal cancers and to explore cell response to a combined inhibition of telomerase and VEGF.</p><p>Methods</p><p>AGS (gastric cancer), Caco-2 (colorectal cancer) and HepG2/C3A (hepatocellular carcinoma), were treated with telomerase inhibitors BIBR-1232 (10μM) and costunolide (10μM), with bevacizumab (Avastin® at 5 ng/ml or 100μg/ml) or with a combination of both types of inhibitors. VEGF and hTERT mRNA levels, and telomerase activity were detected by RT-PCR. VEGF levels were quantified by ELISA. Telomerase was knocked down using hTERT siRNA and hTERT was overexpressed in the telomerase negative cell line, Saos-2 (osteosarcoma), using constructs expressing either wild type hTERT (hTERT-WT) or dominant negative hTERT (hTERT-DN). Tube formation by HUVECs was assessed using ECMatrix™ (EMD Millipore).</p><p>Results</p><p>Our results showed that telomerase regulates VEGF expression and secretion through its catalytic subunit hTERT in AGS, Caco2, and HepG2/C3A, independent of its catalytic activity. Interestingly, VEGF inhibition with bevacizumab (100μg/ml) increased hTERT expression 42.3% in AGS, 94.1% in Caco2, and 52.5% in HepG2/C3A, and increased telomerase activity 30-fold in AGS, 10.3-fold in Caco2 and 8-fold in HepG2/C3A. A further investigation showed that VEGF upregulates hTERT expression in a mechanism that implicates the PI3K/AKT/mTOR pathway and HIF-1α. Moreover, bevacizumab treatment increased VEGFR1 and VEGFR2 expression in cancer cells and human umbilical vein endothelial cells (HUVECs) through hTERT. Thus, the combination of bevacizumab with telomerase inhibitors decreased VEGF expression and secretion by cancer cells, inhibited VEGFR1 and VEGFR2 upregulation, and reduced tube formation by HUVECs.</p><p>Conclusions</p><p>Taken together, our results suggest that bevacizumab treatment activates a VEGF autoregulatory mechanism involving hTERT and VEGF receptors and that an inhibition of this pathway could improve tumor cell response to anti-VEGF treatment.</p></div

Telomerase regulates VEGF secretion and expression independently of telomerase activity.

<p>(A, B) VEGF secretion was assessed by ELISA following a 48-h treatment with telomerase inhibitors BIBR-1532 (10 <i>μ</i>M) and costunolide (10 <i>μ</i>M), and after 72 h of hTERT knockdown with siRNA. (C, D) Total RNAs were isolated from the cells treated in (A), and VEGF expression was analyzed by real-time PCR with GAPDH as the internal control. (E, F, G) Saos-2 cells were transiently transfected with an empty vector, hTERT-WT, and hTERT-DN. hTERT (E) and VEGF expression (F) were quantified by real-time PCR. Secreted VEGF was quantified by ELISA (G). Results were expressed as the mean ±SD from a minimum of three experiments.</p

Bevacizumab increases VEGFR1 and VEGFR2 expression.

<p>(A, B) Telomerase inhibitors were combined to bevacizumab (100 <i>μ</i>g/ml) and then VEGFR1 (A) and VEGFR2 (B) were quantified by real-time PCR. (C, D) Cells were transiently transfected with either control siRNA or hTERT siRNA and treated with bevacizumab (100 <i>μ</i>g/ml). VEGFR1 (C) and VEGFR2 (D) were quantified by real-time qPCR. (E, F) HUVECs were cultured in the presence of telomerase inhibitors for 48 h and hTERT siRNA for 72 h. The expression of VEGFR1 (E) and VEGFR2 (F) were quantified by real-time PCR. Results were expressed as the mean ± SD from three experiments.</p

Telomerase regulates VEGF, VEGFR1, and VEGFR2 expression.

<p>AGS (A), Caco2 (B), and HepG2/C3A (C) cells were treated with control siRNA or hTERT siRNA with or without bevacizumab, and VEGF secretion was evaluated by ELISA. (D, E) Cells were treated with BIBR-1532, costunolide, or transiently transfected with hTERT siRNA for 72h. VEGFR1 (D) and VEGFR2 (E) transcript amounts were quantified with real-time PCR. (F, G) Saos-2 cells were transiently transfected with an empty vector, hTERT-WT or hTERT-DN. VEGFR1 (F) and VEGFR2 (G) were then quantified with real-time PCR. Results were expressed as the mean ± SD from three experiments.</p

Telomerase regulates tube formation by HUVECs.

<p>HUVECs previously treated with BIBR-1532 (10 μM), costunolide (10 μM), bevacizumab (5 ng/ml or 100 μg/ml), or hTERT siRNA were cultured on an extracellular matrix (ECM) in the presence or absence of recombinant VEGF165 (50 ng/ml). Angiogenesis began after 4 hours, and tube formation was then visualized after 6 hours, using an inverted microscope (100X).</p