Abstract Introduction Current push-out experimental methods used in endodontic research should be improved. This study introduced a novel dentin push-out bond strength model that uses micro–computed ...tomography (μCT). Methods Roots filled with gutta-percha cones and different resin-based sealers ( n = 10) were sectioned transversely to obtain two 2-mm-thick slices per root third. The first slice was subjected to a push-out test by using a material testing stage fitted inside a μCT scanner. The apparatus was scanned before and after the test to evaluate areas of filling material ruptures. The images provided by μCT were also used to generate models for a 3-dimensional finite element analysis. Confocal laser scanning microscopy was used to assess failure modes after the test and to measure interfacial gaps in slices not subjected to push-out. Bond-strength and gap data were statistically analyzed ( P < .05). Results Proper coefficients of variation (average less than 30%) were observed for all the experimental conditions. The finite element analysis helped explain the results of bond strength and root-filling ruptures. A significant, moderate, indirect correlation was observed between the bond strength and gaps. Conclusions The micromechanical model with the μCT images resulted in a consistent root-filling bond strength evaluation.
Abstract Introduction This ex vivo study evaluated the disinfecting and shaping ability of 3 protocols used in the preparation of mesial root canals of mandibular molars by means of correlative ...bacteriologic and micro–computed tomographic (μμCT) analysis. Methods The mesial canals of extracted mandibular molars were contaminated with Enterococcus faecalis for 30 days and assigned to 3 groups based on their anatomic configuration as determined by μCT analysis according to the preparation technique (Self-Adjusting File ReDent-Nova, Ra’anana, Israel, Reciproc VDW, Munich, Germany, and Twisted File SybronEndo, Orange, CA). In all groups, 2.5% NaOCl was the irrigant. Canal samples were taken before (S1) and after instrumentation (S2), and bacterial quantification was performed using culture. Next, mesial roots were subjected to additional μCT analysis in order to evaluate shaping of the canals. Results All instrumentation protocols promoted a highly significant intracanal bacterial reduction ( P < .001). Intergroup quantitative and qualitative comparisons disclosed no significant differences between groups ( P > .05). As for shaping, no statistical difference was observed between the techniques regarding the mean percentage of volume increase, the surface area increase, the unprepared surface area, and the relative unprepared surface area ( P > .05). Correlative analysis showed no statistically significant relationship between bacterial reduction and the mean percentage increase of the analyzed parameters ( P > .05). Conclusions The 3 instrumentation systems have similar disinfecting and shaping performance in the preparation of mesial canals of mandibular molars.
Abstract Introduction This study evaluated the disinfecting ability of chemomechanical preparation with rotary nickel-titanium instruments, followed by 2 distinct adjunctive procedures in the root ...canals of extracted mandibular molars by means of a correlative analytical approach. Methods Twenty-two extracted mandibular molars were selected and anatomically matched between groups on the basis of micro–computed tomographic analysis. In the first phase of the experiment, root canals were contaminated with Enterococcus faecalis and subjected to chemomechanical preparation with BT RaCe instruments and 2.5% NaOCl irrigation. Then either XP-Endo Finisher instrument or passive ultrasonic irrigation was used to supplement disinfection. Micro–computed tomography was used to show whether the percentage of unprepared areas correlated to bacterial counts. In the second phase, the same teeth were contaminated once again, and the adjunctive procedures were used. Samples from the isthmus area of mesial roots and the apical 5-mm fragment of distal roots were obtained by cryopulverization. Samples taken before and after treatment steps in both phases were evaluated by quantitative polymerase chain reaction and statistically analyzed. Results In phase 1, preparation in both groups resulted in substantial decrease of bacterial counts ( P < .001). The adjunctive approaches led to a further small bacterial reduction, which was significant for XP-Endo Finisher ( P < .05). No significant differences were observed between groups for persisting bacterial counts. Correlative analysis revealed no statistically significant relationship between bacterial reduction and the percentage of unprepared areas ( P > .05). In phase 2, both methods had significant antibacterial effects in the main canal, but none of them could predictably disinfect the isthmus/recess areas. Conclusions Both XP-Endo Finisher and passive ultrasonic irrigation exhibited antibacterial effectiveness, but only the former caused a significant reduction in the bacterial counts after chemomechanical preparation. None of them were effective in predictably disinfecting the isthmus/recess areas.
Abstract Introduction The aim of this study was to assess the efficacy of lasers in removing filling remnants from oval-shaped canals after retreatment procedures with rotary instruments using ...micro–computed tomographic imaging. Methods The root canals of 42 mandibular canines were prepared and obturated using the warm vertical compaction technique. Retreatment was performed with rotary instruments, and the specimens were distributed in 3 groups ( n = 14) according to the laser device used in a later stage of retreatment procedure: Er:YAG, Er:YAG laser–based photon-induced photoacoustic streaming, and Nd:YAG. The specimens were scanned in a micro–computed tomographic device after root canal filling and each stage of retreatment at a resolution of 13.68 μm. The percentage differences of the remaining filling material before and after laser application within and between groups were statistically compared using the paired sample t test and 1-way analysis of variance test, respectively. Significance level was set at 5%. Results Overall, filling residues were located mainly in the apical third and into canal irregularities after the retreatment procedures. After using rotary instruments, the mean percentage volume of the filling remnants ranged from 13%–16%, with no statistical significant difference between groups ( P > .05). Within groups, additional laser application had a significant reduction in the amount of the remaining filling materials ( P < .05). A comparison between groups showed that Er:YAG laser application after the use of rotary instruments had a significantly higher removal of filling remnants (∼13%) than Er:YAG laser–based photon-induced photoacoustic streaming (∼4%) and Nd:YAG (∼3%) ( P < .05). Conclusions None of the retreatment procedures completely removed the filling materials. The additional use of lasers improved the removal of filling material after the retreatment procedure with rotary instruments.
Abstract Introduction The purpose of this ex vivo study was to evaluate the percentage reduction of accumulated hard tissue debris (AHTD) in the mesial root canal system of mandibular molars under ...different final irrigation regimens by means of micro–computed tomographic imaging. Methods Sixty curved mesial roots of mandibular molars with 2 independent canals joint apically by an isthmus (Vertucci type II) were selected. Specimens were scanned at a resolution of 12.5 μm, anatomically matched, and distributed into 3 groups ( n = 20) according to the preparation protocol: Self-Adjusting File (SAF; ReDent Nova, Ra'anana, Israel), Reciproc (VDW GmbH, Munich, Germany), and Revo-S (Micro-Mega, Besançon, France) systems. Then, each group was subdivided into 2 subgroups ( n = 10) according to the final irrigation protocol with the SAF or EndoVac system (Discus Dental, Culver City, CA). The percentage volume and percentage reduction of AHTD after root canal preparation and final irrigation protocols were statistically compared using 1-way analysis of variance, the paired sample and the independent Student's t tests. The level of significance was set at 5%. Results Within groups, the mean percentage volume was significantly reduced after the final irrigation procedures in either the SAF (from 1.52%–1.78% to 1.01%–1.20%) or EndoVac (from 2.11%–2.23% to 1.31%–1.52%) subgroups ( P < .05). In the experimental groups, the mean percentage reduction of AHTD ranged from 29.15%–39.90% after the irrigation protocols, with no statistical difference between groups ( P > .05). Conclusions None of the irrigation approaches succeeded in rendering the mesial root canal system free of AHTD. A similar percentage reduction of AHTD was achieved after final irrigation protocols using either the SAF or EndoVac system.
Abstract Introduction Bioinformatics has emerged as an important tool to analyze the large amount of data generated by research in different diseases. In this study, gene expression for radicular ...cysts (RCs) and periapical granulomas (PGs) was characterized based on a leader gene approach. Methods A validated bioinformatics algorithm was applied to identify leader genes for RCs and PGs. Genes related to RCs and PGs were first identified in PubMed, GenBank, GeneAtlas, and GeneCards databases. The Web-available STRING software (The European Molecular Biology Laboratory EMBL, Heidelberg, Baden-Württemberg, Germany) was used in order to build the interaction map among the identified genes by a significance score named weighted number of links. Based on the weighted number of links, genes were clustered using k-means. The genes in the highest cluster were considered leader genes. Multilayer perceptron neural network analysis was used as a complementary supplement for gene classification. Results For RCs, the suggested leader genes were TP53 and EP300 , whereas PGs were associated with IL2RG , CCL2 , CCL4 , CCL5 , CCR1 , CCR3 , and CCR5 genes. Conclusions Our data revealed different gene expression for RCs and PGs, suggesting that not only the inflammatory nature but also other biological processes might differentiate RCs and PGs.
Abstract Introduction The greatest reduction in microhardness of the most superficial layer of dentin of the root canal lumen is desired. The use of chelating agents during biomechanical preparation ...of root canals removes smear layer, increasing the access of the irrigant into the dentin tubules to allow adequate disinfection, and also reduces dentin microhardness, facilitating the action of endodontic instruments. This study evaluated the effect of different chelating solutions on the microhardness of the most superficial dentin layer from the root canal lumen. Methods Thirty-five recently extracted single-rooted maxillary central incisors were instrumented, and the roots were longitudinally sectioned in a mesiodistal direction to expose the entire canal extension. The specimens were distributed in seven groups according to the final irrigation: 15% EDTA, 10% citric acid, 5% malic acid, 5% acetic acid, apple vinegar, 10% sodium citrate, and control (no irrigation). A standardized volume of 50 μL of each chelating solution was used for 5 minutes. Dentin microhardness was measured with a Knoop indenter under a 10-g load and a 15-second dwell time. Data were analyzed statistically by one-way analysis of variance and Tukey-Kramer multiple-comparison test at 5% significance level. Results EDTA and citric acid had the greatest overall effect, causing a sharp decrease in dentin microhardness without a significant difference ( p > .05) from each other. However, both chelators differed significantly from the other solutions ( p < .001). Sodium citrate and deionized water were similar to each other ( p > .05) and did not affect dentin microhardness. Apple vinegar, acetic acid, and malic acid were similar to each other ( p > .05) and presented intermediate results. Conclusion Except for sodium citrate, all tested chelating solutions reduced microhardness of the most superficial root canal dentin layer. EDTA and citric acid were the most efficient.
Abstract Introduction This study evaluated the pulpal and periapical responses of dogs' teeth after pulpotomy and pulp capping with a new tricalcium silicate–based cement (Biodentine) when compared ...with mineral trioxide aggregate (MTA) by radiographic, histopathologic, and histomicrobiological analyses. Methods Sixty roots (30 teeth) of dogs were divided into 2 groups, Biodentine ( n = 36 roots) and ProRoot MTA (control, n = 24 roots). Animals were killed after 120 days, and the teeth were subjected to histotechnical processing (hematoxylin-eosin and Brown and Brenn staining). Qualitative and quantitative histopathologic data were analyzed by Fisher exact and Mann-Whitney tests (α = 0.05). Results Radiographically, mineralized tissue bridge formation was observed in more specimens treated with Biodentine (96.8%) than with MTA (72.2%) ( P = .02). Integrity of the lamina dura and absence of periapical bone rarefaction and root resorption (external and internal) were observed in all specimens. Histopathologic and histomicrobiological analyses revealed mineralized tissue bridge formation, pulpal vitality, odontoblast layer integrity, preserved periodontal ligament, and absence of bone or root resorption and microorganisms in both groups. Although the bridges formed at the amputation site had similar morphology, they were significantly thicker in the Biodentine group ( P < .0001). Comparison between the radiographic and histopathologic results showed that radiographic visualization of more bridges in the Biodentine group was related to bridge thickness because radiographic diagnosis was flawed for bridges with thickness less than 0.5 mm. Fluorescence microscopy improved the visualization of bridge structure. Conclusions Biodentine presented tissue compatibility and allowed for mineralized tissue bridge formation after pulpotomy in all specimens with similar morphology and integrity to those formed with use of MTA. Periapical radiographs failed in detecting mineralized tissue bridges with thickness less than 0.5 mm.
Abstract This study proposed smaller dimensions for samples used in solubility and dimensional change tests of root filling materials on the basis of American National Standard Institute/American ...Dental Association (ANSI/ADA) Specification No. 57. The volume, mass, and density of the test samples were determined, and 6 different samples of smaller dimensions were proposed for each test. Endofill and AH Plus sealers were used in the tests. For the solubility test, 2 samples were weighted, stored in distilled and dionized water for 24 hours, dried, and weighed again. Solubility was calculated by using samples’ weight loss (%). For dimensional change analysis, the samples’ heights were measured before and after immersion in dionized water for 30 days. For both tests, correlation between data of the different groups was observed. Kruskal-Wallis test showed that Endofill sealer presented higher solubility values than AH Plus ( P < .05). The Endofill sealer presented 0.56% of shrinkage and AH Plus 0.62% expansion. Smaller dimensions for test samples used in solubility and dimensional change tests are a viable alternative, decreasing the amount of filling material necessary for executing these tests.
Abstract Introduction This study compared the bond strength, interfacial ultrastructure, and tag penetration of resin-based sealers applied to smear-free radicular dentin using 70% isopropyl alcohol ...as the active final rinse. Methods Eighty root canals were prepared and assigned to 2 groups ( n = 40) according to the drying protocol: paper points or 70% isopropyl alcohol. Then, roots were divided into 4 subgroups ( n = 10) with respect to the sealer and obturation material: AH Plus (Dentsply De Trey GmbH, Konstanz, Germany) and gutta-percha (AH/GP), Hybrid Root SEAL (Sun Medical, Tokyo, Japan) and gutta-percha (HR/GP), Epiphany SE (Pentron Clinical Technologies, Wallingford, CT) and gutta-percha (EP/GP), and Epiphany SE and Resilon (EP/RS). Roots were sectioned, and the push-out test was performed. Failure modes were examined under stereomicroscopy and sealer penetration into the dentinal tubules under scanning electron microscopy. Data were statistically analyzed by 2-way analysis of variance post hoc Tukey tests with a significant level of 5%. Results Overall, canals dried with isopropyl alcohol showed significantly higher bond strength values (2.11 ± 1.74 MPa) than with paper points (1.81 ± 1.73 MPa) ( P < .05). The HR/GP group showed lower bond strength than the AH/GP group ( P < .05) but higher than the EP/GP and EP/RS groups ( P < .05). The most frequent type of failure was cohesive in the AH/GP and HR/GP groups and adhesive in the EP/GP and EP/RS groups. Scanning electron microscopic evaluation revealed better adaptation of the adhesive interface in the AH/GP and HR/GP groups in comparison with the EP/GP and EP/RS groups. Conclusions A final rinse with EDTA and 70% isopropyl alcohol improved the bond strength and penetration of the sealers into dentinal tubules of the root.
