Cyclic Fatigue Life of Two Single File Engine-Driven Systems in Simulated Curved Canals

Introduction: This study aimed to evaluate the cyclic fatigue resistance of two single file engine-driven instruments, Reciproc and NeoNiTi, in simulated root canals. Methods and Materials: Two groups of 15 NiTi endodontic instruments with an identical tip size of 0.25 mm were tested: Reciproc R25 (group A) and NeoNiTi A1 (group B). Cyclic fatigue testing was performed in a stainless steel artificial canal. The simulated canals had a 60° angle and 5-mm radius curvature. The Reciproc instruments were operated using the preset program on torque control electric motor specific for the Reciproc instruments, while the NeoNiTi instruments were operated using the manufacturer recommendation. All instruments were rotated until fracture occurred, and the number of cycles to fracture (NCF) and the length of the fractured tip were recorded and registered. Means and standard deviations of NCF and fragment length were calculated for each system and data were subjected to Student’s t test (P<0.05). Results: A statistically significant difference (P<0.05) was noted between Reciproc and NeoNiTi instruments. NeoNiTi A1 instruments were associated with a significantly higher mean NCF as compared to Reciproc R25 instruments (833±176 vs. 318±87 NCF). There was no significant difference (P>0.05) in the mean length of the fractured fragments between the instruments. Conclusion: NeoNiTi instruments were associated with a significantly higher cyclic fatigue resistance than Reciproc instruments.Keywords: Cyclic Fatigue; NeoNiTi; Reciproc; Single-File System

The Effect of Intracanal Medicaments on Microleakage of Mineral Trioxide Aggregate Apical Plugs

Introduction: The purpose of this in vitro study was to evaluate the effect of calcium hydroxide, double and triple antibiotic paste on the sealing ability of mineral trioxide aggregate (MTA) apical plugs. Methods and Materials: A total of 90 extracted teeth with single canals were prepared and randomly divided into four experimental groups (n=20). Intra-canal medicaments were applied for 3 weeks. MTA was placed through the access opening and condensed to the apical area and then fluid filtration technique was utilized to evaluate sealing ability after 1, 7, 14 and 30 days. Results: Triple antibiotic paste significantly reduced the sealing ability of MTA plug compared with double antibiotic paste (P=0.024) and normal saline (P=0.04) groups on day 1. The sealing ability was not different on days 14 and 30 between experimental groups (P>0.05). Conclusion: All medicaments can be used without any long term effect on microleakage.Keywords: Calcium Hydroxide; Double Antibiotic Paste; Endodontic Regeneration; Microleakage; Triple Antibiotic Past

Cone-Beam Computed Tomography Assessment of Root Canal Transportation by Neoniti and Reciproc Single-File Systems

Introduction: The aim of this in vitro study was to compare the canal transportation of two single-file engine-driven systems, Neoniti and Reciproc, using cone-beam computed tomography (CBCT). Methods and Materials: Forty-five non-calcified roots with mature apices and apical curvature of 15-30 degrees were selected from extracted human maxillary molars for this study. Samples were randomly divided into two groups (n=20) and a control group (n=5) and canal preparation with either system was performed according to manufacturers' instructions. Pre- and post-instrumentation CBCT images were captured and the amount of canal transportation within the files was calculated at levels of 3, 4, and 5 mm from the apex. The independent sample t-test was used to analyze the statistical significance between the two groups. The level of significance was defined at 0.05. Results: Reciproc created more canal transportation compared to Neoniti in both mesiodistal and buccolingual directions. The difference between the two systems was statistically significant in all evaluated distances from the apex (P<0.001). During this study fracture of one file (25/0.08) in the Neoniti group occurred. Conclusion: Neoniti and Reciproc systems have significant difference in terms of creating canal transportation. Reciproc created more canal transportation in buccolingual and mesiodistal dimensions.Keywords: Canal Transportation; Cone-Beam Computed Tomography; Neoniti; Reciproc; Root Canal Preparatio

Comparison of Endodontic Treatment Results Yielded from Using Normal Saline with IKI Final Rinse or NaOCl Irrigation: A 30-Month Follow-up Study

Introduction: The aim of this clinical trial was to evaluate and compare the endodontic treatment results of teeth with apical periodontitis after thirty-month recall with two different irrigation regimen: normal saline followed by Iodine Potassium Iodide (IKI) or sodium hypochlorite (NaOCl) irrigation alone. Materials and Methods: Twenty seven patients (30 teeth) who had been included in the first part of our antimicrobial survey were recalled. In previous stage, root canal treatments were performed using either normal saline with IKI final rinse (n=15) or NaOCl (n=15) as irrigating solutions. Bacterial samples were taken before and after instrumentation. In this stage, three patients (6 teeth) were excluded from the follow-up schedule since they did not respond to the recall requests. The remaining 24 subjects (12 teeth in each NaOCl and IKI group) were examined clinically and radiologically. Post-operative and follow-up images were coded, blindly evaluated and given a periapical score according to PAI scoring system. The outcome was assessed in two ways; first, the changes in PAI score from base line to the follow-up evaluation in each group were assessed by wilcoxon signed rank test. In addition, Mann-Whitney U test was used to compare the differences between the post-operative and follow-up images of treatment groups. Second, the dichotomous variables as “healed” or “not healed” were compared. Results: The Median (Min, Max) PAI scores for NaOCl group and IKI group were both 5 (3, 5) for immediate post-operative radiographs and declined to 1 (1, 2) and 2 (1, 2), respectively. A statistically significant decrease in PAI score from the base line to the follow-up evaluation was seen in both groups (P=0.002). The decrease in NaOCl group was higher significantly in comparison to IKI group (P=0.036). One hundred percent of the teeth were healed in both groups (PAI≤2) and no teeth showed any abnormal clinical findings. Conclusion: Root canal irrigation with NaOCl resulted in a significant higher decrease in PAI scores in comparison to irrigation with normal saline followed by IKI final rinse. Although, according to results of 30-months recall, complete bone formation was observed in all samples in both groups and no teeth showed any abnormal clinical findings. These findings depict the weight of all important clinical and biological factors which together impact the results of a successful endodontic treatment

A Comparison of Apical Transportation in Severely Curved Canals Induced by Reciproc and BioRaCe Systems

Introduction: Preserving the apical root structure during cleaning and shaping of the canal has always been a challenge in endodontics particularly when the root canals are curved. The purpose of this in vitro study was to compare the apical transportation induced by the Reciproc and BioRaCe rotary systems in preparing the mesiobuccal root canal of the human maxillary molars. Materials and Methods: The mesiobuccal canals of sixty extracted maxillary molars with curvature angle of 25-35˚ were selected and randomly assigned into two groups. Each canal was prepared by either Reciproc or BioRaCe rotary systems. A double-digital radiographic technique and AutoCAD software were used to compare the apical transportation at 0.5, 1, 2, 3, 4 and 5 mm distances from the working length (WL). The distance between the master apical rotary file and the initial K-file in the superimposed radiographs determined the amount of apical transportation. An independent t-test was used to compare the groups. The statistical significant level was set at 0.05. Results: Apical transportation of the Reciproc group was significantly greater than the BioRaCe group in all distances (P<0.001). The maximum apical transportation occurred in the Reciproc group at 0.5 mm from the WL (0.048±0.0028 mm) and the minimum occurred for BioRaCe at 5 mm from the WL (0.010±0.0005 mm). Conclusions: The Reciproc system produced significantly more apical transportation than the BioRaCe, but this fact does not seem to negatively alter the clinical success or quality of root canal treatment

In Vivo Biocompatibility of an Ionic Liquid-protected Silver Nanoparticle Solution as Root Canal Irrigant

Introduction: The aim of this study was to assess the biocompatibility of positively charged imidazolium-based ionic liquid-protected nanosilver solution (AgNPs) root canal irrigant. Methods and Materials: Eighteen male 4- to 5-month old Sprague-Dawley rats, weighing 200-300 gr were selected and randomly divided into 5 groups: Normal saline 0.9% (group 1), 5.25% NaOCl (group 2), 2.5% NaOCl (group 3), 2.0% chlorhexidine solution (group 4) and AgNPs at 5.7×10-8 M/L (group 5) were randomly injected in 5 sites of dorsal skin of each rat. Tissue inflammatory reaction were evaluated histopathologically after 2 h, 48 h and 14 days. Statistical analysis was done with SPSS version 21 and the Kruskal-Wallis H and Dunn tests were used to find statistically significant differences. The level of significance was set at 0.05. Result: All solutions irritated the highest tissue response after 48 h. Group 1 showed lower inflammatory response compared to groups 2 and 4 (P<0.05). Group 2 displayed higher inflammatory response in comparison with group 5 (P<0.05). Tissue reaction to group 5 was not more severe than the reaction to group 3 or 4. It also would irritate less inflammatory response compared to group 2 (P<0.05). Conclusion: Comparing with NaOCl and CHX, it is possible to label AgNPs as a tissue compatible agent. Keywords: Biocompatibility; Root Canal Irrigant; Silver Nanoparticl

The Effect of Calcium Chloride on Push-Out Bond Strength of Calcium-Enriched Mixture Cement and Mineral Trioxide Aggregate

Introduction: This in vitro study investigated the effect of adding 10% calcium chloride (CaCl2) on push out bond strength of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA) to root canal dentin. Methods and Materials: A total of 120 root dentin slices with 2 mm thickness were prepared from sixty single-rooted human teeth. Dentinal discs were enlarged to achieve 1.3 mm diameter. The specimens were randomly allocated into eight groups (n=15). Dentin discs were filled with either CEM cement or MTA with or without CaCl2 and the push out test was performed after 3 and 21 days. Data were analyzed with two-way ANOVA test. The level of significance was set at 0.05. Results: There was an interaction effect amongst all groups (P=0.028). After 3 days, CEM cement showed a significantly lower bond strength than other groups (P<0.05) while MTA demonstrated significantly higher bond strength than CEM cement with or without CaCl2 (P=0.001). After 21 days, CEM cement with or without CaCl2 had no significant difference with other groups (P>0.05). However, the bond strength of MTA decreased when CaCl2 was added (P=0.011). Conclusion: The addition of 10% CaCl2 increased the push out bond strength of CEM cement and improved it over time; while, this substance aggravated this property for MTA.Keywords: Calcium Chloride; Calcium-Enriched Mixture Cement; Mineral Trioxide Aggregate; Push-Out Bond Strengt

Antimicrobial Efficacy and Cytocompatibility of Calcium Hypochlorite Solution as a Root Canal Irrigant: An in Vitro Investigation

Introduction: The purpose of this study was to compare the antimicrobial efficacy of sodium hypochlorite (SH) and calcium hypochlorite (CH) against Enterococcus faecalis (E. faecalis) using quantitative real-time polymerase chain reaction (qPCR) analysis and also to compare their cytocompatibility on L929 murine fibroblasts using Mossman’s tetrazolium toxicity (MTT) assay. Methods and Materials: A broth micro-dilution susceptibility test was used to determine the minimum inhibitory concentration (MIC) of each irrigant against E. faecalis. Then, the root canals of 50 mature extracted human mandibular premolars were contaminated with E. faecalis and were randomly divided into three groups according to the irrigant used (n=20). Canals were irrigated with SH in group I (n=20) and CH in group II (n=20) at their obtained MIC. In group III (n=10), sterile saline was used. Microbial sampling was performed before and after biomechanical preparation. Quantitative PCR was used to quantify E. faecalis in the root canal samples. For cytocompatibility assessment, L929 murine fibroblasts were exposed to various concentrations of the irrigants. Results: Irrigation with test materials resulted in significant reduction in colony forming units (CFU) in post-instrumentation samples (with the MIC values of SH and CH against E. faecalis being 0.5% and 5%, respectively). However, the reduction in the normal saline group was not significant (P=0.203). In addition, 5% CH was more effective than 0.5% SH (P=0.006) in eliminating E. faecalis. Among the different concentrations of tested irrigants, 0.5% CH and 5% SH showed the least and the most cytotoxicity, respectively (P<0.001). The cytotoxicity of 5% CH and 0.5% SH was similar (P=0.99), and lower than 2.5% SH (P<0.001). Conclusion: CH at an MIC of 5% was effective in eliminating E. faecalis in planktonic state and also its biofilm and exhibited comparable cytocompatibility to that of 0.5% SH.Keywords: Calcium Hypochlorite; Enterococcus faecalis; Polymerase Chain Reaction; Root Canal Irrigant; Sodium Hypochlorit

The Effect of Charge at the Surface of Silver Nanoparticles on Antimicrobial Activity against Gram-Positive and Gram-Negative Bacteria: A Preliminary Study

The bactericidal efficiency of various positively and negatively charged silver nanoparticles has been extensively evaluated in literature, but there is no report on efficacy of neutrally charged silver nanoparticles. The goal of this study is to evaluate the role of electrical charge at the surface of silver nanoparticles on antibacterial activity against a panel of microorganisms. Three different silver nanoparticles were synthesized by different methods, providing three different electrical surface charges (positive, neutral, and negative). The antibacterial activity of these nanoparticles was tested against gram-positive (i.e., Staphylococcus aureus, Streptococcus mutans, and Streptococcus pyogenes) and gram-negative (i.e., Escherichia coli and Proteus vulgaris) bacteria. Well diffusion and micro-dilution tests were used to evaluate the bactericidal activity of the nanoparticles. According to the obtained results, the positively-charged silver nanoparticles showed the highest bactericidal activity against all microorganisms tested. The negatively charged silver nanoparticles had the least and the neutral nanoparticles had intermediate antibacterial activity. The most resistant bacteria were Proteus vulgaris. We found that the surface charge of the silver nanoparticles was a significant factor affecting bactericidal activity on these surfaces. Although the positively charged nanoparticles showed the highest level of effectiveness against the organisms tested, the neutrally charged particles were also potent against most bacterial species