Comparative Evaluation of Canal Transportation and Centering Ratio in Curved Canals: A Study of Cone-beam Computed Tomography and Micro-computed Tomography

Introduction: This study aimed to compare the accuracy and agreement between cone-beam computed tomography (CBCT) and micro-computed tomography (micro-CT) in the assessment of canal transportation and centering ratio following root canal instrumentation with rotary files. Material and Methods: Twenty mesiobuccal canals of mandibular molars were prepared using the 2Shape sequential rotary system. CBCT and micro-CT scans were performed before and after instrumentation, and the magnitude of transportation and centering ratio were measured. The acceptable transportation was set at ≤0.15 mm. The accuracy and agreement between CBCT and micro-CT were calculated, and the intra-class correlation coefficient (ICC) and kappa coefficient were determined to assess the agreement between the two modalities. Statistical analyses were performed using repeated measures ANOVA. Results: Transportation was detected by both modalities at all distances from the apex after instrumentation. The agreement between CBCT and micro-CT in assessing canal transportation was observed in 80%, 85%, 75%, and 75% of specimens at 1-, 3-, 5-, and 7-mm from the apex, respectively. The ICC for transportation and centering ratio was much lower than 0.75, indicating poor agreement between the modalities. The kappa coefficient did not show acceptable agreement between the methods. Conclusions: CBCT and micro-CT demonstrated poor agreement in assessing canal transportation and centering ratio. Micro-CT remains the preferred modality for in vitro investigations, while CBCT should be limited to clinical settings

Comparing microleakage in root canals obturated with nanosilver coated gutta-percha to standard gutta-percha by two different methods

INTRODUCTION: Favorable apical seal of root filling materials is a crucial factor for a successful root canal treatment. The aim of this in vitro study was to compare bacterial and dye microleakage of two root canal filling materials including standard gutta-percha and nanosilver coated gutta-percha, and to evaluate the agreement between results of these two methods.MATERIALS & METHODS: Fifty-eight extracted single-rooted teeth were randomly divided into two experimental groups of 26 each, and two control groups of three each. After decoronation, root canals were instrumented by crown-down technique. Obturation was conducted using standard gutta-percha in one of experimental groups and nanosilver-coated gutta-percha in another group. AH26 sealer was used as the sealer in both experimental groups. Bacterial leakage was investigated after 60 days using Enterococcus (E.) faecalis microbial strains, and dye leakage was assessed during 72 hours using 1% methylene blue. The data were statistically analyzed by Chi-square test, Kaplan-Meier survival analysis, and Cohen’s Kappa. RESULTS: There was 84% bacterial leakage in standard gutta-percha group and 76% in nanosilver gutta-percha group. Complete dye leakage occurred in 24% and 27% of standard and nanosilver gutta-percha groups, respectively. The above difference between groups was not significant. In the samples with leakage, recorded times of leakage were not significantly different. There was no significant measure of agreement between dye and bacterial penetration along root-end fillings.CONCLUSION: There was a poor agreement between dye and bacterial leakage methods. Leakage results produced by nanosilver gutta-percha were comparable to those by standard gutta-percha. Considering the antibacterial effects of nanosilver coated gutta-percha, use of this type of gutta-percha might be more efficacious in endodontic treatments.

The Impact of Three Different Canal Lubricants on Fracture, Deformity and Metal Slivering of ProTaper Rotary Instruments

Introduction: The aim of this in vitro study was to evaluate the effect(s) of three canal lubricants i.e. sodium hypochlorite, RC-Prep as the paste form of ethylenediaminetetraacetic acid (EDTA) and aqueous EDTA, on the occurrence/incidence of fracture, deformity and metal slivering of ProTaper rotary instruments. Methods: A total of 120 mesial canals (i.e. mesiobuccal and mesiolingual) of first mandibular molars or buccal canals (i.e. mesiobuccal and distobuccal) of first maxillary molars, with curvatures of 10-20 degrees were selected and randomly divided into three groups of forty samples each. These selected canals all had approximate 19-21 mm working length and apical diameter equal to a #15 K-file. In each group, the root canals were prepared using ProTaper rotary instruments with an electric motor using one of the three aforementioned irrigants. Subsequently, samples were compared to each other at different magnifications (16×, 20×, 40× and 57×) for any fracture, deformity or metal slivering, by the Cox regression analysis. Results: The fractures rate of samples in RC-Prep group was significantly higher compared to other groups (P=0.01). No evidence of instrument deformity was detected in any groups. A statistically significant reverse relation between metal slivering and instrument fracture was observed. Conclusions: Application of aqueous EDTA and/or sodium hypochlorite as intracanal lubricants caused less fracture of ProTaper instruments compared to canal lubrication with RC-Prep

Cytoxicity of root canal antiseptics used in dental practice on L929 fibroblasts: calcium hydroxide powder vs. 2% chlorhexidine solution

Background & Objective: Chlorhexidine solution is one of the widely used mouth antiseptic liquid that prevents teeth tissue damage and also has application as a root canal antiseptic. In this study, cytotoxicity of 2% chlorhexidine solution is compared with another root canal antiseptic, calcium hydroxide powder.Materials and Methods: Cell cytotoxicity of both chemicals was assessed on cultured L929 fibroblastic cell line for 1,12, 24, 48 and 72 hours using MTT assay (Methyl tetrazolium bromide assay). Untreated L929 cells were used as a negative control group. MTT results were recorded by ELISA reader and analyzed using one-way ANOVA statistical tests.Results: Cytotoxicity of studied chemicals showed significant difference in various dilutions and times (1, 12, 24, 48 and 72 h). The highest cytotoxic effect of 2% chlorhexidine solution was observed in concentration of 0.016% for 72 h. Treatment of cells with 0.016% of 2% chlorhexidine liquid and calcium hydroxide powder for 72 hours showed 80% and 45% cytotoxicity, respectively.Conclusions: Cytotoxicity of calcium hydroxide is significantly less than 2% chlorhexidine liquid and then application of calcium hydroxide powder as root canal antiseptic is recommended

Efficacy of Video-Assisted Instruction on Knowledge and Performance of Dental Students in Access Cavity Preparation

Introduction: The conventional method of teaching endodontics has some drawbacks. Due to the small size of the oral cavity, students cannot closely observe the clinical procedure. Use of new teaching modalities such as the intraoral camera may obviate this problem. This study assessed the effect of video-assisted clinical instruction in dentistry (VACID) on dental student’s knowledge and performance in access cavity preparation during endodontic treatment. Methods and Materials: In this interventional study, twenty six undergraduate students were equally divided into two groups and received instructions on access cavity preparation via conventional demonstration (CD) or VACID using intraoral camera plus conventional demonstration. Students’ knowledge was assessed before and after the demonstration. The scores obtained by students were compared between the two groups. Data were analyzed using the Mann Whitney U test. Results: No significant difference was found between the two groups in knowledge and performance scores of students about pulp chamber removal, under-extension, over-extension, gouging, perforation or finding the main and extra canals. However, use of intraoral camera significantly reduced the number of student visits to instructors for problem solving (P=0.001). Conclusion: VACID is an effective educational method and as efficient as conventional demonstration in endodontics; as a result it can be used in combination with conventional teaching.Keywords: Conventional Education; Endodontic Treatment; Knowledge; Performance; Video-assiste

Alterations of the Danger Zone after Preparation of Curved Root Canals Using WaveOne with Reverse Rotation or Reciprocation Movements

Introduction: The aim of this study was to compare the changes that occur in the danger zone (DZ) after preparation of curved mesiobuccal (MB) canals of mandibular first molars with WaveOne instruments in two different movements [reciprocation (RCP) and counter-clockwise rotation (CCWR)] by means of cone-beam computed tomography (CBCT). Methods and Materials: MB canals of 30 mandibular molars were randomly divided into 2 groups (n=15); WaveOne/RCP and WaveOne/CCWR. Pre- and post-instrumentation CBCT images were assessed for changes in the dentin thickness in DZ (2 and 4 mm below the highest point of the root furcation) in both groups. Data was analyzed using the repeated measures ANOVA test. Results: There was no statistically significant difference between two experimental groups in terms of remaining dentin thickness at 2 and 4 mm levels below the highest point of the furcation (P>0.05). Conclusion: The efficacy of WaveOne instrument on changes of the dentin thickness in the DZ was not affected by different file movements.Keywords: Danger Zone; Reciprocating Handpiece; Reciprocation; Rotation; WaveOne

Comparing Post-Obturation of Apical Microleakage Following the Use of Different Intracanal Chelators

Objectives: Different chelators may be used during root canal treatment, offering various advantages including lubricant effect inside the canal and smear layer removal. However, chelator residues in narrow root canals can lead to apical microleakage. The aim of this in-vitro study was to compare apical microleakage following the use of three root canal chelators via fluid filtration method in root canals instrumented with ProTaper rotary system.Methods: Sixty-eight distobuccal canals of maxillary first molars were randomly divided into six groups of four experimental (n=15) and a positive and a negative control group (n=4). In groups one to three, RC-Prep, 17% EDTA and Glyde File Prep were used as chelators, respectively and sodium hypochlorite (NaOCl) was used as irrigant in all groups except for group four. In group four, root canals were instrumented without chelators and only saline was used for irrigation. Root canals in all groups were prepared using ProTaper rotary system up to F2 file and filled using cold lateral condensation technique with gutta-percha and AH26 sealer. Apical microleakage was assessed by fluid filtration method. The data were subjected to Kruskal-Wallis test.Results No significant differences were noted among the experimental groups regarding apical microleakage (P>0.05). However, preparations with RC Prep+ NaOCl and Glyde File Prep+ NaOCl yielded the highest and the lowest values of apical microleakage, respectively.Conclusion: Use of different chelators did not cause statistically significant difference in apical microleakage of root canals

The Efficacy of an Endodontic Instructional Multimedia Program for Enhancing the Knowledge and Skills of Dental Students

Background and Aim: Full-scale demonstration of treatment phases on actual patients by an instructor is currently the conventional technique for practical instruction on endodontics. In this method, most students do not get the chance to closely observe the clinical procedure due to the small size of oral cavity. This study aimed at assessing the efficacy of an instructional multimedia program in endodontics for enhancing the knowledge and skills of dental students .   Materials and Methods: In this randomized interventional trial, students taking the course of clinical endodontics were divided into two groups receiving conventional live demonstration alone or in combinationwith an instructional multimedia (DVD). Baseline knowledge of students and their level of knowledge and skills after the intervention regarding practical endodontics were assessed by a pre-test and post-test, respectively. Data were compared between the two groups using Kruskal Wallis test .   Results: No significant differenceswere noted between the two groups in terms of knowledge or practical skills of students. However, the multimedia instruction significantly reduced the number of studentinquiries to instructors for troubleshooting (P<0.001 ).   Conclusion: Due to the lack of a significant difference between the two instructional techniques, the multimedia instruction technique may be successfully used as a complement to current conventional techniques for practical instruction on endodontics

In Vitro Evaluation of the Antibacterial Activity of Three Root Canal Sealers

INTRODUCTION: Antibacterial activity is one of the desirable properties of an ideal sealer. This study aimed to compare the antimicrobial effect of three different sealers, i.e. resin (AH26), calcium hydroxide (Apexit) and zinc oxide eugenol (ZOE) based sealers. MATERIALS AND METHODS: Direct contact test with agar diffusion was used in this in vitro study. The freshly mixed sealers were AH26, Apexit and pure ZOE. They were prepared according to manufacturer’s instruction and placed in prepared wells of 30 agar plates inoculated with Streptococcus (S) mutans and Prevotella (P) melaninogenicus (15 samples for each microorganism). All plates were incubated for 7 days (196 hours) at 37˚C under anaerobic conditions, and zones of inhibition were measured after 3 days, 5 days and 7 days. The data were analyzed using Kruskal-Wallis and Friedman tests. RESULTS: In all determined intervals, the antibacterial activity of AH26 was significantly greater than other test materials (P<0.001). ZOE sealer had moderate effect on test microorganisms, whilst Apexit showed the lowest antibacterial activity on S. Mutans and no antibacterial activity on P. melaninogenicus. CONCLUSION: The ascending sequence of bacterial growth inhibition zones was as AH26>Pure ZOE>Apexit