Comparison of the Antibacterial Effect of AH26, Adseal and Beta RCS Root Canal Sealers against Enterococcus Faecalis, an in Vitro Study.

Objectives: Antibacterial activity against endodontic pathogens is a desirable feature for root canal sealers. The objective of this study was to compare the antibacterial effect of three resin-based endodontic sealers (AH26, Adseal, and Beta RCS) against Enterococcus faecalis in vitro. Materials and Methods: The antibacterial properties of the sealers were assessed against E. faecalis using agar diffusion test (ADT) for fresh state (N=10) and direct contact test (DCT) for freshly-mixed and set states of the materials (N=10). In ADT, the diameter of the zones of inhibition was measured after 24h of contact. In DCT, the colony-forming units of the bacteria were counted after 30 minutes and 180 minutes of exposure. The results were analyzed with two-way ANOVA and independent sample t-test. P<0.05 was considered significant. Results: Regarding DCT results, all test materials indicated an antibacterial effect, both in freshly-mixed and set states. The highest antibacterial effect was related to Adseal, whereas the lowest was observed in Beta RCS. There was a significant difference between all study groups (different sealers, setting states, and contact times; P<0.001), except for freshly-mixed AH26 and Adseal at 180 minutes (P>0.05). According to ADT, AH26 and Adseal represented the widest and the smallest inhibition zones, respectively (P<0.001). Conclusion: Within the limitations of this in vitro study, AH26, Adseal, and Beta RCS showed antibacterial effects against E. faecalis in both freshly-mixed and set states. The antibacterial effect increased over time in all of the studied sealers.

Comparative evaluation of the effect of cold ceramic and MTA-Angelus on cell viability, attachment and differentiation of dental pulp stem cells and periodontal ligament fibroblasts: an in vitro study.

BACKGROUND: Biocompatibility and induction of mineralized tissue formation are the properties expected from a material used in vital pulp therapy and repair of perforations. Cold ceramic (SJM, Iran; CC) is a newly introduced calcium silicate-based cement for above mentioned therapeutic applications. This in-vitro study aimed to compare the effect of CC and White MTA-Angelus (MTA) on cell viability, attachment, odontogenic differentiation, and calcification potential of human dental pulp stem cells (DPSCs) and periodontal ligament fibroblasts (PDLFs). METHODS: Cell viability of DPSCs and PDLFs was assessed using MTT on days 1, 3, 7, and 14 (n = 9) in contact with freshly mixed and set states of CC and MTA. Field emission scanning electron micrographs (FESEM) were taken to evaluate cell-bioceramic interaction (n = 6). Gene expression levels of osteo/odontogenic markers (Dentin sialophosphoprotein, Dentin matrix protein 1, Collagen type I alpha 1, and Alkaline phosphatase (DSPP, DMP1, COL 1A1, and ALP, respectively) (n = 8) were assessed using qrt-PCR. ALP enzymatic activity was evaluated to assess the mineralization potential. A two-way ANOVA test was applied, and p < 0.05 was considered to be statistically significant. RESULTS: The effect of freshly mixed and set MTA and CC on the survival of DPSCs and PDLFs in all study groups was statistically similar and comparable to the positive control group (p > 0.05); the only exception was for the viability of PDLFs in contact with freshly mixed cements on day 1, showing a more significant cytotoxic effect compared to the control and the set state of materials (p < 0.05). PDLFs attached well on CC and MTA. The spread and pseudopodium formation of the cells increased on both samples from day 1 to day 14. Contact of MTA and CC with DPSCs similarly increased expression of all dentinogenesis markers studied on days 7 and 14 compared to the control group (p < 0.001), except for DSPP expression on day 7 (p = 0.46 and p = 0.99 for MTA and CC, respectively). CONCLUSIONS: Within the limitation of this in-vitro study, cold ceramic and MTA-Angelus showed high biocompatibility and induced increased expression of osteo/dentinogenic markers. Therefore, cold ceramic can be a suitable material for vital pulp therapy and the repair of root perforations.

Colorimetric Comparison of Internal Bleaching with and without Removing Mineral Trioxide Aggregate (MTA) on Induced Coronal Tooth Discoloration by MTA.

Objective. This study aimed to colorimetric comparison of internal bleaching with and without removing mineral trioxide aggregate (MTA) on induced coronal tooth discoloration by MTA cement. In this experimental study, twenty human teeth were prepared. An OrthoMTA barrier was placed 1 mm below the CEJ. The teeth were restored with composite resin and were placed in the aging accelerator machine. Then, the specimens were divided into two groups (n = 10); in group A, part of the OrthoMTA was removed and the glass ionomer was placed on the OrthoMTA, and in group B, the OrthoMTA remained intact. Internal bleaching was performed 5 times in 6-day intervals using 37% carbamide peroxide gel. Color determination was performed in 5 stages: baseline, after OrthoMTA discoloration, before OrthoMTA removal, after OrthoMTA removal, and after bleaching treatment sessions. In group A, 8 specimens reached to ∆E < 3.3 after 2 times internal bleaching treatment, and in group B, 5 specimens reached to ∆E < 3.3 with almost 3 bleaching sessions (p > 0.05). Additionally, 5 specimens reached to the initial color (baseline) after bleaching treatment, 4 specimens in group A and 1 specimen in group B. After OrthoMTA removal, 2 specimens in group A reached to ∆E < 3.3. There was no significant difference between groups with or without OrthoMTA removal (p=0.06). Although, the specimens with OrthoMTA removal required fewer bleaching treatment sessions, and the mean value of ∆E was lower in this group.

Effect of ultrasonic activation on the efficacy of antimicrobial photodynamic therapy: Evaluation of penetration depth of photosensitizer and elimination of Enterococcus faecalis biofilms.

BACKGROUND: This study aimed to assess the effect of ultrasonic activation of photosensitizer on the efficacy of Antimicrobial Photodynamic Therapy (aPDT) against Enterococcus faecalis and penetration depth of photosensitizer. MATERIALS AND METHODS: In this ex vivo study, mature microbial biofilm of E. faecalis was formed in the root canals of 58 single-rooted single-canal mandibular incisors following their decoronation. The roots were longitudinally sectioned by a diamond disc and split into halves by a chisel. The E. faecalis biofilm was quantified and the penetration depth of photosensitizer was determined by the microbial viability assay and stereomicroscopic analysis in the following three study groups: (1) Ultrasonically activated 5.25% sodium hypochlorite (NaOCl) for 20 s, (2) aPDT using methylene blue (MB) plus 660 nm diode laser with 150 mW power for 1 minute, and (3) ultrasonically activated MB for 20 s followed by aPDT as in group 2. Independent sample t test and one way ANOVA were used to compare the dye penetration depth and microbial load, respectively in the apical and coronal regions among the groups. RESULTS: The penetration depth of photosensitizer in group 3 was significantly greater than that in group 2 (P < 0.05). The E. faecalis count in all three experimental groups was significantly lower than that in the control group (P < 0.05). Groups 1 and 3 were significantly superior to group 2 in terms of reduction in microbial count but the difference between groups 1 and 3 was not significant (P > 0.05). CONCLUSION: Ultrasonic activation of photosensitizer in aPDT increases the penetration depth of photosensitizer into the dentinal tubules and enhances its antibacterial activity. HIGHLIGHT: Ultrasonic activation of photosensitizer in aPDT enhances its penetration depth into dentinal tubules and increases antibacterial efficacy. There was no significant difference between antibacterial effects of aPDT + ultrasonic and ultrasonic activated NaOCl.

Comparison of Antibacterial Effect of Four Irrigation Solutions in Primary Root Canal Infections: A Clinical Study.

Introduction: Reducing the bacterial count from the root canal system is one of the main stages in root canal treatment. The aim of the present clinical study was to compare the antibacterial effect of four intracanal irrigants in primary endodontic infections using both microbiological culture and quantitative Real-time Polymerase Chain Reaction (qRT-PCR) technique. Methods and Materials: Forty patients with primarily infected single rooted premolars were selected and then randomly divided into 4 groups according to the intra canal irrigant used: 5.25% Sodium hypochlorite (NaOCl), Hypoclean (Ogna Laboratori Farmaceutici, Muggiò, Italy), 2% chlorhexidine glouconate (CHX) and CHX-Plus (Vista Dental Products, Racine, WI, USA). Samples were collected before and after chemomechanical preparation and were evaluated by bacterial culture and RT-PCR technique for Enterococcus faecalis and Fusobacterium nucleatum. Data analyzed by repeated measured ANOVA. The significance level was set at 0.05. Results: Four irrigation solutions significantly reduced the total numbers of cultivable bacteria (P<0.05). No statistically differences were found among the antibacterial effects of 5.25% NaOCl (99.93%), Hypoclean (99.94%), 2% CHX (99.77%) and CHX-Plus (99.83%) in reducing cultivable bacteria. Enterococcus faecalis and Fusobacterium nucleatum were no longer detected after preparation using four irrigants (100% reduction). Conclusions: All tested irrigants including 5.25% NaOCl, Hypoclean, 2% CHX and CHX-Plus significantly reduced the number of bacterial colonies in primary endodontic infections.

Comparison of Antibacterial Activities of ProRoot MTA, OrthoMTA, and RetroMTA Against Three Anaerobic Endodontic Bacteria.

OBJECTIVES: The aim of this study was to assess the antibacterial activities of OrthoMTA, RetroMTA, and ProRoot MTA against Fusobacterium nucleatum (Fn), Porphyromonas gingivalis (Pg), and Prevotella intermedia (Pi). MATERIALS AND METHODS: Each material was mixed on a glass slab using a spatula and was placed in columns containing the filter membrane of the modified membrane-enclosed immersion test (MEIT) system. The materials were sterilized after setting. The columns containing the sterilized test materials were placed in microcentrifuge tubes containing 500 µl of bacterial suspension. The systems were then incubated at 37°C under anaerobic conditions. After 72 hours, the bacterial growth and concentration (colony-forming unit (CFU)/ml) were assessed. The results were analyzed using one-way analysis of variance (ANOVA) and Tukey's post-hoc test in SPSS 22 software. In all analyses, the differences were considered significant at P<0.05. RESULTS: OrthoMTA had the highest antibacterial activity against Pi. The mean number of CFU/ml of Fn in the presence of ProRoot MTA and RetroMTA was significantly lower than that in positive controls. There were significant differences between the antibacterial activities of ProRoot MTA and OrthoMTA against Pg compared to positive controls. CONCLUSIONS: ProRoot MTA, OrthoMTA, and RetroMTA had similar antibacterial activities against the three evaluated anaerobic endodontic bacteria, except RetroMTA against Pg.

Efficacy of ProTaper and Mtwo Retreatment Files in Removal of Gutta-percha and GuttaFlow from Root Canals.

INTRODUCTION: The aim of this in vitro study was to compare the efficacy of ProTaper retreatment (ProTaper R) and Mtwo retreatment (Mtwo R) files in removing gutta-percha and GuttaFlow from endodontically treated straight root canals. METHODS AND MATERIALS: The root canals of 60 human mandibular single-rooted premolars were prepared and randomly divided into two groups (n=30). In groups A and B the root canals were obturated using lateral condensation of gutta-percha plus AH 26 and GuttaFlow, respectively. The canal orifices were temporarily sealed and the roots were incubated for 3 months at 37(º)C and 100% humidity. Primary cone-beam computed tomography (CBCT) images were taken after incubation period. The specimens in each group were randomly divided into two subgroups (n=15). ProTaper R files (D1, D2, and D3) were used in groups A1 and B1 while Mtwo R files (25/0.05 and 15/0.05) were used in groups A2 and B2. The time required to extirpate the root filling was also recorded. After retreatment, another CBCT scan was taken at the same position. The volume of remaining filling materials inside the canals was calculated before and after retreatment. The data was analyzed using the two-way ANOVA and independent t-test. RESULTS: The remaining filling materials in the canals treated with ProTaper were less than Mtwo. The remaining volume of GuttaFlow was less than gutta-percha regardless of the system applied. Mtwo R files removed root fillings faster than ProTaper R. CONCLUSION: ProTaper R removed filling material more efficiently compared to Mtwo R which required less time to remove root filling material.

Effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin.

OBJECTIVES: This study aimed to assess the effect of chloroform, eucalyptol and orange oil solvents on the microhardness of human root dentin. MATERIALS AND METHODS: Sixty-eight single-rooted single-canal extracted human premolar teeth were used. Tooth crowns were separated from the roots at the cementoenamel junction (CEJ). Roots were buccolingually sectioned into mesial and distal halves. Specimens were randomly divided into 5 groups, with 20 teeth in each solvent group and 4 teeth in each control group. Primary microhardness of specimens was measured using Vickers microhardness tester. Specimens were exposed to solvents for 15 minutes and were subjected to microhardness testing again. Data were recorded and analyzed using repeated measure ANOVA. RESULTS: No significant difference was found in dentin microhardness before and after exposure to solvents in any of the orange oil, eucalyptol, chloroform or saline groups (P=0.727). None of the experimental groups showed any significant difference in terms of dentin microhardness reduction (P=0.99) and had no significant difference with the negative control group. CONCLUSION: This study showed that chloroform, eucalyptol and orange oil as gutta percha solvents did not decrease the microhardness of root dentin. Thus, none of the mentioned solvents has any superiority over the others in terms of affecting dentin properties.

A Digital Stereomicroscopic Study of the Radicular Wall Thickness of Two-Canal Mandibular Incisors.

OBJECTIVES: This study aimed to assess the radicular wall thickness in mandibular incisors with two canals and find the maximum and minimum thickness to prevent root canal treatment (RCT) procedural errors. MATERIALS AND METHODS: A total of 160 extracted mandibular incisors were selected and radiographed; out of which, 55 had two canals. Three parallel transverse sections were made in each tooth at 1mm below the cementoenamel junction (CEJ), mid-root and 1 millimeter to the apex. Specimens were evaluated under a stereomicroscope and the thickness of radicular walls in each section was determined for the buccal, lingual and proximal surfaces. Data were statistically analyzed using Pearson's correlation coefficient test. RESULTS: The thickness of radicular wall decreased from the cervical towards the apex. In all three sections (cervical, mid-root and apical), the thickness of lingual wall was significantly greater than the buccal wall. Also, the thickness of buccal and lingual walls was significantly higher than that of the proximal walls. CONCLUSION: The lingual radicular wall had the highest thickness in two-canal mandibular incisors. Therefore, in these teeth, the lingual canal is a better choice for post placement.

Comparison of Apical Sealing Ability of Two Phases of Gutta-Percha: A Bacterial Leakage Model.

OBJECTIVES: The aim of this study was to compare apical sealing ability of alpha and beta phases of gutta-percha by means of bacterial leakage model. MATERIALS AND METHODS: Fifty single-rooted human premolars were selected. The root canals were prepared with Mtwo rotary instruments up to apical #35.04. Forty teeth were randomly divided into two groups (n= 20). The root canals were obturated by alpha phase (G1) and beta phase (G2) of gutta-percha and AH26 sealer, respectively, with warm vertical compaction technique. Ten teeth served as positive (n=8) and negative (n=2) control groups. Then, the specimens were sterilized with ethylene oxide gas. Bacterial suspension of Enterococcus faecalis (E. faecalis) in 0.5 McFarland concentration was prepared. All teeth were mounted in plastic vial caps containing Muller Hinton broth and then exposed to bacterial suspension of E. faecalis every three days up to 31 days. The number of days required for the contamination of the entire root canals was recorded. The data were analyzed using Mann Whitney U test. RESULTS: There were no significant differences in bacterial leakage between the G1 and G2 groups (P>0.05). Negative controls revealed no microbial leakage; whereas positive controls showed gross microbial leakage. CONCLUSION: Despite better thermal conduction and adaptability of alpha phase of guttapercha, our study revealed no significant difference in bacterial leakage between alpha and beta phases of gutta-percha in warm vertical compaction.

In vitro cytotoxicity of four calcium silicate-based endodontic cements on human monocytes, a colorimetric MTT assay.

OBJECTIVES: This study was performed to evaluate the cytotoxicity of four calcium silicate-based endodontic cements at different storage times after mixing. MATERIALS AND METHODS: Capillary tubes were filled with Biodentine (Septodont), Calcium Enriched Mixture (CEM cement, BioniqueDent), Tech Biosealer Endo (Tech Biosealer) and ProRoot MTA (Dentsply Tulsa Dental). Empty tubes and tubes containing Dycal were used as negative and positive control groups respectively. Filled capillary tubes were kept in 0.2 mL microtubes and incubated at 37℃. Each material was divided into 3 groups for testing at intervals of 24 hr, 7 day and 28 day after mixing. Human monocytes were isolated from peripheral blood mononuclear cells and cocultered with 24 hr, 7 day and 28 day samples of different materials for 24 and 48 hr. Cell viability was evaluated using an MTT assay. RESULTS: In all groups, the viability of monocytes significantly improved with increasing storage time regardless of the incubation time (p < 0.001). After 24 hr of incubation, there was no significant difference between the materials regarding monocyte viability. However, at 48 hr of incubation, ProRoot MTA and Biodentine were less cytotoxic than CEM cement and Biosealer (p < 0.01). CONCLUSIONS: Biodentine and ProRoot MTA had similar biocompatibility. Mixing ProRoot MTA with PBS in place of distilled water had no effect on its biocompatibility. Biosealer and CEM cement after 48 hr of incubation were significantly more cytotoxic to on monocyte cells compared to ProRoot MTA and Biodentine.

A comparison of viscoelastic properties of three root canal sealers.

OBJECTIVE: Handling of endodontic sealers is greatly dependent on their elasticity and flow ability. We compared the viscoelastic properties of three root canal sealers. MATERIALS AND METHODS: AH Plus (Dentsply, De Trey, Konstanz, Germany), Endofill (Dentsply Hero, Petrópolis, Rio de Janeiro, Brazil) and AH26 (Dentsply, De Trey, Konstanz, Germany) were mixed according to the manufacturers' instructions. The resulted pastes were placed on the plate of a rheometer (MCR 300, Anton-Paar, Graz, Austria). The experiments were performed at 25°C and 37°C. Viscoelastic properties of the sealers including loss modulus (G″), storage modulus (G') and complex viscosity (η*) were studied using dynamic oscillatory shear tests. The shear module versus frequency (from 0.01 to 100 S(-1)) curves were gained using frequency deformation sweep test. Three samples of each material were examined at each temperature. The mean of these three measurements were recorded. RESULTS: The storage modulus of AH plus was higher than its loss modulus at two temperatures. Endofill exhibited a crossover region in which the storage modulus crosses the loss modulus in both temperatures. At 25°C the loss modulus of AH26 was higher than the storage modulus (G″>G'). In contrast, at 37°C G' was greater than G″ (G'>G″). Both shear modules of AH Plus and Endofill decreased as the temperature raised from 25°C to 37°C. On the contrary, the loss modulus and storage modulus of AH26 increased at 37°C. CONCLUSION: In both test temperatures, AH Plus behaved like viscoelastic solids and Endofill exhibited a gel-like viscoelastic behavior. AH26 at 25°C behaved like liquids, while at 37°C it was an elastic solid-like material.

The effect of storage temperature on mechanical properties of gutta-percha and resilon.

OBJECTIVES: To compare the mechanical properties of Resilon and gutta-percha cones after storing at three different temperatures. MATERIALS AND METHODS: One-hundred standardized size 40/02 gutta-percha cones and 100 Resilon cones were randomly divided into four groups. The first group of the materials were tested immediately after receipt as the control group. The other three were stored in their packages at -12°C, 4± 1°C and 22± 2°C for three months. Then, obturating cones were loaded by a tensile force at the rate of 5mm/min. Physical integrity of gutta-percha and Resilon cones were also evaluated according to ISO6877. The data were analyzed by one-way analysis of variance, post hoc and t-test. A p-value <0.05 was considered significant. RESULTS: The elasticity modulus of gutta-percha reduced significantly after three months storage at -12°C, while storage at 4±1°C and 22± 2°C had no effect on its modulus of elasticity. In addition, the tensile strength of gutta-percha did not change after three months of storing. The modulus of elasticity of Resilon reduced significantly in all storage conditions; however, its tensile strength did not change. The storage conditions did not have a significant effect on the elongation rate of gutta-percha and Resilon. Eighty percent of gutta-percha cones lost their physical integrity after storage in 4 °±1C and 22±2°C. However, storage conditions had no impact on the physical integrity of Resilon cones. CONCLUSION: Storing gutta-percha at -12°C can benefit its properties, while keeping Resilon at both refrigerated and room conditions can preserve its mechanical properties.

Effects of enamel matrix derivative on the viability, cytokine secretion, and phagocytic activity of human monocytes.

INTRODUCTION: There is some controversy about the effect of enamel matrix derivative (EMD) on inflammation and resorption. The aim of this study was to investigate the effect of EMD on the inflammatory response of monocytes and their phagocytic activity in vitro. METHODS: Human monocytes were incubated in complete medium (CM) and exposed to 50, 100, and 200 microg/mL EMD for different time points (12, 24, 48, and 72 hours). Untreated monocytes were considered as controls. Cellular viability was evaluated through a 3-(4, 5 dimethylthiazol-2-yl) 2, 5-diphenyl-2 tetrazolium bromide assay. For cytokine measurements, the cells were treated simultaneously with 50, 100, or 200 microg/mL EMD and 10 microg/mL Escherichia coli lipopolysaccharide. Cell-free supernatants were collected after 12, 24, 48, and 72 hours of incubation. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) concentrations were measured by an enzyme-linked immunosorbent assay kit. Phagocytic activity of the cells was assayed using the PHAGOTEST kit (Glycotope Biotechnology, Heidelberg, Germany) according to the manufacturer's instructions. RESULTS: The viability of cells exposed to 50, 100, and 200 microg/mL EMD for 12, 24, 48, and 72 hours were similar to the controls. There was no significant differences in the production of TNF-alpha and IL-1beta among samples with various concentrations (50, 100, and 200 microg/mL) of EMD and control (EMD = 0) at 12, 24, 48, and 72 hours. Phagocytic activity of monocytic cells increased significantly after 72 hours compared with 12 hours. CONCLUSIONS: Based on the results of this study, EMD does not promote releasing of the two studied proinflammatory and resorbing cytokines, TNF-alpha and IL-1beta. By increasing the phagocytic activity of monocytic cells, EMD might accelerate wound healing.

Root canal morphology of the mandibular first premolars in an Iranian population using cross-sections and radiography.

INTRODUCTION: Successful endodontic treatment is dependent on a perfect knowledge of normal root canal anatomy and variations from the norm. This study was aimed to investigate the root canal anatomy of mandibular first premolars by both radiography and cross-sectional methods in an Iranian population. METHODS: Two hundred seventeen extracted human mandibular first premolars were used. Radiographs were taken in both mesiodistal and buccolingual directions for each premolar. Then, all the teeth were decoronated at the cementoenamel junction and resected perpendicular to their long axes into three equal sections and stained with fuscin. Digital photographs of the cross-sectional root surfaces were taken and surveyed at 40x magnification. The root canal configuration types were determined separately by radiographs and cross-sectional images for each premolar. RESULTS: Out of 217 teeth examined, 192 (88.47%) had a single root canal. The remaining 25 teeth (11.53%) showed two canals in at least one cross-section of their roots with five root canal configurations. In the mesiodistal (MD) radiographs, only 5.99% of premolars showed two canals with three root canal configurations. CONCLUSIONS: One-hundred ninety two out of 217 premolars showed one canal in both cross-section and MD radiography. Only 7 premolars were diagnosed as having more than one canal with the same canal configuration in both cross-sections and MD radiography methods.

Influence of Bovine Serum Albumin on the Antibacterial Activity of Endodontic Irrigants against Enterococcus Faecalis.

INTRODUCTION: It has been demonstrated that organic content of the root canals can influence the antimicrobial capability of chemical irrigants. The aim of this study was to evaluate the effect of bovine serum albumin (BSA), as an organic material, on the antimicrobial activity of several intracanal irrigants. MATERIALS AND METHODS: Bactericidal activity of Ethylenediaminetetraacetic acid (EDTA) 17%, citric acid 10%, Sodium hypochlorite (NaOCl) 5.25%, Chlorhexidine 0.2% (CHX), Smear Clear and Cetrimide 0.5% were tested by means of dilution-neutralization method. Contact times were 10 and 30 seconds, 5, 10, 30, 60 minutes and 24 hours. First 950 λ of the medicament was mixed with 50 λ of the bacterial suspension in an Eppendorf test tube. The suspensions were thoroughly mixed. Sterile water served as negative controls. After each contact time, 100 λ of samples was transferred to the Eppendorf test tubes which contained neutralizers. After 5 minutes, 50 λ of serial dilutions were cultured on brain heart infusion agar and incubated in aerobic conditions. Then colonies were counted and reported as cfu/mL. In half of the samples, medicaments were suspended in BSA 0.5% 30 minutes before examination to assess its possible inhibitory effect on the antibacterial activity. RESULTS: NaOCl 5.25%, Cetrimide 0.5% and Smear Clear showed bactericidal activity within seconds after the incubation. BSA had no inhibitory effect on bactericidal activity of these three medicaments. CHX took 5 and10 minutes to kill all bacterial cells in the absence and presence of BSA, respectively. Citric acid and EDTA showed the least antibacterial activity. CONCLUSION: In this study, NaOCl 5.25%, Cetrimide 0.5% and Smear Clear were significantly more effective against E. faecalis than EDTA 17% and citric acid 10% in the presence and absence of BSA. Also, in the presence of BSA, bactericidal activity of CHX 0.2% against E. faecalis was significantly more than EDTA after 10 and 30 minutes of contact time. EDTA and citric acid showed the least bactericidal activity. [Iranian Endodontic Journal 2009;4(4):139-43].

Comparison of the efficacy of three chelating agents in smear layer removal.

The purpose of this study was to compare the efficacy of SmearClear (Sybron Endo, Orange, CA), 17% EDTA, and 10% citric acid in smear layer removal. Forty-eight extracted single-rooted human teeth were randomly divided into 4 groups (n = 12) and instrumented using Mtwo nickel-titanium rotary instruments. Each canal was subsequently irrigated with one of the following solutions: 5.25% NaOCl (control), SmearClear, 17% EDTA, or 10% citric acid. After that, all the specimens were subjected to irrigation with 5.25% NaOCl. The teeth were then processed for scanning electron microscopy (SEM), and the removal of the smear layer was examined in the coronal, middle, and apical thirds. The results showed that there were no significant differences in the efficacy of three chelating agents at all levels of the root canals. The comparison of three one thirds in each group showed no significant difference in the SmearClear and EDTA groups. However, the efficacy of citric acid was significantly less in the apical third compared with the coronal and middle thirds of the canals. In conclusion, the protocol used in this study was not efficient to completely remove the smear layer especially in the apical third of the canal.