The effect of different concentrations and temperatures of sodium hypochlorite irrigation on pain intensity following endodontic treatment of mandibular molars with irreversible pulpitis: A randomized, double-blind clinical trial.

OBJECTIVES: This study aimed to determine the severity of pain after endodontic treatment of mandibular molars with irreversible pulpitis following the use of sodium hypochlorite (NaOCl) at different temperatures and concentrations. METHODS: In this randomized, controlled clinical trial, 72 patients with mandibular molars with irreversible pulpitis were randomly assigned to six groups. The teeth were anesthetized and the root canals were prepared. During the instrumentation, the root canals were irrigated with NaOCl solution at concentrations of 0.5% and 1% and temperatures of 2.5°C, 22°C, and 40°C, 2.5°C were achieved through cryotherapy. Assessment of pain was conducted before, immediately after, and 3, 24, 48, and 72 h after treatment. After obturation, the patients recorded their pain intensity at different time intervals on the visual analog scale (VAS) and reported the number of analgesics tablets they used. The frequency of analgesics tablets and their effect on pain sensation was recorded in the second part of the form. Repeated measures two-way analysis of variance test was used to compare the trend of pain changes over time between two intervals of time in each group. Friedman's nonparametric test was used to compare the intragroup mean score of pain over time and Kruskal-Wallis for comparing the intergroup mean score. RESULTS: Changes in VAS pain scores of all the groups were significant over time (p < .001). Pain in all the groups decreased immediately after treatment and increased 3 h after treatment. There were no significant differences in pain ratings and the number of analgesics tablets used in the groups of NaOCl with different concentrations and temperatures over time. CONCLUSIONS: Within the study's limitations, we concluded that there was no significant difference between concentrations of 0.5%, and 1% and temperatures of 2.5°C, 22°C, and 40°C in pain intensity following endodontic treatment of mandibular molars with irreversible pulpitis.

Comparative antibacterial effects of ginger and marjoram extract versus conventional irrigants on mature Enterococcus faecalis biofilms: An in vitro study.

Background: This study evaluated antibacterial effects of Ginger and Marjoram extract compared with Routine Intracanal Irrigants on Mature Enterococcus faecalis Biofilms. Material and Methods: Sixty-six extracted human teeth, were randomly assigned to four groups 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), chloroform extract of marjoram (Origanum majorana), and oil extract of ginger (Zingiber officinale), and two positive and negative control groups (n=11). Samples were contaminated with E. faecalis, except the negative control group. Then the root canals were irrigated with solutions above, after which dental debris was collected from each tooth separately, followed by culturing on plates containing BHI agar. The bacterial counts were finally determined with a colony counting machine. Results: No bacterial growth was detected in the NaOCl, CHX, and negative control groups. However, some bacterial growth was observed in the ginger and marjoram groups. All four solutions successfully eliminated E. faecalis biofilms compared to the positive control group. Significant difference in the median bacterial growth between the ginger and marjoram groups and the positive control group (P<0.001) has been shown. There was no significant difference in median bacterial growth between the ginger and marjoram groups (P=0.94). Conclusions: Chloroform extract of marjoram and oil extract of ginger were effective in eliminating 6-week-old biofilms of E. faecalis in vitro; however, their effect was not as favorable as CHX and NaOCl. These herbal extracts yielded promising results in the present study; therefore, they can be used as intracanal irrigants instead of chemical agents. Key words:Biofilm, Chlorhexidine, E. faecalis, Ginger, Marjoram, Sodium hypochlorite.

Comparison of the effect of NaOCL, curcumin, and EDTA on differentiation, proliferation, and adhesion of dental pulp stem cells.

Introduction: This study examined the effect of 1.5% NaOCl, 17% EDTA, and curcumin on the proliferation, attachment, and differentiation of dental pulp stem cells (DPSCs) placed on the dentin specimens. Methods: MTT assay was performed to evaluate the proliferation of DPSCs on the dentin specimens treated with different concentrations of NaOCl, 17% EDTA, and curcumin (0.97-250 µM). Cell-adhering ability of DPSCs was tested via the LDH assay to calculate the attached DPSCs. In addition, the western blotting assay was performed to investigate the expression levels of fibronectin as a cell-adhesion marker and analyze the expressions level of differentiation markers, including DMP-1, OCN, ALP, and DSPP, to detect the odontogenic potential of hDPCs. Results: NaOCl had lower toxicity on DPSCs at lower concentrations (P < 0.001). The cytotoxicity of irrigants increased with increased dosage. The difference between the cell-adhesion ability of NaOCl and curcumin was not significant (∼4.4 MU/mL), whereas EDTA (∼3.8 MU/mL) exhibited the lowest release of LDH and less damage to hDPSCs. Regarding fibronectin expression, the pattern differed between irrigants in inducing cell adhesion. NaOCl increased fibronectin expression more than EDTA and curcumin. All the treated groups upregulated the expression of DSPP, DMP-1, OCN, and ALP compared to the control group, in which NaOCl showed a higher effect on the overexpression of differentiation markers. Conclusion: The results showed that all the tested irrigants could be used in regenerative endodontic treatment. However, as an herbal-based and biocompatible irrigant, curcumin exhibited fewer adverse effects than NaOCl and EDTA.

Blood plasma supply chain planning to respond COVID-19 pandemic: a case study.

The COVID-19 pandemic causes a severe threat to human lives worldwide. Convalescent plasma as supportive care for COVID-19 is critical in reducing the death rate and staying in hospitals. Designing an efficient supply chain network capable of managing convalescent plasma in this situation seems necessary. Although many researchers investigated supply chains of blood products, no research was conducted on the planning of convalescent plasma in the supply chain framework with specific features of COVID-19. This gap is covered in the current work by simultaneous regular and convalescent plasma flow in a supply chain network. Besides, due to the growing importance of environmental problems, the resulting carbon emission from transportation activities is viewed to provide a green network. In other words, this study aims to plan the integrated green supply chain network of regular and convalescent plasma in the pandemic outbreak of COVID-19 for the first time. The presented mixed-integer multi-objective optimization model determines optimal network decisions while minimizing the total cost and total carbon emission. The Epsilon constraint method is used to handle the considered objectives. The model is applied to a real case study from the capital of Iran. Sensitivity analyses are carried out, and managerial insights are drawn. Based on the obtained results, product demand impacts the objective functions significantly. Moreover, the systems' total carbon emission is highly dependent on the flow of regular plasma. The results also reveal that changing transportation emission unit causes significant variation in the total emission while the total cost remains fixed.

Ability of Calcium Silicate and Epoxy Resin-based Sealers to Fill the Artificial Lateral Canals in the Presence or Absence of Smear Layer.

Background:The lateral canals are pathways for bacteria and their products to pass between the root canal and the periradicular tissue. Objectives: The present study aims to compare the filling ability of the lateral canals with three calcium silicate based sealers, including MTA Fillapex, Endoseal MTA and Sure-Seal Root, and AH26 epoxy resin sealer in the presence and absence of the smear layer. Materials and methods:Six lateral canals were prepared using an engine reamer in 80 single-rooted human teeth. The root canals were cleaned, then the teeth were randomly divided into two groups. In group A, the smearlayer was removed using 17% EDTA and 5.25% NaOCl, and in group B, the canals were irrigated with normal saline. Groups A and B were divided into four subgroups each, according to the sealer used: A1, B1 (MTA Fillapex sealer), A2, B2 (Endoseal MTA sealer), A3, B3 (Sure-Seal Root sealer), and A4, B4 (AH26 sealer). Obturation of canals was conducted by the warm vertical technique and then teeth were incubated for 72 hours. Teeth were made clear and the filling of lateral canals were evaluated under stereomicroscope. Results:In group A, the highest lateral canals filling rate was in subgroup A2 and the lowest in subgroup A1, and the difference was statistically significant. However, in both groups, the highest lateral canals filling rate was in subgroups B2 and B3 and the lowest in subgroup B1. However, the difference was not statistically significant. In addition, no significant difference was observed in the lateral canals filling rate considering their position in the root. Conclusion:Providing the removal of the smear layer, calcium silicate-based sealers, Endoseal MTA and Sure-Seal Root had a higher ability to fill the lateral canals than AH26 and MTA fillapex sealers.

Comparison of Setting Time of White Mineral Trioxide Aggregate with and without Disodium Hydrogen Phosphate at Different Liquid-to-powder Ratios.

AIM: The present study was conducted with the objective of evaluating the effect of different liquid-to-powder ratios on setting time of white mineral trioxide aggregate (WMTA) and the effect of adding disodium hydrogen phosphate (Na2HPO4) to white MTA (NAMTA). MATERIALS AND METHODS: Sixty samples were prepared in plastic annular molds with a diameter of 10 mm and a height of 2 mm in order to record setting time where white MTA was placed in 30 samples and 2.5 wt% mixture of Na2HPO4 with white MTA was placed in other 30 samples. Setting times in different ratios of liquid to powder (50, 60, and 70%) and at different times including 5, 10, 15, 20, 25, 30, 40, and 50 minutes as well as 1, 1.5, 2.5, 3, 3.5, and 4 hours were measured with Vicat. Statistical Package for the Social Sciences version 16 software was used to examine the differences between groups. The values of p < 0.05 were considered to be statistically significant in this study. RESULTS: The average setting time of samples in two WMTA and NAMTA was 182.17 ± 57.86 and 67.00 ± 14.42 respectively, and this difference was statistically significant (p < 0.001). Also, the average setting time of samples in ratio groups of 50, 60, and 70% were 146.00 ± 75.90, 85.00 ± 31.71, and 142.5 ± 64.47 respectively, and results showed that there was no significant difference between groups. CONCLUSION: Adding 2.5 wt% of Na2HPO4 mixture to white MTA reduces the setting time, which is lower than the WMTA in 50, 60, and 70% liquid-to-powder ratios. CLINICAL SIGNIFICANCE: According to the findings of this study, it can be seen that adding Na2HPO4 to white MTA is a good way to reduce setting timing in clinical dentistry, especially in one-visit treatments.

Compressive Strength of Mineral Trioxide Aggregate with and without Disodium Hydrogen Phosphate at Different Mixing Ratios.

Introduction: Mineral Trioxide Aggregate (MTA) is a substance with favorable physical-mechanical properties. Disodium hydrogen phosphate (DHP) is sometimes added to MTA to reduce its setting time. Therefore, this study was conducted to evaluate the effect of various ratios of liquid to powder of white MTA (WMTA) and addition of DHP on its compressive strength. Methods and Materials: One hundred and twenty samples were prepared with a two-piece stainless steel mold with a height of 6 mm and a diameter of 4 mm in order to evaluate the compressive strength where WMTA was used in 60 samples and DHP in white MTA composition (DHPWMTA) was used in other 60 samples. The compressive strength of WMTA and DHPWMTA was measured in various ratios of liquid to powder including 50, 60 and 70% and at 24 h and 21 days (n=10). Univariate Analysis of Variance test with SPSS 16 software were used to determine the difference between groups. The level of significance was set at 0.05. Results: The maximum and minimum compressive strength of WMTA groups were 63.25±1.96 (50% ratio and 21 days) and 37.79±1.28 (70% ratio and 24 h), respectively. The maximum and minimum compressive strength of DHPWMTA groups were 63.96±1.40 (60% ratio and 21 days) and 37.37±1.62 (70% ratio and 24 h), respectively. The effect of each of factors (type of material, powder to liquid ratio and time) alone were significant on the compressive strength (P<0.05). However, the interactive effect of three factors (type of material, powder to liquid ratio and time) were not statistically significant on compressive strength (P>0.05). Conclusion: Adding 2.5 wt% of DHP to white MTA increased samples compressive strength. Compressive strength in liquid to powder ratios of 50 and 60% compare to 70% and at 21 days compared to 24 h was high.

Root Canal Morphologies of Mesiobuccal Roots of Maxillary Molars using Cone beam Computed Tomography and Periapical Radiographic Techniques in an Iranian Population.

AIM: The aim of this study was to evaluate the accuracy of the results of cone beam computed tomography (CBCT) examinations, confirm the presence or absence of the second mesiobuccal (MB2) root canal in maxillary first and second molars, estimate the distance between the root canal orifices, observe the root types based on Vertucci classification system, and make comparisons between CBCT and periapical techniques in relation to the identification of the root canal form and the second root canal of the MB root. MATERIALS AND METHODS: The CBCT and periapical radiographic data from the Department of Maxillofacial Radiology were used to select 156 individuals (78 females and 78 males) for the evaluation of the anatomy of maxillary first and second molars. RESULTS: The prevalence rate of the second root canal in the MB root in the maxillary first molars was 55.1%, with 44.1 and 63.3% in females and males respectively. The prevalence rate in maxillary second molars was 23.7%, with 15.7 and 30.2% in females and males respectively. In addition, the longest and shortest distances between the root canal orifices were 2.4 and 0.3 mm respectively, with a mean of 1.3 mm. CONCLUSION: There was a significant difference between the results of periapical and CBCT radiographic techniques in relation to the presence or absence of the second root canal in the MB roots of maxillary first and second molars (p < 0.01), with better results being provided by the CBCT technique. CLINICAL SIGNIFICANCE: The results of CBCT images about the existence of the second root canal in the MB roots of maxillary first and second molars are more reliable, and we can use this technique in the finding of additional canals in the clinic. Keyword: Cone beam computed tomography, Dental radiography, Root canal therapy.

Bond Strength of White Mineral Trioxide Aggregate with and without Disodium Hydrogen Phosphate with Different Liquid-to-Powder Ratios.

INTRODUCTION: Mineral trioxide aggregate (MTA) can be used in the treatment of irritated vital pulp and repair of root perforations. However, the initial reaction of inflammatory cells to this material and also its setting time are not ideal. Studies have shown that disodium hydrogen phosphate (DHP), decreases the setting time of MTA, with no effect on its pH. This study was undertaken to evaluate the effect of DHP on push-out bond strength of MTA at different liquid-to-powder ratios. METHODS AND MATERIALS: A total of 120 samples were prepared from the middle third of the roots of single-rooted teeth for evaluation of push-out bond strength. The push-out bond strength was measured in both groups after 72 h at different liquid-to-powder ratios, including 0.33:1, 0.5:1 and 0.6:1. Factorial ANOVA and Tukey's HSD post-hoc tests were used to compare the differences between the independent groups. Statistical significant was set at P<0.05. RESULTS: The push-out bond strengths of pure MTA and MTA+DHP groups were 10.96±5.78 and 13.32±5.03, respectively. Tukey's HSD post-hoc test revealed significant differences between the two groups. Furthermore, there were no interactive effect between material and the liquid: powder ratio. CONCLUSION: Incorporation of DHP into MTA resulted in an increase in push-out bond strength of MTA, and an increase in liquid-to-powder ratio resulted in a decrease in push-out bond strength.

Comparison of the Penetration Depth of Conventional and Nano-Particle Calcium Hydroxide into Dentinal Tubules.

INTRODUCTION: The aim of this in vitro study was to evaluate and compare the penetration depth of conventional (CH) and nano-particle calcium hydroxide (NCH) into dentinal tubules. METHODS AND MATERIALS: Ninety human single-rooted teeth were instrumented by RaCe rotary system and after chemomechanical preparation were randomly divided in two equal groups (n=45). In the first group conventional CH and in the other NCH was used as intracanal medicament. After 2 weeks of incubation all roots were intentionally split at longitudinal axis and prepared for scanning electron microscope (SEM) observation. Three zones of each root, coronal, middle and apical were examined under SEM and the maximum penetration depth of the dressing material into dentinal tubules was recorded for each zone. Data were analyzed using the independent sample t test and the level of significance was set at 0.05. RESULTS: In all of the three zones, NCH group had greater penetration depth than CH (P<0.001). In both groups the penetration depth increased from the apical section to the coronal. CONCLUSION: The depth of penetration of nano-particle calcium hydroxide into the dentinal tubules was significantly higher than that of conventional calcium hydroxide. The lowest penetration depth was observed in apical zone in both groups.

Prevalence of Extra Roots in Permanent Mandibular First Molars in Iranian Population: A CBCT Analysis.

INTRODUCTION: Having knowledge about the anatomy of root canal system is essential for success of endodontic treatment. The present study used cone-beam computed tomography (CBCT), to evaluate the prevalence of third root in mandibular first molars in a selected Iranian population. METHODS AND MATERIALS: A total of 386 CBCT images from subjects referred to oral and maxillofacial radiology department of dental faculty of Tabriz University of Medical Sciences from 2011 to 2013 were selected and evaluated for this study and the cases with well-developed permanent mandibular first molars were included. The 3D images were reconstructed in axial cross sections and evaluated by two endodontists for the presence of the third extra lingual (radix entomolaris) or buccal (radix paramolaris) root. The chi-squared test was used to evaluate the relationship between gender and bilateral incidence of extra roots in mandibular first molars. RESULTS: The distribution of three-rooted mandibular first molars with an additional root was 3%, (3.53% in female and 2.50% in male patients). There was no significant relationship between gender and bilateral occurrence of three-rooted mandibular first molars. CONCLUSION: The occurrence of three-rooted mandibular first molars in Iranian population is not uncommon which should be taken into consideration by the dental practitioners during root canal treatment of these teeth.

Smear layer removal evaluation of different protocol of Bio Race file and XP- endo Finisher file in corporation with EDTA 17% and NaOCl.

BACKGROUND: The aim of the present study was to compare the amount of the smear layer remaining in prepared root canals with different protocols of Bio RaCe files and XP-endo Finisher file (XPF) in association with 17% EDTA and sodium hypochlorite solution. MATERIAL AND METHODS: A total of 68 extracted single-rooted teeth were randomly divided into 4 experimental groups (n=14) and two control groups (n=6). The root canals were prepared with Bio RaCe files (FKG Dentaire, Switzerland) using the crown-down technique based on manufacturer's instructions and irrigated according to the following irrigation techniques: Group 1: XPF with 2 mL of 2.5% NaOCl for 1 minute. Group 2:, XPF with 1 mL of 17% EDTA for one minute. Group 3: XPF was used for 1 minute in association with normal saline solution. Group 4: XP-endo Finisher file for 30 seconds in association with 2.5% NaOCl and 17% EDTA for 30 seconds. The negative control group: NaOCl (2.5%) was used during root canal preparation, followed by irrigation with 17% EDTA at the end of root canal preparation. The positive control group: Normal saline solution was used for irrigation during root canal preparation. In all the groups, during preparation of the root canals with Bio RaCe file, 20 mL of 2.5% NaOCl was used for root canal irrigation and at the end of the procedural steps 20 mL of normal saline solution was used as a final irrigant. The samples were analyzed under SEM at ×1000‒2000 magnification and evaluated using Torabinejad scoring system. Data were analyzed with non-parametric Kruskal-Wallis test and post hoc Mann-Whitney U test, using SPSS. Statistical significant was defined at P<0.05. RESULTS: The results of the study showed the least amount of the smear layer at coronal, middle and apical thirds of the root canals in groups 2, which was not significantly different from the negative control group (P<0.5). CONCLUSIONS: Under the limitations of the present study, use of a combination of NaOCl and EDTA in association with XPF exhibited the best efficacy for the removal of the smear layer. Key words:Smear layer, XP-endo Finisher file, EDTA, Sodium hypochlorite.

Effect of Calcium Hydroxide on the Push-out Bond Strength of Endodontic Biomaterials in Simulated Furcation Perforations.

INTRODUCTION: The aim of this in vitro study was to evaluate the effect of calcium hydroxide (CH) on push-out bond strength of white mineral trioxide aggregate (WMTA) and calcium-enriched mixture (CEM) cement in simulated furcation perforations. METHODS AND MATERIALS: Furcation perforations, measuring 1.3 mm in diameter and 2 mm in height, were created in 80 human mandibular first molars. The teeth were then divided into 4 groups (n=20). In groups 1 and 3 CH was placed in the perforation for one week, before placement of WMTA and CEM. In groups 2 and 4 perforations were repaired without placement of CH. In groups 1 and 2 the perforation sites were repaired with WMTA and CEM cement was used in groups 3 and 4. After 7 days, the push-out test was carried out using a universal testing machine. Data were analyzed with two-way ANOVA. The level of significance was set at 0.05. RESULTS: The maximum and minimum bond strength values were recorded in the WMTA/CH (13.08±1.8 MPa) and CEM cement groups (8.03±0.98 MPa), respectively. There were significant differences in resistance to dislodgement between the WMTA/CH and other groups (P<0.05). CONCLUSION: Placement of CH before placement of WMTA in furcation perforation improves the push-out bond strength of this material.

Accuracy of Cone-Beam Computed Tomography in Determining the Root Canal Morphology of Mandibular First Molars.

INTRODUCTION: The aim of the present in vitro study was to compare the accuracy of cone-beam computed tomography (CBCT) in determining root canal morphology of mandibular first molars in comparison with staining and clearing technique. METHODS AND MATERIALS: CBCT images were taken from 96 extracted human mandibular first molars and the teeth were then evaluated based on Vertucci's classification to determine the root canal morphology. Afterwards, access cavities were prepared and India ink was injected into the canals with an insulin syringe. The teeth were demineralized with 5% nitric acid. Finally, the cleared teeth were evaluated under a magnifying glass at 5× magnification to determine the root canal morphology. Data were analyzed using the SPSS software. The Fisher's exact test assessed the differences between the mesial and distal canals and the Cohen's kappa test was used to assess the level of agreement between the methods. Statistical significance was defined at 0.05. RESULTS: The Kappa coefficient for agreement between the two methods evaluating canal types was 0.346 (95% CI: 0.247-0.445), which is considered a fair level of agreement based on classification of Koch and Landis. The agreement between CBCT and Vertucci's classification was 52.6% (95% CI: 45.54-59.66%), with a significantly higher agreement rate in the mesial canals (28.1%) compared to the distal canals (77.1%) (P<0.001). CONCLUSION: Under the limitations of this study, clearing technique was more accurate than CBCT in providing accurate picture of the root canal anatomy of mandibular first molars.

Tissue Reaction and Biocompatibility of Implanted Mineral Trioxide Aggregate with Silver Nanoparticles in a Rat Model.

INTRODUCTION: Biocompatibility and antimicrobial activity of endodontic materials are of utmost importance. Considering the extensive applications of mineral trioxide aggregate (MTA) in dentistry and antimicrobial properties of silver nanoparticles, this study aimed to evaluate the subcutaneous inflammatory reaction of rat connective tissues to white MTA with and without nanosilver (NS) particles. METHODS AND MATERIALS: Polyethylene tubes (1.1×8 mm) containing experimental materials (MTA and MTA+NS and empty control tubes) were implanted in subcutaneous tissues of seventy-five male rats. Animals were divided into five groups (n=15) according to the time of evaluation: group 1; after 7 days, group 2; after 15 days, group 3; after 30 days, group 4; after 60 days and group 5; after 90 days. The inflammatory reaction was graded and data was analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Statistical significance was defined at 0.05. RESULTS: Comparison of cumulative inflammatory reaction at all intervals revealed that the mean grade of inflammatory reaction to MTA, MTA+NS and control samples were 3, 2 and 2, respectively. According to the Mann-Whitney analysis there were no significant differences between MTA+NS and MTA (P=0.42). CONCLUSION: Incorporation of 1% nanosilver to MTA does not affect the inflammatory reaction of subcutaneous tissue in rat models.

The Effect of Different Mixing Methods on Working Time, Setting Time, Dimensional Changes and Film Thickness of Mineral Trioxide Aggregate and Calcium-Enriched Mixture.

INTRODUCTION: The aim of the present study was to evaluate the effect of different mixing techniques (conventional, amalgamator and ultrasonic mixing) on the physical properties the working time (WT), setting time (ST), dimensional changes (DC) and film thickness (FT)] of calcium-enriched mixture (CEM) cement and mineral trioxide aggregate (MTA). METHODS AND MATERIALS: The mentioned physical properties were determined using the ISO 6786:2001 specification. Six samples of each material were prepared for three mixing techniques (totally 36 samples). Data were analyzed using descriptive statistics, two-way ANOVA and Post Hoc Tukey's tests. The level of significance was defined at 0.05. RESULTS: Irrespective of mixing technique, there was no significant difference between the WT and FT of the tested materials. Except for the DC of MTA and the FT of the all materials, other properties were significantly affected with mixing techniques (P<0.05). The ultrasonic technique decreased the ST of MTA and CEM cement and increased the WT of CEM cement (P<0.05). CONCLUSION: The mixing technique of the materials had no significant effect on the dimensional changes of MTA and the film thickness of both materials.

Comparing the Coronal Seal of Different Thicknesses of MTA with Gutta-Percha after Post Space Preparation.

INTRODUCTION: The aim of this study was to compare the coronal seal of different thicknesses of MTA with gutta-percha after post space preparation. MATERIALS AND METHODS: A total of 50 maxillary central incisors randomly divided into 5 experimental groups (n = 8). After preparation of the root canals with step back technique, in groups 1 and 2, post spaces were prepared and 4 or 5 mm gutta-percha remained in the apical, respectively. In groups 3, 4, and 5, there was 1-2 and 3 mm MTA in the apical, respectively. The ten teeth serve as control groups. The teeth were connected to a bacterial microleakage evaluation system. The study period was 120 days and the samples were evaluated on ten-day intervals; Meier-Kaplan technique was used for estimation of the mean time of microleakage to occur. Log-rank test was used for comparison of microleakage. RESULTS: Number of samples exhibiting microleakage in MTA was less than those of gutta-percha at all intervals. Means of days with no microleakage were maximum and minimum with 3 mm MTA and 4 mm gutta-percha, respectively. CONCLUSION: Obturation of root canals using the MTA technique provides a proper seal with the minimum thickness of MTA in teeth requiring post space preparation.

Evaluation of apical leakage in root canals obturated with three different sealers in presence or absence of smear layer.

INTRODUCTION: Microleakage can result in failure of endodontic treatment. An important characteristic of endodontic sealer is sealing ability. The aim of this experimental study was to compare the apical leakage of teeth obturated with gutta-percha and three different sealers (resin- and zinc oxide eugenol-based) with/without smear layer (SL). MATERIALS AND METHODS: In this study, 100 single-rooted teeth were used after cutting off their crowns. Cleaning and shaping was carried out with step-back technique and the samples were randomly divided into three groups (n=30) which were then divided into two subgroups (n=15) according to the presence/absence of SL. Two negative and positive control groups (n=5) were also prepared. In the various groups, the canals were obturated with gutta-percha and either of the test sealers (AH-26, Adseal or Endofill). The samples were submerged in India ink for 72 h. Then they were longitudinally sectioned and observed under a stereomicroscope at 20× magnification. Data were analyzed with descriptive statistical methods and one-way ANOVA. The significance level was set at 0.05. RESULTS: The mean penetration length of dye in AH-26, Adseal and Endofill samples were 2.53, 2.76 and 3.03 mm, respectively. The differences between three groups were not significant (P>0.05); also, the mean dye penetration in AH-26, Adseal and Endofill samples in presence or absence of the SL was not significantly different. CONCLUSION: AH-26, Adseal and Endofill were similarly effective in prevention of apical microleakage. Differences in the mean dye penetration between the groups with/without the SL were not statistically significant.

Comparison of Push-out Bond Strength of Gutta-percha to Root Canal Dentin in Single-cone and Cold Lateral Compaction Techniques with AH Plus Sealer in Mandibular Premolars.

Background and aims. The single-cone technique has gained some popularity in some European countries. The aim of the present study was to compare the push-out bond strength of gutta-percha to root canal dentin with the single-cone and cold lateral compaction canal obturation techniques. Materials and methods . The root canals of 58 human mandibular premolars were prepared using modified crown-down technique with ProTaper rotary files up to #F3as a master apical file (MAF) and divided randomly into groups A and B based on canal obturation technique. In group A (n = 29) the root canals were obturated with single-cone technique with #F3(30/.09) ProTaper gutta-percha, which was matched with MAF in relation to diameter, taper and manufacturer; in group B (n = 29) the canals were obturated with gutta-percha using cold lateral compaction technique. In both groups AH plus sealer were used. After two weeks of incubation, three 2-mm slices were prepared at a distance of 2 mm from the coronal surface and push-out test was carried out. Data were analyzed with descriptive statistics using independent samples t-test. Results. There were statistically significant differences between two groups. The mean push-out bond strength was higher in group B (lateral compaction technique) compared to group A (single-cone technique; P < 0.05). Conclusion . Use of single-cone technique for obturation of root canals resulted in a lower bond strength compared to cold lateral compaction technique.

Push-Out Bond Strength of Dorifill, Epiphany and MTA-Fillapex Sealers to Root Canal Dentin with and without Smear Layer.

INTRODUCTION: The aim of the present experimental study was to evaluate the push-out bond strength of Dorifill, Epiphany and MTA-Fillapex sealers to root canal dentin in presence and absence of smear layer (SL). METHODS AND MATERIALS: Sixty human single-rooted teeth were selected and divided into six groups (n=10). The canal irrigation protocol in groups 1, 3 and 5 consisted of 2.5% NaOCl during instrumentation and normal saline at the end of preparation plus a 5-min irrigation with 17% ethylenediaminetetraacetic acid (EDTA). In the remaining groups, normal saline was used for canal irrigation. The root canals were filled with Epiphany/Resilon (groups 1 and 2), Dorifill/gutta-percha (groups 3 and 4) and MTA-Fillapex/gutta-percha (groups 5 and 6). After two weeks of storage in 95% relative humidity at 37(º)C, 2 mm-thick dentin disks were prepared from coronal third of each root. The push-out bond strength test was carried out using a universal testing machine. Data were analyzed with the two-way ANOVA and post hoc Tukey's tests. Statistical significance was defined at 0.05. RESULTS: The highest (3.06±0.38 MPa) and lowest (1.16±0.32 MPa) push-out bond strength values were recorded in Epiphany/Resilon-NaOCl/EDTA and Dorifill/gutta-percha/normal saline groups, respectively. There were significant differences in the bond strength of sealers (P<0.05). In addition, elimination of the SL significantly increased the bond strength of all sealers (P<0.05). CONCLUSION: The Epiphany/Resilon group exhibited the highest push-out bond strength in the presence and absence of the SL. Elimination of the SL resulted in a significant increase in the bond strength of all the sealers to dentin.