Comparative Evaluation of Micro Tensile Bond Strength and Microleakage of Ionoseal Glass-Composite as a Fissure Sealant Material, Following Four Different Enamel Surface Pretreatments.

Statement of the Problem: Sealants are employed to prevent carious lesion initiation and to arrest caries progression by providing a physical barrier that inhibits accumulation of microorganisms and food particles in pits and fissures. The two most common materials used for sealing pits and fissures are resins and glass-ionomers. Ionoseal from VOCO company is one of the light curing glass-ionomer composite cements, whose mechanical properties should be investigated. Purpose: The aim of this study was to compare the micro tensile bond strength and micro leakage of Ionoseal with different surface pretreatments. Materials and Method: This in vitro experimental study was conducted on five groups of 95 sound human premolars. Each group consisted of five teeth for the micro tensile test and 14 teeth for the micro leakage test. The groups regarding the materials and the methods used were defined as Group 1: 35% phosphoric acid + total etch adhesive + Ionoseal, Group 2: universal adhesive+Ionoseal, Group 3: 35% phosphoric acid + Ionoseal,Group 4: Ionoseal, and Group 5 (control group): 35% phosphoric acid+Embrace fissure sealant. On the pre-pared buccal enamel of each tooth, a 5 mm block of the sealing material was created and thermo cycled. The specimens were serial sectioned to a cross section of about 1×1mm and loaded in a tensile pressure (0.5 mm/min) until failure occurred. For the micro leakage test, the sealing material was placed into the prepared occlusal fissures and teeth were thermo cycled, and then immersed in 5%methylene blue. A section was made buccolingually; the dye penetration rate was measured based on Williams and Winter criteria under a stereomi-croscope. Data was analyzed with one-way ANOVA test and Kruskal-Wallis test. Results: Mean micro tensile bond strength was significantly different between the groups (p< 0.001), and was significantly higher in Group 1. There was no significant difference between the frequency of modes of failure (p= 0.81). The rate of micro leakage was significantly different between the five groups (p< 0.001) and in Group 1 and 3; it was significantly lower than the other three groups. Conclusion: Ionoseal can be used successfully as a fissure sealant material. Etching the enamel surface with phosphoric acid is necessary and the use of a bonding agent before Ionoseal placement improves results.

Evaluation of Preventive Antibacterial Properties of a Glass-Ionomer Cement Containing Purified Powder of Salvia officinalis: An In vitro Study.

BACKGROUND: In this study, the anti-Streptococcus mutans and anti-Lactobacillus casei properties of a restorative glass-ionomer cement (GIC) modified with extract powder of Salvia officinalis as a safe and effective herbal extract at weight concentration levels of 0.5%, 0.75%, 1%, and 1.25% are investigated. METHODS: The S. officinalis extract powder is provided by doing a multistep laboratory procedure and is filtered to obtain particles smaller than 50 µ. The GIC powder is modified by adding extract powder in weight concentrations of 0.5% (Group II), 0.75% (Group III), 1% (Group IV), and 1.25% (Group V) to form experimental groups, each of 1 g. Five disk-shaped samples, 1 cm in diameter and 2 mm height, of each group (including control group [Group I]) are prepared for each bacterial category of S. mutans and L. casei. The twenty-five samples for each category are tested in vitro against strains of S. mutans and L. casei. Following Agar diffusion tests, the inhibition zone diameters are recorded. The data are tested for normality by means of Kolmogorov-Smirnov procedure. The Kruskal-Wallis and Mann-Whitney tests are used to perform a one-way ANOVA and to do pair-wise comparisons, respectively, at 5% significance level. RESULTS: The mean diameter of the inhibition zones are significantly different among the test groups and also the test groups and the control group except for the group with 0.5% in L. casei category which shows no significant difference with the control group. CONCLUSIONS: The present study revealed direct inhibitory activities of S. officinalis-containing GIC against S. mutans and L. casei in a dose-response manner.

Efficacy of Sodium Hypochlorite Activated With Laser in Intracanal Smear Layer Removal: An SEM Study.

Introduction: The purpose of the present study was to evaluate the different concentrations of sodium hypochlorite activated with laser in removing of the smear layer in the apical, middle, and coronal segments of root canal walls by scanning electron microscopy analysis. Methods: Sixty single-rooted human mandibular teeth were decoronated to a standardized length. The samples were prepared by using Race rotary system to size 40, 0.04 taper and divided into 4 equal groups (n = 15). Group 1, irrigated with EDTA 17% and 5.25% NaOCl, groups 2, 3 and 4, 1%, 2.5%, and 5% NaOCl activated with Nd:YAG laser, respectively. Teeth were split longitudinally and subjected to scanning electron microscope (SEM). Data were analyzed by Kruskal-Wallis, Mann-Whitney tests. P value of <0.05 was considered statistically significant. Results: Five percent NaOCl LAI (laser-activated irrigation) showed best smear layer removal in test groups and the difference was statistically significant (P < 0.001). Control group (EDTA 17% and 5.25% NaOCl irrigation) showed significantly better outcomes in comparative with test groups (P < 0.001). In the apical third, compared to coronal and middle third, the canal walls were often contaminated by inorganic debris and smear layer. Conclusion: All different concentrations of sodium hypochlorite activated with laser have a positive effect on removing of smear layer. Sodium hypochlorite activated with laser removed smear layer more effectively at the coronal and middle third compared to the apical third.

Comparison of the root canal debridement ability of two single file systems with a conventional multiple rotary system in long oval-shaped root canals: In vitro study.

BACKGROUND: This study sought to compare the root canal debridement ability of Neolix, Reciproc and ProTaper rotary systems in long oval-shaped root canals. MATERIAL AND METHODS: Eighty five extracted single-rooted human teeth with long oval-shaped single root canals were selected and divided into three experimental groups(n=25) and one control group (n= 10). Root canals were filled with Vitapex radiopaque contrast medium and prepared with Neolix, Reciproc or ProTaper systems. The control group only received irrigation. Digital radiographs were obtained at baseline and postoperatively and subjected to digital subtraction. The percentage of reduction in contrast medium was quantified at 0-5 mm and 5-10 mm distances from the apex. The data were analyzed using one-way ANOVA and t-test. RESULTS: The mean percentage of the contrast medium removed was not significantly different in the 0-5mm segment among the three groups (P=0.6). In the 5-10mm segment a significant difference was found in this regard among the ProTaper and Reciproc groups (P=0.02) and the highest mean percentage of contrast medium was removed by ProTaper. But, difference between ProTaper and Neolix as well as Neolix and Reciproc was not significant. In Neolix (P=0.024) and Reciproc (P=0.002) systems, the mean percentage of the contrast medium removed from the 0-5mm segment was significantly greater than that in 5-10mm segment; however, this difference was not significant in ProTaper group (P=0.069). CONCLUSIONS: Neolix single-file system may be a suitable alternative to ProTaper multiple-file system in debridement of long oval shaped canals. Key words:Root Canal Preparation, Debridement, Root Canal Therapy.

Apical Sealing Ability of Mineral Trioxide Aggregate, Intermediate Restorative Material and Calcium Enriched Mixture Cement: A Bacterial Leakage Study.

INTRODUCTION: This in vitro study compared the apical sealing ability of three common root end filling materials namely mineral trioxide aggregate (MTA), intermediate restorative material (IRM) and calcium-enriched mixture (CEM) cement using a bacterial leakage model. METHODS AND MATERIALS: The study was conducted on 83 single-rooted human teeth. Tooth crowns were cut and root canals were prepared using the step-back technique. Apical 3 mm of the roots were cut and a three-mm-deep cavity was prepared using an ultrasonic instrument. The samples were divided into three groups (n=25) according to the root-end filling material including MTA, IRM and CEM cement. The roots were inserted into cut-end microtubes. After sterilization with ethylene oxide, microtubes were placed in sterile vials containing 10 mL of Brain Heart Infusion (BHI) broth and incubated at 37°C and 0.1 mL of Enterococcus faecalis suspension compatible with 0.5 McFarland standard (1.5×108 cell/ ml), which was refreshed daily. This procedure was continued for 70 days. The data were analyzed using the chi-square, Kruskal-Wallis and log rank tests. The level of significance was set at 0.05. RESULTS: No significant difference was found in bacterial microleakage among three groups; MTA showed slightly (but not significantly) less microleakage than IRM and CEM. However, the difference in the mean time of microleakage was significant among the groups (P<0.04) and in MTA samples leakage occurred in a longer time than CEM (P<0.012). CONCLUSION: The three tested root end filling materials had equal sealing efficacy for preventing bacterial leakage.

Efficacy of a Novel Rotary System in Reduction of Intracanal Bacteria: An in Vitro Study.

INTRODUCTION: This in vitro study aimed to assess the effectiveness of a single-file rotary system (OneShape) in reduction of intracanal bacteria. METHODS AND MATERIALS: Eighty one single-rooted mandibular first premolars with single canals were used. Six samples were selected as aseptic control group. Seventy five remaining specimens were infected by Enterococcus faecalis and incubated for 72 h at 37(°)C. Then they were randomly divided into three groups (n=25). In each group, cleaning and shaping procedures were done using either two conventional rotary systems (ProTaper and iRace), or the single-file system (OneShape). Microbial samples from the intracanal environment were taken by paper points in two steps, before and after instrumentation. Then, they were diluted and plated in blood agar. In order to compare bacterial reduction and turbidity, the Kruskal-Wallis test was used followed by the Chi-Square and Mann-Whitney tests for pairwise comparison. The level of significance was set at 0.05. RESULTS: The control group didn't show any bacterial growth. The pre- and post-instrumentation samples were significantly different between three groups (P=0.02). Hence, there was no significant differences between turbidity of samples (P>0.05). CONCLUSION: OneShape system is efficient in bacterial reduction. In this regard ProTaper is the most effective system in intracanal bacterial reduction followed by iRaCe and OneShape, respectively.

The relationship between the level of salivary alpha amylase activity and pain severity in patients with symptomatic irreversible pulpitis.

OBJECTIVES: Assessment of dental pain severity is very challenging in dentistry. Previous studies have suggested that elevated salivary alpha amylase may contribute to increased physical stresses. There is a close association between salivary alpha amylase and plasma norepinephrine under stressful physical conditions. The aim of this study was to evaluate the relationship between pain severity and salivary alpha amylase levels in patients with symptomatic irreversible pulpitis. MATERIALS AND METHODS: Thirty-six patients (20 females and 16 males) with severe tooth pain due to symptomatic irreversible pulpitis were selected. The visual analogue scale (VAS) score was used to assess the pain severity in each patient. Unstimulated whole saliva was collected, and the level of alpha amylase activity was assessed by the spectrophotometric method. Statistical analysis was performed using SPSS 13. RESULTS: The level of alpha amylase was significantly increased in the saliva in association with pain severity assessed by VAS. The salivary alpha amylase was also elevated with increased age and in males. CONCLUSIONS: There was a significant correlation between the VAS pain scale and salivary alpha amylase level, which indicates this biomarker may be a good index for the objective assessment of pain intensity.

Effect of initial irrigation with sodium hypochlorite on residual antibacterial activity of tetraclean.

The purpose of this study was to assess the effect of dentin pretreatment with sodium hypochlorite (NaOCl) on the antibacterial substantivity of Tetraclean in bovine root dentin in vitro. One hundred and forty dentin tubes prepared from bovine incisor teeth were infected with Enterococcus faecalis for 14 days. The specimens were divided into five groups as follows: Tetraclean; 5.25% NaOCl/Tetraclean; 2% chlorhexidine (CHX); infected dentin tubes (positive control); and sterile dentin tubes (negative control). Round burs were used to collect dentin chips into tryptic soy broth. After culturing, the number of colony-forming units (CFU) was counted. In all experimental groups, the number of CFU was minimal in the first cultures. And the results obtained were significantly different from each other at any time period (p < 0.05). The Tetraclean group showed the most effective antibacterial action at all five experimental periods (p < 0.05). The NaOCl/Tetraclean group showed lesser antibacterial substantivity than Tetraclean at all time periods (p< 0.05). The chlorhexidine group showed the least antibacterial activity at all time periods. In conclusion, the residual antibacterial activity of Tetraclean was significantly decreased in dentin samples pretreated with NaOCl.

Effect of the combination of enamel matrix derivatives and deproteinized bovine bone materials on bone formation in rabbits' calvarial defects.

BACKGROUND: Various types of materials are used in bone regeneration procedures. The aim of this study was to investigate the use of the enamel matrix derivative (EMD), deproteinized bovine bone mineral (Bio-Oss), and a combination of Bio-Oss plus EMD in the treatment of bone defects created in the rabbits' calvaria. MATERIALS AND METHODS: Twenty New Zealand white rabbits were included in this experimental randomized single blind study. Four equal cranial bone defects (3 × 6 × 0.5 mm(3)) were created in frontal and parietal bone and randomly grafted with Bio-Oss (Group 1), EMD (Group 2), EMD + Bio-Oss (Group 3) and one of them was left unfilled to serve as a control group (Group 4). After 2, 4, 8, and 12 weeks the defects were evaluated by using histological and histomorphometric analysis. Data were analyzed by the Bonferroni test using SPSS 13 statistical software. P value <0.05 considered as statistically significant level. RESULTS: Bone formation in the EMD + Bio-Oss group after 2 weeks was diminished when statistically compared to the other groups (P < 0.05). Bone augmentation after 4 weeks from the lowest to the highest were found in groups 1, 3, 2, and 4, respectively, and these differences were statistically significant (P < 0.05). Using EMD with Bio-Oss increased bone formation in the non-critical defects in the rabbit calvaria during 8 and 12 weeks (P < 0.05). CONCLUSIONS: Boosting of EMD plus Bio-Oss seems to have synergic effect on bone regeneration in bone defects.

Cytotoxic effect of MTA and CEM cement in human gingival fibroblast cells. Scanning electronic microscope evaluation.

In this ex-vivo study, we assessed the adhesion of human gingival fibroblast (HGF) to mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cement using a scanning electronic microscope (SEM). Test biomaterials were prepared and inserted in polyethylene wells (n = 18). Glass coverslips were used for control groups. HGFs were seeded in the glass coverslips, MTA and CEM. For the positive-control group, distilled water was added to the medium; the samples were observed with SEM at one, three and seven-day intervals. Normal cell morphology was observed in the negative controls. In the positive controls, round cells with rougher surfaces were seen; these cells showed few attachments to the glass coverslip. HGFs spread and adhered similarly on MTA and CEM by forming a monolayer of flat cells; there were no statistical differences between these two experimental groups. HGF cells displayed a favorable biologic response in contact with MTA and CEM. This demonstrates non-cytotoxicity of CEM as a novel endodontic biomaterial.

Effect of Ibuprofen on IL-1ß, TNF-α and PGE2 levels in periapical exudates: a double blinded clinical trial.

BACKGROUND: Bone resorption is one of the main features of inflammatory periapical lesions and is mainly mediated by interleukin-1 beta (IL-1ß), tumor necrosis factor-alpha (TNF-α) and prostaglandin-E2 (PGE2). Recent investigations of these lesions revealed that pharmacological modulation may be possible. OBJECTIVE: The aim of this study was to evaluate the effect of Ibuprofen on IL-1ß, TNF-α and PGE2 levels in periapical exudates and compare the results with a group of placebo control. METHODS: Thirty patients with non vital teeth and radiographic lesions were divided into two groups of case and control according to their entrance to the study. Periapical exudates were taken from root canals using absorbent paper points and followed by 400 mg Ibuprofen and placebo prescribed one tablet every 6 hour for three days and in the fourth day second samples were taken, then final cleaning, shaping and obturation of the canals were completed. IL-1ß, TNF-α and PGE2 levels were determined by enzyme-linked immunosorbent assays (ELISA). Data were analyzed using paired t-test and student's t-test. RESULTS: The results showed that PGE2 levels were decreased significantly in the case group to 86.92 ± 72.42 Pg/ml following Ibuprofen treatment comparing with the pre-treatment (164.96 ± 12.255 Pg/ml) (p=0.02) and placebo group (154.2 ± 97.13 Pg/ml) (p=0.001). But there were no significant differences in IL-1ß and TNF-α level between the two groups and in each group before and after treatment. CONCLUSION: The data indicate that Ibuprofen, as a non-steroidal anti-inflammatory drug (NSAID), can be used to block PGE2 release, enhance healing of inflammatory periapical lesions and possibly to inhibit bone resorption.

Residual antibacterial activity of a new modified sodium hypochlorite-basedendodontic irrigation solution

Objective: In this in vitro study the antibacterial substantivity of a new sodium hypochlorite-based root canal irrigant(Hypoclean) in bovine root dentin was investigated.Study Design: Ninety dentin tubes prepared from bovine incisor teeth were used. After contamination for 14days with Enterococcus faecalis, the specimens were divided into five groups as follows: Hypoclean; Tetraclean;5.25% sodium hypochlorite (NaOCl); infected dentin tubes (positive control); and sterile dentin tubes (negativecontrol). Dentin chips were collected with round burs into tryptic soy broth and after culturing, the number ofcolony-forming units (CFU) was counted.Results: The number of CFU was minimum in the first cultures in all experimental groups, and the results obtainedwere significantly different from each other at any time period (P < 0.05). At all five experimental periods,the Tetraclean group showed the most effective antibacterial action (P < 0.05). Regular 5.25% NaOCl groupshowed the worst result at all periods. Hypoclean group demonstrated no bacterial growth after treatment. In eachgroup, the number of CFU increased significantly by time-lapse (P < 0.05).Conclusion: The residual antibacterial activity of Tetraclean was significantly greater than Hypoclean and 5.25%NaOCl (AU)

Residual antibacterial activity of a new modified sodium hypochlorite-based endodontic irrigation solution.

OBJECTIVE: In this in vitro study the antibacterial substantivity of a new sodium hypochlorite-based root canal irrigant (Hypoclean) in bovine root dentin was investigated. STUDY DESIGN: Ninety dentin tubes prepared from bovine incisor teeth were used. After contamination for 14 days with Enterococcus faecalis, the specimens were divided into five groups as follows: Hypoclean; Tetraclean; 5.25% sodium hypochlorite (NaOCl); infected dentin tubes (positive control); and sterile dentin tubes (negative control). Dentin chips were collected with round burs into tryptic soy broth and after culturing, the number of colony-forming units (CFU) was counted. RESULTS: The number of CFU was minimum in the first cultures in all experimental groups, and the results obtained were significantly different from each other at any time period (P < 0.05). At all five experimental periods, the Tetraclean group showed the most effective antibacterial action (P < 0.05). Regular 5.25% NaOCl group showed the worst result at all periods. Hypoclean group demonstrated no bacterial growth after treatment. In each group, the number of CFU increased significantly by time-lapse (P < 0.05). CONCLUSION: The residual antibacterial activity of Tetraclean was significantly greater than Hypoclean and 5.25% NaOCl.

Effect of pretreatment prednisolone on postendodontic pain: a double-blind parallel-randomized clinical trial.

INTRODUCTION: Effective management of endodontic pain represents a continuing challenge. This study evaluates the use of a preoperative, single oral dose of prednisolone for the prevention and control of postendodontic pain. METHODS: Forty patients were randomly assigned to 2 groups, placebo and prednisolone (30 mg). The medications were administered 30 minutes before the start of standard endodontic treatment. Postoperative pain was assessed after 6, 12, and 24 hours by using a visual analogue scale. RESULTS: The outcome showed that prednisolone resulted in a statistically significant reduction in postendodontic pain at 6, 12, and 24 hours (P < .0001). No side effects were reported for any of the medications used. CONCLUSIONS: This study suggests that a preoperative, single oral dose of prednisolone substantially reduced postendodontic pain. Further studies are needed to evaluate the applicability of these findings to other clinical conditions, single- versus multiple-visit endodontic treatment, and drug regimens.

Effect of dentin treatment time with tetraclean on its residual antibacterial activity.

The goal of this study was to evaluate the effect of dentin treatment duration (10 minutes, 24 hours, and seven days) with Tetraclean on its residual antibacterial activity in bovine root dentin. Results showed that the number of colony-forming units in all three experimental groups was zero at the first culture. Furthermore, the 10-minute group and seven-day group demonstrated the highest and the lowest number of colony-forming units, respectively.

Effect of hydrogen peroxide on the antibacterial substantivity of chlorhexidine.

The purpose of this in vitro study was to assess the effect of hydrogen peroxide on the antibacterial substantivity of chlorhexidine (CHX). Seventy-five dentine tubes prepared from human maxillary central and lateral incisor teeth were used. After contamination with Enterococcus faecalis for 14 days, the specimens were divided into five groups as follows: CHX, H(2)O(2), CHX + H(2)O(2), infected dentine tubes (positive control), and sterile dentine tubes (negative control). Dentine chips were collected with round burs into tryptic soy broth, and after culturing, the number of colony-forming units (CFU) was counted. The number of CFU was minimum in the first cultures in all experimental groups, and the results obtained were significantly different from each other at any time period (P < .05). At the first culture, the number of CFU in the CHX + H(2)O(2) group was lower than other two groups. At the other experimental periods, the CHX group showed the most effective antibacterial action (P < .05). Hydrogen peroxide group showed the worst result at all periods. In each group, the number of CFU increased significantly by time lapse (P < .05). In conclusion, H(2)O(2) had no additive effect on the residual antibacterial activity of CHX.

Comparison of removed dentin thickness with hand and rotary instruments.

INTRODUCTION: The aim of this study was to evaluate the amount of dentine removed after canal preparation using stainless steel (SS) hand instruments or rotary ProFile instruments. MATERIALS AND METHODS: Thirty-six extracted human teeth with root canal curvatures less than 30º were embedded in clear polyester resin. The roots were cut horizontally at apical 2, 4 and 7 mm. Dentin thickness was measured at each section and the sections were accurately reassembled using a muffle. Root canals were randomly prepared by SS hand instruments or rotary ProFile instruments. Root sections were again separated, and the remaining dentin thickness was measured. Mann-Whitney U and t tests were performed for analytic comparison of the results. RESULTS: The thickness of removed dentin was significantly different between the two used methods (P<0.05). Significantly greater amounts of dentin was removed mesially in all sections in hand instrumentation group (P<0.001). CONCLUSION: ProFile rotary instrumentation prepares root canals with a greater conservation of tooth structure.

A comparative study of density of obturated root canals by conventional and mechanical lateral condensation techniques.

BACKGROUND: The purpose of this study was to compare the weight of root canal filling material used in a new lateral condensation technique named mechanical lateral condensation (MLC) with that of conventional lateral condensation technique (LC). This new technique uses reciprocal handpiece. METHODS: In this experimental study, 40 human extracted straight canine teeth were used. After crown amputation, root canals were prepared with 18 mm in length. The teeth were randomly divided into four experimental groups; each group was consisting of 10 teeth. The teeth in groups IA and IB were filled by LC technique. The teeth in groups IIA and IIB were filled by MLC technique and using a finger spreader that placed in a reciprocating-action handpiece to laterally condense cold gutta-percha, creating space for accessory cones. All of the roots were weighted before and after obturation and the difference demonstrated the weight of gutta-percha mass. The data were analyzed by t-test. RESULTS: The mean weight for MLC obturations was 10.82 ± 0.025 g compared with 7.37 ± 0.035 g for that of LC technique. The difference was statistically significant (P = 0.001). CONCLUSION: This study showed that MLC technique requires more gutta-percha mass than LC technique.

Residual antibacterial activity of chlorhexidine and MTAD in human root dentin in vitro.

The purpose of this in vitro study was to compare the antimicrobial substantivity of BioPure MTAD, 2% chlorhexidine (CHX) and 2.6% sodium hypochlorite (NaOCl) in human root dentin. One hundred and ten dentin tubes prepared from human maxillary incisors were infected in vitro for 14 days with Enterococcus faecalis. The specimens were divided into five groups as follows: CHX; BioPure MTAD; NaOCl; infected dentin tubes (positive control); and sterile dentin tubes (negative control). Dentin chips were collected with round burs into Brain Heart Infusion (BHI) broth. After culturing, the number of colony-forming units (CFU) was counted. In all experimental groups, CFU was minimum after treatment (day 0), and the results obtained were significantly different from each other at any time period (P < 0.05). After treatment, the NaOCI group and BioPure MTAD group showed the lowest and highest number of CFU, respectively. In each group, the number of CFUs increased significantly by time-lapse (P < 0.05). In conclusion, the substantivity of BioPure MTAD was significantly greater than CHX and NaOCl.

A comparative study of apical microleakage using the conventional lateral condensation and mechanical lateral condensation techniques.

INTRODUCTION: This study compared apical dye penetration using lateral condensation technique (LC) and LC technique with a reciprocal handpiece (mechanical lateral condensation or MLC) as a new method. MATERIALS AND METHODS: Forty-eight human extracted straight canine teeth were used. After crown amputation, the teeth were randomly divided into four experimental groups of 10 teeth each and two negative and positive control groups of 4 teeth each. The groups were as follows: IA, 10 obturations completed by operator A using the LC technique; Group IB, 10 obturations completed by operator B using the LC technique; Group IIA, 10 obturations completed by operator A using the MLC technique; and Group IIB, 10 obturations completed by operator B using the MLC technique. All roots were placed in 2% methylene blue dye and centrifuged at 3000 rpm for 3 minutes. Following centrifugation, the roots were cut along their long axis and evaluated under a stereomicroscope to measure the depth of dye penetration. RESULTS: A t-test showed that the teeth which were filled by the MLC technique had less dye penetration in comparison with LC technique (P<0.05). CONCLUSION: This in vitro study illustrates that canals obturated with the MLC technique had superior apical seal than canals filled with the LC technique.