Moistened Cotton Pellet Research Articles

The Effect of Different Sealer Removal Protocols on Micro-Tensile Bond Strength of Single Bond Plus to Dentin Exposed with Different Chemical Root Canal Irrigants: An Ex Vivo Study

Background: Chemical substances used to prepare root canals and their residuals can alter dentin surface composition, affecting restorative systems bonding to dentin. Objectives: This ex vivo study evaluated the effects of different sealer removal methods on the micro-tensile bond strength of dentin surfaces exposed using endodontic irrigants. Methods: A total of 45 extracted healthy mandibular molars were sliced from the occlusal surface to expose their dentin surface and were randomly divided into three main groups (n = 15) based on the irrigants as G1: Distilled water (control), G2: Sodium hypochlorite (NaOCL) 5.25%, and G3: Chlorhexidine (CHX) 2%. AH Plus endodontic sealer, was applied to all exposed dentin surfaces. Each group was divided into four subgroups (SG) according to the sealer removal methods: SG1: No root canal sealer (control), SG2: Moist cotton pellet, SG3: Ethanol 95% saturated cotton pellet, SG4: Round diamond bur. The teeth were restored using single bond plus and Z250 composite and sectioned to prepare sticks for micro-tensile bond testing. Additionally, failure patterns were investigated. Comparison between experimental groups was performed using Kruskal-Wallis H and Dunn's post-hoc tests. The accepted significance level for all tests was P < 0.05. Results: A significant decrease was observed in the micro-tensile bond strength of the control group cleaned with 95% Ethanol saturated cotton pellets. In addition, the highest micro-tensile bond strength was observed in dentin cleaned through a diamond round bur and in the group irrigated with CHX. The failure modes were mainly adhesive. Conclusions: Within this study's limitations, the dentin bond strength is affected by the irrigation protocol and sealer removal method.

A scanning electron microscopic study evaluating the sealing ability of MTA, BiodentineTM, and new light-cure MTA used for furcal perforation repair.

To evaluate and compare the sealing ability of Mineral trioxide aggregate (MTA), BiodentineTM and light cure MTA used for the repair of furcal perforations using scanning electron microscope (SEM). The study sample comprised 45 extracted mandibular molars. The teeth were embedded in modeling wax. Standard access cavities were prepared in each tooth using a round bur and non-end cutting bur with a high-speed handpiece with water spray. Furcal perforations were made on the centre of the pulpal floor of each tooth using a 0.5mm round bur. The teeth were then randomly divided into 3 experimental groups of 15 specimens each based on the materials used to seal the perforation; Group A: MTA; Group B: BiodentineTM; Group C: Light cure MTA. All the sealed perforations were compacted with a moist cotton pellet, and the samples were stored in a closed container for 24 hours to allow the repair materials to set completely. After 24 hours the samples were sectioned longitudinally and the extent of marginal adaptation was measured using scanning electron microscopy. The sealing ability was evaluated by measuring the gap (in microns) between the pulpal floor and the material used for the furcal repair. The overall results showed that the marginal adaptation of light-cure MTA was better than both MTA as well as Biodentine. The mean space between the pulpal floor and the repair material was least for group C (2.29). Tuckey's post hoc test showed that a significant difference (p<0.05) existed between group C and group A & B. Light-cure MTA exbibits good sealing ability to dentin when compared to conventionally used Biodentine and Mineral Trioxide Aggregate. Key words:Calcium silicates, MTA, Biodentinte, New light-cure MTA, Perforation repair.

Retrievability of Odontopaste and Metapex With 17% Ethylenediaminetetraacetic Acid and 10% Maleic Acid From Root Canals: An Invitro Study.

AimTo evaluate the efficacy of 10% maleic acid in comparison with 17% ethylenediaminetetraacetic acid (EDTA) in the removal of intracanal medicaments from the root canal system.Materials and methodsForty-eight extracted single-rooted mandibular premolars were decoronated to standardize the length of 14 mm. Chemomechanical preparation was done using the crown-down technique with Protaper files (Dentsply‑Maillefer, Ballaigues, Switzerland) till F4, followed by irrigation with 2 ml of 5.25% sodium hypochlorite (NaOCl) after each instrument, and 5 ml of 17% EDTA was used as the final irrigating agent.Metapex (Meta Dental Corp. Ltd., Elmhurst, NY, USA) and Odontopaste (Australian Dental Manufacturing, Kenmore Hills, Qld, Australia) were the two intracanal medicaments that were used in this study.Total samples were divided into two groups based on the intracanal medicament that was placed in the canal. In group 1, Metapex was injected into the root canal until the material extruded through the apex. In group 2, Odontopaste was placed into the canal until the material extruded through the root apex. Cleaning off the excess medicament was done with a moist cotton pellet. After temporary sealing with a cotton pellet and Cavit, all the samples were stored at 37 ºC and 100% relative humidity for a period of seven days. The teeth in each group were further randomly divided into three subgroups on the basis of the irrigant used for retrieval of medicament. In groups 1A and 2A, 1ml of 17% EDTA was used; in groups 1B and 2B, 1ml of 10% maleic acid was used; in groups 1C and 2C, 1ml of 0.9% saline was used. Sonic agitation for 1 minute, followed by a final rinse of 1 ml distilled water, was used in all the groups.After the intracanal medicament was removed from the canal, the roots were longitudinally sectioned using a diamond disk (Bego, Berman, Germany). The residual medicament on each section was evaluated under a stereomicroscope (×30; Medilux, MDL-DS4-BI, Biosystems, Curitiba, PR, Brazil). The data were analyzed using SPSS version 23.0 software (IBM Corp., Armonk, NY). Kruskal-Wallis ANOVA and Mann-Whitney U test (post hoc) were applied for intergroup comparisons. A Wilcoxon signed-rank test was applied for intragroup comparisons.ResultsBoth the chelators, 17% EDTA and 10% maleic acid, removed the Odontopaste significantly better than Metapex. However, 17% EDTA was more effective in the removal of Odontopaste. 10% Maleic acid showed better results in the removal of Metapex than 17% EDTA.ConclusionNone of the chelating agents was able to totally retrieve the intracanal medicaments. When compared to Metapex, Odontopaste showed significantly better retrievability from the root canal with both 17% EDTA and 10% Maleic acid, whereas the retrievability of Metapex was significantly better with 10% Maleic acid in comparison to 17% EDTA.

Pulpal dressing condensation methods in pulpotomy for primary molars: An in-vitro comparative study

PurposeTo compare three condensation techniques of zinc oxide eugenol (ZOE) as a pulpal dressing material during pulpotomy in extracted primary molars. Material and MethodsSixty primary first and second molars were embedded in individual wax casts and divided into three groups consisting of 20 teeth each. In group I, the ZOE base was condensed by an amalgam condenser, while a moist cotton pellet was used in group II. A combination of an amalgam condenser and a wet cotton pellet tested the condensation mentod in group III. The condensation quality of the three techniques was evaluated through two digital periapical radiographs taken in a lateral and anterior-posterior direction. ResultsNon-parametric Kruskal-Wallis test showed that there was no significant difference between the technique and quality of ZOE compaction. However, a significant difference was observed on condensation assessment for combined three groups on lateral radiographs vs the appearance on antero-posterior radiographs with the p-value set at < 0.05. ConclusionVoids appeared with all three techniques. A combination of an amalgam condenser and the wet cotton wool pellet was the least effective method of condensation. Lateral radiographs revealed much fewer spaces between the ZOE and pulpal floor in comparison to antero-posterior images.

An In vitro Study to Assess the Effectiveness of the Shear Bond Strength of Mineral Trioxide Aggregate with Different Adhesive Systems.

Purpose of the Study:Mineral trioxide aggregate (MTA) is a biocompatible material and has excellent sealing ability. It is proved and claimed that it provides double seal due to its physical sealing ability as well as ability to induce cementogenesis that provides biological seal.Aim and Objectives:The aim of the study was to assess the shear bond strength of MTA with three different types of adhesive systems: (1) self-adhering flowable composite, (2) etch and rinse (ER) adhesive system, and (3) self-etch (SE) adhesive system.Materials and Methods:Ninety MTA specimens were prepared using cylindrical acrylic blocks, having a central cavity with 2 mm depth and 4 mm diameter. MTA was mixed and placed in the prepared cavity and was covered with moist cotton pellet and temporary filling material (Cavit). They were further divided into three groups which were further divided into two subgroups. After the bonding agents was applied, the composite resin was placed over the MTA surface. The specimens were then tested for shear bond strength; statically analysis was done.Result:After 24 h, the mean value of ER group was found to be significantly higher than SE and the self-adhering composite groups. Among the 45 min groups, there was no significant difference observed.Conclusion:In single visit, after 45 min, self-adhering flowable can be used successfully as a final restorative material in place of conventional flowable composite without using any alternative adhesive system over MTA.

Mineral trioxide aggregate pulpotomy for permanent molars with clinical signs indicative of irreversible pulpitis: a preliminary study.

To prospectively investigate the clinical and radiographic success rates of pulpotomy in permanent molars with clinical signs and symptoms suggestive of irreversible pulpitis using mineral trioxide aggregate (MTA) as a pulp dressing agent. Sixteen patients with 23 restorable permanent molars exhibiting signs and symptoms indicative of irreversible pulpitis were enrolled. A standardized operative procedure was followed for all participants. All teeth were isolated with a dental dam and caries was removed, and then, pulpotomy performed with a sterile round and/or flame shape diamond burs. Haemostasis was achieved with 5% sodium hypochlorite (NaOCl). A mixture of MTA was placed against the wound, and a moistened cotton pellet was placed over the MTA. Teeth were temporized with a glass-ionomer restoration. Three to ten days later, the interim restoration was removed and setting of MTA was evaluated. Teeth were restored with stainless steel crowns. Follow-up evaluations were scheduled at 3, 6, 12months and annually thereafter. Descriptive statistics were used to assess outcomes. The age of patients at time of pulpotomy ranged between 7.6 and 13.6years (mean=10.7±1.7yrs). The majority of teeth (91%) had clinical signs and symptoms consistent with a diagnosis of symptomatic irreversible pulpitis and symptomatic apical periodontitis (78%). The follow-up examination period ranged from 18.9 to 73.6months. Clinically and radiographically, all pulpotomies were considered successful at the end of the follow-up period. Radiographically, a hard tissue barrier was noticed in 13 (57%) teeth. In children, MTA was associated with high clinical and radiographic success as a pulpotomy agent in permanent teeth with clinical signs and symptoms suggestive of irreversible pulpitis.

Assessment of Mineral Trioxide Aggregate pulpotomy in mature permanent teeth with carious exposures.

To assess the outcome of mineral trioxide aggregate (MTA) complete pulpotomy in permanent teeth with carious exposures. Fifty-two permanent molar teeth with fully developed roots and vital pulps in 43 patients aged 11-51years were included. Preoperative pulpal and periapical diagnosis was established. After informed consent, each tooth was anaesthetized, isolated with dental dam and disinfected with 5% NaOCl before caries excavation; subsequently, a full pulpotomy was performed. Haemostasis was achieved, and Grey MTA (Angelus, Londrina, Brazil) was placed as the pulpotomy agent; a moist cotton pellet was placed, and the tooth was temporized with the intermediate restorative material (IRM). Permanent restorations were placed 1week later if the tooth was asymptomatic, and a postoperative periapical radiograph was taken. Clinical and radiographic evaluation was completed at 3months, 6months, 1year and 3years postoperatively. Clinical signs and symptoms suggestive of irreversible pulpitis were established in 44/52 teeth, and periapical rarefaction was present in 14 teeth. Immediate failure occurred in one tooth. The recall rate ranged from 92% at 3months to 80.3% at 3years, with an overall 100% clinical and 97.5% radiographic success during the first year, and 92.7% success at 3years. All cases with periapical rarefaction were associated with improvement in the periapical index (PAI) score. Two cases had new periapical rarefaction associated with dislodgment of the permanent restoration. A hard tissue barrier was detected radiographically in 5 cases and canal narrowing in 7 cases. MTA full pulpotomy was a successful treatment option for cariously exposed pulps in mature permanent molar teeth.

Surface microhardness of different thicknesses of a premixed bioceramic material with or without the application of a moist cotton pellet.

Background:This study was conducted to assess the effect of thickness and hydration condition on the surface microhardness of Endosequence Root Repair Material putty (ERRM; Brasseler USA, Savannah, GA), a premixed bioceramic material.Materials and Methods:Polymethyl methacrylate cylindrical molds with an internal diameter of 4 mm and three heights of 2, 4, and 6 mm were fabricated. In Group 1 (dry condition), the molds with heights of 2, 4, and 6 mm (10 molds of each) were filled with ERRM. In Groups 2 and 3 (wet condition), a distilled water- or phosphate-buffered saline (PBS)-moistened cotton pellet was placed directly on the upper surface of ERRM, respectively. The lower surface of ERRM was in contact with floral foams soaked with human blood. After 4 days, Vickers microhardness of the upper surface of ERRM was tested. The data were analyzed using two-way analysis of variance. Significance level was set at P < 0.05.Results:No significant difference was found between the microhardness of three thicknesses of ERRM (2, 4, and 6 mm) with or without placing a distilled water- or PBS-moistened cotton pellet over the material (P > 0.05).Conclusion:Based on the results of this study, it could be concluded that placing a moistened cotton pellet on ERRM putty up to 6 mm thick might be unnecessary to improve its surface microhardness and hydration characteristics.

The shear bond strength of MTA with three different types of adhesive systems: An in vitro study.

Aim:To evaluate the shear bond strength of MTA with three different types of adhesive systems- self-adhering flowable composite, etch and rinse adhesive system and self etch adhesive system.Methodology:MTA specimens (n = 60) were prepared using cylindrical acrylic blocks, having a central cavity with 4 mm diameter and 2 mm depth. MTA was mixed and placed in the prepared cavity, and was covered with a moist cotton pellet and temporary filling material. The specimens were divided into 3 groups which were further divided into 2 sub-groups (45 Minutes and 24 hours). After the application of bonding agents composite resin was placed over the MTA surface. The specimens were tested for shear bond strength and readings were statically analyzed.Result:After 24 hrs the mean value of etch and rinse group was significantly higher than self etch and the self adhering composite groups. Among the 45 minutes groups there were no significant difference.Conclusion:In single visit after 45 minutes self adhering flowable can be used successfully as a final restorative material in place of conventional flowable composite without using any alternative adhesive system over MTA.

Clinical and Radiographic Evaluation of Success of Two commercially Available Pulpotomy Agents in Primary Teeth: An in vivo Study

The aim of this study is to evaluate and compare Biodentine and mineral trioxide aggregate (MTA) as pulpotomy agents by clinical and radiological assessments in primary teeth. In this study, 90 decayed primary molars indicated for pulpotomy were chosen and are divided into two groups. Soft enamel and dentinal caries were removed using spoon excavator. Access opening was done using highspeed cool water handpiece. Normal saline was used to irrigate pulp chamber, later saline moistened cotton pellet was used to obtain hemostasis in both groups. Restorations were placed in respective groups and immediate postoperative radiographs were taken. Follow-ups were done at every 3 months intervals, i.e., 3, 6, 9, and 12 months respectively. Statistical evaluation was carried out by using paired t-test which showed no significant difference between the two groups (p ≥ 0.05) with high success rate of 95.5%. Pulpotomy with MTA and Biodentine is a reliable biological method for pulp treatment of primary teeth. Mineral trioxide aggregate and Biodentine could be considered as a reliable biological method for pulp-otomy of primary teeth.

Influence of phosphate buffered saline on the bond strength of endodontic cement to dentin

Aim: To analyze the influence of exposure and time of exposure to phosphate buffered saline (PBS) on the push-out bond strength (BS) of Biodentine to dentine. Methods: Eighty 2-mm-thick dentin discs were obtained from transversal sections of human teeth roots. The space of the canal was enlarged using #2–#5 Gates-Glidden burs to obtain 1.3-mm-diameter standardized cavities. The discs were immersed in 17% EDTA followed by 1% NaOCl and dried. The spaces of the canals were filled with Biodentine and the samples were divided into 2 groups (n=40) according to the storage: G1: exposure to moistened cotton pellet; G2: exposure to PBS. After 30 min, 1, 3 and 28 days, 10 samples of each group were subjected to the push-out test. Data were analyzed using ANOVA and Tukey test (p < 0.05). Results: The specimens exposed to PBS had lower BS (p < 0.05), except for the 1-day period (p = 0.6017). In specimens of Group 1 the BS increased up to 3 days (p < 0.05). In specimens in Group 2, the BS increased from 30 min to 1 day (p < 0.0001) and remained stable up to 3 days (p = 0.9876). At 28 days, a significant decrease was observed in the BS values of both groups (p < 0.05). Conclusions: The exposure of Biodentine to PBS led to lower BS values. In general, the BS increased gradually up to 3 days and reduced at 28 days.

A laboratory assessment of bacterial leakage in MTA apical plugs exposed to phosphate-buffered saline.

This study evaluated the influence of the exposure of mineral trioxide aggregate (MTA) - with and without calcium chloride (CaCl2) -to phosphate-buffered saline (PBS) on apical microleakage. Sixty root segments were divided into 4 experimental groups (n=15). Apical cavities were filled with MTA with or without CaCl2, and the root canals dressed with a moistened cotton pellet or PBS: 1) MTA/cotton pellet; 2) MTA/PBS; 3) MTA+ 10%CaCl2/cotton pellet; 4) MTA+10%CaCl2/PBS. After 2 months, E. faecalis penetration was analyzed along the apical plugs. Samples were observed weekly for 70 days, and leakage was detected by turbidity of the medium in contact with the root segment. Teeth in the control groups (n=2) were either made completely impermeable or kept without an apical plug. The Kaplan-Meier method was used to analyze survival and the Logrank test was used to compare the survival curves (p<0.05). All specimens in the positive control group showed evidence of leakage within 24h, while none in the negative control group showed leakage up to 70 days. There was no statistically significant difference among the experimental groups (p=0.102). The use of PBS as intracanal dressing may improve MTA sealing ability, but cannot prevent bacterial leakage. The addition of CaCl2 to the MTA did not improve MTA sealing ability.

Surface microhardness of three thicknesses of mineral trioxide aggregate in different setting conditions.

ObjectivesThis study aimed to compare the surface microhardness of mineral trioxide aggregate (MTA) samples having different thicknesses and exposed to human blood from one side and with or without a moist cotton pellet on the other side.Materials and MethodsNinety cylindrical molds with three heights of 2, 4, and 6 mm were fabricated. In group 1 (dry condition), molds with heights of 2, 4, and 6 mm (10 molds of each) were filled with ProRoot MTA (Dentsply Tulsa Dental), and the upper surface of the material was not exposed to any additional moisture. In groups 2 and 3, a distilled water- or phosphate-buffered saline (PBS)-moistened cotton pellet was placed on the upper side of MTA, respectively. The lower side of the molds in all the groups was in contact with human blood-wetted foams. After 4 day, the Vickers microhardness of the upper surface of MTA was measured.ResultsIn the dry condition, the 4 and 6 mm-thick MTA samples showed significantly lower microhardness than the 2 mm-thick samples (p = 0.003 and p = 0.001, respectively). However, when a distilled water- or PBS-moistened cotton pellet was placed over the MTA, no significant difference was found between the surface microhardness of samples having the abovementioned three thicknesses of the material (p = 0.210 and p = 0.112, respectively).ConclusionsIt could be concluded that a moist cotton pellet must be placed over the 4 to 6 mm-thick MTA for better hydration of the material. However, this might not be necessary when 2 mm-thick MTA is used.

Influence of the exposure of MTA with and without calcium chloride to phosphate‐buffered saline on the push‐out bond strength to dentine

To analyse the influence of exposure of mineral trioxide aggregate (MTA) with and without calcium chloride (CaCl2 ) to phosphate-buffered saline (PBS) on the push-out bond strength, over different experimental periods. One hundred and twenty dentine discs with standardized cavities were filled with MTA with and without 10% CaCl2 . The specimens were randomly divided as follows (n = 30): (G1) MTA in contact with a moistened cotton pellet, (G2) MTA immersed in PBS, (G3) MTA + CaCl2 in contact with a moistened cotton pellet and (G4) MTA + CaCl2 immersed in PBS. The samples were stored for 3, 28 and 60 days. The bond strengths were measured with the Instron Testing machine. Data were analysed using the three-way anova and Tukey test (P < 0.05). In general, the samples of MTA with and without CaCl2 , exposed to PBS, had higher bond strength values in all study periods (P < 0.05). Analysis of the influence of addition of CaCl2 to MTA (G1 × G3) evidenced significant differences in bond strength in the different periods (P < 0.05). The exposure of MTA to PBS positively influenced the push-out bond strength, whereas the addition of CaCl2 had a negative influence.

The sealing ability of MTA apical plugs exposed to a phosphate-buffered saline

The aim of this study was to evaluate the influence of exposure of the mineral trioxide aggregate (MTA) - with and without calcium chloride (CaCl2) - to phosphate-buffered saline (PBS) on the apical microleakage using a glucose leakage system. Sixty root segments were randomly divided into 4 experimental groups (n=15). After resecting the apical segments and enlarging the canals with Gates-Glidden drills, the apical cavities were filled with MTA with or without CaCl2 and the root canals were dressed with a moistened cotton pellet or PBS, as follows: 1) MTA/cotton pellet; 2) MTA/PBS; 3) MTA+10%CaCl2/cotton pellet; 4) MTA+10%CaCl2/PBS. All root segments were introduced in floral foams moistened with PBS. After 2 months, all root segments were prepared to evaluate the glucose leakage along the apical plugs. The amount of glucose leakage was measured following an enzymatic reaction and quantified by a spectrophotometer. Four roots were used as controls. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests (p<0.05). There were no differences between groups 1 and 2 (p>0.05), and 3 and 4 (p>0.05). The addition of CaCl2 to the MTA significantly decreased its sealing ability (p<0.05). The interaction with PBS did not improve the MTA sealing ability. The addition of CaCl2 to the MTA negatively influenced the apical seal.

The sealing ability of MTA apical plugs exposed to a phosphate-buffered saline

ObjectiveThe aim of this study was to evaluate the influence of exposure of the mineral trioxide aggregate (MTA) - with and without calcium chloride (CaCl2) - to phosphate-buffered saline (PBS) on the apical microleakage using a glucose leakage system. Material and MethodsSixty root segments were randomly divided into 4 experimental groups (n=15). After resecting the apical segments and enlarging the canals with Gates-Glidden drills, the apical cavities were filled with MTA with or without CaCl2 and the root canals were dressed with a moistened cotton pellet or PBS, as follows: 1) MTA/cotton pellet; 2) MTA/PBS; 3) MTA+10%CaCl2/cotton pellet; 4) MTA+10%CaCl2/PBS. All root segments were introduced in floral foams moistened with PBS. After 2 months, all root segments were prepared to evaluate the glucose leakage along the apical plugs. The amount of glucose leakage was measured following an enzymatic reaction and quantified by a spectrophotometer. Four roots were used as controls. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests (p<0.05). ResultsThere were no differences between groups 1 and 2 (p>0.05), and 3 and 4 (p>0.05). The addition of CaCl2 to the MTA significantly decreased its sealing ability (p<0.05). ConclusionThe interaction with PBS did not improve the MTA sealing ability. The addition of CaCl2 to the MTA negatively influenced the apical seal.

In Vitro Assessment of Mineral Trioxide Aggregate Setting in the Presence of Interstitial Fluid Alone

IntroductionThe aim of this study was to determine the ability of white mineral trioxide aggregate (MTA) Angelus (Solucoes Odontologicas, Londrina, Brazil) to set in 24 hours within the root canal in the presence of an intrinsic moisture source (interstitial fluid) alone without the need for moist cotton pellet placement. MethodsExtracted teeth were used to simulate the open apex situation. MTA was placed to a depth of 4 mm and allowed to set for 24 hours in the following test groups: a current protocol group with a moist cotton pellet, a test group with no moist cotton pellet placement, and positive and negative control groups with varnished roots. The teeth were embedded in florist sponges immersed in fetal bovine serum at 13.3-kPa pressure. The MTA set was tested using the Vickers hardness test, and the data were analyzed using analysis of variance. ResultsThe greatest mean surface hardness values were observed in the current protocol group (80.7 ± 35.6), but this was not statistically different when compared with the test group without a moist cotton pellet (78.3 ± 53.7) or the control groups. ConclusionsMoist cotton pellet placement may not be essential for MTA setting in apexification procedures or situations in which the apical surface of the MTA is against a moist opening of greater than 1 mm.

The Effect of One-Step or Two-Step MTA Plug and Tooth Apical Width on Coronal Leakage in Open Apex Teeth.

Mineral trioxide aggregate (MTA) has been suggested as an effective material for apical barrier, forming an effective seal against bacterial leakage in teeth with open apices. MTA needs moisture for setting; which can come from the apical region or a moist cotton pellet. This study was intended to compare bacterial leakage in one- and two-step MTA apical barrier technique in open apices with different diameters. The root canals of 52 extracted human maxillary incisors were prepared and open apices in two different diameters of 1 and 1.4 mm were created. The samples put in experimental groups randomly. A 4-mm thickness of MTA was placed as apical barrier for both one- and two-step methods. In one-step groups (1.4 mm diameter; n=12 and 1 mm diameter; n=12), the samples were obturated immediately after placing MTA plug. For two-step groups (1.4 mm diameter; n=12 and 1 mm diameter; n=12), a moist cotton pellet was placed over the MTA plug for 3 days before root canal obturation. Four samples served as positive/negative control groups. After one week, microleakage was evaluated using bacterial penetration technique and results were statistically analyzed utilizing SPSS software and Chi-square test. In one-step technique 13 and in two-step technique 12 samples showed bacterial leakage. There was no statistically significant differences between two techniques (Chi square, P=1). The difference between the results related to 1 and 1.4 mm apical foramens was also not significant (P=1). Also 12 and 13 samples showed bacterial contamination in teeth with 1 mm and 1.4 mm apical foramens, respectively (P=1). It seems that leakage of MTA apical plug using one- and two-step technique is comparable; however, in vivo investigations are highly recommended for more accurate results.

Apical Sealing Ability of MTA in Different Liquid to Powder Ratios and Packing Methods.

In apical surgery, after apicoectomy and retro-preparation of canal, a retrofil material is applied to seal the apical region of the root canal. Mineral trioxide aggregate (MTA) is the gold standard material for this purpose. Changing water/powder ratios of MTA affects its properties. The purpose of this in vitro study was to determine the effect of liquid/powder ratio of retrofil MTA on apical dye leakage, and also compare two packing techniques for MTA. In this in vitro study, 126 intact single-root extracted teeth were instrumented using step-back technique, and obturated with lateral condensation method. The apical 3 mm of roots was resected, and retrograde preparation was performed by an ultrasonic device. Specimens were randomly assigned to 6 groups of 20 each and 6 teeth served as positive and negative controls. All teeth were retrofilled with White ProRoot MTA. Three groups were retrofilled with 0.28, 0.33, and 0.40 water/powder ratios of MTA and packed with plugger; the other three groups were retrofilled with 0.28, 0.33, and 0.40 water/powder ratios and packed with wet-cotton. Linear dye leakage was used to check apical sealing ability, and data were statistically analyzed using Kruskal-Wallis test. In 0.40 liquid/powder ratio the best applicator for packing MTA was plugger. In 0.28 liquid/powder ratio, moist cotton pellet was the best applicator; in 0.33 liquid/powder ratio, there was no significant difference between the two techniques. Under the condition of this in vitro study, packing with moist cotton pellet in lower liquid/powder ratios of MTA, as well as packing with a plugger in higher liquid/powder ration decreased apical dye leakage.

Effect of Setting Conditions on Mineral Trioxide Aggregate Flexural Strength

This study evaluated the effect of setting conditions (time and hydration) on mineral trioxide aggregate (MTA) flexural strength. MTA beam specimens were allowed to set for either 24 or 72 hours with specimens exposed to moisture on either one or two specimen surfaces. These moisture conditions were used to simulate MTA setting with only external tissue moisture (one-sided moisture) versus tissue moisture in combination with a moistened intracanal cotton pellet (two-sided moisture). Ten specimens were stored at 37°C under each of the four experimental setting conditions (1) 24-hour/moist/2-sided; (2) 24-hour/moist/1-sided; (3) 72-hour/moist/2-sided; (4) 72-hour/moist/1-sided. After storage at respective setting conditions, MTA specimens were tested to failure with three-point bend test to measure flexural strength. Flexural strength of the 24h/moist/2-sided specimens, 14.27 ± 1.96 MPa, was significantly higher (p ≤ 0.05) than the flexural strength values associated with conditions two, three, and four, respectively, 10.77 ± 1.44, 11.16 ± 0.96, 11.18 ± 0.99 MPa, which were not significantly different from each other (p > 0.05). Clinically, these results suggest that a moistened cotton pellet should be placed on the intracanal MTA surface under a temporary restoration; and if possible, to optimize flexural strength, the moistened pellet should only remain in place for 24 hours.