Avaliação da influência da agitação ultrassônica na resistência de união de dois materiais reparadores utilizados para selar perfurações na furca / Assessment of the influence of ultrasonic agitation on the joint resistance of two repairing materials used to seal perforations in the burning / Evaluación de la influencia de la agitación ultrasónica en la resistencia de la unión de dos materiales de reparación utilizados para sellar otras perforaciones

Avaliou-se a influência da utilização da agitação ultrassônica na resistência de união à dentina, por meio de push-out, proporcionada pelos cimentos MTA-Angelus branco (MTA) e Biodentine (BD), empregados no selamento de perfurações de furca. Foram utilizados 48 primeiros ou segundos molares inferiores, com raízes não fusionadas, distantes cerca de 2 mm entre si na porção cervical das mesmas. Os dentes foram acessados e, em seguida, as raízes foram seccionadas transversalmente abaixo da junção cemento-esmalte. Os dentes foram montados em blocos de silicona de adição e perfurações de furca realizadas em seus assoalhos paralelamente ao longo eixo dos dentes e perpendiculares aos assoalhos dentais. A amostra foi dividida em quatro grupos (n = 12) em função do material reparador e da utilização ou não da agitação ultrassônica (AU). Quando empregada, a AU foi aplicada em 2 ciclos de 20 segundos por meio de inserto cônico liso acionado por ultrassom piezoelétrico. Concluídos os selamentos eles foram protegidos com cimento de ionômero de vidro e os dentes imersos em PBS. Decorridos 7 dias discos com 1 mm de altura foram retirados dos assoalhos dentais com auxílio de cortadora metalográfica e levados à máquina de ensaio universal. Os resultados expressos em MPa foram submetidos aos testes ANOVA dois fatores e de Bonferroni. Os maiores valores de resistência obtidos foram no grupo Biodentine com ultrassom (29,41 MPa), seguidos em ordem decrescente pelos grupos Biodentine sem ultrassom; MTA com ultrassom e MTA sem ultrassom (3,72 MPa). Nas condições do estudo concluiu-se que o BD apresentou maior resistência de união à dentina radicular; ainda, que a agitação ultrassônica influenciou positivamente na resistência de união do material à dentina.

We evaluated the influence of the use of ultrasonic agitation on the resistance to the dentin, by means of push-out, provided by the white MTA-Angelus (MTA) and Biodentine (BD) cements, used in the sealing of drilling holes. 48 first or second lower molars were used, with unfused roots, about 2 mm apart in the cervical portion of them. The teeth were accessed and then the roots were sectioned transversely below the cementenamel junction. The teeth were mounted in addition silicon blocks and hole drills performed on their floors parallel along the axis of the teeth and perpendicular to the dental floorings. The sample was divided into four groups (n = 12) depending on the repair material and whether ultrasonic agitation (AU) was used. When employed, the AU was applied in 2 20-second cycles by means of a smooth conical insert activated by piezoelectric ultrasound. Once the seals were completed, they were protected with glass ionomer cement and the teeth immersed in PBS. After 7 days, 1 mm high disks were removed from the dental floorboards with the aid of a metallographic cutter and taken to the universal test machine. Results expressed in MPa were submitted to two-factor and Bonferroni ANOVA tests. The highest resistance values obtained were in the group Biodentine with ultrasound (29.41 MPa), followed in descending order by the groups Biodentine without ultrasound; MTA with ultrasound and MTA without ultrasound (3.72 MPa). Under the conditions of the study, it was concluded that BD showed greater resistance to root dentin binding; also, that ultrasonic agitation positively influenced the resistance of the material to dentin binding.

influencia del uso de la agitación ultrasónica sobre la resistencia de la unión a la dentina se evaluó mediante un estiramiento, proporcionado por los cementos blancos (MTA) y biodentinos (BD) MTA-Angelus, empleados en el sello de los taladros. Se utilizaron los primeros o segundos molares inferiores, con raíces sin fundir, a unos 2 mm de distancia en la porción cervical de las raíces. Se accedió a los dientes y luego las raíces se seccionaron transversalmente por debajo de la unión cemento-enamel. Los dientes se ensamblaron además bloques de silicona y agujeros de perforación en sus pisos a lo largo del eje de los dientes y perpendiculares al suelo dental. La muestra se dividió en cuatro grupos (n = 12) según el material de reparación y si se utilizó o no la agitación ultrasónica (AU). Cuando se empleó, la UA se aplicó en 2 ciclos de 20 segundos mediante una inserción cónica suave activada por ultrasonido piezoeléctrico. Una vez concluidos los sellos, se protegieron con cemento ionómero de vidrio y los dientes se sumergieron en PBS. Al cabo de 7 días, los discos de 1 mm de altura se retiraron del suelo de corte metálico y se llevaron a la máquina de ensayo universal. Los resultados expresados como MPa se presentaron a las pruebas de dos factores ANOVA y Bonferroni. Los valores de resistencia más altos obtenidos fueron en el grupo de Biodentina con ultrasonido (29,41 MPa), seguidos en orden descendente por los grupos de Biodentina sin ultrasonido; MTA de ultrasonido y MTA libre de ultrasonido (3,72 MPa). En las condiciones del estudio se concluyó que la DB mostró mayor resistencia de la unión a la dentina raíz; y que la agitación ultrasónica tuvo una influencia positiva en la resistencia del material a la dentina.

Apical extrusion of sodium hypochlorite in immature teeth: comparison of three different cleaning protocols.

This study compared standard needle irrigation, passive ultrasonic irrigation, XP-Endo Finisher and Easy Clean in the apical extrusion of sodium hypochlorite (NaOCl) in a model simulating immature teeth. Ten bovine teeth were maintained in suspension in a container with the apical portion in contact with 0.2% agarose gel containing 0.1% metacresol purple. The canals were irrigated with 2.5% NaOCl, according to each irrigation protocol. After 3 min, apical extrusion of NaOCl was observed by the colour gel change when in contact with NaOCl. The containers were photographed, and the NaOCl extrusion area was measured. All protocols showed NaOCl extrusion, providing similar area (P > 0.05). Considering the similarity among the studied protocols, all of them can be considered during the endodontic treatment of immature teeth. Further studies on the particularities of immature teeth should be performed to evaluate cell viability, cleaning efficiency, disinfection capacity and dentin removal promoted by the irrigation protocols.

Avaliação do escurecimento dentinário causado por cimentos obturadores endodônticos em função do uso de agitação ultrassônica / Evaluation of dentin discoloration caused by endodontic root canal sealers due to ultrasonic agitation

Introdução: A descoloração da estrutura dentária representa um grande problema estético e uma das razões mais comuns pelas quais os pacientes vão ao cirurgião-dentista. Objetivo: O objetivo do presente estudo foi avaliar a descoloração dentinária causada pelo emprego dos cimentos obturadores endodônticos AH Plus, MTA Fillapex, Pulp Ca- nal Sealer EWT e Sealer Plus; além de avaliar a influência do uso da agitação ultrassônica (AUS). Métodos: Oitenta blocos de dentes bovinos foram confeccionados e tiveram cavidades circulares preparadas em suas faces palatinas, deixando remanescente de 2,0mm de espessura. Em seguida, os blocos foram randomicamente divididos em função do cimento utilizado e do uso ou não da AUS (n=10). A cor foi mensurada por meio de um espectrofotômetro após a inserção dos cimentos e restauração das cavidades, nos tempos: imediatamente após a inserção dos cimentos (T0 ), após 7 dias (T1 ) e após 180 dias (T2 ). Resultados: Observou-se alteração de cor clinicamente perceptível (ΔE>3,7) causada pelos quatro cimentos obturadores, tanto após 7 dias quanto após 180 dias. Não foram encontradas diferenças significativas entre os grupos nos dois tempos (p>0,05). Conclusões: Pôde-se concluir que os cimentos analisados causaram escurecimento dentinário clinicamente perceptível já após 7 dias, o qual perdurou por todo o período da análise; ainda, que a agitação ultrassônica não interferiu significativamente na ΔE, não influenciando na descoloração dentinária causada pelos cimentos testados (AU).

Introduction: Tooth discoloration is an aesthetic problem commonly reported by patients as one of the main reasons to seek a dentist. Thus, this study aimed to evaluate the dentin discoloration caused by AH Plus, MTA Fillapex, Sealer Plus and Pulp Canal Sealer EWT endodontic sealers, associated or not with ultrasonic agitation during the obturation. Methods: Round cavities were prepared on the palatal faces of eighty bovine teeth slabs, preserving a 2 mm of dentin thickness. The slabs were randomly separated in groups by type of sealer employed and based on the use or not of ultrasonic agitation (n = 10). The color was measured by a spectrophotometer after sealer insertion into the cavities (T0), after 7 (T1) and 180 days (T2). Results: Clinically detectable discoloration (∆E > 3,7) was present in all groups at T1 and T2. Statistically significant differences were not found between T1 and T2 (P > .05). Conclusion: All endodontic sealers tested caused dentin discoloration after 7 days. The color-changing persisted thought the entire experimental period. Moreover, the ultrasonic agitation did not influence on the dentin discoloration caused by the endodontic sealers tested (AU).

Efficacy and Cytotoxicity of Binary Mixtures as Root Canal Filling Solvents.

OBJECTIVES: This study reports the efficacy of two solvent mixtures on the dissolution of gutta-percha and AH Plus sealer, together with the cytotoxicity. METHODS: Methyl ethyl ketone (MEK), orange oil, tetrachloroethylene, MEK/tetrachloroethylene (1:1), MEK/orange oil (1:1), and chloroform (control) were tested. Twelve groups (n = 15) of standardized stainless-steel molds filled with softened gutta-percha cones and twelve (n = 15) filled with AH Plus were immersed in the corresponding mixture or individual solvent, in an ultrasonic bath, for either 2 or 5 min. The effect of the solvents was assessed qualitatively by a topographical analysis (scanning electron microscopy) and chemical analysis (Fourier transform infrared spectroscopy), and quantitatively by a weight loss and viscoelastic property (dynamic mechanical analysis) evaluation. The cytotoxicity was assessed on MG63 human osteoblastic cells. RESULTS: The mixtures did not show the formation of new compounds. Both presented significantly higher efficacies compared to their individual solvents, suggesting a synergistic effect. Their dissolution efficacy was similar to that of chloroform, showing high cytocompatibility. CONCLUSIONS: The proposed strategy, incorporating ultrasound agitation and profiting from the synergy of adequate solvents, might enhance root canal cleanliness allowing a single-step procedure to dissolve gutta-percha and the sealer remnants, while assuring cytocompatibility with the periapical tissues.

Root canal debridement efficacy of heated sodium hypochlorite in conjunction with passive ultrasonic agitation: An ex vivo study.

Background. This study aimed to investigate the endodontic debridement efficacy of different sodium hypochlorite (NaOCl) irrigation regimens with and without ultrasonic agitation, followed by ethylenediaminetetraacetic acid (EDTA) via scanning electron microscopy (SEM) after using a rotary instrumentation system. Methods. Mandibular premolars (n=50) were randomly divided into five experimental groups (n=10) for root canal instrumentation with ProTaper Universal rotary system up to F3. The root canal system was treated with intracanal-heated NaOCl (100°C) or preheated NaOCl (55°C), followed by ultrasonic agitation and EDTA treatment. Samples irrigated with conventional needle irrigation (CNI) using normal saline solution were used as controls. Debridement efficacy was analyzed by SEM. A five-point scale was used to estimate the presence/absence of debris for each canal segment (coronal, middle, and apical). The results were analyzed using one-way ANOVA and post hoc Tukey tests (P<0.05). Results. The experimental groups exhibited less debris compared to CNI with saline (P<0.05). The amount of debris decreased significantly for the group with NaOCl intracanal heating compared to extraoral heating. Ultrasonic agitation further enhanced the root canal debridement efficacy of NaOCl. Conclusion. In summary, intracanal heating of NaOCl with and without ultrasonic agitation followed by EDTA appears to be a promising method to flush debris from the root canal system.

Influence of ultrasonic agitation on bond strength, marginal adaptation, and tooth discoloration provided by three coronary barrier endodontic materials.

OBJECTIVES: The effect of ultrasonic agitation (UA) on bond strength and adaptation of cervical plugs prepared with MTA Angelus (MTA), MTA Repair HP (MTAHP), and Biodentine (BIO) was evaluated. Dentin discoloration caused by the materials/treatment was also assessed. MATERIALS AND METHODS: Seventy-two single rooted teeth were divided into six groups depending on the materials/treatment. After cervical plug preparation, dentin discs were excised for the push-out test; additional discs were analyzed under the confocal microscope to determine adaptation (gaps occurrence). For dentin discoloration analysis (ΔE), blocks of bovine incisors had cavities prepared and filled with the materials/treatment (from 7 to 180 days). RESULTS: Both bond strength and adaptation were positively influenced by UA (P < 0.05). Comparison between materials showed an advantage for BIO when compared to MTAHP (P < 0.05). The best and worst results were provided by BIO/UA (12.66 MPa and 1.87%) and MTAHP (2.54 MPa and 28.58%), respectively. For ΔE, significant differences were observed throughout the periods. Just the MTA without UA exhibited noticeable discoloration at 180 days (P < 0.05). CONCLUSIONS: UA favored a better adaptation of the materials to the dentin root, resulting in higher bond strength and adaptation of the materials to the root canal walls. Moreover, UA reduced MTA discoloration, keeping it imperceptible over the period evaluated. CLINICAL RELEVANCE: The better adaptation and higher bond strength provided by UA can be considered clinically relevant due to the importance of maintaining blood clot integrity and the possible esthetic compromise provided by reparative materials when used as coronary barrier in regenerative procedures.

X-ray diffraction analysis of MTA mixed and placed with various techniques.

OBJECTIVES: The aim of this study was to evaluate the effect of various mixing techniques as well as the effect of ultrasonic placement on hydration of mineral trioxide aggregate (MTA) using X-ray diffraction (XRD) analysis. MATERIALS AND METHODS: One gram of ProRoot MTA and MTA Angelus powder was mixed with a 0.34-g of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 s at 4500 rpm or by manual mixing followed by application of a compaction pressure of 3.22 MPa for 1 min. The mixtures were transferred into the XRD sample holder with minimum pressure. Indirect ultrasonic activation was applied to half of the specimens. All specimens were incubated at 37 °C and 100% humidity for 4 days. Samples were analyzed by XRD. Phase identification was accomplished by use of search-match software utilizing International Centre for Diffraction Data (ICDD). RESULTS: All specimens comprised tricalcium silicate, calcium carbonate, and bismuth oxide. A calcium hydroxide phase was formed in all ProRoot specimens whereas among MTA Angelus groups, it was found only in the sample mixed mechanically and placed by ultrasonication. CONCLUSIONS: Mechanical mixing followed by ultrasonication did not confer a significant disadvantage in terms of hydration characteristics of MTA. CLINICAL RELEVANCE: Clinicians vary in the way they mix and place MTA. These variations might affect their physical characteristics and clinical performance. For ProRoot MTA, the mixing and placement methods did not affect its rheological properties, whereas for MTA Angelus, mechanical mixing combined with ultrasonic placement enhanced the calcium hydroxide phase formation.

The effect of ultrasonic vibration and surfactant additive on fabrication of 53.5gr/mm silicon echelle grating with low surface roughness in alkaline KOH solution.

In the silicon echelle grating fabrication process, the "pseudo-mask" formed by the hydrogen bubbles generated during the etching process is the reason causing high surface roughness and poor surface quality of blazed plane. Based upon the ultrasonic mechanical effect and contact angle reduced by surfactant additive, ultrasonic vibration, isopropyl alcohol (IPA) and 2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) were used to improve surface quality of 53.5gr/mm echelle grating. The surface roughness Rq is smaller than 18nm, 7nm and 2nm when using ultrasonic vibration, IPA and TMDD respectively. The surface roughness Rq is smaller than 5nm and 1.5nm respectively when combining ultrasonic vibration with IPA and TMDD. The experimental results indicated that the combination of ultrasonic agitation and surfactant additive (IPA&TMDD) could obtain a lower surface roughness of blazed plane in silicon echelle grating fabrication process.

Recovery of lithium and cobalt from spent lithium-ion batteries using organic acids: Process optimization and kinetic aspects.

An environmentally-friendly route based on hydrometallurgy was investigated for the recovery of cobalt and lithium from spent lithium ion batteries (LIBs) using different organic acids (citric acid, Dl-malic acid, oxalic acid and acetic acid). In this investigation, response surface methodology (RSM) was utilized to optimize leaching parameters including solid to liquid ratio (S/L), temperature, acid concentration, type of organic acid and hydrogen peroxide concentration. Based on the results obtained from optimizing procedure, temperature was recognized as the most influential parameter. In addition, while 81% of cobalt was recovered, the maximum lithium recovery of 92% was achieved at the optimum leaching condition of 60°C, S/L: 30gL-1, citric acid concentration: 2M, hydrogen peroxide concentration: 1.25Vol.% and leaching time: 2h. Furthermore, results displayed that ultrasonic agitation will enhance the recovery of lithium and cobalt. It was found that the kinetics of cobalt leaching is controlled by surface chemical reaction at temperatures lower than 45°C. However, diffusion through the product layer at temperatures higher than 45°C controls the rate of cobalt leaching. Rate of lithium reaction is controlled by diffusion through the product layer at all the temperatures studied.

Efficacy of different techniques for removal of calcium hydroxide-chlorhexidine paste from root canals.

The purpose of this study was to evaluate the efficacy of different techniques for removal of combined calcium hydroxide [Ca(OH)2] and chlorhexidine paste from root canals. Fifty single-rooted human teeth were prepared by oscillatory and rotary systems and filled with a paste of Ca(OH)2 and 2% chlorhexidine gel. After incubation for 14 days, the specimens were divided into 5 groups (n = 10), and the medication was removed by 1 of 5 different procedures. In group 1 (control), removal procedures involved a master apical file, foraminal debridement, and 5 mL of saline solution applied with the NaviTip irrigation needle. Group 2 was treated the same as group 1, but in addition 0.5 mL of 17% ethylenediaminetetraacetic acid was used for 3 minutes. In group 3, ultrasonic agitation was performed for 1 minute. Group 4 was treated as group 2, but the NaviTip FX needle was used for irrigation. In group 5, a master apical file, foraminal debridement, and 3-minute application of 5 mL of citric acid were used. After the root-cleaning procedures, the crowns were removed at the cementoenamel junction, and the roots were split longitudinally into halves. The success of intracanal medicament removal was observed under stereoscopic microscope and scanning electron microscope. Remnants of Ca(OH)2 were found in all experimental groups, regardless of the removal technique used. There was no statistically significant difference in cleanliness in the apical third of the root canal among groups 1, 2, and 3. Group 4 showed the best and group 5 the worst results with statistically significant differences. Overall, the NaviTip FX irrigation needle technique was more efficient in removing a Ca(OH)2-chlorhexidine paste from the root canal.

Effects of ultrasonic agitation and surfactant additive on surface roughness of Si (111) crystal plane in alkaline KOH solution.

In the silicon wet etching process, the "pseudo-mask" formed by the hydrogen bubbles generated during the etching process is the reason causing high surface roughness and poor surface quality. Based upon the ultrasonic mechanical effect and wettability enhanced by isopropyl alcohol (IPA), ultrasonic agitation and IPA were used to improve surface quality of Si (111) crystal plane during silicon wet etching process. The surface roughness Rq is smaller than 15 nm when using ultrasonic agitation and Rq is smaller than 7 nm when using IPA. When the range of IPA concentration (mass fraction, wt%) is 5-20%, the ultrasonic frequency is 100 kHz and the ultrasound intensity is 30-50 W/L, the surface roughness Rq is smaller than 2 nm when combining ultrasonic agitation and IPA. The surface roughness Rq is equal to 1 nm when the mass fraction of IPA, ultrasound intensity and the ultrasonic frequency is 20%, 50 W and 100 kHz respectively. The experimental results indicated that the combination of ultrasonic agitation and IPA could obtain a lower surface roughness of Si (111) crystal plane in silicon wet etching process.

Study on Improving Thickness Uniformity of Microfluidic Chip Mold in the Electroforming Process.

Electroformed microfluidic chip mold faces the problem of uneven thickness, which decreases the dimensional accuracy of the mold, and increases the production cost. To fabricate a mold with uniform thickness, two methods are investigated. Firstly, experiments are carried out to study how the ultrasonic agitation affects the thickness uniformity of the mold. It is found that the thickness uniformity is maximally improved by about 30% after 2 h electroforming under 200 kHz and 500 W ultrasonic agitation. Secondly, adding a second cathode, a method suitable for long-time electroforming is studied by numerical simulation. The simulation results show that with a 4 mm width second cathode used, the thickness uniformity is improved by about 30% after 2 h of electroforming, and that with electroforming time extended, the thickness uniformity is improved more obviously. After 22 h electroforming, the thickness uniformity is increased by about 45%. Finally, by comparing two methods, the method of adding a second cathode is chosen, and a microfluidic chip mold is made with the help of a specially designed second cathode. The result shows that the thickness uniformity of the mold is increased by about 50%, which is in good agreement with the simulation results.

Effects of ultrasonic agitation on adhesion strength of micro electroforming Ni layer on Cu substrate.

Micro electroforming is an important technology, which is widely used for fabricating micro metal devices in MEMS. The micro metal devices have the problem of poor adhesion strength, which has dramatically influenced the dimensional accuracy of the devices and seriously limited the development of the micro electroforming technology. In order to improve the adhesion strength, ultrasonic agitation method is applied during the micro electroforming process in this paper. To explore the effect of the ultrasonic agitation, micro electroforming experiments were carried out under ultrasonic and ultrasonic-free conditions. The effects of the ultrasonic agitation on the micro electroforming process were investigated by polarization and alternating current (a.c.) impedance methods. The real surface area of the electroforming layer was measured by cyclic voltammetry method. The compressive stress and the crystallite size of the electroforming layer were measured by X-ray Diffraction (XRD) method. The adhesion strength of the electroforming layer was measured by scratch test. The experimental results show that the imposition of the ultrasonic agitation decreases the polarization overpotential and increases the charge transfer process at the electrode-electrolyte interface during the electroforming process. The ultrasonic agitation increases the crystallite size and the real surface area, and reduces the compressive stress. Then the adhesion strength is improved about 47% by the ultrasonic agitation in average. In addition, mechanisms of the ultrasonic agitation improving the adhesion strength are originally explored in this paper. The mechanisms are that the ultrasonic agitation increases the crystallite size, which reduces the compressive stress. The lower the compressive stress is, the larger the adhesion strength is. Furthermore, the ultrasonic agitation increases the real surface area, enhances the mechanical interlocking strength and consequently increases the adhesion strength. This work contributes to fabricating the electroforming layer with large adhesion strength.

Effect of varying water-to-powder ratios and ultrasonic placement on the compressive strength of mineral trioxide aggregate.

INTRODUCTION: The purpose of this study was to compare the compressive strength of mineral trioxide aggregate (MTA) when mixed with 2 different water-to-powder (WP) proportions using either hand or ultrasonic placement. METHODS: Tooth-colored ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and white MTA Angelus (Angelus Soluçoes Odontologicas, Londrina, Brazil) were investigated. One gram of each MTA powder was mixed with either 0.34 or 0.40 g distilled water. The 4 groups were further divided into 2 groups of 5 specimens for each of the following techniques: conventional (ie, hand placement) and placement using indirect ultrasonic activation for 30 seconds. All specimens were subjected to compressive strength testing after 4 days. The results were statistically analyzed with multivariate analysis of variance and Tukey Honestly Significant Difference tests at a significance level of P < .05. RESULTS: The mean compressive strength values of ProRoot MTA (84.17 ± 22.68) were significantly greater than those of MTA Angelus (47.71 ± 14.29) (P < .01). Specimens mixed with the 0.34 WP ratio had higher compressive strength values (72.85 ± 25.77) than those mixed with the 0.40 WP ratio (56.69 ± 24.85) (P < .05). The highest compressive strength values were recorded for ProRoot MTA specimens that were mixed in the 0.34 WP ratio, and then the samples were placed with ultrasonic activation (mean = 91.35 MPa). The lowest values were recorded for MTA Angelus samples that were mixed in the 0.40 WP ratio, and the specimens were placed without ultrasonic activation (mean = 36.36 MPa). Ultrasonic activation had no significant difference in terms of compressive strength. CONCLUSIONS: When using ProRoot MTA and MTA Angelus, higher WP ratios resulted in lower compressive strength values. Ultrasonication had no significant effect on the compressive strength of the material regardless of the WP ratio that was used. Therefore, adherence to the manufacturer's recommended WP ratio when preparing MTA for use in dental applications is advised.

Effect of various mixing and placement techniques on the flexural strength and porosity of mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to evaluate the effect of mechanical and manual mixing as well as the effect of ultrasonic agitation during placement on the flexural strength and porosity of mineral trioxide aggregate (MTA). METHODS: White ProRoot MTA and white MTA Angelus were used. One gram of each powder was mixed with a 0.34-g aliquot of distilled water. Specimens were mixed either by mechanical mixing of capsules for 30 seconds at 4500 rpm or by a saturation technique and application of a condensation pressure of 3.22 MPa for 1 minute. The mixed slurries of all materials were loaded into 2 × 2 × 25 mm molds for testing flexural strength and 3 × 4 mm molds for evaluation of porosity. Half of the specimens were placed in the stainless steel molds by using indirect ultrasonic activation. All specimens were incubated for 4 days. Micro-computed tomography was used to determine the porosity of each specimen, and a 3-point bending test was used to evaluate flexural strength. Tukey honestly significant difference and independent t tests were carried out to compare the means at a significance level of P < .05. RESULTS: Irrespective of mixing and placement techniques applied, the flexural strength values of ProRoot MTA were significantly greater than those of MTA Angelus (P < .05). A medium negative correlation was found between flexural strength values and total porosity percentage. CONCLUSIONS: Although mechanical mixing of encapsulated cements was quicker and provided more consistent mixes, this technique along with ultrasonic agitation was not associated with a significant advantage in terms of flexural strength and total porosity over manual mixing.

Comparison of the efficacy of ethylene diamine tetraacetic acid and maleic acid in the removal of three calcium hydroxide intra-canal dressings: A spiral computerized tomography volumetric analysis.

AIM: To assess the efficacy of 17% ethylene diamine tetra acetic acid and 7% maleic acid in the removal of 3 calcium hydroxide preparations placed as intracanal medicaments. MATERIALS AND METHODS: The root canals of 60 single rooted premolars were prepared with a step back technique and randomly assigned into 3 experimental groups (n= 20). Group A was filled with plain calcium hydroxide mixed with distilled water in which barium sulfate was added for radio opacity, Group B was filled with Apexcal and Group C was filled with Metapex. After 7 days each group was divided into 2 sub groups (n= 10). The medicaments were retrieved with 17% EDTA (first sub group) and 7% maleic acid (second sub group). Along with the above irrigants manual and ultrasonic agitation was used. The pre and post removal volume of medicaments in root canals were measured using spiral computerized tomography. The percentage difference was calculated and statistically analyzed using Kruskal Wallis and Mann Whitney U test. RESULTS: 17% EDTA and 7% maleic acid efficiently removed calcium hydroxide, distilled water mixture (P= 0.218) and Apexcal (P= 0.684), whereas 7% maleic acid showed better retrieval capability of Metapex than 17% EDTA (P= 0.002). CONCLUSION: Calcium hydroxide, distilled water mixture and polyethylene glycol based calcium hydroxide were efficiently removed by 17% EDTA and 7% maleic acid. 7% maleic acid removed silicone oil based calcium hydroxide preparation better than 17% EDTA.