Efeito da adição de microfibras de lã de vidro na tenacidade à ruptura de pastas de cimento para poços de petróleo

Although there are a wide variety of additives that act in fresh state, to adjust the properties of cement, there is also a search by additions that improve the tenacity of the cement in the hardened state. This, in turn, can often be increased by inserting fibers, which act on the deflection of microcracks. This study aimed to use a microfiber glass wool (silica-based) as an additive reinforcing the cement matrix, improving the rupture tenacity, in order to prevent the propagation of microcracks in the cement sheath commonly found in oil wells submitted to high temperatures. The fibers were added at different concentrations, 2 to 5% (BWOC) and varied average sizes, grinding for 90 s, 180 s, 300 s, 600 s. The cement slurries were made with a density of 1,90 g/ cm3 (15,6 lb/gal), using Portland cement CPP- Special Class as the hydraulic binder and 40% silica flour. The characterization of the fiber was made by scanning electron microscopy (SEM), particle size by sieving, X-ray fluorescence (XRF), X-ray diffraction (XRD) and thermogravimetry (TG / DTG). Were performed technological tests set by the API (American Petroleum Institute) by rheology, stability, free water, compressive strength, as well as testing rupture energy, elastic modulus and permeability. The characterization results showed good thermal stability of the microfiber glass wool for application in oil wells submitted to steam injection and, also, that from the particle size data, it was possible to suggest that microfibers milled up to 300 s, are ideal to act as reinforcement to the cement slurries. The rheological parameters, there was committal of plastic viscosity when larger lengths were inserted of microfiber (F90). The values obtained by free water and stability were presented according to API. The mechanical properties, the incorporation of microfiber to the cement slurries gave better rupture tenacity, as compared to reference cement slurries. The values of compressive strength, elastic modulus and permeability have been maintained with respect to the reference cement slurries. Thus, cement slurries reinforced with microfiber glass wool can ensure good application for cementing oil wells submitted to steam injection, which requires control of microcracks, due to the thermal gradients

Influência da adição de cinza do bagaço de cana calcinada em sistemas de pastas para cimentação de poços petrolíferos

Cementing operation is one of the most important stages in the oil well drilling processes and has main function to form hydraulic seal between the various permeable zones traversed by the well. However, several problems may occur with the cement sheath, either during primary cementing or during the well production period. Cements low resistance can cause fissures in the cement sheath and compromise the mechanical integrity of the annular, resulting in contamination of groundwater and producing zones. Several researches show that biomass ash, in particular, those generated by the sugarcane industry have pozzolanic activity and can be added in the composition of the cementing slurries in diverse applications, providing improvements in mechanical properties, revenue and cement durability. Due to the importance of a low cost additive that increases the mechanical properties in a well cementing operations, this study aimed to potentiate the use of sugarcane bagasse ash as pozzolanic material, evaluate the mechanisms of action of this one on cement pastes properties and apply this material in systems slurries aimed to cementing a well with 800 m depth and geothermal gradient of 1.7 °F/100 ft, as much primary cementing operations as squeeze. To do this, the ash beneficiation methods were realized through the processes of grinding, sifting and reburning (calcination) and then characterization by X-ray fluorescence, XRD, TG / DTG, specific surface area, particle size distribution by laser diffraction and mass specific. Moreover, the ash pozzolanic activity added to the cement at concentrations of 0%, 20% and 40% BWOC was evaluated by pozzolanic activity index with lime and with Portland cement. The evaluation of the pozzolanic activity by XRD, TG / DTG and compressive strength confirmed the ash reactivity and indicated that the addition of 20% in the composition of cement slurries produces improvement 34% in the mechanical properties of the slurry cured. Cement slurries properties evaluated by rheological measurements, fluid loss, free fluid, slurry sedimentation, thickening time and sonic strength (UCA) were satisfactory and showed the viability of using the sugarcane ash in cement slurries composition for well cementing

Estudo do comportamento mecânico de areias artificialmente cimentadas

Soil improved with the addition of cement have been utilized as an alternative to the construction of various types of geotechnical works, almost always present economic and environmental advantages. This paper presents a study on the usage of cement in the improvement of mechanical properties of sandy soils, characteristic of the region of Natal, collected from its dunes. This research was made in order to analyze the influence of cement content, voids, and also including water immersion and confining pressure. Samples molded from cement-soil mixtures were tested for unconfined compression tests and triaxial tests. The samples had the percentage of cement mixed in 2.5%, 5% and 10% by weight. The cement agent used was the Portland Cement of High Early strength(CPV-ARI), which promoted agility to the experimental procedure for presenting a rapid gain in strenght. The void ratio used ranged from 0.7 (more compact), 0,9 and 1,1(softer). The soil under study can be considered as pure sand. In general, it can be stated that the larger the amount of cement added to the sand studied is, the greater ultimate strength will be. Likewise, as more compact the soil is, the less void ratio and more resistant it will be present. The confining pressure tends to increase the resistance of the specimens. The cementing adopted grades showed that the use of different criteria for failure did not significantly alter the stress-strain parameters for the sand studied. The angle of friction values were found within the typical range of medium and compact sands. Cementing acted in the sand providing an intercepted cohesion which increased enhancing the potential cementation. In triaxial compression tests, the sand with void ratio is equal to 0.7 and showed the expected behavior for a compact sand while the stress-strain behavior of the same sand with the void ratio of 0.9 tended to be expected for the soft sand as well

Adição de geomanta e tecido não tecido de polipropileno em cimentos geopoliméricos de pega rápida

Geopolymers are cementing materials that depict a number of advantages compared to Portland cement. Contrary to the latter, geopolymers are synthesized at room temperature, thus significantly reducing the emission of CO2 to the atmosphere. Moreover, the composition and synthesis reactions can be tailored to adjust the setting time of the material as well as its compressive mechanical strength. It is then possible to produce geopolymeric cements with short setting times and high compressive strength, although relatively brittle. The objective of the present study was to produce and characterize composite materials by reinforcing fastsetting geopolymeric matrixes with polypropylene geosynthetics (geomats and geotextiles) in an attempt to improve the toughness and tensile strength of the cementing material. Geosynthetics have been increasingly used to reinforce engineering structures, providing higher strength and better toughness. In particular, polypropylene nonwoven and geomats depict other attractive properties such as low density, durability, impact absorption and resistance to abrasion. Fast-setting geopolymers were then synthesized and reinforced with polypropylene nonwoven and geomats. The mechanical strength of the materials, reinforced or not, was characterized. The results showed that relatively short setting times and adequate flowing behavior were achieved by adjusting the composition of the geopolymer. In addition, it is possible to improve the fracture resistance of geopolymeric cements by adding polypropylene geosynthetics. The best results were achieved by reinforcing geopolymer with polypropylene TNT

A Mineral Trioxide Aggregate Sealer Stimulated Mineralization

The aim of this study was to evaluate the rat subcutaneous tissue response to implanted polyethylene tubes filled with Endo-CPM-Sealer (Portland Cement Modified Sealer) (EGEO S.R.L., Buenos Aires, Argentina) compared with Sealapex (SybronEndo, Glendora, CA) and Angelus MTA (Angelus, Londrina, Brazil). These materials were placed in polyethylene and dentin tubes and implanted into dorsal connective tissue of Wistar rats for 7, 15, 30, 60, and 90 days. The specimens were prepared to be stained with hematoxylin and eosin or Von Kossa or not stained for polarized light. Qualitative and quantitative evaluations of the reaction were performed. Both materials caused mild to moderate reactions at 7 days that decreased with time. The response was similar to the control on the 30th day with Endo-CPM-Sealer and Angelus MTA and on the 60th day with Sealapex. Mineralization and granulations birefringent to the polarized light were observed with all materials. it was possible to conclude that Endo-CPM-Sealer was biocompatible and stimulated mineralization. (J Endod 2009;35:256-260)

pH, Calcium Ion Release, and Setting Time of an Experimental Mineral Trioxide Aggregate-based Root Canal Sealer

Introduction: An experimental mineral trioxide aggregate sealer (MTAS) has been developed for use as a root canal sealer. The aim of this study was to evaluate the setting time, pH, and calcium ion release of MTAS compared with white Portland cement (CPB-40; Votorantin Cimentos, Camargo Correa SA, Pedro Leopoldo, MG, Brazil), white MTA Angelus (MTA; Angelus, Londrina, PR, Brazil), and AH Plus (Dentsply DeTrey, Konstanz, Germany). Methods: For the evaluation of setting time, each material was analyzed using Gilmore-type needles. Polyethylene tubes with the materials were immersed in distilled water for the measurement of pH (digital pH meter) and calcium release (atomic absorption spectrophotometry). The evaluations were performed at 3, 6, 12, 24, and 48 hours and 7, 14, and 28 days. Data were analyzed by analysis of variance and the Tukey test at 5% significance level. Results: MTAS showed higher calcium release at all experimental periods, a greater increase in pH up to 48 hours and the longest setting time. Conclusions: MTAS presented favorable properties for its indication as a root canal sealer. (J Endod 2011;37:844-846)

Radiographic effect of different radiopacifiers on a potential retrograde filling material

Objective. The objective of this study was to evaluate the radiopacity of white Portland cement (PC) associated with bismuth oxide (Bi(2)O(3)), barium sulfate (BaSO(4)), iodoform (CHI(3)), and zirconium oxide (ZrO(2)). White mineral trioxide aggregate (WMTA) and PC without radiopacifier were used as positive and negative controls, respectively.Study design. Following International Organization for Standardization (ISO) 6876/2001, 5 circular specimens (10 x 1 mm) were made from each material. After the materials set, radiographs were taken using occlusal film and a graduated aluminum step-wedge varying in thickness from 2 to 16 mm. The dental X-ray unit (GE1000) was set at 50 Kvp, 10 mA, 18 pulses/s, and distance of 33.5 cm. The radiographs were digitized, and radiopacity was compared with the aluminum step-wedge, using Wixwin-2000 software (Gendex). Data (mm Al) were analyzed using analysis of variance and Tukey tests.Results. The PC + Bi(2)O(3) and WMTA samples presented greater radiopacity (5.88 and 5.72 mm Al, respectively), followed by PC + ZrO(2) (3.87 mm Al) and PC + CHI(3) (3.50 mm Al). The PC + BaSO(4) and PC samples presented the lowest radiopacity values (2.35 and 1.69 mm Al, respectively), which were below the minimum value recommended by the ISO.Conclusion. Analysis of the present results led to the conclusion that all of the materials tested presented acceptable radiopacity, except PC + BaSO(4) and pure PC. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: 628-632)

Evaluation of the physical and chemical properties of two commercial and three experimental root-end filling materials

Objective. The aim of this study was to evaluate the pH, calcium release, setting time, and solubility of two commercially available mineral trioxide aggregate (MTA) cements (white MTA Angelus and MTA Bio), and of three experimental cements (light-cured MTA, Portland cement with 20% bismuth oxide and 5% calcium sulfate, and an epoxy resin-based cement).Study design. For evaluation of pH and calcium ion release, polyethylene tubes with 1.0 mm internal diameter and 10.0 mm length were filled with the cements and immediately immersed in flasks containing 10 mL deionized water. After 3, 24, 72, and 168 hours, the tubes were removed and the water from the previous container was measured for its pH and calcium content with a pH meter and an atomic absorption spectrophotometer. For analysis of the setting time, Gilmore needles weighing 100 g and 456.5 g were used, in accordance with the American Society for Testing and Materials specification no. C266-03. Solubility of each cement was also tested.Results. All the cements were alkaline and released calcium ions, with a declining trend over time. After 3 hours, Portland cement + bismuth oxide and MTA Bio had the highest pH and light-cured MTA the lowest. After 1 week, MTA Bio had the highest pH and light-cured MTA and epoxy resin-based cement the lowest. Regarding calcium ion release, after 3 hours, Portland cement + bismuth oxide showed the highest release. After 1 week, MTA Bio had the highest. Epoxy resin-based cement and light-cured MTA had the lowest calcium release in all evaluation periods. Regarding setting times, white MTA Angelus and MTA Bio had the shortest, Portland cement + bismuth oxide had an intermediate setting time, and the epoxy resin-based cement had the longest. The materials that showed the lowest solubility values were the epoxy resin-based cement, Portland cement + bismuth oxide, and light-cured MTA. The highest solubility values were presented in white MTA Angelus and MTA Bio.Conclusions. The white MTA Angelus and MTA Bio had the shortest setting times, higher pH and calcium ion release, and the highest solubility. In contrast, the epoxy resin-based cement and light-cured MTA showed lower values of solubility, pH, and calcium ion release. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 110: 250-256)

Biocompatibility of an experimental MTA sealer implanted in the rat subcutaneous: Quantitative and immunohistochemical evaluation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Glucose reactivity with filling materials as a limitation for using the glucose leakage model

Aim To evaluate the reactivity of different endodontic materials and sealers with glucose and to asses the reliability of the glucose leakage model in measuring penetration of glucose through these materials.Methodology Ten uniform discs (radius 5 mm, thickness 2 mm) were made of each of the following materials: Portland cement, MTA (grey and white), sealer 26, calcium sulphate, calcium hydroxide [Ca(OH)(2)], AH26,Epiphany, Resilon, gutta-percha and dentine. After storing the discs for 1 week at 37 degrees C and humid conditions, they were immersed in 0.2 mg mL(-1) glucose solution in a test tube. The concentration of glucose was evaluated using an enzymatic reaction after 1 week. Statistical analysis was performed with the ANOVA and Dunnett tests at a significant level of P < 0.05.Results Portland cement, MTA, Ca(OH)(2) and sealer 26 reduced the concentration in the test tube of glucose significantly after 1 week (P < 0.05). Calcium sulphate reduced the concentration of glucose, but the difference in concentrations was not significant (P = 0.054).Conclusions Portland cement, MTA, Ca(OH)(2) and sealer 26 react with a 0.2 mg mL(-1) glucose solution. Therefore, these materials should not be evaluated for sealing ability with the glucose leakage model.

Inorganic-Organic Nanocomposite Assembly Using Collagen as a Template and Sodium Tripolyphosphate as a Biomimetic Analog of Matrix Phosphoprotein

Nanocomposites created with polycarboxylic acid alone as a stabilization agent for prenucleation clusters-derived amorphous calcium phosphate exhibit nonperiodic apatite deposition. In the present study, we report the use of inorganic polyphosphate as a biomimetic analog of matrix phosphoprotein for directing poly(acrylic acid)-stabilized amorphous nano-precursor phases to assemble into periodic apatite-collagen nanocomposites. The sorption and desorption characteristics of sodium tripolyphosphate to type I collagen were examined. Periodic nanocomposite assembly with collagen as a template was demonstrated with TEM and SEM using a Portland cement-based resin composite and a phosphate-containing simulated body fluid. Apatite was detected within the collagen at 24 h and became more distinct at 48 h, with prenucleation clusters attaching to the collagen fibril surface during the initial infiltration stage. Apatite-collagen nanocomposites at 72 h were heavily mineralized with periodically arranged intrafibrillar apatite platelets. Defect-containing nanocomposites caused by desorption of TPP from collagen fibrils were observed in regions lacking the inorganic phase.

Evaluation of the Effects of Endodontic Materials on Fibroblast Viability and Cytokine Production

Introduction: Recently, a new sealer composed of Portland cement named Endo-CPM-Sealer was developed. The aim of this study was to investigate the effects of Endo-CPM-Sealer (EGEO SRL, Buenos Aires, Argentina), Sealapex (Sybron Endo, Glendora, CA), and Angelus MTA (Angelus, Londrina, Brazil) on cell viability and cytokine (interleukin [IL]-1 beta and IL-6) production by mouse fibroblasts. Methods: Millipore culture plate inserts with polyethylene tubes filled with materials were placed into 24-well cell culture plates with mouse fibroblasts. Cells cultured with only empty polyethylene tubes were used as the control. After 24 hours, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay was used to evaluate the cell viability. For cytokine assay, mouse fibroblasts were incubated in 24-well flat-bottom plates with set material disks at the bottom. Cells cultured without the material disks served as the negative control. After 24 hours of incubation, culture media were collected for cytokine evaluation by using an enzyme-linked immunosorbent assay. The data were statistically analyzed by analysis of variance and Bonferroni correction. Results: Endo-CPM-Sealer, Sealapex, and Angelus MTA did not inhibit the cell viability. All materials induced IL-6 releasing, but the amount was not statistically significant compared with the control group. Angelus MTA induced IL-1 beta releasing significantly more than the control. Conclusions: All materials were not considered cytotoxic in fibroblast culture. (J Endod 2009;35:1577-1579)

In vitro evaluation of apical microleakage using different root-end filling materials

The objective of this study was to evaluate the apical leakage of retrograde cavities filled with Portland Cement (Concrebrás S/A-MG-Brazil), ProRoot MTA™ (Dentsply International, Johnson City, TN, USA) and Sealapex (Kerr Corporation, Orange, California, USA) with addition of zinc oxide (Odahcam Herpo Produtos Dentários Ltda, Rio de Janeiro, RJ, Brazil). Forty-two extracted single-rooted human teeth were decoronated and used for this study. The root canals were instrumented at 1.0mm short of the apical foramen using the step-back technique to an apical ISO size 60. The roots were obturated with gutta-percha points and sealer Sealapex (Kerr Corporation-USA) and then 3mm of each root apex was sectioned at a 90° angle. Ultrasonic retrograde preparation was performed with a diamond tip to 3mm depth and the roots were randomly divided into 3 groups according to the filling material: G1-Portland, G2-ProRoot MTA, G3- Sealapex zinc oxide-added cement. The root surfaces were covered with nail varnish up to 2mm from the apical foramen, immersed in simulated tissue fluid for 30 days, and then immersed in 0.2% Rhodamine B solution for 24 hours for evaluation of marginal leakage. The results showed mean leakage of 0.75, 0.35 and 0.35 for groups 1, 2 and 3, respectively; however, Kruskal-Wallis test revealed that there was no statistically significant difference among the results (p>0.05).

The effect of endodontic materials on the optical density of dyes used in marginal leakage studies

The aim of this study was to determine the effect of the exposure of different endodontic materials to different dye solutions by evaluating the optical density of the dye solutions. Seventy-five plastic tubes were filled with one of the following materials: AH Plus, Sealapex, Portland cement, MTA (Angelus and Pro Root) and fifteen control plastic tubes were not. Each specimen of material and control was immersed in a container with 1 ml of each dye solution. A 0.1 ml-dye solution aliquote was removed before immersion and after 12, 24, 48 and 72 hours of each specimen immersion to record its optical density (OD) in a spectrophotometer. Statistical analysis was performed with ANOVA and Tukey tests (5%). No significant difference was found among any of the solution OD values for AH Plus cement. Portland cement promoted different OD values after 12 hours of immersion. MTA-Angelus cement presented different OD values only for 2% rhodamine B and the MTA-Pro Root cement presented different OD values in all 2% rhodamine B samples. Sealapex cement promoted a reduction in the India Ink OD values. Dye evaluation through OD seems to be an interesting method to select the best dye solution to use in a given marginal leakage study.

Análise da influência de um reforço de solo-cimento compactado na extremidade superior de estacas escavadas, sob carregamentos horizontais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)