Washout Resistance Research Articles

Effects of an Experimental Calcium Aluminosilicate Cement on the Viability of Murine Odontoblast-like Cells

IntroductionQuick-setting calcium aluminosilicate cement with improved washout resistance is a potential substitute for calcium silicate cements in endodontics. This study examined the effect of an experimental calcium aluminosilicate cement (Quick-Set; Primus Consulting, Bradenton, FL) on the viability of odontoblast-like cells. MethodsThe biocompatibility of Quick-Set and white ProRoot MTA (WMTA; Dentsply Tulsa Dental Specialties, Tulsa, OK) cements and their eluents was evaluated using a murine dental papilla–derived odontoblast-like cell line (MDPC-23); 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to examine the effects of the 2 hydraulic cements on mitochondrial metabolic activity. Flow cytometry and confocal laser scanning microscopy were used to identify the effects of the 2 cements on cell death–induced plasma membrane permeability to fluorescent dyes and DNA stains. ResultsAfter the first week of immersion in culture medium, Quick-Set and WMTA were more cytotoxic than the Teflon-negative control (P < .05), and the cells exhibited more apoptosis/necrosis than Teflon (P < .05). After the second week of immersion, the 2 cements were as biocompatible as Teflon (P > .05), with cells exhibiting minimal apoptosis/necrosis. Eluents from the set cements at 1:1 dilution were significantly more cytotoxic that eluents at 1:10 or 1:100 dilution (P < .05). ConclusionsQuick-Set and WMTA exhibited similar cytotoxicity profiles. They possess negligible in vitro toxicologic risks after time-dependent elution of toxic components.

Premixed, injectable PLA-modified calcium deficient apatite biocement (cd-AB) with washout resistance

By using a non-aqueous solution as the mixing liquid, the washout resistance of the calcium deficient apatite biocement (cd-AB) was significantly improved, over that of the conventional method of using cd-AB with water as the liquid phase. In this study, premixed and injectable cd-AB was prepared, which had the advantage of being stable in the syringe and hardens only after being delivered to the defect area. The cd-AB powder with a Ca/P ratio of 1.5 consists of a mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). A solution of polylactide (PLA) in N-methyl-2-pyrrolidone (NMP) was used as the liquid phase of the premixed cd-AB. The premixed cd-AB paste injected into an aqueous environment exhibited excellent washout resistance. The premixed cd-AB had longer setting time and lower compressive strength than conventional cd-AB. The hydration products of premixed cd-AB were a mixture of calcium deficient hydroxyapatite (cd-HA) and PLA. In vitro Tris–HCl immersion tests demonstrated that the premixed cd-AB could be degradable. The results revealed that the premixed cd-AB was cytocompatible and had no adverse effects on the attachment and proliferation of MG-63 osteoblast-like cells in vitro. The most distinct advantages of premixed and injectable PLA-modified cd-AB were its excellent washout resistance and in vitro degradability, suggesting that it may be a promising candidate for bone repair.

In Vivo Characteristics of Premixed Calcium Phosphate Cements When Implanted in Subcutaneous Tissues and Periodontal Bone Defects.

Previous studies showed that water-free, premixed calcium phosphate cements (Pre-CPCs) exhibited longer hardening times and lower strengths than conventional CPCs, but were stable in the package. The materials hardened only after being delivered to a wet environment and formed hydroxyapatite as the only product. Pre-CPCs also demonstrated good washout resistance and excellent biocompatibility when implanted in subcutaneous tissues in rats. The present study evaluated characteristics of Pre-CPCs when implanted in subcutaneous tissues (Study I) and used for repairing surgically created two-wall periodontal defects (Study II). Pre-CPC pastes were prepared by combining CPC powders that consisted of CPC-1: Ca4(PO4)2O and CaHPO4, CPC-2: α-Ca3(PO4)2 and CaCO3 or CPC-3: DCPA and Ca(OH)2 with a glycerol at powder-to-liquid mass ratios of 3.5, 2.5, and 2.5, respectively. In each cement mixture, the Ca to P molar ratio was 1.67. The glycerol contained Na2HPO4 (30 mass %) and hydroxypropyl methylcellulose (0.55 %) to accelerate cement hardening and improve washout resistance, respectively. In Study I, the test materials were implanted subcutaneously in rats. Four weeks after the operation, the animals were sacrificed and histopathological observations were performed. The results showed that all of the implanted materials exhibited very slight or negligible inflammatory reactions in tissues contacted with the implants. In Study II, the mandibular premolar teeth of mature beagle dogs were extracted. One month later, two-wall periodontal bone defects were surgically created adjacent to the teeth of the mandibular bone. The defects were filled with the Pre-CPC pastes and the flaps replaced in the preoperative position. The dogs were sacrificed at 1, 3 and 6 months after surgery and sections of filled defects resected. Results showed that one month after surgery, the implanted Pre-CPC-1 paste was partially replaced by bone and was converted to bone at 6 months. The pockets filled with Pre-CPC-2 were completely covered by newly formed bone in 1 month. The Pre-CPC-2 was partially replaced by trabecular bone in 1 month and was completely replaced by bone in 6 months. Examination of 1 month and 3 month samples indicated that Pre-CPC-2 resorbed and was replaced by bone more rapidly than Pre-CPC 1. Both Pre-CPC pastes were highly osteoconductive. When implanted in periodontal defects, Pre-CPC-2 was replaced by bone more rapidly than Pre-CPC-1.

Optimization of Cement Grouts Containing Silica Fume and Viscosity Modifying Admixture

There is an increasing need to identify the effect of mix composition on the rheological properties of cementitious grouts using minislump, Marsh cone, cohesion plate, washout test, and cubes to determine the fluidity, the cohesion, and other mechanical properties of grouting applications. Mixture proportioning involves the tailoring of several parameters to achieve adequate fluidity, cohesion, washout resistance and compressive strength. This paper proposes a statistical design approach using a composite fractional factorial design which was carried out to model the influence of key parameters on the performance of cement grouts. The responses relate to performance included minislump, flow time using Marsh cone, cohesion measured by Lombardi plate meter, washout mass loss and compressive strength at 3, 7, and 28 days. The statistical models are valid for mixtures with water-to-binder ratio of 0.37–0.53, 0.4–1.8% addition of high-range water reducer (HRWR) by mass of binder, 4–12% additive of silica fume as replacement of cement by mass, and 0.02–0.8% addition of viscosity modifying admixture (VMA) by mass of binder. The models enable the identification of underlying factors and interactions that influence the modeled responses of cement grout. The comparison between the predicted and measured responses indicated good accuracy of the established models to describe the effect of the independent variables on the fluidity, cohesion, washout resistance and the compressive strength. This paper demonstrates the usefulness of the models to better understand trade-offs between parameters. The multiparametric optimization is used to establish isoresponses for a desirability function for cement grout. An increase of HRWR led to an increase of fluidity and washout, a reduction in plate cohesion value, and a reduction in the Marsh cone time. An increase of VMA demonstrated a reduction of fluidity and the washout mass loss, and an increase of Marsh cone time and plate cohesion. Results indicate that the use of silica fume increased the cohesion plate and Marsh cone, and reduced the minislump. Additionally, the silica fume improved the compressive strength and the washout resistance.

Physical and Chemical Properties of New-generation Endodontic Materials

Introduction Mineral trioxide aggregate (MTA), white and gray, has many uses in endodontic therapy but is limited by its difficult handling characteristics. This study compared the physical and chemical properties of white MTA (WMTA) with three experimental root-end filling materials: Capasio (Primus Consulting, Bradenton, FL), Ceramicrete-D (Tulsa Dental Specialties/Argonne National Laboratory, Argonne, IL), and Generex-A (Dentsply Tulsa Dental Specialties, Tulsa, OK). Methods The setting time and radiopacity were tested using International Organization for Standardization (ISO) 6876 methods. Compressive strength was measured following the ISO 9917 method. The pH of the materials was measured after mixing. A novel test was developed for washout resistance of the materials immediately after placement. Data were compared by analysis of variance and Sidak post hoc analysis ( p < 0.05) for compressive strength and washout resistance. Results The setting time of Generex-A was half that of WMTA. All materials met the ISO 6876 requirements for radiopacity. The compressive strengths after 7 days decreased in this order: Generex-A > Capasio > WMTA > Ceramicrete-D. The initial pH of Capasio and Generex-A were alkaline, similar to WMTA, whereas that of Ceramicrete-D was acidic. Significantly, alternative materials remained in situ after the washout test, whereas WMTA was displaced from the retropreparations. Conclusions The clinical handling and washout resistance of the alternative materials were far superior to WMTA. The radiopacity, compressive strength, and washout resistance make Generex-A and Capasio materials suitable for further study. Ceramicrete-D was weaker, less radiopaque, and initially acidic.

Properties of anti-washout-type calcium silicate bone cements containing gelatin

Novel washout-resistant bone substitute materials consisting of gelatin-containing calcium silicate cements (CSCs) were developed. The washout resistance, setting time, diametral tensile strength (DTS), morphology, and phase composition of the hybrid cements were evaluated. The results indicated that the dominant phase of beta-Ca(2)SiO(4) for the SiO(2)-CaO powders increased with an increase in the CaO content of the sols. After mixing with water, the setting times of the CSCs ranged from 10 to 29 min, increasing with a decrease in the amount of CaO in the sols. Addition of gelatin into the CSC significantly prolonged (P < 0.05) the setting time by about 2 and 8 times, respectively, for 5% and 10% gelatin. However, the presence of gelatin appreciably improved the anti-washout and brittle properties of the cements without adversely affecting mechanical strength. It was concluded that 5% gelatin-containing CSC may be useful as bioactive bone repair materials.

β-TCP/MCPM-based premixed calcium phosphate cements

Novel premixed calcium phosphate cements (CPCs) were prepared by combining cement liquids comprised of glycerol or polyethylene glycol with CPC powders that consisted of β-tricalcium phosphate (β-TCP) and monocalcium phosphate monohydrate (MCPM). Changing the powder to liquid mass ratio enabled the setting time to be regulated, and improved the compressive strength of the CPCs. Although some ratios of the new premixed CPCs had long setting times, these ranged from 12.4 to 27.8 min which is much shorter than the hour or more reported previously for a premixed CPC. The premixed CPCs had tolerable washout resistance before final setting, and the cements had strengths matching that of cancellous bone (5–10 MPa); their maximum compressive strength was up to 12 MPa. The inflammatory response around the premixed CPCs implanted in the subcutaneous tissue in rabbits was more prominent than that of apatite cement. These differences might be due to the much faster resorption rate of the premixed CPCs.

Self-flowing underwater concrete mixtures

The placement of conventional concrete mixtures in underwater construction results in a high percentage of material loss owing to washout of cement paste. The current paper presents the influence of antiwashout admixture (AWA) on various properties of concrete. Eleven self-flowing concrete (SFC) mixtures using type II cement were proportioned. A combination of low water–cement (w/c), high cement contents, AWAs, fly ash and silica fume were used to enhance the resistance of fresh concrete to washout. The concrete mixtures were proportioned to be highly flowable, self-levelling and cohesive. The w/c materials ratios ranged between 0·35 and 0·39, which corresponds to a typical underwater concrete mixture. The concrete mixtures were tested for slump, slump flow, washout resistance and compressive strength. The compressive strength of each concrete mixture cast under water was determined at 3, 7 and 28 days and compared with the compressive strength of the same concrete mixture cast under normal conditions (in air). Test results indicated that the use of an AWA facilitates the production of flowable concrete mixtures with the added benefit of lower washout loss. Concrete mixture proportioned using type II cement and fly ash at a 15% level of replacement was found to develop SFC that had better fresh and hardened properties and was more resistant to washout. The self-flowing underwater concretes developed 28-day compressive strengths ranging from 20 to 28 MPa.

Improvement of the Light Stability of Automotive Water Borne Coatings: a Difficult Task

One of the most important current challenges for paint manufacturers is the reduction of volatile organic compounds (VOC) in their formulations. As a potential compliant technology for VOC reduction, water borne clear coats are predicted to develop strongly over the coming years. It must be stated that any impairment of the light stabilising performance of these water borne clear coats is unacceptable in the automotive industry. Due to the lack of techniques for the effective and homogeneous incorporation of light stabilisers, which are in general hydrophobic substances, into water borne clear coats, new product forms addressing this issue have become mandatory. Progress has been made with the development of water compatible product forms of water insoluble hydrophobic additives by using a Novel Encapsulated Additives Technology (NEAT) micro encapsulation techniques. NEAT enables the development of water borne clear coats for automotive application that show the same performance level as current state of the art solvent borne systems. By this novel encapsulation technology, the best UVA’s and HALS are made available for use in aqueous systems. The easy incorporation of the NEAT light stabilizers requires no need for co-solvents. NEAT light stabilizers offer a permanent protection due to a high wash-out resistance and they do not show a negative influence on transparency and gloss.

Fast Setting Calcium Phosphate Cement-Chitosan Composite: Mechanical Properties and Dissolution Rates

Calcium phosphate cement (CPC) can self-harden in vivo to form hydroxyapatite (HA) with excellent osteoconductivity. In recent studies, CPC-chitosan composites are developed with high mechanical strength and washout resistance. The objectives of the present study are to optimize the setting time and mechanical properties of a CPC-chitosan composite by tailoring the chitosan content, and to evaluate the bioresorbability by using an in vitro dissolution model. Six chitosan mass fractions are tested: 0, 10, 15, 20, 25, and 30%. Specimens are immersed in solutions with pH ranging from 3.5 to 5 to simulate the acidic environments produced by osteoclasts in vivo. Dissolution is measured as the fraction of mass loss versus immersion time from 7d to 28d. The CPC-chitosan composite with 20% by mass chitosan has a setting time (mean+/-SD; n=4) of 13 1 min, significantly less than 87 7 min for CPC control without chitosan (p<0.05). The composite flexural strength (mean+/-SD; n 1/4 6) was 14 2 MPa, significantly higher than 4 1 MPa of CPC control (p<0.05). At an intermediate pH of 4.5, the fraction of mass loss for CPC with 20% chitosan and CPC control without chitosan are not significantly different (p>0.1). The dissolution rates (fraction of mass loss per day,%/d) were 1.05 for CPC control and 1.08 for CPC-chitosan. In summary, a CPC-chitosan composite is developed with fast-setting and a flexural strength three-fold of that of CPC control without chitosan. Both materials are soluble in acidic environments, indicating that adding chitosan did not compromise the bioresorbability of CPC. The strong and resorbable CPC-chitosan composite may be useful in moderate stress-bearing craniofacial and orthopedic repairs.

Evaluation of soldering, washout and thermal fatigue resistance of advanced metal materials for aluminum die-casting dies

Anviloy1150, H13, Mo-785, Ti–6Al–4V, Ni-718, cast iron, and copper-base alloys have been evaluated for their resistances to soldering, washout, and thermal fatigue. Anviloy1150 shows the best soldering and washout resistance, followed by Ti–6Al–4V, Mo-785, H13, and Ni-718. Anviloy1150 and Mo-785 also show the best resistance to thermal fatigue and H13 is in the middle while Ti–6Al–4V shows very bad thermal fatigue resistance. Difficulty is found to evaluate the thermal fatigue resistance of Ni-718.

Premixed calcium-phosphate cement pastes.

A self-hardening calcium-phosphate cement (CPC) containing Ca(4)(PO(4))(2)O and CaHPO(4) has been shown in clinical studies to be efficacious for repairing bone defects. This and several other similar CPCs harden in 10 min with the use of a phosphate solution as the liquid and form hydroxyapatite (HA) as the product. The present study investigated the properties of water-free, glycerol-containing CPC pastes that are stable in the package and would harden only after being delivered to a defect site where glycerol-tissue fluids exchange occurs. Premixed CPC pastes were prepared by combining cement liquids containing glycerol and various amounts of hydroxypropyl methylcellulose/Na(2)HPO(4), with CPC powders that contained (1) Ca(4)(PO(4))(2)O and CaHPO(4), (2) alpha-Ca(3)(PO(4))(2) and CaCO(3), or (3) CaHPO(4) and Ca(OH)(2). The hardening times and 1-d and 7-d diametral tensile strengths were measured on samples that hardened in an in vitro model that allowed exchange of glycerol and physiologic-like solution (PLS) through fritted glass slides at 37 degrees C. All pastes had excellent washout resistance; they remained intact and hardened while immersed in PLS and formed HA as products. Newman-Keuls multiple comparison tests indicated that the Na(2)HPO(4) amount, not the hydroxypropyl methylcellulose (HMC) amount, significantly (p < 0.05) affected the strength and hardening time. Although the premixed CPCs generally have longer hardening times and lower strengths, these pastes have excellent washout resistance before hardening and can be prepared in advance under well-controlled conditions.

압축강도에 따른 수중불분리 콘크리트의 배합설계에 관한 연구

At present, the antiwashout underwater concretes are used as popular construction materials in European countries, the United States and Japan. The water-soluble polymers in the antiwashout underwater concretes provide excellent segregation or washout resistance, self-compaction and self-leveling property to the concretes. The purpose of this study is to recommend to optimum mix proportions of antiwashout underwater concretes according to compressive strength of 300kgf/<TEX>$\textrm{cm}^2$</TEX> to 500kgf/<TEX>$\textrm{cm}^2$</TEX>. The antiwashout underwater concretes are prepared with various unit cement content, unit water content, sand-aggregate ratio, unit antiwashout agent and superplasticizer content. And they are tested for flowability, and compressive strength. From the test results, it is possible to recommend the optimum mix proportions of antiwashout underwater concretes according to compressive strengths within the range of 300kgf/<TEX>$\textrm{cm}^2$</TEX> to 500kgf/<TEX>$\textrm{cm}^2$</TEX>.

Relationship between Washout Resistance and Rheological Properties of High-Performance Underwater Concrete

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Artificial Intelligence Model for Flowable Concrete Mixtures Used in Underwater Construction and Repair

This research explores the use of artificial neural networks (ANNs) to predict the rheological and mechanical properties of underwater concrete (UWC) mixtures and evaluate the sensitivity of such properties to variations in mixture ingredients. ANNs mimic the structure and operation of biological neurons and have the unique ability of self-learning, mapping, and functional approximation. Details of the development of the proposed ANN model, its architecture, training, and validation are presented. A database incorporating 175 UWC mixtures from 9 different studies was developed to train and test the ANN model. The data is arranged in a patterned format. Each pattern contains an input vector that includes quantity values of the mixture variables influencing the behavior of UWC mixtures and a corresponding output vector that includes the rheological or mechanical property to be modeled. Results show the ANN model thus developed is not only capable of accurately predicting slump, slump-flow, washout resistance, and compressive strength of underwater concrete mixtures used in the training process, but it can also effectively predict the properties for new mixtures designed within the practical range of the input parameters used in the training process with an absolute error of 4.6, 10.6, 10.6, and 4.4%, respectively.

Experimental design to optimize high-volume of fly ash grout in the presence of welan gum and superplasticizer

Applications such as soil, rock and oil-well grouting all require enormous amounts of cement and are good examples of areas where a high volume of fly ash could partially replace cement to produce low-cost, environmentally safe and durable concrete. There is an increasing need to identify the rheological properties of cement grout using a simple test to determine the fluidity, and other properties of underwater grouts such as washout resistance and compressive strength.

Factorial design modelling of mix proportion parameters of underwater composite cement grouts

Abstract There is an increasing need to identify the rheological properties of cement grout using a simple test to determine the fluidity, and other properties of underwater applications such as washout resistance and compressive strength. This paper reviews statistical models developed using a factorial design that was carried out to model the influence of key parameters on properties affecting the performance of underwater cement grout. Such responses of fluidity included minislump and flow time measured by Marsh cone, washout resistance, unit weight, and compressive strength. The models are valid for mixes with 0.35–0.55 water-to-binder ratio (W/B), 0.053–0.141% of antiwashout admixture (AWA), by mass of water, and 0.4–1.8% (dry extract) of superplasticizer (SP), by mass of binder. Two types of underwater grout were tested: the first one made with cement and the second one made with 20% of pulverised fuel ash (PFA) replacement, by mass of binder. Also presented are the derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of underwater cement grout. Such parameters can be useful to reduce the test protocol needed for proportioning of underwater cement grout. This paper attempts also to demonstrate the usefulness of the models to better understand tradeoffs between parameters and compare the responses obtained from the various test methods that are highlighted.

Experiment design to evaluate interaction of high-range water-reducer and antiwashout admixture in high-performance cement grout

The injection of cement grout in water-saturated medium and the sealing of anchorages require the use of grout with high resistance to water dilution to enhance in-situ performance. This can be achieved by reducing the W/C and incorporating an antiwashout admixture (AWA) to enhance the stability. Such admixture can increase the viscosity and yield stress and necessitate higher dosage of high-range water-reducer (HRWR) to maintain the desired fluidity. Cement-based grouts with 0.30 to 0.50 W/C and different combinations of AWA and HRWR were evaluated. The study was undertaken to highlight the influence of W/C and dosage of chemical admixtures on fluidity, washout resistance, and residual compressive strength (RCS) of the underwater-cast grout. Statistical models established using a statistical design of experiments indicate that the W/C has greater effect on changes in minislump flow, washout, and RCS than the concentrations of HRWR and AWA. On the other hand, for mixtures prepared with a fixed W/C of 0.40, the models show that measured responses are highly affected by the dosages and interaction of both admixtures. Trade-off between fluidity and washout resistance and means to optimize mixture proportioning to enhance the resistance to water dilution without adversely affecting fluidity are discussed.

Effect of Mixture Composition on Washout Resistance of Highly Flowable Underwater Concrete

The underwater casting of relatively thin lifts of concrete in water requires the proportioning of highly flowable concrete that can resist water dilution and segregation and spread readily into place. This paper describes an investigation conducted to examine the effects of anti-washout admixture concentration, water-cementitious materials ratio, and binder composition on the washout resistance of highly flowable concrete. The data presented is important given the increasing demand to secure quality repairs underwater and the higher environmental constraints to limit water pollution caused by such operations.

Application of factorial models to predict the effect of anti-washout admixture, superplasticizer and cement on slump, flow time and washout resistance of underwater concrete

The anti-washout underwater concrete posses different properties from conventional underwater concrete. When an anti-washout admixture is mixed with concrete, the viscosity of the concrete is increased and its resistance to washout is enhanced. Superplasticizer ensures enough concrete fluidity to spread readily in place without vibration. A factorial design was carried out to mathematically model the influence of three key parameters on slump, flow time measured by Orimet and mass loss by washout of underwater concrete. The parameters considered in this investigation were the dosage of cement, the concentrations of anti-washout admixture and superplasticizer. All mixes were made with 0.43 water/cement ratio which correspond a typical underwater concrete. The proposed models are valid for concretes with cement dosage ranging between 420 kg/m3 to 520 kg/m3 and the concentrations of anti-washout admixture and superplasticizer varying between 0.02%–0.13% and 0.4%–1.8%, by mass of cement, respectively.