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Josette Camilleri - One of the best experts on this subject based on the ideXlab platform.
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Tricalcium Silicate based cements properties and modifications
Brazilian Oral Research, 2018Co-Authors: Marco Antonio Hungaro Duarte, Marina Angelica Marciano, Rodrigo Ricci Vivan, Mario Tanomaru Filho, Juliane Maria Guerreiro Tanomaru, Josette CamilleriAbstract:Mineral trioxide aggregate (MTA) has been widely used for different reparative procedures in endodontics. The extensive use of this cement for pulp capping, apexifications, apical surgeries, and revascularization is related to its ability to induce tissue repair and to stimulate mineralization. Several research studies have tested modifications in the composition of MTA-based cements in order to enhance their clinical performance. Novel formulations have been introduced in the market with the aim of increasing flowability. Important properties such as appropriate radiopacity and setting time, color stability, alkaline pH, release of calcium ions, and biocompatibility have to be considered in these new formulations. The latest research studies on the physical, chemical, and biological properties of Tricalcium Silicate-based cements are discussed in this critical review.
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the effect of mixing method on Tricalcium Silicate based cement
International Endodontic Journal, 2018Co-Authors: Jussaro Alves Duque, Josette Camilleri, Marco Antonio Hungaro Duarte, Samuel Lucas Fernandes, J P Bubola, Marina Angelica MarcianoAbstract:Aim To evaluate the effect of three methods of mixing on the physical and chemical properties of Tricalcium Silicate-based cements. Methodology The materials evaluated were MTA Angelus and Portland cement with 20% zirconium oxide (PC-20-Zr). The cements were mixed using a 3:1 powder to liquid ratio. The mixing methods were: manual (m), trituration (tr) and ultrasonic (us) activation. The materials were characterized by means of scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS). Flowability was analysed according to ANSI/ADA 57/2012. Initial and final setting times were assessed following ASTM C266/08. Volume change was evaluated using a micro-CT volumetric method. Solubility was analysed according to ADA 57/2012. pH and calcium ion release were measured after 3, 24, 72 and 168 h. Statistical analysis was performed using the two-way analysis of variance test. The level of significance was set at p = 0.05. Results The SEM analysis revealed that ultrasonic activation was associated with a homogeneous distribution of particles. Flowability, volume change and initial setting time were not influenced by the mixing method (p > 0.05). Solubility was influenced by the mixing method (p < 0.05). For pH, at 168 h significant differences were found between MTA-m and PC-20-Zr-m (p < 0.05). For calcium ion release, PC-20-Zr-tr had higher values than MTA-m at 3h, and MTA-tr had higher values than PC-20-Zr-m at 168h (p < 0.05). Conclusions The ultrasonic and trituration methods led to higher calcium ion release and pH compared with manual mixing for all cements; while the ultrasonic method produced smaller particles for the PC-20-Zr cement. Flow, setting times and volume change were not influenced by the mixing method used, however, it did have an impact on solubility. This article is protected by copyright. All rights reserved.
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Properties of Tricalcium Silicate Sealers
Journal of Endodontics, 2016Co-Authors: Issam Khalil, Alfred Naaman, Josette CamilleriAbstract:Abstract Introduction Sealers based on Tricalcium Silicate cement aim at an interaction of the sealer with the root canal wall, alkalinity with potential antimicrobial activity, and the ability to set in a wet field. The aim of this study was to characterize and investigate the properties of a new Tricalcium Silicate–based sealer and verify its compliance to ISO 6876 (2012). Methods A new Tricalcium Silicate–based sealer (Bio MM; St Joseph University, Beirut, Lebanon), BioRoot RCS (Septodont, St Maure de Fosses, France), and AH Plus (Dentsply, DeTrey, Konstanz, Germany) were investigated. Characterization using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis was performed. Furthermore, sealer setting time, flow, film thickness, and radiopacity were performed following ISO specifications. pH and ion leaching in solution were assessed by pH analysis and inductively coupled plasma. Results Bio MM and BioRoot RCS were both composed of Tricalcium Silicate and tantalum oxide in Bio MM and zirconium oxide in BioRoot RCS. In addition, the Bio MM contained calcium carbonate and a phosphate phase. The inorganic components of AH Plus were calcium tungstate and zirconium oxide. AH Plus complied with the ISO norms for both flow and film thickness. BioRoot RCS and Bio MM exhibited a lower flow and a higher film thickness than that specified for sealer cements in ISO 6876. All test sealers exhibited adequate radiopacity. Conclusions Bio MM interacted with physiologic solution, thus showing potential for bioactivity. Sealer properties were acceptable and comparable with other sealers available clinically.
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in situ assessment of the setting of Tricalcium Silicate based sealers using a dentin pressure model
Journal of Endodontics, 2015Co-Authors: Maria Xuereb, Denis Damidot, Paul Vella, Charles V Sammut, Josette CamilleriAbstract:Abstract Introduction EndoSequence BC Sealer (Brasseler, Savannah, GA) is a premixed Tricalcium Silicate–based root canal sealer that requires moisture from the root dentin to hydrate. The aim of this study was to investigate the setting of EndoSequence BC Sealer and other sealers in contact with human dentin in a simulated clinical environment. Methods EndoSequence BC Sealer, MTA Fillapex (Angelus, Londrina, Brazil), Septodont Sealer (Septodont, Saint Maur-des-Fosses, France), and Apexit Plus (Ivoclar, Schaan, Lichtenstein) were assessed. Caries-free lower premolars extracted for orthodontic purposes in patients aged 13–16 years were standardized to a 10-mm root length and were filled with test sealers and set up in a dentin pressure model for 14 days. In addition, set sealers immersed in physiologic solution for 14 days were also assessed. The set materials in solution and materials retrieved from the dentin pressure setup were characterized by scanning electron microscopy and X-ray diffraction analysis. The setting time and radiopacity were assessed using ISO 6876:2002 specifications. Furthermore, mineral ion leaching was evaluated by inductively coupled plasma mass spectrometry. Results All the sealers tested exhibited formation of a calcium phosphate phase when in contact with physiologic solution. Septodont Sealer and Apexit Plus did not exhibit the formation of a calcium phosphate phase in the dentin pressure setup. The fluid in the system was enough to allow the setting of EndoSequence BC Sealer, which did not set in a dry environment. All materials leached calcium with the Septodont Sealer, exhibiting double the calcium ion leaching compared with EndoSequence BC Sealer. Conclusions Using the dentinal fluid pressure system resulted in an adequate flow of dentinal fluid that allowed EndoSequence BC Sealer to set inside the root canal. Although the sealers tested were Tricalcium Silicate based, the hydration reaction and bioactivity in the presence of dentinal fluid were different to hydration in vitro. Thus, clinically, material bioactivity cannot be assumed.
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Hydration of biodentine, theracal LC, and a prototype Tricalcium Silicate-based dentin replacement material after pulp capping in entire tooth cultures
2014Co-Authors: Josette Camilleri, Patrick Laurent, Imad AboutAbstract:Introduction The calcium-releasing ability of pulp-capping materials induces pulp tissue regeneration. Tricalcium Silicate-based materials produce calcium hydroxide as a by-product of hydration. Assessment of hydration and calcium ion leaching is usually performed on samples that have been aged in physiological solution for a predetermined period of time. The hydration and activity of the materials in vivo may not be similar to those displayed in vitro because of insufficient fluid available in contact with dentin. The aim of this research was the assessment of hydration of Biodentine, Theracal LC, and a prototype radiopacified Tricalcium Silicate-based material after pulp capping and to compare it with direct hydration in an aqueous solution. Methods The extent of hydration of Biodentine, Theracal LC, and a prototype radiopacified Tricalcium Silicate-based material with a similar composition to Biodentine but not incorporating the additives was assessed by scanning electron microscopy and energy dispersive spectroscopy of polished specimens after being allowed to hydrate in Hank's balanced salt solution for 14 days. The extent of hydration was compared with material hydration when used as direct pulp capping materials by using a tooth culture model. Material activity was also assessed by x-ray diffraction analysis to investigate the deposition of calcium hydroxide by the materials, and calcium ion leaching in Hank's balanced salt solution was assessed by ion chromatography. Results Biodentine and the prototype Tricalcium Silicate cement hydrated and reaction by-products were deposited in the cement matrix both after pulp capping and when incubated in an aqueous solution. Calcium hydroxide was formed, and calcium ions were leached in solution. Theracal LC hydration was incomplete because of the limited moisture diffusion within the material. Thus, no calcium hydroxide was produced, and a lower calcium ion leaching was recorded. Conclusions Theracal LC had a heterogeneous structure with large unhydrated particles because not enough moisture was present to allow hydration to proceed. Biodentine composition was shown to be optimized, and the environmental conditions did not affect material microstructure. Biodentine exhibited formation of calcium hydroxide and calcium ion leaching, which are beneficial to the dental pulp.
Richard A. Livingston - One of the best experts on this subject based on the ideXlab platform.
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microscopic investigation of modified hydration kinetics in Tricalcium Silicate paste and mortar strength caused by dicalcium Silicate addition
Journal of Materials Research, 2008Co-Authors: Vanessa K. Peterson, Paul E. Stutzman, Richard A. LivingstonAbstract:It was recently revealed that some processes of hydrating Tricalcium Silicate are altered by the addition of dicalcium Silicate. Previous neutron scattering results revealed two critical tri/dicalcium Silicate compositions. At one composition, changes in the early time hydration kinetics were observed that result in the formation of more products (reflected in increased 28 day strength), despite dicalcium Silicate being essentially unreactive at early times. At the other composition, changes in the early-time hydration kinetics were observed that correspond to reduced strength. The current work uses scanning electron microscope analysis with backscattered electron imaging of 50 day hydrated tri- and dicalcium Silicate mortars to reveal that at the former critical composition increased hydration of the Tricalcium Silicate phase occurs, and at the latter critical composition, the amount of dicalcium Silicate reacted is decreased.
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state of water in hydrating Tricalcium Silicate and portland cement pastes as measured by quasi elastic neutron scattering
Journal of the American Ceramic Society, 2004Co-Authors: Jeffrey J Thomas, Stephen A Fitzgerald, D A Neumann, Richard A. LivingstonAbstract:Quasi-elastic neutron scattering (QENS) was used to monitor the state of water in portland cement and Tricalcium Silicate pastes during the first 2 days of hydration at three different temperatures. By applying a double-Lorentzian rather than a single-Lorentzian fitting function, the QENS signal from water at a given hydration time was divided into three separate populations arising from liquid water, chemically bound water, and constrained water. The constrained water population consisted of water adsorbed on surfaces and contained in very small (<10 nm) pores, and could be associated primarily with the calcium-Silicate-hydrate (C-S-H) phase. The rate of increase in the chemically bound water population closely followed the exothermic heat output, while the constrained water population increased more rapidly during the first several hours of hydration and then leveled off.
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in situ quasi elastic scattering characterization of particle size effects on the hydration of Tricalcium Silicate
Journal of Materials Research, 2004Co-Authors: Andrew J Allen, D A Neumann, J C Mclaughlin, Richard A. LivingstonAbstract:The effects of different particle size distributions on the real-time hydration of Tricalcium Silicate cement paste were studied in situ by quasi-elastic neutron scattering. The changing state of water in the cement system was followed as a function both of cement hydration time and of temperature for different initial particle size distributions. It was found that the length of the initial, dormant, induction period, together with the kinetics of hydration product nucleation and growth, depends on the hydration temperature but not on the particle size distribution. However, initial particle size does affect the total amount of cement hydrated, with finer particle size producing more hydrated cement. Furthermore, the diffusion-limited rate of hydration at later hydration time is largely determined by the initial Tricalcium Silicate particle size distribution.
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a neutron scattering study of the role of diffusion in the hydration of Tricalcium Silicate
Cement and Concrete Research, 2002Co-Authors: Stephen A Fitzgerald, Jeffrey J Thomas, D A Neumann, Richard A. LivingstonAbstract:Abstract Quasi-elastic neutron scattering was used to monitor the temperature-dependant hydration of Tricalcium Silicate and Portland cement. Results show that for some samples the degree of hydration is in fact higher at lower curing temperatures. To investigate this effect further, we performed a series of experiments in which samples are initially hydrated at one temperature and then the diffusion process limiting the long-term curing is monitored at a different temperature. The results confirm that the higher the initial curing temperature the more impervious are the product layers to later diffusion. In addition, it was found that the intrinsic activation energy for this diffusion process is much greater than the traditional values obtained using samples initially cured at different temperatures.
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characterization of the induction period in Tricalcium Silicate hydration by nuclear resonance reaction analysis
Journal of Materials Research, 2001Co-Authors: Richard A. Livingston, J S Schweitzer, C Rolfs, H. W. Becker, S. KubskyAbstract:Nuclear resonance reaction analysis has been applied for the first time to measure the development of the hydrogen depth profile in the early stages of hydration of Tricalcium Silicate using the 1 H( 15 N,αγ) 12 C reaction. The surface layer had an H concentration and thickness consistent with a few unit cells (1.1 nm) of tobermorite-like material. The inner regions exhibited diffusion-controlled growth with time until the hydrogen concentration approaches that of the surface layer at 4.25 ± 0.07 h. This event marked the end of the induction period and the onset of the rapid hydration reaction period.
Bart Van Meerbeek - One of the best experts on this subject based on the ideXlab platform.
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Preclinical effectiveness of an experimental Tricalcium Silicate cement on pulpal repair
Materials science & engineering. C Materials for biological applications, 2020Co-Authors: Mariano Simón Pedano, Imad About, Esther Hauben, Kirsten Van Landuyt, Zheyi Sun, Charlotte Jeanneau, Zhi Chen, Bart Van MeerbeekAbstract:Abstract Objectives To investigate the pulpal repair potential of an experimental zirconium-oxide containing Tricalcium-Silicate cement, referred to as ‘TCS 50’. Materials and methods The effect of TCS 50 on viability, proliferation, migration, and odontoblastic differentiation of human dental pulp cells (HDPCs) was assessed using XTT assay, in-vitro wound healing assay and RT-PCR, respectively. Additionally, the pulp-capping potential was evaluated using a vital human tooth model. Statistical analysis was performed using non-parametric Kruskal-Wallis test and post-hoc test (Mann-Whitney U test). The tests were performed at a significance level of α = 0.05. Results The effect of TCS 50 towards HDPCs was dose dependent. Undiluted TCS 50 extract showed no immediate adverse impact on cell viability (p > .05); however, it significantly inhibited proliferation and migration of HDPCs (p .05), and it significantly enhanced odontoblastic differentiation of HDPCs (p Conclusion TCS 50 is capable of generating an early pulp-healing reaction and therefore could serve as a promising pulp-capping agent.
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Experimental Tricalcium Silicate cement induces reparative dentinogenesis.
Dental materials : official publication of the Academy of Dental Materials, 2018Co-Authors: Mariano Simón Pedano, Bernardo Camargo, Esther Hauben, Stéphanie De Vleeschauwer, Kirsten Van Landuyt, Zhi Chen, Jan De Munck, Katleen Vandamme, Bart Van MeerbeekAbstract:Abstract Objectives To overcome shortcomings of hydraulic calcium-Silicate cements (hCSCs), an experimental Tricalcium Silicate (TCS) cement, named ‘TCS 50’, was developed. In vitro research showed that TCS 50 played no negative effect on the viability and proliferation of human dental pulp cells, and it induced cell odontogenic differentiation. The objective was to evaluate the pulpal repair potential of TCS 50 applied onto exposed minipig pulps. Methods Twenty permanent teeth from three minipigs were mechanically exposed and capped using TCS 50; half of the teeth were scheduled for 7-day and the other half for 70-day examination (n = 10). Commercial hCSCs ProRoot MTA and TheraCal LC were tested as references (n = 8). Tooth discoloration was examined visually. After animal sacrifice, the teeth were scanned using micro-computed tomography; inflammatory response at day 7 and day 70, mineralized tissue formation at day 70 were assessed histologically. Results Up to 70 days, TCS 50 induced no discoloration, ProRoot MTA generated gray/black discoloration in all teeth. For TCS 50, 40.0% pulps exhibited a mild/moderate inflammation at day 7. No inflammation was detected and complete reparative dentin with tubular structures was formed in all pulps after 70 days. ProRoot MTA induced a similar response, TheraCal LC generated a less favorable response in terms of initial inflammation and reparative dentin formation; however, these differences were not significant (Chi-square test of independence: p > 0.05). Significance TCS 50 induced reparative dentinogenesis in minipig pulps. It can be considered as a promising pulp-capping agent, also for aesthetic areas.
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modified Tricalcium Silicate cement formulations with added zirconium oxide
Clinical Oral Investigations, 2017Co-Authors: Kumiko Yoshihara, Mariano Simón Pedano, Kirsten Van Landuyt, Zhi Chen, Jan De Munck, Stevan M Cokic, Pong Pongprueksa, Eveline Putzeys, Bart Van MeerbeekAbstract:Objectives This study aims to investigate the effect of modifying Tricalcium Silicate (TCS) cements on three key properties by adding ZrO2.
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modified Tricalcium Silicate cement formulations with added zirconium oxide
Clinical Oral Investigations, 2017Co-Authors: Kumiko Yoshihara, Mariano Simón Pedano, Kirsten Van Landuyt, Zhi Chen, Jan De Munck, Stevan M Cokic, Pong Pongprueksa, Eveline Putzeys, Bart Van MeerbeekAbstract:This study aims to investigate the effect of modifying Tricalcium Silicate (TCS) cements on three key properties by adding ZrO2. TCS powders were prepared by adding ZrO2 at six different concentrations. The powders were mixed with 1 M CaCl2 solution at a 3:1 weight ratio. Biodentine (contains 5 wt.% ZrO2) served as control. To evaluate the potential effect on mechanical properties, the mini-fracture toughness (mini-FT) was measured. Regarding bioactivity, Ca release was assessed using ICP-AES. The component distribution within the cement matrix was evaluated by Feg-SEM/EPMA. Cytotoxicity was assessed using an XTT assay. Adding ZrO2 to TCS did not alter the mini-FT (p = 0.52), which remained in range of that of Biodentine (p = 0.31). Ca release from TSC cements was slightly lower than that from Biodentine at 1 day (p > 0.05). After 1 week, Ca release from TCS 30 and TCS 50 increased to a level that was significantly higher than that from Biodentine (p 0.05). EPMA revealed a more even distribution of ZrO2 within the TCS cements. Particles with an un-reacted core were surrounded by a hydration zone. The 24-, 48-, and 72-h extracts of TCS 50 were the least cytotoxic. ZrO2 can be added to TCS without affecting the mini-FT; Ca release was reduced initially, to reach a prolonged release thereafter; adding ZrO2 made TCS cements more biocompatible. TCS 50 is a promising cement formulation to serve as a biocompatible hydraulic calcium Silicate cement.
Jiang Chang - One of the best experts on this subject based on the ideXlab platform.
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Tricalcium Silicate graphene oxide bone cement with photothermal properties for tumor ablation
Journal of Materials Chemistry B, 2019Co-Authors: Jinliang Peng, Zhiguang Huan, Long Gao, Jiang ChangAbstract:Bone cements have been used in the clinical setting to fill bone defects resulting from bone tumors. However, traditional bone cements do not have the function to kill tumor cells. This study develops a new type of Tricalcium Silicate (CS) based functional bone cement with excellent photothermal performance for the minimally invasive therapy of bone defects as well as bone tumors. Graphene oxide (GO) was introduced into the CS cement by co-precipitation of CS particles with GO nanosheets to form a CS/GO composite material based on charge interactions between the CS and GO. The incorporation of GO enhanced the self-setting properties of CS and endowed the cement with excellent photothermal performance with the irradiation of near-infrared light. Besides this, the temperature of the composite cement could be regulated by adjusting the laser power and the GO content, where the rising temperature significantly inhibited the growth of subcutaneous tumor tissue in vivo. In addition, the hydration process and development of the early compressive strength of the composite cement could be modulated based on its photothermal performance. Moreover, the CS/GO composite cement retained the bioactivity of CS to promote cell proliferation and the alkaline phosphate activity of MC3T3-E1. Therefore, the CS/GO composite cement holds great promise as a new type of functional bone cement with photothermal performance for bone tumor therapy and bone defect repair.
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bioactive Tricalcium Silicate alginate composite bone cements with enhanced physicochemical properties
Journal of Biomedical Materials Research Part B, 2018Co-Authors: Xiaoya Wang, Zhiguang Huan, J Zhou, Jiang ChangAbstract:Previous studies have shown that Tricalcium Silicate bone cements possess good bioactivity and appropriate degradation rate. However, they also showed some weaknesses such as poor washout resistance, formability and injectability, which have seriously hindered their clinical applications. The purpose of this study was to develop a new type of bone cements-Tricalcium Silicate/sodium alginate (C3 S/SA) composites by utilizing the interaction of Ca ions with SA molecules, in which an interpenetrating double-network of calcium hydrate Silicate (CSH) and alginate hydrogel was formed to enhance the washout resistance, formability, injectability and compressive strength of C3 S. The results confirmed that the washout resistance, formability and injectability of C3 S could indeed be greatly enhanced by the introduction of SA. In addition, the compressive strength of the C3 S/SA composite cement with an optimum composition could reach 54 MPa, which was significantly higher than that of C3 S (i.e., 35.3 MPa). Moreover, the C3 S/SA composite cements retained the bioactivity of C3 S, such as the activity to induce apatite formation in simulated body fluid and to promote cell proliferation. All these results indicate that the C3 S/SA composite cements hold great promise as a new type of bone repair materials for further in vitro and in vivo studies. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 237-244, 2018.
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Tricalcium Silicate induces enamel remineralization in human saliva
Journal of Dental Sciences, 2013Co-Authors: Zhihong Dong, Jiang Chang, Andrew Joiner, Yuekui SunAbstract:Abstract Background/purpose Severe tooth demineralization by production of acid leads to dental caries. In this study, we investigate the repairing effect of Tricalcium Silicate (Ca 3 SiO 4 ) ceramics on acid-etched enamel in natural human saliva. Materials and methods The demineralization of enamel discs was simulated with citric acid, and they were then brushed with Ca 3 SiO 4 paste. The treated discs were placed in human saliva for 1 day or 3 days at 36.5°C, and then the surface morphologies and structures were observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Results Ca 3 SiO 4 ceramics can induce enamel remineralization in human saliva and form a compact Ca–P mineralized layer onto the etched enamel surface. After soaking for 1 day, the thickness was 200–250 nm and the interface bonded well. The chemical components and structure of the mineralized layer were similar to those of the enamel matrix. After soaking for 3 days, the surface roughness of the enamel surface became lower. Conclusion The bioactive Ca 3 SiO 4 repaired the acid-etched enamel successfully and protected the demineralized teeth.
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Tricalcium Silicate induced mineralization for occlusion of dentinal tubules.
Australian dental journal, 2011Co-Authors: Z Dong, Jiang Chang, Y Deng, Andrew JoinerAbstract:Background: The aim of this study was to evaluate the dentinal tubule occluding ability of Tricalcium Silicate (Ca3SiO5 or C3S) in vitro. Methods: Dentine discs were prepared from extracted caries-free human third molars and etched with 0.02 M citric acid (pH 4) for 3 minutes in order to produce patent dentinal tubules. Tricalcium Silicate pastes of different viscosities were applied to the surface of the dentine specimens for 3 minutes and then removed with a swab followed by deionized water rinse. The dentine specimens were immersed in artificial saliva for 7 days. The tubule occlusion, sealing depth and chemical composition of the dentine specimens and bonding force between the dentine matrix and mineralized layer were evaluated by scanning electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction analysis and a nanoscratch test. Results: A homogeneous layer of mineral crystals was precipitated onto the dentine surface and caused significant occlusion of the dentinal tubules. The dentine permeability and sealing depth of the C3S increased with the decrease of viscosity of the paste. With a proper viscosity of C3S pastes, the interface between the mineralized layer and the dentine matrix bonded well. Conclusions: This study suggests that C3S may be an effective agent for the treatment of dentine hypersensitivity.
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low temperature fabrication of macroporous scaffolds through foaming and hydration of Tricalcium Silicate paste and their bioactivity
Journal of Materials Science, 2010Co-Authors: Zhiguang Huan, Jiang Chang, J ZhouAbstract:A low-temperature fabrication method for highly porous bioactive scaffolds was developed. The two-step method involved the foaming of Tricalcium Silicate cement paste and hydration to form calcium Silicate hydrate and calcium hydroxide. Scaffolds with a combination of interconnected macro- and micro-sized pores were fabricated by making use of the decomposition of a hydrogen peroxide (H2O2) solution that acted as a foaming agent and through the hydration of Tricalcium Silicate cement. It was found possible to control the porosity and pore sizes by adjusting the concentration of the H2O2 solution. The in vitro bioactivity of the highly porous scaffolds was investigated by immersion in simulated body fluid (SBF) for 7 days. Hydroxyapatite (HAp) was formed on the surface of the scaffolds. Their bioactivity could be expected to be as good as that of Tricalcium Silicate cement, making the material competent for the bone tissue engineering application.
Jeffrey J Thomas - One of the best experts on this subject based on the ideXlab platform.
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time dependent driving forces and the kinetics of Tricalcium Silicate hydration
Cement and Concrete Research, 2015Co-Authors: Jeffrey W Bullard, George W Scherer, Jeffrey J ThomasAbstract:Abstract Simulations of Tricalcium Silicate (C 3 S) hydration using a kinetic cellular automaton program, HydratiCA, indicate that the net rate depends both on C 3 S dissolution and on hydration product growth. Neither process can be considered the sole rate-controlling step because the solution remains significantly undersaturated with respect to C 3 S yet significantly supersaturated with respect to calcium Silicate hydrate (C–S–H). The reaction rate peak is attributed to increasing coverage of C 3 S by C–S–H, which reduces both the dissolution rate and the supersaturation of C–S–H. This supersaturation dependence is included in a generalized boundary nucleation and growth model to describe the kinetics without requiring significant impingement of products on separate cement grains. The latter point explains the observation that paste hydration rates are insensitive to water/cement ratio. The simulations indicate that the product layer on C 3 S remains permeable; no transition to diffusion control is indicated, even long after the rate peak.
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hydration kinetics and microstructure development of normal and cacl2 accelerated Tricalcium Silicate pastes
Journal of Physical Chemistry C, 2009Co-Authors: Jeffrey J Thomas, Andrew J Allen, Hamlin M JenningsAbstract:Microstructure development and the kinetics of hydration of pure Tricalcium Silicate (C3S) and CaCl2-accelerated C3S pastes were investigated by performing isothermal calorimetry and in situ small-angle neutron scattering (SANS) measurements on parallel specimens during the first few days of hydration, as well as on 28-day old specimens hydrated under the same curing conditions (water/cement ratio = 0.5, 20 °C). Calorimetry experiments were also performed over a range of hydration temperatures from 10 to 40 °C. The calorimetry data were analyzed by applying a previously described boundary nucleation and growth model. The model indicates that CaCl2 significantly increases the rate of nucleation of hydration product on the surface of the C3S particles but has relatively little effect on the product growth rate. The SANS measurements indicate that the composition and density of the calcium−Silicate−hydrate (C−S−H) nanoparticles is unchanged by the addition of CaCl2. However, in the CaCl2-accelerated paste th...
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influence of nucleation seeding on the hydration mechanisms of Tricalcium Silicate and cement
Journal of Physical Chemistry C, 2009Co-Authors: Jeffrey J Thomas, Hamlin M Jennings, Jeffrey ChenAbstract:The fundamental chemical hydration process of portland cement and its main mineral component, Tricalcium Silicate, was studied by investigating the effects of various additives. A relatively small amount (1−4 wt %) of well-dispersed calcium Silicate hydrate (C−S−H), a pure form of the main hydration product, significantly increases both the early hydration rate and the total amount of hydration during the early nucleation and growth period (the first ∼24 h), as measured by calorimetry. This is attributed to a seeding effect whereby the C−S−H additive provides new nucleation sites within the pore space away from the particle surfaces. This mechanism is verified by a digital simulation of the hydration process that reproduces key features of the hydration kinetics. The results provide strong evidence that the hydration process is autocatalytic such that the C−S−H gel product stimulates its own formation. The seeding effect of C−S−H also provides a new explanation of the hydration-accelerating effects of var...
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state of water in hydrating Tricalcium Silicate and portland cement pastes as measured by quasi elastic neutron scattering
Journal of the American Ceramic Society, 2004Co-Authors: Jeffrey J Thomas, Stephen A Fitzgerald, D A Neumann, Richard A. LivingstonAbstract:Quasi-elastic neutron scattering (QENS) was used to monitor the state of water in portland cement and Tricalcium Silicate pastes during the first 2 days of hydration at three different temperatures. By applying a double-Lorentzian rather than a single-Lorentzian fitting function, the QENS signal from water at a given hydration time was divided into three separate populations arising from liquid water, chemically bound water, and constrained water. The constrained water population consisted of water adsorbed on surfaces and contained in very small (<10 nm) pores, and could be associated primarily with the calcium-Silicate-hydrate (C-S-H) phase. The rate of increase in the chemically bound water population closely followed the exothermic heat output, while the constrained water population increased more rapidly during the first several hours of hydration and then leveled off.
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a neutron scattering study of the role of diffusion in the hydration of Tricalcium Silicate
Cement and Concrete Research, 2002Co-Authors: Stephen A Fitzgerald, Jeffrey J Thomas, D A Neumann, Richard A. LivingstonAbstract:Abstract Quasi-elastic neutron scattering was used to monitor the temperature-dependant hydration of Tricalcium Silicate and Portland cement. Results show that for some samples the degree of hydration is in fact higher at lower curing temperatures. To investigate this effect further, we performed a series of experiments in which samples are initially hydrated at one temperature and then the diffusion process limiting the long-term curing is monitored at a different temperature. The results confirm that the higher the initial curing temperature the more impervious are the product layers to later diffusion. In addition, it was found that the intrinsic activation energy for this diffusion process is much greater than the traditional values obtained using samples initially cured at different temperatures.
