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Roland J M Pellenq - One of the best experts on this subject based on the ideXlab platform.
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fracture toughness of Calcium Silicate hydrate from molecular dynamics simulations
Journal of Non-crystalline Solids, 2015Co-Authors: Mathieu Bauchy, Roland J M Pellenq, Franzjosef Ulm, M Abdolhosseini J Qomi, Hadrien Laubie, Christian G HooverAbstract:Abstract Concrete is the most widely manufactured material in the world. Its binding phase, Calcium–Silicate–hydrate (C–S–H), is responsible for its mechanical properties and has an atomic structure fairly similar to that of usual Calcium Silicate glasses, which makes it appealing to study this material with tools and theories traditionally used for non-crystalline solids. Here, following this idea, we use molecular dynamics simulations to evaluate the fracture toughness of C–S–H, inaccessible experimentally. This allows us to discuss the brittleness of the material at the atomic scale. We show that, at this scale, C–S–H breaks in a ductile way, which prevents one from using methods based on linear elastic fracture mechanics. Knowledge of the fracture properties of C–S–H at the atomic scale opens the way for an upscaling approach to the design of tougher cement paste, which would allow for the design of slender environment-friendly infrastructures, requiring less material.
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order and disorder in Calcium Silicate hydrate
Other univ. web domain, 2014Co-Authors: Mathieu Bauchy, Franzjosef Ulm, M Abdolhosseini J Qomi, Roland J M PellenqAbstract:Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium–Silicate–Hydrate (C–S–H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C–S–H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C–S–H, and compared the latter to crystalline tobermorite, a natural analogue of C–S–H, and to an artificial ideal glass. The results clearly indicate that C–S–H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C–S–H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous.
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understanding and controlling the reactivity of the Calcium Silicate phases from first principles
Chemistry of Materials, 2012Co-Authors: Engin Durgun, Roland J M Pellenq, Hegoi Manzano, Jeffrey C GrossmanAbstract:First principles calculations are employed to provide a fundamental understanding of the relationship between the reactivity of synthetic Calcium Silicate phases and their electronic structure. Our aim is to shed light on the wide range of hydration kinetics observed in different phases of Calcium Silicate. For example, while the diCalcium Silicate (Ca2SiO4) phase slowly reacts with water, the triCalcium Silicate (Ca3SiO5) shows much faster hydration kinetics. We show that the high reactivity of Ca3SiO5 is mainly related to the reactive sites around its more ionic oxygen atoms. Ca2SiO4 does not contain these types of oxygen atoms, although experiments suggest that impurities may play a role in changing the reactivity of these materials. We analyze the electronic structure of a wide range of possible substitutions in both Ca3SiO5 and Ca2SiO4 and show that while the influence of different types of impurities on structural properties is similar, their effect on reactivity is very different. Our calculations ...
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evidence on the dual nature of aluminum in the Calcium Silicate hydrates based on atomistic simulations
Journal of the American Ceramic Society, 2012Co-Authors: M Abdolhosseini J Qomi, Roland J M PellenqAbstract:Hydration of tri-Calcium Silicate (C3S) and di-Calcium Silicate (C2S) precipitates Calcium-Silicate-hydrate (CSH) which is the bonding phase responsible for the strength of cementitious materials. Substitution of part of C3S and C2S with aluminum-containing additives alters the chemical composition of hydration products by precipitating Calcium-aluminate-Silicate-hydrate (CASH). Incorporation of aluminum in the molecular building blocks of CSH entails structural and chemo-mechanical consequences. These alterations can be measured through solid state nuclear magnetic resonance (NMR) experiments. By conducting a wide spectrum of atomistic simulation methods on thousands of aluminum-containing molecular CASH structures, an overall molecular approach for determination of CASH nanostructure is presented. Through detailed analysis of different order parameters, it is found that aluminum can exhibit a tetra-/penta-/octahedral behavior which is fully consistent with the recent NMR observations. This corresponds to the formation of a class of complex three-dimensional alumino-Silicate skeletons with partial healing effect in the CASH nanostructure potentially increasing durability and strength of hydration products. We explored the variation of mechanical observables by increasing aluminum content in CASH structures of varying Calcium to silicon ratio. Finally, deformation of CSHs and CASHs of different chemical formula in a multi-scale fashion unravels the effect of chemical composition on the strength and kinematics of deformation in this particular type of composites.
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glassy nature of water in an ultraconfining disordered material the case of Calcium Silicate hydrate
Journal of the American Chemical Society, 2011Co-Authors: Mostafa Youssef, Roland J M Pellenq, Bilge YildizAbstract:We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly disordered Calcium−Silicate−hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the disordered Silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the Calcium−Silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 A, a disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 A, and persisting spatial correlations through dipole−dipole interactions up to 10 A. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteri...
Maria Giovanna Gandolfi - One of the best experts on this subject based on the ideXlab platform.
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Calcium Silicate bioactive cements biological perspectives and clinical applications
Dental Materials, 2015Co-Authors: Carlo Prati, Maria Giovanna GandolfiAbstract:Abstract Objective To introduce and to examine the research progress and the investigation on hydraulic Calcium Silicate cements (HCSCs), well-known as MTA (mineral trioxide aggregate). Methods This review paper introduces the most important investigations of the last 20 years and analyze their impact on HCSCs use in clinical application. Results HCSCs were developed more than 20 years ago. Their composition is largely based on Portland cement components (di- and tri-Calcium Silicate, Al- and Fe-Silicate). They have important properties such as the ability to set and to seal in moist and blood-contaminated environments, biocompatibility, adequate mechanical properties, etc. Their principal limitations are long setting time, low radiopacity and difficult handling. New HCSCs-based materials containing additional components (setting modulators, radiopacifying agents, drugs, etc. ) have since been introduced and have received a considerable attention from laboratory researchers for their biological and translational characteristics and from clinicians for their innovative properties. HCSCs upregulate the differentiation of osteoblast, fibroblasts, cementoblasts, odontoblasts, pulp cells and many stem cells. They can induce the chemical formation of a Calcium phosphate/apatite coating when immersed in biological fluids. These properties have led to a growing series of innovative clinical applications such as root-end filling, pulp capping and scaffolds for pulp regeneration, root canal sealer, etc. The capacity of HCSCs to promote Calcium-phosphate deposit suggests their use for dentin remineralization and tissue regeneration. Several in vitro studies, animal tests and clinical studies confirmed their ability to nucleate apatite and remineralize and to induce the formation of (new) mineralized tissues. Significance HCSCs play a critical role in developing a new approach for pulp and bone regeneration, dentin remineralization, and bone/cementum tissue healing. Investigations of the next generation HCSCs for “Regenerative Dentistry” will guide their clinical evolution.
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Calcium Silicate Calcium phosphate biphasic cements for vital pulp therapy chemical physical properties and human pulp cells response
Clinical Oral Investigations, 2015Co-Authors: Maria Giovanna Gandolfi, Carlo Prati, Francesco Siboni, Gianrico Spagnuolo, Alfredo Procino, Virginia Rivieccio, Gian Andrea Pelliccioni, S RengoAbstract:Objectives The aim was to test the properties of experimental Calcium Silicate/Calcium phosphate biphasic cements with hydraulic properties designed for vital pulp therapy as direct pulp cap and pulpotomy.
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Calcium Silicate and Calcium hydroxide materials for pulp capping biointeractivity porosity solubility and bioactivity of current formulations
Journal of Applied Biomaterials & Functional Materials, 2015Co-Authors: Maria Giovanna Gandolfi, Francesco Siboni, Tatiana M Otero, Maurizio Ossu, Francesco Riccitiello, Carlo PratiAbstract:AimThe chemical-physical properties of novel and long-standing Calcium Silicate cements versus conventional pulp capping Calcium hydroxide biomaterials were compared.MethodsCalcium hydroxide–based ...
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Calcium Silicate bioactive cements: Biologicalperspectives and clinical applications
2015Co-Authors: Carlo Prati, Maria Giovanna GandolfiAbstract:tObjective. To introduce and to examine the research progress and the investigation onhydraulic Calcium Silicate cements (HCSCs), well-known as MTA (mineral trioxide aggregate).Methods. This review paper introduces the most important investigations of the last 20 yearsand analyze their impact on HCSCs use in clinical application.Results. HCSCs were developed more than 20 years ago. Their composition is largely basedon Portland cement components (di- and tri-Calcium Silicate, Al- and Fe-Silicate). They haveimportant properties such as the ability to set and to seal in moist and blood-contaminatedenvironments, biocompatibility, adequate mechanical properties, etc. Their principal limi-tations are long setting time, low radiopacity and difficult handling.New HCSCs-based materials containing additional components (setting modulators,radiopacifying agents, drugs, etc.) have since been introduced and have received a con-siderable attention from laboratory researchers for their biological and translationalcharacteristics and from clinicians for their innovative properties.HCSCs upregulate the differentiation of osteoblast, fibroblasts, cementoblasts, odonto-blasts, pulp cells and many stem cells. They can induce the chemical formation of a Calciumphosphate/apatite coating when immersed in biological fluids.These properties have led to a growing series of innovative clinical applications such asroot-end filling, pulp capping and scaffolds for pulp regeneration, root canal sealer, etc.The capacity of HCSCs to promote Calcium-phosphate deposit suggests their use for dentinremineralization and tissue regeneration. Several in vitro studies, animal tests and clini-cal studies confirmed their ability to nucleate apatite and remineralize and to induce theformation of (new) mineralized tissues.Significance. HCSCs play a critical role in developing a new approach for pulp and bone regen-eration, dentin remineralization, and bone/cementum tissue healing. Investigations of thenext generation HCSCs for “Regenerative Dentistry” will guide their clinical evolution
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alpha tcp improves the apatite formation ability of Calcium Silicate hydraulic cement soaked in phosphate solutions
Materials Science and Engineering: C, 2011Co-Authors: Maria Giovanna Gandolfi, Paola Taddei, Anna Tinti, E Dorigo, Carlo PratiAbstract:Abstract The in vitro apatite-forming ability of experimental Calcium-Silicate hydraulic cements designed for dentistry was investigated. Two cements containing di- and triCalcium-Silicate (wTC and wTC-TCP, i.e. wTC added with alpha-TCP) were soaked in different phosphate-containing solutions, namely Dulbecco's Phosphate Buffered Saline (DPBS) or Hank's Balanced Salt Solution (HBSS), at 37 °C and investigated over time (from 24 h to 6 months) by SEM/EDX, micro-Raman and ATR-FTIR. The early formation (24 h) of an aragonite/calcite layer onto both cements in both media was observed. Calcium phosphate deposits precipitated within 1–3 days in DPBS; spherical particles (spherulites) of apatite appeared after 3–7 days. wTC-TCP cement showed earlier, thicker and more homogeneous Calcium phosphate deposits than wTC. In HBSS calcite deposits were mainly noticed, while phosphate bands appeared only after 7 days; the presence of globular deposits after 14–28 days was mostly detected on wTC-TCP. After 6 months, an approx. 900 micron carbonated apatite layer formed in DPBS whilst a 150–350 micron thick calcite/apatite layer generated in HBSS. Also in HBSS the carbonated apatite coating was earlier and thicker on wTC-TCP than wTC. Calcium-Silicate cements showed the formation of a bone-like apatite layer, depending on the medium composition and ageing time. The addition of alpha-TCP increases the apatite-forming ability of Calcium-Silicate cements. Calcium-Silicate hydraulic cements doped with alfa-TCP represent attractive materials to improve apical bone healing.
Wei Guan - One of the best experts on this subject based on the ideXlab platform.
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fluoride recovery using porous Calcium Silicate hydrates via spontaneous ca2 and oh release
Separation and Purification Technology, 2016Co-Authors: Wei Guan, Xu ZhaoAbstract:Abstract In the present study, porous Calcium Silicate hydrates (P-CSH) was prepared from CaO and soluble sodium Silicate via a hydrothermal method and used for fluoride ions recovery. In comparison with the crystalline Calcium Silicate hydrates (C-CSH), P-CSH, which has large specific surface areas of 148.11 m2/g, a high Ca/Si molar ratio of 2.28 and low crystallinity, exhibited a high capacity for fluoride recovery from synthetic and practical electroplating wastewater. Fluoride recovery by P-CSH continued spontaneously at pH range of 6.4–7.4 without an extra pH adjustment. The fast Ca2+ dissolution rate of P-CSH was favorable for the fluoride precipitation with free Ca2+. Compared with the C-CSH, P-CSH exhibited massive Ca OH linkages, which enhanced the fluoride removal capacity by forming insoluble CaF2. Based on the analysis of the P-CSH samples before and after fluoride recovery by SEM, XRD, FTIR techniques, it was concluded that the surface Ca OH was active sites and the quantitative substitution of Ca OH groups by F− played a key role in F− ion exchange. The fluoride recovery efficiency of P-CSH is 79.6%. The present study demonstrated a good potential of P-CSH for the fluoride recovery.
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preparation and phosphorus recovery performance of porous Calcium Silicate hydrate
Ceramics International, 2013Co-Authors: Wei Guan, Qingkong Chen, Peng Yan, Qian ZhangAbstract:Abstract Porous Calcium–Silicate–hydrate was synthesized and used to recover phosphorus from wastewater. The principal objective of this study was to explore the phosphorus recovery performance of porous Calcium–Silicate–hydrate prepared by different Ca/Si molar ratios. Phosphorus recovery mechanism was also investigated via Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectrum (EDS), Brunauer–Emmett–Teller (BET) and X-ray Diffraction (XRD). The law of Ca 2+ release was the key of phosphorus recovery performance. Different Ca/Si molar ratios resulted in the changes of pore structures. The increase of specific surface area and the increase in concentration of Ca 2+ release were well agreement together. The Ca/Si molar ratio of 1.6 for porous Calcium–Silicate–hydrate is more proper to recover phosphorus. The pore structure of porous Calcium–Silicate–hydrate provided a local condition to maintain a high concentration of Ca 2+ release. Porous Calcium–Silicate–hydrate could release a proper concentration of Ca 2+ and OH − to maintain the pH values at 8.5–9.5. This condition was beneficial to the formation of hydroxyapatite. Phosphorus content of porous Calcium–Silicate–hydrate reached 18.64% after phosphorus recovery.
Paulo J.m. Monteiro - One of the best experts on this subject based on the ideXlab platform.
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structure and intrinsic mechanical properties of nanocrystalline Calcium Silicate hydrate
ACS Sustainable Chemistry & Engineering, 2020Co-Authors: Wenxin Zhang, Paulo J.m. MonteiroAbstract:Nanocrystalline Calcium Silicate hydrate (C–S–H) is the binding phase of many low-CO2 cements. Understanding its structure–mechanical properties relationship is critical in designing sustainable co...
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nanostructure of Calcium Silicate hydrates in cements
Physical Review Letters, 2010Co-Authors: Lawrie Skinner, S Chae, C J Benmore, H R Wenk, Paulo J.m. MonteiroAbstract:Calcium Silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated triCalcium Silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure.
Carlo Prati - One of the best experts on this subject based on the ideXlab platform.
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Calcium Silicate bioactive cements biological perspectives and clinical applications
Dental Materials, 2015Co-Authors: Carlo Prati, Maria Giovanna GandolfiAbstract:Abstract Objective To introduce and to examine the research progress and the investigation on hydraulic Calcium Silicate cements (HCSCs), well-known as MTA (mineral trioxide aggregate). Methods This review paper introduces the most important investigations of the last 20 years and analyze their impact on HCSCs use in clinical application. Results HCSCs were developed more than 20 years ago. Their composition is largely based on Portland cement components (di- and tri-Calcium Silicate, Al- and Fe-Silicate). They have important properties such as the ability to set and to seal in moist and blood-contaminated environments, biocompatibility, adequate mechanical properties, etc. Their principal limitations are long setting time, low radiopacity and difficult handling. New HCSCs-based materials containing additional components (setting modulators, radiopacifying agents, drugs, etc. ) have since been introduced and have received a considerable attention from laboratory researchers for their biological and translational characteristics and from clinicians for their innovative properties. HCSCs upregulate the differentiation of osteoblast, fibroblasts, cementoblasts, odontoblasts, pulp cells and many stem cells. They can induce the chemical formation of a Calcium phosphate/apatite coating when immersed in biological fluids. These properties have led to a growing series of innovative clinical applications such as root-end filling, pulp capping and scaffolds for pulp regeneration, root canal sealer, etc. The capacity of HCSCs to promote Calcium-phosphate deposit suggests their use for dentin remineralization and tissue regeneration. Several in vitro studies, animal tests and clinical studies confirmed their ability to nucleate apatite and remineralize and to induce the formation of (new) mineralized tissues. Significance HCSCs play a critical role in developing a new approach for pulp and bone regeneration, dentin remineralization, and bone/cementum tissue healing. Investigations of the next generation HCSCs for “Regenerative Dentistry” will guide their clinical evolution.
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Calcium Silicate Calcium phosphate biphasic cements for vital pulp therapy chemical physical properties and human pulp cells response
Clinical Oral Investigations, 2015Co-Authors: Maria Giovanna Gandolfi, Carlo Prati, Francesco Siboni, Gianrico Spagnuolo, Alfredo Procino, Virginia Rivieccio, Gian Andrea Pelliccioni, S RengoAbstract:Objectives The aim was to test the properties of experimental Calcium Silicate/Calcium phosphate biphasic cements with hydraulic properties designed for vital pulp therapy as direct pulp cap and pulpotomy.
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Calcium Silicate and Calcium hydroxide materials for pulp capping biointeractivity porosity solubility and bioactivity of current formulations
Journal of Applied Biomaterials & Functional Materials, 2015Co-Authors: Maria Giovanna Gandolfi, Francesco Siboni, Tatiana M Otero, Maurizio Ossu, Francesco Riccitiello, Carlo PratiAbstract:AimThe chemical-physical properties of novel and long-standing Calcium Silicate cements versus conventional pulp capping Calcium hydroxide biomaterials were compared.MethodsCalcium hydroxide–based ...
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Calcium Silicate bioactive cements: Biologicalperspectives and clinical applications
2015Co-Authors: Carlo Prati, Maria Giovanna GandolfiAbstract:tObjective. To introduce and to examine the research progress and the investigation onhydraulic Calcium Silicate cements (HCSCs), well-known as MTA (mineral trioxide aggregate).Methods. This review paper introduces the most important investigations of the last 20 yearsand analyze their impact on HCSCs use in clinical application.Results. HCSCs were developed more than 20 years ago. Their composition is largely basedon Portland cement components (di- and tri-Calcium Silicate, Al- and Fe-Silicate). They haveimportant properties such as the ability to set and to seal in moist and blood-contaminatedenvironments, biocompatibility, adequate mechanical properties, etc. Their principal limi-tations are long setting time, low radiopacity and difficult handling.New HCSCs-based materials containing additional components (setting modulators,radiopacifying agents, drugs, etc.) have since been introduced and have received a con-siderable attention from laboratory researchers for their biological and translationalcharacteristics and from clinicians for their innovative properties.HCSCs upregulate the differentiation of osteoblast, fibroblasts, cementoblasts, odonto-blasts, pulp cells and many stem cells. They can induce the chemical formation of a Calciumphosphate/apatite coating when immersed in biological fluids.These properties have led to a growing series of innovative clinical applications such asroot-end filling, pulp capping and scaffolds for pulp regeneration, root canal sealer, etc.The capacity of HCSCs to promote Calcium-phosphate deposit suggests their use for dentinremineralization and tissue regeneration. Several in vitro studies, animal tests and clini-cal studies confirmed their ability to nucleate apatite and remineralize and to induce theformation of (new) mineralized tissues.Significance. HCSCs play a critical role in developing a new approach for pulp and bone regen-eration, dentin remineralization, and bone/cementum tissue healing. Investigations of thenext generation HCSCs for “Regenerative Dentistry” will guide their clinical evolution
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alpha tcp improves the apatite formation ability of Calcium Silicate hydraulic cement soaked in phosphate solutions
Materials Science and Engineering: C, 2011Co-Authors: Maria Giovanna Gandolfi, Paola Taddei, Anna Tinti, E Dorigo, Carlo PratiAbstract:Abstract The in vitro apatite-forming ability of experimental Calcium-Silicate hydraulic cements designed for dentistry was investigated. Two cements containing di- and triCalcium-Silicate (wTC and wTC-TCP, i.e. wTC added with alpha-TCP) were soaked in different phosphate-containing solutions, namely Dulbecco's Phosphate Buffered Saline (DPBS) or Hank's Balanced Salt Solution (HBSS), at 37 °C and investigated over time (from 24 h to 6 months) by SEM/EDX, micro-Raman and ATR-FTIR. The early formation (24 h) of an aragonite/calcite layer onto both cements in both media was observed. Calcium phosphate deposits precipitated within 1–3 days in DPBS; spherical particles (spherulites) of apatite appeared after 3–7 days. wTC-TCP cement showed earlier, thicker and more homogeneous Calcium phosphate deposits than wTC. In HBSS calcite deposits were mainly noticed, while phosphate bands appeared only after 7 days; the presence of globular deposits after 14–28 days was mostly detected on wTC-TCP. After 6 months, an approx. 900 micron carbonated apatite layer formed in DPBS whilst a 150–350 micron thick calcite/apatite layer generated in HBSS. Also in HBSS the carbonated apatite coating was earlier and thicker on wTC-TCP than wTC. Calcium-Silicate cements showed the formation of a bone-like apatite layer, depending on the medium composition and ageing time. The addition of alpha-TCP increases the apatite-forming ability of Calcium-Silicate cements. Calcium-Silicate hydraulic cements doped with alfa-TCP represent attractive materials to improve apical bone healing.
