Comparison of in vivo dissolution processes in hydroxyapatite and silicon-substituted hydroxyapatite bioceramics
TL;DR: High-resolution transmission electron microscopy observations confirmed that defects, in particular those involving grain boundaries, were the starting point of dissolution in vivo and may help to explain the mechanism by which silicate ions increase the in vivo bioactivity of pure HA.
About: This article is published in Biomaterials.The article was published on 2003-11-01. It has received 391 citations till now. The article focuses on the topics: Bioceramic.
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TL;DR: This review focuses on calcium phosphate-based bone substitute materials that are used (or can be used) for teeth or bone replacement, bone repair, augmentation, or regeneration and will also include some properties of bone (e.g., interconnected porosity, biodegradability, bioactivity, osteoconductivity) that are being mimicked in the manufacture of calcium phosphates.
Abstract: This review focuses on calcium phosphate-based bone substitute materials that are used (or can be used) for teeth or bone replacement, bone repair, augmentation, or regeneration. This review will also include some properties of bone (e.g., interconnected porosity, biodegradability, bioactivity, osteoconductivity) that are being mimicked in the manufacture of calcium phosphate-based biomaterials and some of the reported factors and strategies that can make the calcium phosphate-based biomaterials acquire osteoinductive properties. Archaeological findings showed that attempts to replace missing teeth date back to the prehistoric period. The materials used then included shells, corals, ivory (from elephant tusks), metals, and human (from corpses) and animal bones. Because of the practice of cremation in many societies, not much is known about prehistoric materials used to replace bones lost to accident or disease. Presently, autografts (bones obtained from another anatomic site in the same subject) remain the gold standard for bone repair, substitution, and augmentation followed by allografts (bones from another subject, such as processed cadaver bones). Autografts and allografts while having the important advantage of being osteogenic or osteoinductive (i.e., inducing bone formation), suffer from several disadvantages. With autografts the drawbacks include additional expense and trauma to the patient, possibility of donor site morbidity, and limited availability. In the case of allografts, in addition to limited supply and high cost, potential viral transmission and immunogenicity are of serious concern. Because of the high cost and limited availability of autografts and allografts, there is a great need to develop synthetic alternative biomaterials for bone replacement, repair, and augmentation. Current commercial substitute materials to replace or repair teeth and bones include metals, polymers (natural or synthetic), corals, human bones (processed cadaver bones), animal bones (processed cow bones), corals and coral derived, synthetic ceramics (calcium phosphates, calcium sulfates, calcium carbonate, bioactive glasses), and composites. It is interesting to note that several of the materials used in prehistoric times are similar to the materials used presently (e.g., coral and coral derived, animal bone derived, metals). Generally, depending on the ability to stimulate bone tissue, materials for tooth or bone repair or replacement are classified as bioinert or bioactive. Bioinert materials do not stimulate bone formation but instead stimulate formation of fibrous tissue and therefore do not directly bond to bone and thus form a weak biomaterial-bone interface. Bioactive materials stimulate bone tissue formation and therefore directly bond with bone and thus form a uniquely strong biomaterial-bone interface. Bioinert materials include metals (e.g., titanium or titanium alloys, stainless steel, cobalt-chromium, Co-Cr, alloys), some synthetic polymers (e.g., PEEK, Teflon-type), and some ceramics (e.g., alumina, * To whom correspondence should be addressed. Phone: (212) 998-9580. Fax: (212) 995-4244. E-mail: rzl1@nyu.edu. Racquel Zapanta LeGeros received her Ph.D. degree from New York University. She is currently a Professor and Associate Chair of the Department of Biomaterials and Biomimetics at New York University College of Dentistry. Her pioneering work was on substitution in the apatite structure and effect on properties. Her research interests includes biologic and synthetic apatites and related calcium phosphates, calcium phosphatebased biomaterials in the form of granules, scaffolds, cements, and coatings, and implant surface modifications. Her current research is on the development of calcium phosphate-based biomaterial for prevention of bone loss induced by diseases (e.g., osteoporosis), therapy (e.g., radiation), condition (e.g., mineral deficiency, immobility), and recovery of bone loss. She is married to Dr. John P. LeGeros and mother of Bernard, David, Katherine, and Alessandra. Chem. Rev. 2008, 108, 4742–4753 4742
1,042 citations
TL;DR: An overview of the recent results achieved on ion-substituted calcium phosphates prepared at low temperature, i.e. by direct synthesis in aqueous medium or through hydrolysis of more soluble calcium phosphate based materials is provided.
697 citations
TL;DR: Silicon (Si) substitution in the crystal structures of calcium phosphate (CaP) ceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP) generates materials with superior biological performance to stoichiometric counterparts.
601 citations
Cites background from "Comparison of in vivo dissolution p..."
...groups such as Ti-OH or Si-OH in media [67,68,70], the specific chemistry of the surface [77], and a nano-crystalline microstructure [78]....
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TL;DR: In this paper, a review summarizes recent and very recent work on preparing substituted hydroxyapatites for a wide range of biomedical applications, including repairing and replacing diseased and damaged parts of musculoskeletal systems and also as a drug or gene delivery agent, as a bioactive coating on metallic osseous implants, biomagnetic particles and fluorescent markers.
567 citations
Cites background from "Comparison of in vivo dissolution p..."
...[154] hypothesized that the incorporation of silicate ions into HA increases its bioreactivity by increasing the number of defect structures, which are specific sites vulnerable to dissolution....
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TL;DR: The synthesis of a new generation of biomaterials that can specifically serve as tissue engineering scaffolds for drug and cell delivery is needed and nanotechnology can provide an alternative way of processing porous bioceramics with high mechanical strength and enhanced bioactivity and resorbability.
Abstract: Over the past 30 years, an enormous array of biomaterials proposed as ideal scaffolds for cell growth have emerged, yet few have demonstrated clinical efficacy. Biomaterials, regardless of whether they are permanent or biodegradable, naturally occurring or synthetic, need to be biocompatible, ideally osteoinductive, osteoconductive, integrative, porous and mechanically compatible with native bone to fulfill their desired role in bone tissue engineering. These materials provide cell anchorage sites, mechanical stability and structural guidance and in vivo, provide the interface to respond to physiologic and biologic changes as well as to remodel the extracellular matrix in order to integrate with the surrounding native tissue. Calcium phosphate ceramics and bioactive glasses were introduced more than 30 years ago as bone substitutes. These materials are considered bioactive as they bond to bone and enhance bone tissue formation. The bioactivity property has been attributed to the similarity between the surface composition and structure of bioactive materials, and the mineral phase of bone. The drawback in using bioactive glasses and calcium phosphate ceramics is that close proximity to the host bone is necessary to achieve osteoconduction. Even when this is achieved, new bone growth is often strictly limited because these materials are not osteoinductive in nature. Bone has a vast capacity for regeneration from cells with stem cell characteristics. Moreover, a number of different growth factors including bone morphogenetic proteins, have been demonstrated to stimulate bone growth, collagen synthesis and fracture repair both in vitro and in vivo. Attempts to develop a tissue-engineering scaffold with both osteoconductivity and osteoinductivity have included loading osteoinductive proteins and/or osteogenic cells on the traditional bioactive materials. Yet issues that must be considered for the effective application of bioceramics in the field of tissue engineering are the degree of bioresorption and the poor mechanical strength. The synthesis of a new generation of biomaterials that can specifically serve as tissue engineering scaffolds for drug and cell delivery is needed. Nanotechnology can provide an alternative way of processing porous bioceramics with high mechanical strength and enhanced bioactivity and resorbability.
371 citations
References
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Book•
01 Jan 1968
TL;DR: Dislocations in Isotropic Continua: Effects of Crystal Structure on Dislocations and Dislocation-Point-Defect Interactions at Finite temperatures.
Abstract: Dislocations in Isotropic Continua. Effects of Crystal Structure on Dislocations. Dislocation-Point-Defect Interactions at Finite Temperatures. Groups of Dislocations. Appendixes. Author and Subject Indexes.
10,220 citations
TL;DR: This review describes some of the current concepts regarding the surface reactivity of bone bioactive materials and its effect on attachment, proliferation, differentiation and mineralization of bone cells.
1,086 citations
"Comparison of in vivo dissolution p..." refers background in this paper
...The observed differences in ultrastructure suggest that adsorbed proteins may prevent degradation of sintered crystals, which is normally required for the formation of new phases via solution-mediated physicochemical reactions [37]....
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...At the implant–bone interface, the ceramic material is in contact with a variety of biological materials, including proteins, which adsorb onto and coat the surface of the ceramic particles [37]....
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TL;DR: Silicon, a relatively unknown trace element in nutritional research, has been uniquely localized in active calcification sites in young bone and is suggested to be associated with calcium in an early stage of calcification.
Abstract: Silicon, a relatively unknown trace element in nutritional research, has been uniquely localized in active calcification sites in young bone. Silicon increases directly with calcium at relatively low calcium concentrations and falls below the detection limit at compositions approaching hydroxyapatite. It is suggested that silicon is associated with calcium in an early stage of calcification.
867 citations
"Comparison of in vivo dissolution p..." refers background in this paper
...the active calcification sites, of normal tibiae from young mice and rats [10], suggesting that silicon plays a critical role in the bone calcification process....
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TL;DR: The dissolution behavior of the CPCs studied was found to vary over a wide range, and the dissolution rate of the monophase CPCs increased in the order of stoichiometric hydroxyapatite, calcium deficient hydroxyicarbonate, oxyhydroxyapatites, beta-tricalcium phosphate, alpha-tricals calcium phosphate, and tetracalcium phosphate.
Abstract: The formation of a biologically equivalent carbonate-containing apatite on the surface of synthetic calcium phosphate ceramics (CPC) may be an important step leading to bonding with bone. Reactions of several single phases CPCs upon immersion into a simulated physiologic solution (SPS) with an electrolyte composition of human plasma were determined. The CPCs covered a wide range of solution stabilities from low-soluble hydroxyapatites (HA) to metastable tricalcium phosphates (TCP) and tetracalcium phosphate (TTCP). Changes in chemical compositions of SPS and infrared spectral features after CPC immersion were analyzed. New phase formation was observed on all the CPCs. However, kinetics, compositions, and structures of the new phases were significantly different. The studied CPCs can be characterized by the time to new phase formation in vitro; the minimum time for measurable precipitate formation was found to increase in the order: not-well-crystallized HAs < well-crystallized HAs < alpha-TCP, TTCP < beta-TCP. Among the CPCs only not-well-crystallized HAs led to immediate new phase formation. The metastable CPCs, beta-TCP, alpha-TCP, and TTCP required an induction time during which dissolution occurred. beta-TCP showed the longest induction time and the lowest lattice ion uptake rate of all the CPCs tested. Only the not-well-crystallized HAs elicited immediate formation of carbonated HA. The well-crystallized HAs and beta-TCP did not elicit carbonated apatite formation within the time frame of the experiment. Instead, intermediate phases were formed. On alpha-TCP amorphous calcium phosphate (ACP) with a relatively low carbonate content was formed. TTCP was found to transform extensively to poorly crystallized carbonated apatite after 2 days of immersion.
655 citations
"Comparison of in vivo dissolution p..." refers background in this paper
...However, a disadvantage of using HA implants in comparison to bioactive glasses and glass ceramics is that its reactivity with existing bone is low [1] and the rate at which bone apposes and integrates with HA is relatively slow [2–4]....
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TL;DR: Chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite and demonstrated that phase-pure silicon-substituted hydroxyAPatite may be prepared using a simple precipitation technique.
Abstract: Bioceramic specimens have been prepared by incorporating a small amount of silicon (0.4 wt %) into the structure of hydroxyapatite [Ca10(PO4)6(OH)2, HA] via an aqueous precipitation reaction to produce a silicon-substituted hydroxyapatite (Si-HA). The results of chemical analysis confirmed the proposed substitution of the silicon (or silicate) ion for the phosphorus (or phosphate) ion in hydroxyapatite. The Si-HA was produced by first preparing a silicon-substituted apatite (Si-Ap) by a precipitation process. A single-phase Si-HA was obtained by heating/calcining the as-prepared Si-Ap to temperatures above 700 degrees C; no secondary phases, such as tricalcium phosphate (TCP), tetracalcium phosphate (TeCP), or calcium oxide (CaO), were observed by X-ray diffraction analysis. Although the X-ray diffraction patterns of Si-HA and stoichiometric HA appeared to be identical, refinement of the diffraction data revealed some small structural differences between the two materials. The silicon substitution in the HA lattice resulted in a small decrease in the a axis and an increase in the c axis of the unit cell. This substitution also caused a decrease in the number of hydroxyl (OH) groups in the unit cell, which was expected from the proposed substitution mechanism. The incorporation of silicon in the HA lattice resulted in an increase in the distortion of the PO4 tetrahedra, indicated by an increase in the distortion index. Analysis of the Si-HA by Fourier transform infrared (FTIR) spectroscopy indicated that although the amount of silicon incorporated into the HA lattice was small, silicon substitution appeared to affect the FTIR spectra of HA, in particular the P-O vibrational bands. The results demonstrate that phase-pure silicon-substituted hydroxyapatite may be prepared using a simple precipitation technique.
531 citations
"Comparison of in vivo dissolution p..." refers background in this paper
...Quantities of reactants were calculated by assuming that silicate would substitute for phosphate in the HA lattice [24]....
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