TEM Study of the Central Dark Line in Enamel Crystallites

Marshall, A. F.; Lawless, K. R.

doi:10.1177/00220345810600100801

Cited by 65 publications

(37 citation statements)

References 13 publications

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“…It is, however, still not clear if this phase transformation takes place through an internal structural rearrangement of the metastable phase or by dissolution/ reprecipitation. Ever since the dark line observed in the center of enamel crystals 198 was shown to be OCP phase, it has been speculated that it should be a remnant of the OCP phase composition of either the initially precipitated or the most dominant transitory phase. 199,200 Claims that the precipitated apatite is normally a solid solution rather than a double salt of OCP and HAP may speak in favor of partial or complete transition between these CAP phases in the solid state.…”

Section: Mechanism Of Formation Of Hap By Precipitationmentioning

confidence: 99%

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

2010

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The first part of this review looks at the fundamental properties of hydroxyapatite (HAP), the basic mineral constituent of mammalian hard tissues, including the physicochemical features that govern its formation by precipitation. A special emphasis is placed on the analysis of qualities of different methods of synthesis and of the phase transformations intrinsic to the formation of HAP following precipitation from aqueous solutions. This serves as an introduction to the second part and the main subject of this review, which relates to the discourse regarding the prospects of fabrication of ultrafine, nanosized particles based on calcium phosphate carriers with various therapeutic and/or diagnostic agents coated on and/or encapsulated within the particles. It is said that the particles could be either surface-functionalized with amphiphiles, peptides, proteins, or nucleic acids or injected with therapeutic agents, magnetic ions, or fluorescent molecules. Depending on the additive, they could be subsequently used for a variety of applications, including the controlled delivery and release of therapeutic agents (extracellularly or intracellularly), magnetic resonance imaging and hyperthermia therapy, cell separation, blood detoxification, peptide or oligonucleotide chromatography and ultrasensitive detection of biomolecules, and in vivo and in vitro gene transfection. Calcium phosphate nanoparticles as carriers of therapeutic agents that would enable a controlled drug release to treat a given bone infection and at the same be resorbed in the body so as to regenerate hard tissue lost to disease are emphasized hereby as one of the potentially attractive smart materials for the modern medicine.

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Section: Mechanism Of Formation Of Hap By Precipitationmentioning

confidence: 99%

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

2010

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“…Figure 4(a) shows a typical HRTEM image of mineral needles extracted from human cortical bone. The FFT analysis revealed the lattice fringes of the needles as HA with the [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] zone axis and suggested that the needle direction was parallel to the (1-100) plane of HA [ Fig. 4(b)].…”

Section: (A)]mentioning

confidence: 99%

HRTEM Study of the Mineral Phases in Human Cortical Bone

2010

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Although bone minerals have been widely studied by various techniques in previous studies, crystal structures and morphology of bone minerals remained as controversy. In this study, bone minerals were extracted from human cortical bone with ethylenediamine tetraacetic acid solution (pH 7.4, ambient temperature) and examined by high‐resolution transmission electron microscopy. The results showed that the majority of bone minerals were flake‐like and a few were needle‐like. Most of flake‐like minerals were less than 100 nm in their largest dimension and the needle‐like minerals have a width of ∼10 nm. Hydroxyapatite structure was identified in relatively thick bone minerals. However, octacalcium phosphate structure was identified in relatively thin flake‐like bone minerals. Moreover, central dark line defect similar to that reported in dentin and enamel crystals was observed in some of needle‐like bone minerals.

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“…Generally, hard tissue-forming cells-such as ameloblasts, odontoblasts and osteoblasts-are responsible for the development of various sized apatite crystals suited to different hard tissues (e.g., large crystals in enamel and small crystals in dentin and bone). In addition, the process of crystal formation under normal conditions is strictly regulated by cellular activities that either produce crystals with CDLs in various hard tissues [23][24][25][26][27][28] or without CDLs in the tooth enamel of fish and tooth apparatus of conodonts 29,30) .…”

Section: Discussionmentioning

confidence: 99%

“…According to our recent findings, apatite crystals can be crystallographically divided into 2 types: (1) crystals with central dark lines (CDLs), formed in normal calcified hard tissues of vertebrates [23][24][25][26][27][28] , and (2) crystals without CDLs, formed, for example, in the tooth enamel of fish and tooth apparatus of conodonts 29,30) . Hard tissue-forming cells thus either produce crystals with CDLs or without CDLs.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructure of Apatite Crystals Formed During Vascular Calcification in Humans

Kakei

Tanaka

Mishima

et al. 2009

J. Hard Tissue Biology.

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:Using a transmission electron microscope, we compared the ultrastructure of apatite crystals of normal calcified hard tissue to that of apatite crystals created under pathological conditions. We also sought to verify whether the process of calcification resembles that of osteogenesis after the phenotypic change of soft tissue cells into hard tissue-forming cells. Electron micrographs clearly revealed that cellular debris, plausibly originating from degenerated immune cells like macrophages as well as perivascular cells in intima of femoral artery lesions, seemed to serve in the formation of an organic envelope. This indicates that crystal formation is accompanied by the death of cells. Judging from the lattice image, we also found that the calcified deposits consisted of 2 distinct types of apatite crystals. One type has central dark lines, while the other does not have lines. In addition, the crystals were of various sizes and some showed lattice defects. From these findings, we concluded that ectopic calcification occurred in a manner different from the calcification of normal hard tissues, suggesting that cellular phenotypic change may not happen in vivo.

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TEM Study of the Central Dark Line in Enamel Crystallites

Cited by 65 publications

References 13 publications

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

Nanosized hydroxyapatite and other calcium phosphates: Chemistry of formation and application as drug and gene delivery agents

HRTEM Study of the Mineral Phases in Human Cortical Bone

Ultrastructure of Apatite Crystals Formed During Vascular Calcification in Humans

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