Influence of process conditions on hydroxyapatite crystallinity obtained by direct crystallization

Seckler, Marcelo Martins; Danese, M.; Derenzo, Silas; Valarelli, José Vicente; Giulietti, Marco; Rodrı́guez-Clemente, R.

doi:10.1590/s1516-14391999000200003

Cited by 40 publications

(32 citation statements)

References 5 publications

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“…This shows that the crystallinity degree reaches a maximum around 88.79% after heating of the 10-h milled sample and after that goes down gradually to 84.02% after annealing of the 15-h milled specimen. Since apatite with high crystallinity degree shows little or no activity towards bioresorption and are insoluble in physiological environment [35], the annealed samples with high crystallinity degree are well preferred for dental applications. In a nutshell, the obtained data indicate that, similar to the other structural features (i.e., crystallite size, micro-strain and the volume fraction of grain boundary), the crystallinity degree of mechano-synthesized bioceramics is effectively influenced by the milling time and subsequent annealing.…”

Section: Crystallinity Degreementioning

confidence: 99%

Thermal treatment effect on structural features of mechano-synthesized fluorapatite-titania nanocomposite: A comparative study

Nasiri–Tabrizi

2014

J Adv Ceram

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Abstract:The influence of thermal treatment on the structural features of mechano-synthesized fluorapatite-titania composite nanopowders was studied. A mixture of calcium and phosphate reagents was mixed with a certain amount of titania (20 wt%) and then was mechanically activated for 5 h, 10 h and 15 h respectively. After that, the mechano-synthesized powders were annealed at 700 ℃ for 2 h. The crystallite size of the composite nanopowders estimated from Williamson-Hall method was in good agreement with transmission electron microscopy (TEM) analysis. Scanning electron microscopy (SEM)/TEM images confirmed the formation of a cluster-like composite which was composed of ellipse-like nanoparticles with an average size of about 16±7 nm after 15 h of milling. During the milling process, large variations in mechanochemical behavior of the CaHPO 4 -Ca(OH) 2 -CaF 2 -TiO 2 system were detected. After the beginning of milling, no trace of the composite was found due to the lack of sufficient time for the mechanical activation. When the mechanical activation time increased to 15 h, composite nanopowders with the crystallite size of around 21.66 nm were formed. During heating at 700 ℃, the recovery of crystallinity occurred and the fraction of crystalline phase reached a maximum around 88.79% for the 10-h milled sample. Results indicated that the structural features of the composite were strongly influenced by the subsequent annealing.

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Section: Crystallinity Degreementioning

confidence: 99%

Thermal treatment effect on structural features of mechano-synthesized fluorapatite-titania nanocomposite: A comparative study

Nasiri–Tabrizi

2014

J Adv Ceram

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“…It has been found that apatites with high crystallinity degree show little or no activity towards bioresorption and are insoluble in physiological environment [25]. This suggests that control of the crystallinity degree of bioceramics is necessary for their biological applications.…”

Section: Introductionmentioning

confidence: 99%

Crystallinity Evaluation of Cluster-Like Fluorapatite–Titania Nanocomposites

Fahami

2013

J Clust Sci

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The influence of mechanical activation time on mechanochemical behavior of the CaHPO 4 -Ca(OH) 2 -CaF 2 -TiO 2 system was investigated. Results showed that a fluorapatite-titania (FAp-TiO 2 ) composite nanopowder with high phase purity was obtained after 15 h of milling. Detailed study of microstructure by transmission electron microscopy confirmed the formation of the cluster-like composite nanopowders. This structure was composed of ellipsoidal nanoparticles with an average diameter of 16 ± 7 nm after 15 h of milling. Unit cell measurements indicated that the a-axis and caxis values of FAp in the composite structures were similar to the reported values for the standard. After 5 h of milling, the crystallite size and lattice strain were about 23.11 nm and 0.64 %, respectively. With increasing the milling time to 15 h, the lattice strain increased to about 0.70 %, while the crystalline size declined to around 21.66 nm. Based on the obtained data, the fraction of crystalline phase (crystallinity degree) was strongly influenced by the milling time. Accordingly, the crystallinity degree of the composite nanopowder reached a maximum about 38.32 % after 15 h of milling. According to the FT-IR and EDX results, the 15 h milled sample had high chemical purity.

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“…Dental calculus on teeth consists mainly of four different calcium phosphate 4 phases: hydroxyapatite [Ca 10 (PO 4 ) 6 , etc. ), which introduces changes in the unit cell dimensions.…”

Section: Introductionmentioning

confidence: 99%

“…unc.edu.ar and the local pH, which are important factors for crystallinity in biomaterial products resembling bones. 6 Early calculus deposits require a long time of maturation (about 1 year) to become a more crystalline phase. Schroeder and Bambauer, 7 using X-ray diffraction, found brushite in initial stages (a few weeks) of calculus maturation and whitlockite and hydroxyapatite in old deposits (almost 1 year), while octacalcium phosphate (OCP) was present in all stages.…”

Section: Introductionmentioning

confidence: 99%

A case study of elemental and structural composition of dental calculus during several stages of maturation using SRXRF

Abraham

Grenón

Sánchez

et al. 2005

J Biomedical Materials Res

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This work presents a study of elemental composition and preponderant structure of human dental calculus, as they mature in the mouth for a period of 1 year. The synchrotron radiation X-ray fluorescence technique using a white beam was employed as an analytical method. The set of samples were extracted from different dental elements of the same subject, who did not require any other clinical care. By means of analyzing the Ca/P molar ratio an estimation of the main crystallographic structure was attained, by simple comparison with stoichiometric values of the several crystalline structures that compose the calculus. The results showed a slowly progressive transformation of the initial crystalline structures (brushite) into more stable structures (hydroxyapatite), passing through octacalcium phosphate and whitlockite. The concentrations of mayor components (Ca and P) as a function of time followed a sigmoid curve. The analysis of trace element concentrations versus time indicated a null or small correlation of concentration values with the kinetics of the crystallization process.

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Influence of process conditions on hydroxyapatite crystallinity obtained by direct crystallization

Cited by 40 publications

References 5 publications

Thermal treatment effect on structural features of mechano-synthesized fluorapatite-titania nanocomposite: A comparative study

Thermal treatment effect on structural features of mechano-synthesized fluorapatite-titania nanocomposite: A comparative study

Crystallinity Evaluation of Cluster-Like Fluorapatite–Titania Nanocomposites

A case study of elemental and structural composition of dental calculus during several stages of maturation using SRXRF

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