Sintering behaviour and mechanical properties of hydroxyapatite and dicalcium phosphate

Wang, Pauchiu E.; Chaki, T. K.

doi:10.1007/bf00120384

Cited by 236 publications

(173 citation statements)

References 19 publications

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“…The fact that decomposition of HA phase was not observed in the present material even for the high temperature (i.e. 1200 1C) sintered samples is not in agreement with the findings of Royer et al [21] and Wang et al [22] who reported that decomposition of HA starts at about 1300 1C, accompanied by deterioration of mechanical properties of HA ceramics. In general, sintering of HA can lead to the partial thermal decomposition of HA into TCP and/or TTCP [23].…”

Section: Resultscontrasting

confidence: 86%

Consolidation of nanocrystalline hydroxyapatite powder

Ramesh

Tan

Sopyan

et al. 2007

Science and Technology of Advanced Materials

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The effect of sintering temperature on the sinterability of synthesized nanocrystalline hydroxyapatite (HA) was investigated. The starting powder was synthesized via a novel wet chemical route. HA green compacts were prepared and sintered in atmospheric condition at various temperatures ranging from 900-1300 1C. The results revealed that the thermal stability of HA phase was not disrupted throughout the sintering regime employed. In general, the results showed that above 98% of theoretical density coupled with hardness of 7.21 GPa, fracture toughness of 1.17 MPa m 1/2 and Young's modulus of above 110 GPa were obtained for HA sintered at temperature as low as 1050 1C. Although the Young's modulus increased with increasing bulk density, the hardness and fracture toughness of the sintered material started to decline when the temperature was increased beyond 1000-1050 1C despite exhibiting high densities 498% of theoretical value. The occurrence of this phenomenon is believed to be associated with a thermal-activated grain growth process. r

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Section: Resultscontrasting

confidence: 86%

Consolidation of nanocrystalline hydroxyapatite powder

Ramesh

Tan

Sopyan

et al. 2007

Science and Technology of Advanced Materials

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“…All specimens were sintered at 1200°C for 90 min in air with moisture protection. 33 Measurements of density for all 10 samples of each composition showed that the resulting densities were nearly identical (HA: 91.8 Ϯ 0.4%; HAϩTCP: 91.6 Ϯ 0.4%) and similar to HA densities produced by other investigations. [27][28][29] X-ray diffraction (not shown) of the nonstoichiometric ratio revealed the expected presence of TCP.…”

Section: Methodssupporting

confidence: 71%

Microstructural disassembly of calcium phosphates

Wang

Lee

Moursi

et al. 2003

J Biomedical Materials Res

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Abstract:Microstructural factors may play a role in the osseointegration of calcium phosphates. In this paper, direct microstructural interactions between crystalline calcium phosphates and the biological milieu are reported. Degradation via exposure to osteoblast culture closely resembles in vivo interactions with subcutaneous tissues in a bovine model at early time periods. That these interactions were common to both experiments constitutes one of the few known examples of in vitro-in vivo correspondence. Interestingly, the degradation of phase pure hydroxyapatite (HA) in vitro was more rapid than that of biphasic HA in vivo. In both cases, grain extraction/pullout was frequently observed. This suggests a connection to smaller-scale observations of epitaxial CHA nucleation and growth on pre-existing HA grains. A microstructure in which the grain boundary is dissolving/corroding can apparently be disassembled by forces transmitted through biological structures. These observations are distinct from those of simple non-biological solutions and prove that biological environments can interact with the material beneath the ceramic-cell/ceramic-tissue interface. Many often ignored microstructural factorsgrain size, shape, grain boundary strength and the presence of impurity phases-may in fact control degradation. We also suggest that even relatively modest initial grain sizes will, in combination with the mild/absent foreign body response to calcium phosphates, result in lengthy in vivo particle resistence.

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“…Wang and Chaki [13] studied the sintering behavior (air, vacuum, moisture) and mechanical properties of hydroxyapatite and dicalcium phosphate. Therefore, many studies have been done on various calcium phosphate ceramics and the composition of phases can be changed with a slight variation in Ca/ P ratio as well as temperature and pH of the solution.…”

Section: Introductionmentioning

confidence: 99%