In vitro behavior of HVOF sprayed calcium phosphate splats and coatings

In vitro behavior of HVOF sprayed calcium phosphate splats and coatings

Hydroxyapatite (HA) coatings and splats deposited by high velocity oxy-fuel (HVOF) spray technique was investigated in vitro. HA coatings prepared from two different HA powder size range (30±5 and 50±5 μm ) were immersed in a simulated body fluid with various incubation periods of maximum 6 weeks. T...

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Bibliographic Details
Published in:Biomaterials Vol. 24; no. 5; pp. 723 - 735
Main Authors: Khor, K.A., Li, H., Cheang, P., Boey, S.Y.
Format: Journal Article
Language:English
Published: Netherlands Elsevier Ltd 01-02-2003
Subjects:
Anions
Biocompatible Materials
Biodegradation, Environmental
Body Fluids
Calcium Phosphates
Cations
Dissolution
Durapatite - pharmacokinetics
Humans
Hydroxyapatite
In vitro
Models, Biological
Precipitation
Solubility
Splats
Stress, Mechanical
Surface Properties
Thermal spray
Precipitation
Hydroxyapatite
In vitro
Dissolution
Thermal spray
Splats
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Summary:Hydroxyapatite (HA) coatings and splats deposited by high velocity oxy-fuel (HVOF) spray technique was investigated in vitro. HA coatings prepared from two different HA powder size range (30±5 and 50±5 μm ) were immersed in a simulated body fluid with various incubation periods of maximum 6 weeks. The dissolution/precipitation behavior was studied and the degradation of HA coatings caused by in vitro ageing was demonstrated by measuring the changes in flexural modulus through a 3-point bend test. It was found that the dissolution and precipitation behavior of the coatings was significantly dependent upon the incipient coating phase composition and the precipitation of bone-like hydroxyapatite on the coating's surface was found to be directly related to the dissolution process. Higher dissolution rates of tricalcium phosphate, tetracalcium phosphate and amorphous calcium phosphate relative to HA, resulted in accelerated precipitation. Furthermore, analysis of coatings’ surface morphology demonstrated that advanced precipitation invariably occurred at regions where dissolution took place. Results showed that the changes in flexural modulus of investigated HA coatings accompanying different incubation duration was not systematic but was found to be dependent upon changes of coating structure and other factors brought about by in vitro ageing. In vitro investigation of individual HA splats collected from different HA particle sizes revealed, after 3 days ageing, that the rate ratio of precipitation to dissolution was directly determined by the local phase composition, and this phenomenon could be effectively used to explain the behavior of thermally sprayed HA coatings in vitro. It implied that the precipitation was strongly dependent on the first molecule attachment. To achieve rapid precipitation in vitro, partial molten state of HA particles during HVOF coating deposition was recommended.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
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content type line 23
ISSN:0142-9612
1878-5905
DOI:10.1016/S0142-9612(02)00404-0