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Dual constant composition kinetics characterization of apatitic surfaces
E P Paschalis1, K Wikiel, G H Nancollas
1Department of Chemistry, State University of New York at Buffalo 14260.
Journal of Biomedical Materials Research
|December 1, 1994
Summary
Calcium phosphate implant materials like ceramic hydroxyapatite (CHAP) and hydroxyapatite plasma-coated implants (HPCTI) contain reactive impurities. These impurities influence initial reactions and dissolution kinetics, impacting in vivo performance.
Area of Science:
- Biomaterials Science
- Materials Chemistry
- Surface Chemistry
Background:
- Calcium phosphate phases, including ceramic hydroxyapatite (CHAP) and hydroxyapatite plasma-coated implants (HPCTI), are established implant materials.
- Conventional characterization may not reveal all reactive surface components, despite X-ray diffraction indicating hydroxyapatite (HAP) presence.
- Surface impurities on these materials can significantly affect initial interactions with aqueous environments.
Purpose of the Study:
- To investigate the dissolution kinetics of CHAP and HPCTI using the dual constant composition (DCC) approach.
- To characterize and potentially modify the surfaces of these calcium phosphate implant materials.
- To predict the in vivo behavior of CHAP and HPCTI based on their surface properties and dissolution characteristics.
Main Methods:
- Utilized the dual constant composition (DCC) method, an advancement of the constant composition (CC) technique.
- Studied the dissolution kinetics of ceramic hydroxyapatite (CHAP) and hydroxyapatite plasma-coated implants (HPCTI).
- Analyzed the release of calcium and hydroxyl ions in saline solutions to identify reactive surface phases.
Main Results:
- Confirmed the presence of highly reactive, heterogeneous calcium-containing phases on CHAP and HPCTI surfaces.
- Observed significant release of calcium and hydroxyl ions upon contact with saline solutions, indicating rapid dissolution of impurities.
- Demonstrated unique dissolution behavior for these materials compared to synthetic hydroxyapatite (HAP) and beta-tricalcium phosphate (beta-TCP), dissolving even in HAP-supersaturated solutions.
Conclusions:
- The surfaces of CHAP and HPCTI contain reactive impurities that play a crucial role in their initial interactions in aqueous environments.
- The DCC method effectively characterizes these heterogeneous phases and their dissolution kinetics.
- Understanding these surface properties is essential for predicting and optimizing the in vivo performance of calcium phosphate-based implants.