The effect of calcium phosphate ceramic composition and structure on in vitro behavior. I. Dissolution

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Crystallography

Background:

• Synthetic calcium phosphate ceramics (CPCs) can convert to biological apatite via dissolution, precipitation, and ion exchange.
• Material properties significantly influence the reaction kinetics of CPCs.
• Parametric rate effects are critical for optimizing CPC performance.

Purpose of the Study:

• To investigate the impact of stoichiometry and crystal structure on the dissolution kinetics of various CPCs.
• To establish a relationship between CPC composition and their dissolution rates.
• To provide insights into the transformation of synthetic CPCs into biological apatite.

Main Methods:

• Studied monophase, biphase, and multiphase CPCs with Ca/P ratios ≥ 1.5.
• Conducted dissolution experiments in a calcium- and phosphate-free Tris buffer at pH 7.3.
• Analyzed dissolution rates based on CPC stoichiometry and crystal structure.

Main Results:

• Dissolution rates of monophase CPCs increased in the order: stoichiometric hydroxyapatite < calcium deficient hydroxyapatite < oxyhydroxyapatite < beta-tricalcium phosphate < alpha-tricalcium phosphate < tetracalcium phosphate.
• Dissolution of biphase and multiphase CPCs was proportional to the concentration of their more soluble components.
• Significant variations in dissolution behavior were observed across different CPC compositions.

Conclusions:

• CPC stoichiometry and crystal structure are key determinants of dissolution kinetics.
• The dissolution behavior of multiphase CPCs can be predicted based on their constituent phases.
• These findings are vital for designing CPCs with tailored dissolution profiles for biomedical applications.