Abstract
Synthetic apatites are widely used both in the dental and the orthopaedic fields due to their similarity in composition with the inorganic phase of hard tissues. Biologic apatites are not pure hydroxyapatite (HA), but are calcium-deficient apatites with magnesium and carbonate as minor but important substituents. The aim of the present study was to produce a more soluble biomaterial through the simultaneous substitution of magnesium and carbonate in the apatite structure to accelerate the degradation time in the body. The physico-chemical and dissolution properties of unsintered magnesium and carbonate-substituted apatite (MCAp) with similar Mg/Ca molar ratio (0.03) and varying C/P molar ratio were evaluated. The resultant powders were characterised using several techniques, such as FTIR, TGA, XRD, ICP and SEM, while the release of calcium ions in a pH 6 solution was monitored using a Ca-ion selective electrode. The results showed a decrease of crystallite size and an increase in the release of calcium to the medium as the carbonate content in the samples increased.
Highlights
IntroductionThe apatite structure, e.g. hydroxyapatite (Ca10(PO4)6(OH)2), allows cationic (for Ca2+) and anionic (for PO 3– and/or OH– groups) substitutions
Synthetic apatites and related calcium phosphates are biocompatible, bioactive, and osteoconductive compounds and their similarity in composition to bone and tooth make them the most commonly used ceramics for bone repair in orthopaedics and dentistry[1,2].The apatite structure, e.g. hydroxyapatite (Ca10(PO4)6(OH)2), allows cationic and anionic substitutions
Magnesium (Mg2+) and carbonate (CO 2–) are two minor 3 but important elements associated with biological apatites, which have an average concentration of 0.6 wt. (%) Mg2+ and 7.5 wt. (%) CO32– in the case of bone apatite[1,7,8]
Summary
The apatite structure, e.g. hydroxyapatite (Ca10(PO4)6(OH)2), allows cationic (for Ca2+) and anionic (for PO 3– and/or OH– groups) substitutions. Such substitutions affect the crystallography (crystal size, lattice parameters), physico-chemical properties (e.g., solubility) and cell and tissue response[1,2,3,4,5,6]. Magnesium incorporation in apatite lattice is very limited and is directly dependent on Mg/Ca molar ratio, temperature, pH and the presence of carbonate[1,7,8]. Even the limited incorporation of magnesium causes disturbances in the apatite lattice, decreasing its crystallinity and increasing the dissolution rates[1,7,8,9,10,11]
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