Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Abstract

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO4) possessing variable compositional but rather identical glass-like physical properties, in which there are neither...

Prevention of Caries and Dental Erosion by Fluorides—A Critical Discussion Based on Physico-Chemical Data and Principles

“…However, it is unclear whether a sintered solid block of hydroxyapatite has the same properties as a less dense and partially porous sample of tooth enamel, also with respect to the lower acid solubility of sintered hydroxyapatite in comparison to biological apatite that contains carbonate [ 11 ]. It is likely that the acid resistance of a sintered hydroxyapatite block is higher than that of biological apatite [ 11 , 38 , 39 , 40 ].…”

The Osteoinductivity of Calcium Phosphate-Based Biomaterials: A Tight Interaction With Bone Healing

“…For bone-filling purposes, CaPs have been utilized as bioactive components of solid ceramic, coatings, self-setting CaP cements (CPC), as well as advanced polymers, intending to function as a scaffold for bone formation ( Parent et al, 2017 ). The family of CaP biomaterials comprises varying phase compositions, including HA [Ca 10 (PO 4 ) 6 (OH) 2 ], tricalcium phosphate [TCP, Ca 3 (PO 4 ) 2 ], octacalcium phosphate [OCP, Ca 8 (HPO 4 ) 2 (PO 4 ) 4 ·5H 2 O], dicalcium phosphate dihydrate [DCPD, CaHPO 4 .2H 2 O], and amorphous calcium phosphate [ACP, CaxHy(PO 4 )z·nH 2 O, n = 3–4.5; 15–20% H 2 O], can be used in a variety of applications due to differences in solubility, stability, and mechanical strength ( Jeong et al, 2019 ; Dorozhkin, 2021 ). CaP-based biomaterials provide a strong biomaterial/bone interface and demonstrate promising biological properties such as biodegradability, osteoconductivity, and in some cases even osteoinductivity (i.e., the ability of the material to induce de novo bone formation without the presence of osteogenic factors) ( LeGeros, 2008 ; Chai et al, 2012 ; Stastny et al, 2019 ).…”

The influence of annealing conditions on the Ca/P ratio and phase transformations in bulk calcium phosphates

“…For most CPs, with the exception of amorphous CP (ACP) and calcium-deficient hydroxyapatite (CDHA), this value is fixed, and the discrepancy of this ratio leads to the co-existence of two or more CP phases. 3 While some CPs can be prepared directly by precipitation from aqueous solution, some phases can only be obtained by employing thermal treatment. Conventionally, for thermally induced synthesis, Ca and P salts, such as CaCO 3 , CaHPO 4 , CaHPO 4 ·2H 2 O, (NH 4 ) 2 HPO 4 , etc.…”