Effect of Calcium and Phosphate on Compositional Conversion from Dicalcium Hydrogen Phosphate Dihydrate Blocks to Octacalcium Phosphate Blocks

Abstract

Octacalcium phosphate (OCP) has attracted much attention as an artificial bone substitute because of its excellent osteoconductive and bone replacement properties. Although numerous studies have investigated OCP powder fabrication, there are only a few studies on OCP block fabrication. Therefore, in this study, the feasibility of optimizing dicalcium hydrogen phosphate dihydrate (DCPD) blocks, as a precursor for OCP block fabrication, under a pH 6 adjusted acetate buffer solution at 70 • C for 2 days was investigated. When a DCPD block was immersed in acetate buffer, the block was partially converted to OCP, with a large amount of dicalcium hydrogen phosphate anhydrate (DCPA), and its macroscopic structure was maintained. When the DCPD block was immersed in a Ca-containing solution, it was converted to mainly hydroxyapatite (HAp) with DCPA. On the other hand, when the DCPD block was immersed in a PO 4 -containing solution, the block was converted to OCP, and its macroscopic structure was maintained. In other words, the PO 4 -induced calcium phosphate with a Ca/P molar ratio lower than 1.0 may represent an intermediate phase during the compositional transformation from a DCPD block to an OCP block through the dissolution-precipitation reaction.

Phosphoserine Functionalized Cements Preserve Metastable Phases, and Reprecipitate Octacalcium Phosphate, Hydroxyapatite, Dicalcium Phosphate, and Amorphous Calcium Phosphate, during Degradation, In Vitro

“…Formation of hydroxyapatite is thermodynamically favorable near neutral pH. Therefore, it is likely that the formation of hydroxyapatite under acidic conditions (pH 2.7) results from conversion of acidic metastable phases OCP and DCPD [74,75]. Since these phases form readily in acidic conditions and are metastable, hydroxyapatite is expected to form conversion from OCP and DCPD, during the ongoing dissolution/reprecipitation reaction [75,76].…”

Feasibility evaluation of low-crystallinity β-tricalcium phosphate blocks as a bone substitute fabricated by a dissolution–precipitation reaction from α-tricalcium phosphate blocks

“…In a previous study, some of the co-authors involved in this research showed that OCP, a calcium phosphate formed via amorphous phase, is likely to be formed under PO 4 -rich condition. 33 Therefore, we conclude that for b-TCP formation in acidic aqueous solution, both Mg 2þ and PO 4 ions are needed for the inhibition of stable phase and inducer of precursor phases, respectively.…”

“…In fact, blockstructured octacalcium phosphate (OCP: Ca 8 (HPO 4 ) 2 (PO 4 ) 4 Á5H 2 O), which is a metastable phase of calcium phosphate, could have been prepared through a dissolution-precipitation reaction. 13,14 Jang et al 15 prepared b-TCP powder from HAp under acidic conditions through a dissolution-precipitation reaction. Even though dicalcium phosphate dihydrate (DCPD: CaHPO 4 Á2H 2 O) and dicalcium phosphate anhydrate (DCPA: CaHPO 4 ) are stable phases under acidic conditions, Mg 2þ can inhibit their formation or crystallization, thus resulting in b-TCP as an intermediate phase obtained under acidic conditions.…”

Dual Energy X-ray Methods for the Characterization, Quantification and Imaging of Calcification Minerals and Masses in Breast

“…The use of balanced filtering in dual energy technique was applied by Saito [29] in order to achieve a signal-to-noise ratio of 5 in the final dual energy subtracted iodine image. Although the appearance of calcifications may indicate breast cancer, the consistency of calcifications will indicate whether they are associated with malignancy or benignancy [69][70][71][72][73][74][75][76][77][78][79][80][81]87]. Martini et al [28] worked on the differentiation of calcifications consisting of minerals found to indicate malignancy and benignancy according to literature [103][104][105].…”

“…The calcifications of Type I are composed calcium oxalate (CaC2O4) crystals [76] and are found to be associated with benign lesions or mostly non-invasive lobular carcinoma in situ [77,78]. The calcifications of Type II are composed of calcium phosphate, mainly hydroxyapatite (Hap) crystals [76,[79][80][81] and in some cases of calcium carbonate (CaCO 3 ). Hydroxyapatite is associated with malignancy including carcinomas, while calcium carbonate crystals [82][83][84][85][86] with benignancy [44,45,70,87].…”