Monetite promoting effect of citric acid on brushite cement setting kinetics

Abstract

Brushite forming calcium phosphate cements receive growing interest in hard tissue scaffold applications due to their high surface area and high bioresorbability. The finer microstructure of monetite, the dehydrated form of brushite, has attracted attention for bone tissue engineering applications. The reduction in brushite content of the b-tricalcium phosphate-monocalcium phosphate monohydrate cement system by selective inhibition of growth upon addition of citric acid to excess setting liquid was investigated. The relaxation period during cement setting was monitored by pH stat titration and free drift runs. Spectrometric analysis revealed that the change in solubility of calcium phosphates upon addition of citric acid caused the inhibition of brushite formation and promotion of monetite precipitation. Dissolution of monetite crystals was insensitive to citrate adsorption despite their lower surface area compared to brushite. Overall brushite/ monetite ratio decreased consistently with increasing citric acid concentration in the of 0?1-0?5M range.

Complex phase evolution of Brushite-based calcium phosphate CaHPO4·2H2O using in situ high temperature X-ray diffraction and thermal analysis

“…As can be seen from Fig. 7a, the morphology of commercial DCPD particles is dominated by plate-shaped crystals superimposed showing the sheet structure of DCPD as reported for other sources of DCPD [46,47]. This microstructure persists even for DCPA crystals (Fig.…”

Preshearing is an in situ setting modification method for inorganic bone cements

“…The resulting net setting promoting effect as evident in the increasing peak heights with increasing oscillation frequency is attributed to an enhanced crystal growth rate as the left‐hand side of the peaks reflects the changes in crystal growth rate at high initial supersaturations whereas dissolution is the rate‐limiting mechanism at later stages of setting in calcium phosphate cements. (Fernandez et al., 1996; Şahin & Çiftçioğlu, 2014). Each different cement formulation is expected to exhibit different dependence on oscillation frequency, and a characteristic “setting promoting frequency limit” should be sought by similar measurements in order to control their setting rate.…”

“…whereas dissolution is the rate-limiting mechanism at later stages of setting in calcium phosphate cements. (Fernandez et al, 1996;Şahin & Çiftçioğlu, 2014). Each different cement formulation is expected to exhibit different dependence on oscillation frequency, and a characteristic "setting promoting frequency limit" should be sought by similar measurements in order to control their setting rate.…”

“…The setting reactions involve the dissolution of calcium‐rich basic and phosphate‐rich acidic species, and the subsequent precipitation of a more stable phase (Fukase, Eanes, Takagp, Chow, & Brown, 1990; Mirtchi, Lemaitre, & Terao, 1989) or hydrolysis of a metastable, stoichiometrically similar calcium phosphate to the final apatitic phase (Ginebra, Fernandez, et al., 1995; Bohner, 2005). The setting kinetics, rheological and mechanical properties of calcium phosphate cements have been extensively investigated and correlated with various factors that directly affect the dissolution, crystallization and growth of calcium phosphates including pH (Bohner, 1997), temperature (Liu, 2003), particle size and crystallinity (Fernandez et al., 1996, 1998; Gbureck, Dembski, Thull, & Barralet, 2005), water content (Xu, Quinn, Takagi, & Chow, 2002), ionic strength (Şahin & Çiftçioğlu, 2013), surface charge (Gbureck, Probst, & Thull, 2002), concentrations of calcium phosphate ions (Wang & Nancollas, 2008; Komath, Varma, & Sivakumar, 2000) and chemicals that have affinity to them (TenHuisen & Brown, 1997, Şahin & Çiftçioğlu, 2014). Two main types of calcium phosphate cements, hydroxyapatite and brushite‐forming cements, undergo setting in quite different rates, the latter setting much more rapidly due to the water consuming reaction of relatively fast dissolving precursors, suiting the clinical requirements for vertebroplasty, that is being workable for about 5–10 min and harden in about 15 min (Heini & Berlemann, 2001).…”

“…ionic strength (Şahin & Çiftçioğlu, 2013), surface charge (Gbureck, Probst, & Thull, 2002), concentrations of calcium phosphate ions (Wang & Nancollas, 2008;Komath, Varma, & Sivakumar, 2000) and chemicals that have affinity to them (TenHuisen & Brown, 1997, Şahin & Çiftçioğlu, 2014. Two main types of calcium phosphate cements, hydroxyapatite and brushite-forming cements, undergo setting in quite different rates, the latter setting much more rapidly due to the water consuming reaction of relatively fast dissolving precursors, suiting the clinical requirements for vertebroplasty, that is being workable for about 5-10 min and harden in about 15 min (Heini & Berlemann, 2001).…”