The rheological behavior of a fast-setting calcium phosphate bone cement and its dependence on deformation conditions

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

“…The less soluble β-tricalcium phosphate may dissolve completely depending on the solution pH, temperature, and the volume of water or may remain covered by the brushite crystals. Quantitative phase analysis of set cement samples revealed that the latter was the case and about 10% of the initial β-TCP residue remained undissolved in the quiescent samples as reported in our previous study(Şahin & Kalyon, 2017).The overall dynamic rheological properties reveal that the initial slow setting rates of the presheared samples catch up with that of the quiescent samples around the initial setting time and exceed it during the setting period and on. This is attributed to the evolving cement microstructure that gets gradually depleted in calcium phosphate ions.…”

“…In our previous study, we have seen that brushite cement setting quiescently in 0.5 M citric acid solution reaches the dough time (when cement can be shaped without sticking to the hand but also when it starts to thicken rapidly leading to poor injectability) in 300 s, the initial setting time (when a continuous, solid network structure forms by inter‐growing crystals) in 540 s and the final setting time (when the microstructure is predominantly solid) in about 1,200 s. (circular data points in Figure 1). Also, the LVS limit was found to increase from 0.05 to 0.1 as setting progressed (Şahin & Kalyon, 2017). These parameters are conveniently determined from the variation of the dynamic rheological properties with time (tan δ ≈ 0.5 at the dough time; Gʹ rises exponentially at the initial setting time; and Gʹ reaches a plateau at the final setting time) and with strain amplitude (Gʹ remains constant until the strain amplitude reaches the LVS limit), respectively.…”

“…The dynamic properties of the bone cement were both modified and characterized as a function of time at different shearing modes and shear rates. This partitioning of the preshearing and characterization runs was done to apply the same measurement conditions for comparison of different shearing histories as explained elsewhere (Şahin & Kalyon, 2017). During rheological characterization and preshearing, the cement specimen was sandwiched between two aluminium discs (25 mm diameter), one of which either oscillates (consecutive clockwise and counterclockwise cycles) or rotates at constant angular velocity while the second disc remains stationary.…”

“…The dynamic properties of the bone cement were both modified and characterized as a function of time at different shearing modes and shear rates. This partitioning of the preshearing and characterization runs was done to apply the same measurement conditions for comparison of different shearing histories as explained elsewhere (Şahin & Kalyon, 2017 For the oscillatory preshearing runs, the strain amplitude was kept within the linear viscoelastic strain (LVS) range at 0.04, 0.1 and outside LVS range at 1. The frequencies of 0.1, 1, 10 and 100 rad/s were applied for varying durations from 120 s to 2000 s.…”

“…Recently, we reported the effect of deformation conditions on the rheological properties of brushite cement by utilizing small amplitude oscillatory rheometry (a.k.a. mechanical spectrometry) (Şahin & Kalyon, 2017). This technique resolves the mechanical behaviour of a suspension into the storage modulus (Gʹ), representing the propensity to store the mechanical energy elastically in the solid phase, and the loss modulus (Gʹʹ), representing the propensity to dissipate the mechanical energy viscously in the liquid phase.…”