The successful osseointegration of an implant depends on numerous factors, both material-related (phase composition, mechanical properties, implant morphology, presence of doping agents) and recipient-related (health status, nature of inflammation, material's influence on immunostimulation and reparative histogenesis). Modeling each stage of regeneration separately and combining stages gradually to form a comprehensive model appears to be an appropriate approach for identifying relationships between these factors.
This study aims to assess the contribution of the resorption rate of the osteoplastic material to the process of bone defect regeneration. Dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP), and hydroxyapatite (HA), obtained by the hydrolysis of precursors, were used. Resorption kinetics were evaluated using isotonic buffer solutions SBF and PBS in stationary and dynamic closed systems (up to 28 days; t=37°C; without solution replacement). In the stationary system, a phase transformation of DCPD to OCP was observed for both solutions, which was quantitatively described by a theoretical model based on first principles of chemical kinetics. An equilibrium between the material and saturated solution was observed for OCP and HA samples.
For experiments in the dynamic system, a bioreactor was developed to mimic physiological fluid flow. Under these conditions, no phase transformation of DCPD to OCP occurred in either solution, and an equilibrium between the material and saturated solution was observed. This was explained within the previously obtained theoretical model, taking into account Fick's second law.
Similar experiments were conducted using a mixture of culture medium DMEM and bovine blood serum. It was found that serum albumin adsorbs as a monolayer on the surface of calcium phosphates (Langmuir-type I isotherm), significantly inhibiting the dissolution rate of DCPD and the crystallization rate of OCP.
All obtained data were described within a unified theoretical model, further development of which is the focus of future research.
