Osteoclast-mediated bioresorption can be an efficient means of incorporating the dissolution of biomaterials in the bone remodeling process. Because of the compositionally and structurally close resemblance of biomaterials with the natural mineral phases of the bone matrix, synthetic carbonate-substituted apatite (CA) is considered as an ideal biomaterial for clinical use. The present study therefore investigated the effects of electrical polarization on the surface characteristics and interactions with human osteoclasts of hydroxyapatite (HA) and CA. Electrical polarization was found to improve the surface wettability of these materials by increasing the surface free energy, and this effect was maintained for 1 month. Analyses of human osteoclast cultures established that CA subjected to a polarization treatment enhanced osteoclast resorption but did not affect the early differentiation phase or the adherent morphology of the osteoclasts as evaluated by staining. These data suggest that the surface characteristics of the CA promoted osteoclast resorption. The results of this work are expected to contribute to the future design of cell-mediated bioresorbable biomaterials capable of resorption by osteoclasts and of serving as a scaffold for bone regeneration.

Maximizing vital bone in a grafted site is dependent on a number of factors. These include resorption or turnover of the graft material, stimulation of bone formation pathway without a need for biological molecules added to the site and inhibition of cellular activities that compromise the mineralization of new bone matrix. In the present study, the dissolution profile of silica‐calcium phosphate composite (SCPC) in physiological solution was measured and the data were fed to (ANN‐NARX) prediction model to predict the time required for complete dissolution. The inductively coupled plasma‐optical emission spectrometer ionic composition analysis of the culture medium incubated for 3 days with SCPC showed 57% decrease in Ca concentration and a significant increase in the concentration of Si (13.5 ± 1.8 μg/ml), P (249.4 ± 22 μg/ml), and Na (9.3 ± 0.52 μg/ml). In conjunction with the release of Si, P, and Na ions, the bone resorptive activity of osteoclasts was inhibited as indicated by the significant decrease in multinucleated tartrate resistant acidic phosphate stained cells and the volume of resorption pits on bone slices. In contrast, addition of SCPC to hBMSC cultured in conventional medium promoted higher Runt‐related transcription factor 2 (p < .05), osteocalcin (p < .01), and bone sialo protein (p < .01) than that expressed by control cells grown in the absence of SCPC. The predicted dissolution time of 200 mg of porous SCPC particles in 10 ml phosphate buffered saline is 6.9 months. An important byproduct of the dissolution is inhibition of osteoclastic activity and promotion of osteoblastic differentiation and hence bone formation.

Bone graft materials are widely used in orthopedic and maxillofacial surgeries. The controlled resorbability of the graft material is essential for bone regeneration. Hydroxyapatite and biphasic calcium phosphate bone grafts have poor resorption and limited bone conductive effects. Histology analyses of bone biopsy from SCPC grafted human extraction sockets showed complete bone regeneration and graft resorption in absence of osteoclasts and macrophages. The hypothesis of the present study is that bioactive SCPC inhibits osteoclast’s activity due to the presence of resorbable silica phase in the material. Our objective is to analyze the effect of SCPC dissolution products on the resorption activity of osteoclasts. The conditioned medium was prepared by immersion of SCPC resorbable bioactive SCPC porous granules (Shefabone, Inc, USA) in cell culture medium at various ratios at 37°C for 3 days. The concentration of Si ions released from the SCPC granules into cell culture medium was measured using ICP-OES. Osteoclast precursors derived from human bone marrow were seeded on bone slices and cultured in the conditioned medium containing 10% FBS and osteoclast induction factors. Osteoclast differentiation and resorption were evaluated by TRAP staining and measurement of the volume of resorption pits on the bone slices. Mature multinuclear giant TRAP-positive osteoclasts were observed on the bone substrates after 14 days incubation in control medium containing osteoclast induction factors. In conditioned medium, the number of multinuclear TRAP-positive cells was significantly decreased as the concentration of SCPC dissolved silica increased. The dissolution of silica from SCPC into the culture medium correlates well with down regulation of osteoclast differentiation and the rapid bone regeneration in human bone defects.

Calcium carbonate (CC)-hydroxyapatite (HAP) porous microparticles have gained a lot of popularity as a promising material for clinical applications. The objective of this study is to evaluate the effects of CC-HAP microparticles on osteoblast-like cells to be used as a bone-regeneration biomaterial. In this study, the different concentrations of conditioned media were used to compare the effects of released ions from CC-HAP microparticles. The material’s characteristics demonstrated that the immersion in cell culture medium did not change the crystal phases of CC-HAP. The decrease of calcium ions in cell culture medium is due to the dissolution-precipitation reactions on the material surfaces, which made more crystalline surfaces. The atomic absorption spectroscopy measurement demonstrated that the dissolution-precipitation reactions on the material surfaces in cell culture medium happened in 3 days and were stable between 3 to 5 days. The conditioned media immersed in cell culture medium for 4 days were used for further experiments. Cell evaluations demonstrated that excessive adding of CC -HAP could inhibit cell behaviors such as cell adhesion, proliferation, and differentiation. The cell adhesion indicated by the number of vinculin-positive focal adhesions per cell decreased with the increase of the CC-HAP concentrations. The cells cultured with CC-HAP proliferated at a lower rate than the control without CC-HAP. One of the reasons for the inhibition of cell proliferation was thought to be less formation of focal adhesions with higher concentrations of CC-HAP. The excessive adding of CC-HAP had an inhibitory effect on osteoblast differentiation. The results of this study revealed that the conditioned media prepared by immersion of CC-HAP porous microparticles in cell culture media had effects on the behaviors of osteoblast-like cells such as cell adhesion, proliferation, and differentiation.

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