Shinn-Jyh Ding

Novel fast-setting calcium silicate bone cements with high bioactivity and enhanced osteogenesis in vitro

Novel calcium silicate cements (CSCs) consisting of sol-gel-derived calcium silicate powder as a solid phase and ammonium phosphate solution as a liquid phase were developed. The diametral tensile strength, morphology, and phase composition of various cements were evaluated before and after immersion in physiological solution, in addition to setting time. The proliferation and osteogenetic expression of human osteosarcoma cell line U2OS for the cement specimens were also analyzed. The results indicated that the simultaneous formation of apatite and calcium silicate hydrates (CaO–SiO2–H2O, C–S–H) may endow CSCs with unique properties after mixing with a phosphate buffer solution. These CSCs were not only fast-setting within 9 min, as well as highly bioactive, but they also enhanced proliferation and differentiation of U2OS cells. The development of fast-setting CSCs with high bioactivity may thus have numerous applications as biomaterials.

Effects of altering the Si/Ca molar ratio of a calcium silicate cement on in vitro cell attachment

AIM To examine the effects of altering the Si/Ca molar ratio (6 : 4, 5 : 5, and 4 : 6) of a quick-setting calcium silicate cement on in vitro cell attachment. METHODOLOGY Working time and setting time of three different calcium silicate cements were measured. Alamar Blue was used for real-time and repeated monitoring of cell attachment and proliferation. The Si and Ca ion concentrations of the cell culture medium in the presence of three different calcium silicate cements seeded with MG63 cells were measured. Kinetic immunofluorescent staining of MG63 cells was performed during cell attachment and spreading. Reverse transcription-polymerase chain reaction was employed to determine gene expression in MG63 cells cultured on the cements. One-way analysis of variance was used to evaluate the significance of the differences between the mean values. RESULTS The working time (4-7 min) and setting time (17-24 min) of the cements were shortened with an increase in the Ca content of the calcium silicate powders after mixing the powder with water. In contrast, the higher the Si content in the cement, the more the MG63 cells attached to the cement at all culture time-points, accompanying by the formation of more obvious actin stress fibres. Cell proliferation and differentiation increased significantly (P < 0.05) with an increase in the Si content of the calcium silicate cements. Si ion concentration of the culture medium increased significantly (P < 0.05) with increasing cement Si content and culture time-points. CONCLUSIONS The higher Si content cement enhanced the higher expression of cell attachment, proliferation and differentiation as compared to the lower Si content cement.

Human dental pulp cell responses to new calcium silicate-based endodontic materials

AIM To evaluate human dental pulp cell responses to radiopaque dicalcium silicate cement and white-coloured mineral trioxide aggregate (WMTA). METHODOLOGY Flow cytometry was employed to quantify the phase percentage of pulp cell cycle. Alamar Blue was used for real-time and repeated monitoring of cell proliferation. Reverse transcription-polymerase chain reaction was performed to determine gene expression in pulp cells cultured on the cements. RESULTS The cells cultured on the radiopaque dicalcium silicate cement had similar S and G2 phases in the cell cycle and proliferation to WMTA at all culture times. In addition, the two materials presented the same evolution with similar values in interleukin-1, inducible nitric oxide synthase, alkaline phosphatase, osteocalcin and bone sialoprotein gene expression at all culture times. CONCLUSIONS The dental pulp cell responses to radiopaque dicalcium silicate cement were similar to those reported for WMTA in terms of cell cycle, proliferation, immunocompatibility and osteogenic differentiation.

Bio-inspired calcium silicate–gelatin bone grafts for load-bearing applications

Bio-inspired calcium silicate–gelatin composites with high strength were prepared through a simple pressing–hydrothermal method for load-bearing applications. The phase composition, morphology, and mechanical properties, including the in vitro fatigue behavior, were evaluated. Additionally, in vitro tests were conducted to investigate the biocompatibility of the composites. The results showed that gelatin was dispersed uniformly in the calcium silicate phase and that there was no phase separation between the two phases. Among the composites studied, the 10 wt% gelatin-containing calcium silicate not only exhibited the maximum value of the compressive strength (141.7 MPa), which is strong enough to be used in load-bearing sites of bone tissue, but also had a higher Weibull modulus, indicating a more uniform strength distribution and higher structural reliability. The stability of the composites was affected by in vitro cyclic loading. The presence of gelatin provided a favorable environment for osteoblast-like cells, resulting in a larger degree of cell proliferation, cell differentiation and mineralized tissue formation compared to the control without gelatin. Based on the above results, the bio-inspired calcium silicate–gelatin composites, in particular that containing 10 wt% gelatin, with high initial strength may be an acceptable bone graft substitute as a candidate for load-bearing tissue repair.

Physicochemical properties of radiopaque dicalcium silicate cement as a root-end filling material in an acidic environment.

AIM To investigate the effect of two solutions differing by pH (7.4 and 4.0) on the physicochemical properties of a radiopaque dicalcium silicate cement. METHODOLOGY The cement was prepared by hand-mixing the dicalcium silicate powder with distilled water in a liquid-to-powder ratio of 0.4 mL g(-1) . A total of 253 cement specimens with dimension of 6 mm (diameter) × 3 mm (height) were used. The morphology, weight loss, porosity and diametral tensile strength of the cement were evaluated after soaking in a solution for different time intervals, in addition to pH changes in the cement-immersed solutions. RESULTS After soaking in a pH 7.4 solution for 1 day, the particle size of precipitated apatite spherulites on the cement surfaces was greater than that obtained in a pH 4.0 solution. Solution pH did not result in a significant difference (P > 0.05) in diametral tensile strength of cement specimens at the same soaking time-point. On day 30, the sample was associated with a weight loss of 0.8% in a pH 4.0 solution, whereas in a pH 7.4 solution, a weight increase of 0.2% occurred. A greater porosity of the cement soaked in a pH 4.0 was found compared with that in the solution with pH 7.4. Soaking time affected significantly (P < 0.05) the porosity, weight change and strength of the cements in an acidic environment more than at pH 7.4. CONCLUSIONS High apatite-forming activity and low degradation were the characteristics of a radiopaque dicalcium silicate cement.