@article{RoedelTessmarGrolletal.2019,
  author    = {R{\"o}del, Michaela and Teßmar, J{\"o}rg and Groll, J{\"u}rgen and Gbureck, Uwe},
  title     = {Tough and Elastic alpha-Tricalcium Phosphate Cement Composites with Degradable PEG-Based Cross-Linker},
  series = {Materials},
  volume    = {12},
  journal   = {Materials},
  number    = {53},
  doi       = {10.3390/ma12010053},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226437},
  pages     = {1-20},
  year      = {2019},
  abstract  = {Dual setting cements composed of an in situ forming hydrogel and a reactive mineral phase combine high compressive strength of the cement with sufficient ductility and bending strength of the polymeric network. Previous studies were focused on the modification with non-degradable hydrogels based on 2-hydroxyethyl methacrylate (HEMA). Here, we describe the synthesis of suitable triblock degradable poly(ethylene glycol)-poly(lactide) (PEG-PLLA) cross-linker to improve the resorption capacity of such composites. A study with four different formulations was established. As reference, pure hydroxyapatite (HA) cements and composites with 40 wt\% HEMA in the liquid cement phase were produced. Furthermore, HEMA was modified with 10 wt\% of PEG-PLLA cross-linker or a test series containing only 25\% cross-linker was chosen for composites with a fully degradable polymeric phase. Hence, we developed suitable systems with increased elasticity and 5-6 times higher toughn ess values in comparison to pure inorganic cement matrix. Furthermore, conversion rate from alpha-tricalcium phosphate (alpha-TCP) to HA was still about 90\% for all composite formulations, whereas crystal size decreased. Based on this material development and advancement for a dual setting system, we managed to overcome the drawback of brittleness for pure calcium phosphate cements.},
  language  = {en}
}
@article{NoHolzmeisterLuetal.2019,
  author    = {No, Young Jung and Holzmeister, Ib and Lu, Zufu and Prajapati, Shubham and Shi, Jeffrey and Gbureck, Uwe and Zreiqat, Hala},
  title     = {Effect of Baghdadite Substitution on the Physicochemical Properties of Brushite Cements},
  series = {Materials},
  volume    = {12},
  journal   = {Materials},
  number    = {10},
  issn      = {1996-1944},
  doi       = {10.3390/ma12101719},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-196980},
  year      = {2019},
  abstract  = {Brushite cements have been clinically used for irregular bone defect filling applications, and various strategies have been previously reported to modify and improve their physicochemical properties such as strength and injectability. However, strategies to address other limitations of brushite cements such as low radiopacity or acidity without negatively impacting mechanical strength have not yet been reported. In this study, we report the effect of substituting the beta-tricalcium phosphate reactant in brushite cement with baghdadite (Ca\(_3\)ZrSi\(_2\)O\(_9\)), a bioactive zirconium-doped calcium silicate ceramic, at various concentrations (0, 5, 10, 20, 30, 50, and 100 wt\%) on the properties of the final brushite cement product. X-ray diffraction profiles indicate the dissolution of baghdadite during the cement reaction, without affecting the crystal structure of the precipitated brushite. EDX analysis shows that calcium is homogeneously distributed within the cement matrix, while zirconium and silicon form cluster-like aggregates with sizes ranging from few microns to more than 50 µm. X-ray images and µ-CT analysis indicate enhanced radiopacity with increased incorporation of baghdadite into brushite cement, with nearly a doubling of the aluminium equivalent thickness at 50 wt\% baghdadite substitution. At the same time, compressive strength of brushite cement increased from 12.9 ± 3.1 MPa to 21.1 ± 4.1 MPa with 10 wt\% baghdadite substitution. Culture medium conditioned with powdered brushite cement approached closer to physiological pH values when the cement is incorporated with increasing amounts of baghdadite (pH = 6.47 for pure brushite, pH = 7.02 for brushite with 20 wt\% baghdadite substitution). Baghdadite substitution also influenced the ionic content in the culture medium, and subsequently affected the proliferative activity of primary human osteoblasts in vitro. This study indicates that baghdadite is a beneficial additive to enhance the radiopacity, mechanical performance and cytocompatibility of brushite cement},
  language  = {en}
}
@article{BoehmMeiningerTeschetal.2018,
  author    = {Boehm, Anne and Meininger, Susanne and Tesch, Annemarie and Gbureck, Uwe and M{\"u}ller, Frank A.},
  title     = {The mechanical properties of biocompatible apatite bone cement reinforced with chemically activated carbon fibers},
  series = {Materials},
  volume    = {11},
  journal   = {Materials},
  number    = {2},
  issn      = {1996-1944},
  doi       = {10.3390/ma11020192},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-197808},
  pages     = {192},
  year      = {2018},
  abstract  = {Calcium phosphate cement (CPC) is a well-established bone replacement material in dentistry and orthopedics. CPC mimics the physicochemical properties of natural bone and therefore shows excellent in vivo behavior. However, due to their brittleness, the application of CPC implants is limited to non-load bearing areas. Generally, the fiber-reinforcement of ceramic materials enhances fracture resistance, but simultaneously reduces the strength of the composite. Combining strong C-fiber reinforcement with a hydroxyapatite to form a CPC with a chemical modification of the fiber surface allowed us to adjust the fiber-matrix interface and consequently the fracture behavior. Thus, we could demonstrate enhanced mechanical properties of CPC in terms of bending strength and work of fracture to a strain of 5\% (WOF5). Hereby, the strength increased by a factor of four from 9.2 ± 1.7 to 38.4 ± 1.7 MPa. Simultaneously, the WOF5 increased from 0.02 ± 0.004 to 2.0 ± 0.6 kJ∙m-2, when utilizing an aqua regia/CaCl2 pretreatment. The cell proliferation and activity of MG63 osteoblast-like cells as biocompatibility markers were not affected by fiber addition nor by fiber treatment. CPC reinforced with chemically activated C-fibers is a promising bone replacement material for load-bearing applications.},
  language  = {en}
}