title: Dual setting α-tricalcium phosphate cements.
abstract: An extension of the application of calcium phosphate cements (CPC) to load-bearing defects, e.g. in vertebroplasty, would require less brittle cements with an increased fracture toughness. Here we report the modification of CPC made of alpha-tricalcium phosphate (α-TCP) with 2-hydroxyethylmethacrylate (HEMA), which is polymerised during setting to obtain a mechanically stable polymer-ceramic composite with interpenetrating organic and inorganic networks. The cement liquid was modified by the addition of 30-70 % HEMA and ammoniumpersulfate/tetramethylethylendiamine as initiator. Modification of α-TCP cement paste with HEMA decreased the setting time from 14 min to 3-8 min depending on the initiator concentration. The 4-point bending strength was increased from 9 MPa to more than 14 MPa when using 50 % HEMA, while the bending modulus decreased from 18 GPa to approx. 4 GPa. The addition of ≥50 % HEMA reduced the brittle fracture behaviour of the cements and resulted in an increase of the work of fracture by more than an order of magnitude. X-ray diffraction analyses revealed that the degree of transformation of α-TCP to calcium deficient hydroxyapatite was lower for polymer modified cements (82 % for polymer free cement and 55 % for 70 % HEMA) after 24 h setting, while the polymerisation of HEMA in the cement liquid was quantitative according to FT-IR spectroscopy. This work demonstrated the feasibility of producing fracture resistant dual-setting calcium phosphate cements by adding water soluble polymerisable monomers to the liquid cement phase, which may be suitable for an application in load-bearing bone defects.
authors.affiliation: Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, 97070, Würzburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Christel
authors.forename: M
authors.initials: M
authors.lastname: Kuhlmann
authors.forename: E
authors.initials: E
authors.lastname: Vorndran
authors.forename: J
authors.initials: J
authors.lastname: Groll
authors.forename: U
authors.initials: U
authors.lastname: Gbureck
mesh_terms: D001843:Bone Cements / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate