Magnesium phosphate cements (MPC) have been demonstrated to have a superior bone regeneration capacity due to their good solubility under in vivo conditions. While in the past only aqueous MPC pastes have been applied, the current study describes the fabrication and in vitro/in vivo testing of an oil-based calcium doped magnesium phosphate (CaMgP) cement paste. Premixed oil-based pastes with CaMgP chemistry combine the advantages of conventional MPC such as high mechanical strength and good resorbability with a prolonged shelf-life and an easier clinical handling. The pastes set in an aqueous environment and predominantly form struvite and achieve a compressive strength of ~8–10 MPa after setting. The implantation into a drill-hole defect at the distal femoral condyle of New Zealand white rabbits over a course of 6 and 12 weeks demonstrated good biocompatibility of the materials without the formation of soft connective tissue or any signs of inflammation. In contrast to a hydroxyapatite forming reference paste, the premixed CaMgP pastes showed subsequent degradation and bony regeneration. The CaMgP cement pastes presented herein are promising bone replacement materials with excellent material properties for an improved and facilitated clinical application.

Calcium phosphate cements (CPCs) are widely used for bone-defect treatment. Current developments comprise the fabrication of porous scaffolds by three-dimensional plotting and doting using biologically active substances, such as strontium. Strontium is known to increase osteoblast activity and simultaneously to decrease osteoclast resorption. This study investigated the short- and long-term in vivo performances of strontium(II)-doted CPC (SrCPC) scaffolds compared to non-doted CPC scaffolds after implantation in unloaded or load-bearing trabecular bone defects in sheep. After 6 weeks, both CPC and SrCPC scaffolds exhibited good biocompatibility and osseointegration. Fluorochrome labeling revealed that both scaffolds were penetrated by newly formed bone already after 4 weeks. Neither strontium doting nor mechanical loading significantly influenced early bone formation. In contrast, after 6 months, bone formation was significantly enhanced in SrCPC compared to CPC scaffolds. Energy dispersive X-ray analysis demonstrated the release of strontium from the SrCPC into the bone. Strontium addition did not significantly influence material resorption or osteoclast formation. Mechanical loading significantly stimulated bone formation in both CPC and SrCPC scaffolds after 6 months without impairing scaffold integrity. The most bone was found in SrCPC scaffolds under load-bearing conditions. Concluding, these results demonstrate that strontium doting and mechanical loading additively stimulated bone formation in CPC scaffolds and that the scaffolds exhibited mechanical stability under moderate load, implying good clinical suitability. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:106-117, 2018.

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