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The core aim of this study was to investigate zinc (Zn)and zinc and strontium (ZnSr)-containing brushite-forming β-tricalcium phosphate (TCP) cements for their effects on proliferation and differentiation of osteoblastic-like cells (MC3T3-E1 cell line) as well as for their in vivo behaviour in trabecular bone cylindrical defects in a pilot study. In vitro proliferation and maturation responses of MC3T3-E1 osteoblastic-like cells to bone cements were studied at the cellular and molecular levels. The Zn-and Sr-containing brushite cements were found to stimulate pre-osteoblastic proliferation and osteoblastic maturation. Indeed, MC3T3-E1 cells exposed to the powdered cements had increased proliferative rates and higher adhesiveness capacity, in comparison to control cells. Furthermore, they exhibited higher alkaline phosphatase (ALP) activity and increased Type-I collagen secretion and fibre deposition into the extracellular matrix. Proliferative and collagen deposition properties were more evident for cells grown in cements doped with Sr. The in vivo osteoconductive properties of the ZnCPC and ZnSrCPC cements were also pursued. Histological and histomorphometric analyses were performed at 1 and 2 months after implantation, using carbonated apatite cement (Norian SRS ® ) as control. There was no evidence of cement-induced adverse foreign body reactions, and furthermore ZnCPC and ZnSrCPC cements revealed better in vivo performance in comparison to the control apatite cement. Additionally, the presence of both zinc and strontium resulted in the highest rate of new bone formation. These novel results indicate that the investigated ZnCPC and ZnSrCPC cements are both biocompatible and osteoconductive, being good candidate materials to use as bone substitutes. a Both authors contributed equally to this work 163 www.ecmjournal.org S Pina et al. Brushite-forming bone cements

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Three types of tetraalkyl ammonium hydroxides (TANOHs)-namely, tetramethyl ammonium hydroxide (TMNOH), tetraethyl ammonium hydroxide (TENOH), and tetrabutyl ammonium hydroxide (TBNOH)-were used as peptizing agents for the hydrothermal synthesis of nanocrystalline TiO 2 powders. X-ray diffractometry, Brunauer-Emmett-Teller surface-area analysis, differential thermal analysis-thermogravimetry, scanning electron microscopy, and transmission electron microscopy were used to characterize the powders. The results showed that the carbon-chain length of TANOHs had a great influence on the particle size, particle shape, and the phase transformation of the hydrothermally derived TiO 2 particles. Anatase phase was obtained in all the samples, regardless of the peptizer used, and the particle size increased as the peptizer cation size decreased. In the presence of TMNOH, the particle shape changed from spherical at low concentration to rodlike with increasing TMNOH concentration, whereas a transition from a spherical morphology to an asterisk-like structure was observed in the TENOH peptized samples. However, spherical particles were formed in all the TBNOH peptized samples. The anatase-rutile transition occurred at a lower temperature for the TENOH-derived powders, relative to the other two peptizers.