title: Heat treatment of Na2O-CaO-P2O5-SiO2 bioactive glasses: densification processes and postsintering bioactivity.
abstract: Because of their excellent bioactivity, bioactive glasses are increasingly diffused to produce biomedical devices for bone prostheses, to face the dysfunctions that may be caused by traumatic events, diseases, or even natural aging. However, several processing routes, such as the production of scaffolds or the deposition of coatings, include a thermal treatment to apply or sinter the glass. The exposure to high temperature may induce a devetrification phenomenon, altering the properties and, in particular, the bioactivity of the glass. The present contribution offers an overview of the thermal behavior and properties of two glasses belonging to the Na2O-CaO-P2O5-SiO2 system, to be compared to the standard 45S5 Bioglass(®). The basic goal is to understand the effect of both the original composition and the thermal treatment on the performance of the sintered glasses. The new glasses, the one (BG_Na) with a high content of Na2O, the other (BG_Ca) with a high content of CaO, were fully characterized and sintering tests were performed to define the most interesting firing cycles. The sintered samples, treated at 880°C and 800°C respectively, were investigated from a microstructural point of view and their mechanical properties were compared to those of the bulk (not sintered) glass counterparts. The effect of sintering was especially striking on the BG_Ca material, whose Vickers hardness increased from 598.9 ± 46.7 HV to 1053.4 ± 35.0 HV. The in vitro tests confirmed the ability of the glasses, both in bulk and sintered form, of generating a hydroxyapatite surface layer when immersed in a simulated body fluid. More accurate biological tests performed on the sintered glasses proved the high bioactivity of the CaO-rich composition even after a heat treatment.
authors: Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Via Vignolese 905, 41125 Modena, Italy. antonella.sola@unimore.it.
authors: A
authors: A
authors: Sola
authors: D
authors: D
authors: Bellucci
authors: M G
authors: MG
authors: Raucci
authors: S
authors: S
authors: Zeppetelli
authors: L
authors: L
authors: Ambrosio
authors: V
authors: V
authors: Cannillo
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001672:Biocompatible Materials / Q000494:pharmacology; D001826:Body Fluids / Q000737:chemistry; D002460:Cell Line; D002516:Ceramics / Q000737:chemistry; D004055:Differential Thermal Analysis; D017886:Durapatite / Q000737:chemistry; D005898:Glass / Q000737:chemistry*; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D058428:Silica Gel / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; C425330:bioactive glass 45S5; C120461:sodium oxide-calcium oxide-silicon dioxide-diphosphorus pentoxide; D058428:Silica Gel; D017886:Durapatite; D000469:Alkaline Phosphatase