Bioactive glasses for bone tissue engineering application

Bioactive glasses are useful materials as synthetic bone graft substitutes due to their potential for osseoinduction and osseoconduction. The ability of these materials to chemically bond to bone is characterized by surface apatite formation. In this paper, the bioactivity of two bioactive glasses has been evaluated in serum supplemented cell culture medium simulating near-physiological conditions and analysed by pH measurements, ICP-ES, FT-IR and XRD. The results show how Bioglass 45S5 that is considered maximally bioactive by many other studies, failed to form apatite in such conditions, while a slightly different glass composition was able to form detectable crystalline apatite in the same conditions, indicating the effect of minor changes in chemical composition on the bioactivity of such materials. Introduction Bioceramics such as hydroxyapatite (ActifuseTM) and bioactive glass (PerioGlas®) represent synthetic alternatives to autografts and fresh cancellous bone allografts for augmentation of severely resorbed regions in the dental alveolar ridge, preservation of ridge dimensions following dental extractions and to facilitate implant placement in deficient ridges. Ambiguity exists regarding the efficacy of hydroxyapatite monoliths and scaffolds for alveolar ridge preservation [1, 2] ,particularly when placed in fresh extraction sockets. Their major disadvantage is slow rate of degradation and the life-long presence of the synthetic material within a bone defect. Placement of bioactive glassmonoliths in artificial sockets created by splitting the alveolar bone prior to definitive restorative treatment [3] and immediately following tooth extraction results incircumferential osseous tissue formation,minimal implant dehiscence, normal healing of the overlying soft tissue, absence of infection and high survival rates over long follow-up [4] . On contact with body fluids, the initialexchange of cations (Na + , Ca 2+ ) from the glass surface for cations (H + , H3O + ) in solution causesalkalinization of local pH. Hydroxyl (OH ) ions attack Si-O-Si bonds witha subsequent loss of soluble silicagroupsthat re-polymerize onto the alkali deficient glass surface, as a silica-rich layer. Surface migration of Ca 2+ and PO4 3groups and incorporation of free Ca 2+ and PO4 3from the solution allows deposition of an amorphous CaPlayer over the silica-rich layer [5] . A mixed carbonated hydroxyapatite (HCA) layer is formed by the inclusion of OH and CO3 2,which is believed to be biologically active and essential in bonding to living tissues. An interface thus established allows interaction with biological moieties such as collagen, fibronectin, plasma proteins, blood cells, fibroblasts and osteoblasts – and in due course of time a strong bonding between the biomaterial and the physiological environment is established [6] . This paper explores in vitro bioactivity of two such materials as micro-particles, in order to characterize various parameters that influence their behaviour in physiological conditions. Quick Response Code www.idjsr.com Use the QR Code scanner to access this article online in