Molecular Basis for Action of Bioactive Glasses as Bone Graft Substitute

Abstract

Bone grafting procedures are undergoing a major shift from autologous and allogeneic bone grafts to synthetic bone graft substitutes. Bioactive glasses are a group of synthetic silica-based bioactive materials with bone bonding properties first discovered by Larry Hench. They have several unique properties compared with other synthetic bioresorbable bioactive ceramics, such as calcium phosphates, hydroxyapatite (HA) and tricalcium phosphate (TCP). Bioactive glasses have different rates of bioactivity and resorption rates depending on their chemical compositions. The critical feature for the rate of bioactivity is a SiO 2 content <60% in weight. In vivo, the material is highly osteoconductive and it seems to promote the growth of new bone on its surface. In a recent study, the activity of the material was found even to overshadow the effect of BMP-2 gene therapy. In vivo, there is a dynamic balance between intramedullary bone formation and bioactive glass resorption. Recent studies of molecular biology have shown that bioactive glass induces a high local turnover of bone formation and resorption. Many osteoporotic fracture patients are candidates for concurrent treatment with bisphosphonates and bioceramic bone graft substitutes. Since osteopromotive silicabased bioactive glasses induce accelerated local bone turnover, adjunct antiresorptive agents may affect the process. However, a recent study showed that an adjunct antiresorptive therapy (zoledronic acid) is even beneficial for bone incorporation of bioactive glass. Based on these observations, bioactive glasses are a promising group of unique biomaterials to act as bone graft substitutes.

Evaluation of optical density of bone defects filled with calcium phosphate cement and bioactive glass in rats

“…The values observed at day 7 suggest that the mere presence of particles of these products filling the cavities already yields higher density values in relation to the natural process of bone regeneration, as reported by Välimäki et al 6 and Sanzana et al 7 This phenomenon demonstrates the important role that the biomaterials studied play as scaffolds for bone healing and new bone formation, since they are replaced with bone tissue over time, through a phenomenon known as osteotransduction 8 . At the same time, they promote faster bone regeneration due to their osteoconductive and osteoinductive properties 3 , through which the biomaterials seemed to induce the process of bone repair and new bone formation earlier than in the control group.…”

Enhancement of the osseointegration of a polyethylene terephthalate artificial ligament graft in a bone tunnel using 58S bioglass

“…They suggested that the bioactive glass coating on the polymeric substrate participates in bone healing through indirect processes which promote angiogenesis and bone maturation and not directly on osteoprogenitor differentiation and bone formation. As previously reported [21], bioglass releases ions, such as Ca 2+ and Si 4+ , after implantation in vivo, which stimulate osteoblastic proliferation and differentiation. Thus, we hypothesise that the ions released from the bioglass in vivo might play an important role in new bone formation at the graft-bone interface.…”

Bioactive glass-containing cranial implants: an overview

“…In many of the FRC material studies, there have been additional BG (S53P4) particles on the surface of the FRC implant [24,25,62,63]. BGs are synthetic resorbable, biocompatible, osteoconductive-osteoinductive bone substitutes, and some compositions of BGs have clinically been used because of bonebonding capacity, antibacterial and angiogenesispromoting properties [64][65][66][67][68][69]. FRC-BG implant has been tested by animal tests for cranial implant applications as well as for orthopedics and oral implantology.…”