Novel Bioactive Glass Cements For Bone Grafting: From An In-Vitro To An In-Vivo Study

Objectives: An ovine study has previously been conducted to assess the performance of novel bioactive glass based calcium-phosphate cements and indicated that are osteoconductive and able to osseointegrate with host bone (bone to graft contact: 90%).
In this study we developed new strontium (Sr) containing compositions. Cement properties, bone cells activity were investigated. The addition of Sr is hypothesised to enhance bone remodelling in-vivo.
Methods: Glasses were synthesised by progressively substituting Sr²⁺ for Ca²⁺ on a molar basis. Cements were prepared by mixing the glass powders with Ca(H₂PO₄)₂ and a 2.5% Na₂HPO₄ solution. XRD, compressive strength and ions release were measured after 1h, 1d, 7d and 28d immersion in TRIS buffer solution. Setting times and Radiopacity were tested. Cell culture was performed using MC3T3-E1 osteoblast cell line. A pilot minipig study was conducted to compare performances of Sr free against 25%-Sr containing compositions for socket preservation and guided bone regeneration around dental implants. Specimens were retrieved after 3 and 6 months and analysis using XMT, BSSEM and Histology has been carried out.
Results: Sr release and radiopacity increased proportionally with Sr content in the glass. Compressive strength showed a maximum value of 12.5 MPa. XRD showed that octacalciumphosphate was the main phase present after 1h and 1d and after 28d was completely transformed to Sr-containing HA (SrHA). In general, fewer cells grew on the surface of 0%-Sr discs when compared to those with higher content.
Preliminary in vivo results suggests high osseintegration rates (90%) and high remodelling rates for the Sr-containing cement after 6 months of implantation (>50%).
Conclusions: A novel method to develop a bone substitute forming in vitro SrHA as a final product by using a bioactive glass as a precursor was shown. A correlation cements properties and Sr content was witnessed. The addition of Sr might promote a faster bone remodelling in-vivo.