High-temperature X-ray analysis of phase evolution in Sr-doped zinc-silicate glasses

Bone grafts are required in many clinical situations. Autografts are the traditional gold standard for treating conditions requiring bone grafts. However autografts have inherent drawbacks such as donor site morbidity, pain and increased operative time. An alternative for autografts are synthetic grafts. A series of strontium doped zinc silicate glasses were developed which were investigated using high temperature X-ray diffraction (HT-XRD) in order to establish phase transformations, which occur up to the first crystallization temperature, (Tp1), thus identifying the composition–structure relationships which arise during this thermal processing. In analysing BT110 it was observed that all glass material crystallised into 4 phases including strontium zinc silicate, sodium calcium silicate, calcium silicate and strontium silicate, leaving no residual glass phase. BT111 and BT112 were shown to contain a residual glassy phase alongside for BT111, sodium zinc silicate, larnite and silicon oxide and for BT112 strontium silicate, calcium silicate, sodium silicate and silicon oxide. In the case of BT111 the residual glass phase appears to be rich in strontium. The residual glass phase being Sr enriched with respect to the glass-ceramic may offer increased release of Sr2+ from the material; important for the regulation of osteoblastic and osteoclastic activity. BT113 crystallized to form strontium silicate, sodium silicate, and strontium zinc silicate. BT114 crystallized to form strontium silicate and sodium silicate. The biocompatibility of phases formed in BT113 and BT114 is as yet unknown. Further knowledge will be generated by later work examining the biocompatibility of these phases identified in this research. However, on the basis of these results, the materials (BT110–BT112) exhibit potential as a bone graft substitutes, whilst BT113–BT114 give rise to phases with unknown biocompatibility and so warrant further investigation.

Research highlights
► Sr-doped zinc silicate materials comprise of biocompatible crystalline materials.
► Appear to demonstrate a residual glassy phase at Tp1.
► Potential for exerting a marked influence on chemical stability.