Use of strontium doping glass-ceramic material for bone regeneration in critical defect: In vitro and in vivo analyses

The in vitro bioactivity and in vivo bone neoformation in critical-size bone defects of a glass-ceramic material containing strontium ions (Sr2+) were evaluated in the present study as well as the antimicrobial effect against oral pathogens. A glass-ceramic bioactive material in powder (CP), based on the composition of S53P4 bioactive glass, was produced by partially replacing calcium with SrO using the sol-gel route. The amount of SrO added was 2.2 wt% (CPSr12.5) and 5.0 wt% (CPSr25). The amount of Sr2+ ions released by the CP increase with time achieving 18 mg/L at 6 h and the release rate decreased at longer times. pH values higher than 10 were obtained in the first 6 h, in agreement with an inhibitory microbial effect. These materials showed in vitro bioactivity, with total surface coated by hydroxyapatite (HA) after 7 days of immersion in simulated body fluid (SBF). The pH of SBF increased rapidly after immersion of CP, reaching a maximum value of 8.72 after 168 h. HA formation was observed in vitro for all samples. On microtomography and histomorphometric analysis, CPSr25 showed higher values than CP without Sr2+ (CPSr0) for bone volume (p = 0.016), density (p = 0.016) and neoformation area (p = 0.025) at 28 days. Histological analysis revealed higher degree of vascularization after 28 days for CPSr25 when compared to CPSr0 (p = 0.003). In addition, CP showed an inhibitory effect on oral pathogens. Substitution of CaO by SrO (CPSr25) presented the best results on the healing of critical-size bone defects, as evidenced by microtomographic and histological analyses. These data confirmed that higher concentrations of Sr(2+)doped CP materials are potential alternatives to improve bone healing and regeneration in critical-size bone defects.