Strontium-substituted bioglass-based composite for restoring root surface defects

Introduction
The interaction of soft tissues with resin-based restorations is not well understood. Understanding such interplay is essential when restoring root surface lesions close to the gingiva as it can impact the clinical outcome. This study examined cellular interactions with a novel resin-based material and compared these with contemporary materials.

Materials and methods
Resin-modified glass ionomer (RMGI) (Fuji II), resin composites (G-aenial/Bioactiva) and a novel strontium-substituted bioglass (Sr-BG) filled resin were assessed. A range of bulk and leachate characterisations were performed and oral keratinocyte attachment to these materials determined. The effect of leachates on cell attachment to culture wells were also investigated. Viable H400 cell attachment to fresh (non-immersed) and aged specimens (immersed in culture media for 7 days with media changed every 48 h) were determined quantitatively with the trypan-blue assay and qualitatively using scanning electron microscopy (SEM).

Results
Although all the materials were resin-based, there were differences in the type of resin and filler constitution which affected the leaching profile and resulted in differences in cellular attachment. Significantly more cells attached to fresh/aged Sr-prototype with more spreading and increased cell-cell contacts. Spearman’s correlation revealed positive-associations between cells attached to materials and pH as well as Si⁴⁺ and Sr²⁺ ion release. Cells exposed to Sr-prototype leachates showed significantly higher attachment. Cell attachment to wells showed negative correlations with both leachate concentration and Al³⁺ ion release.

Conclusion
The Sr-prototype composite showed promising potential for management of root surface lesions as it promoted cellular attachment which may offer a mechanism to regain the gingival seal around restored teeth.