Novel Strontium/High Phosphate Containing Bioactive Glass for Periodontal Treatment

Objectives: Bioactive silicate glass-based Perioglas^® has been used to treat periodontal-bony-defects. During glass degradation in body fluids, these glasses generate a high pH>8. This high pH enhances the growth of periodontopathic bacteria such as P.gingivalis which grows optimally at higher pH ≈ 8.3, furthermore high alkaline pH inhibits osteoblast activity, resulting in suppression of osteogenic differentiation/proliferation of the local biological environment. Therefore, this work aims to develop novel strontium/high phosphate containing bioactive glass to program and regulate the higher alkaline pH evolution through: (i) inhibition the alkaline periodontal bacterial growth of virulent P.gingivalis and (ii) creation neutral periodontal environment for osteoconductive bone regeneration. Strontium is known to stimulate osteoblasts and has a bactericidal action against P.gingivalis, it also provides radio-opacity enabling the dissolution process to be followed clinically by X-rays.
Methods: Specific ratios of strontium and high phosphate bioactive glass were prepared by melt-quenching-process. The glasses synthesised were ground and sieved to obtain a specific selection of particle size fractions for glass preparation. The glass-bioactivity was performed by immersing the prepared glass in Tris and SBF Buffer-solutions (pH=7.35). The pH change in buffers was measured and the ions release was quantified by ICP-OES as a function of time. The glass degradation and apatite formation were investigated by Fourier Transform Infrared (FTIR) Spectroscopy, XRD (X-ray diffraction) and Magic-Angle-Spinning-Nuclear-Magnetic Resonance (MAS-NMR).

Results: The pH behaviour was modulated by immersing the prepared glass in buffers solutions (Tris and SBF). ICP-OES-study detected essential Sr²⁺ therapeutic ions release with respect to antimicrobial activity against P.gingivalis. FTIR, XRD and MAS-NMR revealed much faster glass degradation and apatite formation compared to the reference Perioglas^®.

Conclusions: Smart modulation of pH profile and therapeutic Sr²⁺ ion release were essential in inhibiting the alkaline bacterial growth (P.gingivalis). The new developed glass accelerated the apatite formation rate compared to Perioglas^®.