Characterisation and Synthesis of a Novel Bioactive Glass Cement Endodontic Sealant

Abstract

AIM: Endodontic Sealants are critical to the long-term performance of root canal treatment. The objective of this study was the characterization of a new potential endodontic sealant based on a strontium bioactive glass cement. METHODOLOGY: A strontium bioactive glass (SiO2-P2O5-Na2O-CaO-SrO) was synthesized by a melt quench route and compared with a commercially available sealant. A strontium glass was chosen to increase the radio-opacity of the material but also provide strontium release. Strontium is known to: i) upregulate osteoblasts ii) have a bactericidal action and iii) stimulate bone formation, The glass was ground and sieved to give a glass powder <45microns which was then blended with powdered Ca(H2PO4)2 and mixed with a 2.5% solution of Na2HPO4. The resulting paste set hard to give a cement in <1Hr. Discs measuring 10mm in diameter by 1mm thick were produced. The discs were then immersed in simulated body fluid (SBF) and Tris buffer pH7.3 (TB) for 0 to 6 weeks Fourier Transform Infrared Spectroscopy ( FTIR) and X-ray powder diffraction (XRD) were used to characterize the discs. The immersed solutions were analyzed by Inductively coupled optical emission spectroscopy (ICP-OES) for Ca, Sr, Si, Na and P. RESULTS: FTIR and XRD showed the bioactive glass reacted initially forming a crystalline nastrophite (NaSrPO4·9H2O), after 1day immersion in TB or SBF the nastrophite disappeared and the presence of a strontium substituted apatite Ca/Sr5(PO4)3OH was detected. Analysis of the immersion solutions by ICP-OES showed an initial increase in P in TB up to one day followed by a decline suggesting release of phosphate from the cement followed by its consumption to form apatite. The P and Ca concentrations decreased in SBF indicating their consumption to form more apatite within the cement. Both Sr and Si were detected in biologically therapeutic amounts in both SBF and TB. CONCLUSIONS: The new sealant demonstrated bioactive properties including ion release and apatite formation. It shows potential as an endodontic sealant.