Bioactivity and Biocompatibility of Lithium Contained Surface Pre-reacted Glass Fillers

Objectives: Surface pre-reacted glass (S-PRG) fillers have comprehensively been studied because they can release different ions that control the behavior of cells. We reported that S-PRG fillers containing lithium ions could induce tertiary dentin formation via canonical pathway activation in rat pulp capping model showing biocompatibility to the dental pulp stem cells. In this study, in vitro bioactivity, biocompatibility to the tissues and their biosafety have been assessed.
Methods: In vitro bioactivity test was performed using disks of MTA, S-PRG and S-PRG/Li-100 mM. Disks were immersed in simulated body fluid for 1 and 7days. Hydroxyapatite formation was assessed using scanning electron microscope.
Animal studies were conducted under the approval of the Institutional Animal Care and Use Committee of Osaka University Graduate School of Dentistry (No. 28-013-0). In vivo biocompatibility has been examined using tube subcutaneous implantation method. Teflon tubes filled with (MTA, S-PRG, SPRG/LiCl-100mM and empty) were implanted on the dorsal sites of 5 rats. One and two weeks later, tissues contained tubes have been evaluated using H/E staining. Images were taken for inflammatory cells scoring. (ANOVA, Tukey Kramer post hoc test, α=0.05). Serum lithium concentration was measured in 3 rats after pulp capping using S-PRG/LiCl-100 mM cement for biosafety assessment. 24hrs later, 5ml of blood has been collected for flame atomic absorption spectroscopy of lithium ions.
Results: The results revealed that hydroxyapatite has formed on the surface of three test groups indicating their bioactivity. MTA showed sharp edged geometrics, while other groups showed rounded heads that coalesced to form bigger apatite. Histopathological results denoted mild inflammatory reactions in all test groups with no significant difference compared with control (empty) group (p-value >0.05). Lithium ions in rat’s serum was detected less than 0.01 mmol/L.
Conclusions: S-PRG/LiCl-100 mM accelerated the bioactivity in vitro and displayed compatibility to the subcutaneous tissues. Serum lithium indicates its biosafety.