Correlating immediate vapour reactivity with dentin remineralization and tubule occlusion capacity of a bioactive sol-gel borate glass

The use of bioactive glass as a mineralization agent in treating dentin hypersensitivity has been established for almost two decades where the melt-quench-derived silicate glass, 45S5, may be regarded as the gold standard formulation. Compared to silicate glasses, borate glasses are less chemically durable and have the potential to mineralize (i.e., convert to apatite) more rapidly. This study compared the apatite forming capacity of a sol-gel-derived calcium-borate glass, 40CaO–60B2O3 (SGB60), to that of 45S5, on demineralized dentin discs and its ability to occlude tubules on non-demineralized dentin discs, in vitro. Moreover, it investigated the vapour sorption reactivity of the glasses to explore the potential correlation between their immediate aqueous interactions and bioactivity in remineralization solution. Compared to 45S5, SGB60 demonstrated more rapid calcium-phosphate layer formation on demineralized dentin surfaces. On the other hand, after 24 h immersion in remineralization solution, the 45S5-induced calcium-phosphate layer occlusion of tubules in non-demineralized dentin surfaces appeared to be qualitatively greater than that induced by SGB60. Moreover, vapour sorption analysis under either air or nitrogen gas, demonstrated that the reactivity of 45S5 with vapour varied under the different purge gasses, with significant carbonate formation under air. In contrast, SGB60 showed a more rapid rate of initial weight increase with vapour under both purge gasses, and this vapour reactivity may be correlated to its more rapid calcium-phosphate layer formation on demineralized dentin surfaces when immersed in remineralization solution.