Investigating the effect of bicarbonate ion on the structure and strength of calcium silicate-based dental restorative material—Biodentine

Abstract

Investigating the effect of carbonation on the strength and structure of calcium silicate-based cement (Biodentine™) in the presence of bicarbonate ion. Cylindrical samples of Biodentine (N = 120) were prepared and cured in deionised water (DW) or bicarbonate solution (BC) for 1 and 2days and 1, 2 and 4weeks. After storage, the compressive strength of cured samples was tested using a universal testing machine, and carbonate was quantified on the surface or within the structure of samples using Raman and Fourier transform infrared spectroscopy, respectively. Levels of calcium and silicon ions and pH were measured after each storage duration, and 4-week-old samples were imaged using scanning electron microscopy. Cement's compressive strength was significantly higher after curing in BC for 2days. This was associated with significantly higher levels of carbonate on the surface of the cement but not within its structure. Levels of calcium and silicon ions and pH in BC dropped significantly after 1day and remained at a steady lower level. The pH and calcium ion levels dropped gradually over 4weeks in DW, unlike the silicon ion level that maintained a steady higher level than in BC. Our results indicate that Biodentine exhibited higher strength in the presence of bicarbonate, which can be explained by the carbonation process that encouraged the formation of calcium carbonate on the cement's surface. Carbonation should be of more consideration when studying calcium silicate-based cements, with curing and testing conditions closer to the intraoral conditions.