Carbonation inhibitor by polyethylene glycol encapsulation of calcium hydroxide fine particles to improve antimicrobial and root canal penetration properties

The carbonation of calcium hydroxide (Ca(OH)(2)) is affected by humidity and a saturated atmosphere. Ca(OH)(2) from nature is easily carbonation and self-aggregates into calcium carbonate (CaCO(3)), resulting in larger particle size impairing the antimicrobial properties due to lack of penetration into the dentinal tubules and lower ion dissociation. To reduce the particle size, the wet beads milling process with distilled water as the medium is commonly used, but often results in great carbonation of the final product. Polyethylene Glycol (PEG) may inhibit the carbonation process as well as re-agglomeration. However, it requires intensive drying of the fine Ca(OH)(2) particles. As an alternative, we used ethanol as a medium in the milling process, which is easily dried and compatible with PEG as a surfactant. This study aimed to evaluate PEG 400 as a dispersing agent in ethanol medium in the beads milling process to prevent carbonation of the fine Ca(OH)(2) particles. The following groups were analysed CaP-PEG (Ca(OH)(2)-PEG) with ethanol as a medium, CaP-Eth (Ca(OH)(2) with ethanol as a medium), CaP-DW (Ca(OH)(2) with distilled water as a medium), CaPC (Ca(OH)(2)-carbonated) as the negative control and CaC (Ca(OH)(2) analytical grade) as the positive control The final particle results were characterized to evaluate the crystal structure, functional groups, and particle size. The corresponding pH and antimicrobial activity against Enterococcus faecalis were assessed at 1, 3, 7, and 14 days. The penetration ability was evaluated by Scanning Electron Microscope. The data obtained were analysed by ANOVA with a significance level of 5%. PEG was able to inhibit carbonation and stabilize pH for up to 14 days, providing increased antimicrobial activity against E. faecalis. PEG also facilitates the ability of fine Ca(OH)(2) particles to penetrate deeper into the dentine tubules by reducing particle size.