Effect of sodium fluorosilicate on the properties of Portland cement

Mineral trioxide aggregate (MTA) satisfies most of the ideal properties of a surgical root-end filling and perforation repair material. It has been found to be nontoxic, noncarcinogenic, nongenotoxic, biocompatible, insoluble in tissue fluids, and dimensionally stable and promotes cementogenesis. The major disadvantages are its long setting time and difficult handling characteristics during placement when performing endodontic procedures. MTA is similar to Portland cement (PC) in both composition and properties. The cement industry has used many additives to decrease the setting time of PC. Proprietary formulas of PC additives include fluorosilicates, which decrease setting time. The purpose of this pilot study was to determine whether sodium fluorosilicate (SF) could be used to decrease the setting time without adversely affecting the compressive strength of PC.

To determine the most appropriate amount of SF to add to PC to decrease its setting time, 1%, 2%, 3%, 4%, 5%, 10%, and 15% SF by weight were added to PC and compared with PC without SF. Setting times were measured by using a Gilmore needle, and compressive strengths were determined by using a materials testing system at 24 hours and 21 days.

Statistical analysis was performed by using one-way analysis of variance with post hoc Games-Howell test. None of the percentages of SF were effective in changing the setting time of PC (P > .05), and the SF additives were found to decrease the compressive strength of PC (P < .001).

On the basis of the conditions of this study, SF should not be used to decrease setting time and increase the compressive strength of PC and as such does not warrant further testing with MTA.