Setting time and expansion in different soaking media of experimental accelerated calcium-silicate cements and...

The setting time and the expansion in deionized water, phosphate-buffered saline (PBS), 20% fetal bovine serum (FBS)/80% PBS or hexadecane oil of experimental accelerated calcium-silicate cements and ProRoot MTA were evaluated.

Different compounds such as sodium fluoride, strontium chloride, hydroxyapatite, and tricalcium phosphate were separately added to a basic experimental calcium-silicate cement to test their effect on setting and expansion. The initial and final setting times were determined using appropriate Gilmore needles. A linear variable differential transformer (LVDT) device was used to test the restricted hygroscopic linear expansion over 180 minutes of cements immersed in different solutions. Results were statistically compared using a 2-way ANOVA test (cement type versus solution type).

All experimental cements showed initial setting times between 28 and 45 minutes and final setting times between 52 and 80 minutes. MTA showed a final setting time of 170 minutes. Final setting time of all experimental cements was faster than MTA. All cements showed slight (0.04%-0.77%) expansion in water, PBS, or FBS/PBS. Only fluoride-containing cement showed a significant expansion in water (6.68%) and in PBS (6.72%). The PBS/FBS contamination significantly reduced the expansion of fluoride-containing cement (2.98%) and MTA (0.07%). In contrast, cements showed a slight shrinkage when immersed in hexadecane, especially fluoride-containing cement.

The study demonstrated that: (1) the setting time of calcium-silicate cements may be effectively reduced; (2) the expansion is a water dependent mechanism owing to water uptake, because no expansion occurred in cements immersed in oil; (3) a correlation between setting time and expansion in water and PBS exists; (4) fluorine-containing cement showed a significant expansion in water and in PBS; (5) the immersion in FBS/PBS strongly reduced the expansion of MTA and fluoride-doped cement suggesting that fluid contamination (ie, blood) during surgical procedures may greatly affect the expansion of some calcium-silicate cements.