Ion Release and Acid Buffering Capacity of S-PRG Containing Cement

Objectives: To assess evolution of the ion release and the acid buffering capacity of a S-PRG filler containing cement for root caries.
Methods: From mixture of fluoroaluminosilicate glass and S-PRG filler (Shofu), powders with different S-PRG filler content (S-PRG0, 10, 20, 30, 40 wt%) were prepared. The liquid was composed of polycarboxylate sodium polymer, water and additives. The powder/liquid ratio was 2.2/1.0 in weight. Disk shaped specimens (15-mm diameter and 3.0-mm thickness) were prepared and kept at 37°C in 100% humidity for 24 hrs. For the ion release, specimens were immersed in 20 ml of ultrapure water for 7 days (n=5 per group). From the elute, F^- was measured using an ion meter (ORION 4STAR, Thermo) equipped with a fluoride ion electrode (9609 BNWP), whereas Al, B, Na, Sr were measured using an inductively coupled plasma (ICP, SPECTRO ARCOS, HITACHI). These measurements were conducted every 24 hrs during storage. Data after 7 days water storage were statistically compared using one-way ANOVA followed by Tukey post hoc test or Kruskal-Wallis test (α=0.05). Regarding the acid buffering capacity assessment, specimens were kept in 5 ml of demineralized solution (pH 4.5) for 7 days. The pH change of the demineralized solution was monitored using a pH meter (F-52, HORIBA) every 24 hrs. Data were statistically compared using non linear regression analysis (α=0.05).
Results: Longer storage resulted in decreased ion release for all ions. S-PRG0% and S-PRG40% were the significantly highest for F^-release. S-PRG0% was the significantly highest for Al release, whereas S-PRG40% was the statistically significantly highest for B, Na and Sr release. With regard to the acid buffering capacity, S-PRG40% showed statistically significantly higher pH as compared to the other S-PRG contents.
Conclusions: In summary, S-PRG40% would be the best composition in terms of ion release and acid buffering capacity.