Buffering Capacity and Fluoride Release of GICs in Natural Saliva

Objectives: To investigate the fluoride release and buffering capacity of two glass ionomer cements (GICs) in natural stimulated saliva. Methods: Columnar specimens (2x2x24mm) were prepared from Ketac-Fil Plus Aplicap (KF, 3M/ ESPE, Germany) and Fuji IX (FU, GC, Japan). The specimens were matured for 24h at 37ºC before being lapped and placed either in acidified (pH ~ 3.80) or non-acidified (pH ~ 7.10) natural stimulated saliva. Over 4 weeks the saliva was replaced daily. The pH changes (DpH) and fluoride release were determined daily using a pH meter and ion-selective electrode (ISE). Finally, the specimens were weighted and the surfaces observed under scanning electron microscopy (SEM). Results: The materials showed a similar daily pattern for DpH and fluoride release. The DpH was increasing under acidified conditions and decreasing or increasing under non-acidified conditions. The mean cumulative fluoride release in ppm (±sd) from KF (266±11) was found to be significantly higher than FU (189±3) under acidified conditions (P< 0.05, one-way ANOVA and Tukey's test), while having no significant differences (51±7) and (46±4) under non-acidified conditions. The DpH and fluoride release showed a significant positive relation under an acidic environment and were inversely proportional under neutral conditions. Neither material showed any significant surface changes under non-acidified conditions, while KF showed significantly more surface destruction under acidified conditions. Specimens lost weight in acidic media (KF > FU, P< 0.05) and gained weight in non-acidic media (KF ~ FU). Conclusions: Acidified conditions cause greater differences in fluoride release between GICs. The DpH and fluoride release were positively related under acidic conditions and inversely proportional under non-acidic conditions.