Effect of Protective Coating on Fluoride Release from Glass Ionomer

Objective: To investigate the rate of fluoride release from three conventional glass ionomer cements (GIC) and two resin modified glass ionomer cements (RMGIC) over several progressive time intervals with and without resin coating.

Method: 120 acrylic wafers (20 in each group) with circular wells (0.3175cm diameter x 0.3175cm depth = surface area of 0.07917 cm², volume of 0.02514 cm³) were filled with GIC: Ketac Silver (3M ESPE), Fuji IX GP (GC America), Riva Self Cure (SDI) and RMGIC: Ketac Nano (3M ESPE), and Fuji II LC (GC America).  After setting, half of each sample group was coated with Ketac Glaze (3M ESPE) or G-Coat Plus (GC America).  The control group was 10 empty acrylic wells.  All samples were stored in closed containers with deionized water.  A Fluoride Ion Selective Electrode was used to measure the Fluoride release after 3 hours, 12 hours, 1 week, 2 weeks, 3 weeks, and 4 weeks.  The data was calculated as micro-grams Fluoride release per surface area (cm²). Findings were analyzed using ANOVA and Tukey tests.

Result: All samples released fluoride, with the greatest rate of release during an initial “fluoride burst” which occurred during the first three hours after setting as per manufacturer specifications. The rate of fluoride release subsequently declined, with the lowest fluoride release detected at four weeks post curing. GIC had significantly higher rates and overall amount of fluoride release compared to RMGIC. Application of resin coating caused significant impairment of fluoride release regardless of cement type. A low level of fluoride release was still detected by all the coated samples within the first two weeks despite the impairment.

Conclusion: The amount of fluoride release is dependent on type of GIC or RMGIC, presence of coating and time. Resin coating significantly decreases fluoride release, regardless of cement type or coating type.