Manipulation effects on fluoride release from chemically-cured and resin-modified glass ionomers

To examine the effect of mixing techniques (hand-mixing vs. trituration) on fluoride release from chemically-cured (Fuji II) and resin-modified (Fuji II LC) glass ionomer products.

Fluoride measurements were determined and comparisons made between hand-mixed-type materials that were both hand-mixed (60 seconds) and triturated (10 seconds). Hand-mixed specimens were made using the manufacturer's recommended powder/liquid ratio. Triturated specimens of the same material were made using the same powder/liquid ratio. Disk specimens (8.5 mm diameter, 2 mm thickness; n = 6) were stored in deionized water for 23 hours to obtain Day 1 solutions. Solutions were also obtained at 2, 3, 4, 5, 6, 7, 14, 21, and 28 days after fabrication and were changed 24 hours before fluoride concentration was determined using a fluoride ion selective electrode. Daily rates of fluoride release and 28-day cumulative fluoride totals were calculated. Cumulative data were analyzed by two-way ANOVA and Scheffé's test (alpha = 0.05). Daily results were analyzed by the Mann-Whitney U-test.

A significant difference was observed between materials (P < 0.001). Depending on the kind of material used, the method of manipulation affected the fluoride release. Data analysis revealed that: (1) Fuji II LC released significantly more fluoride than Fuji II for both triturated (P = 0.005) and hand-mixed (P < 0.005); (2) the triturated Fuji II released significantly more fluoride than the hand-mixed (P = 0.02); and (3) the hand-mixed Fuji II LC released more fluoride than the triturated, but was not statistically significant (P = 0.16).