Effect of APF gel on a glass ionomer cement: an SEM study

This SEM study evaluated the micromorphological effect of a 1.23 percent acidulated phosphate fluoridated gel (Oral B)(APF) on the surface of a glass ionomer cement (Ketac-Fil). Glass ionomer (GI) cylinders (area 6.69 mm) were prepared and divided into seven groups of ten specimens each: Group 1, glaze, no polishing; Group 2, glaze, polishing, glaze; Group 3, glaze, no polishing, APF for four minutes; Group 4, glaze, polish, glaze, APF for four minutes; Group 5, no glaze, no polish, APF for four minutes; Group 6, no glaze, polish, APF for four minutes; Group 7, glaze, polish, two coats of glaze, APF for four minutes. The glass ionomer was handled according to manufacturer's instructions, except for groups 5 and 6, where no glaze was used. Polishing was done with medium Sof-Lex discs, using slow-speed and water. The glaze resin (Ketac-Glaze) was painted with a brush over the GI surface and cured with visible light (Demetron) for thirty seconds. In Group 7, the first coat was cured and then the second coat was applied. The APF was applied with a cotton applicator for four minutes, rinsed, and dried. All specimens were then mounted on aluminum stubs, coated, and evaluated under the SEM. The results indicated that the glaze tends to contract or incorporate into the GI matrix in all groups. When APF was used over the GI, the amount of glaze remaining over the surface was diminished, exposing the GI surface. When two coats of the glaze were used, minimal GI surface was exposed after APF treatment.