Effect of 1- and 4-minute treatments of topical fluorides on a composite resin.

The purpose of this in vitro study was to compare the effects of a 1-min immersion and of 4-min immersions in an acidulated phosphate fluoride (1.23% APF) foam, a 1.23% APF gel, a 2.0% sodium fluoride (NaF) gel, and water on surface topography and on weight of a composite resin (APH). Forty composite resin specimens were placed into eight groups (N = 5 each). For each treatment, a group of specimens was immersed for either 1 or 4 min (four 1-min immersions). Specimens were weighed before and after each immersion. The surface topography of two scanning electron micrographs of each specimen was scored visually by two investigators. Inter-rater reliability was r = 0.75 (intraclass correlation coefficient). There were no significant differences in the mean visual scores or weight among the 1-min immersion groups. Significantly greater surface changes and weight loss of this composite resin occurred following 4-min immersions in either 1.23% APF foam or gel as compared with those immersed in either 2.0% NaF gel or water (P 0.0001; one-way ANOVA, Tukey's Studentized Range Test).