Etching of young permanent teeth with an acid gel.

The effect of 15 seconds of etching of young permanent teeth in vitro with a phosphoric acid gel (50 percent) was evaluated with the scanning electron microscope (SEM). Resin impressions of forty-seven pairs of contralateral enamel surfaces divided into three experimental series were studied. A scale with scores from 0 to 3 was used to evaluate the degree of surface irregularity. In the first series the effect of acid gel was compared with the effect of a phosphoric acid solution (37 percent). In the second series 15- and 60-second periods of etching with acid gel were compared. In the third series 15 seconds of acid gel etching of enamel surfaces pretreated with fluoride was compared with the effect of the same etching time on nonfluoridated enamel. It was found that there is no difference in the degree of surface irregularity after etching with an acid solution as compared with an acid gel and that it is possible to create good retentive conditions on the enamel of young permanent teeth after 15 seconds of etching. It was also concluded that extra etching time is not necessary when teeth have been pretreated with fluoride.