Effect of fluoride varnish and gel on dental erosion in primary and permanent teeth.

OBJECTIVE: To assess the effect of a fluoride varnish and gel on the erosive wear of primary and permanent teeth.

DESIGN: Sixty human primary (n=30) and permanent (n=30) enamel specimens were randomly assigned to one of the following groups: APF gel (1.23% F), NaF varnish (2.26% F), and control (no treatment). Fluoride gel was applied for 4 min and fluoride varnish for 24 h. Six daily demineralisation-remineralization cycles of 5 min of immersion in a cola drink (pH 2.3) and 30 min in artificial saliva were conducted during 7 days. All specimens were stored in artificial saliva between and after cycles. Surface Knoop microhardness (%SMHC) readings were performed at baseline, 48 h and 7 days. Data were tested using ANOVA and Tukey's tests (p<0.05).

RESULTS: For primary enamel, the mean %SMHC (+/-SD) after 48 h and 7 days was, respectively: gel (31.0+/-14.4 and 36.9+/-7.5), varnish (26.7+/-9.5 and 38.3+/-8.7), and control (35.8+/-8.6 and 45.0+/-8.6). For permanent enamel, such values were: gel (37.5+/-7.7 and 27.8+/-7.5), varnish (31.7+/-9.6 and 27.4+/-11.1) and control (48.6+/-6.4 and 43.1+/-6.4). In primary enamel, erosion inhibition by fluoride was not significant at 48 h (p=0.203) and 7 days (p=0.082). In permanent specimens, both products showed a significant effect (p<0.001).

CONCLUSIONS: Both fluoride varnish and gel were able to inhibit erosive enamel loss but mainly in the permanent experimental groups. Primary and permanent enamel substrates reacted differently to both demineralization by a cola drink and remineralization by fluoridated compounds.