How different time intervals between repeated applications of CPP-ACP fluoride varnish effect smooth surface enamel demineralization?

Objectives: To evaluate the preventive effects of different time intervals between repeated applications of the CPP-ACP fluoride varnish on enamel demineralization. Methods: Human teeth were sectioned and randomly allocated to three groups: 4-week, 6-week, and 12-week (N = 22/group). Baseline images of the enamel surfaces were obtained using the FluoreCam recording the area, intensity, and impact of baseline enamel demineralization. All groups received fluoride varnish applications at the beginning of the experiment. The varnish was reapplied every 4 or 6 weeks in the 4-week and 6-week groups, respectively. Following each application, the groups underwent thermo-cycling, tooth brushing and pH cycling to simulate the time effect. After 12 weeks, the enamel surfaces were reimaged using the FluoreCam. Within and between-group differences in the area, intensity and impact of demineralization were evaluated. Results: At baseline, there were no significant between-group differences for area, intensity, or impact. Statistically significant (p<0.001) enamel demineralization occurred over time within each group. There were significant between-group differences in the changes that occurred in area (P = 0.004), impact (P = 0.022), but not intensity. The 12-week had significantly larger areas of demineralization than the 6-week (P = 0.041) and 4week (P = 0.001) groups. Changes in impact was significantly (P = 0.007) greater in the 12-week group than 4-week group, but not greater than the 6-week group. There were no statistically significant differences between 4- and 6-week groups in the changes of area, intensity, or impact. Conclusion: Reapplication of the CPP-ACP fluoride varnish every 4-6 weeks, is more effective in reducing enamel demineralization compared to every 12 weeks.