Período de wash-out en diseños experimentales cruzados con dentífrico de alta concentración de fluoruro

Objective

Most crossover studies using fluoride dentifrice (FD) of standard concentration (1000-1500 ppm F) have empirically used a wash-out period of 7 days to remove the residual effect of the treatment. For higher concentrations of FD (5000 ppm F) the period is unknown, and a longer time may be required to remove fluoride (F) from saliva. Therefore, the aim of the study was to determine if less than 7 days of wash-out would be sufficient to remove residual F in saliva after using 5000 ppm F FD.

Methodology

An in vivo study, blind analysis, was conducted on volunteers (n = 6) who brushed their teeth 3 times per day in the following sequence: a) initial or lead-in period of 3 days using placebo fluoride dentifrice (PD) (0 ppm F); b) using a high concentration FD (5000 ppm F) for 4 days; and c) wash-out using PD for 3 days. During the 3 periods, samples of non-stimulated and stimulated saliva were collected after fasting (one overnight period from the last brushing). Fluoride concentration was assessed in saliva using a fluoride specific electrode.

Results

F concentrations in saliva after discontinued use of FD (wash-out period of 2 and 3 days) were similar to baseline values. F concentrations did not differ between unstimulated and stimulated saliva.

Conclusion

A two day wash-out period using non-fluoridated dentifrice was sufficient to eliminate residual F in saliva after use of a high concentration F dentifrice. These results are also valid for standard concentrations of dentifrice.