Fluoride prevents caries among adults of all ages

Medline, Embase and the Cochrane Central Register of Controlled Trials were searched. References of each retrieved article were also searched for relevant articles. The US Food and Drug Administration, American Dental Association and manufacturers of topical fluoride products were contacted to identify unpublished trials.

For inclusion, the study had to be published in the English language, was of duration 1 year or longer, and examined the association between fluoride and caries in intact human teeth in study populations that included adults. To examine the effectiveness of self- or clinically applied fluoride, only longitudinal studies with random assignment of participants or of split-mouth design were included. For studies examining the effectiveness of water fluoridation, cross-sectional studies were included if their participants lived most of their lives in a fluoridated or a nonfluoridated community.

Screening of eligible studies and data extraction were conducted independently and in duplicate. A random-effects model was used to estimate the effect-size of fluoride (absolute difference in annual caries increment or relative risk ratio) for all adults aged 20+ years and for adults aged over 40 years. Root caries increment was also estimated for adults aged over 40 years.

Twenty studies involving 13 551 participants were included in the final body of evidence. Eleven studies examined the effectiveness of self- or clinically applied fluoride. Of these studies, 10 were randomised controlled trials, and one was a controlled trial (split-mouth) that did not specify whether the treatment had been randomly assigned. Nine studies examined the effectiveness of water fluoridation; all were cross-sectioned studies except one which was a prospective cohort trial. Of the studies published after or during 1980, any fluoride (self- and clinically applied or water fluoridation) annually averted 0.29 [95% confidence intervals (CI), 0.16-0.42] carious coronal and 0.22 (95% CI, 0.08-0.37) carious root surfaces. The prevented fraction for water fluoridation was 27.2% (95% CI, 19.4-34.3%).

These findings suggest that fluoride is effective in preventing caries in adults of all ages.