Introduction: Decalcification is a significant problem during fixed orthodontic treatment. Topical Fluorides can reduce or eliminate the problem, but the relative effectiveness of different treatments or combinations of topical fluoride preparations is unknown. This systematic review was undertaken to determine the effectiveness of topical fluoride preparations in preventing decalcification during fixed orthodontic treatment. Methods: A wide search of published and unpublished material in any language was undertaken by using general and specialist databases; key dental journals were searched by hand. Predefined inclusion criteria based on objective outcome measures of decalcification, duration of treatment, presence of a comparison group, and study design were applied to determine study selection. Included studies were double extracted onto predesigned data extraction sheets. Results and conclusions: By screening titles and abstracts, we identified 143 articles; after the inclusion criteria were applied, 7 reports (of 6 studies) remained. Differences in the methodologies and reporting made statistical analysis impossible. However, the use of topical fluorides in addition to fluoride toothpaste reduced the incidence of decalcification in populations with both fluoridated and nonfluoridated water supplies. Different preparations and formats appear to decrease decalcification, but there was no evidence that any 1 method was superior. There was some evidence that the potency of fluoride preparations might be important.